Comparative Study of Rcc T-beam Bridge By

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COMPARATIVE STUDY OF RCC T-BEAM BRIDGE

BY

IRC: 112-2011 & IRC: 21-2000

By

A V PRANAY KUMAR REDDY

12011D2002M.TECH(S.E)

Under the guidance of

Mrs. P. Srilakshmi

ASSOCIATE PROFESSOR of Civil Engineering

Department,

JNTUH College of Engineering , Hyderabad.


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Outline of Presentation

Introduction. Literature review.

Aim of present study.

Bridge loading.

Method of Grillage analysis.

Design consideration.

Numerical Analysis.

Conclusion.

Scope for further study.


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INTRODUCTION

Bridge construction has been one of the importantengagements of mankind from the earliest days and today.

Bridges are one of the most challenging of all civil

engineering works. The numbers and sizes of bridges have

continuously increased in last fifty years.

To cope up with this demand, tremendous efforts all over the

world in the form of active research in analysis, design and

construction of bridges is continuing.

The two major methods of practice in design are Working

stress design Method (using IRC:21-2000) and Limit state

design method (using IRC: 112-2011).


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B.H.Solanki & Prof.M.D.Vakil

In India IRC has published new code IRC-112:2011 that

combines specifications for both RCC & prestress concrete

bridges.

In this paper the flexure design was carried out by LSM and

WSM. Emphasis is put on the variation in amount of concrete

and steel by both. It also shows the design charts for particulargrade of concrete and steel for various moment capacities.

As it always a question how it differs from older one whenever

theres new code of practice, this paper consist of flexuredesign for different combination of grade of concrete & steel In

this paper the flexure design approach by both the IRC-

112:2011 & IRC-21:2000 is discussed.


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Kamde D ,John,Hulagabali A

In this paper comparative design of a single-span bridge

using AASHTO LRFD Bridge Design specification, Indianstandard T beam girder bridge specification and deck

slab(excluding girders).

The difference in design philosophy, calculation procedures

was studied. Foundation design and related geotechnicalconsiderations are not considered. The span of the bridge

was studied for 10m.

It was found that the (i) shear force calculated is more in IS

method (ii) the amount of concrete in the deck portion is

more in IS method (iii) large amount of reinforcement wascalculated in case of IS method.

However for the design of more than 25m span above

results were reversed. The design using LRFD Method is far

safer than IS method (with/without Girder) because ofs ecial rovision for ara et wall alon the brid e.


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B.H.Solanki & Prof.M.D.Vakil

In this paper shear force for a section was assumed to be the

same for both Working stress approach (IRC:21-2000) and limitstate approach (IRC:112:2011).

Shear force is more critical force than other actions on the bridge

member, the design was carried out by the above two methods

for comparison of parameters such as shear strength, steel

required for shear, shear resisting capacity of member without

shear reinforcement .

Since shear is more critical than other actions on bridges

members,the combinations of fy grade of steel and fck grade of

concrete gives more shear strength so member requires minimumor no shear reinforcement.


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AIM OF THE PRESENT STUDY

The aim objective of this project is to know

which method requires more materials when

designed in Working stress method (IRC 21-

2000) and Limit state method (IRC112-2011)for T-beam girder bridge of span 10m, 15m, 20m

respectively, when all other difficulties arise

during the construction of bridge are assumed to

be same for both methods.


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Bridge Loading

The loading has profound effect upon the design,

construction and eventually upon the cost of any bridge of a

given span.

Besides carrying their own weight, the decks are designed

for certain loadings imposed partly by the vehicles and theusers and partly by the nature.

In order to maintain uniformity in design, loading standards

have been laid down for the guidance of engineer.

Different countries, including India, have their own loadingstandards. The code used in India is IRC:6-2010.


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The description of actions and their notations given

as per IRC:6-2010.

Permanent action.

Variable gravity loads treated as permanent loads.

Variable actions.


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METHOD OF GRILLAGE ANALYSIS

In recent years, the Grillage Analogy Method, which is a

computer-oriented technique, is increasingly being used in theanalysis and design of bridges.

When a bridge deck is analyzed by the method Grillage

Analogy, there are essentially five steps to be followed for obtaining

design responses:

Idealization of physical deck into equivalent grillage.

Evaluation of equivalent elastic inertias of members of grillage.

Application and transfer of loads to various nodes of grillage. Determination of force responses and design envelopes.

Interpretation of results.


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DESIGN CONSIDERATIONS

LIMIT STATE METHOD

Aims of Design

General performance requirements:The bridge, as a complete structural system and its

structural elements should perform their functions adequately

and safely, with appropriate degrees of reliability during

design life and during construction. Adequacy of performance

is defined in terms of serviceability, safety, durability and

economy. Two basic groups of limit states are considered:

(a) Ultimate Limit States (ULS)

(b) Serviceability Limit States (SLS)


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(a) Ultimate limit states (ULS)

Limit state of equilibrium

When subjected to various design combinations of ultimate loads the

bridge or any of its components, considered as a rigid body, shall not

become unstable.

Limit state of strength

The bridge or any of its components shall not lose its capacity to sustain

the various ultimate load combinations by excessive deformation,transformation into a mechanism, rupture, crushing or buckling.


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(b) Serviceability Limit States (SLS)

Limit state of internal stress

The internal stresses developed in the materials of

structural elements shall riot exceed the specified

magnitudes when subjected to combination of

serviceability design actions.

Limit state of crack control.

The cracking of reinforced, partially prestressed and

prestressed concrete structures under serviceability loadcombinations is kept within acceptable limits of crack

widths in such a way as not to adversely affect the

durability or impair the aesthetics.


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Limit state of deformation

The deformation of the bridge or its elements when subjected

to combination of design actions shall not adversely affect theproper functioning of its elements, appurtenances, and riding

quality.

Limit state of fatigue

The bridge or any of its components shall not loose its capacity

to carry design loads by materials reaching fatigue limits due to its

loading history


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WORKING STRESS METHOD

Stresses that are likely to occur in plain and reinforced

concrete structure, under the worst combination of loads andforces, specified in IRC: 6 shall be provided for in accordance

with accepted procedures of design and construction and in

conformity with the fundamental principles of mechanics

without exceeding limits of stresses.

The detailing of reinforcement in all components shall be as to

ensure satisfactory placement and good compaction of

concrete all around in the components with due consideration

being given to the construction techniques adopted.


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Basis of Design:

The strength of a reinforced concrete structural member

may be assessed by commonly employed elastic theory

and it may be assumed that:(i) The modulus of elasticity of steel is 200Gpa.

(ii) The modular ratio of 10 is adopted.

Unless otherwise permitted, the tensile strength of concrete is

ignored.

For working stress approach, service loads are used in the

whole design and the strength of material is not utilized in

the full extent.

In this method of design, stresses acting on structural

members are calculated based on elastic method and theyare designed not to exceed certain allowable values. In

fact, the whole structure during the lifespan may only

experience loading stresses far below the ultimate state

and that is the reason why this method is called workingstress a roach.


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NUMERICAL ANALYSIS

In this study a T- beam girder bridge has been analyzed using

grillage analogy and design performed as per Limit state method

and working stress method. The design data adopted for the

study are as follows:


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Bridge data 1:

Effective span of Tee beam= 20 mWidth of carriage way= 7.5 m

Thickness of wearing coat =80 mm

Spacing of main girders =2.5 m

Width of kerb =0.5 m

Width of footpath =1 m

Thickness of deck slab = 250 mm

Modular ratio =10

Number of main Girders = 4

M30 Grade and Fe-415 Grade HYSD bars.As width of carriage way is 7.5m, number of lanes proposed are 2.

Therefore LIVE LOAD combination: ONE LANE OF 70R OR TWO

LANES OF CLASS A.


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Cross Section of Bridge- Deck

Plan of Bridge -Deck


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DESIGN BASED ON IRC: 21-2000

Load calculation for grillage model

(i) Dead load:

Self weight -1

(ii) SIDL

a) Wearing coat (80 mm) = -1.84 kN/m2

b) Weight of kerb = -7.8 kN/m2

c) Weight of crash barrier = -14.86 kN/m2

d) Foot path load = -3.44 kN/m2


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Cross Section of End Longitudinal girder

Cross section of Intermediate longitudinal girder

A=1.3*106 mm2,

Yc=1400 mm,

Ixx =0.9676*10 12mm4,

Iyy=108mm4,

Izz=0.4838 *1012mm4

A=1.237*106 mm2,

Yc=1380 mm,

Ixx =0.936*1012mm4,

Iyy=108

mm4

Izz=0.468 *1012mm4

Sectional properties of longitudinal members:


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Design of B.M reinforcement for external

girder at L/2

Load type BENDING MOMENT (kN-m)

DEAD LOAD 1370

SIDL 936

Load type BENDING

MOMENT(kN-m)

BENDING

MOMENT WITH

IMPACT FACTOR

(kN-m)

CLASS A 844 990

70R TRACKED 2420 2662

B.M due to DL and SIDL for external longitudinal girder at mid

span

B.M due to Live load for external longitudinal girder at mid span


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Mmax = (DL +SIDL)B.M +Max. OF (CLASS A OR70RTRACKED OR 70R WHEELED)BM

=1370 + 936+ 2784

=5090 kN-m


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From the designproblem carried out in the project, the followingconclusions can be made:

1. The savings of materials in Limit state method is almost nil for

the deck slab.

2. In case of 10 m span it can be seen from the results the cross

section in the savings of steel in Limit state method in the design

for B.M in girder at mid span and quarter span is nearly 30 %

and 50 % less as compared to Working stress method.

CONCLUSIONS


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3. In case of 10m span, the difference in the reinforcement

for shear force for girder and deck slab is negligible.

4. In case of 15m span, the savings in the concrete in the

design for B.M for the same amount of steel reinforcement

at mid span by Limit state method was around 7-9

%.However at quarter span the savings in concrete andsteel are 7-9 % and 18% as compared to Working stress

method.


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5. In case of 20m span, the savings in the concrete and steel

due to B.M by Limit state method are around 9-11 % and

2% when compared to Working stress method.

It can be concluded that the Limit state method is

economical than Working stress method.


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1. The current study is limited to the load combination of dead load ,SIDL and live load. The study can be extended by including

longitudinal forces, accidental actions, wind load etc.

2. The current study was done for R.C.C. T beam girder which can beextended to prestressed girders.

3. The comparison can be checked for longer spans as the results may

vary when the B.M due to external loads are more.

SCOPE OF FURTHER STUDY


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REFERENCES

1. Amit Saxena & Dr. Savita Maru comparative study of the

analysis and design of T-beam girder and box girder

superstructure Published in IJREAT International Journal of

Research in Engineering & Advanced Technology, Volume 1,

Issue 2, April-May, 2013.

2. B.H.Solanki & Prof.M.D.Vakil Comparative study for

flexure design using IRC 112:2011 & IRC 21:2000,

Published in International Journal of Scientific & EngineeringResearch, Volume 4, Issue 6, June-2013.


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3. Kamde D, John B and Hulagabali A (2014) Comparative

Study for the Design of single span bridge using AASHTO

LRFD and Indian Standard Method, International

Conference on Advances in Engineering & Technology 2014 (ICAET-2014) Page no:44.

4. B.H.Solanki & Prof.M.D.Vakil comparativestudy for shear

design using IRC 112:2011 & IRC 21:2000, Published inInternational Journal of Scientific & Engineering Research,

Volume 4, Issue 6, June-2013.

5. E. C Hambly, BridgeDeck Behavior chapman and Hall,

Second Edition. 1991


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6. N Krishna Raju, Design of Bridges Oxford and IBH

Publishing Co. Pvt. Ltd., New Delhi, fourth Edition.

7. IRC:6-2010, Standard Specifications and Code of

Practice for Road Bridges, Section II, loads and

stresses.

8. IRC:112-2011, code of practice for concrete road

bridges.

9. IRC:21-2000,Standard Specifications and Code ofPractice for Road Bridges", Section: III, cement concrete

(plain and reinforced).


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Comparative Study of Rcc T-beam Bridge By

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