Torsional Response of Asymmetric Buildings under Earthquake Loads

Abstract

Irregular buildings constitute a major fraction of the urban infrastructure due to various newlineoccupational and architectural demands.Most buildings are irregular to varying degrees newlinedue to asymmetry in plan, elevation, distribution of vertical members or mass distribution newlineon the floors. Perfectly regular buildings are more of an idealized concept and in practice newlinethis condition is rarely satisfied. Under seismic loading, the presence of structural newlineirregularity in buildings leads to large displacement amplifications and stress newlineconcentrations in the members which lead to their severe damage and ultimately, early newlinecollapse. The presence of irregularities in mass, stiffness, strength or geometry along the newlineelevation of the building is categorized as vertical irregularity. Torsional irregularity or newlinein-plan irregularity can be considered to exist if the building possesses non-concurrency newlinein the lines of action of centers of mass and stiffness on a common vertical axis at each newlinefloor level. During earthquakes or any other lateral loads, the inertia force acts through newlinethe center of mass and resistive force through the center of stiffness or resistance. If an newlinein-plan eccentricity is present, a time varying twisting moment is generated causing newlinetorsional vibration. newlineThe proposed study investigates the effect of in-plan irregularity and vertical irregularity newlineon the seismic response of buildings. Irregularities in mass and stiffness along the height newlineof the buildings in combination with torsional irregularities along the plan of the newlinebuildings are evaluated. Transient analysis is carried out to analyse the seismic response newlineof the shear wall buildings, mass irregular buildings and stiffness irregular buildings with newlinein-plan eccentricity using LS-DYNA software. The responses of the irregular buildings newlineand the effect of in-plan eccentricity in terms of variation in natural period, base shear, newlinestorey drifts, roof deflection, torsional resultant and roof rotations obtained from the newlineanalysis due to asymmetry have been studi