Dynamic characteristic analysis and fatigue life estimation of steel-structure bridges under vehicle loading

Abstract

Influenced by repeated effects of vehicle loads during an operation period, a bridge structure will suffer from cyclic stress, while the corresponding fatigue damage will be generated. Therefore, it is very important to conduct on fatigue performance analysis and life assessment of a bridge during the operation period. Firstly, vehicle load spectrums and dynamic stress are determined through using field vehicle recorder and strain gauge to measure stress responses of steel-structure bridge diaphragm plates. Results show that: No.1 strain gauge was closer to the hole edge than No. 2 strain gauge, and its stress concentration was more obvious; sequence of stress values is as follows: No. 1 strain gauge > No. 2 strain gauge > No. 3 strain gauge. Then, the vehicle load spectrums are loaded into the finite element model of the steel-structure bridge (with and without struts), so stresses at holes, weld and plates are computed. Stresses at holes and plates have the similar variation tendency, but stresses at the hole are larger. Variation of stresses at welds is more complicated than other two positions when vehicles pass by. Equivalent stress amplitudes at holes, plates and other positions in the steel-structure bridge (with struts) model are less than computational results of the steel-structure bridge (without struts) model, but stress amplitudes at the weld don’t vary obviously, indicating that force at holes and plates can be effectively improved by strengthening rigidity of the diaphragm plate using struts. Finally, fatigue lives of detailed parts for the steel-structure bridge are computed. Results show that applying struts can effectively increase fatigue lives of some detailed positions, which can further improve fatigue life of the whole steel-structure bridge.