Research On Fatigue Performance Of Welded Girders With Trapezoidal Corrugated Webs

Welded girders with trapezoidal corrugated web is a kind of new welding beam structure.Due to its excellent mechanical properties,it has been developed rapidly.Study on the fatigue performance,which has important significance for the practical application in engineering.Proceeded from the fatigue theory of welding structure,three levels of fatigue methods were studied,which were nominal stress method,hot-spot stress method and equivalent structure stress method.The application strategy of the equivalent structure stress method was particularly concerned.Then the three levels of fatigue methods were used to evaluating the fatigue phenomenon of welded girders with trapezoidal corrugated web.The main research work and conclusions includes:(1)Researched on the basic theory of equivalent structure stress method.Given the approach of element node force change to local coordinate system.Realized the numerical solution method of the element line load matrix.Studied the finite element model based on SHELL element of T welded joints,and compared the calculation result with experimental result,then given the modeling approach of equivalent structure stress method fatigue assessment for T welded joints.Longitudinal structural stress construct approach was proposed to analyzing the fatigue life of non-load-carrying T welded joints with longitudinal load.(2)Fatigue failure location was given by research of substantial experimental result of welded girders with trapezoidal corrugated web.FEA models of four point loading experimental specimen were established based on several characterization stress methods(nominal stress method,hot-spot stress method,equivalent structure stress method),which was aimed at studying characterization stress distribution,analyzing crack initiation location,evaluating fatigue life and comparing the effect of different fatigue assessment method.Then three point loading experimental result of welded girders with trapezoidal corrugated web was used to verification and analysis with the equivalent structure stress method.Consequently,equivalent structure stress curve performed severe corrugated characteristics which could forecast crack initiation location accurately and calculate fatigue life reliably,which was recommended as the control parameter for fatigue evaluating of welded girders with trapezoidal corrugated webs.(3)Chose the corrugated numbers of web as the influencing factors of fatigue performance for welded girders with trapezoidal corrugated web.Built FEA model with different corrugated numbers of web,the variable numbers witch were designed as 2n,2n+l and 2n±0.5.Calculated equivalent structure stress of local weld toe for each girder respectively with four point load and three point load.Normalized the equivalent structure stress result of different girder.Compared the normalized result and analyzed the impact by the change of the corrugated numbers of web for the fatigue performance.The results indicated that the fatigue life was enhanced with the increased quantity of corrugated numbers of web.For three point loading,the corrugated numbers of web was recommended as 2n+1.For four point loading,the corrugated numbers of web was recommended as 2n+1 or 2n±0.5,and the corrugated numbers of web between the load location was recommended as integer.,In this paper,the research on the fatigue performance of welded girders with trapezoidal corrugated web could guidance the design,manufacture and assembly of the structure,which has great significance to expand its application field.