Elastic Earthquake Analysis of a Class of Torsionally Coupled Buildings

A simple procedure is developed for analysis of elastic response of a particular class of torsionally coupled multistory buildings to earthquake ground motion, characterized by smooth response spectra. In this procedure the response of a N-story torsionally coupled building — a system with 3N degrees-of-freedom (DOF) — is determined by analyzing two systems: (1)An N-story torsionally uncoupled counterpart of the actual building — a system with N DOF; and (2)an associated one-story torsionally coupled system — a system with 3 DOF. The simpler analysis procedure leads to exact results if the variation of earthquake spectral acceleration with vibration period is idealized as flat or hyperbolic. For arbitrary but smooth shapes of the response spectrum, it is shown through a numerical example that the results of the simpler analysis are sufficiently accurate for design purposes.