Restrained distortional buckling capacity of half-through bridge girders

Steel beams with continuous and complete tension flange restraint buckle in a restrained distortional buckling (RDB) mode. Lateral buckling of half-through girders is an important example of this phenomenon because of the restraint offered by the deck, and due to the flexibility of the web in restraining the compressive flange. A numerical study was undertaken to investigate the distortional buckling behaviour of simply supported compact steel I-beams subjected to uniformly distributed load. For this purpose, a finite-element model was developed using ABAQUS. It was then used in a parametric study to simulate the distortional buckling behaviour and capacity of half-through girders, and investigate the effect of cross-section geometry and yield strengths in a RDB mode on the buckling moments of doubly-symmetric steel I-beams. Then a new formula based on the regression analyses has been proposed to predict the member moment capacities of steel I-beams subjected to RDB. The results indicate that the proposed empirical formula is properly capable of evaluating the RDB strength of steel I-beams. The results show that the proposed formula is more accurate and applicable than existing design codes.