ENHANCED SEISMIC DESIGN OF THE NEW SAN DIEGO CENTRAL COURTHOUSE

摘要

Located in the central business district of downtown San Diego, the new 24-story San Diego Central Courthouse replaces the adjacent existing facility built in 1961 over an active earthquake fault zone. Designed by Skidmore, Owings & Merrill LLP for the Judicial Council of California, the new Superior Court facility will include 71-courtrooms comprising 704,000 sq ft of administrative, clerk, jury, security operations, holding and building support areas allowing for the consolidation of San Diego County criminal trial, family and civil courts under one roof. This paper focuses on the structural design of the steel framed superstructure to achieve enhanced seismic performance objectives of the New San Diego Central Courthouse with an emphasis on the advanced seismic analysis, design methods (Direct Analysis Method) and technologies employed. The building superstructure consists of a cost-effective steel framed superstructure with two-way lateral special moment frames (SMF) utilizing ductile reduced WF beam section "RBS" connections with WF cruciform and built-up box column sections. The steel moment resisting frames incorporate 106 nonlinear viscous damping devices (VDD) to provide a distributed supplemental energy dissipating damping system over the height of the structure to reduce seismically induced building story shears, story drifts, floor accelerations and inelastic rotational demands on moment frame beam-column joints. These VDD's were also effective in providing damping for wind loads leading to reduction of the dynamic component of the wind vibration amplitude. The modelling was completed successfully pushing the limits of the CSI ETAB v9.7 software in capturing the complex nonlinear response history analysis behavior. This paper is intended to document the enhanced seismic performance objectives in the application of advanced seismic design methods and technologies in achieving resilient and sustainable structural systems in regions of high seismicity. It will describe the step by step approach to selection of the final lateral system for the project. Additionally, the full-scale SMF steel box column RBS connection qualification testing completed during the construction document design phase which extended AISC limits for this project will be briefly described. In addition VDD prototype and performance testing was completed during construction phase to validate the VDD properties. Other features of the integrated architectural and structural engineering design include an interconnecting pedestrian bridge to the Hall of Justice, roof cornice overhang and offset circulation core. Under construction for more than 30 months, the courthouse was dedicated in June 2017.