Double tee

The strong bond of the flange (horizontal section) and the two webs (vertical members, also known as stems) creates a structure that is capable of withstanding high loads while having a long span.

[1] The developments of double tee were started in the 1950s by two independent initiatives, one by Leap Associates founded by Harry Edwards in Florida, and the other by Prestressed Concrete of Colorado.

They designed the wings to expand the structural channel in order to cover more area at a lower cost.

[2] In 1951, Harry Edwards and Paul Zia designed a 4-foot (1.2 m) wide prestressed double tee section.

The list included 8DT24 that were proven to be the most popular double tee type used for 60-foot (18 m) spans for several decades.

Double tees are connected during the construction without topping with concrete to create the parking structure floor surface.

[6] A benefit of pre-topped double tees is a higher quality concrete for more durable surface to reduce traffic wears.

[6] In case that the cracks are developed after the parking structure is already in use, other methods to provide external support to the double-tees are needed.

[9] NEXT Beam development started in 2006 by the Precast/Prestressed Concrete Institute (PCI) North East to update regional standard on Accelerated Bridge Construction (ABC).

The use of double tees with wide flange permits fewer beams and to have them stay in place to form the deck, resulting in a shorter construction time.

The design was called "NEXT D" with 8-inch (20 cm) flange thickness that does not require deck topping, allowing the wearing surface to be applied directly on to the beams.

To reduce these problems, many methods have been developed to manage the lateral connections of the double tees.

Additionally, the ceiling can be raised higher as double tee wall members can have long spans also.

[14] Precast Prestressed Concrete Institute included double tee wall panels in its PCI Design Handbook between 1971 and 2010.