Self-tapping screws as reinforcement for rounded dovetail connections

The use of self-tapping screws as reinforcement to improve the structural performance of rounded dovetail connections (RDC) under vertical shear loading was studied. RDC are a versatile concept for connecting two wooden members. RDC without reinforcement were compared with RDC with three different types of reinforcements: joist reinforcement with screws at an angle of 90° between the screw axis and the wood grain of the joist, reinforcement of joist and main beam with screws at an angle of 55° between the screw axis and the wood grain of the joist, and reinforcement of joist and main beam with angled screws crossing each other. The failure modes in shear tests were studied; and the capacity, the load at 3 mm deformation, and the relative vertical deformation at capacity were evaluated using analysis of variance. Self-tapping screws significantly improve the structural performance of RDC. All reinforcement types significantly increase capacity, and stiffness is significantly increased when main beam and the joist are reinforced with self-tapping screws.