Author(s)

VESNA TERZIC & STEPHEN A. MAHIN

Abstract

In recent earthquakes in Chile, New Zealand, and Japan modern buildings were generally quite safe. However, there was a tremendous variability in the economic and social consequences associated with damage repair and loss of occupancy. Code-compliant structures are generally designed to provide safety and prevent collapse at minimum costs, but when severe ground shaking occurs, the damage to contents, nonstructural components and the structural system can result in loss of function, which can have a dramatic impact on the occupants, owners, and community. Such situations can be avoided by mitigating future seismic damage through a better structural design. Although structural enhancements may likely increase the initial cost of a structure they should be compensated through benefits realized over its lifetime. This paper presents the results of repair cost and repair time analyses of conventional and high-performance code-compliant low-rise commercial steel buildings designed for the same location. The buildings are located at a site with high seismic hazard representative of western North America. The conventional lateral load-resisting systems include: special moment resisting frame, spe- cial concentrically braced frame, and buckling restrained braced frame; and high-performance systems include: seismically isolated intermediate moment resisting frame, seismically isolated ordinary concentrically braced frame, seismically isolated buckling restrained braced frame, and viscously damped moment frame. In addition, enhancements of the fixed, seismically isolated, and viscously damped moment frames beyond the code minimum and their effect on the repair cost and repair time are stud- ied. The analysis reveals significant damage savings for code-compliant seismically isolated systems relative to their conventional counterpart, with seismically isolated ordinary concentrically braced frames yielding the largest savings. It also shows that enhancements of the isolation and viscously damped system beyond code minimum standards results in significant reduction in damage-induced losses, while the enhancement of the SMRF does not yield desirable loss reduction.

Keywords

Base isolation, braced frames, dampers, moment resisting frames, repair loss, repair time