An Ultimate Load Test to Study Bracing Effects of Bridge Decks

The objective of this research project was to study the possible bracing effect of a bridge deck on the lateral instability of the stringers. The capacity of bridges is frequently underrated due to conservative assumptions regarding unknown conditions. Traditionally, the stringers have been taken to be laterally unsupported along the span, thus leading to conservative estimates of the bridge capacity. A full-size laboratory test was conducted on a 24-foot-span multi-girder bridge comprising five steel stringers supporting a wood deck, to demonstrate the bracing effect of the deck. It was seen that the bridge failed by lateral buckling of the bridge beams. The test bridge capacity was twice the unbraced capacity (assuming no bracing from the deck).