Probabilistic Analysis of Timber Bridge Decks

Reliability indices are calculated for single timber beams and timber bridges with deck planks and stringers. Load and resistance models are developed on the basis of the truck survey and material test data available. Three common groups of species and two material grades are considered. The reliability indices are calculated using the Rackwitz and Fiessler procedure for the single beams, and Monte Carlo simulations for the whole bridges. The reliability indices for single beams are about 15–40% lower than those for whole bridges. The difference can be attributed to a distribution of load between the stringers because of the mechanical properties of wood, in particular the modulus of elasticity, modulus of rupture and their correlation.