Computational simulation of light timber framing connections strengthened with self-tapping screws

Traditional light timber framing systems, comprised of stud to top and bottom plate connections, suffer from relatively low stiffness along compression perpendicular-to-grain of the plates, leading to excessive shortening of studs in mid-rise buildings. Experimental testing of timber stud to plate connections revealed that a reinforcement technique employing self-tapping screws, placed at the top/bottom plate interface, was an efficient way to enhance the connection stiffness and alleviate permanent displacements. In other words, the combination of bonding stress development at the interface of self-tapping screws and timber stud as well as plastic deformation, built up in timber plate in compression perpendicular-to-grain, plays an important role in improving the bearing stiffness/strength of these connections. In this paper, structural performance of light timber framing connections, strengthened with self-tapping screws under gravity loading is investigated, utilising finite element modelling. Continuum damage mechanics framework along with traction-separation cohesive zone technique are incorporated in detecting various failure scenarios and damage propagation for timber components in the finite element modelling. Small-scale unreinforced and reinforced stud to top/bottom plate connections using the Machine Graded Pine timber and high strength self-tapping screws were employed and tested experimentally to calibrate the finite element modelling parameters. Calibrated parameters are then utilised to establish a full-scale light timber framing finite element model. It is demonstrated that finite element models established in this paper can predict the load-displacement response and failure modes of reinforced light timber framing systems.