In order to aid in post-earthquake response and recovery efforts, hospitals and other critical structures must remain operational after a design level seismic event. Protective systems (base-isolation and supplemental damping) provide a means to reliably and economically achieve improved structural and nonstructural performance. Viscous wall dampers (VWDs), originally developed in Japan, will be used in this first U.S. application to provide supplemental damping and enable a new 15 story hospital in San Francisco, California to achieve stringent performance goals. This paper introduces the innovative VWD devices, describes the results of full-scale prototype testing, summarizes VWD properties, and explains modeling techniques for implementation in nonlinear response history analysis. By using VWDs in this hospital application, the overall steel weight was reduced by an amount that more than offset the installed cost of the VWD devices and a unique lateral system was designed that will enable improved structural performance, when compared with traditional systems. Also, floor accelerations in the upper floors of the building were significantly decreased, thereby reducing the costs associated with nonstructural bracing, especially for the central utilities plant located on the top floor.
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