Improved fastening designs for bridge decks made of mechanically-laminated timber

Abstract To develop improved fastening designs with competitive characteristic values such as stiffness, load capacities and energy for Mechanically-laminated Timber (MLT) bridge decks, monotonic tests were conducted on double-shear connections made of galvanized spiral nails of two diameters (4.68 mm, 7.24 mm), three-type self-tapping screws of two diameter (5.80 mm, 5.95 mm) and two fastening orientations (90-degree, 45-degree to loading direction) via a universal electromechanical testing machine. It was found that screws showed better performance in terms of load capacities and energy accumulated at peak load, and, 45-degree fastening tended to give better results in terms of stiffness than 90-degree fastening. The fastening designs of 45-degree oriented screws of zinc coat partially threaded/zinc coat fully threaded were recommended for their 40%/14% higher stiffness, 22%/48% higher yield load capacity, 7%/18% higher peak load capacity, and 66%/71% higher energy accumulated at the peak load than those values of the reference group (i.e., 90-degree fastening of galvanized spiral nail of 4.68 mm diameter).