UBC Theses and Dissertations
Glued-in re-bar connection Malczyk, Robert
The aim of this research was to develop a reliable structural timber connection, which would break by failure of its steel components, thus taking advantage of the lower variability and higher strength of steel. The basic concept of the joint was to glue the reinforcing bars in pre-drilled holes and develop a bond strength stronger than tensile resistance of the bar. This report describes the testing and design of such connections. The joints consist of re-bars and steel plates. Weldable #10 and #20 re-bars were used. The steel plates were cut from flat bar. The re-bars are welded to the steel plates and inserted into the holes, and fixed to the wood by epoxy glue. The holes are drilled on an angle to the grain; 30 degree angle was found to be the most effective. The testing consisted of preliminary pull-out tests used to establish the embedment length needed to induce steel failures. Additional testing examined the behavior of glued-in rod joints used as a beam splice connection, a column foundation joint loaded with horizontal forces, and knee joints as used in a portal frame, loaded with positive and negative moment. Steel failures were observed consistently. A typical portal frame was designed in order to tie the research to practical applications. Internal forces from this analysis were then used as a guide to the magnitude of the forces that can be expected in real life situations. In the last part of this report the necessary design steps for two configurations of glued-in rod joints are presented: 1.Column foundation or beam splice joints. 2.Knee joints. This was performed in order to inform structural engineers how glued-in rod joints work under load, and how they should be designed. Glued-in rod connections have several advantages over presently used systems. They can be manufactured in the glulam plant, using conventional tools, reducing the field work to merely bolting of the joints. The construction method becomes very similar to the erection methods of the steel structures. The elements are connected by bolts or welding. Glued-in rod connections have a great potential to become a safe connection method for the statically indetermined structures. The testing of knee joints showed the possibility of developing a moment resisting connection, which would make glulam more competitive against steel in the area of portal frames widely used for commercial buildings.
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