Sophisticated Earthquake Resistant Features on the Wilshire Grand


The Conco Companies are providing the entire cast-in-place concrete for the new Wilshire Grand Center currently under construction in Los Angeles. As it is the tallest building to be constructed in a “seismic hot zone,” the tower’s structural design had to be put through a series of some of the most technologically advanced earthquake modeling available today.

Designed by architect, David Martin, the Wilshire Grand has large windows on every floor, which required the construction of a concrete core and further complicated the earthquake resistance of the skyscraper. With a core that is only 33 feet wide along its narrowest side for a building 1,100 feet tall, the geotechnical firm, AMEC, was brought in to reduce the likelihood of damage to the structure from a quake.

AMEC’s task was to create simulated earthquakes that tested the structural integrity of the tower and evaluate “the maximum acceleration — the greatest jolt — that the building could experience.” They conducted a series of tests and studied damage to structures from past earthquakes in Southern California that were built on similar faults and in comparable soil conditions. Based on the results of the tests, engineers redesigned the size and depth of the foundation to resist a much as “13.2 million pounds of force pulling up and 25 million pounds of force pushing down on each of the 20 perimeter columns as the tower swayed during an earthquake.”

When additional testing still simulated some buckling, AMEC’s solution was to add devices called buckling-restrained braces rather than increase the amount of concrete. These devices are long steel bars encased in a steel box filled with grout that allows the bars to compress or stretch as the building moves. There are 170 of these devices used in the construction of the new Wilshire Grand Center.

The Conco Companies are a leading supplier of concrete services for the Western U.S. and got our start in the Bay Area in 1959 by offering clients the best value on a wide range of concrete services and products. Since that time, we have taken a leading role as one of the top concrete contractors in the region. Our offices serve California, Colorado, Oregon, Washington and Nevada.

Sources: – Sources: Leonard Joseph, Thornton Tomasetti; Tammy Jow, Joseph Varholick, Carey McLeod and Noel Moreno, A.C. Martin; Steve Carroll, Schuff Steel; Ian Aiken, SIE Inc.; Nippon Steel Engineering USA; G.G. Schierle, USC School of Architecture; Dave Eichten, Pankow.

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