LINEAR ELASTIC ITERATION ANALYSIS OF THE ULTIMATE BEARING CAPACITY OF CFST ARCH BRIDGE UNDER INITIAL STRESS OF STEEL TUBE

A linear elastic iteration method for ultimate bearing capacity analysis of CFST arch bridges is developed using the homogeneous generalized yield function to consider the initial stress of the steel tube at the component level of CFST, and the limits of the initial stress of steel pipes were discussed with engineering examples. The test database of CFST members under axial or eccentric compression considering the initial stress of steel tube was established, and the initial stress reduction coefficients of steel tube were compared and determined. Combined with the bearing capacity correlation equation of CFST members without initial stress, the homogeneous generalized yield function of CFST members under the initial stress of steel tube is presented, which is further used to define the element bearing ratio of the CFST arch bridges representing the bearing state of the element with the initial stress being regarded as a constant load. The linear elastic iteration method was proposed for evaluating the ultimate bearing capacity of CFST arch bridges under the initial stress of steel tube on the basis of the live load coefficient adjustment method and the elastic modulus reduction method. The accuracy and efficiency of the proposed method were verified by comparing with the results of model tests and incremental nonlinear finite element methods. The proposed method was applied to a super-span railway concrete-filled steel tube arch bridge. The results show that the proposed homogeneous generalized yield function and linear elastic iteration method can evaluate the ultimate bearing capacity of CFST members and arch bridges under the initial stress of steel tube accurately with high efficiency. When the initial stress ratio is within the allowable range of the current specification, the influence of the initial stress of steel tube on the ultimate bearing capacity of arch bridges is less than 10%.