CHALLENGES & SOLUTIONS

• Main objective was to retain historical integrity with the installation of new lateral systems and additions.
• Using concrete shear walls, instead of steel bracing in this existing structural steel building, avoided cluttering the historical windows, but also created more challenges for the structural design.
• A challenge was created by the large size of the windows at the exterior. In order to retain the open retail space on the interior, a portal shear wall system was designed around the perimeter. This system was constrained by existing masonry pier locations. At the interior of each pier, shear walls were created using new reinforced shotcrete with shear studs welded to existing steel columns within historical walls.
• Small areas of the historical floor were removed to allow access to structural steel columns in the building, to create the new portal shear walls. These areas were later filled in with concrete and metal deck, without compromising the integrity of the floor.
• The existing coffered ceiling created a situation that required the spandrels to be constructed from the top down to maintain the integrity of the historical ceiling. Existing steel box girders above this ceiling still remain in the structure.
• The existing roof level slab was removed at the middle bay for the entire length of the slab to allow the large open areas to draw light into the space. A system of horizontal steel X-bracing was developed to tie the existing slab section together to maintain the integrity of the slab diaphragm. In doing so, the seismic capabilities of the structure were maintained and improved.
• An 8th level was added at the interior of the building, as well as a mezzanine structure at the 2nd floor. Both additions were posed a challenge in connection without compromising the structural and historical integrity of the existing building. The basement level was also renovated for Bank of America's new space.