Load and Resistance Factor Design for Engineered Wood Construction: A Pre-Standard Report

The information contained in this pre-standard report is intended to provide guidance to writers of a load and resistance factor design (LRFD) specification for engineered wood construction. The report contains procedures and a methodology to determine resistance factors for forest products used in engineered wood construction. The resistance factors were developed using concepts of probabilistic limit states design which incorporated state-of-the-art load and resistance models and statistical information, and they are consistent with the rationale used in determining load factors and load combinations in ANSI A58—Building Code Requirements for Minimum Design Loads in Buildings and Other Structures. The phenomena of load duration (creep-rupture) was researched and a load-duration factor, λ\N, was developed. This load duration factor incorporates a stochastic load process model as well as a damage accumulation model. Resistenance and design equations, including buckling and ponding, are formulated in terms of load capacities. Fire and serviceability limit states are discussed. Additional factors which account for quality control, data sample size, and numerous forest products with different variabilities, are also presented.