Los Angeles City Hall

Restoring & Protecting a Downtown Icon
I would like to extend my gratitude to Clark Construction Group for their devotion and continuing commitment the City Hall Seismic Rehabilitation project. Due to the dedication of your employees, City Hall will be a monument for all to enjoy for generations to come.
Gary Lee Moore, PE, City Engineer, City of Los Angeles
Location: 
Los Angeles, California
Client: 
City of Los Angeles
Architect: 
AC Martin & Partners
Additional collaborations with AC Martin & Partners:
Contract Value: 
$134,900,000
Size: 
911,000 Square Feet
Year Completed: 
2001

Los Angeles City Hall's countless appearances in Hollywood films and television productions made the building synonymous with the city itself. Weakened by a series of earthquakes, it was closed in 1998 for a total ground to sky refurbishment. The Clark team restored this iconic building to its original Art Deco grandeur and ensured state-of-the-art systems would offer protection from future earthquakes.

At 454 feet, the Los Angeles City Hall is the tallest base-isolated structure in the world. Its seismic upgrade allows City Hall to sustain minimal damage and remain functional after a magnitude 8.2 earthquake.

To strengthen the building, Clark-led project team added 30,000 cubic yards of concrete, 3,000 tons of structural steel, 5,000 tons of reinforcing steel, and an additional 68,467 million pounds of dead weight to the structure.

Clark also included the excavation of a sub-basement and installation of a system of hydraulic jacks to support the structure while the team installed 526 isolators and sliders, as well as 64 viscous dampers. Excavation of an exterior perimeter moat and saw cut of the perimeter walls from their foundations also was performed to allow the structure to float or sway during an earthquake. A seismically-reinforced shearwall aslo was constructed and extends from the foundationto the top of the building.

In addition to meeting rigorous safety and damage mitigation standards, the Clark team preserved the building’s distinctive façade, mosaics, artwork, articulated ceilings, and period ornamental details. The interior of the first five floors was renovated, including historic restoration of the ornate rotunda, grand staircases and other public areas. Historic electrical light fixtures were removed from their settings, cleaned, and restored to comply with current energy codes. Art conservators researched and analyzed the original 1928 paint colors in the main hallways so they could be replicated into the new construction.

The installation of the shearwalls, intrinsic to the building's seismic rehabilitation, required removing any conflicting structures or finishes. When shearwalls intersected historic fabric or historic walls, the historic fabric was removed, cataloged, crated, and stored.

Through Clark’s leadership, the project was brought in on schedule and within budget.

Awards: 
AGC - Build America Award, Renovation
AIA Los Angeles Chapter - Building Team of the Year
American Public Works Association - Project of the Year, Historic Restoration $10 million+
Buildings Magazine - Modernization Award Winner
LA Business Council - Architectural Award Grand Prize, Best Completed Project
LA Business Council - Architectural Award Winner, Commercial Mid-Rise Category
Los Angeles Conservatory - Preservation Award