UNINTENDED COMPOSITE ACTION IN HIGHWAY BRIDGES

All available data on unintended composite action in beam-and-slab bridges are reviewed and the factors that may influence the existence of unintended composite action in noncompositely built beam-and-slab bridges are investigated. Test reports summarized in this paper have shown that the existence of a natural or a chemical bond is the single most important factor in determining whether a noncompositely built beam-and-slab system can be counted on to act compositely. There is considerable evidence that indicates the presence of composite action in bridges in which no provisions were made for such action. This composite action may reduce the stress under a given load by a significant amount. However, the uncertainty surrounding the presence of composite behavior and the difficulty associated with verifying the existence of composite behavior make the assumption of composite behavior in a bridge designed noncompositely a questionable one.