Mechanical characteristics of circular hollow section damper under bidirectional cyclic loading

Abstract

During earthquake events, hysteretic dampers installed on the elevations composed of the columns and beams of structural frames can resist forces in any direction other than the in-plane direction because of the three-dimensional behavior of buildings and the interrelationship between the dampers and the adjacent members. Circular hollow section dampers (CHSDs), which form a type of steel hysteretic dampers, can be employed as seismic devices because they provide equal structural performance in any horizontal direction according to the geometrical characteristics of the cross-sectional shape. However, the cumulative hysteretic characteristics of CHSDs for multidirectional behavior remain unelucidated; therefore, an empirical review is needed. This study experimentally analyzed the cumulative hysteresis behavior of a CHSD repeatedly loaded sequentially in two horizontal directions (bidirectional cyclic loading). The results obtained were compared with previous experimental results under unidirectional cyclic loading conditions. The comparative analysis using empirical data revealed that the hysteretic curve of the CHSD under bidirectional cyclic loading maintained a relatively constant strength increase ratio and effective stiffness along with a stable spindle shape until the damper reached the ultimate state despite the continuous change in the loading direction. Further, compared with the unidirectional cyclic loading condition, the CHSD under bidirectional cyclic loading exhibited similar structural trends considering the damper aspect ratio and material influence. Moreover, the total accumulated plastic deformation in each loading direction was approximately the same as the cumulative plastic deformation caused by unidirectional cyclic loading.