Effects of Slab Post-Tensioning on Supporting Steel Beams in Steel Framed Parking Deck Structures

AISC Design Guide 18, Steel Framed Open-Deck Parking Deck Structures, discusses the use of cast-in-place post tensioned concrete slabs in steel framed parking structures. In Section 3.3.2.1 of Design Guide 18, the authors reflect on the manner in which the post-tensioning force is resisted by and affects the supporting beam: in a noncomposite or composite manner. They conclude that the post-tensioning force is carried almost entirely in a composite manner (minus effects of shrinkage and elastic shortening). This conclusion is based on results of unpublished research and is corroborated by earlier design guidance. The objective of this field study is to quantitatively assess the effect that slab post-tensioning forces have on their supporting steel members.