With the recent concern toward wood utilization in large-scale structures, increasing the strength performance of structural elements is important. Developing structural elements using board materials is one of the measures to increase the strength performance. A high-performance nailed joint to resist shear loading is necessary to increase the strength performance of wooden structural elements using board materials. This study was conducted in order to understand the shear properties of nailed joints intended for large-scale structures. Shear tests were conducted with nailed joints using structural plywood, medium density fiberboard, or particleboard. The yield resistance was determined from experimental load-slip displacement curves, and was also calculated using European yield theory (EYT). Consequently, the nailed joint specimens using MDF showed an experimental yield resistance higher than those using structural sugi plywood. The nailed joint specimens using PB also showed a high value similar to that of the joints using structural karamatsu plywood. The yield resistance of most of the joint specimen series calculated using European yield theory showed slightly higher values than the experimental yield resistance. This study observed the deformation behavior around the nail head under shear loading. No deformation was observed from the appearance at the initial region of the test. The nail head started a rotational deformation when the joint started yielding. Moreover, the side panel became partially embedded. The nail head was completely embedded at the maximum load of the specimen. Nail pull-out from the base material was not remarkably evident. This deformation behavior was observed in all the board materials used in this study.

To investigate the influence of preservatives on bond durability of glued-laminated-timber (GLT), sugi (Cryptomeria japonica D.Don) laminae were impregnated with five kinds of wood preservative (ACQ, NCU, CUAZ2, NZN, and AAC), and 5-ply GLTs of low and high density were fabricated using resorcinol-formaldehyde (RF) and phenol-resorcinol-formaldehyde (PRF) resin adhesives. They were subjected to 10 years of outdoor exposure testing, and after 1, 3, 5, and 10 years of exposure, block-shear tests were conducted. As the result, bond shear-strength decreased with exposure duration regardless of adhesive resin in GLT treated with ACQ, NCU, and CUAZ2, which contain copper as the main ingredient. The rate of decrease of bond shear-strength of GLTs treated with ACQ, NCU and CUAZ2 was greater when using RF than when using PRF. Comparing the bond shear-strengths of high and low density GLTs, it was recognized that decrease of bond shear-strength was greater for high density than for low density GLTs. Decrease of wood-failure ratio with exposure duration was low for all GLTs.

To investigate the influence wood preservatives on glued-laminated-timber (GLT), sugi (Cryptomeria japonica D.Don) laminae were treated with five kinds of wood preservative (ACQ, NCU, CUAZ2, NZN, and AAC), and 5-ply GLTs with low and high density were fabricated using resorcinol-formaldehyde (RF) and phenol-resorcinol-formaldehyde (PRF) resin adhesives. They were subjected to 10 years of outdoor exposure testing, and after 1, 3, 5, and 10 years of exposure block-shear tests were conducted. As the result, for GLTs treated with ACQ, NCU, or CUAZ2, which contain copper as the main ingredient, the specimens sawn from both lateral sides were more degraded than the specimens sawn from the middle part. In GLTs treated with ACQ, NCU, or CUAZ2 the glue-layers closer to the upper horizontal surface tended to show greater deterioration. In addition, in some GLTs the lower glue-layers also deteriorated. From the results of the specimens sawn from the west side of GLTs exposed outdoors, of exposure tests of 2 years, and of accelerated-aging tests using block-shear specimen with 10 mm and 25 mm width, reduction curves (plots of deterioration vs. exposure time) of shear-strength were obtained and compared. The reduction curves of GLTs exposed outdoors were similar to those of the outdoor exposure tests using block-shear specimen of 25 mm width.