Glulam knowledge overview

　　The characteristics of glulam

　　1.1 Small materials, good use of inferior materials

　　Because the glulam is formed by short lengths, widths, and thicknesses in longitudinal or transverse gluing, any large cross-section and any length of components can be made according to the customer's requirements, making small materials useful. The mesh wooden structure of the former Beijing Yayuncun Recreation and Leisure Park is a glulam structure made of 4cm thick wood and finger-joined. The beam is 30m long, 2m high, and 4m wide. In 1994, a fused timber arch bridge was built in Ehime Prefecture, Japan. The load was 20 tons. The bridge was 2636 meters long, 8 meters wide and spanned 23 meters.

　　Before gluing, gluing of knots, wormholes, rotted wood rakes, and bending defects such as hollows can be used to produce “non-defective” glulam. Even if there are wood defects in the distribution of the board can also be dispersed, making excellent use of inferior materials.

 

　　1.2 Easy to Dry and Its Versatility

　　Due to the fact that the raw materials of the conjugate material are mostly short materials, the drying is relatively complete, and the water content of the long-sized, large-section member produced is relatively uniform, and the cracking deformation is smaller than that of the large sawn timber product.

　　Before gluing, glulam can be used for pretreatment, anti-fire, pest control, and ant prevention of various special treatment. Compared to large-section sawn timber, the depth and effect of drug treatment are greatly improved, so that glulam products have excellent anti-corrosion properties. Sex, flame retardancy and insect resistance. In addition, glulam has low thermal conductivity, good thermal insulation properties, strong sound absorption, good acoustics, and humidity control capabilities.

 

　　1.3 High strength and high wood utilization

　　In the manufacturing process of glulam wood, the straightness of blank wood fiber can be controlled, and the influence of oblique texture or thrifty and disordered texture on the strength of wood components can be reduced. The combination of laminates can be configured according to the principle of strength and weakness, and the outer layer can be graded. High tree species, lower grade tree species in the inner layer, this configuration has been experimentally proven to be 1.5 times stronger than solid wood. This glulam can not only increase the strength of the product, but also make full use of low grade wood, thus increasing the Wood utilization. The laminated timber can not only be a combination of different tree species, but also can be a combination of appearance graded lumber materials and mechanical performance grade lumber materials. These two combined methods all increase the freedom of production of the glulam. However, for axially loaded components that are mainly subject to axial tensile stress and axial compressive stress, the structural laminates are preferably made of the same grade of sawn timber.

 

　　1.4 Mechanical properties of glulam

　　Although the method of free combination of laminated timber laminates can be used to disperse the defects affecting the strength of sawn timber flexibly, but when the structural laminated timber undergoes bending load, the neutral axis is not fixed like the solid wooden beam but it will follow. The change in the load of Hexa changes and the pressure part even extends below the midline, and the forces in the various parts of the tension part are not completely similar. Therefore, the tensile strength should be particularly considered for the primary evaluation index value of the strength of structural laminated members. The 10% outermost stretch zone on the stretched side of the trussed structural flexural member can be divided into two sections: the outer 5% stretch zone and the inner 5% stretch zone. The thickness of the component is different, and the effect on the strength of the component in the outer 5% drawing zone and the inner 5% drawing zone is affected by the chaos, knot, oblique texture, density, ring width, and the proportion of the pith and pressed wood. The requirements of the factors are also different.

 

　　1.5 The product has more freedom in molding

　　The general glulam is made of small pieces with a thickness of 2~4cm, and can be made into wooden components that can meet various special shape requirements, such as: bow trusses, arches, upper jaw elements, and bent keels, frames, etc. The curved radii of curved glulam are up to 150 times its thickness, which provides great imagination for the design and construction of wooden components. For example, the pagoda-shaped “Nimanoli House” in Shangjing District of Kyoto, Japan, is all trussed. The underground building has 4 floors, 72 floors above ground, 339m in height, and a total area of ​​5027m. The appearance is simple and elegant, which is difficult to achieve for other wood products.

 

　　1.6 Continuous production

　　In countries such as Europe, North America and Japan, Glulam has achieved industrial continuous production, and has greatly increased the production speed of various special-shaped wooden components and the assembly speed of buildings.

 

　　1.7 Disadvantages

　　The production of Glulam requires dedicated production equipment, good technology and quality monitoring systems, and product inspection personnel or institutions. Compared to solid wood products, Glulam products consume more energy due to sawing, planing, and bonding. , so its cost is relatively high.