Limit‐State Interactions in Reliability‐Based Design for Wood Structures

Abstract

Strength and serviceability limit states are closely interrelated in wood construction. The design of wood beams is often governed by limits on deflection, and the resulting section is larger than that required for flexure or shear strength. Moreover, members used in light‐frame construction are chosen from standard available dimension lumber sizes. Relatively few sizes are available for wood in comparison to the number of standard shapes available in steel construction. As a result, the sections selected in wood design may be significantly larger than what would otherwise be required by the design equations. This paper addresses the additional reliability gained with respect to ultimate strength by including the deflection limit state and by considering the availability of standard sections for individual wood members and parallel‐member systems. The significance of system effects from load sharing in serviceability reliability is assessed. The implications that these effects have for the ongoing development of load and resistance factor design (LRFD) provisions for engineered wood construction are examined.