The frame structure house refers to the house which is made of reinforced concrete cast into load-bearing beams and columns, and then assembled with prefabricated aerated concrete, expanded perlite, pumice, vermiculite, ceramic rotten and other light-weight plate partition walls. Suitable for large-scale industrial construction, with high efficiency and good project quality.
The frame structure is composed of beams and columns, and the cross-section of the member is small. Therefore, the bearing capacity and stiffness of the frame structure are low. Its stress characteristics are similar to vertical cantilever shear beams. The higher the floor, the slower the horizontal displacement. Both horizontal and vertical directions are subject to a large horizontal force. At this time, the cast-in-place floor also works as a beam, and the role of assembling the integral floor is not considered. The wall of the frame structure is filled with walls, which serves as an enclosure and Separation function, the characteristic of the frame structure is that it can provide flexible use space for the building, but the seismic performance is poor.
The main advantages of the frame building: flexible space separation, light weight, conducive to earthquake resistance and material saving; it has the advantage of being more flexible to match the layout of the building, which is conducive to arranging building structures that require a larger space; the beam and column members of the frame structure are easy Standardization and stereotyping make it easy to adopt an assembled monolithic structure to shorten the construction period; when using cast-in-place concrete frames, the integrity and rigidity of the structure are better, and the design and treatment can achieve better earthquake resistance. The columns are cast into various required cross-sectional shapes.
The difference between frame structure and brick-concrete structure
The main difference between the frame structure and the brick-concrete structure is the load-bearing method. The load-bearing structure of frame-structured houses is beams, slabs, and columns, while the load-bearing structure of brick-concrete structures is floors and walls. In terms of firmness, in theory, the firmness that the frame structure can achieve is greater than that of the brick-concrete structure, so when the brick-concrete structure is designed for construction, the building height cannot exceed 6 floors, while the frame structure can achieve dozens of floors.
However, in the actual construction process, the state stipulates the earthquake resistance level that the building must achieve, whether it is brick or concrete or frame, it must reach this level, and the developer will use the frame structure to build the house, and will not improve the building's strength. Increase investment, as long as it meets the earthquake resistance level.
In terms of sound insulation, the sound insulation of brick-concrete residences is moderate. The sound insulation of the frame structure depends on the choice of partition materials. Some advanced insulation materials are better than brick and concrete, while ordinary partition materials, such as cement Hollow slabs and the like have poor sound insulation.
If you are going to renovate the interior space, the frame structure because most of the walls are not load-bearing, so the reconstruction is relatively simple, just knock off the walls, and many walls in the brick-concrete structure are load-bearing structures, which are not allowed to be demolished, you You can only make a fuss on a few non-load-bearing walls. A simple way to distinguish between load-bearing walls and non-load-bearing walls is to look at the wall thickness. A wall with a thickness of 240 mm is load-bearing, and a wall of 120 mm or less is non-bearing.
The difference between frame structure and frame shear structure
The main difference between the frame-shear structure and the frame structure is the addition of shear walls, and the lateral rigidity of the frame structure is not strong, especially for high-rise or super-high-rise frame structure buildings! In order to solve this problem, shear walls (or seismic walls) are used. Shear wall is an uninterrupted lateral force member from the top surface of the foundation to the design height. Its lateral rigidity is large, but the lateral rigidity of the lateral plane is small, so it is generally not considered to bear vertical loads. Of course, of course, the shear wall can also play a role of enclosure and separation of the wall.
Frame shear wall structure
Commonly referred to as frame-shear structure, it is a combination of frame structure and shear wall structure. In addition to the frame layout, some shear walls (or seismic walls) are added to the structural plane layout to absorb their own strengths. It provides large space for building layout and good lateral resistance. The shear walls in the frame-shear structure can be set separately, or walls such as elevator shafts, stairwells, and pipe shafts can also be used. Therefore, this structure has been widely used in various types of housing construction.
The deformation of the frame structure is shear type, with relatively small deformation between the upper layers and large deformation between the lower layers. The deformation of the shear wall structure is curved, with relatively large deformation between the upper layers and small deformation between the lower layers. For the frame-shear structure, due to the coordinated deformation and deformation of the two structures, bending shear deformation is formed, which reduces the relative displacement ratio and vertex displacement ratio between the structural layers and improves the lateral rigidity of the structure.
From the point of view of stress characteristics, since the lateral stiffness of the shear wall in the frame-shear structure is much greater than that of the frame, under horizontal load, under normal circumstances, more than 80% of the shear wall is used to bear. Therefore, the distribution of the floor shear force under the horizontal load of the frame structure is evenly distributed along the height, and the bending moments of the beams and columns of each layer are relatively close, which is helpful to reduce the beam and column specifications and facilitate construction.
In the seismic design of the structure, the shear wall of the frame-shear structure is the first line of defense, and the frame is the second line of defense.
The frame structure can be designed as a statically determinate three-hinge frame or an ultra statically determinate double-hinge frame and a hingeless frame. Concrete frame structures are widely used in residential, school, and office buildings, and there are also prestressed concrete beams or slabs as needed to apply to larger spans; frame steel structures are often used in large-span public buildings, multi-story industrial plants, and some In special-purpose buildings, such as theaters, shopping malls, stadiums, railway stations, exhibition halls, shipyards, hangars, parking lots, light industrial workshops, etc.
1. The cross-sectional dimensions of the beam should meet the following requirements:
(1) The section width should not be less than 200mm;
(2) The cross-sectional aspect ratio should not be greater than 4;
(3) The ratio of net span to section height should not be less than 4.
2. When flat beams with a beam width greater than the column width are used, the floor slab should be cast-in-place. The small beam line should coincide with the center line of the column. The flat beams should be arranged in both directions and should not be used for primary frame structures. The cross-sectional dimensions of the flat beam shall meet the following requirements, and shall meet the deflection and crack width provisions of the current relevant specifications.
3. The reinforcement configuration of the beam should meet the following requirements:
(1) The reinforcement ratio of the longitudinal tensile reinforcement at the beam end should not be greater than 2.5%. And taking into account the ratio of the height of the compressive area of ​​the beam end concrete under compression to the effective height, the first level should not be greater than 0.25. The second and second levels should not be greater than 0.35.
(2) The ratio of the longitudinal steel reinforcement at the bottom and top of the beam end section shall be less than 0.5 at the first level and less than O at the second and third levels, except as determined by calculation.
(3) The length, maximum spacing and minimum diameter of stirrup reinforcement area at the beam end shall be adopted in accordance with Table 12-29. When the longitudinal reinforcement reinforcement ratio at the beam end is greater than 2%, the minimum diameter value of stirrup in the table shall be Increase 2mm.
4. The longitudinal reinforcement configuration of the beam should still meet the following requirements:
(1) The reinforcement along the top and bottom of the full length of the beam should not be less than 2φ4 for the first and second levels, and should not be less than 1/4 of the larger cross-sectional area in the longitudinal reinforcement at the top and bottom of the beam at both ends , Level 4 should not be less than 2φ12;
(2) The diameter of each longitudinal steel bar passing through the middle column in the first and second frame beams should not be greater than 1/20 of the cross-sectional dimension of the column in the direction for rectangular section columns; it should not be greater than the location of the longitudinal reinforcement for circular section columns 1/20 of the chord length of the cylindrical section.
5. The distance of stirrups in the reinforced area of ​​the beam end should not be greater than 200mm and greater than 20 times the diameter of stirrups in grade one. Grade two and three should not be greater than 250mm and greater than 20 times the diameter of stirrups. Grade four should not be greater than 300mm.
6. The cross-sectional dimensions of the column should meet the following requirements:
(1) The width and height of the section should not be less than 300mm; the diameter of the cylinder should not be less than 350mm.
7. The reinforcement configuration of the column shall meet the following requirements:
(1) The minimum total reinforcement ratio of the longitudinal reinforcement of the column shall be adopted in accordance with Table 12-31, and the reinforcement ratio on each side shall not be less than 0.2%; for high-rise buildings built on Category IV sites and high, the values ​​in the table It should be increased by 0.1.
Note: When using HRB400 hot-rolled steel bars, it should be allowed to decrease by 0.1, and when the concrete strength level is higher than C60, it should be increased by 0.10.
2) When the stirrup diameter of the second-level frame column is not less than 10mm and the distance between the stirrup legs is not more than 200mm, the maximum distance except the column root should be 150mm; when the cross-sectional size of the third-level frame column is not more than 400mm, the minimum diameter of the stirrup 6mm should be allowed; when the shear span ratio of the four-stage frame column is not greater than 2, the stirrup diameter should not be less than 8mm.
3) The frame pillar and the column with a shear span ratio of not more than 2 should not exceed 100mm.
8. The longitudinal reinforcement configuration of the column should still meet the following requirements:
(1) It should be symmetrically arranged.
(2) For columns with a cross-sectional size greater than 400mm, the longitudinal reinforcement spacing should not be greater than 200mm.
(3) The total reinforcement ratio of the column should not be greater than 5%.
(4) For columns with a first-level and a shear span ratio not greater than 2, the longitudinal reinforcement ratio on each side should not be greater than 1.2%.
(5) When the side columns, corner columns, and end columns of the seismic wall produce a small eccentric tension in the combination of seismic action, the total cross-sectional area of ​​the longitudinal reinforcement in the column should be increased by 25% compared with the calculated value.
(6) The binding joint of the longitudinal reinforcement of the column should avoid the stirrup encryption area at the end of the column.
9. The stirrup encryption range of the column shall be adopted as follows:
(1) At the end of the column, take the cross-sectional height (cylinder diameter) and the maximum value of 1/6 and 500mm of the column height.
(2) The bottom column, the column root is not less than 1/3 of the column height; when there is rigid ground, besides the end of the column, the rigid ground should be taken 500mm above and below.
(3) Columns with a shear-span ratio no greater than 2 and columns with a ratio of the net height of the column formed by the installation of infill walls to the column section height of no greater than 4 shall be taken to be the full height.
(4) Frame pillar, take full height.
(5) The corner posts of the first and second frames are taken at full height.
11. The stirrup leg distance in the column stirrup encryption area should not be greater than 200mm for the first level, 250mm and the larger value of 20 times the stirrup diameter for the second and third levels, and not greater than 300mm for the fourth level. There is a stirrup or tie bar constraint in both directions; when a tie bar composite hoop is used, the tie bar should be close to the longitudinal reinforcement and hook the stirrup.
12. Volume hoop ratio of column stirrup encryption area,
Note: â‘ Common hoop refers to a single rectangular hoop and a single circular hoop; composite hoop refers to a hoop composed of rectangular, polygonal, circular hoop or tie bars; composite spiral hoop refers to a spiral hoop and rectangular, polygonal, circular hoop or Stirrups composed of tie bars; continuous composite rectangular spiral hoop refers to stirrups made of all spiral hoop made of the same steel bar;
â‘¡Composite spiral hoop or cross-shaped composite hoop should be used for the frame pillar, the minimum characteristic value of the coupling should be increased by 0.02 than the value in the table, and the volume coupling should not be less than 1.5%;
â‘¢ For columns with a shear span ratio of not more than 2, composite spiral hoops or cross-shaped composite hoops should be used. The volume matching ratio should not be less than 1.2%, and should not be less than 1.5% at 9 degrees;
When calculating the volume matching rate of the composite spiral hoop, the volume of the non-spiral hoop stirrup should be multiplied by a conversion factor of 0.8.
13. The volume hoop ratio of the non-encrypted area of ​​the column stirrups should not be less than 50% of the encrypted area; the stirrup spacing, the first and second frame columns should not be greater than 10 times the longitudinal reinforcement diameter, and the third and fourth frame columns should not be greater than 15 Double the longitudinal reinforcement diameter.
14. The maximum spacing and minimum diameter of the stirrups in the core area of ​​the frame node should be adopted according to 6.3.8 of this chapter. The hoop ratio should not be less than 0.6%, 0.5% and 0.4%, respectively. The characteristic value of the coupling in the core area of ​​the frame node with the column shear span ratio not greater than 2 should not be less than the characteristic value of the larger coupling at the upper and lower column ends of the core area.
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