Impact of Moisture Cycling on Screw Withdrawal Capacity of Treated and Untreated Radiata Pine

Abstract

The increased use of wood products for construction has intensified the need to understand how moisture affects the mechanical properties of timber connections. The withdrawal capacity of dowel-type fasteners, such as screws, needs to be measured, or estimated, for the design of timber systems having connections with axially loaded dowel-type fasteners. The influence of the moisture content changes on the timber is often examined, but its effect on the mechanical performance of connections is poorly considered, including the design codes. This work examined changes in the screw withdrawal capacity in light organic solvent preservative-treated and untreated Radiata pine with type 17 screws inserted perpendicular and parallel to the grain and subjected to repeated wetting and drying cycles. A comparison of the screw withdrawal capacities with those predicted from Australian and European codes was performed. The results presented here are part of a larger project that includes the study of embedment strength and lateral resistance in combination with different wood treatments and pine species.