Comparative Analysis of Truss Bridges

Comparative Analysis of Truss Bridges

V. R. Shinde1

1M.E Civil-Structure Student, Department of Civil Engineering,

JSPMs Rajarshi Shahu College of Engineering Tathawade, Pune-411033, India

Prof. A. S. Patil2

2Assistant Professor,

Department of Civil Engineering, Engineering, JSPMs Rajarshi Shahu College of Engineering Tathawade, Pune-411033, India

Prof. U. A. Mahadik3

3Assistant Professor, Department of Civil Engineering, Engineering, JSPMs Rajarshi Shahu College of Engineering Tathawade,

Pune-411033, India

AbstractA bridge must be designed to safely resist all loads and forces that may reasonably occur during its life. These loads include not only the weight of the structure and passing vehicles, but also load from natural causes, such as wind and snow. The loads may act individually but more commonly occur as a combination of two or more loads applied simultaneously. The project discussed analysis and design of steel truss bridge, the bridge is 70m long and 7.5m width and 6 m high, the spaces between the trusses in the roof are various, from the beginning we leave space that equal 0.5 m. The analysis was done by staad pro program. The project studied maximum axial forces, shear forces, torsional values & moment.

KeywordsPratt Truss Bridge, Howe, Warren, Staad Pro v8i.

1. INTRODUCTION

   A bridge is a means by which a road, railway or other service is carried over an obstacle such as a river, valley, and other road or railway line, either with no intermediate support or with only a limited number of supports at convenient locations. Bridges range in size from very modest short spans over, say, a small river to the extreme examples of suspension bridges. The main advantages of structural steel over other construction materials are its strength and ductility. It has a higher strength to cost ratio in tension and a slightly lower strength to cost ratio in compression when compared with concrete. The stiffness to weight ratio of steel is much higher than that of concrete. Thus, structural steel is an efficient and economic material in bridges.

   1. Objectives of the Present Study

      1. To determine the reactions and member forces. The methods used for carrying out the analysis with the equations of equilibrium and by considering only parts of the structure through analyzing its free body diagram to solve the unknowns.

      2. Create a structural optimization algorithm capable of finding the various reactions, when subjected to various load combinations and design constraints.

      3. Comparing and analyzing the various constraints of different truss bridges models.

   2. Various Truss Bridges Pratt Truss Bridge

      This type of truss has diagonal members that slope down towards the Centre, this type is completely differing of the Howe truss. The inner diagonals of the truss are having tension whereas compressive force acts upon vertical members. This truss was invented by Caleb Pratt and Thomas Pratt in 1844. This type is practical for spans up to 75 metres.

      Warren Truss Bridge

      It was patented by James Warren in 1848. It consists of longitudinal members joined by Cross members that are angled. Its forms alternatively inverted equilateral triangles ensure that no strut, tie or beam is subjected to bending or torsion strain nature forces.

   3. Loads on Truss Bridges Dead Load

   The mass of the equipment load that has constant magnitude and attached to the structure permanently represents the dead load. It consists of the main truss weight the floor beams or girder weight and stringer of the floor system the dead load that acts on the member should be assumed before the design of the member. A member of structure should be designed in such a sequence that to as great an extent as practicable the weight if each member designed is a portion of the dead load carried by the next member to be designed.

   Live Load

   There are mainly four types of loadings whose usage depends on the purpose, location, and properties of the bridge. There are following type of loadings as listed:

   IRC Class 70R Loading. IRC Class AA Loading IRC Class A Loading IRC Class B Loading

2. PROBLEM STATEMENT

   Analysis of steel truss bridge, the bridge is 70m long and

   7.5 m width and 6 m high, the spaces between the trusses in the roof are various, from the beginning leave space that equal

   0.5 m, after that divided all spaces in 10 segment the length of each one equal 7m in the floor.

   Project used the straight member and, in the beginning, and the end connected by welding point formed triangles, and this member affected by compression or tensile force, about the moment the same mean of torque is excluded in the trusses, Moreover, assume all the joint in the trusses is pin.

   Fig. 1 Pratt Truss Bridge Model

   Fig. 2 Warren Truss Bridge Model

   Fig. 3 Howe Truss Bridge Model

3. RESULT & DISCUSSION

   1. Comparative Results of Shear Force (in KN)

      Fig 4 Shear Force KN

   2. Maximum Displacement (in mm)

      Fig 5 Max Displacement mm

   3. Torsional Values (in KNm)

      Fig 6 Torsion KNm

   4. Support Reaction (KN)

      Fig 7 Support Reaction KN

   5. Maximum Moment (KNm)

      Fig 8 Moment KNm

4. CONCLUSION

This project discussed the analysis and design of steel truss bridge, the bridge is 70m long and 7.5 m width and 6 m high, the spaces between the trusses in the roof are various, from the beginning by leaving space that equal 0.5 m, divided all spaces in 10 segment the length of each one equal 7m.

1. Maximum shear force value is for howe truss bridge which is 485.763 KN

2. Maximum displacement is 690.141 mm for warren truss bridge. This is 15% more than pratt truss bridge and 5% more than howe truss bridge.

3. Torsional value for pratt truss bridge is 30% more than howe truss & 22% more than warren truss bridge.

4. Maximum support reaction is 4946.319 KN for howe truss bridge.

5. Maximum moment occurred for warren truss bridge which is 1029.88 KNm. This value is 25% more than pratt truss bridge.

REFERENCES

1. T.Pramod Kumar, G.Phani Ram (July 2015) Analysis and Design of Super Structure of Road cum Railway bridge across Krishna river.

2. IRC: 6-2014 Section II (Loads and Stresses) standard specifications and code of practice for road.

3. IRC: 21 Section III Cement Concrete (plain and reinforced) standard specifications and code of practice for road bridges.

4. Karthiga P, Elavenil S, Kmp D. A Comparison of Road Over Bridge And Rail Over Bridge. The IUP Journal of structuralengineering.

5. Huili Wang, Hao Gao, Sifeng Qin, "Fatigue Performance Analysis And Experimental Study Of Steel Trusses Integral Joint Based On Multi- Scale Fem", Engineering Review, Vol. 37, Issue 3, 257- 262, 2017.

6. T. J. Jayakrishnan , Lekshmi Priya R., "Analysis of Seismic Behaviour of a Composite Bridge using ANSYS", International Journal of Engineering Research & Technology (IJERT), Vol. 6 Issue 05, May 2017.

7. K.Suganthi, K. Sachidanandam, "Behavioural Analysis of Lattice Bridge by Using ANSYS", International Journal of Innovative Research in Science, Engineering and Technology, Vol. 5, Issue 6, June 2016.

8. Jianing Hao, "Natural Vibration Analysis of Long Span Suspension Bridges", 5th International Conference onCivil Engineering and Transportation, ICCET, 2015.

9. Dongdong Zhanga, Yaru Lvb, Qilin Zhaoc, Feng Lia, Development of lightweight emergency bridge using GFRPmetal composite plate-truss girder

10. Alpesh Jain, Analysis of a bridge structure with four different material using ANSYS software

11. Yamaguchi, Post-member-failure conduct of a truss bridge by static analysis and the dynamic evaluation