Probability-based LRFD for engineered wood construction

The newly developed load and resistance factor design (LRFD) specification for engineered wood construction in the United States uses probabilistic methods as the technical basis for selecting design strength requirements, load combinations and load factors. Special characteristics of wood and wood products as structural materials are considered. The strength of wood structural products depends on the rate of application and duration of the loads. LRFD criteria for the ultimate limit states account for this dependence by means of a time effect factor. The apparent increase in strength of wood structural systems comprised of several nominally identical and repetitively used members is taken into account with a system factor. Serviceability limit states of deflection and vibration are addressed with some general code guidelines and a nonmandatory commentary.