Combined Bending and Axial Loading in Lumber

Abstract

This paper describes the development of a model for predicting the strength of lumber in bending, and in combined bending and axial loading, on the basis of axial tension and compression behavior of similar members. Both instability and material strength failures are included. The model includes the effects of variability in lumber strength, both within a member and between members. Size effects which predict decreasing strength with increasing member size are incorporated. An extensive experimental program on a large quantity of structural lumber has been used for calibration and verification. Output from the model will contribute to the development of more efficient design methods for wood trusses and other structures where lumber is subjected to combined bending and axial loading.