Download - Comparative Study of Rcc T-beam Bridge By
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
1/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
2/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
3/32
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).
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
4/32
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
5/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
6/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
7/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
8/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
9/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
10/32
The description of actions and their notations given
as per IRC:6-2010.
Permanent action.
Variable gravity loads treated as permanent loads.
Variable actions.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
11/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
12/32
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)
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
13/32
(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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
14/32
(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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
15/32
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
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
16/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
17/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
18/32
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:
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
19/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
20/32
Cross Section of Bridge- Deck
Plan of Bridge -Deck
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
21/32
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
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
22/32
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:
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
23/32
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
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
24/32
Mmax = (DL +SIDL)B.M +Max. OF (CLASS A OR70RTRACKED OR 70R WHEELED)BM
=1370 + 936+ 2784
=5090 kN-m
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
25/32
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
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
26/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
27/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
28/32
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
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
29/32
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.
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
30/32
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
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
31/32
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).
-
8/10/2019 Comparative Study of Rcc T-beam Bridge By
32/32
THANK YOU