JAMA has recently begun sharing some of the interesting structural challenges we encounter on projects. The latest in this series is the Broad Beach Residence – a 2-story structure with irregularly shaped floor plan for Michael Ovitz, of Creative Artists Agency and Disney fame.
The actual building area is 16,000 square feet and the roof is about 30 feet from slab on grade. The new home fronts Broad Beach in Malibu, and while somewhat straightforward in design, is innovative for its structure. Second floor and roof gravity framing consist of steel wide flange girders, truss joist and 2x joists. The framing is supported on steel columns, and both levels transfer diaphragm forces through plywood sheathing. There is 3 3/8” concrete topping on the second floor. Lateral loads induced by seismic are resisted by flexible wood diaphragms. Loads from the roof diaphragm transfer to plywood shear walls and steel special moment frames. Discontinuous lateral force resisting system forces the loads transferred from the roof to the second floor diaphragm to migrate through transfer members. Eventually, second floor diaphragm loads are resisted by steel special moment frames in the east- west direction and cantilevered concrete filled steel columns in the north-south direction in the south triangular portion of the building. Lateral forces in the north rectangular portion of the building are resisted by concrete shear walls. Concrete walls and concrete filled steel tube columns carry both vertical and lateral loads down to the building foundations. Structural slab on grade spans one-way in-between grade beams. Walls and frame columns are supported on grade beams and deep pile foundations.