Effective oscillators for the seismic analysis of inelastic one-way asymmetric-plan buildings

This study proposes a novel oscillator, referred to as the co-shape oscillator (COSO), which can be effectively used in the nonlinear response history analysis (NRHA) of multistory asymmetric-plan buildings. Each COSO, consisting of a rigid mass block connected with two spring–dashpot sets, represents a pair of vibration modes of the original multistory asymmetrical building. When compared with the common single-degree-of-freedom (SDOF) oscillator, the COSO with translation–rotation coupled motion is more suitable to represent the motions of asymmetrical buildings. The issue of reflecting the non-proportionality between the modal translation and the modal rotation existing in the SDOF modal oscillator does not exist in the COSO. The COSO further considers the nonlinear coupling within the associated two vibration modes of the inelastic multistory building. Substituting the governing COSOs for the finite element model of the multistory building substantially improves the efficiency of performing NRHA. Two example asymmetrical buildings, one single-story and one 20-story, were used to illustrate the effectiveness of the COSOs.

► Co-shape oscillators (COSOs) are proposed for the analyses of asymmetric buildings.
► Each COSO represents a pair of vibration modes of the original building.
► The COSO can capture the dynamic characteristics of asymmetric buildings.
► The co-shape coordinate system is novel for structural dynamics.