Bian Xiao sorted out the basic situation of short-leg shear wall through the architectural knowledge column of the encyclopedia website "Construction Network" of the construction industry. The basic contents are as follows:
Short-leg shear wall, that is, short-leg shear wall, refers to the shear wall whose section thickness is not more than 300mm and the maximum height-thickness ratio of each limb section is more than 4 but not more than 8.
In order to help construction enterprises understand the stress of short-leg shear wall, Zhong Da Consulting Company analyzed the stress of short-leg shear wall. The main stress types are: (1) short-leg shear wall structure (2) special-shaped column structure, and the basic situation of short-leg shear wall structure is as follows:
1, short-leg shear wall structure
Short-leg shear wall structure refers to the shear wall structure in which the length of the wall limb is 5-8 times the thickness, and commonly used ones are "T", "L", "X", "Z", "polyline" and "I".
This type of structure is characterized by:
(1) According to the building plane, the vertical members are arranged by using the position of partition wall, which basically does not conflict with the building function;
② The number of walls can be more or less, and the limb length can be longer or shorter, mainly depending on the need of lateral force resistance, and the position of stiffness center can be adjusted by different sizes and arrangements;
(3) Flexible layout, multiple choices and simple plane layout;
(4) The beam connecting the wall is located in the plane of the partition wall perpendicular to the position of the wall limb and can be concealed;
⑤ According to the need of lateral stiffness of building plane, the central shear wall is used to form the main lateral force resisting member, which is easy to meet the requirements of stiffness and strength.
The design and calculation of short-leg shear wall structure is basically the same as that of ordinary shear wall structure, and three-dimensional tie rod-book column spatial analysis method or spatial tie rod-wall component analysis method can be used. The former is TBSA and TAT of Architectural Institute, SS module of Guangsha CAD of Guangdong Architectural Design Institute, and the latter is TBSSAP and SATWE of Architectural Institute, TUS of Tsinghua University, SSW of Guangdong Architectural Institute, etc. Among them, the calculation model of spatial beam-wall component analysis method is more in line with the actual situation and has higher accuracy. Although the spatial analysis program of three-dimensional bar system-thin-walled column is used earlier and widely, the spatial bar-wall component program should be used for checking the long-wall and short-leg shear walls.
After the above analysis, according to the Code for Design and Construction of High-rise Buildings, the theory and practice of short-leg shear wall structure is more mature than that of special-shaped column structure, but there are still some aspects that need attention in structural design.
(1) Because the lateral stiffness of short-leg shear wall structure is smaller than that of ordinary shear wall structure, it is necessary to arrange an appropriate number of long walls in the design, or use elevators and staircases to form an inner tube with greater stiffness to avoid large deformation of the structure under the fortification intensity, and at the same time form two seismic fortification measures;
(2) The weak seismic part of the short-leg shear wall structure is the wall limb at the corner of the outer edge of the building plane. When there is torsion effect, it will aggravate the existing warping deformation and make the wall limb crack first. Therefore, the seismic structural measures should be strengthened, such as reducing the axial compression ratio and increasing the reinforcement ratio of longitudinal reinforcement and stirrup;
(3) Under the action of horizontal force, the high-rise short-leg shear wall structure presents overall bending deformation, and the small wall limb at the bottom bears large vertical load and torsional shear force, which is reflected in some model tests. Therefore, the thickness and reinforcement of the peripheral retaining wall limb should be increased to strengthen the ductility and seismic performance of the peripheral retaining wall limb. Short-leg walls should be connected in two directions to avoid the formation of isolated I-shaped wall limbs;
(4) The distribution of each wall limb should be as uniform as possible, so that its stiffness center is as close to the centroid of the building as possible, and the stiffness center should be adjusted with long limb walls when necessary;
(5) The coupling beams in high-rise structures are energy-consuming components. In the short-leg shear wall structure, the stiffness of the wall limb is relatively reduced. The beam connecting the wall limbs is similar to the ordinary frame beam, but different from the coupling beam between ordinary shear walls. In the overall information of calculation, the stiffness of coupling beam should not be greatly reduced, thus reducing its design internal force. The height of concrete compression zone should be controlled according to the requirements of ordinary frame beams, and the negative bending moment reinforcement at the beam end can be adjusted by 70%-80% through plasticity.
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