This document analyzes the effect of skew on stress resultants in T-beam bridges under various Indian Road Congress (IRC) loading conditions. T-beam bridge models with spans of 14m and varying skew angles from 0-45 degrees were modeled and analyzed using CSi Bridge software. The results show that bending moment, shear force, and torsion increase with higher skew angles and heavier loadings. Specifically, IRC AA tracked loading produces 10-15% higher bending moments than IRC 70R loading. IRC AA tracked and wheeled loadings also produce significantly different stress responses, with up to 40% variation. The analysis provides guidance on the behavior of skewed T-beam bridges under IRC standard loadings.

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 8, Issue 2, February 2017, pp. 410–417 Article ID: IJCIET_08_02_044
Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=2
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
EFFECT OF SKEW FOR VARIOUS IRC LOADINGS
ON A T-BEAM BRIDGE SECTION
Mohammed Anif
P. G. Student, Civil Engineering Department,
SRM University, Chennai, Tamil Nadu, India
Prof. G Augustine Maniraj Pandian
Professor, Civil Engineering Department,
SRM University, Chennai, Tamil Nadu, India
ABSTRACT
India is on the threshold of becoming a developed country. Naturally it is investing heavily
on new bridges to improve the road / rail connectivity across the country. A bridge carry
uniformly distributed dead load, vehicular live load to its surface and transfers the same to the
support by flexure, shear and torsion. Bridges in India are designed on the basis of loading
conditions specified by Indian Road Congress (IRC) codal provisions. Skew bridges or Curved
bridgesare now-a-days designed due to space constraints prevailing in urban or densely
populated areas in the form of mountainous terrain, winding river courses, unplanned
construction of housing and other infrastructure. A study on variation in the stress resultants
with introduction of skew in the bridge layout is thus very important to understand the complex
behaviour of the structure. T-beam bridges are designed for small and medium span bridges.
In this paper T-beam bridges are modelled and analysed by introducing skews for various span
lengths and IRC loading conditions .Careful investigations have been carried out using CSi
Bridge computer software and the results are compared graphically.
Key words: IRC loadings, Skew, T-beam bridge.
Cite this Article: Mohammed Anif and Prof. G Augustine Maniraj Pandian, Effect of Skew
for Various IRC Loadings on a T-Beam Bridge Section. International Journal of Civil
Engineering and Technology, 8(2), 2017, pp. 410–417.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=2
1. INTRODUCTION
One of the most important steps in the process of designing a bridge is to determine the most
appropriate live load representing to a high certainty, the expected normal traffic loads that might go
over the bridge. These expected Live Loads vary from a country to country, depending upon many
parameters such as degree of locality, the volume of traffic, the nature of the expected major traffic
passing over the bridge. In India, IRC: 6 standards are referred for load considerations while designing
bridges.
In countries like India, due to high population growth and rapid urbanization space restrictions is a
major problem. High demand for land and illegal encroachments is a common problem in the country.

2. Mohammed Anif and Prof. G Augustine Maniraj Pandian
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Government projects suffer to a great extent and even lead to stagnant infrastructure growth. Hence in
highly congested areas due to non-availability of land bridges are often altered from the straight layout
to a skewed or curved one. Even in mountainous regions or the regions with some form of
geographical constrains skew bridges become necessary .In order to ensure safe design of skewed or
curved bridges, it is very important to understand the behaviour of the bridges for various loading
conditions.
2. LITERATURE REVIEW
[1]
Nikhil Deshmukh, Dr., Dr. U.P. Waghe conducted their research for the effect of skew on the design
parameters of the bridge. Skew angle is the difference between alignment of intermediate and end
support and a line square to the longitudinal axis of bridge above. The author used ABAQUS for
analysis. It was analyzed that for obtuse angle longitudinal girder with increase in skew angle there
was increase in shear and mid span moment and a rapid increase in torsion moment. It was also
analyzed that for acute angle longitudinal girder with increase in skew angle there was decrease in
shear and mid span moment. There is insignificant change for inclusion in design up to 20 degree
skew.
[2]
S.V.V. Prasad in another research carried out the design of concrete girder bridge. The design of
fly over bridge was carried out successfully by using IRC: 21 2000 codal provisions. Deck Type
bridge was adopted to ensure safety, serviceability and economy .The design of deck slab with ‘I’
girder, pier with pier cap of Flyover Bridge was carried out.
[3]
X.H. He, X.W. Sheng conducted research in which a 1:8 model was analyzed for 3 spans
continuous pre-stressed concrete box Girder Bridge for railway. Static and dynamic behavior of bridge
model was analyzed in this paper. Skewed bridges are becoming a popular choice for high speed
railway bridges. Effect of torsion was also taken into consideration in the analysis for reactions,
deflections, strains and moments. The width/span ratio for a box girder is much lesser as compared to
any other bridge sections. Also strength/weight ratio enhances stability. Hence providing more
torsional rigidity.
[4]
Christos P. Katsaras, Telemachos B. in his research studied the effect of uplift on the torsional
rigidity of a bridge superstructure. Uplift is caused when the torque exceeds the torsional stiffness of
the structure. Hence uplift protects bridge from excessive torque and thereby stability is improved.
Two conditions were taken into account for studying the effect of uplift i.e. before and after concrete
cracking. Before concrete cracking the torsional stiffness remains constant and it is not significantly
affected by the reinforcement and the relative values of bending moment, shear force and torsion.
After concrete cracking the torsional behavior of element is non-linear with significant reduction of
corresponding stiffness that depends on reinforcement.
Skew bridges are very important modification in normal straight bridges and finds applications in
highly congested urban areas due to space constrains. Skew brides like any other bridge structure
undergo moment and shear but in addition to that torsion plays an important role in on the resultant
stress resultants. Use of different sections for super structures such as box girder, simple girder, PSC
beams with flange and web, etc. will give a clear idea of providing guidelines and information
regarding choice of material and section.
3. MODELLING AND ANALYSIS
The modelling and analysis of bridges was carried out by CSi Bridge computer software and careful
study of parameters such as bending moment, shear force, torsion and reaction forces was carried out.
This paper includes the comparative analytical study of 14mspan T-beam bridges for various skew
angles and IRC loading conditions. The Load considerations for all the models are similar and it is as
per IRC codal provisions. The study includes the comparison of flexural moment, shear, torsion and
support reactions of the bridge structure. The model consists of T-beam bridge consisting of 3 girders

3. Effect of Skew for Various IRC Loadings on a T-Beam Bridge Section
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placed at a spacing of 2.5m from each other. The bridge has a clear roadway of 6.8m. The cross
sectional dimensions of the super structures are kept the same for all the bridges varying the skew
angle and the loading conditions on the bridge. For 14 m span, a straight skew has been introduced in
the middle 10 m span.
4. ANALYSIS
Table 1 Basic Considerations
Basic Considerations Data
Spansss Span 14m
Clear roadway 6.8 m
No. Of T-Beams 3
Grade of concrete M25
Grade of reinforcement Fe415
Thickness of slab 0.2 m
Skew angles considered 0, ,15,25,30,35, 40, 45
The models of T-beam bridges with various skew angles are shown in Fig. 1-7
Figure 1 Bridge with straight alignment Figure 2 Bridge with 15° Skew
Figure 3 Bridge with 25° Skew Figure 4 Bridge with 30° Skew

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Figure 5Bridge with 35° Skew Figure 6 Bridge with 40° Skew
Figure 7 Bridge with 45° Skew
5. RESULTS
Analysis results for various loading conditions and varying skewed spans have been obtained and
tabulated.
5.1. Bending Moment
The bending moment induced is shown in in Table 2.
Table 2 Bending moment
BENDING MOMENT(kN-m)
SKEW
LOADING
IRC A IRC AA TRACKED IRC AA WHEELED IRC 70R IRC B
0 834 2010 1224 1851 498
15 892 2122 1268 2040 532
25 918 2145 1279 2128 548
30 931 2157 1285 2172 656
35 944 2168 1312 2215 564
40 969 2193 1342 2253 579
45 998 2244 1371 2284 597

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5.2. Shear Force
Resultant shear forces are shown in Table 3.
Table 3 Shear force
SHEAR FORCE (kN)
SKEW
LOADING
IRC A IRC AA TRACKED IRC AA WHEELED IRC 70R IRC B
0 293 598 375 622 175
15 303 608 375 648 181
25 309 613 374 665 185
30 312 615 374 675 187
35 316 617 373 684 189
40 324 619 371 705 192
45 343 627 374 749 194
5.3. Torsion
The torsion moment created is indicated in in Table 4.
Table 4 Torsion
TORSION (kN-m)
SKEW
LOADING
IRC A IRC AA TRACKED IRC AA WHEELED IRC 70R IRC B
0 731 1166 807 1511 438
15 685 1001 760 1372 410
25 649 892 716 1280 388
30 634 881 695 1242 379
35 598 911 644 1176 358
40 584 901 615 1168 350
45 571 939 602 1158 342
6. COMPARISONS
6.1. IRC AA Tracked and IRC 70R
The comparison of bending moment, shear force and torsion for IRC AA Tracked and 70R loadings
has been represented in Figures 8, 9 and 10 respectively.
Figure 8 Bending moment Figure 9 Shear force

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Figure 10 Torsion
6.2. IRC AA Tracked and IRC AA Wheeled
The comparison of bending moment, shear force and torsion for IRC AA Tracked and Wheeled
loadings has been represented in Figures 11, 12 and 13.
Figure 11 Bending moment Figure 12 Shear force
Figure 13 Torsion
6.3. IRC A and IRC B
The comparison of bending moment, shear force and torsion for IRC A and IRC B loadings has been
represented in figures 14, 15 and 16.

7. Effect of Skew for Various IRC Loadings on a T-Beam Bridge Section
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Figure 14 Bending moment Figure 15 Shear force
Figure 16 Torsion
6.4. IRC A, IRC AA Tracked, IRC AA Wheeled, IRC 70R
The comparison of bending moment, shear force and torsion for IRC A, IRC AA Tracked, and
Wheeled and 70R loadings has been represented in figures 17, 18 and 19.
Figure 17Bending moment Figure 18 Shear force
Figure 19 Torsion

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7. CONCLUSIONS
Based on the analysis results following conclusions can be drawn:
 For IRC AA Tracked and 70R loadings, the values of bending moment increases by about 10% when
IRC 70R is replaced by IRC AA Tracked loading.
 For IRC AA Tracked loading, there is increase in bending moment by about 12% as the skew angle
increases from 0 to 45°.
 There is an increase of about 3 to 16% in the shear force between IRC AA Tracked and 70R loading as
the skew increases from 0 to 45°.
 There is an increase in torsion of about 20% when IRC AA tracked loading is replaced by 70R loading.
 However it is observed that there is decrease in the value of torsion for both IRC AA Tracked and 70R
loading with skew angle ranging from 0 to 45°.
 Comparison of IRC AA Tracked and Wheeled loadings show a very large variation in the values of all
three parameters i.e. bending moment, shear force and torsion.
 The variations are as large as 40% when IRC AA wheeled is replaced by Tracked loading.
 However with variation in the skew, both IRC Tracked and Wheeled shows similar curves.
 IRC A and B loading show an increase of about 10-15% in the values of bending moment with increase
in skew from 0 to 45°.
 However if IRC B is replaced by IRC A loadings, there may be increase in about 40% in the bending
moment without considering the skew.
 IRC AA Tracked and Wheeled loadings does not show any significant change in the values of shear
force with the skew angle however there is a slight increase in shear force in Tracked loading.
 Comparison of four loadings i.e. IRC A,IRC AA Tracked and Wheeled and 70R show increase in the
values of bending moment and shear force and decrease in the value to torsion with skew.
 However for IRC AA Tracked loading, first an decrease and then increase of torsion is observed as the
skew changes from 35 to 45°, thus proper care must be taken to ensure safety against torsion especially
in IRC AA Tracked loading with skew higher than 30°.
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