NEHRP Clearinghouse

Title
Inelastic Seismic Response of a Torsionally Unbalanced Single-Story Building Model.
File
PB80164197.pdf
Author(s)
Irvine, H. M.; Kountouris, G. E.
Source
National Science Foundation, Washington, DC. Engineering and Applied Science., July 1979, 172 p.
Identifying Number(s)
R79-31
Abstract
The dynamic effects of coupling between torsion and translocation using a simple torsionally unbalanced single-story building model are described. The investigation deals with a two-degree-of-freedom model in which two frames support a diaphragm the center of mass of which may be offset from the center of stiffness. Frames are assumed to behave as simple elastic-plastic springs and to have the same stiffness and strength levels. A comprehensive parameter study was undertaken to identify trends in the peak ductility demands of the worst situated frame. Results are plotted and interpreted. A simple frequency domain analysis outlines why the peak ductility demands occur in the frame farthest from the center of mass. The study indicates that the most important parameter is one involving the product of diaphragm mass and spectral acceleration normalized by a yield level in the frame. For wide ranges of other parameters, the peak ductility demand is roughly linear in this parameter, a characteristic of symmetric structures. Eccentricity does not appear to be a significant parameter. A regression analysis of the data yielded simple confidence levels for peak ductility demands.
Keywords
Dynamic response; Ground motion; Buildings; Regression analysis; Earthquake engineering; Earthquake resistant structures; Seismic design; Equations of motion; Two degrees of freedom; BILIN subroutine; Mathematical models; Framed structures; Subroutines; Dynamic structural analysis