Combined Load Capacity of Threaded Fastener‐Wood Connections

Abstract

Threaded fastener‐wood connections using lag screws, wood screws, and the like are commonly loaded with forces having components both parallel and perpendicular to the fastener axis. Metal side plate‐to‐wood connections with a single fastener are tested in pure withdrawal loading (90°), pure lateral loading (0°), and loading at 22.5° increments between the two extremes. Two sizes of standard lag screws and one size tapping screw are tested with southern pine and spruce‐pine‐fir main members. The experimental results show that relatively small deviations from pure lateral or pure withdrawal loading may be conservatively ignored. There is minimal interaction between lateral and withdrawal components of the maximum capacity of lag screw connections. Design values are derived by applying different safety factors to either the test, load at a limiting lateral deformation or the ultimate withdrawal load. An interpolation function such as Hankinson's formula or a second‐order interaction conservatively describes the effect of load angle on computed allowable loads.