Assessment Of The Structural Behaviour Of Girder Bridge ...

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.

[email protected]

[email protected]

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.

Journal of Interdisciplinary Cycle Research

Volume XII, Issue V, May/2020

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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


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


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.


than 20.1 5


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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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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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)


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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TABLE V

5) Total Load Bending Moment percentage variation (Inner)

GRAPH V

5) Total Load Bending Moment percentage variation (Inner)

TABLE VI


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)


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


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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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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