The Tower, a 32-story office building in Burbank. California, clearly demonstrates the practicability and economy of concrete construction in seismic areas. The savings that accrued from reduction of structural cost, reduction in cladding, and reduction of floor to floor height amounted to at least $15 per square foot for this one million-square-foot project. This was achieved with materials and methods in daily use in Southern California, proven by past experience of the contractor, his subtrades, and suppliers.
The basements and first five levels cover a full block. These parking levels, except for the tower footprint, are framed with cast-in-place post-tensioned beams and one way slabs.
The tower footprint is set at 45 degrees to the base and all levels are framed with post-tensioned flat plates, typically seven inches thick, spanning nominally 27 feet. Lateral forces are resisted in the tower with a perimeter cast-in-place concrete ductile moment frame, exposed to be part of the architectural appearance of the façade. At the base, lateral loads are transferred to perimeter shear walls.
The tower foundation is a concrete mat of varying thickness, supplemented by pad footings for the lower structure.
For maximum parking efficiency, vertical circulation was provided by sloping the parking floor in two bays of the base structure. Continuity of the floor diaphragm and of circulation was maximized by warping the tower area slabs to meet the ramped floors.
The Tower clearly demonstrates that tall concrete buildings need not be confined to non seismic areas, nor are unusual techniques or materials required to be used or invented. Utility and economy can be achieved using the same materials and techniques perfected by common experience. Project Summary
32 stories above grade
4 basement levels
Total suspended area: 1 million square feet
Garage capacity: 1,342 cars Credits Owner:
BlackRock, New York, New York
Herbert Nadel Partners, Los Angeles, California Structural Engineer:
Frame Design Group Inc., Sherman Oaks, California General Contractor:
Stolte/KG Concrete Frame Contractors
Parr Contracting Company, Torrance, California
Seneca Construction Systems Inc., Houston, Texas