Wooden materials and products

The materials and products which are obtained by tooling of tree trunk (timber and saw-timber, millwork and details), physical and chemical processing of fibred wood-pulp without the special introduction of binder substances (cane fiber boards, plastic lingo-carbohydrates and piezo-thermoplastics) or with addition of binders (glued wood, particle boards, sawdust concrete and other) are applied for the construction purposes.

Timbers. Round timbers are the segments of tree trunks with the chopped off knots and pollinated butt ends. Segments of trunks with diameter more than 12 cm consider chumps, from 8 to 11 cm - rickers, from 3 to 7 cm - polewood.

Round timbers are divided into sorts depending on the amount and type of defects. Rot is permitted in none of sorts. Logs which are utilized for making of bearing structures must have humidity not more than 25%.

Round commercial timber is stored at outside court in stacks in not more than 2 m high, which provides the normal natural drying. The butt ends are covered with the moisture protecting mixtures and lime solution to prevent the logs from cracking.

The saw-timbers (Fig. 19.3) are obtained by the longitudinal sawing of logs. They are divided into slab boards, quarters, bars, boards and half logs.

Plates are obtained by tree sawing for the axis of trunk on two halves, quarters - in mutually perpendicular directions. Incomplete plates are the wastes at sawing of logs called half logs. Bars have a thickness and width more than 100 mm, scantlings - thickness to 100 mm and width no more than double thickness, boards - thickness to 100 mm, width - more than double thickness.

According to the thickness, the saw-timbers are divided into fine-bored (planks) to 32 mm and thick, more than 32 mm; according to the character of treatment – on edged, sawed from all four sides and unedged, sawed only from two sides.

Length of coniferous saw-timbers is in the range of 1-6.5 m, hardwood in the range of 0.5-6.5 m.

The sort of saw-timber is determined by the presence of wood defects, and also sawing exactness, cleanness of treatment and warping degree. The saw-timber with humidity less than 25% is saved in the closed premises or under a cover, and more than 25% - in stacks.

Boards and bars, cut on the set sizes with assumptions on tooling and shrinkage, which is used for making of details, are called work materials. According to the kind of work materials treatment there are sawn, glued, calibrated. There are utilized also millwork materials, which have a special cut form.

Along with the roundwood and sawn, the sliced, shelled, shredded timber is applied in construction. The veneer, plaster clapboard, roof slab, bundling chipping and other setting are made by an adzing. Decorative veneers are thin layers (0.6-1mm) of wood which differ with beautiful texture and color. It is made from wood of oak, ashwood, beech, African mahogany, larch and other. A texture paper and various decorative tapes are widely utilized in the place of natural planed veneer.

The peeled veneers which are obtained from the steamed out blocks in the type of continuous ribbon with a next scission on the sheets of necessary sizes is applied for making of plywood and laminates, and also facing elements from wood.

Parquet - is a material for arranging of floors in housings and public buildings, which made as block parquet, mosaic, as parquet boards. Block parquet consists of slats which are made from wood of oak, beech, ashwood, maple, pine-tree and other. Fabricated wood block flooring and shields consist of slats which are glued by a certain picture on basis. There are slots and cogs on the edges and butt ends of parquet board for connection between themselves. Veneer squares or the veneered facing dalle can be also glued in place of slats on parquet shields. Facial side of parquet board and shields usually has the transparent lacquered coverage. The artistic parquet blocks are applied for the floors of unique buildings. The mosaic parquet is made as carpets, which consist of separate slats, glued by a facial surface on a paper or other elastic material.

The basic types of elements and details of wood are wood moldings, millwork, window and door blocks, partitions and panels.

Wood moldings are boards and scanting for floors, baseboards, banisters, cases, boarding and other elements – are got by milling on machine-tools. They are characterized by a certain form of transverse section; for example, boards and scanting for floors have a slot on one edge, and cog on another.

Shields are made for the installation of partitions and ceilings, and also casing for concrete and reinforced-concrete structures,they consist of wooden framework to which the side plates are asigned to. The battenboards are got at gluing on the shields from both sides in one or two layers of veneer; they are used at wall, floor, shield furniture installation. The window and door blocks are also got from millwork for construction.

The factory-made houses are produced from bars, framed wooden elements and panels and also and other prefabricated articles (Fig. 19.4). In the framed wooden houses the wooden framework is filled with the fibreboards and woodwool slabs. The water-resistant board materials are applied for revetment of external walls. In the factory-made houses for boarding are used edged boards, space between which is filled with heat-insulating materials.

Glued wood. The glued wood belongs to the most effective construction materials. It can be stratified - from veneer (plywood, laminated-wood plastic), massive - from the lump raw waste lumber and woodworking (panels, blocks, squared beams, boards), combined (battenboard).

Construction plywood is the sheet material, obtained by gluing of three and more veneer slices with the mutually perpendicular placing of fibers. After the drying the veneer packages are glued together usually by the hot compaction on the hydraulic press.

There is distinguished plywood of raised waterproofness, glued on phenol-formaldehyde resin, medium waterproofness, - on the carbamide and albuminic casein glues and limited waterproofness - on protein glues.

The veneer sheets of plywood can have a thickness from 1.5 to 18 mm.

Along with ordinary one, the decorative plywood is made, faced with the film coating. The bakelized plywood which is made from a birch veneer has high structural strength, impregnated with phenol-formaldehyde resins, at the protracted conditioning. The plywood is also reinforced by the expanded lathes or encase with the metal skim to increase the strength, hardness and inflexibility.

Plywood is widely used for revetment of walls, production of veneered doors, glue plywood sheets for external and internal walls and ceilings, panels, for built-in furniture and others like that.

The glued products from the lump timber waste classify at the type of glue which is used and character of treatment and characteristics. The strength of wood adhesion depends on porosity, correlation of summerwood and latewood in annual layers, its humidity, chemical composition, fiber angle. It is set that the strength of gluing is in linear relation to porosity, it grows also in measures of cellulose content increasing.

Advantages of the glued wood are low average density, waterproofness, possibility of products manufacturing from of small size material of irregular shape or large structural elements; influence of wood anisotropy is weak in the glued structures, they are characterized with the rot-resistance and by a low capacity for ignition, are not liable to the shrinkage and warping. Glued timber structures by the terms and labor expenditures of construction and also resistance to the action of corrosive air environment often successfully compete with steel and reinforced-concrete structures. Their application is effective at the erection of agricultural enterprises, exhibition and commercial halls, sporting complexes, buildings and constructions of prefabricated type.

As well as the reinforced concrete, the glued timber can be produced preliminary tensed, reinforced by the steel rods. In the reinforced structures as solid-webbed or hollow beams, the bearing ability almost in 2 times is higher, than in all-wood.

The nomenclature of products from the glued wood is wide. So, from the deal-ends, the panels are glued which have the cleavage strength along fibers in the glued juncture not less than 6 MPa. The static bending strength of toothed finger joint is not less than 35% of flaw-free wood strength. Such panels are applied for the installation of partitions, boarding of houses, floors boarding.

The glued shields used, mainly for floor boarding is manufactured from the wastes of lumber. For their making lump wastes of lumber are cut on the scanting, which are dried to the humidity at 10-12%, and then are glued together at pressing. The blocks are addiced from two sides on the thicknessing machine, cut on a perimeter to the set sizes with simultaneous making on the lateral edges of slot and cog.

The economy of industrial wood to average 20 % at using of the glued elements in building, and the cost of structures diminishes in 3-4 times comparatively with the cost of structures from whole wood.

Structures from the glued wood allow decreasing the mass of buildings in 2.5-3 times, to reduce the efforts on 25-30%, and terms of construction in 1.5-2 times.

Beams, frames, arches, arched girders, and spatial structures belong to the basic types of the glued industrial timber.

Date: 2015-12-18; view: 1289