Influence of fastener size on lateral strength of steel-to-wood screw joints.

摘要

Single shear steel plate to wood screw joints were tested to study the influence of screw diameter on lateral strength for load parallel to grain or perpendicular to grain. Joint tests encompassed use of steel wood screws with shank diameters of 4.2 mm (by 51 mm long) and 5.5 mm (by 76.4 mm long); steel self tapping screws of 6.1 mm diameter (by 76.4 mm long); and steel lag screws of 6.4 mm diameter (by 76.4 mm long). In addition, embedment tests were conducted using these fasteners and two other screw sizes (2.86-mm wood screw and 7.8-mm lag screw). Although in general the failure mode and strength depended on both the direction of loading and the screw diameter, differences between strengths parallel to grain and perpendicular to grain increased in proportion to screw diameter. There was only a small effect of loading direction for joints with 4.2-mm-diameter wood screws and less, although subsidiary embedment tests revealed that convergence of the strengths in the two loading directions occurred at shank diameters of about 3 mm and less. Existence for steel screws of a threshold fastener diameter below which the direction of loading has no influence on joint strengths is consistent with prior findings for nails or bolts. Based on the new data and synthesis of earlier data, it is concluded that structural design practices need only account for the influence of loading direction on lateral strengths of screws when fastener diameter is greater than 4.2 mm..