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Technical standard for steel bar binding of cast-in-place frame structure

range

This technology standard is applicable to the steel binding engineering of cast-in-place frame and frame-shear wall structure of multi-storey industrial and civil buildings.

Construction preparation work

2. 1 Materials and main machines:

2. 1. 1 steel bar: It shall have the factory certificate and the mechanical properties shall be rechecked as required. When special circumstances such as brittle fracture occur during processing, it is necessary to carry out chemical composition inspection. Steel bars shall be free of old rust and oil stain.

2. 1.2 formed steel bar: it must conform to the specification, size, shape and quantity of the ingredient list, and have the factory certificate of processing.

2. 1.3 iron wire: No.20 ~ No.22 iron wire (burning wire) or galvanized iron wire (lead wire) can be used. The cutting length of iron wire should meet the use requirements.

2. 1.4 cushion block: made of cement mortar, 50mm square, with the same thickness as the protective layer, with 20 ~ 22 fire wires embedded in the fault block. Or use plastic cards, braces, and support rods.

2. 1.5 main machines and tools: steel hook, crowbar, wrench, binding frame, wire brush, trolley, chalk, ruler, etc.

2.2 Operating conditions:

2.2. 1 After the reinforcement enters the site, the factory certificate and the second interview report shall be checked, and the stow-wood shall be stacked separately according to the position, specification, use position and quantity specified in the construction plan.

2.2.2 Before steel bar binding, check whether there is corrosion, and transport it to the binding site after derusting.

2.2.3 Be familiar with the drawings, and check whether the specifications, shapes and quantities of processed steel bars are correct according to the design requirements.

2.2.4 Do a good job of copying and setting out, play the horizontal elevation line, and play the column and wall dimension line.

2.2.5 According to the played skin dimension line, check the position, quantity and length of the lower reserved lap reinforcement. If they don't meet the requirements, they should be treated. Before binding, straighten out the overlapping reinforcement extending from the lower layer, and remove dirt such as rust and cement mortar.

2.2.6 According to the elevation, check whether the elevation of the concrete surface (column top and wall top) where the lower layer extends out of the overlapping reinforcement meets the requirements of the drawings. If there are any loose or false places, remove them and clean them up.

2.2.7 After the template is installed, it shall be inspected and sundries in the template shall be cleaned.

2.2.8 Scaffolding shall be erected as required.

2.2.9 According to the requirements of design drawings and process standards, make technical disclosure to the team.

operative technique

3. 1 Binding column reinforcement:

3. 1. 1 process flow:

Set of column stirrups → lap and bind vertical reinforced bars → draw stirrup spacing lines → bind stirrups.

3. 1.2 set of column stirrups: calculate the number of stirrups for each column according to the spacing required by the drawings. First, put the stirrup on the lap reinforcement protruding from the lower layer, and then tie the column reinforcement at least three times within the lap length and tie it in the center of the column. When the main reinforcement of the column is overlapped with round steel, the hook at the corner should be 45 with the template, and the hook at the middle reinforcement should be 90 with the template.

3. 1.3 lap-binding vertical reinforced bar: after the main reinforcement of column is erected, the lap length of binding joint should meet the design requirements. If there is no design requirement, it shall be adopted according to Table 4- 10.

Lap length of binding joint of tensile reinforcement

Table 4- 10

Concrete strength grade

C20 C25 C30

1Ⅰ grade steel bar 35d, 35d 30d 25d

2 Ⅱ reinforcement (crescent) 45d 40d 35d

3 Ⅲ steel bar (crescent) 55d 50d 45d

Note: 1. When the primary and secondary reinforcement is d >; 25mm, lap length should be increased by 5d according to the values in the table.

2. When the diameter of the threaded steel bar is less than or equal to ≤25mm, the lap length of the tensile steel bar shall be reduced by 5d according to the values in the table.

3. In any case, the lap length shall not be less than 300mm. The positions of binding joints shall be staggered. From the center of any binding joint to the section with overlapping length of 1.3 times, the percentage of the cross-sectional area of steel bar with binding joint to the total cross-sectional area of steel bar: the tensile area shall not exceed 25%; The compression zone shall not exceed 50%. When welded joints are used, from the center of any welded joint to the section with the length of 35 times the diameter of steel bar and not less than 500mm, the area of welded steel bar accounts for the percentage of the total area of steel bar: the tensile area should not exceed 50%; The compression zone is not limited.

3. 1.4 Draw stirrup spacing line: Draw stirrup spacing line with chalk on the vertical bar of the column that has been erected.

3. 1.5 column stirrup binding

3. 1.5. 1 Move this group of stirrups up according to the position line of stirrups, tie them from top to bottom, and tie them with buckles, as shown in Figure 4- 19.

3. 1.5.2 Stirrup and main reinforcement should be vertical, the intersection of stirrup corner and main reinforcement should be bound, and the intersection of main reinforcement and non-corner part of stirrup should be bound into plum blossom shape.

3. 1.5.3 Hook joints of stirrups are staggered along the vertical steel bars of the column, and they are firmly bound, as shown in Figure 4-20.

3. 1.5.4 In areas with seismic requirements, the stirrup end of the column should be bent into 135, and the length of the straight part should not be less than 10d(d is the stirrup diameter). When the stirrup lap is 90, the lap joint shall be welded, and the length of the welded joint shall not be less than 5d.

3. 1.5.5 stirrups at the upper and lower ends of the column should be encrypted, and the length and spacing of stirrups in the encrypted area should meet the requirements of design drawings. If the design requires stirrups to be provided with lacing bars, the lacing bars should be hooked on the stirrups.

3. 1.5.6 The protective layer thickness of column rebar should meet the specification requirements. The outer skin of main reinforcement is 25mm, and the pad should be tied to the outer skin of column vertical reinforcement, and the spacing is generally 1000mm (or plastic card is used on the outer vertical reinforcement) to ensure the accuracy of the protective layer thickness of main reinforcement. When the column section size changes, the column should be bent in the plate, and the bending size should meet the design requirements.

3.2 binding shear wall reinforcement:

3.2. 1 process flow:

Set up 2 ~ 4 vertical poles → draw the distance of transverse barrier → tie a crossbar → tie the rest of the crossbar → tie the rest of the crossbar.

3.2.2 Erecting 2-4 vertical bars: tie the vertical bars with overlapping bars protruding from the lower layer, draw horizontal bar grading marks on the vertical bars, tie two horizontal bars at the lower part and chest level for positioning, draw vertical bar grading marks on the horizontal bars, then tie the remaining vertical bars, and finally tie the remaining horizontal bars. Transverse reinforcement should meet the design requirements on the inside or outside of vertical reinforcement.

3.2.3 Three horizontal steel bars shall be bound at the lap joint of vertical steel bars and extended lap steel bars, and the lap length and position shall meet the design requirements. If there is no requirement in the design, the construction shall be carried out according to Table 4- 1 1.

Concrete strength grade

C20 C25 C30

1Ⅰ grade steel bar 35d, 35d 30d 25d

2 Ⅱ reinforcement (crescent) 45d 40d 35d

3 Ⅲ steel bar (crescent) 55d 50d 45d

3.2.4 Shear wall reinforcement shall be bound point by point, lacing bars or supporting bars shall be bound between double rows of reinforcement, and the vertical and horizontal spacing shall not be greater than 600mm, and the steel sheath shall be bound with pads or plastic cards.

3.2.5 At the joint of shear wall and frame column, the horizontal and transverse reinforcement of shear wall should be anchored in the frame column, and the anchoring length should meet the design requirements. For example, when pouring column concrete first, and then tying bracing wall reinforcement, it is necessary to reserve connecting reinforcement in the column or embed iron pieces in the column as the connection when dismantling column and tying wall reinforcement. Its reserved length should comply with the provisions of the design or specification.

3.2.6 Anchorage length of horizontal reinforcement of shear wall at both ends, corners, cross joints and coupling beams, and reinforcement around the hole shall meet the design seismic requirements.

3.2.7 After mold closing, the protruding vertical reinforcement shall be trimmed, and a transverse reinforcement shall be tied at the lap joint for positioning. When pouring concrete, there should be special personnel to take care of it, and it should be adjusted again after pouring to ensure the accurate position of steel bars.

3.3 beam steel binding:

3.3. 1 process flow:

In-mold binding: draw the stirrup spacing between the primary and secondary beams → put the stirrup on the secondary beam of the main beam → pass through the longitudinal bar at the bottom of the main beam and bend the steel bar → pass through the longitudinal bar at the bottom of the secondary beam and fix it with stirrups → pass through the longitudinal bar at the top of the main beam and erect stirrups → bind according to the stirrup spacing → pass through the longitudinal bar at the top of the secondary beam and bind according to the stirrup spacing.

Binding outside the mould (binding and forming at the top of beam formwork before entering the mould);

Draw hoop plate spacing → spread a few steel bars at the top of the primary and secondary beam formwork → set stirrups on the steel bars → wear longitudinal bars under the main beam → wear longitudinal bars under the secondary beam → bind according to stirrup spacing → wear longitudinal bars on the secondary beam → bind according to stirrup spacing.

3.3.2 Draw the stirrup spacing on the beam side formwork and place the stirrup.

3.3.3 First pass through the longitudinal stressed steel bars and bent steel bars at the lower part of the main girder, and separate the stirrups one by one according to the drawn spacing; Wear the longitudinal stressed steel bars and bent steel bars at the lower part of the secondary beam, and set stirrups; Put the scissors of primary and secondary beams; Tie up the installation stud and stirrup at regular intervals; Adjust the stirrup spacing, make the spacing meet the design requirements, tie the stud, then tie the main reinforcement, and coordinate the primary and secondary beams at the same time.

3.3.4 The upper longitudinal reinforcement of the frame beam should run through the middle node, and the anchorage length of the lower longitudinal reinforcement of the beam should meet the design requirements. The anchorage length of longitudinal reinforcement in end nodes of frame beams should also meet the design requirements.

3.3.5 Tie the stirrups of the upper longitudinal bars of the beam with the method of set buckle.

3.3.6 Stirrup hooks at the lap joint shall be staggered and bound in the beam. The stirrup hook is 135, and the length of the straight part is 10d. If the closed hoop is made, the length of one-sided weld is 5d.

3.3.7 The first stirrup at the beam end should be set 50mm away from the edge of column node. The stirrup at the joint of beam end and column should be encrypted, and its spacing and encryption zone length should meet the design requirements.

3.3.8 Place cushion blocks (or plastic cards) under the stressed steel bars of the main beam and the secondary beam to ensure the thickness of the protective layer. When the stressed steel bars are in double rows, short steel bars can be placed between the two layers of steel bars, and the row spacing of steel bars should meet the design requirements.

3.3.9 Lapping of beam reinforcement: When the diameter of the stressed reinforcement of the beam is equal to or greater than 22mm, it is appropriate to adopt welded joints, and when it is less than 22mm, it can adopt binding joints, and the lap length should comply with the regulations. The distance between the end of the lap length and the bend of the steel bar should not be less than 10 times the diameter of the steel bar. The joint should not be located at the maximum bending moment of the member. In the tension zone, the end of the binding joint of Grade I steel bar should be hooked (Grade II steel bar can't be hooked), and the lap joint should be fastened at the center and both ends. The joint positions should be staggered. When binding lap joints are used, there is a reinforced part of the joint at any part of the specified lap length.

The area accounts for the percentage of the total cross-sectional area of steel bars, and the tensile area is not more than 50%.

3.4 plate steel binding:

3.4. 1 process flow:

Clean the template → draw lines on the template → bind the reinforced bar under the plate → bind the short reinforced bar with negative bending moment.

3.4.2 Clean up the sundries on the template, draw the main reinforcement on the template with chalk, and distribute the spacing of reinforcement.

3.4.3 spacing as planned, put the main reinforcement first, and then put the distribution reinforcement. Embedded parts, electrical conduits, reserved holes, etc. Should be installed in time.

3.4.4 If there is a plate beam in the cast-in-place slab, the plate beam reinforcement shall be bound first, and then the plate reinforcement shall be placed.

3.4.5 When binding plate reinforcement, straight buckle or splayed buckle is generally adopted. Except for the intersection of two peripheral tendons, other points can be bound alternately (all intersections of two-way slabs must be bound). If the floor is a double-layer reinforced bar, a reinforced horse stool should be added between the two layers of reinforced bars to ensure the position of the upper reinforcement. Each intersection of negative moment reinforcement shall be bound.

3.4.6 The mortar pad is placed under the steel bar with the spacing of 1.5m, and the thickness of the pad is equal to the thickness of the protective layer, which should meet the design requirements. When there is no requirement in the design, the thickness of the protective layer of the plate should be 15mm, and the requirements for the lap length and lap position of steel bars are the same as those of the beam mentioned above.

3.5 Stair steel binding:

3.5. 1 process flow: draw position line → tie main reinforcement → tie distribution reinforcement → tie step reinforcement.

3.5.2 Draw the position lines of main reinforcement and distribution reinforcement on the stair board.

3.5.3 According to the direction of main reinforcement and distribution reinforcement in the design drawings, tie the main reinforcement first and then the distribution reinforcement, and tie each intersection. If there is a stair beam, tie the beam first, and then tie the slab reinforcement. Plate reinforcement should be anchored in the beam.

3.5.4 After the bottom plate reinforcement assembling is completed, the step reinforcement shall be assembled after the step template is hoisted. The number and location of main reinforcement joints shall comply with the provisions of construction specifications.

quality standard

4. 1 guarantee project:

4. 1. 1 The variety and quality of reinforcement must meet the design requirements and the provisions of relevant standards.

4. 1.2 The surface of steel bar must be clean. After derusting, it is forbidden to use the reinforcement with granular or flaky old rust and pockmarks according to the original specifications. Steel surface should be kept clean.

4.l.3 The specification, shape, size, quantity, anchorage length and joint position of reinforcement must meet the design requirements and construction specifications.

4. 1.4 The mechanical properties of welded joints of steel bars must meet the special requirements for welding and acceptance of steel bars.

4.2 Basic items:

4.2. 1 The number of missing and loose buckles does not exceed 10% of the number of buckles, so it will not be collected.

4.2.2 Hook orientation should be correct, binding joints should comply with the provisions of construction specifications, and the lap length should not be less than the specified value.

4.2.3 The spacing quantity of stirrups should meet the design requirements. When the seismic requirements are met, the hook angle is 135, and the straight line length of the hook is 10d.

4.2.4 Butt-welded joints of rebar, Ⅰ, Ⅱ and Ⅲ rebar shall be free from burns and transverse cracks, and the welding package shall be uniform. The bending of the welded joint is not more than 4, and the deviation of the steel bar axis at the welded joint is not more than 0. 1d and not more than 2nm.

4.3 See Table 4- 12 for allowable deviation items.

Finished product protection

5. 1 After the column reinforcement is bound, it is not allowed to be trampled.

5.2 After the bent steel bar of the floor is tied with the negative bending moment steel bar, it is not allowed to walk on it. When pouring concrete, assign a steel reinforcement worker to repair it, so as to ensure the correctness of the negative bending moment steel bar position.

5.3 When binding steel bars, it is forbidden to touch embedded parts and hole templates.

5.4 When applying isolation agent on the inner surface of steel formwork, don't pollute the steel bar.

5.5 When installing electric conduits, heating pipes or other facilities, steel bars shall not be cut and moved arbitrarily.

Quality problems that should be paid attention to

6. 1 Before pouring concrete, check whether the rebar position is correct, prevent rebar from touching when vibrating concrete, and immediately trim rebar position after pouring concrete to prevent column rebar and wall rebar from shifting.

6.2 The size of the beam steel skeleton is smaller than the design size: stirrups should be calculated according to the size of the endothelium.

Table 4- 12 Allowable deviation of steel bar binding of cast-in-place frame

Inspection method of allowable deviation (mm) of the project

Check the length and width of 1 net multiplied by 10 foot.

2. The mesh size of continuous third gear is 20 feet, and the maximum value is taken.

3 The width and height of the skeleton are 5.

4 skeleton length 10

5 spacing 10

6 row spacing 5

7. The spacing between the tie stirrups and the structural steel bars for the third consecutive gear is 20 feet, which is the maximum.

8 rebar bending starting point displacement 20

Center line displacement 5

Level difference +3 -0 feet quantity inspection

Beam and Column +/-5

Wall panel 3

6.3 The stirrups in the core areas of beams and columns should be encrypted and familiar with the construction drawings as required.

6.4 The end of stirrup shall be bent into 135, and the length of straight part shall be 10d.

6.5 The length of the main beam reinforcement extending into the bearing should meet the design requirements, and the position of the bent reinforcement should be accurate.

6.6 The position of bent steel bars and negative bending moment steel bars of the slab shall be accurate, and they shall not be trampled during construction.

6.7 When binding plate reinforcement, draw lines with a ruler. When binding, look straight at any time to prevent the plate reinforcement from being straight and dislocated.

6.8 When binding the vertical reinforced bar, it should be hung upright, and three buckles should be tied at the lap joint, not in the same direction as the straight buckle. When the storey height is more than 4m, erection and binding shall be carried out, and measures shall be taken to fix the reinforcement to prevent the column and wall reinforcement skeleton from being vertical.

6.9 ingredients should be paid attention to when processing steel bars. When there is a butt joint at the end, avoid the overlapping range to prevent the butt joint from mixing into the binding joint.