Seismic fragility estimates of steel diagrid structure with performance-based tests for high-rise buildings

Abstract

During seismic performance-based design for building structures, the accuracy of limit states criteria is directly related to its real damage state and retrofitting measures after the earthquake. As a new type of structures, diagrid structure has a special way of bearing force. Firstly, in order to accurately estimate the deformation capacity and energy dissipation mechanism under horizontal loads, four plane specimens of steel diagrid structure are designed and seismic performance-based tests under horizontal quasi-static cyclic load are carried out. Secondly, according to the yield strength and horizontal ultimate deformation capacity of diagrid structure, combined with pushover method, the limit state values of four performance levels of diagrid structure are determined. Finally, the seismic fragility of a diagrid structure for high-rise building is analyzed. The results suggest that the bottom tilted columns have obvious deformation visible to the naked eye before failure, and some failure warnings can be given in advance. It is difficult to realize the “beam hinge” mechanism in diagrid structure, and the cumulative damage of “column hinge” is its main failure mode. The bottom tilted column is the first place where plastic hinge occurs. In addition, the recommended value of inter-story drift ratio for judging the yield of steel diagrid structure is 1/128 by these experimental results, and the recommended value of inter-story drift ratio for collapse resistance is 1/85. Based on these experimental results, the probability of diagrid structure in each performance state can be estimated reasonably and effectively.