Assessment Of The Structural Behaviour Of Girder
Bridge Deck With The Range Of 00-550Skew Angle Ruchi A. Thakur1, Prof. Sanjay K. Bhadke2
1 M. Tech Student, Department Of Civil Engineering, Tulsiramji Gaikwad- Patil College Of Engineering And Technology Nagpur
India. 2 Assistant Professor, Department Of Civil Engineering, Tulsiramji Gaikwad- Patil College Of Engineering And Technology
Nagpur India.
Abstract— — There is a wide growth in number of skew bridges or flyovers; mostly in urban and developing cities. Due to
ease in construction and constraints of space availability in cities; highway interchanges or grade separators, the skewed
slab bridges are adopted instead of conventional straight slab bridges. The analysis of skew slab is more complicated as
compare to straight slab due to variation in skew angle. In this study Six different cases of models with skew angles
00,150,250,350,450,550 with span of 30m and 3 lane of skew bridge are to be considering for analysis. As per IRC 6-2017 load
and load combination is consider. On the basis of live load, and dead load calculating the maximum bending moment,
maximum shear force, torsion and deflection and for this software package STADD pro v8i based on FEM has been used.
Keywords— Analysis, finite Element, Skew Angle, Dead load, Live Load.
I. INTRODUCTION
Skew bridges are common at river passage, highway and other grade changes when skewed geometry is
extremely important due to restrictions in space. there is a growing demand for skewed RC beam bridges
because the necessities for complex intersection and also the troubles with space constraint in urban and
metro city areas arise. When roadway alignment changes don't seem to be feasible then the Skewed
bridges are useful or due to the topography of things to maintained economic and moreover at particular
areas someplace environmental impact are often an issue. so on supply high speeds and more safety
necessities of the traffic, modern highways are to be straight as far as possible and this has required the
provision of rising number of skew bridges. If a road alignment crosses a river or other obstruction at an
inclination different from 90°, a skew crossing is additionally essential. The inclination of the centre line
of Roadway to the centre line of river just in case of a river bridge or other obstruction is termed the
skew angle. The analysis and elegance of a skew bridge are rather more complicated than those for a
typical bridge. The analysis and elegance of bridge decks complicated if skew is present. Bridges with
big angle of skew can have a substantial effect on the behaviour of the bridge mainly within the several
ranges of spans. an oversized number of research studies have examined the performance of skewed
highway bridges. However, there don't seem to be any detailed guidelines addressing the performance of
skewed highway bridges. Numerous constraints affect the response of skewed bridges which make their
behaviour complex. Therefore, there's a desire for extra research to figure the effect of skew angle on the
performance of beam bridges. Skew during a bridge may result from several factors, including natural or
manmade obstacles, intricate intersections, space limitations, or mountainous terrain.
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II. OBJECTIVE OF STUDY
1. To study the effect of different skew angles.
2. To study the effect various types of loads as per IRC 6:2017
3. Develop the mathematical model to evaluate the effect of various parameters such as skew angle on
the behavior of skewed bridges.
4. To observe the effect of skew on maximum Live load, Shear force, and Torsion and effect of
skewness directly on design parameters i.e. bending moment, shear force, and torsion.
5. Test a real skewed bridge to understand its behavior of skewed bridges and use the results for
determination of safe and economical skew angle.
III. CODAL PROVISION
1. IRC:6-2017, “Standard Specifications and Code of Practice for Road Bridges Section : II Loads and
Load Combinations (Seventh Revision)”, Indian Roads Congress, New Delhi.
The provisions used from the above mentioned codes are as follows:
i. Clause no.203 mainly discusses about the dead load calculations of the bridges.
ii. Clause no.204 mainly discusses about the live load calculations of the bridges.
TABLE 1.1
COMBINATION OF LIVE LOAD
Sl.
No.
Carriageway Width
(CW)
Number of Lanes for
Design Purposes Load Combination
1 Less than 5.3 1
One lane of Class A considered to occupy 2.3m. The
remaining width of carriageway shall be loaded with
500 kg/m2
2 5.3m and above but less
than 9.6m 2 One lane of Class 70R OR two lanes for Class A
3 9.6m and above but less
than 13.1 3
One lane of Class 70R for every two lanes with one
lanes of Class A on the remaining lane OR 3 lanes of
Class A
4 13.1m and above but less
than 16.6m 4
One lane of Class 70R for every two lanes with one
lane of Class A for the remaining lanes, if any, OR
one lane of Class A for each lane.
5 16.6m and above but less
than 20.1 5
6 20.1m and above but less
than 23.6 6
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a) Clause no. 204.3 mainly discusses about Combination of Live Load in table 2 considered 3 lane for design are
mention below
Fig.1 IRC:6-2017 Live Load Combination Case I
Fig.2 IRC:6-2017 Live Load Combination Case II
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ISSN NO: 0022-1945
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IV. MODELING
Six skew angle box girder bridge deck which is starting from 00 to 550 as shown in following figures are modeled and analyzed
using STAAD Pro v8i software.. A comprehensive review of the steps to be followed to perform analysis in STAAD Pro v8i is
also studied. Finally the results obtained after analyzing the skew angle box girder bridge deck are presented and a comparison of
results in form of maximum Shear Force, Bending Moment, Deflection, Torsion and Support Reaction.
A. Skew angle Box Girder Bridge
The skew angle box girder bridge deck taken for analysis in STAAD Pro v8i is as follows and the size of box girder bridge is
30m x 13.5m:
Fig 1.1 Plan for 00 Skew Angle Fig1.2 Isometric View for 00 Skew Angle
Fig.1.3 Plan for 250 Skew Angle Fig. 1.4 Isometric View for 250 Skew Angle
Fig.1.5 Plan for 550 Skew Angle
Fig.1.6 Isometric View for 550 Skew Angle
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B. Details of Box Girder Bridge
The six skew angle box girder bridge deck selected for analysis are discussed in this section. It is important to note that all the box
girder bridge deck have same dimension i.e. 30 m x 13.5 m in X-Z plane and moreover the internal/outer girder of box girder
bridge deck having equal cross section.
TABLE 1.2
Properties of Box Girder Bridge
Length of Bridge 30 m
Width of Single Lane 3.5 m
Nos of Lanes 3 Nos
Clear Width of Roadways 10.5 m
Kerb Width 0.5 m
Width of Cantilever Bridge 1.5 m
Thickness of Top Slab 0.25 m
Thickness of Wearing Coat 0.075 m
Clear Width of Carriageway 10.5 m
Nos of Box Girders 3 Nos
Nos of Longitudinal Girders 4 Nos
Depth of Girder 1.25 M
Thickness of Girder 0.35 m
Thickness of Bottom Slab 0.2 m
Over All Length 11.7 m
Thickness of Kerb 0.3 m
Grade of Concrete M 35
Grade of Concrete Fe 415
Modular Ratio 10
Density of Concrete 25 kN/m3
Density of Wearing Coat 22 kN/m3
C. About STAAD PRO
This project is mostly based on modelling & analysis of STAAD Pro (v8i) software. Any type of body which is stable in a given
loading can be considered as structure. So first find the skeleton of the structure, whereas analysis is the assessment of what are
the type of loads that deeds on the bridge and calculation of Shear Force, Bending Moment, Deflection, Torsion and Support
Reaction comes under analysis stage. To calculate Shear Force, Bending Moment, Deflection, Torsion and Support Reaction of a
complex loading bridge it takes about a numbers of days. So when it approaches to the Box girder bridge with moving load it will
take a couples of week. Staad pro is a powerful tool which does this job in just few minutes or in hours. Staad pro is a best
substitute for bridge analysis.
D. Analysis using STAAD Pro v8i
To perform analysis in STAAD Pro v8i following steps must be followed:
i. Loads & Load combinations
ii. Analysis command
iii. Geometric Modeling
iv. Sectional Properties and Material Properties
v. Supports : Boundary Conditions
V. RESULT AND DISCUSSION
After STAAD PRO Analysis the results are obtained and the presented in expressions of critical structural response such as
Shear Force, Bending Moment, Deflection, Torsion and Support Reaction in the Box Girder Bridge deck Models due to the
applied moving vehicle load. Hence, the comparison made between all skew angle Box girder bridges by using maximum
Shear Force, Bending Moment, Deflection, Torsion and Support Reaction.
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ISSN NO: 0022-1945
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A. Comparisons of Various Skew Angle for Critical Stress
TABLE I
1) Total Load Shear Force percentage variation (Outer)
GRAPH I
1) Total Load Shear Force percentage variation (Outer)
TABLE II
Length (m) Skew Angle
15 25 35 45 55
0 0.00% 0.00% 0.00% 0.00% 0.00%
2.5 -0.19% -0.30% -0.42% -0.54% -0.63%
5 -0.08% -0.13% -0.19% -0.24% -0.28%
7.5 -0.05% -0.07% -0.10% -0.13% -0.16%
10 -0.03% -0.04% -0.06% -0.07% -0.09%
12.5 -0.01% -0.02% -0.03% -0.03% -0.04%
15 0.00% 0.00% 0.00% 0.00% 0.00%
17.5 0.01% 0.02% 0.03% 0.03% 0.04%
20 0.03% 0.04% 0.06% 0.07% 0.09%
22.5 0.05% 0.07% 0.10% 0.13% 0.15%
25 0.08% 0.13% 0.18% 0.24% 0.27%
27.5 0.18% 0.30% 0.42% 0.54% 0.62%
30 0.00% 0.00% 0.00% 0.00% 0.00%
2) Total Load Deflection percentage variation (Outer)
Length (m) Skew Angle
15 25 35 45 55
0 2.41% 5.19% 8.51% 12.78% 18.91%
2.5 2.69% 5.53% 8.91% 13.28% 19.54%
5 2.98% 5.88% 9.34% 13.80% 20.20%
7.5 3.28% 6.25% -0.99% 3.57% -0.67%
10 4.61% 8.51% 13.14% 19.12% 27.70%
12.5 -56.39% -52.38% -47.60% -104.57% -95.73%
15 -19.56% -34.11% -51.42% -73.75% -105.80%
17.5 -10.55% 96.26% 80.64% 60.50% 39.73%
20 -8.03% -13.36% 29.04% 25.54% 13.79%
22.5 -2.39% -5.78% -9.81% -15.01% 8.49%
25 -4.13% -4.43% -7.39% -11.20% 8.20%
27.5 -3.36% -5.29% -7.58% -10.53% -14.78%
30 -3.46% -5.36% -7.62% -10.54% -14.72%
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GRAPH II
2) Total Load Deflection percentage variation (Outer)
TABLE III
Skew Angle
15 25 35 45 55
250% 450% 700% 1000% 1550%
3) Total Load Torsion percentage variation (Outer)
GRAPH III
3) Total Load Torsion percentage variation (Outer)
TABLE IV
Skew Angle
15 25 35 45 55
0.03% 0.25% 0.67% 1.31% 2.17%
4) Total Load Support Reaction percentage variation (Outer)
GRAPH IV
4) Total Load Support Reaction percentage variation (Outer)
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ISSN NO: 0022-1945
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TABLE V
5) Total Load Bending Moment percentage variation (Inner)
GRAPH V
5) Total Load Bending Moment percentage variation (Inner)
TABLE VI
Length (m) Skew Angle
15 25 35 45 55
0 19.62% 35.07% 54.10% 79.31% 115.91%
2.5 19.95% 35.65% 54.99% 80.63% 111.57%
5 20.28% 36.25% 52.74% 75.62% 113.46%
7.5 17.39% 30.40% 50.41% 76.92% 61.40%
10 22.47% 40.17% 47.07% 32.01% 73.93%
12.5 -37.05% -19.02% 3.19% 32.62% -22.48%
15 60.04% 107.32% 25.44% -13.77% -90.37%
17.5 -84.28% -157.00% -120.70% -213.01% -293.63%
20 77.22% 48.82% 112.88% 80.79% 225.83%
22.5 29.11% 22.57% 52.19% 83.14% 52.03%
25 18.93% 44.46% 33.94% 20.00% -0.23%
27.5 -6.58% -11.77% -18.15% -26.61% -38.89%
30 -6.55% -11.70% -18.05% -26.46% -38.68%
6) Total Load Shear Force percentage variation (Inner)
GRAPH VI
6) Total Load Shear Force percentage variation (Inner)
Length (m) Skew Angle
15 25 35 45 55
0 17.25% 29.95% 44.37% 61.19% 79.91%
2.5 16.04% 27.35% 39.50% 52.20% 63.26%
5 12.42% 19.68% 25.62% 29.06% 19.36%
7.5 -38.85% -80.49% -154.69% -306.22% -458.94%
10 28.77% 55.16% 85.84% 107.61% 158.87%
12.5 19.39% 28.89% 43.53% 67.95% 86.92%
15 15.84% 30.27% 42.92% 54.01% 62.21%
17.5 12.80% 19.65% 28.91% 32.08% 23.44%
20 11.16% 13.11% 10.02% 6.89% -5.46%
22.5 -9.21% -12.38% -15.99% -37.05% -77.46%
25 33.08% 78.23% 154.78% 220.39% 260.90%
27.5 14.76% 21.86% 26.49% 27.22% 20.06%
30 3.67% 4.39% 3.30% -0.73% -10.54%
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TABLE VII
Length (m) Skew Angle
15 25 35 45 55
0 0.00% 0.00% 0.00% 0.00% 0.00%
2.5 0.17% 0.36% 0.64% 1.04% 1.60%
5 0.08% 0.16% 0.29% 0.46% 0.71%
7.5 0.05% 0.09% 0.16% 0.26% 0.40%
10 0.03% 0.06% 0.10% 0.16% 0.23%
12.5 0.02% 0.03% 0.05% 0.08% 0.12%
15 0.01% 0.01% 0.02% 0.02% 0.02%
17.5 0.00% -0.01% -0.02% -0.04% -0.08%
20 -0.01% -0.03% -0.06% -0.11% -0.19%
22.5 -0.02% -0.06% -0.12% -0.21% -0.34%
25 -0.05% -0.12% -0.23% -0.39% -0.63%
27.5 -0.11% -0.27% -0.52% -0.89% -1.43%
30 0.00% 0.00% 0.00% 0.00% 0.00%
7) Total Load Deflection percentage variation (Inner)
GRAPH VII
7) Total Load Deflection percentage variation (Inner)
TABLE VIII
Skew Angle
15 25 35 45 55
0% 50% 50% 750% 150%
8) Total Load Torsion percentage variation (Inner)
GRAPH VIII
8) Total Load Torsion percentage variation (Inner)
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ISSN NO: 0022-1945
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TABLE IX
Skew Angle
15 25 35 45 55
-4.51% -7.85% -12.38% -28.41% -18.35%
9) Total Load Support Reaction percentage variation (Inner)
GRAPH IX
9) Total Load Support Reaction percentage variation (Inner)
VI. CONCLUSIONS
1. Variation Bending Moment & Shear Force for skew angle lies between 150 to 550 are compared with
zero degree skew angle, where as for skew angle greater than 450 the Bending Moment & Shear
Force value increases more than 50% for different loading combinations.
2. Whereas, the variation in Deflection increases with increasing skew angle as compared to zero skew
angle, for various loading combinations.
3. Whereas, the variation in Torsion & support reaction also increases with increasing skew angle as
compared to zero skew angle, for various loading combinations.
4. The observed value for various combinations of skew angle includes loading that for skew angle lies
between 00 to 350 are structurally safe and economical for same load conditions.
ACKNOWLEDGMENT
I would like to express utmost gratitude to my co-author Asst. Prof. Sanjay K. Bhadke for his support and
guidance provided in articulation of this paper.
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