Welded‐Versus Bolted‐Steel I‐Diaphragms in Composite Bridges

Abstract

In the design of composite bridges, the North American practice either ignores or minimizes the contribution of transverse disphragms to the transverse load distribution; this results, among other disadvantages, in heavier longitudinal steel girders than necessary as well as in the loss of headroom. Recent tests have shown that when transverse steel I‐diaphragms are rigidly joined in a welded connection to the longitudinal steel girders, the wheel loads on the bridge become distributed in an orthotropic manner. The influence of bolted and welded transverse I‐diaphragms (to the longitudinal girders) on the response of composite bridges are investigated. Several composite bridge models were tested; repeated load tests were also conducted to examine the fatigue resistance of the longitudinal steel girders as influenced by the welding attachments. The experimental results are compared to theoretical ones based on the finite element method. It is concluded that the response of welded‐diaphragm composite bridges is superior to that of bolted‐diaphragm bridges and that this construction technique be used to rehabilitate existing composite bridges and/or improve their load rating.