Distortion-induced stress investigation of double angle stringer-to-floorbeam connections in railroad bridges

Research has shown that double angle stringer-to-floorbeam connections in riveted railway bridges are susceptible to fatigue cracking caused by secondary, distortion-induced stress. This stress, caused by stringer end rotation is not easily calculable, therefore more detailed analysis techniques are needed to quantify connection behavior. The present study was initiated to determine the effect that connection parameters: (1) gage length of the outstanding angle leg, (2) angle depth, (3) angle thickness, and (4) stringer length have on moment-rotation behavior and stress concentrations from a typical 286,000 pound railcar load. Seventy-two unique double angle connection configurations were investigated using 3D and 2D finite element analysis software. Maximum principal stress in the connection angle was investigated in each analysis case and a subsequent stress prediction equation was developed through linear regression analysis. The proposed equation is a function of connection parameters and provides an easily calculable and effective method to predict the magnitude of stress range in connection angles. This facilitates fatigue life evaluation without the need for rigorous analysis.