Research And Experiment On Fatigue Of Steel Truss Girder Welding Integral Joint Of Long-span Double-layer Highway Suspension Bridge

Since the welding integral joint was firstly used in Sunkou Yellow River Bridge,a number of long-span steel bridges with integral joint have been built in China.Wuhan Yangsigang Yangtze River Bridge is the longest steel truss double decker highway suspension bridge,which is under construction and has a span of 1700 meters.The welding integral joint is suitable for manufacturing in factories and assembling at the construction site,meanwhile,it could ensure the quality of steel bridges and shorten the construction period.Due to the complexity of the welding seam in integral joint,it is very difficult to assess the fatigue performance of integral joint accurately by using finite element analysis;therefore,it is necessary to conduct the fatigue test of integral joint.Taking the Wuhan Yangsigang Yangtze River Bridge from an engineering background,this paper uses finite element simulation and a fatigue test to assess the fatigue performance.Firstly,the finite element model of Wuhan Yangsigang Yangtze River Bridge is built by finite element software Midas/Civil.Then Chinese standard fatigue load is used in the moving load analysis to choose the study object whose stress range is bigger than the other joints in the bridge.Secondly,according to the BS5400 specification and Miner Rule,this article calculates the selected joint equivalent fatigue load,which is equal to 2,000,000 times fatigue load.Finally,fatigue test is conducted to the test model.Static load is applied to the model per 200,000 times,meanwhile,observe the fatigue critical areas on the model to find the fatigue cracks.After 2,000,000 times fatigue load,the model is as good as the 0 time,and the measured stress closely matches the theoretical value.This indicates that the result of the fatigue test is reliable.The anti-fatigue performance of Wuhan Yangsigang Yangtze River Bridge meets the design requirements.