Using PBEE to assess and improve performance of different structural systems for low-rise steel buildings

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, special 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 studied. 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.

An analytical framework to assess earthquake-induced downtime and model recovery of buildings

“…The results highlighted the contribution of impeding factors, structural repair, and non-structural repair to the total downtime estimates. Terzic and Mahin (2017) studied the performance of conventional and seismically enhanced low-rise commercial steel buildings using the FEMA P-58 methodology and expressed the benefits of the enhancements in terms of repair cost and repair time. Molina Hutt et al (2021) examined the performance of modern tall buildings, designed following a performance-based procedure, in terms of their downtime to functional recovery using the REDi guidelines with some adjustments.…”

Optimal design of dampers in seismic applications utilizing the MOPSO algorithm

“…In this optimization problem, damping coefficients of dampers are selected to be the only design (i.e., decision) variables to provide an initial insight into the usability of MOPSO in seismic applications (see VDMF Configuration and Modeling Section for more details). The other damper's properties, stiffness and velocity exponent, are adopted from the engineered design solution (Terzic and Mahin, 2017) and take values of 2000 kips/in. and 0.5, respectively.…”

“…The building was located in Los Angeles at a site characterized by spectral accelerations of S s = 2.2 g (for short period) and S 1 = 0.74 g (for a period of 1s). The building was modeled in OpenSees (McKenna and Fenves, 2004) by Terzic and Mahin (Terzic and Mahin, 2017) with viscous dampers modeled utilizing Maxwell model (linear spring and nonlinear dashpot in series). It is to be noted that dampers of VDMF were originally designed by Miyamoto International, Inc. with the design objective to limit the interstory drifts at the design level earthquake to 1%.…”

“…Moment frames with supplementary damping devices (i.e., damped moment frames) are often used for the design of new and retrofit of existing buildings as they are known to improve seismic performance at a reasonable cost (Terzic and Mahin, 2017;Wang and Mahin, 2018a;Del Gobbo et al, 2018). The improved performance is…”

“…This is a direct result of code criteria that permit high interstory drifts (2.5% for low-rise buildings) along with a relatively small strength (0.75% of the seismic base shear based on strength reduction factor (R) of 8), leading to a highly flexible and relatively weak lateral load-resisting system. However, Terzic and Mahin (Terzic and Mahin, 2017) further showed that a relatively small investment into larger damping devices stiffens up the frame, yielding significant reductions in repair cost and repair time when compared to a code-compliant special moment frame. Interestingly, the improved (beyond the code) damped moment frame achieves far better performance than a special moment frame at a smaller construction cost.…”