Evaluation of Method to Prevent Cracking at Diaphragm/Plate Girder Connections
- T. J. Wipf, L. F. Greimann, A. H. Khalil, D. Wood
- Final report, Iowa Department of Transportation…
Some of the Iowa Department of Transportation’s (Iowa DOT) welded continuous steel plate girder bridges have developed cracks in the negative moment regions at the web gaps with diaphragm connection plates. A method to prevent cracking in bridges with X-type or K-type diaphragms had been suggested by the Iowa DOT, which consists of loosening the bolts in some of the connections between the diaphragm diagonals and the connection plates. The objective of the paper is to investigate the effectiveness of this method in X-type diaphragm bridges. The research was sponsored by and performed in cooperation with the Iowa DOT. The experimental investigation included selecting and testing three bridges: two skew and one non-skew. The finite element method was used to choose the testing locations at which strain gages and displacement transducers were attached. The response at these locations was collected before and after implementing the method. Bridges were subjected to truck loading in different lanes with different speeds. The preliminary results show that the behavior of the web gaps in X-type diaphragm bridges was greatly enhanced by the suggested method as the stress range and out-of-plane distortion were reduced by at least 42% at exterior girders. Based on the results of the study, it is recommended to implement the method in bridges with Xtype diaphragms.