Duration of load and probability of failure in wood. Part II. Constant, ramp, and cyclic loadings

Abstract

A generalized model for damage accumulation is used to study the probability of failure of a wood member in bending for different load histories. The variability in time-to-fracture corresponding to a given load history is accounted for in the generalized model. Four types of loads are considered: (1) a constant load, (2) a ramp load, (3) a cyclic load of constant cycle amplitude, and (4) a cyclic load of random cycle amplitude. In each case, the probability of failure is studied as a function of the factor [Formula: see text] which, in the design equation, is applied to the 5th percentile of the short-term strength distribution to obtain the design stress. Snow loading is considered as an example of cyclic load with random cycle amplitude.