Experimental investigation of timber-to-steel connection using self-drilling wing screws

Abstract

Self-drilling wing screws are well-suited for hardwood and pressed material boards and are explored as an alternative connector to traditional bolts for connecting thick hot-rolled steel with timber. The wing avoids force-feeding of the screw into the timber which prevents the timber from cracking. However, limited studies were found on the timber-to-steel connection using self-drilling wing screws under shear loading. This paper investigates the shear behaviour and capacity of self-drilling winged screw connections between radiata pine timber and hot rolled steel plate through the experimental test. In addition, tensile coupon tests, screw bending tests, moisture content tests, screw pullout tests, and screw bearing tests were performed to determine the material properties of the steel, timber, and screws. A total of 70 experimental tests were conducted on the timber to steel connection connections with different steel thicknesses (8mm-20mm), timber thickness (15mm-45mm), numbers of screws (1-3), and screw axis angle (45°-90°). The failure mode is theoretically analyzed using Johansen yield theory. The resulting data from Eurocode 5 [24] was compared with experimental results as current AS/NZ standards lack adequate guidance in addressing timber-to-steel connections. From the above comparison, it was found that the Eurocode 5 [24] was under-conservative by 90%. Based on the experimental results, new design equations for calculating the shear capacity of self-drilling winged screws are proposed.