Seismic Evaluation Retrofit Design of Civic Center Administrative/Police Building - Union City, CA
The Administrative/Police Building was designed in 1977 under the provision of the 1973 Uniform Building Code. The building is on two levels, with the first level below grade on two sides and at or near grade on the other two sides. The building is irregular in shape and walls occur on both orthogonal and 45-degree orientations.
The method of seismic evaluation used is the ASCE/SEI Standard 31-03 for Seismic Evaluation of Existing Buildings. This standard includes guidelines for determining the appropriate evaluation process and method based on the chosen goal of Life Safety for the upper level and Immediate Occupancy for the lower level following a major nearby quake. The evaluation is also specific for the type of construction and seismicity of the site and includes checklists for identification of both structural and non-structural potential seismic deficiencies.
For seismic evaluation of the structure, a Tier 1 Screening was used to identify potential seismic deficiencies. With that screening completed, a Tier 2 Evaluation was done for the components identified as having a potential seismic deficiency under the Tier 1 Screening. Structural checklists were completed and structural calculations were prepared as needed to check against acceptance criteria as given in the ASCE/SEI Standard.
Detail retrofit design includes:
- New roof lateral load transferring system including continuous collectors with intermediate blockings and connections to the lateral wall systems.
- Steel bracing frames at limited location of exterior walls with limited impact on the original architectural features of the building. Exterior foundation for the steel bracing will also required.
- Steel brackets need to be installed on top of bearing walls to prevent potential seating offset of the main girders. The interior construction sequence needs to be considered to allow the City emergency call center to be functional at all hours and cause minimal interruption to the police station operations.