ABSTRACT
A special steel moment frame building with seismic dampers was designed to meet a enhanced structural performance level in the Bay area. In order to protect the valuable computer data center, passive control with steel moment frame system were selected as a most cost-effective solution to control the lateral acceleration and displacement for earthquakes. The story drift ratio was limited to 1% of the story height during the Design Basis Earthquake (DBE), which has a mean return period of 475 years. Seismic dampers were mounted on Chevron braces in selected locations each floor. Approximately 20% of critical damping were provided. The primary seismic resistant frames, without dampers, were designed to meet the Uniform Building Code of 1997. In addition, the seismic resistant frames, with dampers, were designed to remain elastic under a Design Basis Earthquake. 3 site-specific DBE time-history analyses were performed and the maximum values were selected for design. The goal is to limit the lateral drift to 1% of the story height and, the Demand-to-Capacity ratio (DCR) of the earthquake resistant members within 1 under the DBE event. As a result, collector forces were found to be much higher than originally expected. More piles with larger lengths and bigger pile caps were designed to meet the DBE demands.
