Double-Sided STS-CLT Connection for a Modularized Building System

Abstract

Cross laminated timber (CLT) is a lumber-based engineered wood product characterized by supreme mechanical performance, CNC fabrication capability, and panelized building system, making CLT a good building material for volumetric modular construction. However, most of the connections used in the CLT are transferred from the light- or heavy-frame wood construction with deficient stiffness and strength characteristics which can only provide vertical or horizontal connectivity. This study focused on the development of a CLT connection comprised of self-tapping screw (STS), and steel plate that could offer both vertical and horizontal connectivity. Three types of double-sided STS arrangement were investigated: Type 1 was the traditional 45° inserted STS parallel-to-grain, Type 2 was the 45° horizontally inserted perpendicular-to-grain on the opposite direction of each side of the steel plate, and Type 3 was a combination of Type 1 and Type 2. It was found the Type 3 was the most efficient connection in terms of strength and ductility. Type 3 resulted in an increase in the peak load and ductility by 28% and 33%, respectively compared to Type 1. It was concluded that the proposed connection arrangement was promising for both vertical and horizontal connectivity with adequate stiffness and strength.