Life-cycle seismic performance of Q690 steel columns with H-section under various bi-directional cyclic loading paths

Abstract

The ageing effect in the life-cycle assessment should be considered for the high-strength steel structures constructed in corrosive environments and high-seismicity zones. Additionally, the structures can suffer multi-dimensional seismic excitations because of the spatial effect of ground motions. Therefore, this study aims to investigate the impact of different loading protocols on the mechanical properties of Q690 steel columns with H-section during the whole life-cycle. Firstly, numerical methods considering time-varying corrosion process are used to simulate the ageing steel columns. After that, the nonlinear hysteretic behaviors of the ageing steel columns under different loading protocols are investigated. The factor of resistance degradation (the degree of degradation of ultimate resistance) is employed to quantify the effect of loading protocols on ageing steel columns. Finally, the biaxial ultimate interaction curve considering the ageing effect and a practical design process are proposed. The findings demonstrate that the steel columns exhibit different mechanical properties under various loading protocols, and the coupling direction of bi-directional displacement loads influences the degree of degradation of ultimate resistance. As service time increases, the factor of resistance degradation of steel columns gradually reduces by up to 40%. The proposed biaxial ultimate interaction curve has acceptable accuracy. These findings emphasize the importance of employing the unfavorable loading protocols in conducting the seismic design of the steel columns in different life-cycle stages.