Dynamic torsional coupling in asymmetric building structures

An approximate method is proposed for the dynamic analysis of torsionally coupled tall building structures by utilizing the properties of their uncoupled counterparts. An exact solution is first given for the particular case in which the lateral and torsional stiffness matrices are uncoupled by same transformation. The method is then applied to a wider class of structures where this condition is only approximately satisfied by reducing the dynamic coupling problem to an approximate two-degrees-of-freedom system. Simple formulae and graphical representations of dynamic magnification of static eccentricity are given. Two numerical examples illustrate the use of the proposed method, checking on its accuracy and comparing its results with seismic code provisions.