Distortion induced fatigue of web-gap details, a parametric study

Abstract

Prior to the mid 1980’s, bridge girders were often constructed with a gap between the end of the connection plate and the flange in tension. This practice was stopped due to early fatigue damage being developed in the web-gap region due to out-of-plane distortion. Several hundreds of bridges have suffered from this type of damage and more are yet to come. The aim of this paper is to get a better understanding of distortion induced fatigue through the study of deformation and contour plots together with a parametric study of some key parameters. The improved understanding will help engineers to identify bridges prone to this type of damage and to choose a suitable retrofitting procedure for damaged bridges. The results from this paper indicates that the distortion induced stresses in the lower web-gap are mainly caused by rotation of the cross-section. Meanwhile, the ones in the upper web-gap are mainly caused by the deformation of the concrete deck and the uneven deflection between the longitudinal girders. Furthermore, web-thickness and the distance from the cross-bracing to the supports were among the parameters with highest influence on the web-gap stresses.