Newmark Structural Engineering Laboratory. University of Illinois at Urbana-Champaign.
Abstract
This report summarizes the results of a parametric study of a controlled rocking seismic
lateral resistance system that includes two steel braced frames linked by replaceable
energy dissipating fuses that are engaged by controlled rocking behavior. The frames are
post-tensioned vertically to the foundation so as to facilitate self-centering after rocking.
The study was conducted using geometrically and materially nonlinear finite element
analysis of a two-dimensional prototype of the structural system. In this study, the
structure is subjected to a suite of far-field ground motions representing different hazard
levels in the Western U.S. The characteristics of the structural fuses, which absorb
energy through a combination of cyclic shear and localized flexure mechanisms, were
based on experimental test results of steel slit shear panels and engineered cementitious
composite shear panels. Three key parameters are investigated that affect the response.
The first is the ratio, A/B, of the bay width of the braced frames as compared to the width
of the shear fuses connecting the frames. The second is the overturning factor (OT),
which is the ratio of the total resisting moment of the fuses and post-tensioning compared
to the overturning forces in the design code. The third is the self-centering factor (SC),
which is the ratio of restoring moment of PT to the resisting moment of the fuses. Based
on the computational results, recommendations are made for appropriate ranges of values
for each of these parameters for effective performance.published or submitted for publicatio
