Effects of M3 or PMM Nonlinear Hinges in Pushover Analysis of Reinforced Concrete Buildings

Effects of M3 or PMM Nonlinear Hinges in Pushover Analysis of Reinforced Concrete Buildings

In Taiwan, the detailed seismic evaluation procedures used by engineers are nonlinear static analyses, known as pushover analyses, which are based on the Capacity Spectrum Method, where the nonlinear behavior of the building is concentrated by the nonlinear hinge of the components. The seismic evaluation program TEASPA developed by the NCREE uses M3 nonlinear hinges for X-direction pushover analysis(where the Y-direction is M2). M3 nonlinear hinges do not consider axial force–moment interaction and their strength is determined by the column axial force at the static load stage. On the other hand, the moment nonlinear hinge PMM can consider axial force–moment interaction and its strength is determined by the column axial force of the pushover process. In this paper, three sample structures are used to discuss the influence of the nonlinear hinge setting of M3 or PMM on the pushover analysis of reinforced concrete structures. The three sample structures are a three-story traditional school building structure, a ten-story moment-resisting frame structure, and a ten-story moment-resisting frame with shear wall structure. The results show that the PMM nonlinear hinge can reveal the influence of the change of axial force on the bending moment strength and can also reflect the reduction of bending moment strength by the biaxial bending moment. The difference in performance target ground acceleration estimated by the pushover analysis using M3 or PMM hinges does not exceed 10%.