Study on the strength mechanism of the wooden round-end mortise-and-tenon joint using the digital image correlation method

The aim of this study was to reveal the strength mechanism of the mortise-and-tenon (M–T) joint at a deeper level. The effects of tenon fit on bending and withdrawal load resistances, and strain distributions outside and inside beech (Fagus sylvatica) wooden round-end M–T joints were experimentally investigated using mechanical testing synchronizing digital image correlation method (DICM). The results showed that (1) the tenon fit had greater significance on withdrawal properties than that of bending properties of M–T joints; (2) the bending load resistance was linearly proportional to withdrawal load resistance based on both theoretic analysis and regression methods; (3) strain distributions outside M–T joints during the loading process were not sufficient to evaluate the mechanical behaviors of the M–T joint; (4) strain distributions inside M–T joints showed that the maximum strains on top and bottom parts of the tenon were significantly greater than that of middle part, but the difference decreased with the growth of tenon fit; (5) the method of determining the optimal tenon fit of the M–T joint based on the DICM was proposed, and optimal tenon fit of beech wooden round-end M–T joint evaluated ranged from 0.4 to 0.5 mm.