Concerto is the first tall building in Los Angeles using Performance Based Design which allowed us to replace prescriptive code seismic forces with rationally developed design criteria. Our use of this sophisticated design approach, in conjunction with 12,000 psi high strength concrete, produced major cost construction savings because of smaller seismic columns and beams. The tower’s lateral system uses internal concrete ductile moment frames permitting unobstructed views on all sides of the structure. Two 28-story, 320-foot concrete towers stand above 4-levels of subterranean parking. A 35,000 square foot rooftop plaza over three levels of above-grade parking separates the towers from the 5-story Type III wood framed lofts.