Challenges: Los Angeles City Hall, being culturally and historically significant, as well as an essential government facility, required restoration and strengthening to remain functional after a magnitude 8.2 earthquake . Project requirements also called for the protection of the building's exterior façade and historic interior fabric, which were frequently damaged during regional earthquakes over the past 70 years. A key challenge was assuring that the Los Angeles City Hall's seismic resistance level was never reduced or compromised by the use of interim bracing during construction.

Solution: In collaboration with AC Martin Partners' architects and engineers, NYA designed a hybrid system, combining seismic isolation bearings, shear walls and viscous dampers at the top of the structure and the plane of isolation at the base. This system provides a level of life safety and damage control that exceeds the level provided by conventional strengthening schemes. The base isolation system consists of 416 high damping rubber bearings, 90 flat sliding bearings and 52 viscous dampers installed between the basement and foundation levels of the building. Los Angeles City Hall is the tallest building ever to be base-isolated.

×