CLT panels consist of several layers of lumber stacked crosswise and glued together on their faces. Prototype Sugi CLT floor panels were manufactured and bending and internal shear tests were carried out under the different parameters of lumber MOE, number of layers, thickness of lumber and thickness of CLT panels. On the basis of above tests, internal shear strength, bending stiffness and moment carrying capacity were estimated based on the lumber properties by Monte Carlo method. Bending stiffness EI of CLT panels could be estimated by adopting parallel layer theory and equivalent section area. Experimental moment carrying capacity showed 12% higher value than the calculated moment carrying capacity by average lumber failure method, and also showed 45% higher value than the calculated moment carrying capacity by minimum lumber failure method due to the reinforcement of the outer layer by the neighboring cross layer. Experimental internal shear force of CLT panel showed 30% higher value than the calculated one.
Journal of Structural and Construction Engineering: Transactions of AIJ
Summary
Cross Laminated Timber (CLT) panel is consisted of several layers of lumber stacked crosswise and glued together on their surfaces. In Europe, mid-to-high-rise building using CLT has been already built. Recently, CLT structure attracts attention in Japan as one of the means to promote Wooden Public Buildings. Since the lamina can utilize small or middle diameter wood as the raw materials, expansion of CLT demand would promote local forestry and wood industry. There are various joint methods of CLT such as LSB joints, screw joints with steel side-plates, and so on. In this study, we examined tensile bolt joint which is one of the effective joint methods of the end of panel when the wall panel showed rocking behavior, assuming architectural structure using the panels of around 1-2m in width.
CLT wall panels having an opening were subjected to horizontal loading and the failure process of CLT around the opening was compared with the simulation by Finite Element Method. Three types of CLT wall panels of 3500mm length and 2700mm height had an opening of 1500mm length and 900mm to 2000mm height at the center of the wall panel. During the racking test of wall panel cracks appeared at the corner of the opening. The wall panel was modelled with three models. One included a single orthotropic plane element calculated from the mechanical properties parallel and perpendicular direction of lamina layout (Model I). Another included two orthotropic plane elements crossed each other and connected at each nodal point based on the mechanical property of lamina composing the panel (Model II). The third model included laminae of 30-by 120mm cross section arranged vertical and horizontal directions (Model III). The simulation by each model predicted comparatively well the initial shear stiffness of CLT wall panels and the initiation of cracks at the corner of opening.
Cross-laminated timber (CLT) panels consist of several layers of lumber stacked crosswise and glued together on their faces. Prototype sugi CLT floor panels were manufactured and bending tests were carried out under the different parameters of lumber modulus of elasticity (MOE), number of layers, thickness of lumber and thickness of CLT panels. On the basis of above tests, bending stiffness and moment carrying capacity were predicted by Monte Carlo method. MOE of lumber was measured by using grading machine and tensile strength of lumber was assumed to be 60 % of bending strength based on the obtained bending test. Bending stiffness EI of CLT panels could be estimated by adopting composite theory and equivalent section area. Experimental moment carrying capacity showed 12 % higher value than the calculated moment carrying capacity by average lumber failure method, and also showed 45 % higher value than the calculated moment carrying capacity by minimum lumber failure method due to the reinforcement of the outer layer by the neighboring cross layer.
Cross Laminated Timber (CLT) is a new material for midrise timber structures. CLT panels made of Japanese species like Sugi (Cryptomeria japonica D.Don) are developed in Japan. Seismic resistance of CLT structures are mainly determined by the performances of panel-to-panel connections. One of the main fasteners for CLT connections is large size self-tapping screws. It is possible to use not only CLT panels but also glulam structures. But there are few data for these joints and not used so much in Japan. In this study, shear tests of timbet-to-timber joints including CLT panels with large size self-tapping screws and several material tests were conducted. And estimating equations of single shearing properties were validated.
In this study, shear tests of timbet-to-timber joints including CLT panels with large size self-tapping screws and several material tests were conducted. And estimating equations of single shearing properties were validated. Estimation curves were fitted well with test curves. It is confirmed that estimating equations are valid for timber-to-timber connections of large size self-tapping screws.
