Web design of box girders concrete bridges

The purpose of this paper is to introduce a new design approach including the Ultimate Limit State (ULS) due to fatigue. Different criteria for the design of those webs are compared by means of shear-bending moment interaction diagrams, as an attempt to identify the most realistic one. An experimental investigation was undertaken with the purpose of verifying the validity of the newly developed approach. The following failure modes were considered: excessive plastic deformation of the stirrups, crushing of the compressed struts and failure of the stirrups due to fatigue. The experimental results showed good agreement with the results of the proposed approach. Furthermore, the tests revealed new aspects of the fatigue behavior: the failure of the stirrups due to fatigue occurred in stages, one at a time in a gradual manner. In all cases, failure took place near the connection between the web and the bottom flange.