Los Angeles City Hall

This paper describes the Los Angeles City Hall building and a unique seismi c strengthening program. Four hundred and sixteen high damping rubber beari ngs, 90 flat sliding bearings and 64 viscous dampers have been installed as part of the seismic rehabilitation. The building is a 460 feet tall steel frame with unreinforced masonry infill. The rehabilitation consists of inst alling high damping rubber bearings at its base supplemented with nonlinear viscous dampers. This paper describes various aspects of the project inclu ding the development of seismic performance goals, identification of inhere nt seismic deficiencies of the existing building, evaluation of alternative strengthening schemes, the final design process and construction issues. C opyright (C) 2000 John Wiley &, Sons, Ltd.