Shear behaviour of timber connections with transversal dowel fasteners and verification of analytic formula

Abstract

This study mainly explored the shear behaviour of self-tapping screws intended for reinforcing timber structural joints Shear tests and relevant supplementary tests were conducted to measure the shear strength and ductility of fasteners as well as the failure mode of the entire components The species of the structural Chinese fir (Cunninghamia lanceolata) and Japanese cedar (Cryptomeria japonica) types of fastener (fully-threaded or half-threaded self-tapping screw) and use of washers served as the experimental parameters of shear tests for examining the effects of timber species and joints’ profiles The shear test is carried out by 20-ton universal testing machine The experimental results were compared to the shear values calculated based on European Union (EU) timber structure design code in order to evaluate the feasibility about applying the equation for predicting timber joints with self-tapping screws as dowel type fasteners in Taiwan According to the results of the shear tests the maximum capacity and rigidity were significantly affected by the physical properties of materials particularly wood While the species of wood dominate the ultimate shear strength the washers influence the failure mode Regarding the effect of fasteners on shear behaviour however no significant difference was observed in the effect of fully-threaded or half-threaded self-tapping screws within the joints Calculation results based on EuroCode 5 Equation 8 7 revealed that the (h) value represented the theoretical shear strength The analytic values and experimental results exhibited a discrepancy between 16% and 51% for eight specimens The testing results were greater than the theoretical values suggesting relatively conservative estimation consequences With regard to the failure mode however the accuracy of prediction is insufficient and the equations might require further modification for Taiwanese wood

Date of Award	2019
Original language	English
Supervisor	Yu-hsiang Yeh (Supervisor)