Preventing Cracking at Diaphragm/Plate Girder Connections in Steel Bridges: Fid-Bau Portal

Preventing Cracking at Diaphragm/Plate Girder Connections in Steel Bridges

The primary objective of this study was to investigate a retrofit method proposed by the Iowa DOT to prevent web cracking. This method consists of loosening the bolts at selected connections between the diaphragm diagonals and the connection plates, which are not welded to the tension flange. The scope of the investigation included studying the cracking problems occurring at the diaphragm/plate girder connections in negative moment regions of continuous plate girder bridges, identifying existing methods of crack prevention/control, and comparing the out-of-plane distortion of the web for X-type and K-type diaphragms. During the early stages of the study, a comprehensive literature review was conducted. In the experimental phase of this study, the proposed method was evaluated for potential field use. After conducting a preliminary field and theoretical investigation of the method, field tests on five bridges, with two transverse bracing systems, were conducted. Three bridges having X-type diaphragms were tested: one non-skew bridge and two skew bridges. The other two bridges, one non-skew and one skew, had K-type diaphragms. During tests, strains and displacements at various locations were measured to assist in evaluating the effect of the proposed method on the local and global behavior of these bridges. Loaded test trucks, provided by the Iowa DOT, as well as ambient traffic, were utilized.