PARKING STRUCTURES. IN: STRUCTURAL CONDITION ASSESSMENT
2005
Although they are classified and constructed as buildings, parking structures are unique. Because they are not enclosed, they are subject to ambient weather conditions, which may vary widely based on the geographic location. In cold climates, they are often exposed to snow, ice, and water, as well as to the corrosive action of deicing salts. Unlike a bridge deck, the inside of a parking structure is not rinsed by rain, and its exposure to chlorides may be aggravated by poor drainage. Parking structures are subjected primarily to loads from moving vehicles, and their roof levels are exposed to weather similar to bridge decks. Since they frequently very large, the experience greater volume changes (temperature, shrinkage, and creep) than enclosed structures, which usually are smaller and are exposed to more uniform temperatures, humidity, and moisture. Restraint of these volume changes can cause cracking of garage structural members, which allows for ingress of water and chlorides and this leads to accelerated deterioration. Parking structure slabs usually are constructed of concrete and are supported by concrete beams and columns, except in rare instances where steel framing is used. The functional and traffic requirements dictate that the open-floor spans be in a range of approximately 55 to 60 ft (16 to 18 m) to allow concurrently for two traffic lanes and two parking lanes. The access to different floors sets the floor height, ramp slopes, and turning radii, whereas the building code requirements affect the magnitude of loads and fire protection and ventilation criteria. Because of the longer lengths of parking structures, volume-change movements have to be accommodated and designed for. Properly specified and designed expansion joints will reduce the effect of volume changes. Also, because of the longer spans of the floor framing system and the moving concentrated loads, the magnitude of floor deflection and vibration will vary based on the structural system. All of these factors make parking structures different from other types of building structures, and assessment of the condition of parking structures has to take these factors into account.
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