Progressive-models method for evaluating interactive stability of steel box girders for bridges – Extension of progressive collapse method in ship structures

Abstract The progressive collapse method (PCM) in ship structures, in which local buckling is simplified by average compressive stress-strain curves of stiffened plates, is extended to analyze the ultimate bearing capacity of steel box girders for bridges. The PCM for steel bridges is reconstructed as the progressive-models method (PMM). Subsequently, a detailed PMM used for large-scale steel box girders is proposed and implemented through a two-stage analysis, which includes the nonlinear analysis of stiffened plate using shell finite element (FE) model and the nonlinear analysis of member using beam-column theory. The PMM is demonstrated by using an example tested steel box girder of which the ultimate bearing capacity is influenced by local buckling. The traditional finite element (FE) models of the tested steel box girder, including the refined shell FE model, beam-column FE model and multi-scale FE model, are established to make a comparison and validate the proposed method. The results show that the stability of each stiffened plate in the studied steel box girder is different, among them the mid web, of which the ultimate strength is 0.65 times of the yield strength at the severe defect level, is the most susceptible to buckling. Compared with results of the test and traditional FE models, the PMM is conservative for predicting the ultimate bearing capacity. In addition, the comparison of the scale of models shows that the PMM proposed can significantly reduce the complexity of modeling and improve the computational efficiency, thus the PMM has potential practical application value. The PMM can be regarded as a new attempt for the ultimate bearing capacity analysis of large-scale steel bridge members.