Garage 5 Slab Replacement

A detailed assessment was performed of Parking Garage 5 in Silver Spring, MD as part of a task order contract with the Montgomery County Department of Public Works and Transportation Division of Capital Development Services (DPWT). The garage consists of five tiers of above-grade levels with a framing system containing 5” thick reinforced concrete slabs supported on composite structural steel beams and girders. The survey performed incorporated elevated parking decks, exterior cladding, structural framing, stairwell, stair/elevator roofs, MEP systems, and vertical conveyance.

The structural framing system and waterproofing items were observed to be in fair to poor condition, with certain components showing signs of severe physical distress, requiring significant remedial repairs or replacement. The suspended decks were beginning to show signs of extensive spalling and analytical computations showed the structure is incapable of withstanding lateral loads induced by seismic forces. MEP deficient items included a crumbling electrical grid which required a new PEPCO service feed. For this effort, the existing electrical panels had to be retrofitted and the lighting levels were improved with new lighting and provisions for a new Uninterrupted Power Supply system (UPS) along with an air-conditioned UPS room, to maintain critical life-safety systems in the event of a power outage.

Forensic testing including chlorides, petrographic analysis, compressive strength, rebar depth and UT weld tests were performed. The tests led to the conclusion that isolated repairs combined with extensive replacement of selected deck slabs, new epoxy coated reinforcing, waterproof membrane, new expansion joint seals, supplemental strengthening of the steel frame, stair repairs, and the replacement of stair doors would be an appropriate measure needed to provide a sustainable and safe parking structure.