Identification of System Failure Modes of Steel Bridges Based on Bi-directional Evolutionary Structural Optimization

The accurate simulation and transfer of the structural failure status was the key issue of the identification algorithm for system failure modes of the steel bridges. Aimed at the accurate simulation of the possible stress redistribution of the yielded failure members under a strengthening or unloading state, and refinement of the simplified method of changing the structural status by deleting and replaying the disabled elements with a fictitious force in the structural performance analysis process, a tensile elastic-plastic material constitutive mode was proposed firstly for a better reveal of the characteristics of the steel elements in the elastic, yielding, strengthening and unloading stage. A compressive elastic-plastic material constitutive mode was considered for the reduction of yield stress. Furthermore, the bi-directional evolutionary structural optimization method was introduced to realize the automatic transfer of structural analysis state. Then, the elasticity of the tension and compressive members and the occurrence of partial unloading phenomenon were estimated by the judging criteria of stress. The material constitutive modes of the elements were converted to corresponding modes automatically in the process of identification of system failure modes, and these elements were deleted when reaching the ultimate strength. The results show that the interaction effect and the phenomenon of stress redistribution of the steel bridge components are fully considered by this method. The main failure modes of the steel bridges are identified by precise simulation and automatic transfer of structural analysis. Combined with the phase critical strength branch and bound criterion, the automatic identification program for the structural failure modes is developed, the trunk and main branch of the failure tree of the steel bridges are identified and generated rapidly. An example of a steel truss bridge is given to show that the system failure modes and the fake failure modes of the structure can be identified successfully. © 2017, Editorial Department of China Journal of Highway and Transport. All right reserved.