Due to the tremendous growth in the metropolitan D.C area, the Maryland Aviation Administration (MAA) decided to upgrade the airport’s functionality, notably adding a state-of-the-art parking garage to consolidate ten rental car companies. The parking structure design involved a cast-in-place concrete system and was based on the desire for minimized maintenance. The facility footprint included 3.5-million square feet of parking space. More than 3-million linear feet of VSL’s VSLAB+® bonded slab post-tensioning system and several other unique features make it significantly different from typical parking garages.
The VSLAB+® bonded slab post-tensioning system provided total encapsulation of the strands using high density plastic duct with watertight, duct to anchorage couplers. Strict control of stressing and grouting operations was required. Using an innovative 2-strand hydraulic ram, tendons were stressed to 10-kips/strand on the day after concrete placement to control initial cracking. Final stressing operations commenced once the concrete reached 3200-psi. A high-performance, low-bleed grout was mixed and placed with a colloidal mixer to achieve optimum results. Grout vents with mechanical shut-off valves were strategically placed in accordance with PTI recommendations, to release air and ensure full encapsulation. In addition, the team instituted a series of grout tests to ensure the density, water/cement ratio and grout fluidity met the project specifications.
Another interesting feature of this project was the concrete pour sequence. The original design layout called for 93-concrete pours of approximately 10,000-sf each, however, the team opted to increase the pour size to 33,000-sf. This change provided multiple benefits, including elimination of tendon couplers, and a reduction in the number of bulkheads and joints.
Based on a cooperative effort fostered by the owner, the project team delivered the garage on time and on budget. The facility offers customers one-stop convenience for rental cars and frees up more than 1,000 prime parking spaces in the terminal parking structure.