Designing,Manufacturing And Property Evaluation Of Hemlock CLT

CLT is a new type of woodwork developed by Germany and Austria. CLT is usually produced and processed accurately in the manner of prefabrication at factory according to the requirement of structure design. This mode of production enhances the efficiency of site construction, reduces construction cost and reduces construction site dust and noise pollution. Among medium- and high-rise buildings,high-rise building adopts prefabrication, simple and rapid installation method, which shortens construction time of buildings. Therefore, it is one of main advantages of CLT applied to buildings. In addition, CLT buildings have such advantages as high-strength and light quality, intact structure, good insulation and durability.Consequently, CLT is deemed as a good choice to increase added value of woodwork.In order to technically analyze the feasibility of Canadian hemlock species for CLT manufacturing and analyze and evaluate the market prospects of CLT in Canada and China, it is necessary to find a new breakthrough for the application and popularization of hemlock materials in CLT wood structure building point.The paper firstly applies lateral oscillation method to test modulus of elasticity parallel to grain, tangential elastic module and tangential shear module of Canadian hemlock dimension lumber, makes grade stress of sawn timber in accordance with modulus of elasticity parallel to grain of sawn timber so as to know the property of Canadian hemlock. Based on this, the paper determines the feasibility of hemlock in the application of hemlock to CLT manufacturing. In addition, the paper predicts CLT property by using calculation model so as to confirm CLT assembly scheme. It formulates and designs the processing and manufacturing flow and technological parameter of production of hemlock CLT according to the current production line,processes and manufactures hemlock into CLT with full size according to the conventional production technology of CLT, conducts systematic test and evaluation of anti-bending elasticity modulus, bending strength, shear strength, shear strength of glue line and durability of glue line for CLT and analyzes the feasibility of CLT used for CLT manufacturing. In addition, the paper determines the accuracy and reliability of computed result in theory through contrast analysis between predicted computed result and measured static result. The research result indicates that:(1)The average mechanical properties such as modulus of elasticity parallel to grain, tangential elastic module and tangential shear module of hemlock dimension lumber used in this paper reaches the property required by CLT manufacturing.Moreover, the test result of modulus of elasticity parallel to grain conforms to Weibull distribution law. After making stress grade according to the modulus of elasticity parallel to grain, 35% of sawn timber of hemlock reaches 1.5E stress grade,and 34.8% of sawn timber of hemlock reaches 2.0 E stress grade.(2)After designing CLT unit structure, the theoretical predicted value of engineering properties like effective bending rigidity, bending strength, maximum deflection and inherent frequency of CLT finished plate can reach the requirement of related building design code and conform to the requirement of practical engineering application.(3)The test results of elasticity modulus in main strength direction, bending strength, shear strength of interface layer, cementation strength and durability of hemlock CLT reach the requirement of Canadian CLT standard grade.(4)Hemlock dimension lumber and various mechanical properties of hemlock CLT can reach the requirement of Canadian grade standard ANSI APA PRG320-201.Therefore, Western Canadian hemlock can be used to process and manufacture CLT for engineering use.(5)The theoretical predicted value of elasticity modulus in the main strength direction of CLT has high pertinence with the measured value and the result error is within 10%. Therefore, we can draw the conclusion that the method of utilizing dynamic modulus of elasticity of sawn timber composed of CLT unit to predict the property of CLT finished plate is relatively accurate and feasible, which can be used for structure design and property prediction prior to CLT processing and manufacturing.(6)The decay and knot defects of timber have obvious impact on bending strength, shear strength of interface layer, cementation strength and weather resistance of glue line. During CLT production and manufacturing, please pay attention to the appearance grade of base material and avoid using timber with obvious defects as the base material.Therefore, this study is of great significance to find the new application direction of Canadian hemlock and improve the added value of the products of western China hemlock. At the same time, it has high theoretical guidance and significance to promote the development, promotion and application of domestic CLT wood building Value.