SK&A’s Repair & Restoration Group provided an in-depth study and evaluation of the Aventine’s garage and plaza to develop repair quantity estimates and to initiate a structural repair and maintenance program.
The parking garage is a three-story, below-grade structure. The lowest level, is a five-inch thick concrete slab-on-grade, installed over a vapor barrier and six inches of compacted granular drainage fill, founded on engineered control fill and subgrade. Elevated parking decks are post-tensioned concrete flat slabs supported on reinforced concrete columns.
The structural slabs were cast-in-place over steel cables wrapped in a greased plastic sheathing. The slabs were designed as “two-way” slabs, reinforced with two-way post-tensioning (PT) tendons, as well as a nominal amount of conventional reinforcing bars. A section of the garage structure had no post-tensioning and was reinforced wholly with mild steel reinforcing. The post-tensioning system specified in the original structural plans was an unbonded, monostrand tendon system conforming to ASTM A416.
SK&A’s survey found that the garage’s structural framing was in fair-to-poor condition and spalled, delaminated, and generally deteriorated concrete was found throughout the garage slab top surfaces and soffits. Exposed post-tensioning cables and anchors were observed in a number of locations within the garage, along with broken PT tendons and corroded anchors were evident in those locations. Areas of inadequate concrete cover over tendons were noted to the extent that the tendon sheathing wore off thus exposing the cables. Quantity summaries and budget estimates for the recommended repairs and preventive maintenance of the garage and plaza was developed by SK&A to initiate a repair program.
SK&A developed schematic sketch and preliminary design details to explain suggested structural repairs of the deteriorated post tensioning tendons. Deficiencies were categorized and repair costs developed based on current unit cost data gathered for the Washington-Northern Virginia Metropolitan Area market. The cost estimate presented took into account the application of a waterproofing membrane over selected areas of the B-1 level garage deck.