Renovation & Seismic Upgrades
Seismic upgrade and remodel of existing building, with a 72,100 square foot footprint and consisting of five full levels and three partial levels above grade, a full basement and a partial second basement level. Existing structural system is a concrete encased structural steel skeleton with concrete slab and joists and perimeter shear walls that are to be partial removed for the remodel An atrium was created by removing twelve bays of framing full height in the center of the building. New brace frames were installed on three sides of the new atrium with another brace frame installed a bay away from the atrium, for a total of sixteen brace bays up to eight levels high. All column splices, brace and beam connections incorporated complete penetration splices, with columns up to W14x605, braces up to W14x283 and beams up to W14x176. The seismic upgrade included new collectors and welding existing riveted connections to transfer loads from existing structure to new brace frames, boxing some of the existing columns, and welding some of the existing riveted column splices. The remodel portion included structural framing to add 13,220 square feet of terraces to the partial upper levels, infill of existing openings and added reinforcing beams framing new openings. 25,500 square feet of decking was install at the terraces and infills. 200 ton and 75 ton hydraulic cranes were used to erect the braces frames and 50% of the terraces, with the cranes operating in the atrium. Shoring was installed by others in the atrium and the travel path from the street for crane travel, delivery trucks and forklifts with additional shoring under all crane outrigger locations. With city streets on three sides of the project, the only interruption to traffic/public transportation for our work was when trucks entered or exited the building.