World Trade Center Parking Structure Restoration
Walter P Moore performed an emergency assessment of the World Trade Center garage. The parking structure was suffering full depth cracks in the slab which led to corrosion, concrete delamination, concrete spalls, and broken tendons. The structural system is composed of a precast double T with an alternating cast-in-place slab tied together with post-tensioned (PT) tendons. The broken tendons, caused by water infiltration, were impacting the structure’s capacity and safety. Since the garage is used by LA commuters and the structure above is used by a school, we needed to limit the parking spaces used during construction and minimize revenue loss for the owner.
Typically, a screw driver test is used to determine whether or not a PT tendon is stressed, although the test is time consuming with limited results. As an alternative methodology, we used a “lift-off” test. This process requires the use of a ram to pull the tendon’s tail until the anchor wedges released. If tendon stress is too low it can quickly be re-stressed, and multiple tendons may be tested within one opening. Before Walter P Moore was consulted, the restoration was expected to take 3 months. By strategically locating exploratory openings where the worst case was expected, we cut the restoration time in half. Areas were identified by looking for cracks and signs of water infiltration. Over 230 tendons were tested and 16 tendons were restored. Walter P Moore is now providing a full garage assessment, along with construction documents and construction administration services, to further rehabilitate the structure and prevent future deterioration.