The enhanced performance of split-ring connections through prestressing

Abstract

This paper examines the concept of enhancing the performance of timber connectors in truss joints by the introduction of transverse prestressing. The behaviour of lap splices of Douglas fir, with 63 mm split-ring connectors and end distances of 50, 100, 150, and 210 mm, was examined for various levels of prestress in a laboratory study. As well, the magnitude of the load that can be carried by the connection through friction between faying surfaces was also assessed for various levels of prestress. The simple technique used in the laboratory for introducing prestress is described. Results of the laboratory tests on 20 joint configurations are presented, and the experimentally determined strengths are compared with the calculated resistances using the provisions of CAN\CSA-086.1-M89 "Engineering design in wood (limit states design)." Key words: timber, connector, prestress, truss joint.

Effects of pretension in bolts on hysteretic responses of moment-carrying timber joints

“…1,2 In the fi eld of timber connections, especially with dowel-type fasteners, a similar improvement could also be achieved by introducing pretension to their fasteners. Through a monotonic test, Quenneville and Dalen 3 demonstrated that pretension in bolts enlarged the initial stiffness of split-ring timber joints besides increasing their lateral load-carrying capacities. Because loss of prestress (stress on wood member due to fastener pretensioning) may occur due to various factors, 4,5 a minimum prestress level of 690 kPa at the time of construction has been recommended.…”

“…6 Higher prestress levels (1500 kPa and 3000 kPa) were also applied to the bolts of split-ring joints to improve their structural performances. 3 In spite of its general application, the dowel-type timber joint is characterized by a very low stiffness at initial loading due to the existence of lead-hole clearance. 7,8 Increasing the initial stiffness or load-carrying capacity of timber joints with dowel-type fasteners therefore could be done by applying pretension to the bolts.…”

Combined effects of end distance and spacing on the resistance of split ring connectors loaded in tension

“…Quenneville and Van Dalen (1991) have already discussed these papers and brought forward the fact that Scholten's latest work was the most extensive research project on the subject, and many of the criteria governing the design of connections included in current design standards originated with his work. However, little work was done by either one of them on multiple connector joints with an aim of assessing the combining effects of connector spacing and end distance.…”