1. The basic concept of shear wall
The shear wall structure is to replace the columns in the frame structure with reinforced concrete wall panels, which can bear the internal forces caused by various loads and can effectively control the horizontal force of the structure. This kind of reinforced concrete wall panels can bear vertical and horizontal forces The structure is called shear wall structure. This structure is widely used in high-rise buildings. The characteristic of the shear wall section is that the length of the wall limb is much greater than the thickness, and it has a large stiffness and bearing capacity in its own plane, and the out-of-plane stiffness and bearing capacity are relatively small. At the same time, in the structure of shear wall, the wall is a plane member, in addition to the horizontal shear force and bending moment acting along its plane, it also bears vertical pressure; it works in the composite state of axial force, bending moment and shear force It is like a cantilever deep beam whose bottom is embedded on the foundation when it is subjected to horizontal force. In addition to the stiffness and strength requirements, the shear wall under earthquake action or wind load must also meet the requirements of ductility, energy dissipation and control of structural cracking without collapse under repeated cycles of inelastic deformation.
2. Structural layout
The principles of uniformity, dispersion, symmetry and surroundings should be followed. Shear walls should be arranged in both the vertical and horizontal directions of the house, and as little as possible when the displacement limits are met. The shear wall should be set to ” L “, ” T “, ” U ” shape, try not to set “1” shape wall. In the vertical arrangement, the shear wall should penetrate the full height of the house to make the up and down rigidity of the structure continuous and uniform.
2.1 The principle of arranging shear walls in the middle of the structure
Shear wall for floor beam arrangement. Because pure shear wall structures are mostly used in residential buildings, the construction profession has many restrictions on the arrangement of structural beams to meet the functional requirements. The structural personnel should first consider the beam layout when getting the building drawings, and avoid the occurrence of overly complicated relations between the primary and secondary beams. If the relationship between the primary and secondary beams is too complex and the secondary beams have too many stages, it is possible that the failure of the primary beam will cause the relevant areas of the structure to lose their use function, which is not allowed by the structural design concept. Shear wall required for floor beams.
Shear wall installed at the place with large constant load and in the building (electric) ladder. Due to the opening of the floor and the influence of stair components, the building (electrical) staircase is the weak link of the structure, and the staircase is also the only escape route for the building in the event of an earthquake, so it can be arranged around the building (electrical) staircase Shear wall should be fully arranged at the place of shear wall, which can not only be used as the reinforcement of weak link, but also can form a cylinder to provide vertical rigidity for the structure.
2.2 Principles of arranging shear walls around the structure
The surrounding shear wall can provide vertical stiffness to the structure to reduce the displacement of the structure, and can also improve the torsional stiffness of the structure and reduce the torsional period. When arranging the surrounding shear walls, the walls allowed by the building should be arranged as far as possible. The length of the limb in the other direction connected to the surrounding shear wall should be increased or decreased according to the needs of structural displacement calculation on the premise of satisfying the function of the building.
2.3 Long walls should be arranged as far as possible without violating the regulations
From the economic point of view, if the structure of the shear wall is short and large, the number of hidden columns in the shear wall will also be large. If a long wall is installed, some unnecessary walls or openings will be reduced, so that the number of hidden columns in the shear wall is small. When the number of walls is the same, the amount of rebar can be reduced, and a certain time will be saved in the construction drawing.
3 Model adjustment
According to the preliminary layout of the shear wall and beams, a calculation model ( PKPM ) is established , and one to two standard floors are built (two standard floors must be established when there are many floors and the calculation of the strain wall thickness) to carry out the preliminary calculation of the structure. The preliminary calculation is mainly to determine the regularity of the model and adjust the vertical stiffness. The preliminary calculation in the specific parameters should achieve the following effects:
the rules of cycles and cycle ratios. In general, high-rise buildings with pure shear wall structures are not too complicated. When adjusting the structure, Tt / T1 ≤ 0.9 ( level A high-rise) should be satisfied first . If the cycle ratio is not satisfied, it means that the torsional stiffness of the structure is relatively small. During the adjustment, the surrounding shear wall should be increased, the surrounding beam should be heightened (if the building facade allows) or the intermediate shear wall should be reduced. PKPM calculation, after the period ratio to meet the requirements, the period should be adjusted coefficient translational and torsional coefficient, X- direction, the Y moving to the main level of the first coefficients from the translational vibration period and from the first to reverse based The torsion coefficients of the vibration period should be close to 1.00 .
The displacement is close to the limit, and the displacement ratio when accidental eccentricity is not considered is close to 1.00 . The size of the displacement and displacement ratio is the most intuitive data showing how much the structural shear wall is arranged. On the one hand, enough shear walls should be arranged to meet the displacement requirement of 1/1000 ; on the other hand, the number of shear walls must not be too large, otherwise it is not economical. In the actual initial adjustment of the model, the displacement ( X direction, Y direction) should be controlled to about 1/1000 ; for the displacement ratio when accidental eccentricity is not considered, it should also be adjusted to 1.00 or close to 1.00 . This displacement ratio more directly represents the structure in The regularity of displacement under the influence of action. If this ratio is too large, it is caused by an excessive displacement of a part or a point of the structure due to an unreasonable structure. If the displacement is controlled to 1/1000 at this time, it indicates that the shear wall is relatively arranged. On the contrary, if the displacement is 1/800 ~ 1000 at this time, the local shear wall may be found by finding the point where the local displacement is too large. Adjust to achieve the displacement of 1/1000 .
In structural adjustment, the center of mass and rigidity should be as close as possible or basically coincident. The coincidence of the center of mass and rigidity can prevent the structural rigidity from being biased in a certain direction and reduce the torsional effect, which is very helpful for the adjustment of the displacement ratio and the cycle ratio. The adjustment method is to increase the shear wall in the opposite direction of the rigid center offset or decrease the shear wall in the direction of the rigid center offset according to the magnitude of the displacement.
The adjustments of period, displacement and super-ribs are not isolated. They are related to each other and influence each other. They should be fully considered. They cannot be “headaches, heads, feet”. After completing these three adjustments, the shear wall The layout is basically determined, and the next step is to carefully model and adjust the super-ribs of the coupling beam.
After the model is refined, if there are local coupling beams with extra ribs, the following methods can be used to adjust.
amplitude modulation method. The bending moment and shear force of the connecting beam in the seismic design shear wall can be plastically amplitude-modulated to reduce its shear design value. However, in the structural calculation, the stiffness of the connecting beam has been reduced, and its amplitude adjustment range should be limited or no more. When the design value of the bending moment is reduced for some connecting beams, the bending moments of the connecting beams and the wall legs of the remaining parts should be increased accordingly. The coupling beam treated by amplitude modulation method shall ensure that the coupling beam has no obvious influence on the vertical load.
Second: reduce and increase the beam height. Reducing the beam height reduces the internal force of the beam, which is very effective for adjusting the over-reinforcement under normal circumstances. However, when the structural displacement is close to the limit, it may cause the displacement to exceed the limit. Adding Dalian beam height The internal force of the connecting beam is increased, and the resistance is also increased, which may make the connecting beam not exceed the reinforcement, and can reduce the displacement, but this method may be limited by the building height of the beam, and the height of the connecting beam If it exceeds a certain limit, the structure needs to be strengthened, which also causes an increase in the amount of reinforcing steel.
Third: Add the Dalian beam span. It can effectively solve the problem of over-reinforcement of connecting beams, but shortening the shear wall may cause increased displacement.
The above one and several methods can be used together during design. If the individual connecting beam super-reinforcement still exists, it is also possible to increase the reinforcement of the connecting wall limbs and the amount of the Dalian coupling to make the reinforcement can bear the maximum shear capacity of the section.
The above is the explanation of “Method of Layout of Shear Wall Structure Model” . Part of the information comes from literature and online information. If there is any infringement, please contact the webmaster in time.
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