Design and construction will gradually shift to the steel bar industry.
Civil workers will lose their jobs if they don't understand steel bars.
Therefore, the tender editor Bian Xiao compiled this comprehensive reinforcement summary.
Zero-based learning reinforcement technology
A, steel overview
Reinforcement type
Reinforcement types of building structure reinforcement engineering
For the reinforcement project of building structure, it can be divided into the overall seismic reinforcement of building structure (that is, system reinforcement) and component reinforcement. System reinforcement is aimed at the deficiency of the overall seismic performance of building structures in the current seismic appraisal standards; Component reinforcement is to reinforce local components in view of their insufficient bearing capacity.
Strengthening principle
The design principles for seismic strengthening of existing buildings shall meet the following requirements:
1. The reinforcement scheme shall be determined according to the comprehensive analysis of the seismic appraisal results, and the whole building reinforcement, sectional reinforcement or component reinforcement shall be adopted respectively to strengthen the integrity, improve the stress condition of components and improve the comprehensive seismic capacity;
2, the layout of reinforcement or new components, should eliminate or reduce the unfavorable factors, prevent local reinforcement lead to structural stiffness or strength mutation;
3. There should be a reliable connection between the new parts and the original parts; New vertical members such as seismic walls and columns should have reliable foundations;
4. When the material used for reinforcement is the same as the original structure, its strength grade should not be lower than the actual strength grade of the original structure material;
5, reinforcement design should pay attention to the joint connection structure design.
Contents and methods of strengthening
security reinforcement
Masonry structure reinforcement
Measures such as strengthening, partially replacing or adjusting the internal force of masonry structures and related parts that are not reliable or required by the owner are taken to make them have the safety, durability and applicability required by the current design code and the owner.
When the seismic bearing capacity is not satisfied, appropriate reinforcement methods should be adopted.
1) Remove masonry or add seismic wall.
2) Repair and grouting
3) surface or plate wall reinforcement
4) reinforce with additional columns
5) corner wrapping or edge wrapping reinforcement
6) Support or bracket reinforcement
When the integrity is not satisfied, the reinforcement method should be adopted.
1) When the wall is not closed in the plane, it can be closed by adding wall segments or adding cast-in-place reinforced concrete frames at the mouth of the cave.
2) When the vertical and horizontal strong connection is poor, steel tie rod, long anchor rod, outer column and outer ring beam can be used for reinforcement.
3) When the supporting length of the building and roof components does not meet the requirements, joists can be added or measures to enhance the integrity of the building and roof can be taken; Corroded and deteriorated parts should be replaced; A bottom chord tie rod should be added to the herringbone roof truss without bottom chord.
4) When the setting of constructional column or core column does not meet the appraisal requirements, additional columns should be added; When the wall is reinforced with double-sided steel mesh mortar surface layer or reinforced concrete slab wall, and reinforced belts which are reliably bound with each other are added at the junction of the wall, additional constructional columns are not required.
5) When the ring beam setting does not meet the appraisal requirements, ring beams should be added; The outer wall ring beam should be cast-in-situ reinforced concrete, and the inner wall ring beam can be replaced by steel tie rods or anchor rods at the deep end; When double-sided steel mesh mortar surface layer or reinforced concrete slab wall is used for reinforcement, and reinforcement belts are added at the upper and lower ends, ring beams are not required.
6) When prefabricated buildings and houses do not meet the requirements of seismic appraisal, reinforced concrete cast-in-place layers or joists can be added to reinforce the buildings and roofs.
Weak and easy to fall parts, adopt appropriate reinforcement methods.
1) when the width of the wall between windows is too small or the seismic capacity does not meet the requirements, reinforced concrete window frames can be added or reinforced with reinforced mortar surface and slab walls.
2) When the seismic capacity of the wall section of the supporting beam does not meet the requirements, masonry columns, composite columns and reinforced concrete columns can be added, or reinforcement can be carried out by methods such as mortar surface layer with steel mesh and slab wall.
3) When the wall supporting the cantilever member does not meet the appraisal requirements, reinforced concrete columns or masonry composite columns should be added at the end of the cantilever member for reinforcement.
4) If there is no Rachel or the Rachel is not firm, the partition wall can be strengthened by wrapping, embedding steel sheath, anchor bar or steel tie rod; When the partition wall is too long and too high, it can be reinforced with steel mesh mortar surface.
5) When the stairwell, elevator room and water tank room out of the roof do not meet the appraisal requirements, the surface layer or additional column can be used for reinforcement, and the upper part should be reliably connected with the roof components, and the lower part should be connected with the reinforcement measures of the main structure.
6) When chimneys, parapets without Rachel, gables, etc. If the height exceeds the specified height, it should be removed, lowered or reinforced with section steel and steel tie rods.
7) When the anchorage length of the cantilever member does not meet the requirements, the pull rod can be increased or the cantilever length can be reduced.
Strengthening of reinforced concrete structure
When the structural system and seismic bearing capacity of reinforced concrete buildings do not meet the requirements, the following reinforcement methods should be adopted:
1) One-way frame should be strengthened, or changed to two-way frame, or measures should be taken to strengthen the integrity of buildings and roofs, and at the same time, anti-lateral force components such as seismic walls and seismic supports should be added.
2) If the single-span frame does not meet the appraisal requirements, the lateral force resisting members such as seismic wall, wing wall and seismic support should be added within the range greater than the maximum spacing between the frame and seismic wall structure and not greater than 24m, or the single-span frame with corresponding axis should be changed into multi-span frame.
3) When the reinforcement or bearing capacity of frame beams and columns can't meet the appraisal requirements, reinforcement methods such as wrapping steel, increasing cross section, sticking steel plates or sticking carbon fiber sheets can be adopted.
4) When the axial compression ratio of the frame column does not meet the appraisal requirements, the method of increasing the cross section can be adopted for reinforcement.
5) When the stiffness of the building is weak, obviously uneven or has obvious torsion effect, the reinforced concrete seismic wall or wing wall can be reinforced, and the support can also be set for reinforcement.
6) When the reinforcement of the reinforced concrete seismic wall does not meet the appraisal requirements, the original wall can be thickened or end columns and walls can be added.
7) When the stair component does not meet the appraisal requirements, it can be strengthened by pasting steel plate, carbon fiber cloth or enlarging the cross section.
Member reinforcement
Foundation reinforcement
Increase the area of the bottom of the foundation
Scope of application: the method of increasing the bottom area of foundation is suitable for strengthening when the bearing capacity of foundation or the bottom area of existing building foundation does not meet the design requirements.
Schematic diagram of increasing the area of foundation bottom
Structural requirements:
A, when the foundation is eccentrically compressed, asymmetric widening can be adopted; Symmetrical widening can be used when the center is compressed;
B, before pouring concrete, the original foundation should be chiseled and scrubbed clean, and then a layer of high-strength cement slurry or concrete interface agent should be laid to increase the cohesive force of new and old concrete foundations;
C, widening part of the main reinforcement should be welded with the main reinforcement in the original foundation, and set the Rachel reinforcement arranged in plum blossom (if shear reinforcement is needed, it should be determined according to calculation).
Deepening foundation method
Scope of application: the deepening foundation method is suitable for shallow foundation with good soil layer as bearing layer and low groundwater level. This method is to deepen the buried depth of the original foundation, so that the foundation can be supported on a better bearing layer to meet the design requirements for the bearing capacity and deformation of the foundation.
Structural requirements:
A, strengthening the foundation of existing buildings by deepening the foundation method should be carried out in batches, sections and intervals. Excavate vertical pits with a length of about 1.2m and a width of about 0.9m at intervals;
B, vertical pit under the foundation should be cast-in-situ concrete, 80mm from the bottom of the original foundation to stop pouring. After a day's curing, dry thick cement mortar mixed with expansion agent and accelerator should be filled in the cracks of the basement to ensure the compactness.
Anchor static pressure pile
Scope of application: Anchor static pressure pile method is suitable for silt, muddy soil, cohesive soil, silt, artificial fill and other foundation soil.
Schematic diagram of working principle of anchor static pressure pile
Requirements of original foundation structure: In addition to the relevant bearing capacity requirements, the original foundation cap shall also meet the following requirements:
The clear distance from the periphery of the pile cap to the side pile should not be less than 200mm；; The pile hole thickness of the original foundation as the foundation of the bearing platform should not be less than 350mm, otherwise additional pile sealing and anchoring measures should be taken; The length of the pile top buried in the cap should be 50 ~100 mm; C30 micro-expansive early strength concrete is used to tamp the pile hole.
The strength grade of pile concrete should not be lower than C30；; When the thickness of the original foundation is less than 350mm, the hole sealing of the pile should be cross-welded with the 2φ 16 steel bar on the anchor rod. At the same time, the pile top should be poured above the top surface of the pile hole with a thickness of not less than150 mm. ..
Pile structure requirements:
The pile body material can be reinforced concrete or steel; Reinforced concrete piles should be square, and the side length of the pile should be 200 ~ 300mm；; The strength grade of pile concrete should not be lower than C30；; The main reinforcement in the pile should be determined by calculation.
When the side length of the square pile section is 200mm, the reinforcement should not be less than 4 φ10; When the side length is 250mm, the reinforcement should not be less than 4 φ12; When the side length is 300mm, the reinforcement should not be less than 4 φ16; The length of each pile section should be 1.0 ~ 2.5m, and the pile sections should be reliably connected by welding.
Structural requirements of anchor rod: the anchor rod can adopt smooth straight heading bolt or welded hoop bolt, and shall meet the following requirements:
When the pile pressing force is less than 400kN, M24 anchor can be used; M27 anchor can be used when the pile pressing force is 400~500kN; The anchoring depth of the anchor bolt can be 10~ 12 times of the bolt diameter, and should not be less than 300mm. The length of the anchor rod exposed from the top surface of the pile cap should meet the requirements of the pile driver, generally not less than120mm. ; The distance between anchor rod and pile hole, surrounding structure and the edge of pile cap should not be less than 200mm.
Brick wall reinforcement
Reinforcement method of cement mortar surface layer with steel mesh
Scope of application: the reinforcement of cement mortar with steel mesh is a reinforcement method that adds a layer of steel mesh, a layer of steel mesh or a layer of welded steel mesh to the surface mortar to improve the bearing capacity and ductility of the wall. Its advantages are that the out-of-plane bending stiffness is greatly improved, the in-plane shear strength and ductility are greatly improved, and the crack resistance of the tower is greatly improved. This method is suitable for static reinforcement and seismic reinforcement with medium and high intensity.
Schematic diagram of strengthening brick wall with steel wire mesh cement mortar surface layer
Structural requirements: when the foundation bears eccentric compression, asymmetric widening can be adopted; Symmetrical widening can be used when the center is compressed; Before pouring concrete, the original foundation should be chiseled and scrubbed clean, and then a layer of high-strength cement slurry or concrete interface agent should be laid to increase the cohesive force of new and old concrete foundations. The main reinforcement of the widened part should be welded with the main reinforcement in the original foundation, and the Rachel reinforcement with plum blossom arrangement should be set (if shear reinforcement is needed, it should be determined according to calculation).
Second, the concrete column reinforcement method and matters needing attention
Application of the method
Concrete reinforcement method
1
Strengthening method with enlarged section
application area
The method of increasing the section reinforcement, that is, increasing the reinforcement of the original member and re-pouring concrete on the outside to increase the section size of the member, can achieve the purpose of improving the bearing capacity. Its advantages are that it can increase the stiffness, bearing capacity and deformation capacity of the member at the same time, and in some cases, it can also strengthen the reliability of the connection; Its disadvantages are heavy workload of wet operation, long maintenance period and much building space. The schematic diagram of strengthening concrete columns with enlarged section is shown in the following figure.
Schematic diagram of strengthening concrete columns by enlarging cross-section reinforcement method
Structural requirements
A, component concrete strength grade should not be lower than c13; ;
B, the new part, can use cast-in-place concrete, self-compacting concrete or shotcrete pouring. It can also be made of cement-based grouting material mixed with fine stone concrete.
C, new concrete thickness requirements: manual pouring: ≥ 60 mm; Spray: ≥ 50 mm
D. When the reinforcement method of increasing the cross section is adopted, the concrete surface of the original member should be treated, and the design documents should put forward requirements for the treatment method and quality of the cross section. In general, in addition to roughening the concrete surface, measures such as coating structural interface glue, planting shear studs or adding shear keys should also be taken.
E, column reinforcement diameter should not be less than 14mm, anchorage stirrup diameter should not be less than 8 mm; The diameter of the U-shaped hoop should be the same as that of the original hoop; The diameter of distributed reinforcement shall not be less than 6mm.
Speak from experience
A, four sides to increase the cross section to strengthen the concrete column, be sure to ensure that the new stirrup is closed.
B, when using unilateral, bilateral or trilateral cross-section to strengthen concrete columns, if the new stirrups can't be closed, the new stirrups can be welded with the original stirrups to achieve the closed effect.
2
External steel plate reinforcement method
application area
According to the connection mode with the original structure, the reinforcement methods of external bonding steel can be divided into external bonding steel reinforcement method and external bonding steel reinforcement method. Both of them are suitable for the reinforcement of reinforced concrete columns that need to greatly improve the cross-sectional bearing capacity and seismic capacity. The schematic diagram of concrete columns strengthened with steel-clad steel is shown in the following figure.
Schematic diagram of strengthening concrete columns by wrapping steel bars
Structural requirements
A, reinforced angle steel should not be less than l75× 5;
B, flat steel hoop plate or batten plate should not be less than 40mm×4mm, spacing should not be greater than 20r(r is the minimum radius of gyration of a single angle steel section), and should not be greater than 500mm；; In the node area, the spacing should be properly encrypted.
C, both ends of the outsourcing angle steel should be reliably connected and anchored. The lower end of angle steel should be anchored on the foundation, the middle should pass through each floor, and the upper end should extend to the upper floor of the reinforcement layer or the bottom of the roof panel.
D, outsourcing steel reinforcement column, the edges and corners of the original component section should be polished into rounded corners with a radius r greater than or equal to 7 mm .. Glue injection for external bonding steel should be carried out after the steel frame is welded.
E, the thickness of external steel glue joint should be controlled within 3 mm ~ 5 mm; Glue joints with a length of not more than 300mm and a thickness of not more than 8mm are allowed locally, but they shall not appear within 600mm of the end of angle steel.
Speak from experience
A, the new angle steel along the column height must be fully penetrated. When the angle steel can't pass through the floor beam, it can be welded with the reinforcing angle steel of the upper and lower layers by using the equivalent reinforcement passing through the floor;
B, in the beam-column joint position, when the flat steel can't pass through the concrete beam, it can also be reinforced by welding the equivalent steel bar between the concrete beam and the left and right steel angles;
C, for the bottom column rebar, the end of the rebar angle must be anchored at the top surface of the original structural foundation, and for the rebar angle part buried in the foundation soil, concrete enclosure shall be poured for antirust treatment, as shown in section 3-3 above;
D, if there are any special requirements, after the concrete column is reinforced with steel bars, it still needs fire prevention treatment. In view of the fact that there is no relevant code requirement in China at present, the usual practice is the same as that of steel structure fire prevention, such as brushing thin or thick fire retardant paint.
three
Strengthening method of circumferential closed hoop bonded with carbon fiber cloth
application area
It is suitable for the reinforcement of reinforced concrete columns that need to improve the shear bearing capacity of section and the overall ductility of components.
Structural requirements
A, reinforced concrete structural members, the field measured concrete strength grade shall not be lower than C 15, and the tensile bond strength of concrete surface shall not be lower than1.5 MPa; ;
B, carbon fiber cloth composites pasted on the surface of concrete members shall not be directly exposed to sunlight or harmful media, and their surfaces shall be protected.
C, the concrete structure reinforced by this method, its long-term use of environmental temperature should not be higher than 60℃.
Speak from experience
A, when necessary, carbon fiber sheets and supporting resin bonding materials can be sampled and inspected on site.
B, the actual pasting area of carbon fiber sheet should not be less than the design quantity, and the position deviation should not be greater than 65438+/-00 mm. ..
C, the bonding quality between carbon fiber cloth and concrete can be checked by tapping with a small hammer or pressing the surface of carbon fiber cloth by hand, and the total effective bonding area should not be less than 95%.
Three, concrete beam reinforcement methods and matters needing attention
Application of the method
Concrete reinforcement method
1
Strengthening method of sticking carbon fiber cloth outside
Structural requirements
A, component concrete strength grade should not be lower than c15; ;
B, normal section bending bearing capacity should not be increased by more than 40%;
C. the reinforcement of fiber composite materials: the precast slab should not exceed 2 layers; Fiber cloth should not exceed 4 layers.
Speak from experience
A, the problem of paste extension length. For the bending steel bar at the bottom of the beam, when the sticking length of carbon fiber sheet is not satisfied, additional anchorage forms can be adopted, such as U-shaped hoop reinforced at the end; For the bending steel bar of beam support, when the sticking extension length is not satisfied, the end anchorage can be carried out in the form of steel plate strip+nail. See article 10.2.5 of Code for Design of Reinforcement of Concrete Structures (GB50367-20 13) for the determination of sticking extension length.
B, sticking carbon fiber cloth and sticking steel plate meet. The beam support is strengthened by bending. If the other direction is reinforced with bonded steel plates, carbon fiber cloth should be placed on the lower steel plates.
C, fire prevention. Because carbon fiber cloth is bonded and reinforced, its materials include binder and carbon fiber cloth, and the ambient temperature of binder should not be higher than 60℃. Therefore, when this method is used to strengthen concrete structures in high temperature environment, corresponding protective measures should be taken. At present, there is no relevant specification in China, and the usual practice is to plaster with cement mortar.
2
U-shaped hoop bonded with carbon fiber cloth
Structural requirements
A, component concrete strength grade should not be lower than c15; ;
B, the width of the U-shaped hoop: the end hoop should be ≥ 2/3 of the width of the carbon fiber cloth at the bottom of the beam and ≥ 200 mm; The middle hoop should be ≥ 1/2 the width of carbon fiber cloth at the bottom of the beam, and ≥100 mm. ..
C. Shear reinforcement of U-shaped hoop: the upper end of U-shaped hoop is anchored with longitudinal battens, and when the beam height h≥600mm, longitudinal waist battens should be added at the waist of the beam.
three
Strengthening method of externally bonded steel plate
Structural requirements
A, component concrete strength grade should not be lower than c15; ;
B, normal section bending bearing capacity should not be increased by more than 40%;
C, steel plate thickness requirements: manual gluing ≤ 5 mm; Injection ≤10 mm;
D, steel plate reinforcement: tensile zone ≤3 layers; Compressive zone ≤2 layers; And that total thickness of the steel plate is less than or equal to10mm. ..
Speak from experience
When concrete beams are strengthened by bending, carbon fiber sheets are pasted outside.
four
U-shaped hoop with externally bonded steel plate
Structural requirements
A, component concrete strength grade should not be lower than c15; ;
B, anchoring U-shaped hoop: the end hoop should be ≥ 2/3 of the width of the steel plate at the bottom of the beam, and should be ≥ 80 mm; The middle hoop should be ≥ 65438+ 0/2 of the width of the steel plate at the bottom of the beam, and should be ≥ 40 mm; The thickness of the U-shaped hoop should be ≥ 65438+ 0/2 of the thickness of the steel plate at the bottom of the beam, and should be ≥ 4 mm;
C. Shear reinforcement of U-shaped hoop: the upper end of U-shaped hoop is anchored with longitudinal battens, and when the beam height h≥600mm, longitudinal waist battens should be added at the waist of the beam.
five
Externally bonded section steel
Structural requirements
A, Angle steel thickness should be 5 mm or higher, Angle steel edge should be 50 mm or higher;
B, batten plate section should be 40 mm× 4 mm or more, the spacing should be 20r or more (r is the minimum radius of gyration of single angle steel section), and ≤500mm or less.
Speak from experience
I. Selection of reinforcement scheme. Because this reinforcement method needs to pass all flat steel hoops through the original floor, this method will cause too much damage to the original floor, so this reinforcement method is generally not recommended. If this method is really needed, steel bars can be used instead of flat steel hoops to reduce the damage to the original floor.
B, the fire prevention problem is the same as the concrete column strengthened with externally bonded steel. Please refer to the reinforcement of concrete columns.
Four. Technical requirements of common reinforcement materials
1
specific
1, used for structural reinforcement of concrete, its strength grade should be higher than the original structure and components, and not lower than C20, and its performance and quality should comply with the current national standard "Code for Design of Concrete Structures" GB500 10.
2. Code for Design of Reinforced Concrete Structures (GB50367-20 13), Article 4. 1.
2
Steel and welding materials
Code for design of reinforcement of concrete structures (GB50367-20 13), article 4.2.
three
Fibers and fiber composites
1, the fiber of fiber composite material must be continuous fiber, and its variety and quality shall meet the following requirements:
(1) The carbon fiber used to strengthen the load-bearing structure should be small tow fiber with polyacrylonitrile base not exceeding 15K.
(2) It is forbidden to use the fiber fabric produced by prepreg method in the reinforcement project of load-bearing structure.
(3) The tensile strength of fiber composite materials shall meet the requirements of Article 4.3 of Code for Design of Reinforcement of Concrete Structures (GB50367-20 13).
2. For other details, see Article 4. 1 in Code for Design of Reinforcement of Concrete Structures (GB50367-20 13).
four
Adhesive for structural reinforcement
1. Adhesives for load-bearing structures should be divided into Class A adhesives and Class B adhesives according to their basic properties. For important structures, cantilever members, structures and members under dynamic action, grade A glue should be used; For general structures, grade A glue or grade B glue can be used.
2, bearing structure with adhesive, bond shear strength test must be carried out. During inspection, the standard value of bond shear strength should be determined according to the requirements of confidence level of 0.90 and guarantee rate of 95%.
3. Unsaturated polyester resin and alkyd resin are forbidden to be used as adhesives for strengthening load-bearing structures.
4. See Article 4.4 of Code for Design of Reinforcement of Concrete Structures (GB50367-20 13) for details.
Checking calculation of seismic reinforcement of verb (abbreviation of verb) system
Seismic strengthening of multi-storey masonry buildings
The comprehensive seismic capacity index after reinforcement can be used as an index to measure the seismic capacity of multi-storey masonry buildings, and the shear bearing capacity of reinforced wall sections can also be checked according to the design method.
1
Comprehensive seismic capacity index method
The comprehensive seismic capacity index of reinforced floor slab and wall section shall be checked according to the following formula:
See Article 5.116-2009 of Technical Specification for Seismic Strengthening of Buildings for the meaning of each parameter in the formula. (PS: For specifications, please reply to "rebar specifications" on the official account of WeChat).
Different from the appraisal, the corresponding reinforcement coefficient should be considered according to different reinforcement methods, and the system influence coefficient ψ 1 and local influence coefficient ψ2 should be taken according to the reinforcement situation.
1, the reinforcement coefficient of wall reinforcement of Class A and Class B masonry houses is the same. For surface reinforcement,1.1~ 3.1according to the original wall thickness, mortar strength grade, reinforcement surface and reinforcement fabric thickness; For slab wall reinforcement, according to the mortar strength grade of the original wall,1.8 ~ 2.5; For the reinforcement of the outer column, when the structural column is not needed, according to the situation of the outer column and holes, 1. 1~ 1.3 is selected.
2. The structural influence coefficient of Class A and Class B masonry houses is slightly different, mainly in the influence coefficient of constructional columns:
A, after adding the thickness of seismic wall, if the spacing between transverse walls is less than the specified value in the Appraisal Standard for Steel Core Floors, take ψ1=1.0;
B, identification does not need constructional column, after adding additional column, tie rod and ring beam, the overall connection coefficient (supporting length of building roof, arrangement and structure of ring beam, etc. ) is ψ1=1.0; When identifying the constructional column, the additional constructional column should meet the identification requirements, and the corresponding influence coefficient material can be ψ1=1;
C, using surface layer, plate wall to reinforce or add window frames and columns between windows, the influence coefficient of its local size is ψ 2 =1.0;
D, the influence coefficient of the supporting length of the main girder is ψ2= 1.0 after the surface layer, slab wall reinforcement or additional columns are adopted.
2
Testing algorithm of shear bearing capacity
After the wall is reinforced, according to the current regulations, only the wall section with large attached area or small vertical stress can be selected for checking the seismic bearing capacity, and the seismic and shear bearing capacity of this section can be checked by the following companies:
When the structural influence is not included: V≤ηVRo
When considering the structural influence: v ≤ξ ξ1ξ 2vro.
See Article 5.1/kloc-0-6-2009 of Technical Specification for Seismic Strengthening of Buildings for the meaning of each parameter in the formula.
Seismic strengthening of multi-storey and high-rise reinforced concrete buildings
When reinforced concrete buildings are strengthened under earthquake, the reinforcement scheme should be selected according to the actual situation of the building, and the schemes of mainly improving the seismic bearing capacity of structural members, mainly enhancing the structural deformation capacity or changing the frame structure system should be adopted respectively. The seismic checking calculation of reinforced buildings can adopt the same CCB method as seismic appraisal. The comprehensive seismic capacity of concrete structures should be determined according to the reinforced structural conditions, such as earthquake action, floor yield strength coefficient, system influence coefficient and local influence coefficient.
1
Grade a residence
When the comprehensive seismic capacity index of plane structure floors is used for secondary appraisal of Class A reinforced concrete buildings, the system influence coefficient and local influence coefficient shall meet the following requirements.
1, the system influence coefficient can be determined according to the structural system, beam-column stirrups, axial compression ratio and other degrees and parts that meet the first-class appraisal requirements, according to the following conditions:
A 1.4 can be adopted when the above-mentioned structure conforms to the current Shanghai standard Code for Seismic Design of Buildings DGJ08-9.
B. 1.25 is preferable when all structures meet the requirements of Class B buildings in Section 6.3 of Code for Seismic Appraisal and Reinforcement of Existing Buildings DGJ08-8 1-20 15;
C, when all structures meet the requirements of 6.2. 1~ 6.2.7 in Code for Seismic Appraisal and Reinforcement of Existing Buildings DGJ08-8 1-20 15, it is advisable to use1;
D, when all structures meet the requirements of non-seismic design, 0.8 is desirable;
E. When the structure is damaged or tilted but corrected, the above values shall be multiplied by 0.8~ 1.0.
2. According to the degree that the local structure does not meet the requirements of seismic measures in Section 6.2 of Code for Seismic Appraisal and Reinforcement of Existing Buildings (DGJ08-8 1-20 15), the minimum of the following three coefficients can be selected:
A, connected to the bearing masonry structure frame, desirable 0.8 ~ 0.95;
B when the connection between the infilled wall and the frame does not meet the requirements of seismic measures in section 6.2 of Code for Seismic Appraisal and Reinforcement of Existing Buildings DGJ08-8 1-20 15, take 0.7 ~ 0.95;
C. When the length-width ratio of the floor slab to the roof between the seismic walls exceeds the provisions of Clause 6.2. 1 5 of Code for Seismic Appraisal and Reinforcement of Existing Buildings, it can be 0.6~0.9 according to the exceeding degree.
four
Grade b house
The system influence coefficient of Class B reinforced concrete buildings can be determined according to the degree and position of structural system, beam-column stirrups, axial compression ratio, wall members, etc., which meet the appraisal requirements, according to the following conditions:
A.1.4 is acceptable when the above structure conforms to the current Shanghai standard Code for Seismic Design of Buildings DGJ08-9;
B.1can be adopted when all the structures meet the provisions in Article 6.3. 1~ 6.3.9 of Code for Seismic Appraisal and Reinforcement of Existing Buildings DGJ08-8 1-20 15;
C, when all structures meet the Code for Seismic Appraisal and Reinforcement of Existing Buildings DGJ08-8 1-20 15, the value of 0.8 is desirable;
D when the structure is damaged or tilted but has been repaired and corrected, the above values shall be multiplied by 0.8~ 1.0.
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