A probabilistic approach for analysis of wood bridges is discussed. Load and resistance parameters are treated as random variables. The statistical models are derived on the basis of truck surveys, test data, and analysis. The mean maximum 75-year live load is calculated for single- and two-lane bridges. For low-volume roads, the maximum moments can be reduced by about 10%. Resistance is considered for timber stringers, glued-laminated (glulam) girders, and stressed decks. A considerable variation of modulus of rupture (mor) is observed for sawn lumber. The degree of variation of mor is considerably reduced in case of glulam girders and stressed decks. Reliability is a convenient measure of structural performance. Reliability indices are calculated for three structural types. The effect of traffic volume is negligible for timber stringers, but it can be considered forglulam girders and stressed decks. This paper appears in transportation research record no. 1291, Fifth international conference on low-volume roads, may 19-23, 1991, raleigh, north carolina, volume 1.
Abstract