ABSTRACT
For conventional concrete deck-over-steel stringer bridges, full composite action is usually preferred and achieved due to the ef‘ciency of the materials used. In the American Association of State Highway and Transportation Of‘cials (AASHTO) code slab-on-girder bridges can be designed for either noncomposite or full composite actions. No partial composite action is de‘ned. However, ‘ber-reinforced polymer (FRP) decks are usually designed in practice for partial composite action. Several limiting practical factors lead to this behavior: (1) The hollow core con‘guration of FRP panels and lack of continuous connection at the panel-stringer interface do not allow development of perfect contact and attachment between decks and connections. (2) The high modulus ratio between the steel girder and FRP panel (about 30 compared to 8-10 for a conventional concrete deck-over-steel girder) makes the contribution of the FRP deck to the overall bridge stiffness much less signi‘cant. (3) The practical connection spacing of about 0.6 to 1.2 m for FRP decks, compared to conventional concrete deck connection spacing of 0.15 to 0.25 m, is too large to develop full composite action. All these factors in turn lead to less shear force to be transferred at the deck-girder interface, leading to slippage and achieving a partial degree of composite action. On the other hand, it may actually be desirable to allow for some degree of deck-stringer relative displacement to account for differential thermal expansions between FRP and steel.
