The wooden frame of the ancient building is composed of various wooden components combined horizontally and vertically to form a skeleton, and the mechanical characteristics of the wood are used to connect through the node structure, so that the ancient building has the characteristics of "the wall collapses and the house does not collapse". The combination methods between components mainly include mortise and tenon joint, adhesive bonding, nail bonding, binding method, metal connector connection method, etc., and bolt connection method in modern times.
First, the combination of mortise and tenon joints
Mortise and tenon is a general term for tenon and tenon eye, in the combination of wooden components of ancient buildings, craftsmen make the end of a wooden component into a prominent shape, called tenon or tenon, and at the same time make a notch that fits with the tenon at the end of another wooden component called Mao or mortise. The application of mortise and tenon structure in ancient Chinese architecture is very early, in the Hemudu site of Yuyao, Zhejiang Province 5000~7000 years ago, various mortise and tenon joints including column head tenon, column foot tenon, beam head tenon and tongue and groove have been found, see Figure 4-107 for details. In the Song Dynasty's "Constructing the French Style", several kinds of duets, drums, mantis heads, and hooks are recorded, as shown in Figure 4-108. For a long time, with the practice and exploration of engineering and technical personnel, many unique mortise and tenon processes have been created.
Figure 4-107 The mortise and tenon structure at the Hemudu site in Yuyao, Zhejiang
Figure 4-108 An example of mortise and tenon in Song's "Constructing the French Style".
There are many kinds of mortise and tenon joints of wood frame, different shapes, and the formation of these types and shapes is not only directly related to the function of mortise and tenon joints, but also has a direct relationship with the position of wood members, the combination angle between components, the combination mode, and the installation sequence and installation method of wood components. According to the position and function of the Qing mortise and tenon joint, it is divided into the following categories.
(1) Mortise and tenon joints of column components
In ancient timbers, the vertical members are mainly various columns. Ancient pillars can be divided into two categories: floor-to-ceiling columns and non-floor-to-ceiling columns. The landing columns include eaves columns, gold columns, middle columns, mountain columns, corner columns, etc., and the columns that do not fall to the ground include child columns, melon columns, Lei Gong columns, weeping lotus columns, etc., these pillars all need to be fixed with mortise and tenon joints.
1. Pin tenon
That is, the tenon used to fix the column base, its function is to prevent the displacement of the column base. According to the "Quality Inspection and Evaluation Standards for Ancient Building Construction Projects" (CJJ 39-91), the length of the pin tenon should not be less than 1/4 of the end column diameter, should not be greater than 3/10 of the end column diameter, and the diameter of the tenon (or cross-section side length) is the same as the length. The pin tenon is used for all kinds of landing columns and children's column feet, when used for landing columns, the sea eye should be chiseled out at the corresponding column capstone position, and when used for children's columns, a flat bucket plate (also known as pier buckets) is placed at the foot position of children's columns, and there is a socket on the bucket. See Figure 4-109 (a), (b) and (d) for details.
2. Set top tenon
The top tenon is a special pin tenon, which is larger than the general pin tenon in length and diameter, and penetrates the capstone and falls directly on the bottom stepping stone. Its length is generally 1/5~1/3 of the exposed part of the column, and the tenon diameter is 1/2~4/5 of the column diameter, which needs to be determined as appropriate. The roof tenon is mostly used in promenades, pavilions, hanging flower doors, archways, etc. The function is to strengthen the stability of the building, but because the roof tenon is buried deep underground, it is easy to decay, so the buried underground part should be treated with anti-corrosion. See Figure 4-109(c) for details.
Figure 4-109 Pipe tenon, steamed bread tenon, top tenon, and child column foot tenon
3. Half-tenon at the foot of the melon column
The melon column foot tenon is used for the connection between the column foot and each beam frame of various melon columns. The tenon of the guapillar foot is commonly a double tenon, the tenon thickness is about 1/6 of the width of the guazhu (generally about 8 minutes, about 25mm), and the tenon length is 2~2.5 inches (60~80mm). When the melon column is high, in order to enhance the stability of the column, the corner back is often used. At this time, the root of the melon column needs to be made of a cover tenon on the basis of the half tenon, so that it can be installed together with the corner back. See Figure 4-110 for details of the half-tenon at the foot of the melon column.
Figure 4-110 Semi-tenon structure of melon pillar base
4. Steamed bread tenon
It is used for the connection part between the column head (including the melon column) and each beam, which corresponds to the sea eye at the bottom of the beam head, and the size of the steamed bread tenon is the same as that of the pin tenon, see Figure 4-109 (b) for details.
5. Stigma purlins
It is used for the overlapping part of the stigma head of the middle column, mountain column and ridge melon column and purlin. The form of the stigma purlin is similar to that of the beam head purlin, and the size is 1/4 purlin diameter from the purlin lower skin to set the purlin height, and according to this, press the 45 ° angle on both sides, and do the "nose" tenon in the center of the purlin bottom skin, and the height and width of the "nose" tenon are 1/5 purlin diameter.
(2) The mortise and tenon of beam (柁) components
1. Large in and small out tenon
It is used for the connection between the head beam, the peach tip beam, the gold corner beam, the corner beam and the column. The tenon is thick, the cylindrical diameter is usually 1/4 column diameter or 1/3 beam thickness, and the square column is usually 1/4~3/10 column diameter. The height of the "big in" part of the tenon is according to the full height of the beam, and it is long to the middle of the column; the height of the "small out" part is 1/2 of the height of the beam, and the length is according to the diameter of the column itself (the head is half the column diameter). The structure of large inlet and small tenon is detailed in Figure 4-111.
Figure 4-111 Structure of large inlet and small outlet
2. Half-oak
It is used for the connection between the head beam, the peach tip beam, the gold corner beam, the corner beam and the column. The tenon is thick, the cylindrical diameter is usually 1/4 of the column diameter or 1/3 of the beam thickness, the square column is usually 1/4~3/10 of the column diameter, the tenon height is according to the full height of the beam, and the tenon is long to the column.
3. Semi-tenon pressure palm tenon
When the beam frame used for the mountain column or the middle column intersects with the column, the tenon height is generally divided into 2 points, and the column diameter is divided into three parts, so that the half tenon at one end is 1/3 of the column diameter and 2/3 of the column diameter is extended below, and the other end of the half tenon is 2/3 of the column diameter and 1/3 of the column diameter is extended below. And in accordance with the provisions of the "Quality Inspection and Evaluation Standards for Ancient Building Construction Projects" (Northern Region) (CJJ 39-91), the auxiliary tension structure applied at the lower part of the finch or substitute wood must be a sparrow substitute or substitute wood with a pulling effect. The structure of the semi-tenoned palm tenon is shown in Figure 4-112.
Figure 4-112 Half-tenon pressed palm tenon structure
4. Purlin and nose tenon
It is used at the intersection of various types of beam frames and purlins, corner beams and purlins. In accordance with the provisions of the "Quality Inspection and Evaluation Standards for Ancient Building Construction Projects" (Northern Region) (CJJ 39-91), the depth of the beam head purlin shall not be greater than 1/2 purlin diameter, shall not be less than 1/3 purlin diameter, and there must be a nose tenon between the beam head purlins, and the tenon width at the general position is 1/2 of the beam head width. The beam head of the purlin is made of a small nose tenon, and the height and width of the tenon should not be less than 1/6 of the purlin diameter, and should not be greater than 1/5 of the purlin diameter.
When the purlin truss intersects with the angle beam, also make the purlin (truss) 椀 according to the need, the nose (also known as the gate) can be left at the mouth of the purlin, or it can not be left, when the purlin truss intersects with the corner beam, the angle cloud, etc., the beam head does the overlapping tree, does not leave the nose. The structure of the purlin and nose tenon is shown in Figure 4-113.
Figure 4-113 Purlin and nose tenon structure
5. Step tenon
It is mostly used at the intersection of the lying beam, the trowel beam and the purlin truss, and the intersection of the long and short lying beams.
The intersection of the lying beam, the trowel beam and the purlin truss must be stepped tenon. The stepped tenon is generally made into three layers, each layer is deep into the purlin not more than 1/4 of the purlin diameter, the longest tenon length does not exceed the center line of the purlin, and about 1/4 beam width is made on both sides of the stepped tenon. In addition, the outer end of the beam head must be pressed through the purlin centerline, and the length of the centerline shall not be less than 15% of the purlin diameter.
When the short lying beam is placed on the long lying beam, the erection length is not less than 1/2 of the width of the lying beam, and the intersection is slightly the same as the above, and it can not be covered. The stepped tenon structure is shown in Figure 4-114.
Figure 4-114 Stepped tenon structure
(3) The mortise and tenon of fang components
1. Dovetail
Also known as semi-silver ingot tenon, it is the tenon used in the intersection of horizontal members such as eaves, foreheads, beams, gold fangs, and ridges. The shape of the dovetail tenon is narrow at the root, wide at the end, and has a large head, which is called "putting", and the dovetail tenon is large at the top and small at the bottom, which is called "closing the tongue". The purpose of the first is to make the tenon and tenon knot strong, and the purpose of retracting is to tighten and tighten the falling installation when it is installed.
When the fang component is made, the length of the dovetail tenon should not be less than 1/4 of the corresponding column diameter, and should not be greater than 3/10 of the corresponding column diameter, and the maximum cross-section width of the tenon is required to be the same length. The "cha" and "slip" of the dovetail tenon should be scored according to 1/10 of the cross-sectional width.
Used for the dovetail tenon on the forehead and eaves, there are two methods with sleeve shoulders and without sleeve shoulders, and the sleeve shoulders are used to solve the small root section of the dovetail tenon, poor shear resistance and the use of a remedy, the length of the sleeve shoulders is generally 1/8 column diameter, and the width is equal to the big head of the tenon.
The dovetail structure is detailed in Figure 4-115.
Figure 4-115 Dovetail structure
2. Hoop head tenon
The hoop head tenon is a special mortise and tenon structure used for the junction of the forehead (eaves) fang and the end post or corner post. The specific method of hoop head tenon is to add a column diameter (large) or 1.25 times the column diameter (small) from the center line of the column to the forehead, make tenon and groove at the intersection of the fang and the column head, and make the hoop head other than the part of the column skin. There are two forms of hoop head, overlord fist and three-way head, which are used in large and small buildings respectively.
There are two cases of hoop head fangs on one side and two sides. When used on one side, only the stigma head needs to be grooved in one direction along the surface width, and when used on both sides, the stigma head needs to be cross-grooved. When the double-sided hoop head fang is used, the two-way forehead fang intersects at the corner stigma buckle, and the intersecting part should be made equal mouth and cover, and the production and installation are carried out in accordance with the law of the mountain surface pressing the eaves surface. The tenon height of the hoop head tenon is 8/10 square height, and the tenon width should not be less than 1/4 of the column diameter, and should not be greater than 3/10 of the column diameter.
The structure of the hoop head is shown in Figure 4-116.
Figure 4-116 Hoop head tenon structure
3. Large in and small out tenon
The large in and small out tenon is used to intersperse the connection between the fang and the column. Tenon size: tenon thickness, the cylinder is usually 1/4 column diameter or 1/3 thickness, the square column is usually 1/4~3/10 column diameter;
4. Half-oak
The half-tenon is used for the parts connected with the pillar, such as the rafters, the ridge, the intersection, and the chessboard. The tenon is thick, the cylindrical diameter is usually 1/4 of the column diameter or 1/3 of the thickness of the fang, the square column is usually 1/4~3/10 of the column diameter, the tenon height is according to the full height of the fang, and the tenon is long to the column.
5. Cross-carved half-oak
The cross-engraved semi-tenon is a kind of cross-tenon. It is often used for the intersection of the cross of the flat fang (general fang), the depth of the notch is 1/2 of the thickness of the fang, and the width of the notch is considered on both sides according to the width of the component itself 1/10 to make a "cover" (sleeve tenon), and the remaining 8/10 fang width is the width (length) of the notch. The cross-engraved semi-tenon structure is detailed in Figure 4-117(a).
Figure 4-117 Overlapping tenon structure
(4) The mortise and tenon of purlin (truss) components
1. Dovetail
It is used for the connection between purlins and purlins. The width of the upper head of the dovetail tenon head is 3/10 of the diameter of the purlin, and the root of the lower end is 1/10 of the width of the head to both sides. The length of the tenon is the same as the width of the head at the end of the tenon, and the height of the tenon is made according to the different parts of the beam head carved half tenon or ridge purlin (truss) through tenon.
2. Cross clamp waist tenon
The cross card waist tenon is a kind of lap tenon, which is often used for lap purlins. The specific method is to divide the purlin truss into four equal parts along the wide and narrow surface, divide it into two equal parts along the high and low planes, engrave one on each side according to the required angle, and then engrave the upper or lower half of each other, and then buckle and intersect.
Cross card waist tenon is often used in quadrilateral, hexagonal or octagonal buildings, when used in quadrilateral buildings, it should be carved and overlapped in accordance with the principle of mountain eaves surface, if used in hexagonal or octagonal buildings, there is no problem of mountain eaves surface, on the same member, the direction of the joint should be consistent, that is, both ends of a component are made of equal tongue tenon, and both ends of an adjacent component are made cover tenon. It is not possible to make both equal and cover on one component.
The structure of the cross clamp waist tenon is shown in Figure 4-117(b).
(5) Large wooden components are connected by hidden pins
Unlike mortise and tenon joints, concealed pins can be used independently and are set to prevent the displacement of wooden members. It is often used in large foreheads and flat fangs, old angle beams and corner beams, truss purlins and backing plates, and between the various layers of bucket members. There are two common hidden pin connections: load pin and hinge pin.
1. Loading
The loading pin is to drill the hole at the corresponding position of the overlapping surface of the two layers of components, and then load the wooden pin into the pin eye of the lower layer member. When installing, the pin eye of the upper member corresponds to the pin tenon that has been loaded. Pin tenons are used for large wooden members, in order to prevent the misalignment of the upper and lower members. The pins in the large wooden components are rectangular, and their sizes are mostly 1.8 inches× 0.8 inches× 2.5 inches, and the pins in the bucket are mostly 1.2 inches× 0.4 inches× 2 inches. The pin structure is shown in Figure 4-118.
Figure 4-118 Pin structure
2. Hinge pins
The pin method does not penetrate the component, while the pin rule penetrates two or even multiple layers of the member. The common components that use hinge pins in ancient buildings are: the locking of the components of each layer at the back and end of the gold bucket, the hairpin on the sill in the gate of the ancient building, the ridge pile at the ridge wood of the large roof, the tenon under the column of the high column of the archway, and the head part of the rafter using the chaotic head. The hinge pin structure is shown in Figure 4-119.
Figure 4-119 Hinge pin structure
(6) The mortise and tenon joint structure of the plate joint
The production of ancient building wood and some decoration components often requires the use of wider wooden boards, such as Bo seam board, mountain flower board, hanging board, wooden floor board, door leaf board, etc. This requires plate seam splicing, and the common plate seam splicing mortise and tenon joints are as follows.
1. Silver ingot tenon (buckle)
It is often used for sewing boards and couch boards. It is shaped like a silver ingot, with large ends and a thin middle waist. It is inlaid between the seams of the two panels, which can effectively prevent the panel from loosening and cracking due to the age of glue. The spacing of the silver ingot tenon should not be greater than 10 times the thickness of the plate itself or 1.2 times the width of the plate itself.
2. Judgment (企口缝)
It is to cut off half of the small surface of the wooden board according to the thickness, the width of the cut is similar to the thickness, and the two sides of the wooden board are staggered and cut, and then lap to use, this practice is often used in the Lizha Mountain Flower Board.
3. Dragon and phoenix tenon
The small side of the board is cut out of grooves in the center, and the other board surface combined with it is cut into a convex tenon in the center, and the combination of the two boards is just convex and concave. Dragon and phoenix tenon is the most commonly used splicing method for ancient building boards, and is often used for the splicing of mountain flower boards, drip bead boards, hanging boards and wooden floor slabs.
4. Wear straps
The reverse side of the glued plate is removed from the dovetail groove, the depth of the groove is about 1/3 of the thickness of the plate, and then the dovetail threading belt is driven into the groove, which can lock the plates, do not crack, and have the effect of preventing the concave and convex deformation of the board surface. Threading is often used for plate door leaves, vertical gate dripping bead boards, hanging drop plates, etc.
There are three ways to wear the belt: one is the flat belt, that is, the belt is flush with the surface of the board; the other is the open belt, that is, the belt is combined with the trowel, the practice is the same as the flat belt, but the belt should highlight the board surface;
5. Pressure the palm
It is mostly used for splicing between the roof lookout plates, and the upper and lower plates are combined by an inclined section. The intersection of rafters and rafters is also often used to press the palm.
See Figure 4-120 for details of the common plate seam splicing mortise and tenon joints.
Figure 4-120 Common mortise and tenon joint structure of plate seam splicing
Second, adhesive bonding
1. Cementing material
In ancient times, most of the gum was animal glue. In the Shang Dynasty and even earlier, glue was used for the bonding of wooden joints. Glue making materials are generally taken from animals, including leather glue, bone glue, fish glue, gelatin, etc., leather glue and bone glue are the most commonly used, commonly known as "water glue". The second is fish gelatin. Animal glue has low cost, easy preparation and use, good dry strength, and low melting point, which is 18~22 °C. This glue melts when heated, solidifies when cooled, and the gluing process is very short, and the elasticity of the adhesive layer is very good, and it is not easy to dull the tool. However, most of them are not resistant to water (the adhesive layer expands and loses its elasticity when exposed to water), and is not resistant to bacterial and insect corrosion.
The process of wood gluing has both chemical and physical reactions. The strength and size of the glue are related to the quality of the glue, the properties of the wood, the moisture content, and the thickness of the glue joint. Wood with soft texture and loose fiber, such as red and white pine, fir pine, etc., and wood with hard texture such as oak, jujube, quercus glauca, sandalwood, etc., have better bonding performance; when the moisture content of wood is 8%~10%, the bonding strength is the highest; the smoother and smoother the planing surface, the greater the bonding strength; the thicker the coated adhesive layer, the lower the cementation strength, and the optimal thickness value is 0.05~0.2mm.
2. Gluing process
(1) Wood surface treatment First of all, the moisture content of the wood should be controlled at 8%~12%; the surface of the wood should be smooth and clean, the old and unclean surface should be planed or sandpapered; the sawdust on the surface of the wood should be wiped with a cloth or brush. If necessary, the surface of the wood can be degreased to increase the adhesion.
(2) The temperature of boiling glue should be controlled at 60~80 °C, the water temperature is too low, which will prolong the time of the sol, and the water temperature is too high, which will reduce the viscosity of the glue. It is also necessary to correctly grasp the thickness of the glue. The thickness of the glue depends on the cementing object and the ambient temperature. In the case of glulam strips or mortis, the glue should be thicker, and in the case of panels or laminates, the glue should be thinner. The glue should be thinner in winter and thicker in summer.
(3) Cooling and aging When gluing the wood, the adjusted glue is evenly applied to the two adhesive surfaces, and it is allowed to stand in the air for a period of time, which is called "cooling". It is then attached and then stored for a period of time, which is called "aging". Cooling and aging can make the glue easy to diffuse, penetrate and volatilize the solvent, and improve the adhesion.
(4) Bonding and curing In the process of bonding and curing, external force can be appropriately applied to ensure the sealing of the bonding surface, avoid gaps, and promote the penetration of glue. The pressure is applied after aging and is not relieved until the glue is completely or largely cured.
3. Nailing
The use of nails in continental woodwork is relatively late. During the Spring and Autumn Period and the Warring States Period, the development of iron smelting technology in the mainland promoted the use of metal nails in woodwork. According to relevant research, iron nails were first used in boats, and at the latest in the late Warring States period, large building timber began to use iron nails to combine, and became one of the necessary means of combining ancient building wood.
In addition to metal nails, ancient buildings also have the use of wooden nails and bamboo nails, in fact, the use of wooden pins, in fact, is actually "big wooden nails". This type of nail is usually chiseled or drilled to make a small and deep hole, and then hammered into the nail material. In ancient times, metal nails were rarely used in the woodworking industry, and even the level of skill was often measured by the presence or absence of metal nails, and those who used nails were often treated with contempt and considered "laymen". In fact, in the construction of ancient buildings, bamboo and wooden nails are mostly used in the combination of small wooden components, and iron nails are used in the combination of large wooden components, and hidden pins are used in the combination of large wooden components, and there are examples of nail combination in places that are out of sight, such as ancient rafters and lookout boards.