The LEED Gold Certified rehabilitation of this 1927 historic landmark included cost-effective seismic isolation, modernization of plumbing and electrical systems, and the addition of a new building with a connecting underground tunnel, all without altering the building’s historic integrity.
- The City of Pasadena had two primary goals for the seismic upgrade of their City Hall: to limit the intrusion of the new seismic upgrade into the significant historic elements of the building and to minimize the amount of damage anticipated after a major earthquake. To address both needs, friction pendulum isolators were placed between the foundation and basement. They were positioned on an off-grid system with one isolator in the center of four columns, thus supporting the entire square rather than one isolator per column. This innovative technique both minimized costs and increased construction efficiency.
- Forell/Elsesser benchmarked performance analysis against data obtained from the Northridge earthquake, showing that much of the historic non-structural elements were sound and did not require repair, thus keeping costs down.
- Shear walls were installed on the East end of the building’s wings, and a replacement of the deteriorating arcade with a utility tunnel running underneath, structurally tied the building’s two wings together. The project also included the modernization of Mechanical, Electrical and Plumbing systems, necessitating the redesign of structural systems to accommodate the new weight and space requirements of these energy-efficient additions.