ABSTRACT
Recently, the studies on the additional negative stiffness (NS) in structures have attracted many researchers. NS can mimics the structural yielding and reduce structural internal force. For civil structural design, multi degree of freedom (MDOF) structural performance should be estimated by single degree of freedom (SDOF) system according spectrum theory. Additional NS changes the structural property to be bilinear, which complicates the converting process from MDOF to SDOF. This paper presents a new method to approximately estimate the MDOF structure with NS in the 1st story (MNS1) by an approximate SDOF bilinear elastic system (ASBS). The accuracy of approximation from the MNS1 to the ASBS is studied by the sensitivity method of mode shapes in which the relative changes in structural mode shapes are related to the variation of stiffness. An eight-story numerical example is employed to illustrate the accuracy of approximation by the proposed method. The results show that the accuracy of approach is acceptable, and ASBS can estimate the response of the MNS1.
