The effect of gap size on performance of metal plated joints in compression

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Virginia Polytechnic Institute and State University


Metal plate splice joints with gaps between butting pieces of lumber were tested in compression to evaluate the effect of gap size on joint serviceability performance. The current design methodology for compression splice joints was also evaluated. Specimens representing floor and roof trusses, with 16 and 20 gauge plates of staggered and aligned tooth configurations were tested for each of two gap sizes.

Generally, 20 gauge plates and 16 gauge plates with 1/8” gaps buckled under compression loads while 16 gauge plates with 1/16" maximum gap did not buckle before the gap closed; rather, the gap closed primarily due to slippage between the teeth and the wood. 16 gauge plates generally outperformed 20 gauge plates based on serviceability performance of the test compression splice joints. Furthermore, gap size had less of an influence on joints with 16 gauge plates than on joints with 20 gauge plates.

The current practice of sizing plates for compression splices to withstand one-half of the calculated chord force could not be physically confirmed using the study joint serviceability criteria. The test results indicate that basing allowable plate ratings on a per area basis derived from tension tests is misleading.