Behavior Analysis And Fatigue Evaluation Of Existing Steel Bridges

With the rapid development of economic, the pressure of rail transport becomes more and more large. Measures such as running heavy haul train on existing railway lines have been launched to increase the transport capacity. But running heavy haul train will shorten the life of bridge, and amount of disease have been detected in the existing bridges. Therefore, it is important to repair diseased bridge for the safety of the trains.This article is provided by the scientific research development program Technology research on defects treatment and detection evaluation of the existing steel bridges under heavy haul train (2011G016-C). A through type continuous steel trussed girder (3×108m) on the Changdong Yellow River Bridge was selected as the prototype, and a three-dimensional model was established by the finite element analysis software Midas and ANSYS to study the behavior and fatigue performance under the heavy haul train. The major work and conclusions are as follows.(1)The behavior performances of steel truss were analyzed for static strength, fatigue strength and overall stability. A steel truss plane and space models are established by the Midas software. The structure behavior were calculated under the dead load, design-live load, UIC live load and30theavy haul train, some conclusions indicate that when the girder runs under the30theavy load combined with other load, part of the main truss rod can not meet the specification requirements and need to be reinforced.(2)The impact of the bridges disease on the forces of structural member was studied; the conclusion is that the actual pier settlement and bearing defects have a huge impact on steel truss main truss rod axis force, and less impact on the axial force of other members. Bearing jacking steps are determined by numerical simulation. By bearing jacking the bearing are recovered. And the measured results and finite element analysis results agree well.(3) The dynamic response of steel truss girder when a train crossing the bridge were analyzed using ANSYS software. In the analysis of this paper, concentrated load was used to simulate vehicle action. The dynamic response of the steel truss is analyzed under the action of three different axle load vehicle which are C64K, C70and C80, the results show that the dynamic deflection of structure and stress increase with the increasing of vehicle axle load, but the vertical acceleration do not play a strictly proportional relationships with vehicle axle load; And in low speed range, changes of dynamic response of the structure is not obvious with the increase of speed of vehicles crossing the bridge;(4) By analyzing the stress time curve of lower chord caused by a train bridge, the fatigue life of this steel truss bridge was calculated by rainflow method, which is about125years.