Long Span Parking Structures are typically constructed of one-way post-tensioned slabs supported by post-tensioned beams. The girders have an approximate bay size of 18' by 60'. For multi-level structures the ramping is most commonly designed with a slope of 5% to 6% to accommodate parking along the ramps. Other types of ramps can also be facilitated such as the use of a speed ramp without parking spaces. Vertical shear requirements are typically addressed by using either shear walls or moment frames. Long span parking structures have some of the most efficient parking layouts, accomodating the most parking spaces for a given space.
Steel Beam Forms and Deck Tables are the most commonly use method to form cast-in-place long span parking structures. In general steel beams have width of 14" at the bottom with a 1" draft on each side which develops a 16" width at the top of the beam. The width can vary from 12" to 24" wide. The overall beam height including the slab thickness normally varies from about 30" to 36", but the height and width should be designed at a common dimension throughout the entire project to be the most economically efficient. The steel beams are fabricated full length (60') with the shoring for the beam and deck tables attached. This allows the entire beam section to be set, stripped and towed, all in one piece. Once the beams and shoring are erected and aligned the deck tables are brought in and set between the beams.
Gang Wood Beam Forms and Deck Tables are the same as the steel beam and table system, except, rather than the beams forms being steel they are fabricated out of wood. This method is used in lieu of steel beams because of size constraints or re-use. Other than the beam configuration the system is very similar to that of the steel beam system.
Hybrid – Pre-cast Columns & Beams with Deck Tables is a combination of precast support elements (columns and beams) with cast-in-place slabs spanning between the beams to create a hybrid composite structure. Columns are typically set full height in conjunction with corresponding beams then plumbed and braced. This erection operation is typically done in quadrants due to the weight of the pre-cast members and capacity of the crane. Once the erection of the pre-cast is complete the shoring for the suspended slab is brought in and erected between the pre-cast beams, reinforcing steel and post-tensioning is installed and the slabs are placed. In most geographical areas some type of shear elements are required by structural design. The two typical methods are; perimeter moment frames or shear walls. There are pros and cons for both types of shear elements, but ultimately the end user along with the designers input will determine what suites the project the best.
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