RELIABILITY-ANALYSIS FOR HIGHWAY BRIDGE DECK ASSESSMENT

An assessment procedure based on structural system reliability princip les, has been developed for highway bridges with concrete or composite decks. It concentrates on the ultimate flexural limit state of slabs and takes account of the fact that the failure of the structure is dep endent on the combination of the applied loads, their variability, bot h spatial and in amplitude, and on the variability of geometric and ma terial properties. Recognising that each of a number of topologically distinct collapse mechanisms may contribute to the overall probability of system failure, an optimisation technique is used in conjunction w ith structural reliability analysis in order to establish for each mec hanism the critical geometry and the associated probability of occurre nce. The procedure can be implemented in the assessment of existing br idge structures, where the use of plastic analysis may reveal strength reserves not utilised in design and, hence, alleviate the need for st rengthening. By modelling the bridge as a virtual series system and an alysing a finite number of collapse mechanisms, bounds on system failu re probability in flexure can be estimated. An example of its intended use is presented for a solid slab concrete bridge deck.