The Earthquake Engineering Online Archive

Coupled lateral torsional response of buildings to ground shaking

Kan, Christopher L.; Chopra, Anil K.

UCB/EERC-76/13, Earthquake Engineering Research Center, University of California, Berkeley, 1976-05, 175 pages (555/K218/1976)

This study of earthquake response of buildings for which the lateral motions are coupled with the torsional motion is presented in three parts: The elastic response of torsionally coupled one-story buildings to earthquake ground motion, characterized by idealized shapes for the response spectrum, is studied. Influence of the basic system parameters on the response is investigated. The relationship between the forces--base shears and torque--in a torsionally coupled system and the base shear in a corresponding torsionally coupled system and the base shear in a corresponding torsionally uncoupled system is established, and the effects of torsional coupling on earthquake forces are identified. Useful upper and lower bounds are presented for the base shears and torque due to simultaneous action to two horizontal components of ground motion of equal intensity. A simple, semiempirical analysis procedure, accompanied by the necessary numerical data, is presented to provide a convenient means to obtain conservative estimates of earthquake forces in torsionally coupled buildings. A simple procedure is developed for the analysis of the elastic response of a particular class of torsionally coupled multistory buildings to earthquake ground motion, characterized by smooth response spectra. A perturbation analysis of vibration frequencies and mode shapes is conducted. To illustrate the application of this procedure, a numerical example is presented.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-76-13.pdf (8 MB)