Wood Types

Wood

This chapter mainly states the structure and the physics characteristics of wood. Furthermore it also introduces the corruption and the insect pest caused and the preventive measures to them. This chapter also tells something about artificial plate and its usage.

In the ancient history of Chinese architectural history, the wood used to be combined with materials of construction and those of decoration. The architectures built of them amazes the whole world for the outstandingly perfect usage of wood. Take the world famous Beijing Qi’nian Palace for example, which was made up of completely wood. Nowadays wood is mainly used for interior decoration and ornament.

wood

Wood is used as architectural and decoration material for its several advantages as follows: its specific strength is intense, and it is light-weight and high-strength; it has great elasticity and tenacity that it can bear certain grade of bow and shock wave; its thermal conductivity is low but thermal isolation is good; Being conserved properly, it can be very durable; it is also easy to process, and it can be made into products in various shapes; the wood is beautiful-grained, mild-toned, elegant-styled and well-effected in decoration;the combination of its elasticity, heat isolation and warm tone makes us comfortable; moreover it has high insulating ability without poison. And for sure the wood also has following disadvantages: it is not even in structure, and it is of anisotropy; its quality and usage are affected by the numerous natural disadvantages; it expands with wetness and shrinks with dryness, so it is liable to crack or warp when being used incorrectly; if not properly conserved, it may be corrupted or mildew and rot or even eaten by worms; in addition its fireproof is poor and is liable to burn.

Types Of Wood

In Architecture woods are made of trees, which are may in species.Bu trees are mainly classified in two species.

1. Conifer

2. Broadleaf

1. Conifer: The leaves of these tree are long, slim and needle like.the trunks are straight and tall ligneous tissue is soft liable to process.of superior strength, apparent density is low and strength is also low.These are mainly used in load carrying members like Door or window and also for the Architecture.

2. Broadleaf: Leaves are Broad and shape in sheets, most of which are hard wood.the straight of part of trunks are shorts ad ligneous tissue is hard,not easy to process.the apparent density s high and shrinkage of density is also high.it is easy to crack and warp.It used for minor Interior decoration work like veneer.

The Performance of wood can be derived from the structure of wood and the structure of wood can be classified in to Macro Structure and Micro structure.

* Macro Structure: The wood structures that can be seen by eyes or through magnifying glass are called the macro structure of wood. In order to observe closely, the trunks are cut into three different sections. Transverse section: the section that is vertical against the trunk axis Radial section: the section that passes the trunk axis Tangential section: the section that parallels with the trunk axis and tangent with the annual ring.the wood is made up of bark, xylem and pith,Bark is mainly used for burning except certain species of trees (cork oak, and yellow pineapple tree)whose bark can be used to make heat-proof materials Pith is in the central part of the trunk, whose texture is loose and fragile, and is liable to be corrupted or eaten by insect worms.  So the best part for use is the xylem of trunk. In the xylem, the darker part near the pith is called duramen,while the light part outside is called albumum. The duramen contains little 240 Building materials in civil engineering.water so that it is not liable to reshape, and it has high corrosion resistance.While the alburnum contains more water that it is easy to deform and has worse corrosion resistance than duramen.On the transverse section many centric circles can be seen, which are called annual rings. Of them the part in dark color and lie close are grown in summer,called summenvood. And the converse part is grown in spring, called spring wood. The more summenvood wood has, the better the wood is. The more intense and evener annual rings the wood has, the better quality the wood has.

macro structure

* Micro structure: The wood structures that can be seen through microscope are called micro structure of wood. There are differences between the structures of conifer and broadleaf,Every cell can be classified into two parts: the cell wall and the lumen. The cell wall is composed of fibrils The longitudinal combination is firmer than the transverse combination. So the cell wall is of high strength in length ways, but of low strength in transverse.There are very little spaces among the fibrils composed of cell wall, which enables the material to absorb or leak water.The structure of the cell determines the physical characteristics of wood. For example: the wood with thick cell wall and small lumen is intense and hard, and its bulk specific gravity is high and it is of high strength.

micro structure

Uses Of Wood: During the construction process, the wood should be used rationally according to the species, the grade and the structure. And we should also try to avoid using the big ones for fraction and the good ones for trifles.

The wood used in architecture can be classified into primitive streak, log, sawn timber and crosstie according to its usage and status of processing Primitive streak means the wood without bark, root and treetop. And usually it is not processed into certain length or diameter by certain size.Primitive streak is o ften used as scaffold, architecture material and furniture Log means the wood without bark, root and treetop. And usually it is processed into certain length or diameter according to certain size. Log is often used as frame, purlin or rafter, etc.. Furthermore it can also be used as pile timber, pole, miye timber, etc.. When processed, it can also be made into plywood, ship model and machine model. Sawn timber means timber, which has been processed and sawn. The timber whose width is three (or more than three) times of its thickness is called plate.While the timber whose width is less than three times of its thickness is called square log. Sawn timber is often used in architecture, bridge, furniture, ship, automobile or pocking box.