Discussion on deformation joint and its fire preve

2022-08-10
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Discussion on deformation joints and their fire protection requirements

in high-rise buildings, due to temperature, settlement, earthquake resistance and other reasons, 13. The accuracy of displacement indication is often left in some parts: 1% cracks better than the indication. These cracks divide the high-rise building into several independent parts of the structure, which is what we usually call deformation joints. The setting of deformation joints can solve the problems of excessive deformation and internal force of high-rise buildings, but it also produces many new problems. For example, it is difficult to deal with the facade, leakage of underground parts, waterproof difficulties, etc., and the building fire prevention problem is more hidden and dangerous. The deformation joint runs through the whole building up and down, and the caulking material has a certain combustibility, and the part involved here is small, which often does not attract people's attention. Due to the chimney effect, the fire and smoke can spread and expand rapidly through this part, resulting in the complete failure of the vertical fire prevention zone, which is very dangerous

deformation joints are divided into temperature joints, settlement joints and anti vibration joints. The temperature joint is also called expansion joint. The high-rise building structure has not only a large plane scale, but also a large vertical height. The temperature change and concrete shrinkage will not only produce horizontal deformation and internal force, but also produce vertical deformation and internal force. When the following necessary structural and construction measures are taken, temperature joints can also be set on longer sections. 1. Increase the reinforcement ratio in the part with greater temperature influence; 2. Thickened roof thermal insulation layer; 3. Post cast strip shall be reserved during construction

when there is a significant settlement difference between each part of the same building due to foundation settlement, which may produce internal forces and deformation that the structure cannot bear, settlement joints can be used to separate the two parts. There are two kinds of differences in foundation settlement: one is that the foundation is obviously uneven; the other is that the number of floors in the same high-rise building varies greatly, and the load varies greatly. The most typical is the difference in settlement between the main building and the podium. The settlement joint shall not only penetrate the superstructure, but also the foundation itself. After setting settlement joints, the superstructure must set independent lateral force resistant structural forms of double beams, double columns and double walls on both sides of the joints. There are many structural problems in the building. After the building is put into use for a certain period of time, the free settlement of all parts avoids the internal force generated by uneven settlement, but the base course and surface decoration materials of the joint will have cracks, which increases the possibility of fire spreading along the joint. When the post pouring section is left as the temporary settlement joint during the construction process, and then connected as a whole after the settlement is basically stable, the permanent settlement joint can not be set. This method can be used in the main building and podium of high-rise buildings

when the number of floors, quantity and stiffness of each part of high-rise buildings in areas with fortification intensity above 6 are too different, or there are staggered floors, seismic joints should be set. When expansion joints and settlement joints are set in each structural unit, their joint degrees should meet the requirements of the width of seismic joints. The seismic joint shall be set along the full height above the ground. When it is not used as a settlement joint, the foundation may not be equipped with seismic joint. Because the vibration conditions between units, especially between high and low floors, are different during an earthquake, the connection (2) Rockwell hardness (HR) is easy to crush and break. The width of the anti earthquake joint is generally large, and the risk of preventing and post earthquake fire is also large

after in-depth discussion of the above three forms of deformation joints, we can draw the following conclusions:

first, high-rise buildings should comprehensively adjust the plane size and structural layout, and take appropriate structural and construction measures. If there are fewer joints, there will be fewer joints, and if there are no joints, there will be no joints

II. If no measures are taken or joints must be set, the parts must be completely separated, that is, set along the full height from the foundation part to the superstructure, and the necessary joint width must be guaranteed to prevent earthquake and fire

III. The deformation joints shall be sealed with asphalt mortar, the base course shall be made of concrete slab or galvanized steel plate grade a materials, and the surface decoration shall be made of decoration materials not lower than grade B1

IV. shear walls or frames should be arranged on both sides of the deformation joint, and it is best not to cross the room. The fire door set near the deformation joint should be set on the side of Dow, which has more floors, on the basis of the early cooperation between the two sides, and the door should not cross the deformation joint after it is opened

v. cables, combustible gas pipelines and class A, B and C liquid pipelines should not be attached in the deformation joint. When they pass through the deformation joint, non combustible material casing should be added at the crossing point, and the gap of the casing should be filled tightly with non combustible material

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