Location: 30.36301° N, 89.09872° W
This parking structure in Gulfport MS is an oceanfront, six-story (seven-level) garage constructed of precast concrete columns, spandrel beams, and pre-tensioned double-tee deck with cast-in-place reinforced concrete topping. The central ramp between the 1st and 2nd stories collapsed. It is hypothesized that the deck failed in negative-bending flexure when storm surge caused unloading of the deck beams. When the downward load due to self weight was negated or reduced by the upward load due to the storm surge, the internal moment from the prestressing caused the concrete in the flange at midspan to rupture in tension.
The dimensions of the structure are approximately 200 ft by 450 ft by 70 ft high, arranged in a rectangular grid of 4 by 15 bays. The collapsed ramp measures 2 by 5 bays, approximately 100 ft wide by 150 ft long, in the center of the structure. The ramp sloped down toward the Gulf. Figure 1 shows the parking structure from the northwest. Figure 2 shows some of the collapsed deck beams. Figure 3 shows evidence of uplift and dropping of the second-story deck adjacent to the collapsed portion. Note the seaweed or grass trapped between the 2nd-floor deck web and the reinforcement in the girder, implying repeated uplift and dropping, and hence the possible value of better positive connection between the deck beams and supporting girders. Figure 4 shows the shear keys that support the end of deck beams at the spandrel. The structure is located perhaps six ft (2 m) above sea level. Its exposure category according to ASCE 7-02 is C.
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Submitted by Keith Porter and Gilberto Mosqueda
September 12, 2005