Development of Mobile App on Structural Glass Design · 4.2 The DIN 18008 52 4.3 The CAN/CGSB-12.20...

Development of Mobile App on Structural Glass Design

Author: Imre Vekov

Supervisor: Prof. Sandra Jordão and Prof. Aldina Santiago

University: University of Coimbra

University: University of Coimbra

Date: 12.01.2015

European Erasmus Mundus Master

Sustainable Constructions under natural hazards and catastrophic events 520121-1-2011-1-CZ-ERA MUNDUS-EMMC

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Acknowledgments

I would like to express my gratitude to my two supervisors, Professor Sandra Jordão and

Professor Aldina Santiago. Their continuous guidance and constructive remarks were an

invaluable help to improve this work.

I would also like to thank to Professor Luís Simões da Silva for the opportunity to work on

this topic, I am really grateful for the chance to combine the areas of structural engineering

and software development.

I would like to thank Jocelyn Reyes for her valuable advice in topics related to graphical

design.

My sincere thanks to my colleagues from the SUSCOS programme and to everyone from the

Civil Engineering Department from the University of Coimbra, who helped and supported me

whenever needed.

The author acknowledges the Ministério da Educação e da Ciência (Fundação para a Ciência

e a Tecnologia) for their support under the framework of the research

PTDC/ECM/116609/2010 – SGlass.

During the development of the thesis very valuable insights and contributions were made by

Arup, represented by Paulo Machado, and by the representatives of Cristalmax, Cruz de

Oito, Sika and Sosoares. I am very grateful for their ideas, help and their support to develop

an Android application for structural glass design.



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Abstract

Glass is one of the most favoured structural materials used by architects in an increasing

manner worldwide, to offer quality and style to their projects, and to offer a modern look.

Glass is a powerful material, with high compression strength, and an elevated resistance to

chemical abrasion, making glass one of the most durable materials.

Android handheld devices have already gathered significant importance and are a part of the

everyday life. Android applications offer fast support for countless everyday life activities,

and are widely used in the industry and various technological fields. The most common

building materials like steel and concrete already have numerous dedicated Android

applications to design structures, yet, structural glass has none.

The thesis presents the development process of an Android application that aims to help in

structural glass design. As there is no such application on the present market, the needed

functionalities were specified, developing modules to offer theoretical support, calculation

modules, and a structural glass product database for the user. The development process was

largely helped by the valuable insights that were made by Arup, represented by Paulo

Machado, and by the representatives of Cristalmax, Cruz de Oito, Sika and Sosoares.

Available data on structural glass was compiled to form the Knowledge Base, offering an

overview of the terminology, technological procedures and design codes used in structural

glass design.

Multiple structural glass design codes were studied and calculation methods were selected

for further implementation. Complex calculation blocks were designed to present solutions

and analysis possibilities to various design problems, connecting in the same time every

calculation procedure to the pre-design functionality of the Knowledge Base.

The architecture of the application was defined and every complex functionality was

transposed into an algorithmic form to make the software implementation possible. The

application user interface was defined, detailing the input and output methods, and the

general design guidelines.

The development of the application was done with Android specific development tools

under Eclipse, an integrated development environment. The Java object-oriented

programming language and Extensible Markup Language (XML) were mostly used through

the implementation process to develop the equivalent software code, and finish the process

with a running application.

Final remarks and future development possibilities were listed to contribute to an eventual

further development of the application.



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Keywords

glass, structural design, handheld application, Android, Java, product database, design

codes, price estimation, glass to steel equivalence



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Table of Contents Acknowledgments 2

Abstract 3

Keywords 4

Table of Contents 5

Symbols and abbreviations 8

1 Introduction 10

1.1 Overview/framing 10

1.2 Methodology 13

1.3 Organization and contents of the thesis 14

2 Background info: Material and technology 16

2.1 Glass 16

2.2 Technological processes 22

2.2.1 Float glass 22

2.2.2 The heat tempering process 23

2.2.3 Chemical tempering 26

2.2.4 Laminated glass 27

2.3 Glass used in structural systems 29

2.3.1 Glass beam 29

2.3.2 Glass column 32

2.3.3 Glass slabs 33

2.3.4 Glass walls 34

2.3.5 Connections in structural glass 36

3 State of the art 41

3.1 Applications for structural glass design 41

3.2 Databases 45

3.2.1 Relational Database management systems (RDBMS) 45

3.2.2 Object-oriented database management systems 46

3.3 Agile software development 47

4 Design procedures for structural glass 49

4.1 The E1300-12a 49

4.2 The DIN 18008 52

4.3 The CAN/CGSB-12.20 54

4.4 The AS 1288-2006 57



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4.5 Comparative table of the considered design codes 58

5 Architecture and development of the code 62

5.1 General overview 62

5.2 The structure of the application and the navigation possibilities 65

5.3 Input methods 72

5.3.1 The Button 72

5.3.2 The EditText 73

5.3.3 RadioButtons and RadioGroups 75

5.4 Output methods 77

5.4.1 Linear Layouts and Scrollview 79

5.4.2 The TextView 81

5.4.3 The WebView 83

5.4.4 Images and Description 83

5.4.5 Emailing the results 84

5.4.6 Description of a calculation block 85

5.5 The Knowledge Base 86

5.6 Implementation of design codes calculation procedures for glass sheets 91

5.6.1 Introduction 91

5.6.2 German DIN18008 91

5.6.3 American E1300-12a 96

5.6.4 Canadian CAN/CGBS1220 100

5.6.5 Australian AS1288-2006 102

5.7 Calculation blocks 105

5.7.1 Introduction 105

5.7.2 Design of a glass fin 105

5.7.3 Design of a glass T-beam 108

5.7.4 Design of a hybrid beam 110

5.7.5 Design of a glass balustrade 111

5.8 The Product database 112

5.9 The Glass beam equivalent functionality 117

5.10 The About subpart 120

6 Conclusions and future development 121

7 Figures-sources/credits 123

8 Reference list 126



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Symbols and abbreviations

Symbols:

a - short side of the glass sheet (Canadian CAN/CGSB-12.20)

b - long side of the glass sheet (Canadian CAN/CGSB-12.20)

c - strength coefficient (Canadian CAN/CGSB-12.20)

c1 - glass type strength coefficient (Canadian CAN/CGSB-12.20)

c1 - glass type factor (Australian AS 1288-2006)

c2 - heat treatment strength coefficient (Canadian CAN/CGSB-12.20)

c2 - surface type factor (Australian AS 1288-2006)

c3 - load duration strength coefficient (Canadian CAN/CGSB-12.20)

c3 - load duration factor (Australian AS 1288-2006)

c4 - load sharing strength coefficient (Canadian CAN/CGSB-12.20)

d - depth of beam (Australian AS 1288-2006)

D - dead load (Canadian CAN/CGSB-12.20)

E - modulus of elasticity

Ed - design value of actions (German DIN18008)

ft’ - characteristic tensile strength (Australian AS 1288-2006)

G - torsional elastic modulus (Australian AS 1288-2006)

g1 - slenderness factor (Australian AS 1288-2006)



h - glass plate thickness (Canadian CAN/CGSB-12.20)

J - torsional moment of inertia (Australian AS 1288-2006)

kc - construction factor (German DIN18008)

kmod - modification factor (German DIN18008)

ksheet - load sharing factor (Australian AS 1288-2006)

L - live load (snow) (Canadian CAN/CGSB-12.20)

Lay - distance between the effectively rigid buckling restraints / distance between points of

effective rigid rotational restraints (Australian AS 1288-2006)

Mcr - critical elastic value of the maximum moment (Australian AS 1288-2006)

p - effective uniform pressure (Canadian CAN/CGSB-12.20)

Q - live load (wind and earthquake loads) (Canadian CAN/CGSB-12.20)

r0 - factor for deflection calculation (Canadian CAN/CGSB-12.20)



R - factored resistance (Canadian CAN/CGSB-12.20)

Rd - design value of the resistance (German DIN18008)



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Rref - factored resistance of reference glass (Canadian CAN/CGSB-12.20)

Ru - nominal capacity (Australian AS 1288-2006)

S* - design action effect (Australian AS 1288-2006)

T - effects of temperature difference (Canadian CAN/CGSB-12.20)

TD - melting temperture

Tg - solidification temperature

tsheet - thickness of glass sheet (Australian AS 1288-2006)

w - deflection (Canadian CAN/CGSB-12.20)

x - factor for deflection calculation (Canadian CAN/CGSB-12.20)

X - geometric factor (Australian AS 1288-2006)

yh - location from the neutral axis of the loading point (Australian AS 1288-2006)

y0 - distance of the restraints from the neutral axis (Australian AS 1288-2006)

αD - combination factor for dead loads (Canadian CAN/CGSB-12.20)

αL - combination factor for live loads (Canadian CAN/CGSB-12.20)

αQ - combination factor for live loads (Canadian CAN/CGSB-12.20)

αT - combination factor for loads from temperature difference (Canadian CAN/CGSB-12.20)

αT - thermal expansion coefficient

γ - importance factor (Canadian CAN/CGSB-12.20)

δ - deflection

n - Poisson’s ratio

φ - capacity factor (Australian AS 1288-2006)

ψ - load combination factor (Canadian CAN/CGSB-12.20)

Abbreviations:

ASTM - American Society for Testing and Materials

CAN - Canadian

CGBS - Canadian General Standards Board

EVA - etyl vinyl acetate

LR - load resistance

LTB - lateral-torsional buckling

NFL - non-factored load

PET - polyester

PVB - polyvinyl butyral

SLS - service limit state

ULS - ultimate limit state



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1 Introduction

1.1 Overview/framing

Glass is one of the most favoured structural materials used by architects in an increasing

manner worldwide to offer quality and style to their projects. Glass is a powerful material,

with high compression strength, and an elevated resistance to chemical abrasion, making

glass one of the most durable materials. In 2010 the global float glass market produced more

than 52 million tons of float glass for different purposes. The value of these glass products is

around 22 billion euros at a primary level, jumping to 55 billion euros on the level of

secondary processing. The market tends to grow around 3 per cent every year, the demand

depending on the economic cycles. On an average calculation, float glass production

represents 0.1-0.2% of the GDP (Gross Domestic Product). The building products represent

80-85% of the overall float glass market. Four fully global companies are of large importance

and responsible for a major share of glass production, NSG Group, Saint-Gobain, Asahi and

Guardian. In the European Union 58 float lines are operational and they have a capacity of

12 million tons every year. As represented in Figure 1.1, the number of float lines used for

glass production is increasing worldwide (Savaëte, 2011).

Figure 1.1 Float lines in China, Europe and USA from 1960's to today(Savaëte, 2011)

The main glass producers from the EU are Germany with a share of 19%, France, Italy and

Belgium with 12% each and UK and Spain with 9% each1.

In the last years a trend of desire for transparency can be observed in building design.

Elements made of glass combine the impression of modern design, functionality and design

freedom to obtain a final product that can be mostly characterized as being elegant and

functional.

1 http://www.glassforeurope.com/en/industry



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Global companies and major institutes join in on the trend and by various glass structures try

to send the positive messages of transparency, versatility and quality. As glass structures

tend to be the symbol of technological innovation, they are sometimes used to demonstrate

corporate advancement and the pursuit of continuous improvement (Figure 1.2).

Figure 1.2 Kanagawa Institute of Technology, Japan

Steve Jobs, the former CEO of Apple can be considered as such an example. His talent and

contribution to technology and art are well renown, having among others, multiple

structural glass design patents under his name, choosing glass as structural material for his

stores and also for the new headquarter building of Apple. The Apple store entrance in New

York shown in Figure 1.3 is an example of dedication and fast technological and

advancement in the quality of glass design. It was first constructed using 90 glass panels. The

number decreased to 15 after a major renovation granting a cleaner look and demonstrating

fast advancement of glass as a structural material. Also, Apple was the first major company

using glass staircases in their product stores, going as far as to own the patent rights for it

(Figure 1.4).



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Figure 1.3 Apple store entrance in New York

Structural engineering, architects visions and company pride mix together to predict a future

where structural glass will grow in magnitude and the design of glass elements will gather

larger and larger importance.

Figure 1.4 Apple's first spiral glass stairway, Osaka, Japan

The resources of the computers and other calculation enhancing electronic devices are

largely used in the fields of structural engineering. In these applications the design

procedures from the engineering field are combined with the computational possibilities

offered by an electronic device. Such examples are the applications that are developed for

smartphones.



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Smartphones are phones with advanced computing capabilities that mix together properties

of computers and other commonly used electronic devices like cameras, sound recorders,

media players etc.

As smartphones and other devices (tablets etc.) with similar characteristics are widely used,

it is advisable for design software to orient the application development towards these

technologies. Most of these mobile devices use the Android operating system, which is an

open source platform and is widely used in electronic devices.

There is a need for a mobile application developed for Android environment that can tackle

issues related to structural glass, as in the present there is no application related to

structural glass on the market, in the application stores.

1.2 Methodology

The methodology to develop a handheld device application consists of mainly 3 major parts.

As a first step, considered as pre-development, the analysis and formulation of the

application specifics takes place to prepare the data and desired functionalities for

software implementation.

As a second step, the graphical design process takes place, defining the interface of

the application.

As a third and last step, the implementation is done for specific platforms.

In commercial software development these main steps are undertook by different

development/design teams to optimize the workflow, ensure superior quality and minimize

the time needed to complete the project. Using this design methodology, the steps of

development overlap and run in parallel, and a continuous communication ensures the

synergy of the project. In the application treated in the present work, the mentioned steps

were carried out by only one person, the workflow being linear.

The pre-development phase consisted of data gathering and analysis. An overview of the

present theoretical knowledge related to structural glass was summarized to offer a

framework and support to the calculation steps. Most of this data was used further to

compile a Knowledge Base with useful information related to structural glass.

In the second step, different technological aspects were collected, together with an

overview of major structural glass design code summary. Multiple structural glass design

codes were studied and compared. The different glass sheet calculation processes and glass

member calculation procedures were studied and summarized to define the steps used in

the calculation blocks.

An overview study of the present structural glass market was done, to assemble a database

that represents the cross-section of the glass market for materials used in the present in

structural glass constructions.



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The graphical design consisted mainly of the detailed definition of the input and output

methods used in the application. The graphical interface design was treated as a secondary

objective, as the other two steps offer design topics that are more valuable to tackle from an

engineering point of view, taking also into consideration that the graphical design is the part

that can be updated in the application the most easily.

Graphical representations were attached to the calculation blocks to offer a visual

representation. Throughout the application the design principles were implemented to offer

a uniform appearance to the application, consisting of the use of titles, general

representation, button use, etc..

The implementation of the application was done for Android environment using the Eclipse

development tool. An overview of the basic Android functionalities was provided and the

implementation steps are detailed both for Java and for the xml format. The complex

functionalities were taken apart into pieces, to form algorithms that are implementable for a

software language. The syntax is shown for the general cases, and screenshots are provided

from the application to offer a thorough overview.

1.3 Organization and contents of the thesis

The dissertation is divided into 6 chapters. A short description is provided for the contents of

each:

Chapter 1 Introduction

This chapter is an introduction to the work presented in this dissertation. The main goals and

influencing factors of the work are described.

Chapter 2 Background information

This chapter presents the basic background information related to glass as material and the

related technologies.

Chapter 3 State-of-the-art in glass design and Android application development

This chapter reviews the state of the art in Android application development.

Chapter 4 Design procedures for structural glass

This chapter presents an overview of some of the various design codes used in structural

glass design and various design procedures are selected.

Chapter 5 Structural glass-application implementation

This chapter presents the steps of the development of an Android application, which aims to

aid structural glass design, focusing on the algorithmic formulation and the implementation.



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Chapter 6 Final remarks and future development

The chapter presents the conclusions of the development work, and lists the future

improvement possibilities of the application.



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2 Background info: Material and technology

2.1 Glass

“Glass is a uniform material, a liquid that has solidified by cooling to a rigid state without

crystallizing, which means that the molecules are in a completely random order and hence do

not form a crystal lattice. It is a solid with an amorphous, noncrystalline structure.”

(Khorasani, 2004)

Figure 2.1 Glass sheets commonly used in construction industry

Glass has a very high resistance to chemical substances making it one of the most durable

construction materials. In the construction industry, for structural or nonstructural purposes

mostly soda lime glass is used. Glass is composed from silica sand, lime, soda and further

additives (Table 2-1). The soda (sodium oxide) has the role to lower the temperature

necessary for the procedure while the lime acts as a stabilizer and increases the chemical

resistance (Haldimann, et al., 2008).

Table 2-1 Typical composition of soda–lime–silica glass

Material Formula % composition

Silica SiO2 69-74%

Lime CaO 5-14%

Soda Na2O 10-16%

Magnesia MgO 0-6%

Alumina Al2O3 0-3%



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Figure 2.2 Schematic view of the irregular view of soda lime silica glass(Haldimann, et al., 2008)

In the case of glass there is no exact melting point. When exposed to heat a gradual change

from solid to plastic-viscous form and then to liquid form can be observed through a

temperature range (Figure 2.3). The exact melting temperature (Ts) and solidification

temperature (Tg) depend on the chemical composition, and so does the viscosity and the

thermal expansion coefficient. For soda lime silica glass the values are around 1300-1600C

for the melting temperature and 530C for the transition temperature (Haldimann, et al.,

2008).

Figure 2.3 Schematic comparison of the volume’s dependence on temperature for a glass and a crystalline

material(Haldimann, et al., 2008)

One interesting characteristic of glass is that it can be produced almost transparent. The

electrons in glass are confined to specific energy levels and thus they don’t absorb the

radiation in the bandwidths visible (Figure 2.4). Only a small part of the light is reflected

from the surface and another small part is absorbed by the impurities in glass. Optical

properties are mainly influenced by the chemical composition, the thickness of the glass

sheet and the applied coatings (Wurm, 2007).



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Figure 2.4 Transmittance as a function of wavelength for a typical soda lime silica glass and a low-iron glass with anti-

reflective coating(Haldimann, et al., 2008)

Glass has an isotropic behavior, its properties are independent from the direction or

orientation. As it can be seen in Figure 2.5, glass presents an almost perfectly elastic

behavior until it reaches its load bearing capacity, where it suddenly fractures in a brittle way

(O'Reagan, 2014).

Figure 2.5 Stress/strain curves for steel and float glass(O'Reagan, 2014)

Based on the molecular bonding forces between the elements, the tensile strength of glass

can be as high as 32 GPa. This ideal strength is never achieved because of the surface flaws

(microscopic and macroscopic) that define the actual tensile strength. The flaws in the glass

surface can be caused by factors like the manufacturing processes, mechanical processes

and environmental factors. When the glass element is under compression there is no flaw

opening on the surface, therefore a higher resistance is achieved. Although this higher

resistance under compression, the determining factor for the structural applications



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regarding the resistance of glass will remain the tensile strength because in most of the

cases a glass element reaches its tensile strength before its compressive strength.

On the surface of the glass element there are several larger flaws, but the number and the

severity of these flaws gets smaller when descending to the level of glass fibers. Because of

these microscopic flaws in the bulk material, the fracture stresses decrease as the fiber

diameter increases (Figure 2.6) (Haldimann, et al., 2008).

Figure 2.6 Typical short term strengths as a function of the flaw depth(Haldimann, et al., 2008)

A glass element fails in tension if the stress intensity at the tip of one flaw exceeds a critical

value. Other influencing factors for the tensile strength are the duration of loading and the

surrounding environment, as humidity accelerates subcritical crack propagation through

stress corrosion (Figure 2.7).

The term stress corrosion or static fatigue is used for the chemical phenomenon that causes

flaws to grow in the presence of humidity when exposed to flaw opening stresses. The glass

can fail in time while not being exposed to the initially determined failure stress, as the

strength of the glass decreases with time because of the phenomenon (Khorasani, 2004).

Figure 2.7 Crack growth by chemical breaking of oxide network (Khorasani, 2004)



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Depending on the local stress and the curvature of the crack tip enough activation energy is

gained to supply the chemical reaction shown in Figure 2.8 of a water molecule with silica at

the crack tip. The H2O molecule will generate two Si-OH units.

Figure 2.8 Stress corrosion, chemical reaction at the crack tip: (1) adsorption of water to Si-O bond, (2) concerted reaction

involving simultaneous proton and electron transfer, and (3) formation of surface hydroxyl groups(Haldimann, et al.,

2008)

These reaction products are weaker than original glass and the cracks lengthen with one

atomic-scale step. Figure 2.9 illustrates the effect of water vapor on crack lengthening in

glass at room temperature.

Figure 2.9 Crack velocity versus load(Khorasani, 2004)

This subcritical crack growth is the consequence of stress corrosion and underlines the fact

that the general failure of glass is heavily influenced by the surface flaws.



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Mainly because of the above mentioned characteristics glass design has a slightly different

approach when compared to other commonly used materials as steel or concrete. As glass

can’t yield, the overall resistance checks are far from enough. It is important to not permit

any stress concentrations and to limit the stress range at areas prone to failure by stress

concentrations like supports and connections (O'Reagan, 2014).



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2.2 Technological processes

2.2.1 Float glass

The float glass process developed by Alistair Pilkington is the most commonly used glass

fabrication method producing 90% of the world’s glass production. The production process,

shown in Figure 2.10 has three stages. First the raw materials are introduced to a melting

furnace which is heated to 1500-1600C. Then the melted material is poured at 1000C to a

tin bath where it floats on the molten tin. In this stage the glass spreads out and forms an

even surface. The thickness of the ribbon is controlled by the speed at this step. The last step

is the annealing lehr where the glass is slowly cooled down at 100-500C in order to

minimize residual stresses in the final product (Haldimann, et al., 2008).

Figure 2.10 The basic float glass process

Through this process a glass thickness of 2 to 19 mm can be obtained. After cooling, the

resulting sheet (Figure 2.11) is cut to sheets of 3.21mx6m. The glass obtained through this

method has the advantage of being mass produced guaranteeing a superior material quality.



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Figure 2.11 Float glass production

2.2.2 The heat tempering process

As annealed glass/float glass is very sensitive to tension stresses, it is useful to impose a

favorable pre-compression on the surface of the glass sheet. During the tempering

procedure tensile stresses are introduced in the core of the element and compressive

stresses in the surface. The surface flaws are compressed and while the tensile stresses

resulting from the actions are smaller than the compressive stresses there will be no crack

growth initiation.

During the process annealed glass is heated up to 620-675C in a furnace and cooled down

afterwards (Figure 2.12).

Figure 2.12 Glass heat tempering process

During the cooling phase the exterior side of the glass will solidify first. When the interior of

the sheet is cooling down the thermal shrinkage will be set back by the already solid exterior

surface introducing in the element the specific residual stresses (Figure 2.13).



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Figure 2.13 Transient stress field during the tempering process(Haldimann, et al., 2008)

The tempering procedure influences also the fracture pattern of the glass. The fracture

pattern of a specific glass element depends on the energy stored inside it. The more

accentuated the tempering process is, the bigger the residual stresses will be and the glass

will shatter into smaller pieces (Figure 2.14). Heat strengthened glass and float glass breaks

into larger shards and the behaviour is more favourable making an arch effect possible,

while fully tempered glass breaks into smaller shards and doesn’t make interlocking possible.

Figure 2.14 Post breakage behaviour of laminated glass made of different glass types(Haldimann, et al., 2008)

Because of the production process of tempering by heat, the tolerances will rise to several

millimetres. The thermal treatment is done on the element after all the other mechanical

works (cutting, drilling) are finished because during mechanical works the stress state is

perturbed, and a sufficiently high tensile stress at the surface can shatter the whole glass

element into pieces (Haldimann, et al., 2008).

2.2.2.1 Fully tempered glass During the process of obtaining fully tempered glass, the heating phase is followed by a

rapid cooling phase. The glass is quenched and quickly cooled by cold air to ambient



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temperature. By following this method, residual compressive stresses of 80-170 MPa can be

achieved on the glass surface. Due to these high residual stresses the fully tempered glass

breaks into small pieces. These little pieces are blunt, this being the reason why this type of

glass is also called safety glass.

One specific problem related to fully tempered glass is the possibility of spontaneous

fracture due to nickel sulphide (NiS) inclusions in the microstructure of glass. Depending on

the temperature nickel sulphide increases in volume and introduces supplementary stresses

in the glass element often leading to failure (Figure 2.15) (Haldimann, et al., 2008).

Figure 2.15 Failure through nickel sulphide inclusions

To minimize the risk of failure through nickel sulphide inclusions, glass sheets are filtered

through a heat soak test where they are kept at elevated temperature for a definite time.

2.2.2.2 Heat strengthened glass In the fabrication process of heat strengthened (or partially tempered) glass the glass is

heated up to the same degree as in the process to obtain fully tempered glass but the

cooling process is slower. The resulting residual compressive stresses will be 40-80MPa for

heat strengthened glass. Because of the less stored energy the breaking pattern is

comparable to that of the annealed glass. As it can be seen in Figure 2.16, the fragmentation

pattern is larger than in the case of fully tempered glass and offers a relatively good post-

failure performance (O'Reagan, 2014).



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Figure 2.16 Breakage pattern of the heat-strengthened glass (left) and breakage pattern of the fully-tempered glass

(right)

2.2.3 Chemical tempering

Another tempering process modifies the composition of the glass surface. Chemical

tempering introduces a different pattern of stresses in the glass element. Glass is introduced

in an electrolysis bath where sodium ions from the glass surface are exchanged to potassium

ions (Figure 2.17). The potassium ions are larger than the sodium ions with around 30% and

will introduce compression in the top layer (Haldimann, et al., 2008).

Figure 2.17 Chemical tempering of glass

The depth of the compression zone is in function of time, but can be considered very thin

compared to other methods as it can be seen in Figure 2.18. The thickness of the

compressed zone will be around 20m in 24 hours.



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Figure 2.18 Section through toughened glass showing comparison between the stresses in thermal and chemical

processes(O'Reagan, 2014)

Through the use of the method thinner sheets can also be toughened and the deformation

of the sheets will remain minimal. It is possible to drill and to cut the glass sheet after the

altering process. It is an expensive procedure and it is very seldom used in structural

applications because of the very small thickness that will be in compression.

2.2.4 Laminated glass

Lamination is the process of bonding together two or more sheets of glass by placing

between them a plastic interlayer (Figure 2.19). The sheet laminating process is done in an

autoclave where the sheets of glass and interlayer materials are subjected to elevated heat

(around 140C) and elevated pressure (around 800kN/m2) (Haldimann, et al., 2008). The

sheets can be of different thickness and of different type (float glass and both fully tempered

glass and heat strengthened glass can be used as the sheet’s constituting materials).

Figure 2.19 Laminated glass



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The process changes the mechanical and sometimes also the optical performance. The

procedure is widely used in applications and is favored because of the improved behavior

and post breakage performance. The element stays as one piece when it is shattered. The

glass pieces adhere to the plastic film and the fragments arch and are locked in place. The

exact residual strength is in function of the thickness of the film and the fracture pattern of

the individual sheets.

The most commonly used material between the glass layers is PVB-polyvinyl butyral which is

present in more than 90% of the applications. PVB foil is usually produced in a thickness of

0.38mm and commonly 2 or 4 are used to form an interlayer. The interlayer also

compensates for the unevenness of the glass. As PVB is a viscoelastic material its properties

depend on the temperature and the load duration. Because of the lack of considerable load

transfer through the interlayer, under long load durations or elevated temperatures the PVB

interlayer doesn’t contribute significantly to the mechanical resistance of a non-broken

laminate element (O'Reagan, 2014).

Other used sheet interlayers are the PVB/PET(polyester)/PVB combination, ethyl vinyl

acetate (EVA) or ionoplast sheets.

Ionoplast interlayers are stiff sheets made mostly from ethylane/methacrylic acid

copolymers that may be permanently bonded to glass. An example to such a sheet is

DuPont™ SentryGlas®. For both PVB and ionoplast interlayers the Young’s modulus is similar

at low temperatures (<0C), but at higher temperatures an ionoplast polymer has higher

stiffness for a large range of temperature. A key benefit for such an interlayer is that in the

structural analysis the bonding of the sheets can be considered. This results in higher

resistances and lower deflections (Bennison, et al., 2008).

Resins can be also used as interlayer materials, the mostly used being acrylic, polyurethane

and polyester resins. In the application process the glass sheets are distanced and the resin

is poured between them. The brink is sealed and a curing process using chemical reactions

or ultraviolet light solidifies the resin.

The interlayers can also be coloured or printed and can be also used to enhance sound

insulation or fire protection.



29

2.3 Glass used in structural systems

2.3.1 Glass beam

A glass beam is a linear structural element made of glass that withstands mostly bending and

shear stresses. Glass beams are used largely in roof structures and in fins. Glass fins are

vertical beams that support facades and withstand the wind loads. Three types of glass

beams can be distinguished. Continuous glass beams are usually made of one single piece of

glass (usually laminated glass) and each layer is covering the full span of the beam (Figure

2.20) (O'Reagan, 2014).

Figure 2.20 Continuous beam - Entrance Pavilion of Broadfield House Glass Museum

Segmented glass beams are glass beam segments that are joined together by mechanical

connections (bolted, bolted friction grip etc.) achieving larger spans (Figure 2.21).

Figure 2.21 Segmented glass beam - Canopy above the entrance of the Yūrakuchō’s underground train station in Tokyo,

Japan



30

Splice laminated glass beams are overlapping glass sheets that are laminated together to

cover longer spans (Figure 2.22).

Figure 2.22 Spliced glass beam being lifted into place

(O'Reagan, 2014)

In function of the supports and the design chosen the beam may behave as a cantilever, a

single span beam or a continuous beam, influencing the bending diagram.

A special type of application for glass beams is the possibility to fabricate glass I-beams as

shown in Figure 2.23. In these hybrid beams the web is made of glass and the flanges are

made from another material (wood, steel) that improves the beams characteristics. The

connection can be made by glued or mechanical connections.

Figure 2.23 A beam after failure presenting a typical fracture pattern for timber−glass hybrid beam with the web made of

annealed float glass



31

The design of glass beams can be made using finite element methods, using elastic stability

theory or by using 1:1 testing, or using analytical design rules. When testing glass beams

usually 4 point bending is applied to get results for a population of flaws.

The governing design criterion is linked to both strength and redundancy. The design is

influenced by safety concepts developed to counteract the fact that glass is a brittle

material. To increase the redundancy and improve the beams pre- and post-breakage

behavior beams are usually fabricated as glass sheets laminated together. This solution

makes possible for the beam to withstand loads even if one/more of the sheets fail. The

interlayer between the sheets will also help to keep the possibly broken pieces in place,

prevent injuries and improve the behaviour by the arch effect. In most of the cases the

advantages of tempered glass (elevated strength, decrease of sensitivity to thermal

breakage failure) are used for the withstanding of loads.

The failure of the glass beam usually occurs when the tensile strength is exceeded on the

surface of the beam. The bending of the beam is accompanied by the lateral torsional

buckling (LTB) if there are not enough lateral restraints on the compressed part of the beam.

LTB produces a lateral deflection and a twisting deformation as seen in Figure 2.24

(Haldimann, et al., 2008). For design, analytical models based on second order theory and

buckling curves derived from buckling tests and numerical FEA models may be used. It is

possible to define LTB buckling curves for glass, but in the present the buckling curve C from

Eurocode is used handling the LTB design in a conservative manner.

Figure 2.24 Lateral torsional buckling model with bending moments applied at both extremities (Haldimann, et al., 2008)



32

The buckling resistance of the glass beam is governed by the tensile resistance due to the

high compressive strength. Other influencing characteristics for the calculation and design

are the moment distribution along the beam, the boundary conditions, the distance from

the centre of gravity of the section to the point of load application, the glass thickness, the

initial deformations (depending on the type of glass), the load duration, the tensile strength

of glass and the surface quality (O'Reagan, 2014).

In case of every glass structural element it is vital to pay attention to the details. The

supports, the restraints may be the source of load concentrations in case of an inappropriate

design.

The serviceability limit state control lays mostly in the deflection and vibration check. In case

of float glass only low tension stress levels are allowed reducing the eventuality of high

deflection, but in the case of laminated and tempered glass the higher stress levels make it

important to perform a thorough check for deflections. A check for vibration is necessary

especially if the beam is the support of a floor plate or cladding. In these cases the natural

frequency is checked to avoid possible excitation by traffic or other sources.

2.3.2 Glass column

A glass column is a linear structural element made of glass that withstands mostly

compression. Under compression loads the main failure mode for a column is buckling

instability.

In case of a glass column the slenderness ratio has to be based on the highest tensile

strength. This value can be obtained from elastic second order equations. In case of

compressed glass elements the approach of using column curves can be used.

Similar to glass beams, glass columns should behave in a redundant way. In case of failure

the loads have to be able to redistribute along the structure or the column has to be

fabricated from at least 3 sheets of glass, where the column would still resist after the failure

of 2 from the 3 layers.

Any type of glass product, annealed glass, fully- or partially tempered glass may be used as

long as the stresses don’t exceed the allowable limits, however annealed glass and partially

tempered glass are more benefic because of the enhanced post breakage performance.

Laminated columns can rarely be considered as composite elements. Because of the

possibility of long load duration and elevated temperatures the interlayer shear modulus

should be considered zero. Ionoplast interlayers are somewhat exceptions because they are

more stable. In their case some amount of composite action can be considered. In case of

short term loads (wind blasts) the composite action may be considered (O'Reagan, 2014).

In the design procedure of the column the imperfections have to be taken into

consideration. The amount of imperfections varies in function of the post treatment of the



33

glass. For annealed glass the imperfections can be considered L/2500, while for fully

tempered glass this value is L/300.

Connections can be fully fixed moment connections or point support connections, the main

design principle being that of avoiding stress concentrations. Adhesive based solutions are

often used to make the load distribution more even.

2.3.3 Glass slabs

Glass slabs are mostly used to get a transparent/translucent walking surface (Figure 2.25).

This glass floor may also support other permanent additions like glass walls or balustrades.

Every type of glass may be used for the fabrication of glass floors, but mostly laminated glass

is used with heat treated sheets, to improve the pre-breakage and post-breakage

performance of the system (O'Reagan, 2014).

Figure 2.25 Floor plate supported by glass beams(O'Reagan, 2014)

The uppermost glass sheets are treated with sand blasting, acid etching or enameling to

provide slip resistance for the users. This treatment may decrease the tensile strength of the

treated surface by up to 40% but it won’t affect the design as the face that works in tension

is not affected (unless the slab is continuously supported). The translucency effect is also

often needed to offer privacy.

One major design criterion, as in case of other glass elements is the concept of redundancy.

A glass panel always has to remain in place. Even if the failure of the glass sheets occurs, the

interlayer has to keep the shards in place and enable the post-breakage arch-effect.

From a design point of view a glass slab withstands short-term and long-term loads. As the

strength of the glass depends on the load duration, for shorter actions a larger resistance

may be considered. Self-weight, variable action and concentrated variable action should be

considered for design purposes. Usually the concentrated variable action is the one that



34

results in the highest bending stress and therefore is critical for the structural integrity. Even

with a detailed design process, every system should also be verified through testing.

(O'Reagan, 2014)

As considered also in other materials, if the laminated glass sheets length to width ratio

exceeds 2, a 2 side support has to be considered, and the assumption that the interlayer

material (in case of a laminated sheet) provides no structural stiffness has to be made.

From a serviceability point of view, usually the deflections and the floor vibrations have to

be limited. The deflection limit is often considered span/250, calculated for the load of both

variable and permanent actions. The natural frequency is mostly limited to 5Hz.

In practice, glass panels are often supported on all 4 edges (or sometimes on 2 edges) by a

steel system and a particular attention has to be paid to the possible stress concentrations

that can occur at the supports. Direct contact with glass and metal has to be avoided and an

appropriate interlayer material has to be provided. An example for a glass panel-steel

support system can be seen in Figure 2.26 (O'Reagan, 2014).

Figure 2.26 Example of a continuous support to a floor plate(O'Reagan, 2014)

2.3.4 Glass walls

Glass walls can be used both as outside envelopes and also as inside structural elements

(Figure 2.27). The walls may be single planed or laminated, and for enhanced thermal

properties sometimes also double glazed.



35

Figure 2.27 Interior glass walls

The design of glass walls is similar to the design of floor panels. A major difference is that

glass walls have usually just two edges restrained (bottom and top) and they have to

withstand also axial actions (self-weight and other supported elements). The design case to

axial loads is similar to columns and the use of buckling curves is possible. In the case when

the wall also ensures lateral stability it is also subjected to shear forces. The two restrained

edges can be a variation of pinned and fixed connections (combined with a fixed edge, one

edge can also remain free). The theoretically fixed connections are hard to achieve. It is

more adequate to consider in the modeling a rotational stiffness or a spring as a support. As

in every glass connection, a particular attention has to be paid to the possible stress

concentrations. The deflection, settlement, creep of the support structure also has to be

considered in the calculations (O'Reagan, 2014).

As walls mostly support a higher axial load the deflection restrictions are very severe

considering the column type design. If the glass wall is used as a barrier, the deflection limit

for balustrades has to be verified.

Figure 2.28 Application of glass walls and glass fins - Apple store, New York



36

2.3.5 Connections in structural glass

Mechanical and adhesive based are the two main types that can be distinguished in glass

connections. Mechanical solutions are the older types used in glass design. They can be of

various types, but the most widespread are the linear supports, the clamped and friction

gripped fixings and the simple bolted connections (Figure 2.29) (Wurm, 2007).

Figure 2.29 Glass connection systems(Wurm, 2007)

The connection should be able to fulfil its structural task, it should not damage the glass in

the service life and it should allow fabrication tolerances. To achieve these goals a particular

importance is paid not to allow the direct contact between glass and metal. Usually an

interlayer material is placed between them to spread the stresses and redistribute the loads.

For most cases the use of a heat treated glass type is advised because regular float glass is

not strong enough to withstand the stress concentrations around a mechanical connection

(especially around the boreholes).

The continuous linear supports connect the glass to a frame or to another glass element. The

panels are mostly supported on 2 or 4 sides. Isolated clamps and friction grip connections

are more appealing from a visual point of view, because they have smaller visual impact. The

friction grip connection has the advantage of redistributing the stresses on a larger area.



37

Figure 2.30 Bolted connection types

Bolted connections (Figure 2.30) may allow or restrain in plane movement, while they (as

the other type of connections) also have to compensate for the movements of the supports

and the stresses induced by temperature changes (Figure 2.31).

Figure 2.31 Point-supported framing system

Adhesives are widely used in the connections for glass elements. Adhesive based

connections are advantageous compared to mechanical connections because a more

uniform load-distribution pattern can be obtained. The connection is homogeneous, no

holes are needed and thus the local stresses are reduced. Examples for adhesive based

connections can be seen in Figure 2.32 (Santarsiero, 2012).



38

Figure 2.32 Adhesive glass‐to‐steel connections(Santarsiero, 2012)

From a structural point of view the adhesives can be classified based on their modulus of

elasticity, as shown in Figure 2.33, but this characteristic has also a strong connection to the

microstructure of the adhesives (Wurm, 2007).

Figure 2.33 Stress-strain graph of various adhesive systems(Wurm, 2007)

The synthetic adhesives used with glass elements can be elastomers, thermoplastics or

thermosets.

“Elastomer materials are those materials that are made of polymers that are joined by

chemical bonds, acquiring a final slightly crosslinked structure” (adhesiveandglue.com).

Elastomer adhesives can be stretched several times their original length and the adhesive

returns to its original length when the stress is removed. These adhesives have relatively low

tensile strength but they produce a high elongation at break. The low modulus of elasticity

enables to these adhesives to distribute the stresses evenly when used in a connection.

Typical elastomer adhesive is the polyurethane adhesive (2 components), adhesives based

on silicones and adhesives based on modified silane.

“Thermoplastic materials are those materials that are made of polymers linked by

intermolecular interactions or van der Waals forces, forming linear or branched structures”

(adhesiveandglue.com).

Thermoplastic adhesives get softer when heated and harden back if they are cooled down.



39

They do not cure or set, no cross links are formed. The change under heat exposure is

merely physical. They allow plastic deformations under heat. A thermoplastic adhesive can

be heated and then injected to the destination place where it hardens to its final shape.

Typical thermoplastic adhesives are the acrylates and the cyanoacrylates.

“Thermoset materials are those materials that are made by polymers joined together by

chemical bonds, acquiring a highly crosslinked polymer structure.” (adhesiveandglue.com)

Thermosets solidify using another component (resin, hardener) through a chemical process

or by the exposure to heat or UV light. Once cured, the changes in the material properties

are irreversible. If they are heated after solidification they will not soften or melt.

The highly cross linked structure of the adhesive ensures high rigidity and resistance

compared to other adhesives. They have high strength but they have short elongation at

break.

Typical thermoset adhesives are epoxy adhesives, unsaturated polyester adhesives,

polyurethane adhesives and anaerobic adhesives (Cheremisinoff, 2001).

Depending on the thickness that is necessary for an adhesive, the types of contact adhesives

(thickness less or equal to 1 mm) and gap filling adhesives (thickness equal or more than 5

mm) can be distinguished.

A glued connection’s one particular concept is the optimal glue thickness. The phenomenon

of the glue thickness influencing the connection resistance can be seen in Figure 2.34

(Wurm, 2007).

Figure 2.34 Graph of strength against layer thickness for a hard adhesive and an elastic adhesive(Wurm, 2007)

The design values provided for the adhesives are based on the premise that the adhesive will

fail due to the loss of cohesion (the failure will occur inside the adhesive) or by substrate

failure (the failure of the glass) and not by adhesion failure (at the adhesive-glass surface)

which is considered the worst type of failing. To ensure a proper behavior adequate surface

conditions have to be provided.

The redundancy concept has to be applied also to glass connections. The failure of a

connection shouldn’t result in a disproportionate collapse of the structure. In some countries



40

it is mandatory to install a secondary system that will prevent collapse in case of adhesive

failure.



41

3 State of the art

3.1 Overview

State of the art is considered the most recent stage in the development of a product, incorporating the newest ideas and the most up-to-date features. As this thesis is not a research topic, but an Android application development project, the state of the art meaning has to be interpreted accordingly. In case of software applications, it can be considered as a market search. The environment in which the application should perform has to be clearly researched, as the strengths of the application has to be built on the market needs to build a successful product. New technologies, and new development approaches are also crucial to obtain a final product that can compete on the market. The State of the art consists of three loosely connected topics that ensure a thorough market search, and present database tools and development methods:

Applications for structural glass design – Presents the market conditions on which an Android structural glass application would have to compete.

Databases – Different types of databases can be used to offer enhanced value for an application, this chapter presenting two from the advantageous implementable solutions.

Agile software development – Presents a relatively new approach to software development, used in the development process, where the software is built up and developed in separate functionality blocks.

3.2 Applications for structural glass design

Applications are software that are developed to accomplish a specific task. They are

developed to run on a specific operating system and are usually designed to run optimal on

specific devices. Applications are usually acquired from application stores that are digital

distribution platforms, mostly for handheld devices. The two most important application

stores (considering users and download numbers) are Google Play and Amazon Appstore for

Android operating system and iOS App Store for iOS operating system, with more than 1.3

million apps for each platform.

The University of Coimbra already has a vast experience with application development, as

applications for different structural engineering topics were already developed for Android

and for iOS, in a partnership with CMM - Associacao Portuguesa de Construcao Metalica e

Mista. The EC3 Steel Member Calculator is a calculation tool for beams, columns and beam-

columns, and also provides a database for hot-rolled I-section profiles, cold-formed and hot-

finished tubular profiles, and mechanical fasteners. The Buildings LCA application provides a

simplified Life Cycle Analysis (LCA) at the product level and at the building level, and treats

three different approaches for the Life Cycle Analysis, a cradle-to-gate analysis, a cradle-to-

gate analysis plus end-of-life recycling, and a cradle-to-grave analysis plus end-of-life



42

recycling. The Ferpinta application calculates the resistance of columns, beams and beam-

columns based on EC3-1-1, and also provides a database of cold formed steel welded

structural hollow sections fabricated by FERPINTA.

For an application to be successful it has to provide a service that is needed on the

application market for less money than the present applications, or the offered services have

to be of a higher quality to attract users. An overview of the market is necessary to

determine which areas are not covered from the point of view of an application that wants

to aid structural glass design. When searching the App Stores for keywords like “glass”,

“glass structure” or “structural glass” some conclusions can be drawn. Almost none of the

applications with “glass” in the name or in the description are related to structural

engineering. There are a couple of applications that are relatively unknown that treat glass

from different viewpoints. The “GlassWeigh” application (Figure 3.1) solely calculates the

weight of a specified glass amount, while the “Construction Materials Engg.” and “Civil

Engineering-Basics” applications present some theoretical overview.

Figure 3.1 The Glass Weigh application

A slightly different approach to find an application related to glass design is to search for

companies that are closely related to structural glass. A couple of important companies have

applications presenting their portfolio related to glass products. The “Glass Facade”, “Glass



43

Design” and “Glass Vision” by Saint-Gobain and “Sosoares” by Sosoares can be considered of

this type. Another category of “glass” applications are the ones that help the user choose a

desirable product of the company. “Glass Compass” and “Saint-Gobain Isolierglascenter” are

an aid to in choosing insulating glass units through calculation. The “Sika” calculation tool

can be also considered as such, as it calculates how much sealant or adhesive is needed for a

project, also considering the sealing of facade joints.

Another category of software products for glass are the desktop software like Calumen II

(Figure 3.2) that offer wider calculation possibilities, but they only treat insulated glass units,

and only from a thermotechnical point of view.

Figure 3.2 The interface of the Calumen II

When compared to other materials like steel and concrete, it can be seen that there are

plentiful applications for various structural problems for steel and concrete, with a high

number of downloads (Figure 3.3). As there are also free applications and also more

complex versions for pay, at various level of sophistication, it can be assumed that the

market of steel and concrete handheld device applications is highly variable and partly

saturated.



44

Figure 3.3 Applications on Google Play for "concrete"

In comparison, and as a conclusion it can be said that there are no applications for Android

or iOS that treat glass from a structural point of view, that make resistance calculation

possible.



45

3.3 Databases

3.3.1 Relational Database management systems (RDBMS)

The most common database type is the relational database, which is a traditional two

dimensional database format. They first appeared in the 1980’s and they are the most

widespread ever since. The popularity of relational databases is due to the high efficiency in

case of simple data, simple relational tables and many user tools. Relational databases are

optimal to store simple data in tables. In the case of glass design it can be easily used to

represent the state of the glass market, to represent products and prices. However, they

can’t handle many-to-many situations and are not suitable to represent complex data.

Relational databases are sets of tables which store the data in two dimensions, namely in

rows or tuples, that can be considered an ordered list of elements, and columns (attributes

or fields) (Figure 3.4). The data stored is mostly simple data (integers, strings) and every cell

has only one corresponding value. In these tables the data is not arranged in order, a

primary key is required to identify a specific row.

Figure 3.4 Relational database terms

The data is “normalized” in the database, so that information is not stored in duplicates and

the changes can be made more efficiently. Some basic operations are possible in the

database to manage the data. The classical operation types are union, intersection and

difference, but also selection (selection according to a filter), projection (selecting a part of

the attributes/columns of the table) and join (combination of Cartesian product with

selection and projection) operations are possible. The operations are made possible by the

use of a programming language specific to databases.

Relational database servers use SQL (Structured Query Language) as communication

language (Figure 3.5). This special programming language is especially for data management

inside a relational database management system, and is the most widespread language in



46

database managing. SQL makes possible actions like data insertion, query, update and delete

of data, data access control etc.

Relational databases have been improved with object oriented features like user-defined

data types and structured attributes to respond to some of the requests of object-oriented

programming.

As in the application mostly simple data formats are used, this type of system was used to

build the SQLite database that functions as the core of the data presenting functionality used

in the application (Burnette, 2010).

3.3.2 Object-oriented database management systems

Object-oriented database management systems (object databases) were developed because

of the spreading use of object-oriented programming (Java, C++). The database follows an

object oriented data model based on classes, properties and methods. While classes define

the data and the methods an object will contain, the methods define the behavior of the

object. Objects can contain both executable code and data. A query language similar to SQL

is used for data management and object manipulation. The main concept behind these types

of databases is to store the objects in a database and save time and resources by skipping

the conversion and decomposition. In glass design applications, entire structural elements

can be stored as objects, with all specific characteristics. However, if not treated as an

object, compared to relational databases additional resources (necessary for the conversion,

decomposition) are needed to get only specific information out of the object.

Object databases are used in case of complex data or complex data relationships (object

databases can handle many-to-many situations). They are mostly used in spatial databases,

telecommunication, and scientific areas.

This system is highly advantageous when saving complex data-structures. By using objects, it

is possible to save complex data-structures like entire beams are glass sheets (Burnette,

2010).

Figure 3.5 The three most popular database management engines: Oracle, MySQL and Microsoft SQL Server



47

3.4 Agile software development

Agile software development is an alternative to traditional style project management and

software development. Traditional software development implies the complex planning of

an application development, where the development steps are aligned one after the other.

Agile recommends an incremental software building approach from the beginning of the

project. Larger projects are broken down to smaller functionalities called “user stories” in

Agile terminology, and the delivery is done in multiple steps, called iterations as it can be

seen in Figure 3.6. The approach assumes that not every requirement can be identified

before the design and the coding steps, as in the traditional approaches (agilemanifesto.org).

Figure 3.6 Comparison of the traditional and Agile software development approach, source:

http://www.agilenutshell.com/how_is_it_different

This environment is highly favourable if the requirements are changing during the lifetime of

the project development. As the plans can be considered short-term, it is easier to handle

changes and implement an adaptive planning. Adaptive planning means focusing on the

important functionalities in case of a time struggle and even dropping the least important

features in exchange of a well written, fully tested software.

An early step of the Agile development process is the listing of the needed software

requirements in small features. The features are sized, first relative to each other (Figure

3.7), and an estimate is made for the implementation time for each of them. This step can be

considered very important, as the accuracy of the predictions are based on this step.



48

Figure 3.7 Relative sizing of the user stories, source: http://www.agilenutshell.com/estimation

To every functionality, a priority is attributed, and the implementation process is started

with the most important feature. Throughout the development an iterative process is

present, as a simple feature is increased incrementally over time. Iterations can be

considered time intervals of a couple of weeks, where the steps of analysis, design, coding

and testing are all present continuously adapting changes and improving the product.

Continuous feedback is ensured by the continuous delivery process. At the end of every

iteration, a completely functional feature is delivered that is running and thoroughly tested

(opposed to the traditional development style, where testing is only done in the last phase).

As after an iteration there is a feedback loop from the stakeholders, risks are minimized and

fast and early decision making and adaptability in guaranteed. This method is also useful to

track the progress of the project. “Burndown” charts like Figure 3.8 are used to show the

amount of work done and the amount of work due, taking into consideration the iteration

steps (agilemethodology.org).

Figure 3.8 Burndown chart, source: http://www.agilenutshell.com/burndown



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4 Design procedures for structural glass

4.1 The E1300-12a

The American E1300-12a is the standard practice for determining load resistance of glass in

buildings and it was issued by ASTM (American Society for Testing and Materials). It is mainly

used for the load resistance and deflection calculation for vertical and sloped glazing. The

procedure described in the design code is used to determine the load resistance of glass in

buildings and to determine, through the use of charts, the approximate maximum lateral

glass deflection. The results obtained are for glass sheets that are simply supported along

the edges (2, 3, 4 sides), or in a cantilever position. A uniform lateral load distribution has to

be considered and the sum of the considered loads (self-weight, snow, wind) has to be less

than 15kPa. The associated probability of breakage is less or equal to 8 glass sheets from

1000 and the calculations are made under the assumption that the surface condition of the

glass is typical to a glass in service for several years, being weaker than freshly manufactured

glass. The design methodology does not apply to glasses that suffered a post-treatment with

resistance reducing effects (etching, sandblasting etc.) or to glass sheets that are not used as

glazing (glass floor panels, structural glass members etc.) (E1300-12a, 2009).

Laminated glass is considered in the design code only with PVB (polyvinyl butyral) or

equivalent interlayers. In case of laminated glass, a combined thickness is designated to the

plies based on the thicknesses of the individual sheets and the thickness of the interlayer

material.

The standard considers loads that act for short durations (less than 3 seconds) and long

durations (approximately 30 days). The calculations are based on a theoretical glass

breakage model and the results are condensed in non-factored load (NFL) charts (Figure 4.1)

which represent a 3 second uniformly distributed load with a probability of breakage less

than or equal to 8 sheet from 1000 for monolithic annealed glass (E1300-12a, 2009).



50

Figure 4.1 Non-factored load chart for 2.5 mm glass with four sides simply supported, source: (E1300-12a, 2009), p. 8, Fig.

A1.1 (upper chart)

In the design procedure, based on the dimensions of the rectangular glass sheet and the

edge support conditions, the non-factored load can be determined by the use of a chart. The

non-factored load is multiplied by the glass type factor (obtained from a table) to get the

final load resistance of the sheet. In function of the lateral load, the area of the glass sheet

and the aspect ratio, the maximum lateral glass deflection can be obtained from specific

charts (Figure 4.2).

Figure 4.2 Deflection chart for 2.5mm glass with four sides simply supported, source: (E1300-12a, 2009), p. 8, Fig. A1.1

(lower chart)



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The appendixes of the design code contain information related to a procedure for an

alternative deflection calculation method, the determination of type factors, determination

of load duration factors (Table 4-1) and combination of the loads of different durations. Also,

procedures can be found for the determination of the approximate maximum surface stress

and equivalent thickness calculation for laminated glass.

Table 4-1 Load duration factors according to E1300-12a

Duration Factor

3 s 1

10 s 0.93

60 s 0.83

10 min 0.72

60 min 0.64

12 h 0.55

24 h 0.53

1 week 0.47

1 month (30 days) 0.43

1 year 0.36

beyond 1 year 0.31



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4.2 The DIN 18008

The German DIN 18008 treats the design and construction rules for glass in buildings. In

parts 1 and 2 the subchapters Terms and general bases and Linearly supported glazings are

treated.

For glass design, partial safety factor method has to be used, and both the ultimate limit

state (ULS) and the service limit state (SLS) have to be verified. The relationship Ed≤ Rd has to

remain true, where Ed is the design value of actions (here, stresses) and Rd is the design value

of the resistance. The loads applied on the glass sheet have to be determined from

specialized design codes. The characteristic resistance is assumed to be at 5% fractile. A

linear elastic glass behaviour has to be considered. The design code fixes some major

characteristics of the soda lime silica glass, as the modulus of elasticity (E) being equal to

70000N/mm2, Poisson’s ratio (ν) being equal to 0.23 and the thermal expansion coefficient

(αT) being equal to 9.0*10-6/K (DIN18008-1, 2010).

The design code is valid for glass thicknesses between 3 and 19 mm, and forbids the use of

glass sheets if the depth of the flaws is deeper than 15% of the thickness. The glass sheets

are distinguished based on their inclination as horizontal (inclination>10◦) or vertical

(inclination≤10◦).

The resistance of a glass sheet is determined in function of the glass type. For glasses

without thermal tempering the equation (1) is used, while for thermally tempered glasses a

modified formula is used (2), that takes into consideration also the kmod factor (DIN18008-1,

2010).

(1)

(2)

The value of fk represents the characteristic bending tensile strength of the glass sheet. The

factor kc depends on the art of the construction and is equal to 1 if not specified otherwise.

For glass sheets without thermal strengthening, supported on all four sides, the kc factor can

be taken as equal to 1.8 (DIN18008-1, 2010).

The kmod factor takes into consideration the pronounced modification in behaviour of a glass

sheet without thermal tempering, depending on the load duration, to account for the

reduction of glass strength due to stress corrosion (Machado, 2011). Three load duration

categories are taken into consideration as seen in Table 4-2.

Table 4-2 Values of kmod in function of the load duration, source: (2010), p.12, Tab.6

Load Example kmod



53

duration

Permanent Self-weight 0,25

Medium Snow 0,4

Short Wind 0,7

The kmod factor is selected based on the load type that acts for the smallest amount of time.

Every ULS load combination has to be checked during the design procedure because the

design resistances change depending on the combination (duration of loads in a

combination). Thus a combination with the maximum resulting load may not be the

determining one from the point of view of the design (Schneider, 2008).

In the case of laminated glass, the resistance values may be enlarged by 10%, but in case of

edges subjected to loading, for glass sheets without heat tempering the resistances should

be considered as only 80%.



54

4.3 The CAN/CGSB-12.20

The CAN/CGSB-12.20 is the National Standard of Canada titled Structural design of glass for

buildings, and includes the procedures recommended for the structural design of soda-lime

glass for use in buildings (windows, glass doors, partitions, etc.). The code considers two and

four sided support of the glass plates. The load types are divided into four categories, D-

dead loads (self-weight), L-live loads due to snow, Q-live loads due to wind and earthquake

loads and T-effects of temperature difference. Other actions like the settlement of the

building and impacts also should be considered. In structural analysis, the modulus of

elasticity (E), of glass should be considered 70000MPa. In case of patterned glass, the

minimum thickness should be used, and laminated glass should be considered as monolithic

only if the load duration and temperature limits fixed in the code are not exceeded (else, it

should be treated as a layered assembly) (CAN/CGSB-12.20, 1989).

The code describes the procedure to determine the factored loads and the factored

resistance (4), the main objective of the design being to have the factored resistance higher

than the factored loads. The factored load can be determined using (3). αD is equal to 0.85

for uplift and 1.25 for other cases. αL and αQ are both equal to 1.5 and αT is equal to 1.25.

(3)

(4)

where:

γ - taken as 1 for regular buildings and 0.8 for buildings that upon collapse would not cause

injury

ψ - load combination factor, that can be 1, 0.7 or 0.6, and varies in function of the number

and type of the considered loads

R - factored resistance, indicates the glass strength and includes a resistance factor

depending on its variability and nominal risk of failure

Rref - factored resistance of annealed glass loaded to failure in 60 seconds, where 0.8% of the

units are expected to fail.

c1 – glass type strength coefficient

c2 – heat treatment strength coefficient

c3 – load duration strength coefficient

c4 – load sharing strength coefficient (in case of double-glazed or triple-glazed insulated glass

units)

For glass sheets with aspect ratios smaller than 5, graphs (Figure 4.3), tables are provided to

help in the determination of the factored resistance or the necessary thickness.



55

Figure 4.3 Reference factored resistance-4mm glass

Also, the minimum necessary thickness can be expressed as the minimum from formulas (5)

and (6). For glass sheets with an aspect ratio of above 5, formula (7) gives the minimum

necessary thickness. In the above mentioned formulas, a and b represent the short and the

long side of the glass sheet, while R is the required factored resistance and c is the strength

coefficient.

⁄ (5)

⁄ ⁄ (6)

⁄ (7)

As glass lights can deflect 2 to 6 times their thickness under large loading, large deflection

theory should be used for the deflection determination. The deflection is calculated for

effective pressure, not taking into consideration the load coefficients. The deflection of a

two edge supported glass plate is expressed in equation (8), while in the case of a four edge

support, equations (9), (10), (11) and (12) are substituted into equation (13) to obtain the

final deflection. In the equations, h stands for the glass plate thickness, p for the effective



56

uniform pressure and a is considered the span between the supports in case of a two side

supported plate, while a and b are taken as the short and long dimensions of the glass sheet

in the case of a four sided support (CAN/CGSB-12.20, 1989).

⁄ (8)

(9)

⁄ ⁄ ⁄ (10)

⁄ ⁄ ⁄ (11)

⁄ ⁄ ⁄ (12)

(13)



57

4.4 The AS 1288-2006

The Australian standard, Glass in buildings-Selection and installation, presents procedures

for the selection and installation of glass in buildings subjected to wind loading and human

impact. The glass strength requirements are based on the tensile stresses developed on the

surface of the glass.

The main relationship that has to be fulfilled is:

(12)

Where S* represents the design action effect determined by elastic analysis, and φRu

represents the ultimate design capacity (AS1288-2006, 2006).

The ultimate design capacity is the product of the capacity factor (φ), taken as 0.67, and the

nominal capacity (Ru) is given by:

(13)

The coefficients c1, c2, c3 are the glass type factor, the surface type factor and the load

duration factor. ft’ is the characteristic tensile strength of the glass in MPa. It is equal to (14)

when considering the edge of the glass panes and equal to (15) away from the edge of the

glass panes, where t is the minimum thickness of the glass sheet in millimetres. The edge of

the glass is considered the outermost part of a glass sheet with a width equal to the sheet

thickness. Symbol X is a geometric factor that depends on the size, shape and support

conditions of the glass sheet (AS1288-2006, 2006).

(14)

(15)

In case of laminated glass sheets for short-term load durations minimum glass thickness

should be considered in the calculations, without considering the interlayer thickness, while

for medium or long-term loads the strength of each sheet should be tested, where every

sheet takes an amount of the load sharing factor, ksheet (16) of the total load.

∑

∑

(16)

The design calculations should be based on the actual glass thickness, or (if the actual glass

thickness is not known) on the minimum thickness for the specific nominal thickness.



58

The maximum deflection is limited to span/60 for glass sheets supported on 2-3-4 edges and

height/30 or cantilever length/30 for cantilevered panels.

In case of wind loads, wind pressures are considered to be less than 3 seconds in duration

and under 10 kPa. Formulas and predefined constants are provided in the code to determine

the maximum span allowed in case of a specific thickness. A distinction is made between a 2

or 4 sided support, with the mention that a 3 sided support should be considered as a 2

sided one.

In case of an aspect ratio higher than 5, a two-edge support should be considered.

The informative appendix describes methods for the calculation of the critical elastic value of

the maximum moment. Depending on the type and amount of restraints the code

distinguishes between beams with intermediate buckling restraints (17), beams with no

intermediate buckling restraints (18) and continuously restrained beams (19). The code

provides tables for the determination of the constant factors g1, g2, g3 (AS1288-2006, 2006).

( ⁄ ) (17)

( ⁄ ) ( ⁄ )

(18)

⁄ [

]

(19)

where: d - depth of beam

G - torsional elastic modulus

g1 - slenderness factor



J - torsional moment of inertia

Lay - distance between the effectively rigid buckling restraints / distance between points of

effective rigid rotational restraints

Mcr - critical elastic value of the maximum moment yh - location from the neutral axis of the loading point

y0 - distance of the restraints from the neutral axis



59

4.5 Comparison of the considered design codes

The four considered design codes have similarities, but also several important differences. It has to be mentioned that only a superficial comparison is possible between the design codes, as the approaches are different and for a global overview an understanding of the entire design process of a country is needed. This procedure is not easy to follow through, as it is hard to acquire all the design codes for the studied countries. In the comparison procedure the main accent was put only on the glass design codes mentioned earlier in the chapter. The global approach from the glass design codes can be considered different in case of the German DIN18008 where a resistance is the final output, not considering a specific glass sheet, and the other three design codes (American, Canadian, Australian), where the output data is focused on specific design issues, like minimum necessary thickness or maximum allowed span (DIN18008-1, 2010) (AS1288-2006, 2006) (CAN/CGSB-12.20, 1989) (E1300-12a, 2009). Only the three non-European design codes use tables and graphical representations to aid the calculation procedure. All of the design codes take into consideration the duration of the loads, offering different

load intervals and coefficients for the calculation process. The minimum amount of

alternatives is given by the German and Canadian design code, where only 3 load duration

possibilities can be specified, while the American design code includes a total of 11

possibilities. All of the design codes consider 2 and 4 side linear support conditions, while

only the American one treats specifically cantilever cases.

All of the design codes specify upper and lower boundaries for the thickness of the glass sheet that is taken into consideration, these values being the same (3mm (2.5mm)-19mm). The Australian AS1288-2006 is the only glass sheet design code that specifies a glass fin stability calculation method, offering formulas for the determination of the critical elastic value of the maximal moment (AS1288-2006, 2006).



60

German DIN18008 American E1300-12a Canadian

CAN/CGBS1220

Australian AS1288-2006

Probability of failure The characteristic

resistance is assumed to

be at 5% fractile.

A probability of

breakage of 8 sheets

form 1000 is assumed.

A probability of

breakage of 8 sheets

from 1000 is assumed.

Not specified.

Load

safety/combination

factors

From DIN 1055-100:

2001-03.

None specified. Safety factors:αD, αL, αQ,

αT

Load combination factor:

ψ

From AS/NZS 1170.

Material safety factors γM None specified. None specified. Capacity factor: φ

Duration of load

considered in the

calculation

kmod factor, with 3

different load durations

load duration factor,

with 11 different load

durations

c3 load duration

coefficient, with 3


c3 load duration

coefficient, with 5


Calculation tools used in

the design code

- abaqus abaqus and tables abaqus and tables

Output offered by the

design code

Rd - resistance LR – load resistance

deflection

R – factored resistance

minimum necessary

thickness

deflection

φRu – ultimate design capacity allowable maximum span deflection

Glass thickness

considered

3-19mm 2.5-19mm 3-19mm 3-19

Deflection calculation No specific procedure

provided.

Based on charts. Based on formulas. Based on a chart.



61

Types of support

treated in the design

code

2 and 4 sides 1, 2, 3 and 4 sides 2 and 4 sides 2 and 4 sides

Stability Not treated. Not treated. Not treated. Calculation procedure

for the critical elastic

value of the maximal

moment.



62

5 Architecture and development of the code

5.1 General overview

As design methodologies need to be transformed into software code, steps need to be

carried out that allow the transformation. The formulation of a design code, the design

steps, the additional functionalities need to be described algorithmically to allow this step.

Algorithms are step-by-step procedures that have finite number of steps, and generate an

output based on user generated input. For this to be possible, every step of the algorithm

has to be precise, as the implementation of each step is done by the computer.

The various design methodologies and concepts that are needed in the application are taken

into pieces, and arranged in easily interpretable linear steps. After this step is made, using

the syntax of the software language, in case of Android development, Java and xml markup

language, the steps are transformed into software code.

One important concept governing the application development is to offer fast functionality

in a clear, simple and concise manner. The functionalities of the Structural glass application

can be grouped in five major categories, directly accessible from the main menu of the

starting page (Figure 5.1).

Figure 5.1 The Main menu



63

The Knowledge base is an information center related to structural glass, covering the

principles from the material properties to the effective design, and also offering the

functionality of a pre-design guide. It is structured in four chapters offering a brief overview

in the Use of structural glass in civil engineering subchapter, presenting the glass as a

material and the related technological procedures in the subchapter of Material and

technology.

The Glass used in structural systems and the Design procedures for structural glass

subchapters offer an overview on general design guidelines and national codes.

The Glass sheet calculation subpart of the application gathers the glass sheet design

procedures of national standards, and offers fast calculation support for the German DIN

18008, for the American E1300-12a, for the Canadian CAN/CGBS1220 and for the Australian

AS1288-2006.

The Glass member calculation subpart collects calculation modules that help to explore

different design topics through “live” calculation. The cases include fin, T-beam, hybrid beam

and balustrade calculation.

The glass Product database is a collection of products used in the glass design ordered in

categories, with details and company-contact information for every item.

The glass member equivalent for a steel beam functionality makes possible a fast

comparison procedure, considering numerous restraints, but drawing a parallel between

glass and steel.

The About subpart summarizes the development background of the application and

enumerates the sources and additional recommended material.

Android applications are mostly written in Java programming language. The code is compiled

with additional data and resource files into an APK, an Android package. The Android devices

use this package to install the application. Applications are built of four components,

activities, services, content providers and broadcast receivers. In the present application the

most widely used components are activities, which are practically single screens with user

interfaces.

Activities are activated by Intents, which are created with an Intent object that define what

exact component to activate. Intents in practice are “orders” for an Activity to start. They

may be of two types:

they may start an Activity in a linear manner, or

they may start an Activity only “for a result”, case in which Android will calculate the

necessary result in the opened Activity, and afterwards close it, and return with the

saved value to the primary Activity



64

Every component is declared in the AnddroidManifest.xml file, along with other vital

information regarding the app like permissions. The manifest informs the system about the

components of the application and their capabilities.

Along with the code, an Android application is also composed of additional resources like

pictures, menus and layouts. For every resource included, a unique identifier ID is generated

that can be used for further reference.

The application was developed using Eclipse, which is an integrated development

environment (IDE), seen in Figure 5.2. In this environment the necessary Java code can be

edited, the Android application packages can be compiled, the errors can be debugged and

graphical user interfaces can be built using the .xml language functions. The development

was done mostly using virtual machines, especially a Google Nexus 7 tablet. In present

development only the final stage of handheld device development is made on an actual

device. As it is costly to own and work on parallel on more devices, the concept of virtual

machines is used. Virtual machines allow developers to have any device as a desktop

application that can run the written software. Using this technology the optimization can be

made using a single work-station.

Figure 5.2 The Eclipse development environment



65

5.2 The structure of the application and the navigation possibilities

As it can be seen in the schematic representation of the application in Figure 5.4, the

application has 6 main parts, 6 main functionalities. At the start-up of the application a

welcome screen (marked with “-”) greets the user (Figure 5.3), which disappears after a

couple of seconds. The user gets to the Main menu (“A”), and from there the 6 main

functionalities can be accessed.

Figure 5.3 Start-up screen of the application

The first four possibilities (“1”-“4”) are menu screens that help in the navigation of the

different modules (Knowledge Base Menu, Glass sheet calculation menu (Figure 5.5), Glass

member calculation menu, Product database menu), while the Equivalent beam calculation

(“5”) and the About (“6”) subpart are directly accessible. From the first menu screen (“1”)

the user can enter the 4 main chapters of the Knowledge Base, having the possibility to

freely move through the subchapters (marked with “C”odes, “S”tructures and “M”aterial).

The calculation blocks may be accessed from the menus marked with “2” and “3”. The

calculations and also the Equivalent beam functionality have a Description that can be

entered from each Activity, marked with “D”. The “DIN18008” glass sheet calculation

procedure has a screen to change the predefined values, marked with “c”(hange). The

Database uses classes that are different in type than the previous ones, called Adapters.

These Adapters are used to fill the Database from the data stored in the application

resources. The Adapters are marked with an orange triangle. The Activity of the About

functionality is marked with “6”.

StructuralGlass



66

Figure 5.4 Schematic representation of the application

For navigation purposes it is important to mention the concept of depth. The Main menu

(“A”) is considered as Depth 0, the submenus (1-4), the Equivalent beam and the About

Depth 1, and the “blocks” of the application marked with different colours and marked from

1 to 4 as Depth 2.

When designing the navigation possibilities two main concepts were kept in sight. The

navigation should be fast, a user should not have to go back to the main menu to access

another main functionality, but also, subparts that do not have logical connection between

them should not be connected. There are in total three possibilities to move inside the

application. The Android device has a “Back” button, and by pressing it practically the

Activity will be terminated and the application will “go up” one depth level. By clicking a

button on the main screen the application usually enters a deeper level. On the top of the

screen a menu row is placed to offer fast movement possibility. By using this Action bar

(Figure 5.6), the six main functionalities and the main menu can be accessed directly from

every Depth 1 Activity, while for the other Activities the Action bar offers a “back”

functionality, which is (in almost all cases) equivalent to getting to a sub-menu Activity from

where fast navigation is already possible.



67

Figure 5.5 The Glass sheet calculation sub-menu

When a button is pressed in the Main menu, the attached onClickListeners start the onClick()

method of the application. Each button has a unique id, which can be used to determine

which new Activity is needed to start.

The code executed when a button is pressed from the menu:

@Override

public void onClick(View v) {

switch (v.getId()) {

case R.id.button1:

Intent a = new Intent(MenuGlassSheet.this,

DINSheet.class);

startActivity(a);

break;

case R.id.button2:

Intent b = new Intent(MenuGlassSheet.this,

AMESheet.class);

startActivity(b);

break;

case R.id.button3:

Intent c = new Intent(MenuGlassSheet.this,

CANSheet.class);

startActivity(c);



68

break;

case R.id.button4:

Intent d = new Intent(MenuGlassSheet.this,

AUSSheet.class);

startActivity(d);

break;

}

}

Figure 5.6 The Action bar for Depth 1 activities

The click on one of the Action bar “menu” elements will trigger a listener that starts the

onOptionsItemSelected() method. The Intents that start the next Activity are activated in

function of the id code of the pressed menu item.

Code detailing the click on one of the Action bar items:

@Override

public boolean onOptionsItemSelected(MenuItem item) {

switch (item.getItemId()) {

case R.id.main_menu_item:

finish();

break;

case R.id.knowledge_base_menu_item:

Intent ourIntent1=new Intent(MenuGlassSheet.this,

MenuKnowledgeBase.class);

startActivity(ourIntent1);

finish();

break;

case R.id.glass_sheet_calculation_menu_item:

// Intent ourIntent2=new Intent(MenuGlassSheet.this,

MenuGlassSheet.class);

// startActivity(ourIntent2);

// finish();

break;

case R.id.glass_member_calculation_menu_item:



69


MenuGlassMemberCalculation.class);


finish();

break;

case R.id.product_database_menu_item:


MenuDatabase.class);


finish();

break;

case R.id.glass_beam_equivalent_menu_item:


Equivalent.class);


finish();

break;

case R.id.about_menu_item:


About.class);


finish();

break;

default:

return super.onOptionsItemSelected(item);

}

return true;

}

The code to create (“inflate”) the elements of the Action bar: @Override

public boolean onCreateOptionsMenu(Menu menu) {

// Get a reference to the MenuInflater

MenuInflater inflater = getMenuInflater();

// Inflate the menu using activity_menu.xml

inflater.inflate(R.menu.main_menu, menu);

inflater.inflate(R.menu.knowledge_base_menu, menu);

inflater.inflate(R.menu.glass_sheet_calculation_menu,

menu);



70

inflater.inflate(R.menu.glass_member_calculation_menu,

menu);

inflater.inflate(R.menu.product_database_menu, menu);

inflater.inflate(R.menu.glass_beam_equivalent_menu,

menu);

inflater.inflate(R.menu.about_menu, menu);

// Return true to display the menu

return true;

}

Figure 5.7 Action bar for the glass sheet calculation blocks

The procedure in case of a single menu item (Figure 5.7) is the same as the case with

multiple selection possibilities. For code robustness measures the switch statement is used

also here.

Code executed on the selection of the one-item Action bar:

@Override

public boolean onOptionsItemSelected(MenuItem item) {

switch (item.getItemId()) {

case R.id.back_to_glass_sheet_calculation_menu_item:

finish();

break;

default:

return super.onOptionsItemSelected(item);

}

return true;

}

The code to create (“inflate”) the one-item Action bar:

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Get a reference to the MenuInflater

MenuInflater inflater = getMenuInflater();

// Inflate the menu using activity_menu.xml



71

inflater.inflate(R.menu.back_to_glass_sheet_calculation_menu, menu);

// Return true to display the menu

return true;

}



72

5.3 Input methods

Android offers various input methods to get information from the users. In the Structural

Glass application mostly Buttons, EditTexts, RadioButtons and RadioGroups are used. When

deciding on the input types, the main consideration is how much freedom the users need for

the input of the data/information.

5.3.1 The Button

Buttons (Figure 5.8) are widely used throughout the application to provide the user

possibilities of navigation and means to signal the end of a computational phase.

Figure 5.8 Button example

The Button is set up in the .xml layout file of the Activity. An Android id is provided for

connection purposes (Activity-layout.xml connection) and the text displayed on the button is

specified.

Defining a button in the layout.xml file:

<Button

android:id="@+id/button1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Button" />

The Button is initialized in the Activity declaring a Button variable and connecting it to the

layout through the button id and casting it to the variable.

Initializing a button in an Activity: Button button1; button1 = (Button) findViewById(R.id.button1);

The text/layout of the Button may be modified programmatically, modifying the text or the

background (this is largely used in the Knowledge Base functionality), but considering also

that major changes (background change) overwrite every graphical setting of the button as it

can be seen in Figure 5.9.



73

Figure 5.9 Background change overwriting the button layout

The Button is provided with an onClickListener which contains the executable code in case of

a button click. The onClickListener can be initialized right after the Button declaration or as a

separate method in which multiple button clicks are handled based on their .xml ids and

using a switch statement.

Example for code being executed after an onClickListener intercepts the button press:

@Override



case R.id.button1:

Intent i = new Intent(DINSheet.this, DINModify.class);

startActivityForResult(i, 0);

break;

case R.id.button2:

result=(float)Math.round(result * 100) / 100;

tvResult.setText(String.valueOf(result)+" MPa");

break;

}

}

5.3.2 The EditText

EditTexts (Figure 5.10) are the basic possibility for users in Android to enter characters.



74

Figure 5.10 EditText example

An EditText is set up in the .xml layout file of the activity and Android ids ensure the Activity-

layout connection. An android:inputType may be used to limit the input possibilities.

Defining an EditText in the layout.xml file:

<EditText

android:id="@+id/editText1"

android:layout_width="match_parent"


android:ems="10"

android:inputType="numberDecimal" >

</EditText>

The EditText is initialized from the Activity declaring an EditText variable and referring the

layout id of the widget, casting it inside the variable.

Initializing an EditText in an Activity: EditText et1;

et1 = (EditText) findViewById(R.id.editText1);

If no restrictions are made, any input can be provided to an EditText. After the input, the

information has to be interpreted, where the permissive input methodology generates

verification tasks. The interpretation of the information consists of checking the input for

validity, and the transferring to a variable that can be easily used further in calculation

procedures.

The processing of the information may begin by the application of listeners (for example

TextChangedListener) for a “live” interpretation procedure, or by connecting the EditText

input interpretation with a button click. As it is unnecessary to recalculate everything once a

character is entered, this second method is used through the application. Most often a

“Calculate” button is placed after the input block and the button’s onClickListener triggers

the interpretation step.

Information gathering from an EditText on the click of a button:

@Override



case R.id.button1:

a = Double.parseDouble(et1.getText().toString());



75

break;

}

}

When setting up the EditText the android:inputType=”” gives the possibility to calibrate the

pop-up keyboard type, the representation of the input text (normal/password format) and

can prevent the user from entering unsupported characters. If the term

android:inputType=”number” is used in the .xml initialization, only number input is enabled

in the EditText. If the term android:inputType=”numberDecimal” is used in the .xml

initialization, the user may only enter numbers and a decimal point.

The validity check of the information is necessary because errors may occur in further

phases if the type of the input does not fit inside a desired variable. Android, and inside

Android, the Java programming language uses different variable types to store data. If no

restrictions are specified, the data collected from an EditText is a String. A String variable

can contain any sequence of characters, but mathematical operations will not be possible. In

the next step, the String is transferred to a number format to enable calculation. Usually the

number types have upper and lower boundaries and also other restrictions. Integers for

example cannot contain decimal numbers, while doubles may store decimals, but will not be

able to interpret a String like “.12” as a number.

The information from the EditText is checked and is passed through casting (forceful

transferring) to a variable that can be used for further calculation processes.

Casting (to Integer or to Double) of the information gathered from the EditTexts:

a = Integer.parseInt(et1.getText().toString());

b = Double.parseDouble(et2.getText().toString());

5.3.3 RadioButtons and RadioGroups

RadioButtons (Figure 5.11) are checkable buttons which are usually grouped together to

form a RadioGroup (Figure 5.12). In a RadioGroup only one RadioButton can be checked at

one time.

Figure 5.11 RadioButton example



76

Figure 5.12 RadioGroup example

Once a different selection is made, the previous selection is unchecked. The RadioButtons

are linked together with a fixed input, practically limiting the input from the user to options

provided by the RadioButtons. They are very useful in case of design codes, because design

codes often provide choice possibilities where the user has to specify a selection and then

continue the calculation further using that selection, as seen in Figure 5.13.

Figure 5.13 Example for design code possibilities

The RadioButtons/RadioGroups are set up in the .xlm layout file. Android ids are provided to

both types. RadioButtons are provided with text linking them to choices and it is possible to

introduce a default checked RadioButton to ensure that on the Activity sheet one choice is

always selected. This methodology is used in the application to prevent “no selection” type

errors. The Activity declares the RadioButton and RadioGroup variables for further use and

casts the xml widgets inside the variables using the ids.

Defining a RadioGroup in the layout.xml file:

<RadioGroup

android:id="@+id/radioGroup2"


android:layout_height="wrap_content" >

<RadioButton

android:id="@+id/radio21"



android:checked="true"

android:text="Annealed" />

<RadioButton






77

android:text="Heat strengthened" />

<RadioButton




android:text="Fully tempered" />

</RadioGroup>

Initializing of RadioButtons and initializing and setting of a listener to a RadioGroup in an Activity: RadioButton choice11, choice12, choice13;

RadioGroup radiog1;

choice11 = (RadioButton) findViewById(R.id.radio11);



radiog1 = (RadioGroup) findViewById(R.id.radioGroup1);

radiog1.setOnCheckedChangeListener(this);

The state change of the RadioButtons can be monitored by onCheckedChangeListeners, but

in this application RadioButtons are always grouped inside RadioGroups and the

RadioGroup’s onCheckedChangeListener is used to monitor the changes. The changes can be

easily managed using a switch statement, where based on the ids of the RadioButtons,

different code snippets can be run.

Example of code executed in case of a change in a RadioGroup selection:

@Override

public void onCheckedChanged(RadioGroup group, int checkedId) {

switch (group.getCheckedRadioButtonId()) {

case R.id.radio11:

c1 = 2.5;

break;

case R.id.radio12:

c1 = 3.00;

break;

case R.id.radio13:

c1 = 4.00;

break;

}

}

5.4 Output methods



78

Through the application several, mostly basic output methods are used to get information to

the user. In Android the information displayed on the screen is most often contained in

layout.xml files. The layouts are inflated mostly at the start of the Activity lifecycle, in the

onCreate() method (Figure 5.14).

Figure 5.14 Android Activity Lifecycle, source: http://www.android-app-market.com/wp-

content/uploads/2012/03/Android-Activity-Lifecycle.png

The most usual layout types are linear layouts and relative layouts. In case of a rather fix

structure, where the main purpose is to offer information, the linear layouts are an

advantageous solution. In the Structural Glass application various Linear Layouts are mostly

used.



79

5.4.1 Linear Layouts and Scrollview

One of a linearlayout’s most important properties is its orientation. The orientation may be

horizontal or vertical. Various outlooks can be obtained by combining the different

linearlayouts, and by inserting layouts inside the layouts (Figure 5.15).

Figure 5.15 Combination possibilities of the Linear layout

Layouts (and also other View objects in Android) have several width/height setting

possibilities. They may fill all the space that is provided (“match_parent”), they may only

wrap their own contents (“wrap_content”), or they may be given a specified value for

height/width. The possible settings can be visualised in Figure 5.16.

Figure 5.16 Width/height possibilities

In case of multiple layouts inside an outer layout, a ration can be given to specify how much

each of the layouts should take from the available space. In this case the outer layout’s

android:weightSum is specified, and to each child-layout an amount of this weightSum is

given through the android:layout_weight. Layouts can also have additional options like



80

padding and gravity or backgroundcolorspecified. An example for the use of these

characteristics can be seen in Figure 5.17.

Figure 5.17 Example for the use of the "weight" and "background" characteristics

The layout.xml representation of the above example:

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"


android:layout_height="match_parent"

android:orientation="horizontal"

android:weightSum="100">

<LinearLayout



android:orientation="vertical"

android:layout_weight="50"

android:background="@android:color/white">

</LinearLayout>

<LinearLayout



android:orientation="vertical"

android:layout_weight="50"

android:background="@android:color/black" >

</LinearLayout>

</LinearLayout>



81

An additional possibility is introducing layouts inside a scrollview. By doing this, the inside

layout will be scrollable. In case of layouts that exceed the screen size, this is one of the

possibilities to show all the contents.

Example for a Scrollview inside a layout.xml file:

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="wrap_content">

<LinearLayout



android:orientation="horizontal"

android:weightSum="100">

</LinearLayout>

</ScrollView>

5.4.2 The TextView

TextViews are the most basic output possibilities inside Android. The TextView widget offers

the possibility to represent text with a relatively low amount of formatting. In the Structural

Glass application they are used in almost every simple output process.

Defining a TextView in the layout.xml file:

<TextView

android:id="@+id/textView1"



android:text="TextView" />

Using their TexView.setText() method, they can be easily used to present results.

Android has limited formatting possibilities, underlining not being a predefined possibility.

To use underlined titles as in Figure 5.18, an additional .class was downloaded and an extra

.xml snippet was used for every underlined title.

Figure 5.18 Example for underlining

Representation in the layout.xml file of the above example:

<com.structural.glass.UnderlineTextView



android:gravity="left"

android:text="GLASS BALUSTRADE"



82

android:textSize="18sp"

android:textStyle="bold"/>

One interesting setting of a TextView (and also other View objects) is the visibility. The

android:visibility=”” may be equal to “visible”, “invisible” or “gone” (Figure 5.19), the

difference between the last two being that in “invisible” state the object still uses the space

that is assigned to it. The visibility state can be programmatically changed during the run of

the application (Figure 5.20).

Figure 5.19 Example for EditText with visibility "gone"

Figure 5.20 Example for EditText with visibility set programatically to "visible"

In the application, in various cases (but most often when displaying results) this possibility is

used to show results only after the calculation process, but on the same layout as the input.

In these cases the “Calculate” button’s onClickListener triggers the change in the views,

generating the appearance and practically enlarging the visible layout (Figure 5.21).

Figure 5.21 "Enlargement" of the visible layout on results generating



83

The calculated results store as many decimals of the result as their variable type permits. As

the representation of the results usually does not require more than two decimals, the

results need to be rounded up to have an adequate representation form. This is done prior

to setting the result inside the TextView.

Rounding up and displaying only two decimals:

deflection=(double)Math.round(deflection * 100) / 100;

5.4.3 The WebView

A WebView is mostly used to show web content, but in the present application it is widely

used, mostly in the Knowledge Base instead of TextViews. The reason for this is the fact that

Android does not have justification implemented for TextViews. To obtain a justified text, a

WebView (set up in the layout.xml file) is needed which is after filled with text, and extra

formatting code make text justification possible.

Defining a WebView in the layout.xml file:

<WebView

android:id="@+id/dp1"

android:layout_width="825dp"


android:gravity="left"/>

Initialization of a WebView in the Activity:

WebView viewdp1 = (WebView) findViewById(R.id.dp1);

<string name="string_dp11">

<![CDATA[<html><body><p align=\"justify\">

...

</p></body></html>

]]>

</string>

viewdp1.loadData(textdp11, "text/html", "utf-8");

5.4.4 Images and Description

Images are often additional sources of information, like in Figure 5.22. They are used widely

in the Knowledge Base, but they have the most important task in the glass member

calculation procedures, where they illustrate the variables used and their meaning.



84

Figure 5.22 Example for images used to display information related to the notation

Images are usually represented in Android by ImageView elements in the layout, specifying

the size of the image, the identification element of the image (android:src), and sometimes

also a scaling type. Images are copied and stored inside the res/drawable directory of the

application folder.

Defining a ImageView in the layout.xml file:

<ImageView

android:id="@+id/imageView37"

android:layout_gravity="center"

android:gravity="center"

android:src="@drawable/kb_design_1"

android:layout_width="500dp"

android:layout_height="250dp"

android:scaleType="centerInside" />"

5.4.5 Emailing the results

At the end of each glass sheet and glass member calculation module it is possible to send the

results by email. If the button is clicked, the onClickListener composes the email message,

which will include the variable selections made by the user, and the final result. The Activity

will start an Intent that will search for installed email-sender applications and load a new

message. The subject of the email is set to “Structural Glass-*Name of the module+”, while

the recipients line will be left blank.

Emailing the results in case of a button click:

case R.id.button3:



85

String emailaddress[] = { " " };

String message = " Type of glass: "

+ type

+ " Position "

+ position

+ " Duration of load: "

+ duration

+ " Glass sheet supported on: "

+ support

+ " Part of laminated sheet: "

+ laminated

+ " Resistance of glass sheet according to

DIN18008"

+ '\n' + result;

Intent emailIntent =new

Intent(android.content.Intent.ACTION_SEND);

emailIntent.putExtra(android.content.Intent.EXTRA_EMAIL,

emailaddress);

emailIntent.putExtra(android.content.Intent.EXTRA_SUBJECT,

"Structural glass-Glass sheet DIN18008");

emailIntent.setType("plain/text");

emailIntent.putExtra(android.content.Intent.EXTRA_TEXT, message);

startActivity(emailIntent);

break;

5.4.6 Description of a calculation block

The calculation modules of the application have a description accessible through a button at

the top of the layout (Figure 5.23) that offers information and extra details related to the

calculation procedure. In some of the calculation blocks simplifications are made to make

the result calculation possible on the Android platform. The simplifications and additional

design step information can be found in the detailed description shown in Figure 5.24.

Figure 5.23 DIN18008 Glass sheet calculation, Description button on the top of the layout

Another provided functionality is the list of the links that connect to the related topics of the

Knowledge Base. The Descriptions are important connection elements that are helping the



86

user navigate from a design situation to the pre-design guiding tool function of the

Knowledge base.

Figure 5.24 The Description screen of the DIN18008 Glass sheet calculation

5.5 The Knowledge Base

The Knowledge base (Figure 5.25) has a double functionality. It offers a brief overview of the

important knowledge related to glass that could be useful in the pocket of a structural

engineer, and offers a significant amount of the knowledge needed to understand the

concepts of structural glass design. In the same time, the Knowledge Base acts as a pre-

design guiding tool, as it helps with early stage decision making, product- and approach

selection. It is tightly linked to the calculation functionalities of the application, as, in case of

every glass sheet calculation procedure or complex calculation block, the Description offers

the related Knowledge Base topics that should be studied for a better understanding.

The structure of the Knowledge Base consists of two levels to help in a quick search for

information. The topics are grouped together following the general overview, material,

structure, and design procedures blocks. These blocks represent the upper level of the of a

search procedure. In case of information search, the subchapters, representing the second

level can be accessed for the needed details.



87

Figure 5.25 The Knowledge base outline inside the application

For a quick access possibility and to ensure an elevated mobility, main functionalities

(chapters) are made accessible on the top of the view area, while the subchapters for each

chapter are made accessible and listed on the left side for fast navigation, as shown in Figure

5.26.

Figure 5.26 Structure of the Knowledge base

Major chapters of the Knowledge Base:



88

Use of structural glass in civil engineering - offers a general overview containing

production numbers and a brief summary of why the role of structural glass design is

increasing

Material and technology - groups together subchapters that treat the glass as a

material that can be influenced by various procedures. The Glass and Float glass

subchapters summarize the general characteristics of the material, and the

production procedure. The next four subchapters, The heat tempering process, Fully

tempered glass, Heat strengthened glass and Chemical tempering treat the various

toughening procedures available for glass tempering.

Glass used in structural systems - groups the major element types that are made of

glass, consisting of five subchapters, treating glass beams, columns, slabs, walls and

connections

Design procedure for structural glass - consists of four subchapters, each subchapter

detailing a glass design code. The design codes taken into consideration are the

American E1300-12a, the German DIN18008, the Canadian CAN/CGSB-12.20 and the

Australian AS 1288-2006.

Figure 5.27 The system of the linear layouts inside the Knowledge base

To obtain the structure designed a system of linear layouts are used. The desired solution

can be obtained by the combination of horizontal and vertical linear layouts in a

combination shown in Figure 5.27. The linear layouts 2 and 4 hold the buttons that help in

the navigation between the chapters and the subchapters. The orientation of the layout fixes

the appearance of the buttons. In the horizontal layout (2) the chapter titles displayed on

the buttons are distributed horizontally, while in the vertical layout that holds the

subchapters (4) the distribution is vertical. Linear layout (5) is a scrollable layout and it is

used to display information attached to every subchapter.



89

The contents of Knowledge Base are represented by the use of TextViews, ImageViews and

WebViews. The images are scaled to the size of 500dp x 250dp, where dp stands for density-

independent pixels. This representation is useful because the image size is relative to the

actual properties of the used device. TextViews are used for the caption of the images, and

WebViews for the main text parts. WebViews are used because they are able to display

justified text.

Each subchapter is treated in a different activity with a different layout, and the jump

between them in ensured by intents, which open the next desired subchapter, and close the

previous one. For this result, to each button, an onClickListener is attached and through a

switch statement in function of the Id of a specific button, a specific activity is started. The

onClick() method and the inside switch used to start a new Activity in case of a button click:

The onClick() method of the Knowledge Base that initiates the navigation between the

topics:

@Override



case R.id.button1:

finish();

break;

case R.id.button2:

Intent a = new Intent(UseOfStructuralGlass.this,

UseOfStructuralGlass.class);

startActivity(a);

finish();

break;

case R.id.button3:

Intent b = new Intent(UseOfStructuralGlass.this,

MaterialAndTechnology.class);

startActivity(b);

finish();

break;

case R.id.button4:

Intent c = new Intent(UseOfStructuralGlass.this,

GlassInStructuralSystems.class);

startActivity(c);

finish();

break;

case R.id.button5:

Intent d = new Intent(UseOfStructuralGlass.this,

DesignProcedures.class);

startActivity(d);

finish();

break;



90

}

}



91

5.6 Implementation of design codes calculation procedures for glass sheets

5.6.1 Introduction

Glass sheets can be considered as the most basic form of the use of structural glass. The

fabrication procedure results in glass sheets with different characteristics that are later

further processed, and the most basic design procedures offered by the various design codes

are detailing the calculation of simple glass sheets.

Glass sheets are largely used to withstand wind loads. Most of the treated design codes

formulate general recommendations and specific design procedures focusing and limiting

the use of the design code to these types of sheets. Various formulations (charts, tables,

formulas) are used in the design code calculation procedures, to offer support, approaching

glass sheet design from different viewpoints. The final output values differ, as some codes

offer guidance to resistance determination, while others thickness or allowable span.

In the implementation process the steps of the calculation were kept similar to the ones

from the design code, to be of quick help to anyone familiar with the specific code. As part of

this concept, the units of measurement are also identical to the ones used throughout the

official formulations.

The implemented calculation procedures from various design codes:

German DIN18008 – Resistance calculation of a glass sheet

American E1300-12a – Load resistance calculation of a glass sheet

Canadian CAN/CGBS1220 – Determination of the factored load, Calculation of the minimum necessary thickness of a glass sheet, Deflection calculation

Australian AS1288-2006 – Determination of the maximum allowable span

5.6.2 German DIN18008

In case of every glass sheet calculation process, the first dominant task is the receiving and

managing of the input data. According to the DIN18008 design code five factors and their

combination can influence the resistance of a glass sheet. The input procedure, as shown in

the user interface representation in Figure 5.28 is implemented through simple radiogroup-

type input. This type of input offers the possibility to choose from a list of options, in a way

that only one choice can be selected at a specific time.



92

Figure 5.28 The DINSheet Activity

The type of glass (float, fully tempered, heat treated, cast glass, fully tempered enameled

glass, partially tempered enameled glass) is influential mostly at the level of the basic

strength, but is also important in some special cases. The German design codes offer

predefined resistance values for different types of glass, detailed in Table 5-1.

Table 5-1Glass resistance values according to German design codes

Float glass 45 MPa

Fully tempered glass 120 MPa

Heat treated glass 70 MPa

Cast glass 25 MPa

Fully tempered enameled glass 75 MPa

Partially tempered enameled glass 45 MPa

The inclination of the glass sheet can be taken as vertical (inclination≤10◦) or horizontal

(inclination≥10◦).



93

Figure 5.29 Input of glass type (right) and input of glass sheet inclination (right)

The duration of load may vary between short (ex. wind), medium (ex. snow) or long (ex. self-

weight). The two support conditions defined in the design code are two sided support and

four sided support. The calculation procedure is a little different in case of a glass sheet that

is part of a laminate. This information is also necessary for a full calculation procedure.

Figure 5.30 Input of the shortest load duration (left), support conditions (centre) and lamination information (right)

The calculation procedure is divided in calculation blocks, as the resistance of the glass sheet

is in function of six factors (Figure 5.31). Every factor is calculated individually in a calculation

block, and each block can be considered a function:

The first block calculates the characteristic resistance fk in function of the glass type.

The second block is used to determine the construction type factor which is 1.8 in

case of glass without tempering that is in a vertical position and is supported on four

sides, and equal to 1 otherwise.

The third function returns the duration modification factor in function of the shortest

load duration.

The fourth function returns a factor for taking only 80% of the resistance for glass

sheet without tempering that are supported on two sides and thus are loaded on the

edges.

The fifth function enables a 10% increase in strength for glass sheets that are part of

a laminated sheet.



94

The sixth function returns the material safety factor, which is 1.8 for glass without

tempering and 1.5 otherwise.

Figure 5.31 Calculation blocks (functions) for DIN18008

The final result can be obtained by multiplying the resulting first five factors and then

dividing with the material safety factor.

To enable particular cases, an overwrite possibility is implemented for the predefined

characteristic glass resistance values. The values can be changed and the calculations can be

continued with modified values.

For further use of the calculation details, at the end of each glass sheet calculation it is

possible to send the details of the calculations by email.

The implementation of the German DIN18008 glass sheet calculation for an Android consists

of an interactive input screen, a predefined value modification screen, and a “Description”

page. The input is obtained by the means of RadioGroups, which make possible to select one

RadioButton from every RadioGroup.

In the calculation process every factor that influences the result is calculated in a different

function/method. The methods use the variables introduced through the RadioGroups to

calculate the values.

The functions/methods used for result calculation inside the DINSheet activity:

fk=resistance(type);

constructiontype=construction(type, position, support);

durationmodfaktor=durationmod(type, duration);

edgefaktor=edge(type, support);

lam=lamin(laminated);



95

safety=safetyfaktor(type);

result=fk*constructiontype*edgefaktor*lam/safety;


The application offers the possibility to change the predefined resistance values offered by

the various German design codes. If the user wants to change the values, an Intent is started

through the startActivityForResult() method, because the change is taking place in a

separate Activity.

The startActivityForResult() method:

Intent i = new Intent(DINSheet.this, DINModify.class);

startActivityForResult(i, 0);

The input of the new predefined values is achieved through invisible EditTexts that are

visible only when the user clicks to make the change. These EditTexts will collect the changes

and send back the results (Figure 5.32).

Figure 5.32 Modification of the predefined values

Sending the modified predefined values through a Bundle:

Intent sendIntent= new Intent();

Bundle basket = new Bundle();

basket.putInt("a", a);

basket.putInt("b", b);

basket.putInt("c", c);

basket.putInt("d", d);

basket.putInt("e", e);

basket.putInt("f", f);



96

sendIntent.putExtras(basket);

setResult(RESULT_OK, sendIntent);

finish();

The results are interpreted by the DINSheet main Activity and the final results are

recalculated and displayed.

Gathering of the information from the Bundle and recalculating the results:

@Override

protected void onActivityResult(int requestCode, int resultCode, Intent

data) {

super.onActivityResult(requestCode, resultCode, data);

if (resultCode == RESULT_OK){

Bundle gotBasket = data.getExtras();

a=gotBasket.getInt("a");

b=gotBasket.getInt("b");

c=gotBasket.getInt("c");

d=gotBasket.getInt("d");

e=gotBasket.getInt("e");

f=gotBasket.getInt("f");

fk=resistance(type);

constructiontype=construction(type, position, support);

durationmodfaktor=durationmod(type, duration);

edgefaktor=edge(type, support);

lam=lamin(laminated);

safety=safetyfaktor(type);

result=fk*constructiontype*edgefaktor*lam/safety;


}

}

5.6.3 American E1300-12a

The application subpart implements the load resistance calculation of the American E1300-

12a. The calculation is based on charts that help the user to find the non-factored load (NFL)

and afterwards multiply it by different coefficients that take into consideration the type of

the glass and the duration of the load.



97

Figure 5.33 The interface of the American E1300-12a sheet calculation

An input process, show in the user interface in Figure 5.33 is required to gather the

information from the user. The gathered information (sheet dimensions, support conditions)

is used to select the appropriate design chart and to obtain the non-factored load from it.

The E1300-12a does not provide the equations from which the charts were created, and the

lines cannot be considered as functions. The adequate chart is selected based on the

thickness of the glass sheet. The two major dimensions of the sheet are used to define a

point in the chart. The point is united with the (0,0) point of the chart by a line and the

segment that contains the point and is limited by the neighboring lines is used to interpolate

and get the final non-factored load as shown in Figure 5.34.



98

Figure 5.34 Example for the graphical procedure in a design chart

The rest of the input values are used to calibrate this non-factored load. The output of the

algorithm is the load resistance (LR) of the glass sheet, which is the uniform lateral load that

a glass construction can sustain based upon a given probability of breakage and load

duration.

The input of the user defined values is achieved through the use of EditTexts and

RadioGroups. According to the design code the sheet dimensions are used (particularly the

thickness) to select the chart and calculate through interpolation the value of the non-

factored load.

The charts are transposed into Android environment as tables. The first row and the first

column contain the dimension with steps of 20 centimeters, while the inside of the table

contains the corresponding values. The assumption is made that the linear interpolation is

safe in these 20cm intervals.

Initialization of a chart-equivalent table:

table4sides3 = new double[][] {

{ 0, 200, 400, 600, 800, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600,

2800, 3000 },

{ 200, 0, 15, 10, 10, 10, 10, 10, 10, 10, 10, 0, 0, 0, 0, 0 },

{ 400, 0, 8, 5, 3.9, 3, 2.75, 2.5, 2.5, 2.25, 2.25, 2, 2, 2, 2, 2 },

{ 600, 0, 0, 4, 3.25, 2.55, 2, 1.66, 1.42, 1.22, 1.1, 1, 1, 0.95, 0.9, 0 },



99

{ 800, 0, 0, 0, 2.65, 2.34, 1.9, 1.6, 1.45, 1.2, 1, 0.93, 0.78, 0.5, 0.5, 0.5 },

{ 1000, 0, 0, 0, 0, 1.9, 1.6, 1.4, 1.25, 1.15, 1.02, 0.95, 0.8, 0.72, 0.5, 0.5 },

{ 1200, 0, 0, 0, 0, 0, 1.37, 1.21, 1.05, 0.98, 0.87, 0.8, 0.75, 0.6, 0.5, 0.5 },

{ 1400, 0, 0, 0, 0, 0, 0, 1, 0.95, 0.8, 0.75, 0.72, 0.7, 0.65, 0.55, 0.5 },

{ 1600, 0, 0, 0, 0, 0, 0, 0, 0.75, 0.73, 0.7, 0.62, 0.6, 0.55, 0.5, 0.5 } };

The application first checks if the introduced values match exactly the length values in the

table, and if not, through interpolation the final non-factored loads are calculated. If the

introduced values are too small/too big and outside the limits of the table, the user will get a

warning message about it, and will be advised to consult the design code.

The calculation of the non-factored load:

private double calculateNonFactoredLoad(double a, double b, double[][] table) {

double value = 0;

double y1, y2, x11, x12, x21, x22;

i = 1;

j = 1;

while (table[0][i] < a) {

i++;

}

while (table[j][0] < b) {

j++;

}

x11 = table[j - 1][i - 1];

x12 = table[j - 1][i];

x21 = table[j][i - 1];

x22 = table[j][i];

int compare1 = Double.compare(table[0][i], a);

int compare2 = Double.compare(table[j][0], b);

if ((compare1 == 0) && (compare2 == 0) && (table[j][i] != 0)) {

value = table[j][i];

} else {

if ((x11 != 0) && (x12 != 0) && (x21 != 0) && (x22 != 0)) {

y1 = interpolate(table[j - 1][0], table[j][0], x11, x21, b);

y2 = interpolate(table[j - 1][0], table[j][0], x12, x22, b);

value = interpolate(table[0][i - 1], table[0][i], y1, y2, a);

} else {

value = 0;

}

}

;



100

return value;

}

The interpolate() method used in the linear-interpolation: private double interpolate(double a1, double a2, double x1, double x2,

double a) {

double value = 0;

if (x2 > x1) {

value = x1 + (x2 - x1) * (a - a1) / (a2 - a1);

} else {

value = x2 + (x1 - x2) * (a2 - a) / (a2 - a1);

}

return value;

}

As Double values cannot be easily compared (the representation in the memory may be

different, while the values might be almost exactly the same), the compare() method is used

for a correct comparison.

Finally, the non-factored load is multiplied by the other factors, rounded up and displayed in

a result-TextView.

5.6.4 Canadian CAN/CGBS1220

The Minimum thickness of a glass sheet (Canadian CAN/CGBS1220) consists of a three step

calculation procedure, where at every step the user has to input new variables to complete

the calculation:

In the first phase the factored load is calculated. The user introduces the selected

non-factored loads, which is then multiplied by the safety factors and combined

using the necessary combining factors.

In the second phase, the characteristics of the glass sheet are entered, the type of

glass, the type of heat treatment, and the load duration. The formulas presented in

the design code are used to calculate the minimum necessary thickness.

In the third phase of the calculation, the non-factored loads and a final user selected

thickness are used to calculate the deflection under the specified characteristics.



101

Figure 5.35 Glass sheet calculation (Canadian CAN/CGBS1220)

The implementation of the Canadian sheet calculation procedure into Android is largely

based on three repeating steps of input-calculation-output. The repetitions are divided by

button clicks, as the onClickListener() and onClick() methods ensure the calculation after

each step.

The design code formulas and conditions are implemented inside the code, using the Math

class to calculate logarithms and to raise numbers to a specific power.

Thickness and deflection calculation:

case R.id.button1:

a=Integer.parseInt(et5.getText().toString());

b=Integer.parseInt(et6.getText().toString());

unfLoad=d+l+q+t;

typeOfGlass=type(c1);

heatTreatment=heat(c2);

loadDuration=load(c1, c3);

c=typeOfGlass*heatTreatment*loadDuration;

h1= (4.87f*Math.pow((a/1000), 0.96)*Math.pow((b/1000),

0.22)*Math.pow(fLoad/c, 0.545));

h2= (2.33f*Math.pow((a/1000)*(b/1000), 0.665)*Math.pow(fLoad/c,

0.87)-1.62*((a/1000)/(b/1000))+1.2);



102

h3= (6.2f*Math.pow((a/1000), 1.15)*Math.pow(fLoad/c, 0.5));

if (a/b>5) {

resultThickness=h3;

} else {

if (h1<h2) {

resultThickness=h1;

} else {

resultThickness=h2;

}

}

resultThickness=(double)Math.round(resultThickness * 100) / 100;

tvMinThickness.setText(String.valueOf(resultThickness)+ " mm");

break;

case R.id.button2:

thickness =

Integer.parseInt(etFinalThickness.getText().toString());

e=70000000;

r0 = 0.553 - 3.83 * (a / b) + 1.11 * Math.pow((a / b), 2) -

0.0969

* Math.pow((a / b), 3);

r1 = -2.29 + 5.83 * (a / b) -2.17 * Math.pow((a / b), 2)

+0.20678

* Math.pow((a / b), 3);

r2 = 1.485 - 1.908 * (a / b) + 0.815 * Math.pow((a / b), 2) -

0.0822

* Math.pow((a / b), 3);

x=Math.log(Math.log(unfLoad*Math.pow(a*b,

2)/(e*Math.pow(thickness, 4))));

w=thickness*Math.exp(r0+r1*x+r2*Math.pow(x, 2));

w=(double)Math.round(w * 100) / 100;

tvDeflection.setText(Double.toString(w)+" mm");

break;

5.6.5 Australian AS1288-2006

The allowable maximum span determination according to the Australian AS1288-2006

(Figure 5.36) consists of an input step from the user (glass sheet dimensions, glass type and

ultimate limit state design wind pressure) and a calculation step that uses the formula

provided by the design code that implements the constants stored in the design code tables.



103

Figure 5.36 Glass sheet calculation (Australian AS1288-2006)

The table is chosen in function of the thickness and the type of glass. The formula uses the

specific constants and the wind pressure to calculate the maximum allowable span, .

The input step of the algorithm is achieved with EditTexts and RadioGroups, mentioning that

the design code offers calculation procedures for different types of glass and different

thicknesses.

The type of the glass decides what thicknesses can be taken into account. The application

handles this step with RadioGroups that are set to “gone” as the default visibility value. Only

the RadioGroup with the thickness belonging to the selected type is displayed. If the type

selection is changed, the corresponding new RadioGroup will appear.

The tables in the design code specify constants that depend on the aspect ratio, and linear

interpolation is allowed between two consecutive values. The application has every table

implemented, with two-dimensional arrays that have on the first line the aspect ratios, and

below the values of the constants.

Initialization of tables based on the constant values specified in the design code:

private void initializetables() {

tableA03 = new double[][] {

{ 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 5, 10 },

{ 1558.4, 1373.2, 1313.4, 1343.4, 1381.9, 1184.5, 667.6,

655.7,

585.6 },

{ 0.25, 0.2, 0.2, 0.3, 0.4, 0.3, -0.3, 0, 0 },

{ -0.6124, -0.6071, -0.6423, -0.7112, -0.7642, -0.7255,

-0.4881, -0.5, -0.5 },

{ 4.2, -1.4, -22.68, -12.6, -11.2, 2.8, -8.4, 0, 0 } };



104

...}

The implemented algorithm interpolates (based on the aspect ratio) in the table, gathers the

values of the constants and calculates the allowable maximum span for the specific glass

sheet according to the formula given by the design code.

The determination of the maximum allowed span:

private double maxSpan(double d, double p2, double[][] table) {

double value = 0;

double a1, a2, a, k1, k2, k3, k4;

int i=0;

while (table[0][i]>d) {

i++;

}

a1=table[0][i];

a2=table[0][i+1];

a=d;

k1=interpolate(a1, a2, table[1][i], table[1][i+1], a);




value=k1*Math.pow(p2+k2, k3)+k4;

return value;

}



105

5.7 Calculation blocks

5.7.1 Introduction

The glass member calculation blocks represent one of the core functionalities offered by the

application. Glass as a structural material is used to offer solutions to various design

problems. The design problems depend on the ideas proposed by the architects, and may

change over time, new solutions may get more importance in upcoming projects.

The calculation blocks offer an overview possibility of a design topic, making possible “live”

calculation and results interpretation. Dimensions and additional design input data can be

changed instantaneously for a quick comparison process. The Android implementation

process and the design problem overview is offered in the Description of every calculation

block to help in an eventual further calculations.

Calculation blocks may be combined between each other and with the glass sheet

calculation procedures to offer complex use possibilities.

The implemented glass member calculation blocks:

Design of a glass fin – Stress calculation and the approach of the lateral-torsional

buckling

Design of a glass T-beam – Determination of the stresses at the extremities and at

the adhesive layer

Design of a hybrid beam – Determination of the stresses in case of a glass web-steel

flanges hybrid beam

Design of a glass balustrade – Stress and deflection calculation for a glass balustrade

5.7.2 Design of a glass fin

The calculation block calculates a glass fin, shown in Figure 5.37, which is connected by

continuous silicone seals to a facade, and withstands the distributed (wind) load from the

facade and the self-weight plus an additional weight a user may consider. The structural

scheme is simply supported. It is assumed that for short term wind loads the silicone

provides continuous connection to the facade, but it is flexible enough not to allow the

appearance of a T-beam effect.



106

Figure 5.37 Visual representation of glass fin design concept

In the first step, the dimensions of the fin, the span/distance between two adjacent fins, and

the wind pressure is specified. Additionally, the user can specify additional weight on one fin,

not considering self-weight. In the second step, the bending moment, the axial load, and the

geometrical properties are calculated. Finally the short term and long term tension and

compression values are calculated and displayed, along with the deflection.

Based on the Appendix C of the Australian AS1288-2006, the application also calculates the

critical bending moment.

After the calculation of the input data, the calculation processes run in four different

methods, after which the results are shown in TextViews (Figure 5.38).



107

Figure 5.38 Glass member calculation-glass fin

According to the Australian AS1288-2006, the design moment for a particular structural

situation should not exceed the critical elastic buckling moment (Mcr) divided by a factor of

safety of 1.7. The application displays also this value for a quick comparison possibility.

When displaying this information, a warning message is additionally displayed, raising

awareness, that the approach used in AS1288-2006 for the critical moment calculation may

be too optimistic in some situations.

“Toast” output message to the user at the end of the calculation process:

Toast.makeText(getApplicationContext(), "Consider also the use of Ayrton-Perry

method (Eurocode) for " +

"the final critical moment calculation and design, as

the approach in AS1288 used in this " +

"preliminary calculation may be too optimistic in some

situations.",

Toast.LENGTH_LONG).show();

}

As well, the value of length/500 is displayed for the possibility of comparison with the actual

deflection.



108

5.7.3 Design of a glass T-beam

The module gives the possibility to calculate a simply supported glass T-beam, considering a

rigid connection between the web and the top. (A rigid adhesive should be considered in an

eventual further stage.) The user can specify the span, the four characteristic dimensions of

the beam section, and the load which may be a uniform distributed load and/or a

concentrated load at the middle of the span (Figure 5.39).

Figure 5.39 Glass member calculation-glass T-beam

The application calculates the maximum bending moment and shear, and from those values

the maximal stress at the tension and compression fiber. The shear stress in the adhesive is

layer is also calculated, offering an important piece of information regarding the useable

glue types.

The lateral-torsional buckling is not considered in the calculation.

In the first step, the user input is gathered and the load is updated with the self-weight of

the T-beam.

The stresses are calculated in separate methods and the result TextViews are updated with

the resulting stresses.

Main methods used in the fin calculation:




109

span = Double.parseDouble(et1.getText().toString());

b = Double.parseDouble(et2.getText().toString());

t = Double.parseDouble(et3.getText().toString());

h = Double.parseDouble(et4.getText().toString());

w = Double.parseDouble(et5.getText().toString());

qLoad = Double.parseDouble(et6.getText().toString());

p = Double.parseDouble(et7.getText().toString());

geometry();

qSelfWeight=a/1000000.00*25;

qTotal=qLoad+qSelfWeight;

forces();

sigmaT();

sigmaC();

taoShear();

tv1.setVisibility(View.VISIBLE);

bendingMoment=(double)Math.round(bendingMoment * 100) / 100;

tv2.setText(String.valueOf(bendingMoment)+" kNm");

tv2.setVisibility(View.VISIBLE);

...}



110

5.7.4 Design of a hybrid beam

The module calculates a simply supported hybrid steel-glass beam, with steel flanges and

glass web, and uses the user input obtained through the interface presented in Figure 5.40

that specifies the geometrical characteristics of the beam (span, cross-section dimensions),

the loads (uniform distributed load, concentrated load in the middle), and the properties of

the glue. The steel grade is considered S235. The calculation procedure does not take into

consideration lateral-torsional buckling.

Figure 5.40 Glass member calculation-hybrid beam

The calculation process consists of the load determination (the user specified load is

updated with the self-weight), the calculation of the internal forces (bending moment and

shear) and the average stiffness and efficiency factor calculation for the connection between

the two materials. The effective moment of inertia is calculated for the section, and the

stresses (stress on the glass edge, stress on the steel edge, shear stress in the glued

connection) are calculated, along with the vertical deformation.

After the collection of data from the EditTexts, the data is processed in separate methods.



111

5.7.5 Design of a glass balustrade

The simplified calculation of a glass balustrade consists of stress and deflection calculation

for a glass balustrade with the thickness, balustrade height and uniform lateral distributed

load on the edge specified by the user (Figure 5.41).

Figure 5.41 Glass member calculation-glass balustrade

In the calculation process, 1m of balustrade is considered. The connection is considered fully

fixed. The deflection is calculated based on (20).

(20)

Where:

– deflection

P – load

E – modulus of elasticity

I - moment of inertia

The Android implementation of the glass balustrade calculation module consists of data

collection, results calculation through the use of methods, and display of the results.



112

5.8 The Product database

The database is another core functionality of the StructuralGlass application. The database

offers an overview of the main categories and products related to structural glass (Figure

5.42). The products presented reflect the actual situation of the structural glass market,

including glass sheets and additional materials used in structural glass applications. Each

item has the original, producer provided description, to ensure a direct relation between

user and producer. The database has a tight connection with the Knowledge Base and the

calculation blocks. The exact properties of a desired product, list of available products, even

new technologies can be browsed in a regularly updated Database.

The database is divided into four major categories:

Glass sheets – offers an overview of glass sheet products with various degree of heat

treatment, lamination etc.

Adhesives – presents products used in the construction of glass adhesive joints

Connections – contains mechanical connections that can be found on the market

Decoration glass – presents glass sheets that have a modified aspect (and modified

characteristics)

The categories are reachable from the Database menu. The categories and the inner

structure database are arranged in a way to make further additions and changes

possible. The lateral “sub-category” buttons are not implemented, as the content does

not need it, but they are easily addable, as the presented major categories can be further

divided into subcategories.

The contents are stored inside an inner database, called SQLite database, thus making

possible fast change and update procedures. Databases are structures that usually

change dynamically in a fast-changing environment. The Database needs to be

updateable in future occasions or when running an update.

In commercial software, an Alarm element is usually set that searches for updates

regularly over the internet. The application downloads the update package,

decompresses, and makes the prescribed changes.



113

Figure 5.42 Product database category overview

After selecting a major category from the menu, the user is taken to the “page”, Activity of

the category, where the products are listed in a scrollable grid, with an image and a title.

When a product is selected, the detailed description of the product appears along with an

enlarged image. The official webpage/company contact information is also displayed.

The design used is very similar to the design used in the Knowledge Base, making possible

fast navigation between the categories using the buttons on the top.



114

Figure 5.43 Product database menu

The grid like appearance is achieved using a GridView in the layout.xml file.

Populating the GridView from the available resources:

@Override

public View getView(int position, View convertView, ViewGroup parent) {

LayoutInflater inflater = (LayoutInflater) mContext

.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

View gridView = (View) convertView;

if (convertView == null) {

gridView = new View(mContext);

gridView = inflater.inflate(R.layout.databaseforimageadapter,

null);

TextView textView = (TextView) gridView

.findViewById(R.id.grid_item_label);

textView.setText(shortDescription[position]);

ImageView imageViewNEW = (ImageView) gridView

.findViewById(R.id.grid_item_image);



115

gridView.setLayoutParams(new

GridView.LayoutParams(GridView.LayoutParams.WRAP_CONTENT,GridView.LayoutParams.WRA

P_CONTENT));

gridView.setPadding(PADDING, PADDING, PADDING, PADDING);

imageViewNEW.setImageResource(mThumbIds.get(position));

}

return gridView;

}

The resources, the images, the titles, and the longer descriptions are stored separately in

arrays, and (in case of images) in the res/drawable folder. The grid is filled at startup using a

BaseAdapter class to adapt the images and the titles and to display them in the same format.

A third Activity is used to display the large image and the description of the product, as

shown in Figure 5.44.

Displaying a specific image based on the information transmitted through an intent:

Intent intent = getIntent();

View largeView = new View(getApplicationContext());

LayoutInflater inflater = (LayoutInflater) this

.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

largeView =

inflater.inflate(R.layout.databaseforlargeimage, null);

Bundle gotBasket = intent.getExtras();

int position=gotBasket.getInt("position");

int image=gotBasket.getInt("image");

textView.setText(longDescription[position]);

imageViewNEW.setImageResource(image);

The official webpage inside the description is displayed in a hyperlink format, meaning that

the user can click on it, and a new WebBrowser application will be opened to display the

link.



116

Figure 5.44 Product database-Detailed representation



117

5.9 The Glass beam equivalent functionality

The Glass beam equivalent functionality makes possible for the user to specify a beam span

and a distributed load and calculate the glass sections that can resist the load, considering

different types of glass beams. The application also calculates the minimum IPE section that

can resist the same load.

The application gives the possibility to introduce the cost of the glass types, the cost of the

lamination interlayer, and the cost of two layer lamination, to compare the height of the

equivalent beams and as well as the cost of each beam. Through this equivalent glass-steel

calculation, the user gets a powerful tool to compete in a market that is mostly dominated

by steel constructions. By examining the relation between the steel and glass sections,

considering also the cost of each glass beam, the user has the possibility to propose near-

optimal equivalence possibilities for design cases, where previously only steel solutions were

considered.

By obtaining both the price and the exact layout of the beams, the user may orient itself

following the minimal price or can consider also other factors. The “live” calculation

interface offers the possibility to update the price-details and to keep account of various

financial factors.

The application takes into consideration 3 types of glass, annealed glass, with a tensile

strength of 45MPa, heat strengthened glass with a tensile strength of 70MPa, and fully

tempered glass with a tensile strength of 120MPa.

The application solves the equivalent glass section problem for glass beams made out of 2, 3

or 4 glass sheets, each sheet with a thickness of 10 mm or 20 mm. The application displays

the minimum beam-height required for each scenario, considering the height between 50

mm and 1000 mm, rounding up the result to an 50 mm round value.

The application assumes simplifications, the thicknesses are fixed and the number of glass

sheets are limited to offer fast calculation results. Also, it does not take lateral-torsional

buckling, or bending moment-shear interaction into consideration.

The first step consists of the user inputting the span of the beam and the distributed linear

load (Figure 5.45). The user can choose to have or not detailed price calculation. In case of

cost calculation, by the change of a RadioButton selection, the EditTexts that gather the cost

calculation details become visible.



118

Figure 5.45 The Glass beam equivalent functionality

The minimum necessary steel section is calculated using a two dimensional array that has

included the characteristics of every IPE beam.

Calculation of the steel section:

private void calculateSteel() {

foundSteel = false;

i=0;

while ((foundSteel == false) && (i<18)) {

bendingMomentSteel=bendingMoment+(tableIPE[1][i]/100.00*Math.pow(span,

2)/8.00)/1000000.00;

shearSteel=shear+tableIPE[1][i]/100.00*span/1000/2;

bendingIPE=235.00*1000*tableIPE[3][i]/1000000.00;

shearIPE=235*tableIPE[2][i]*100/1000.00;

if ((bendingMomentSteel<bendingIPE) && (shearSteel<shearIPE)) {

foundSteel=true;

}

i++;

}



119

For both the steel and the glass section, the distributed load is updated with the self-weight.

For the glass section calculation for every scenario a beam with the height of 50mm is tried

out. If it does not resist, 50mm is added to the height until a valid result is found or the 1000

mm upper limit is reached. The cost is calculated once for every scenario, calculating every

glass type at once.

Calculation of the cost:

private void calculateCost() {

costFullyTempered=Double.parseDouble(etCost1.getText().toString());

costHeatStrengthened=Double.parseDouble(etCost2.getText().toString());

costAnnealed=Double.parseDouble(etCost3.getText().toString());

costInterlayer=Double.parseDouble(etCost4.getText().toString());

costLamination=Double.parseDouble(etCost5.getText().toString());

costMaterialFullyTempered = tGlassSheet/1000.00*numberOfSheets*(j-

50)/1000.00*span/1000*costFullyTempered;

costMaterialHeatStrengthened = tGlassSheet/1000.00*numberOfSheets*(j-

50)/1000.00*span/1000.00*costHeatStrengthened;

costMaterialAnnealed = tGlassSheet/1000.00*numberOfSheets*(j-

50)/1000.00*span/1000.00*costAnnealed;

costMaterialInterlayer = (numberOfSheets-1)*(j-

50)/1000.00*span/1000.00*costInterlayer;

costBeamLamination = (numberOfSheets-1)*costLamination;

costTotalFullyTempered=costMaterialFullyTempered+costMaterialInterlayer+cos

tBeamLamination;

costTotalHeatStrengthened=costMaterialHeatStrengthened+costMaterialInterlay

er+costBeamLamination;

costTotalAnnealed=costMaterialAnnealed+costMaterialInterlayer+costBeamLamin

ation;

costTotalFullyTempered=(double) Math.round(costTotalFullyTempered *

100) / 100;

costTotalHeatStrengthened=(double)

Math.round(costTotalHeatStrengthened * 100) / 100;

costTotalAnnealed=(double) Math.round(costTotalAnnealed * 100) / 100;

}

As a last step, the results are displayed in a table-like format presented in Figure 5.46 to

make the comparison procedure easier.



120

Figure 5.46 Equivalent beam - glass section results

5.10 The About subpart

The About subpart of the application contains general information related to the framework

of development of the application.

It also contains the Disclaimer of the application. Disclaimers are statements denying

responsibility, intended to prevent civil liability and is used in almost every software product.

The reference list and the list of the sources/credits of the figures used in the application can

also be found here.



121

6 Final remarks and future developments

6.1 Final remarks

In the framework of the application, the major topics of structural glass were treated and

various subparts were further developed. The developed application offers calculation

support for glass sheet calculation based on various design codes and other glass member

calculation blocks. A theoretical support for the calculations and various glass related topics

is provided to ensure a better understanding of the applied concepts. A database is provided

to offer an overview of the market related to structural glass design. An equivalent beam

calculation module is presented to offer comparison possibilities between steel beams and

glass beams.

As it has been shown in the previous chapters, in the present there are no applications on

the market that tackle issues related to structural glass. There is a gap in the market that can

be filled with an application that suits the needs of most of the structural glass designers.

This is an interesting fact, as structural glass applications spread more and more. One reason

could be the fact that there is a lack of design codes related to structural glass. A lot of

countries have little to none regulations and the glass Eurocode is expected to be published

only in a couple of years. Given the fact that handheld devices will most certainly remain an

important tool in the future, and considering that there is a continuous technological

improvement in structural glass, such an application (with regular updates that consider the

new design codes) could become a highly used and downloaded application that could even

generate a slight income.

In case of a commercial software, the application-glass companies relationship can also be

further developed to include advertisement or other advantageous solutions for companies

that could generate profit from being included in the application in different ways. If the

application is largely used, this can also be considered as an income source.

The development of the application was done from a European “point of view”. Design

codes from America, Canada and Australia were also taken into consideration, but the main

functionalities, the calculation blocks show the European approach. Given the fact that

foreign design codes use different methods, different approaches, it would be interesting to

consult with people that are used with those design and development environments.

Handheld device applications are considered a global tool, without boundaries. For better

understanding and to provide better support for the users it would be advisable to have the

global overview of all major glass design codes (and the additional core design codes, design

methodologies from the different countries). This goal is not easy to achieve, because the

different design codes are hard to acquire and require a significant amount of money

investment.



122

6.2 Future developments

The developed application can be a useful tool as it is, but further improvements are also

possible to give even higher functionality to the user.

In the development process only a very small accent was put on the graphical design part of

the application. The interface can be made more fluent and user-friendly by building a better

suited design, characteristic to the application. Custom button designs, background-

foreground colour optimization, input and output fluency improvement can be considered

as major design steps to be taken in an eventual further development.

More calculation block scenarios can be implemented through the monitoring of the actual

design needs. The calculation blocks can be grouped together to enable the calculation of a

design scenario of a larger magnitude, constantly being careful not to exceed the optimal

use capacities of a handheld device. In some cases the design codes offer alternatives to

calculate a value. In the application in every such case only one method was implemented

for the calculation procedures, leaving the possibility of the implementation of the nearly

equivalent method for further development.

Other topics may be also developed to increase the value of the Knowledge Base. As the

Knowledge Base offers theoretical support for the calculation procedures, in case of new

calculation blocks the theoretical support has to be written.

The Database intends to give an overview of the present market. As it is a dynamical and fast

changing environment, regular updates would be beneficial, as well as the introduction of

even more companies and products. The database model used is the relational database

model, but object-oriented database management systems could be also implemented to

save complex data like an entire glass sheet or glass beam, including every characteristic,

making possible future work with them, and making possible to save complex calculations.



123

7 Figures-sources/credits Figure 1.1 Float lines in China, Europe and USA from 1960's to today, adapted from: (Savaëte, 2011) 10 Figure 1.2 Kanagawa Institute of Technology, Japan, source: http://www.thecoolist.com/kanagawa-institute-of-

technologys-glass-building/kanagawa-institute-of-technology-glass-building-7/ 11 Figure 1.3 Apple store entrance in New York, source:

https://www.apple.com/retail/fifthavenue/images/fifthavenue_hero.jpg 12 Figure 1.4 Apple's first spiral glass stairway, Osaka, Japan, source:

http://appleinsider.com/articles/07/11/08/spiral_glass_staircase_at_future_nyc_apple_store_hard_drive_up date_1_0 12

Figure 2.1 Glass sheets commonly used in construction industry, source: http://chinanorthglass.en.made-in-china.com/productimage/pMwJmbYCheRi-2f1j00VeLabREWsNpl/China-Tempered-Glass-Sheet-Customized-Size-for-Floor-and-Clading.html 16

Figure 2.2 Schematic view of the irregular view of soda lime silica glass, source: (Haldimann, et al., 2008), p. 5, Fig. 1.4 17

Figure 2.3 Schematic comparison of the volume’s dependence on temperature for a glass and a crystalline material, source: (Haldimann, et al., 2008), p.5, Fig. 1.5 17

Figure 2.4 Transmittance as a function of wavelength for a typical soda lime silica glass and a low-iron glass with anti-reflective coating, source: (Haldimann, et al., 2008), p. 7, Fig. 1.6 18

Figure 2.5 Stress/strain curves for steel and float glass, source: (O'Reagan, 2014), p. 5, Fig. 2.2 18 Figure 2.6 Typical short term strengths as a function of the flaw depth, source: (Haldimann, et al., 2008), p. 8,

Fig. 1.7 19 Figure 2.7 Crack growth by chemical breaking of oxide network, source: (Khorasani, 2004), p. 24, Fig. 2.7 19 Figure 2.8 Stress corrosion, chemical reaction at the crack tip: (1) adsorption of water to Si-O bond, (2)

concerted reaction involving simultaneous proton and electron transfer, and (3) formation of surface hydroxyl groups, source: (Haldimann, et al., 2008), p. 54, Fig. 3.1 20

Figure 2.9 Crack velocity versus load, source: (Khorasani, 2004), p. 25, Fig. 2.9 20 Figure 2.10 The basic float glass process, source: http://www.tangram.co.uk/TI-Glazing-Float%20Glass.html 22 Figure 2.11 Float glass production, source: http://www.glassforeurope.com/en/industry/float-process.php

23 Figure 2.12 Glass heat tempering process, source: http://www.breakglass.org/How-is-glass-made.html 23 Figure 2.13 Transient stress field during the tempering process, source: (Haldimann, et al., 2008), p. 12, Fig.

1.12 24

Figure 2.14 Post breakage behaviour of laminated glass made of different glass types, source: (Haldimann, et al., 2008), p. 14, Fig. 1.15 24

Figure 2.15 Failure through nickel sulphide inclusions, source: http://www.constructionspecifier.com/wp-content/uploads/2014/04/Lexi-Condo.-by-Ed.-10-20-08-001.jpg 25

Figure 2.16 Breakage pattern of the heat-strengthened glass (left) and breakage pattern of the fully-tempered glass (right) , source: http://www.legardien.com/architectural-products 26

Figure 2.17 Chemical tempering of glass, source: http://www.ctmsrl.it/en/products/detail/tc-forno-industriale-camera-tempera-chimica-vetro/ 26

Figure 2.18 Section through toughened glass showing comparison between the stresses in thermal and chemical processes, source: (O'Reagan, 2014), p. 9, Fig. 2.9 27

Figure 2.19 Laminated glass, source: http://www.gscglass.com/laminated-glass/ 27 Figure 2.20 Continuous beam - Entrance Pavilion of Broadfield House Glass Museum, source:

http://4.bp.blogspot.com/-CGa-- 29 Figure 2.21 Segmented glass beam - Canopy above the entrance of the Yūrakuch÷’s underground train station

in Tokyo, Japan, source: http://aefirms.wordpress.com/2011/02/01/macfarlane-tim/ 29 Figure 2.22 Spliced glass beam being lifted into place, source: (O'Reagan, 2014), p.61, Fig. 8.11 30 Figure 2.23 A beam after failure presenting a typical fracture pattern for timber−glass hybrid beam with the

web made of annealed float glass, source: http://www.glassonweb.com/articles/article/871/, Fig. 13 30



124

Figure 2.24 Lateral torsional buckling model with bending moments applied at both extremities , source: (Haldimann, et al., 2008), p. 116, Fig. 5.6 31

Figure 2.25 Floor plate supported by glass beams, source: (O'Reagan, 2014), p. 49, Fig. 8.1 33 Figure 2.26 Example of a continuous support to a floor plate, source: (O'Reagan, 2014), p. 50, Fig. 8.3 34 Figure 2.27 Interior glass walls, source: http://decorationchannel.com/wp-content/uploads/2013/02/RG-Glass-

Wall-05.jpg 35 Figure 2.28 Application of glass walls and glass fins - Apple store, New York 35 Figure 2.29 Glass connection systems, source: http://www.alibaba.com/product-detail/stainless-steel-glass-

connection-glass-to_500567352.html, (Wurm, 2007), p. 114, Fig. 47, p.115, Fig. 50 36 Figure 2.30 Bolted connection types, source COST Action TU0905 Bolted connections 37 Figure 2.31 Point-supported framing system, source:

http://www2.dupont.com/SafetyGlass/en_US/assets/images/newseum_bolted_glass.jpg 37 Figure 2.32 Adhesive glass‐to‐steel connections, source: (Current & Near-Future Research on Structural Glass,

2012) 38 Figure 2.33 Stress-strain graph of various adhesive systems, source: (Wurm, 2007), p. 88, Fig. 20 38 Figure 2.34 Graph of strength against layer thickness for a hard adhesive and an elastic adhesive, source:

(Wurm, 2007), p. 88, Fig. 21-22 39 Figure 3.1 The Glass Weigh application 42 Figure 3.2 The interface of the Calumen II 43 Figure 3.3 Applications on Google Play for "concrete" 44 Figure 3.4 Relational database terms, source: "Relational database terms" by User:Booyabazooka - Own work.

Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Relational_database_terms.svg#mediaviewer/File:Relational_database_terms.svg 45

Figure 3.5 The three most popular database management engines: Oracle, MySQL and Microsoft SQL Server 46 Figure 3.6 Comparison of the traditional and Agile software development approach, source:

http://www.agilenutshell.com/how_is_it_different 47 Figure 3.7 Relative sizing of the user stories, source: http://www.agilenutshell.com/estimation 48 Figure 3.8 Burndown chart, source: http://www.agilenutshell.com/burndown 48 Figure 4.1 Non-factored load chart for 2.5 mm glass with four sides simply supported, source: (2009), p. 8, Fig.

A1.1 (upper chart) 50 Figure 4.2 Deflection chart for 2.5mm glass with four sides simply supported, source: (2009), p. 8, Fig. A1.1

(lower chart) 50 Figure 4.3 Reference factored resistance-4mm glass 55 Figure 5.1 The Main menu 62 Figure 5.2 The Eclipse development environment 64 Figure 5.3 Schematic representation of the application 66 Figure 5.4 Start-up screen of the application 65 Figure 5.5 The Glass sheet calculation sub-menu 67 Figure 5.6 The Action bar for Depth 1 activities 68 Figure 5.7 Action bar for the glass sheet calculation blocks 70 Figure 5.8 Button example 72 Figure 5.9 Background change overwriting the button layout 73 Figure 5.10 EditText example 74 Figure 5.11 RadioButton example 75 Figure 5.12 RadioGroup example 76 Figure 5.13 Example for design code possibilities 76 Figure 5.14 Android Activity Lifecycle, source: http://www.android-app-market.com/wp-

content/uploads/2012/03/Android-Activity-Lifecycle.png 78 Figure 5.15 Combination possibilities of the Linear layout 79 Figure 5.16 Width/height possibilities 79 Figure 5.17 Example for the use of the "weight" and "background" characteristics 80 Figure 5.18 Example for underlining 81 Figure 5.19 Example for EditText with visibility "gone" 82 Figure 5.20 Example for EditText with visibility set programatically to "visible" 82 Figure 5.21 "Enlargement" of the visible layout on results generating 82



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Figure 5.22 Example for images used to display information related to the notation 84 Figure 5.23 DIN18008 Glass sheet calculation, Description button on the top of the layout 85 Figure 5.24 The Description screen of the DIN18008 Glass sheet calculation 86 Figure 5.25 The Knowledge base outline inside the application 87 Figure 5.26 Structure of the Knowledge base 87 Figure 5.27 The system of the linear layouts inside the Knowledge base 88 Figure 5.28 The DINSheet Activity 92 Figure 5.29 Input of glass type (right) and input of glass sheet inclination (right) 93 Figure 5.30 Input of the shortest load duration (left), support conditions (centre) and lamination information

(right) 93 Figure 5.31 Calculation blocks (functions) for DIN18008 94 Figure 5.32 Modification of the predefined values 95 Figure 5.33 The interface of the American E1300-12a sheet calculation 97 Figure 5.34 Example for the graphical procedure in a design chart 98 Figure 5.35 Glass sheet calculation (Canadian CAN/CGBS1220) 101 Figure 5.36 Glass sheet calculation (Australian AS1288-2006) 103 Figure 5.37 Visual representation of glass fin design concept 106 Figure 5.38 Glass member calculation-glass fin 107 Figure 5.39 Glass member calculation-glass T-beam 108 Figure 5.40 Glass member calculation-hybrid beam 110 Figure 5.41 Glass member calculation-glass balustrade 111 Figure 5.42 Product database category overview 113 Figure 5.43 Product database menu 114 Figure 5.44 Product database-Detailed representation 116 Figure 5.45 The Glass beam equivalent functionality 118 Figure 5.46 Equivalent beam - glass section results 120



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8 Reference list

adhesiveandglue.com. http://www.adhesiveandglue.com. [Online] agilemanifesto.org. http://agilemanifesto.org/. [Online] agilemethodology.org. http://agilemethodology.org/. [Online] AS1288-2006. 2006. Glass in buildings-Selection and installation. s.l. : Australian Standard, 2006. Bennison, Stephen J., HX Qin, Maria and Davies, Phillip S. 2008. High-performance laminated glass for structurally efficient glazing. Hong-Kong : s.n., 2008. Burnette, Ed. 2010. Hello, Android. 2010. CAN/CGSB-12.20. 1989. Structural design of glass for buildings. 1989. Cheremisinoff, Nicholas. 2001. Condensed Encyclopedia of Polymer Engineering Terms. s.l. : Butterworth-Heinemann, 2001. ISBN: 0080502822. COSTAction. TU0905 Bolted connections. DIN18008-1. 2010. Glass im Bauwesen- Bemessungs- und Konstruktionsregeln. s.l. : DIN Deutsches Institut für Normung, 2010. 2010. DIN18008-1 Glass im Bauwesen- Bemessungs- und Konstruktionsregeln. s.l. : Deutsche Norm, 2010. E1300-12a, ASTM. 2009. s.l. : ASTM, 2009. Haldimann, Matthias, Luible, Andreas and Overend, Mauro. 2008. Structural Use of Glass. Zürich : IABSE, 2008. Vol. Structural Engineering Documents 10. ISBN 978-3-85748-119-2. Haseman, Chris. 2011. Android Essentials. 2011. Khorasani, Naimeh. 2004. Design principles for glass used structurally. Lund : Building Science Department Lund University, 2004. ISSN 1103-4467. Kovács, Áron. 2011. Translator and Information Retrieval Application on Android, using OCR algorithms. 2011. Louter, Pieter Christiaan. 2011. Fragile yet Ductile, Structural Aspects of Reinforced Glass Beams. Zutphen : Wöhrmann Print Service, 2011. ISBN 978-90-8570-743-1. Lucas Jordan, Pietere Greyling. 2009. Practical Android Projects. 2009. Machado, Paulo. 2011. Normas para o cálculo estrutural do vidro-a nova. s.l. : VIII Congresso de Construcao Metalica e Mista, 2011. Morris, Jason. 2011. Android User Interface Development. 2011. Murphy, Mark. 2010. Beginning Android 2. 2010. O'Reagan, Chris. 2014. Structural use of glass in buildings. Second. London : The Institution of Structural Engineers, 2014. ISBN 978-1-906335-25-0. Santarsiero, Manuel. 2012. Current & Near-Future Research on Structural Glass. [ed.] Prof. Jan Belis. Ghent : Ghent University, 2012. pp. 85-89. Savaëte, Bernard Jean. 2011. The world flat glass industry. Proposals for an education on history & economy. 2011. pp. 704-707. Schneider, Jens Wörner,Johann-Dietrich. 2008. DIN 18008 – Glas im Bauwesen. s.l. : Stahlbau Spezial 2008 Konstruktiver Glasbau, 2008. 1989. Structural design of glass for buildings CAN/CGSB1220. s.l. : Canadian National Standards Board, 1989. Wurm, Jan. 2007. Glass Structures-Design and construction of self supporting skins. Basel, Boston , Berlin : Birkhäuser, 2007. ISBN: 978-3-7643-7608-6.

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