PERFORMANCE OF STRUCTURAL WOOD PRODUCTS: PRODUCER RESPONSIBILITIES AND CUSTOMER EXPECTATIONS

摘要

Standards for structural wood products throughout the world contain a variety of implicit and explicit levels of performance targets. For example, in North America, one frequently quoted historical strength-based performance target for flexural members is that the near-minimum flexural strength (often selected to be the 5th percentile of the assumed population) meets or exceeds 2.1 times the published allowable bending design value. Over the decades since these targets have become embedded in standards throughout the world, structural wood products and their applications have significantly evolved. For example, engineered wood products such as structural composite lumber (SCL), glued-laminated beams (glulam), and various types of wood trusses and I-joists continue to expand the range of applications achievable by structural wood products. This paper recalls the historical basis of the traditional performance targets in a variety of codes and standards throughout the world. The discussion proceeds with the potential pitfalls of oversimplifying performance targets and explores the various levels of performance verification that are required for one product versus another. Perspectives are provided from various user groups regarding their performance expectations for structural wood products. Potential discrepancies between customer expectations and verifiable performance levels are identified, and the responsibility for verifiable product quality is placed squarely on the shoulders of the manufacturer. The paper concludes by asking the audience whether our international structural wood standards provide adequate verification of performance levels across a range of products, given the potential pitfalls that have been discussed. It also asks whether manufacturers can provide verification of the performance levels for their products, and whether they fully understand that they - not the codes or standards or 3rd party agencies - are responsible for their product quality and safety in applications.