Progress in the methods of analysis of restricted distortional buckling of composite bridge girders

The problem of restricted distortional buckling (RDB) is described in this paper, together with an overview of the history of progress in this area over recent years. A simple method for the distortional buckling analysis of composite steel/concrete bridge girders is then revisited here in a new form. The approach is based on the analogy between the buckling phenomenon, and that of a beam on an elastic foundation that is well known in structural engineering. In this analogy, the bottom flange of the steel joist is simulated as a beam that is resting on the elastic foundation of the web, and that is subjected to an axial force whose distribution can be determined from the bending moment diagram of the composite bridge girder. In order to present the problem mathematically and simply, a simple finite element model with two nodes and three degrees of freedom per node is developed. The method is then used to provide design curves for a range of loading patterns. Owing to the simplicity and clarity of the model, it may is useful for implementation in design practice.