An evaluation of the effectiveness of base isolation systems in enhancing the seismic performance of modular steel buildings

摘要

More consistent quality, reduced site disruption and flexibility of use are some of the advantages of Modular Steel Buildings (MSBs) as affordable, timesaving alternatives to traditional on-site steel buildings. However, despite their effectiveness, due to detailing requirements for assembly of the prefabricated modules on site, these systems are prone to undesirable failure mechanisms during large earthquakes. In particular, their vulnerability to inelasticity concentration in vertical connections and soft-story formation has been a significant concern for researchers in recent years. On the other hand, seismic base isolation has become one of the most effective technologies in protecting structures against destructive earthquakes. By providing sufficient flexibility at the base level, the isolation system absorbs the majority of the displacement demand of the earthquake, with the main structure mostly displacing as a rigid body. Simultaneously, base isolation considerably lowers the fundamental frequency of the system. For stiff structures with higher natural frequencies, this effect can have adverse consequences by shifting the natural frequency inside the dominant range of input frequencies. Considering both effects, the present paper examines the effectiveness of this scheme for enhancing the seismic performance of MSBs with Laminated Rubber Bearings (LRBs). OpenSees is used to evaluate the nonlinear responses of a series of typical braced frames of MSBs with various heights with and without an optimally designed LRB to selected suites of far- and near-field recorded ground motions. By summarizing the results of these analyses, conclusions are made to provide better insight into the applicability range of these systems.