Project Description /OverviewThe TCW Tower is a 850,000 sq. ft., 38-story building located in downtown Los Angeles. The building utilizes a modified framed tube along the perimeter of the building (with clustered columns at the corners) and four internal eccentrically braced frames in combination with a Vierendeel outrigger system. The behavior and design criteria of the eccentric braced frames were established through the research of Professor Egor Popov from the University of California at Berkeley. The eccentric braced frames are located between adjacent elevator banks and use the inverted K-configuration, except where accessibility requires the inclined single diagonal. This framing allows the axial forces induced in the braces to be transmitted either to a column or to another brace through shear and bending in a floor beam segment called a shear link. At service loads, the frames are excellent in providing lateral stiffness. During a severe earthquake, the links yield favorably in shear and effectively dissipate the generated energy. Popov peer reviewed the eccentrically braced frames and provided invaluable contributions toward their final design.
This structural system was designed to withstand several loading combinations; gravity, and dead and live loads. A wind tunnel study was performed using the high-frequency force balance technique and generated three different combinations of loads for drift and strength purposes. Seismic design criteria for two levels of earthquake expectations were also used. First, the structure is designed to remain elastic for the maximum probable earthquake. Second, the structure is designed to act with controlled inelasticity and without a developed failure mode mechanism for the maximum credible earthquake.