Brick and wood structure seismic performance?

0 Introduction Brick and wood structure is the characteristic of wood structure building in China, which is still commonly distributed in the vast rural areas of China and has good anti-seismic performance. In the Wenchuan earthquake, most of the houses in Bikou Town, Wenxian County, Gansu Province, were found to be seriously damaged, except for a brick and wood structure house in Doujiaba Village, which had almost no damage. After the news was transmitted to the Internet, causing widespread concern among netizens, this house is known as the most cattle houses. We can see from this event on the brick and wood structure has good seismic performance, then we will briefly explore why this brick and wood structure has such excellent seismic performance.1 brick and wood structure of the introduction of brick and wood structure houses is to masonry clay brick walls as load-bearing walls, windows, doors and roofs for the wooden structure of the single-story and multi-story houses, part of the house has a concrete ring beams and structural columns. Generally, brick and wood structure house adopts wooden roof, and the purlins are set aside on the cross wall, and the wall is responsible for load bearing, shear resistance and meeting the structural requirements. Brick and wood structure houses have the following characteristics: vertical load is relatively small, wood has good elasticity, smooth grain tensile and transverse grain shear capacity, and the roof frame longitudinal and transverse support connection to form a spatial system, so as long as the nodes are not damaged, can effectively play a role in earthquake resistance, so the brick and wood structure houses are widely used in the rural areas in the earthquake zone. Brick and wood structure in the Wenchuan earthquake showed good seismic performance is not accidental. In the Tangshan earthquake more than 30 years ago, almost all the buildings in the city were razed to the ground, leaving only two wooden houses standing. In the 1995 Kobe Earthquake in Japan, it was also proved that wood-frame houses have good seismic performance. The economic losses caused by the Kobe earthquake amounted to 800 billion yuan, and other structures were severely damaged, but the modern wooden houses in the disaster area were almost unaffected. Shaking table tests show that the brick and wood structure itself has good seismic performance. With reinforced concrete structural columns and ring beams of single-story brick and wood structure house model overall stiffness is larger, stronger seismic capacity, can withstand 9 degrees of the earthquake and do not fall, to meet the 8 degrees of the basic fortification intensity of the verification of the proposed housing structure to resist the high intensity of the earthquake, for the popularization of earthquake-resistant housing to provide a reference basis [3]. 2 Wenchuan earthquake in the wood structure of the main damage and causes of the houses according to the relevant data [2]. According to the relevant data[2], the wooden structure houses in the Wenchuan earthquake area are mainly brick and wood structure or earth and wood structure. Most of the remote houses in rural areas are adobe walled houses with wooden frames (roofs of tiled roofs supported by wooden frames). A small number of houses have adobe walls and wooden roofs. The seismic damage of wood-framed houses is mainly manifested in the following ways: the earth wall of the adobe walled houses with wooden frames collapsed, and the roof frame partially collapsed (Fig. 1); part of the wall of the adobe walled houses with wooden roofs collapsed, and the wooden roofs were seriously damaged (Fig. 2). Only a few wooden structures have collapsed as a whole. As can be seen from the above data, wooden houses are mainly damaged by the use of low-strength and highly discrete earth as walls, which is mainly caused by the irrationality of rural construction, not by the structural problems of the wooden structures themselves. The quality of construction is also a major cause of structural damage, and the seismic capacity of the same structure can be very different depending on the quality of construction. The wood frames and roofs remained intact and basically intact after the earthquake. This indicates that the brick and wood structure of residential houses is a good seismic performance.3 the most cattle houses of structural characteristics according to the Gansu Provincial Earthquake Bureau, Director of the Emergency Response Division, Jing Tianxiao introduction, this house in 1998 when the construction did not give much consideration to seismic function, ordinary brick and wood structure of the house, did not use the concrete ring beams and structural columns. Unlike other houses, the roof is covered only with wooden rafters and green tiles, which are lightweight. As for other aspects, the first floor is completely made of high-quality solid bricks, while the second floor is made of hollow bricks; and the interval between rooms is not made of brick walls, but is separated by wooden materials. The brick and wood structure is greatly reduced by the use of a wooden roof, and the second floor of the house is made of hollow bricks, which reduces the weight of the building even more. In this way, from the point of view of structural dynamics and seismic resistance, the phenomenon of top-heaviness is avoided. Similarly, the use of wood for the room partitions reduces the dead weight of the second floor. At the same time, the wood itself has elasticity, which can cushion and decompose seismic forces to a greater extent. Under the action of seismic force, it also plays a role in reducing earthquake damage. According to the Wenchuan earthquake related data report [4], brick and wood structure in the 0-10g region of the earthquake damage is slight, in the 0-15g and 0-20g region of the earthquake damage is serious, mainly because the structure itself does not use sufficient seismic defense structure, its weak parts are mainly roof system and independent brick columns. The roof of the best private house is only covered with wooden rafters and green tiles, which is lightweight, has strong integrity, is more reliably restrained, and generates less inertia force under the action of seismic force. The structure of the most cattle houses does not use independent brick columns, but the use of ordinary wall load-bearing structure, the structural form is more symmetrical, which is conducive to the seismic role of the house.4 Brick and wood structure of the seismic mechanism of the brick and wood structure in the earthquake showed good seismic performance is mainly due to the following reasons: (1) a reasonable structural layout. On the plane, brick and wood structure is seldom used in buildings with complex plan, mainly rectangle with aspect ratio not more than 2:1. Regular plan layout is conducive to structural seismic and energy consumption, which is widely recognized by the architectural community. Space, the use of wood roofs, lightweight while maintaining a good integrity, such structural forms to avoid the lightness of the building's head, is the ideal seismic structural design; (2) wood roof mortise and tenon energy consumption. The mortise and tenon joints of the wooden structure of ancient buildings are the essence of China's architecture. Tongue and groove has a strong seismic energy consumption performance. The mortise and tenon joints have a strong deformation property when they are subjected to large loads. Under the action of seismic load, mortise and tenon dissipates a lot of seismic energy, reducing the damage to the structure itself; (3) the building structure is more integral. Timber has a very good tensile strength and cross grain shear strength, such a structure to make a strong integrity of the roof, in the role of lateral support, and the surrounding walls to form a good spatial system. Such a system can have good seismic capacity as long as there is no damage at the nodes.5 Reconstruction Suggestions (1) Promote the use of brick and wood structure buildings. Brick and wood structure has good seismic performance and has strong national characteristics in remote rural areas of China. Brick and wood structures are characterized by low cost, relatively simple structure and low construction requirements. These features in China's rural areas are very attractive. Japan's Kobe earthquake after the Japanese government ordered all civil housing must be used in North America wood structure villa and the implementation of JAS building standards. [2] China should also combine with its own national conditions, and actively promote the building structure with good seismic performance. In the context of the Wenchuan earthquake, the government stepped in to actively guide is of great significance; (2) strengthen the rural residential construction management. It is also important to point out that, due to the fact that China's rural self-built houses are not included in the national construction management program, the lack of management of rural dwellings, basically random design, not only did not take into account the requirements of anti-seismic setup, but also often have serious design defects. The quality of construction is not guaranteed by unqualified construction teams. These are the existing construction problems in China, which need to be solved urgently. So strengthen the management of rural residential construction, set up seismic awareness, actively respond to the possible dangers, and become passive disaster relief for active prevention, which will get twice the result with half the effort; the most cattle houses are not accidental. It is the structural characteristics of the brick and wood structure itself. The experience of the most cattle houses should be the attention of the majority of workers in the field of construction. Brick structure is worthy of in-depth study of seismic structural forms, and has the potential to be widely promoted. This paper hopes to attract the attention of relevant experts and contribute to the development of China's seismic cause.

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