Rising 1,100 feet from the ground, the Wilshire Grand Center is the tallest building in Los Angeles and the highest west of the Mississippi River. The iconic skyscraper is a mixed-use development, standing 73 stories tall in the footprint of one of the world’s most active earthquake zones. To lift the tower from the ground into the Los Angeles skyline, the structure needed a seismically resilient foundation with the strength to withstand Southern California’s fiercest earthquakes.

Having engineered world-class structural designs, Wood recommended creating a concrete mat design for the building foundation. To prevent differential curing, the entire foundation was created using one continuous pour of concrete. Hundreds of trucks provided more than 21,000 cubic yards of concrete in 18 hours, the largest continuous concrete pour in world history, according to Guinness’ World Records. Delivering this quantity of concrete in the tight confines of downtown Los Angeles was a logistical challenge.

The unique curving arc of the south façade and functionality requirements as a hotel also added to the complexity. The structural system consists of concrete core walls, composite columns, composite floors and steel outrigger diagonals. As this structural system is not ordinarily permitted by the building code, an alternative design procedure was used based on performance-based earthquake engineering (PBEE) analysis and design.

To support the placement of the massive concrete foundation, we performed geotechnical inspection and testing to approve the bedrock. Our team also worked with the shoring engineer to provide an earth retention system up to 100 feet deep around the project, which is surrounded by other tall buildings and adjacent subway tunnels. We developed and operated a monitoring system to ensure safe operation of the subway during construction.