Flexural performance of cross-laminated timber made out of poplar reinforced with nail and screw

In this study, flexural performance of cross-laminated timber (CLT) made out of poplar wood (Populus alba), Polyurethane adhesive and different mechanical connectors were investigated. Amount of adhesive was 300 g/m2. For manufacturing CLT panels, wood planks were air-dried, then four face-bonding surfaces of planks were planed (S4S). Thickness and width of planks were 19 and 100 mm, respectively. The thickness, width and span to depth ratio of Three-layered CLT specimens for bending test were 57, 80 mm and 12, respectively. Bending test was conducted by Instron 4486. The variables of this study were including different connectors (galvanized steel nail, strip brad nails (ST Nails) and coarse thread drywall screw), connector number (2 and 4), adhesive (with and without adhesive) and panel direction (major and minor direction). The results showed that the higher modulus of rupture (MOR) and modulus of elasticity (MOE) were related to major direction of CLT panels connected by 4 screws and adhesive as well the lower of them were related to minor direction of CLT panels connected by 2 ST nails and adhesive. The results also showed that MOR and MOE of CLT panels were changed about 71 and 16, 16 and 400, 1 and 10%, respectively with the change of shear connector, adhesive and number of connector. MOR and MOE in major direction of CLT panels were about 3 and 4 times higher than those in minor direction. The results revealed that MOR of CLT panels meet the specified requirements of ISO 16696-1 standard, however, MOE of them were not comparable with standard value. Hence, it was recommended to perform some comprehensive studies for reinforcing CLT panels made of poplar for increasing their MOE.