Capacity of built-up bolted timber splices

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University of New Brunswick


This report describes the Capacity of Built-up Bolted Timber Splices when a bending moment is applied. Particularly how thick a wooden element is needed to force failure to occur in the bolt and not in the wood. This report discusses; the moment capacity, the mode of failure, a beam width to bolt diameter ratio, side plate friction effects and moisture content effects on the capacity of the built-up bolted timber splices. Twenty-three test beams of varying widths were assembled and tested in the A-2 Structures Lab at the University of New Brunswick. A baldwin test machine was used to apply a 3-point middle third bending moment load. An ultimate bending moment capacity of 16.9 kNm was achieved by the five ply specimen group. The three ply specimen group achieved a value of 16.0 kNm. This group, which had a beam width to bolt diameter ratio of 9, was chosen to be the most efficient and economical beam. In the two ply specimens, the connection failed by full bearing (i.e. crushing) of the wood members. In the four and five ply splices, bending yield of the bolts was exceeded with no crushing of the wood. The three ply specimens had both full bearing and bending yield exceeded. It is recommended that the test methods should include torquing of the bolts and varying the moisture contents of the samples. A study could also be completed in which one beam width was studied with a variety of bolt diameters.