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STEEL CONSTRUCTION:
COMPUTER AIDED DESIGN & MANUFACTURE
Lecture 5.2: The Future Development
of Information Systems for Steel
Construction
OBJECTIVE/SCOPE
To discuss possible future developments in data transfer between different stages in the
steel construction process, through a product model approach. To indicate the benefits that
might be realised as a result of this and how such changes can be achieved.
PREREQUISITES
Lecture 5.1: Introduction to Computer Aided Design and Manufacture
RELATED LECTURES
None.
SUMMARY
The processes of exchanging information at various stages of a steel construction project
are reviewed briefly. The potential advantages of enabling this transfer to be made directly
between computers rather than, as at present, on paper are outlined. The basic
requirements that must be met before such a system can be implemented are discussed in
principle, and the practical ways in which it might be achieved are considered. The role ofthe management information system is explained, and a realistic approach to
implementation throughout the industry is outlined.
1. INTRODUCTION
The progress of a building project from client's brief to completion of execution entails the
generation and transfer of large quantities of information, much of it in the form of paper
documents. Many people contribute to the project as it progresses through its various
phases.
Inefficiency and disruption results from the need to translate information from one formatto another - as occurs, for example, in the creation of workshop drawings for the steel
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fabrication - as well as from the transfer of inadequate or erroneous information, and from
late changes which may entail laborious reworking.
The aim of this lecture is to extend ideas relating to information exchange standards,developed for manufacturing industry, to the processes of information transfer between the
various stages of construction, in order to render these more efficient and economical.
2. INFORMATION EXCHANGE IN THE
CONSTRUCTION PROCESS
2.1 Information Exchange: The Present
Figures 1 and 2 give an indication of the information generated and exchanged within the
construction process, and the various parties which may need to be involved in such
exchanges of information. Figure 3 represents a portion of this information schematically,
using the terminology of the Product Model - the product being in this case the steelwork
aspect of the building project. This figure marks the stages in the life of the product, and
illustrates the accumulation of product data as product life progresses. Information
exchanged between phases often has particular legal significance. A particular example is
the set of information exchanges which take place at the end of the design phase and
which are marked by the signing of a contract. There is a particular onus on the
participants to ensure the completeness, correctness, clarity and finality of suchinformation exchanges, as errors can waste time and money and variations lead to
contractual claims.
Common sense would suggest that the quantity of information exchange should be
confined to the essential - consistent, of course, with the conveyance of an adequate
understanding of requirements.
At present this information is exchanged between participants as hard copy, i.e. as reports,
calculations, drawings, etc. Interpreting this data at each stage of information exchanged
can be a time consuming process, particularly if there are ambiguities, or if some aspectsare incomplete. Modifications in the information generally result in changes within all
subsequent stages of the product model route. Changes in the client brief, for instance,
cause reworking of design calculations, drawings, details, etc. and if made late in the
programme can result in significant delays. Substitution of alternative section sizes at the
detailing stage to take account of material availability, for example, may have less
consequence, but even so the required changes to details may be time consuming. It is
always a danger too that isolated changes have implications for other aspects of
construction which are not identified in the rush to make the corrections. Something as
simple as a change in beam depth, for instance, may have considerable significance for the
accommodation of services.
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The present system does, however, provide useful opportunities for checking information
since at each stage of information transfer the data is examined afresh. It also allows forconsiderable flexibility in the system, with some information being passed on in a partially
complete form, and in a variety of formats. Feedback between later stages in the product
model route and those earlier in the process are also relatively straightforward.
2.2 Information Exchange: The Future
More use is being made of computers within each stage of the product model route, with a
view to increasing efficiency. One of the most time consuming aspects of using computers
is entering data, and significant savings can therefore be achieved if the effort required for
data input is minimised. This can be achieved by transferring data between successivestages in the product model route electronically rather than as hard copy.
Future information exchange will therefore involve wider use of computers to reduce
manual input of data and provide a better flow of information relating to the steelwork
'product'. For instance information derived from design calculations could be transferred
directly to a computer-aided design (CAD) system to avoid duplicating definitions of basic
data such as beam spans, column heights, etc. and to enable the output from the
calculations (section sizes, beam reactions, etc.) to be taken directly into the next stage.
Some developments have already taken place in this sense. The integration of general
arrangement drafting and detailing systems, and the output of 3-D modelling systems
leading directly into numerically controlled machines for fabrication. This meansreplacing the present limited conventions and protocols for information exchange, both
manual and computer based, with a more rigorous unified information exchange system
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which can apply across the entire construction industry, and which is capable of operation
in all phases of the project's life.
Such a system requires:i.the establishment of a unified computer based product description.
This requires data in a sufficiently comprehensive form to describe all relevant aspects
of the product at all stages.
ii. the creation of standards for the transfer of information between different computer
systems and organisations.
iii. the creation of information management systems - to control information changes,
access rights and quality assurance.
These requirements can be illustrated by the following simple examples:
i.A computer program for the elastic analysis of frames requires member cross-sections to
be described in such terms as area and moment of inertia. It does not require a
description of how the area is distributed throughout the section, i.e. what its shape is.
Such a description would, however, be inadequate to generate connection details. It is,
therefore, desirable to have a single format which would accommodate both needs,
permitting an efficient transition from analysis to drafting.
This is a somewhat trivial example. Most frame analysis programmes now allow
definition of cross-sections by reference to a standard library. However it does illustrate
the point that data which is sufficient to describe the product at one particular stage in
the process may be inadequate for other stages.
ii.Working on a range of products, a steelwork fabricator has to produce shop drawings
from engineering design information originating from a variety of software and
hardware systems, some of which are mutually incompatible. It would seem
advantageous if this fabrication could access directly the graphical information base
created by the designer in each case. This would necessitate a CAD system capable of
information exchange with all others on the market. CAD developers have tended to
concentrate on transfer of information between computers running the same software,
i.e. theirs, rather than facilitating exchange of information with machines running
software produced by a competing CAD developer. An information exchange format
which is particular to a CAD package is termed the 'native' data exchange format of that
system.Considerable progress has been made in this direction with regard to alphanumeric data.
The ASCII format provides a basic standard so that text produced using one
wordprocessor system, for instance, can be output in this form enabling it to be read
directly by other systems or application programs. Dealing with text is a relatively simple
matter because it involves a limited number of unique characters. Even so, the ASCII
standard provides for the basic characters only with no formatting signals to indicate
different text styles, subscripting, etc. Data for presenting information graphically is even
more complicated, but some standards have been established, IGES and DXF files serve a
similar function, providing a standard of data appropriate to drawing instructions, enabling
the output from the CAD system to be interpreted by another. However it should be clear
that this is not in itself sufficient to provide a full description of what is being drawn. The
full product model description requires much more complete information.
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3. A FRAMEWORK FOR CHANGE
3.1 The Product Model
An essential first step towards an integrated approach is the development of a standard
specification for the organisation of technical information on structural steelwork. This
specification is referred to as the 'logical product model' and provides a standard basis for
the production of interfaces between structural steelwork software products. When the
technical information on a particular structural steelwork contract is arranged according to
the 'logical product model' specification, it is then simply referred to as a product model.
The product model approach can be used to transfer information between all sorts of
software products by using product model files (computer files) to transfer the information
automatically. Consistent versions of existing paper documents can then be generated, as
required, from this unified digital description, or product model.
In broad terms, the system would work in the following way:
Each software product concerned with structural steelwork would have its own
product model interface.
Product model files would be used to transfer information between the various
software products.
The product model interfaces would read information from, and write information
to, the product model files as and when required.
Figure 4 compares the traditional approach with the product model approach for
information exchange. The main advantages of the product model approach are that it will
offer flexibility for users to configure and develop systems from the software products
they prefer (provided each product they wish to use has a product model interface).
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A product model for steelwork construction is currently being developed within the
Eureka EU130 CIMSTEEL project.
In the long term, the approach is capable of being developed to achieve full databaseintegration of software products. It is the target system architecture activity which aims to
map out the future part of development.
3.2 Information Exchange Between Software Products
3.2.1 Introduction
The native exchange file formats are 'de facto' standards established by particular software
vendors and remain under their control. In contrast, the concept of a neutral file format
implies a universal standard independent of any particular vendor. Such standardsoriginate typically from research projects but are now increasingly coming under the
control of international standards bodies.
One of the principal goals of current research projects, e.g. EUREKA, ESPRIT, is to make
it possible to transfer information easily and inexpensively between the many different
software products already available or being developed for the structural steelwork
industry. This implies direct digital transfer of information obviating the need for manual
interpretation of drawings, etc.
Examples of software products involved are:
Structural analysis programs.
Computer aided design and detailing systems.
Software for programming of NC (numerically controlled) machines, tools, e.g.
sawing, drilling, flame cutting, and profiling machines.
Software for programming of welding cells.
Company MIS (management information systems) and software for cost
estimating.
The main benefits of linking software are that time and effort can be saved, and
transcription errors can be eliminated.
Traditionally, wherever a company requires an efficient means of information exchange
between specific software products, a new piece of purpose-written software, 'an
interface', has to be produced. Unfortunately, an interface will only work with the
particular pieces of software for which it was specifically written in the first place. Thus,
every time a new software product is introduced, new interfaces have to be produced to
link with each and every other piece of software with which it needs to exchange
information. The simple interface of two pieces of software solves only a local problem
and creates a localised increase in efficiency (Figure 5). To achieve a solution to meet the
requirement of the whole industry a wider perspective is required.
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3.2.2 'Neutral' graphical exchange file formats
The IGES Standard
The most widely supported of the current generation of neutral exchange file formats is
the Initial Graphical Exchange Standard (IGES). It originated in 1980 with the then United
States National Bureau of Standards. By 1988 Version 4.0 had been published, and at the
time of writing this lecture, a final version - to be Version 5.0 - is awaited. While IGES
has extended its ability to represent information and addressed problems of efficiency, the
standard has grown increasingly complex. It is similar in principle to the DXF system,
which is a proprietary product of Autodesk.
The neutral file concept established by IGES led to the evolution of several other data
exchange standards, each targeted on the needs of a specific group of CAD/CAM users. In
each case, the objective was to make the exchange process more efficient and reliable, and
to maximise the ability of the developed data exchange file format to represent particular
classes of engineering information.
While considerable technical progress was made by these various standards projects, the
result was a proliferation of data-exchange formats. It was recognised that the solution lay
in a single second-generation neutral file standard which would provide a unified
framework for data exchange by all sectors of engineering. The result was the new
emerging International Standards Organisation (ISO) STEP Standard.
The ISO STEP Standard
STEP, the Standard for the Exchange of Product model data seeks to provide consistent
data models across a broad range of engineering applications which would be applicable
to the whole life-cycle of engineering products. Thus the STEP data models will
(eventually) enable all aspects of a construction project to be represented, from conception
through to the structure's ultimate demolition.
So in some respects, STEP is just another neutral data exchange file format. However, the
true significance of STEP is that it uses much definitive second-generation engineeringdata exchange standards based on the concept of a product model. It is interesting to note
that during the early development of IGES it was 'Product Data' that was to be exchanged.
The switch to 'Product Model' in STEP reflects a recognition that it is information (i.e.
meaning), not data, that has to be transferred (see Figure 6).
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Currently, STEP is little more than a powerful enabling technology and, while it may be a
long-term task to compile the necessary component product models, the technology for the
implementation of STEP will soon be available [1, 2].
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3.3 Management Information Systems (MIS)
To make real progress in the area of the future management information systems it is
necessary to have a clear and common view of how it relates to the product model. Themain point to recognise is that the product model is limited to technical information.
Management information must be dealt with separately by the MIS.
Figure 7 presents a simplistic view of the structural steelwork design and manufacture
process with boxes representing the functions of scheme design, detail design, fabrication
and erection. Types of software products which may be used are shown under each
function. At the top of the diagram is the Management Information System, which
monitors and controls the functions. At the bottom of the diagram is the Product Model
which provides the technical information needed by the software products in the form of
product model files.
Although a clear division between technical and management information can be defined
theoretically, in reality the MIS will need to:
Know where all technical information is located and organised.
Monitor and control all modifications to Product Model information.
Monitor and control all Product Model file transfers to and from the software
products.
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Thus, in addition to a 'management information controller' the MIS should also include a
'product model information controller' whose function will be to manage the flow of
product model information in the form of product model files. Figure 8 illustrates the way
in which this could be arranged. In essence, the MIS controls both the managementfunctions and the transfer of product model information. Product model files are stored in
the product model file store and are used to transfer technical information to enable the
various pieces of technical software to perform their required operations for any particular
contract going through the factory.
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It should be noted that Figure 8 represents product model file interfacing, and does not
include database integration of products model information. As such, it can only represent
a step towards the development of fully integrated systems.
4. IMPLEMENTATION
Incremental Implementation
It has to be fully recognised that many of these long term aims have only a theoretical
meaning today. As a result practical incremental implementation is essential so that the
industry can start to reap the benefits in the shorter term. The shorter term goals of
common information exchange standards allow the interfacing of systems enabling the
industry to take the first vital steps towards implementation of computer integrated
manufacture (CIM).
Recognising the different ways in which steelwork companies are managed, and will
continue to be managed, it is evident that an all encompassing standard for management
information is going to be very difficult to achieve.
However, if the finance, sales and marketing, personnel, and administration functions are
excluded for the time being, then a common approach is feasible for:
Contract planning.
Capacity planning.
Process planning. Design control.
Materials control.
Fabrication control.
Despatch/transport control.
Erection control.
It is in these areas that an industry-wide approach could be developed. An industry MIS
could be produced covering these functions which would comprise a number of modules
operating in conjunction with a management information database and a product model
file store.
5. CONCLUDING SUMMARY
Computer aided transfer of standard product information between design and
fabricator will reduce time for information production, detailed design and the
production of fabrication drawings, as all required information can be transferred
automatically.
The net result will be significant increases in efficiency due to the reduction in
contract variation claims and hence a less contentious contractual relationship.
Controlled early access to relevant information and changes to information has
great advantages in reducing lead times and errors.
This future development will result in a dramatic change in the nature of
estimating with respect to current practice. The fabricator will receive standard
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items of product information, files of historical manufacturing (material and
workmanship) cost data for each item. The 'scientific' part of estimating can thus
be automated. Commercial judgments on an estimated contract value can then be
applied in the more certain knowledge that estimates are correct. There are four key requirements for the structural steelwork industry to enable the
effective and efficient transfer of product information. These are computer-based
product descriptions, international information exchange standards for structural
steelwork (neutral exchange file formats), and information control (management
information systems).
These developments represent a fundamental change in current methods of
working. Acceptance by the industry can only be achieved by the introduction of
short term solutions which lead towards the ultimate goal.
6. REFERENCES[1] National Economic Development Council (NEDC), Information Transfer in Building,
NEDO, London, 1990.
[2] Watson, A. S., CAD Data Exchange, Proc. Institution of Civil Engineers, Part 1, 1990,
Vol. 88, December, 955-969.
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