Effect of crossbanded laminates on the bearing properties of mechanical joints of laminated veneer lumber with a drift pin
2006
Kawazoe, M.(Kyoto-fu. Forest Experiment Station, Wachi (Japan)) | Tuchiya, Y. | Mori, T. | Komatsu, K.
To investigate the effects of crossbanded laminate ratios in laminated veneer lumber (LVL) on its bearing properties, tension-type bearing strength tests of drift-pin joints were made. The LVLs of parallel laminates and two types crossbanded laminates were made of rotary-cut veneers of sugi (Cryptomeria japonica D. Don). Deformation rates (embedding speed of the drift-pin) of the tests were 5, 5O and 500 mm/min. The test results were approximated by a perfect elasto-plastic relationship. Conclusions were as follows: 1) The parallel laminates LVL showed brittle fracture with a small embedment of the drift-pin However the LVL with crossbanded laminates showed very ductile behaviors, since the drift-pin could be embedded into them continuously. From observations of crossband veneer fracture in the LVL, it became clear that the wood fibers of the crossband veneer resisted the embedment of the drift-pin. 2) Initial stiffness decreased with increasing crosssband veneer ratio in the LVLs. The stiffness of LVL with a 40% crossband veneer ratio became from 50% to 60% of that of the parallel laminates LVL. However, the ultimate bearing stress tended to increase with increasing crosssband veneer ratio of the LVL on condition that the deformation rate of the tests was fast. 3) The ductility ratio (yield embedment deformation to ultimate embedment deformation) became from 16 to 23 for the LVL with crossbanded laminates, while for the parallel laminates LVL it was less than 2. The bearing energy of the LVL with crossbanded laminates became from 24 times to 35 times greater than that of the parallel laminates LVL.
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