Edge Support

The transverse free edges of the concrete deck slab may need to be strengthened or supported by means of a beam or other component. This mainly occurs at abutments, where the transverse free edge of the deck will interface with some type of expansion device, approach slab, or abutment backwall. At these transverse edges, the deck is usually thickened for a certain width so that it behaves like a concrete beam, or the deck is supported by the end diaphragm. If a cross frame is used at this location, the top member of the cross frame will usually need to be a channel or a W-shape than can provide support to the deck. If a beam used to support this free edge is made composite with the concrete deck slab, Article 9.7.1.4 of the AASHTO LRFD (7th Edition, 2014) allows the beam to be designed with an effective width as specified in Article 4.6.2.1.4.