Nonlinear seismic analysis of asymmetric in plan buildings

Abstract

In many buildings the centres of resistance do not coincide with the centres of mass. As a consequence, lateral base motion during an earthquake gives rise to torsional vibration of the structure. The inelastic seismic behaviour of asymmetric-plan buildings is considered using the histories of base shear and torque. The procedure to construct the base shear and torque (BST) surface of the system with an arbitrary number of resisting elements in the direction of asymmetry and of ground motion is proposed. The factors that determine the shape of the BST surface are the strength eccentricity, lateral and torsional capacity of the system and planwise distribution of strength. The BST surface contains most of information necessary to describe the inelastic properties of a system. However, the inelastic deformation cannot be computed unless a nonlinear static or dynamic analysis is performed.Kod mnogih zgrada centri nosivosti, krutosti i masa se ne poklapaju. To moze dovesti do pojave torzionih vibracija u slucaju da zgrada bude izlozena dejstvu zemljotresa. U radu je razmatrano neelasticno ponasanje nesimetricnih zgrada prateci zavisnost izmedju ukupne smicuce sile (BS) i momenta torzije (T) u osnovi zgrade. Predlozen je postupak konstruisanja interakcionog BS-T dijagrama za sistem sa proizvoljnim brojem nosecih elemenata postavljenih u pravcu dejstva zemljotresa. Neelasticni odgovor sistema i oblik interakcionog dijagrama zavisi od ekscentriciteta izmedju centra masa i nosivosti, od kapaciteta torzione i poprecne nosivosti konstrukcije i distribucije nosivosti u osnovi zgrade. Interakcioni BS-T dijagram sadrzi najveci deo informacija potrebnih da se opisu neelasticne osobine posmatranog sistema, ali nelinearne deformacije ne mogu biti sracunate sve dok se nelinearna staticka ili dinamicka analiza ne sprovede.