Understanding of Wood Structure Architecture in China

The ancient wooden structure in China is the main structural type and important feature of ancient buildings in China. Since ancient times, when there are two primitive life forms, namely "nest" and "hole", the primitive prototype of wood structure has emerged. The description of "building wood as a nest" in ancient times in the literature is undoubtedly a description of the embryonic state of wood structure. As far as cave dwelling is concerned, the hole of bag-shaped vertical cave dwelling must also adopt supporting structure and covering structure composed of branches and branches of vegetation. As a result, it has evolved into various buildings built on the ground, forming a unique wood structure system in China.

Archaeological excavations have confirmed that as early as the Neolithic matriarchal clan society, a large number of clan settlement buildings have been discovered in the vast areas of the Yellow River Basin and the Yangtze River Basin. From the banpo village site in Xi 'an, Shaanxi Province and Hemudu site in Yuyao County, Zhejiang Province excavated in recent years, it can be seen that the wooden structures at that time had a considerable scale and level. The wooden components found in Hemudu site prove that the ancestors of China mastered the perfect tenon-mortise connection technology a long time ago, which also shows that the wooden structure has experienced a long process of use and development before this.

Ancient wooden structures in China can be roughly divided into three types: lifting beam type, cross bucket type and well dry type. Among them, the beam structure is widely used, followed by the bucket structure, and the well dry structure is mostly used in wood producing areas.

The beam-lifting wood structure is mainly composed of front and rear columns along the depth direction of the building, and beams are erected at the ends of the columns; Erect a melon column (that is, a short column, which is called a melon column because it is made into a melon shape) on the beam, and then erect a beam on the melon column; Erect melon columns and beams again ...; Layer upon layer. The length of the beam is gradually shortened from bottom to top. In the middle of the top beam, a ridge melon column is erected. According to a certain law, the height between two beams decreases from top to bottom layer by layer (that is, Song's lifting) or increases from bottom to top (that is, Qing's lifting), thus forming a roof truss composed of beautiful and soft curves, and each group of curves is called a seam. Purlins are erected at the end of each beam between two parallel-jointed roof trusses and at the top of the melon pillars on the roof to form a whole, and then the purlins are connected. Two-seam frame, that is, the space formed by four columns, is the basic unit of ancient architecture-room. The two rooms are composed of three-seam room frames arranged in parallel; Four seams make up three rooms. Ancient buildings are generally composed of odd bays of 3, 5, 7 and 9. The number of overlapping beams in the joint room depends on the scale and depth of the building.

Due to the limitation of wood length, mining and transportation conditions and mechanical properties, it is impossible to make the depth too large. In order to meet the use requirements of larger space, on the basis of the above-mentioned basic residential frame, the depth of the building is increased by inserting gold beams or hooks. The inserted gold beam is a short column outside the front and rear columns of the basic building frame, and the inserted gold beam is placed on it. The beam head is placed on the outer column head, and the beam tail is inserted into the column body of the foundation building frame. The inserted gold beams can also be stacked layer by layer to increase the depth. Hooking is to connect two, three or more groups of house frames into a joint house frame along the depth direction, and the two groups of house frames at the joint use a column, so it is called hooking.

The beam in the beam-lifting wood structure bears the concentrated load transmitted from the upper floor to form a flexural member, and the load increases step by step from the roof ridge down, and the cross section of the beam also increases step by step with the increase of the load. In early physical objects, the length-width ratio of beam section is often 2: 1 ~ 3: 2. Nanzenji, built in 782 in the third year of the Tang Dynasty, added diagonal braces between the upper and lower beam ends, which are called braces. It transforms part of the vertical force at the upper beam end into horizontal component force, which makes the lower beam produce a certain tensile stress and reduces the bending stress of the lower beam. It is a more scientific and reasonable structure. But this structure was rarely used in Ming and Qing Dynasties. Columns are compression members that bear vertical loads; In the early physical objects, the stigma of the columns around a building tilted slightly to the center, which was called lateral foot; And along the outer wall from the center to the four corners, the column is raised, which is called rising. These two measures make the center of gravity of the building structure slightly tilt inward, and make the tenon-mortise joints more compact and firm, thus improving the overall stability of the structure. After the Ming dynasty, the lateral foot gradually decreased and rose very little.

In addition to rectangular layout, the building plane of lifting beam wood structure can also be arranged in various plane forms such as square, hexagon, octagon, circle and cross according to the purpose and architectural art requirements.

The weight of the roof of the rising beam building is transferred from purlin to beam, from beam to column, and from column to foundation. The wall of a building only plays the role of partition or enclosure, not a load-bearing structure, that is, the so-called wall does not collapse. But the wall still has a certain effect on the overall stiffness of the building.

Penetrating wood structures are widely used in buildings in southern China. Its basic components are columns and penetrations (also called penetrations). Bucket-through wood structure is a column along the depth direction of the building. Its main differences from the beam-type wood structure are as follows: ① The column head directly supports purlins and does not need to transfer loads through beams, so it has higher bearing capacity than the beam-type wood structure; (2) There are many landing columns with dense column spacing; (3) The columns in the single-seam building frame are connected into a whole through purlins that run through the columns. The pillars of bucket wood structure gradually increase from front to back to the center (roof ridge) along the depth direction, forming an arc roof similar to beam wood structure. In the bucket-type wood structure, because the load borne by the column is much smaller than that of the beam-lifting structure, the diameter of the column is also reduced accordingly, which plays the role of small-diameter wood, which is not only economical in materials, but also lighter in posture. However, the reduction of column diameter increases the slenderness ratio of the column, so multiple purlins should be set along the column body, and the axial stability of the column should be ensured by the pull rod parallel to the purlin and the pavilion plate laid on it. Because purlins are mainly used for communication, they are not large in size. The bucket structure is also a room composed of purlins between two seam frames. Its disadvantage is that the material is fine and it is difficult to bear the load of heavy roof, so it is rarely used in northern China. And there are many landing columns, so it is difficult to form a large complete space. Therefore, another practice can be seen in the south of China, that is, in the same building, the beam structure is adopted in the middle and the barrel structure is adopted at both ends to meet the requirements of greater indoor space.

Dry wood structure is made of logs (or squares) stacked, and most logs are simply processed and stacked vertically and horizontally to form a rectangular space. This structure exists not only in China, but also in countries rich in forest resources. As early as 3,000 years ago, China discovered the use of well-dried wooden coffins in Shang tombs, and this structural form can also be seen in Han dynasty artifacts found in Yunnan. According to records, during the period of Emperor Wu of the Han Dynasty, there was a tall well-stem building in the palace: the description of "the well is dry but not half, and the eyes turn to frustration" shows that the well-stem structure has a history of not less than 3,000 years in China, and it is still used in wood producing areas today.

Ancient wooden structures in China are widely used in low-rise buildings such as palaces, temples and houses, as well as multi-storey or high-rise buildings. As early as the Spring and Autumn Period, heavy houses were built, and many architectural patterns carved with two or three layers can be seen on the bronze wares of the Warring States Period among the unearthed cultural relics. Since the Qin and Han Dynasties, the number of multi-storey pavilions has increased, and the construction of pavilion-style wooden towers in the Northern Dynasties was in its heyday, the most famous of which was the Yongning Temple Tower in Luoyang built in Xiping period of the Northern Wei Dynasty. According to "Luoyang Galand Ji", "There are nine-story floating pictures in the temple, which are erected with wood and are 90 feet high, with a brake and 10 feet high. Go to thousands of feet, go to the capital, and look at it from afar. " In Zhuhe, the height of the tower was recorded as more than 40 feet, but in fact, the 40 feet at that time had exceeded 100 meter, which is enough to prove China's outstanding achievements in high-rise wood structures in the early 6th century. It's a pity that the tower was destroyed in the fire soon after it was built. The existing high-rise wooden structure is represented by the Saga Pagoda of Fogong Temple in Yingxian County, Shanxi Province (see color map [Buddha Pagoda (Yingxian Wooden Pagoda), an ancient wooden structure in China, located in Yingxian County, Shanxi Province, built at 1056] and Figure 3 [Saga Pagoda Structure]) (commonly known as Yingxian Wooden Pagoda). The tower has five outer layers and four hidden layers. The structure adopts two circles of wooden column nets inside and outside, and each layer consists of beams, squares and buckets. It is powerful and abnormal. It has been more than 900 years since it was built, and it still stands tall after many earthquakes.

In the ancient wooden structure of China, the use of bucket and the tenon-mortise structure of connecting members are very unique and exquisite.

Bucket is the general term of "bucket" and "bucket", which is often used at the junction of beams, columns, purlins and other components and between purlins. It is a unique wooden component of ancient buildings in China (Figure 4 [Bucket 1, Flat Square 2, Sitting Bucket 4 5] .5438+0. [6] Cover the bucket plate), whose main functions are: ① Increase the contact surface of the components at the joint through the bucket body, improve the stress situation at the joint, and shorten the net span of the supported components. (2) The far eaves of the building are supported by buckets layer by layer. Although the exact date of the capital of Dou can't be verified, the image of Dou was found in the "Ling" casting in the Western Zhou Dynasty more than 3,000 years ago, and it developed quite maturely and was widely used from the Eastern Han Dynasty to the Three Kingdoms period, which became the embryonic form of the development of ancient architecture to "modular system" and "standardization". Since the Tang and Song Dynasties, bucket has become the basic unit of measurement of architecture. The early bucket was mainly to meet the needs of functions, such as the Guanyin Pavilion of Dule Temple in Jixian County, Tianjin (see the color map [Guanyin Pavilion of Dule Temple, an ancient wooden structure in China, located in Jixian County, Tianjin, built in 984]) and other buildings. Later, the ingenious combination of function and art became one of the characteristics of ancient wooden structures in China. After the Ming dynasty, the bucket gradually developed to be slender, so its function was weakened and its decorative function was highlighted.

Mortise and tenon The components of China wood structure mainly rely on mortise and tenon connection (Figure 5 [mortise and tenon]), such as whole tenon, half tenon, single tenon, double tenon, tenon with angle, pin tenon and silver ingot tenon, which not only properly solves the connection of various components, ensures the firmness of structural nodes, but also makes this connection elastic and plays a good role in energy consumption. Therefore, ancient wooden palaces and temples have good resistance to natural disasters such as earthquakes and strong winds because of their perfect tenon-mortise connection and reasonable structural layout.

philology

Liu Dunzhen, editor-in-chief: History of Ancient Architecture in China, China Building Industry Press, Beijing, 1980.