Cracking of Longitudinal Diaphragms in Long-Span Cable-Stayed Bridges

Abstract

Longitudinal diaphragms are frequently used in steel box girders of long-span cable-stayed bridges to obtain desirable performance of steel girders. Field examination, however, reveals that premature cracking may often occur in the diaphragms after only a few years of service. Using the Runyang cable-stayed bridge (RCB) in China as an example, this paper presents an investigation of the cracking damage of longitudinal diaphragms, in which the pattern, location, and propagation of cracks are evaluated according to nondestructive field tests. To further look into the failure mechanism, a multiscale finite-element (FE) model of the RCB is developed, and the influence of diaphragms on local and global behavior of the bridge is investigated. In conjunction with a comprehensive vehicle load model developed using traffic information from a toll station, probabilistic FE analyses are performed, and the predicted fatigue lives of specific details are obtained and compared with those in field examination, where good agreement is observed.