Glulam is the use of plates or small square wood according to the direction of wood fiber parallel, in the thickness, width and length of the direction of the glued wood products. The raw materials of laminated timber are mostly thinning timber and small diameter timber. Glulam is one of the effective means to save wood and improve the utilization rate of wood.
Characteristics of Glulam
1.1 small materials are of great use, inferior materials are of great use
Because the laminated material is made of short and small materials in the length, width and thickness directions of vertical or horizontal splicing and gluing, it can be made into components with any large cross section and any length according to customer requirements, making small materials useful. The net-like wood structure building of the former Beijing Asian Games Village Recreation and Leisure Water Park is a laminated wood component made of 4cm thick wood boards glued by fingers. The beams are 30m long, 2m high and 4m wide. In 1994, a glulam arch bridge was built in Ehime Prefecture, Japan, with a load of 20t, a length of 2636m, a width of 8m and a span of 23m.
Before gluing, the "defect-free" glulam can be produced by removing wood defects such as nodes, insect eyes, decay, etc. and growth defects such as bending and hollow. Even if there are wood defects in the board, it can be dispersed, making the inferior wood superior.
1.2 easy to dry and its versatility
Because the raw materials of laminated timber are mostly short and small materials, the drying is relatively sufficient, and the moisture content of each part of the long-sized and large-section components is relatively uniform. Compared with large sawn timber products, the cracking and deformation are small.
Before gluing, the laminated timber can be pre-treated with various special treatments such as anti-corrosion, fire prevention, insect prevention, and ant prevention. Compared with the large cross-section sawn timber, the depth and effect of drug treatment are greatly improved, so that the laminated timber products have excellent corrosion resistance, flame retardancy and insect resistance. In addition, the laminated material has low thermal conductivity, good thermal insulation performance, strong sound absorption, good sound effect, and has various functions such as humidity control ability.
1.3 high strength, high utilization rate of wood
In the process of making glulam, the straightness of embryo wood fiber can be controlled, and the influence of oblique texture or disordered texture of knots on the strength of wood components can be reduced. The combination of laminates can be based on the principle of strength configuration. The outer layer uses tree species with higher grade and the inner layer uses tree species with lower grade. The experiment proves that its strength performance is 1.5 times that of solid wood. This glulam can not only improve the strength of products, it can also make full use of low-grade wood, thereby improving the utilization rate of wood. Glulam can not only be a combination of different tree species, but also a combination of sawn timber with equal appearance and mechanical properties, both of which increase the freedom of production of glulam. However, for axially loaded members subject primarily to axial tensile and axial compressive stresses, the laminates of the member are preferably of the same grade of sawn timber.
Characteristics of Mechanical Properties of 1.4 Glulam
Although the free combination of laminated timber laminates can disperse the defects affecting the strength of sawn timber at will, when structural laminated timber is subjected to bending load, its neutral axis is different from that of solid wood beams, but will change with the increase of load. The compressed part even extends below the midline, and the stress of each section of the tensile part is not completely similar. Therefore, special consideration should be given to the tensile strength, the primary evaluation index value for the strength of structural laminated components. The outermost 10% stretch zone on the stretch side of the laminated material bending member for mechanism can be divided into two parts: the outer 5% stretch zone and the inner 5% stretch zone. The thickness of the component is different, and the requirements for the factors that affect the strength of the component, such as random lines, nodes, oblique texture, density, annual ring width and the proportion of medullary core and compressed wood, are also different in the external 5% tensile zone and the internal 5% tensile zone.
1.5 product modeling greater freedom
General laminated material is made of small materials with a thickness of 2~4cm, which can be made into wood components that can meet various special shape requirements, such as: bow-xuan frame, arch frame, upper-xuan component, curved keel, frame, etc. The bending radius of bending laminated material can reach 150 times of its thickness, which provides a lot of imagination space for the design and construction of wood component buildings. For example, the pagoda-shaped "Riman Lilou" in Shangjing District of Kyoto, Japan is all laminated material structure. Its underground building has 4 floors and above-ground building has 72 floors, reaching 339m, with a total area of 5027m m. Its appearance is simple and elegant, which is difficult for other wood structures.
1.6 can be continuous production
In Europe, North America and Japan and other countries, laminated timber has achieved industrial continuous production, and greatly improved the production speed of various special-shaped wood components and the assembly speed of buildings.
1.7 Disadvantages
The production of integrated timber requires special production equipment, good technology and quality control systems and product inspection personnel or institutions, and compared to solid wood products, integrated timber products because of sawing, planing, gluing and other energy consumption, so its cost is relatively high.
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