When the right amount of steel bars are added to concrete, it is reinforced concrete. The reason why steel bars and concrete with different physical and mechanical properties can work together effectively is mainly due to their cohesive force and coordinated deformation after loading. The following are some quality standard practices for steel bar construction. Welcome to read!
Standard practice of steel bar forming
1. Stacking and marking of formed steel bars: The formed steel bars shall be stacked in categories, and identification plates shall be set up to indicate the forming size, diameter, use position, etc. To avoid misuse.
2. Lifting rings of prefabricated members: round steel bars shall be used, and cold drawing is strictly prohibited. The depth of embedded concrete should not be less than 30 days.
3, steel substitution, must go through the design unit, there is a checklist, which is also the content of the mandatory provisions.
Second, the standard practice of foundation steel binding
1, when the bottom plate adopts double-layer steel mesh, a reinforced horse stool should be set between the two layers, and the horse stool should be placed on the lower steel mesh, and a horse stool should be placed every1m.
2. When the independent foundation is reinforced in two directions, the short-term reinforcement at the bottom should be placed on the long-term reinforcement. This joint should be knotted at three points.
3. On the basis of directly bearing dynamic load, it is not advisable to weld the joint.
Because high temperature will affect the material of steel, destroy the original impact toughness and ductility, and the fatigue performance will be greatly affected, which can not adapt to the periodic change of dynamic load and directly affect the structural safety. Therefore, high-strength bolt connection or other flexible measures should be adopted according to the situation.
4. When the diameter of foundation reinforcement is greater than 16mm, welded joints should be adopted, which is the requirement in the process standard. Some requirements in the process standard are higher than those specified in the specification.
5, the foundation slab adopts reinforced horse stool to support the upper reinforcement, so as to control the concrete thickness of the slab.
6, the standard practice of foundation beam slab steel binding:
(1) When there are bent steel bars in the beam, the distance from the joint to the starting point of bending should not be less than 10 times the diameter of the steel bar;
(2) The openings of beam stirrups should be staggered.
Standard practice for steel binding of three-sided shear walls
1, shear wall reinforcement should be bound point by point, and the binding between double rows of reinforcement should be one model larger than the vertical reinforcement of the wall, and trapezoidal positioning reinforcement should be made, with vertical and horizontal spacing not greater than 60cm.
2. Fabrication of horizontal trapezoidal ribs: The trapezoidal ribs are placed according to the mold spacing and fixed by spot welding with arc welding.
3. Initial reinforcement position of horizontal distribution reinforcement of shear wall: After the first initial reinforcement is bound from 5cm, it shall be bound according to the drawing spacing.
4.f fixture can also be used to control the width of horizontal distribution bars on both sides of shear wall.
5. Vertically distributed steel bars can be overlapped at the same height, and the overlapping length should not be less than 1.2 times of the anchorage length of longitudinal tensile steel bars.
6. When the shear wall opens a hole, edge members should be set on both sides of the hole, and the upper and lower edges of the hole should be equipped with structural longitudinal bars.
7, waterproof requirements, steel plate water stop treatment.
Standard practice for binding four-column steel bars
1, when the steel bar diameter in the column is greater than 25mm, two stirrups should be added on each side of the joint with a spacing of 5cm.
2, stirrup hook lap should be staggered along the column vertical reinforcement.
3. Angle of stirrup hook in seismic zone 135? The length of the straight part of the hook shall not be less than 10 times of the stirrup diameter.
4. Control method of column main reinforcement: place precast positioning stirrups to prevent the common quality problem that the main reinforcement is easy to displace.
5, steel plate water stop through the column processing: local broken into open stirrups for binding.
6, the location of the longitudinal reinforcement connection joint should avoid the beam end, column end encryption area, when can't avoid, should use high quality mechanical connection joint, joint area percentage should not exceed 50%.
7. The corner columns of the first and second seismic grade frame columns should all be encrypted with stirrups, that is, the spacing between each stirrup is 5cm.
8. Requirements for stirrup encryption zone of constructional column: The length of the encryption zone at the bottom column root should not be less than 1/3 of the column clear height. When there is a rigid ground, stirrups should be densified within 500mm from top to bottom of the ground.
9. Principles to be observed: If the drawing requirements are higher than the specification requirements, the construction shall be carried out according to the drawing requirements; When the drawing requirements are lower than the specifications, the construction shall be carried out according to the specifications.
Reinforcement binding of five frame beams
1, if the tension zone is the end of the round steel binding joint, it should be hooked, but the steel bar should not be hooked.
2, the joint should be staggered, in any case, the binding lap length of compression reinforcement should not be less than 20cm, and the lap length of tension reinforcement should not be less than 30cm.
3. This beam is a cantilever beam, and the main reinforcement is not in the lower part, but in the upper part, and the vertical reinforcement is in the lower part. This is right, and the cushion block is also padded, but the stirrup below is bound incorrectly, and the stirrup openings at the lower part of the beam should be staggered.
Six cast-in-place slab steel binding
1, the intersection of two steel bars at the periphery should be fully tied, and other points can be staggered.
2. The floor adopts reinforced horse stool to support the upper reinforcement, which is used to control the thickness of concrete.
Seven steel bar connections
1, tensile steel bar diameter d >；; 28mm (process standard is 22mm), and the diameter of compressed steel bar is d >；; When it is 32mm, it is not appropriate to use binding joints, but to use welding or mechanical connection, and the joints should be staggered. This is a specification requirement and an effective measure to save steel.
2. Straight thread connection of steel bar: appearance quality of processing: full tooth profile of thread head, no broken or bald tooth defect, smooth tooth surface.
3, ribbed steel radial extrusion joint connection:
(1) The two steel bars connected can have the same diameter or different diameters, but the diameter difference shall not exceed 9mm.
(2) Appearance quality: the length of the extruded casing shall be1.10 ~1.15 times of the original casing length, and the extruded casing shall not be cracked. If the indentation depth is not enough, make up the pressure; if it is too deep, remove the joint and reconnect it.
4. Electroslag pressure welding connection: the axial deviation of the joint should not be greater than 0. 1 times the diameter of the steel bar, and should not be greater than 2mm. If the appearance inspection is unqualified, it should be dismantled and welded again.
5, arc welding connection:
(1) covered electrode must have a product certificate.
(2) 2) One-side welding of HPB 235 (steel bar): 8d. Double-sided welding: 4d； One-sided welding of HRB335, HRB400 and RRB400 (round steel):? 10d, double-sided welding:? 5d .
(3) The weld thickness should not be less than 0.3 times the diameter of the main reinforcement; The weld width should not be less than 0.8 times the diameter of the main reinforcement.
(4) There shall be no sag, flash and crack, and the residual height of weld shall not be greater than 3mm.
8 reinforced protective layer control
1, the importance of reinforced protective layer
(1) A reasonable protective layer of steel bars is relatively safe. However, if the thickness of the protective layer is too small, it is easy to expose the steel bar, or the surface concrete will fall off when the steel bar is stressed, and the surface concrete will gradually carbonize. It won't be long before it loses its protective effect. Steel bars are easy to oxidize at room temperature, which will lead to corrosion of steel bars, reduction of cross section and strength, loss of bonding force between steel bars and concrete, and destruction of the integrity of reinforced concrete.
(2) The displacement of the steel bars on the upper part of the beam slab will seriously affect the bearing capacity and crack resistance of the structure, so the code stipulates that the qualified rate of the protective layer thickness of the beam slab must reach more than 90% to be qualified;
(3) In the process of construction, the position of reinforcement is always correct when binding, but it is different when pouring concrete. People step on it and tools press on it. As a result, the horse stool supporting the steel bar was trampled down, the upper steel bar was bent and deformed, and the thickness of the protective layer could not be guaranteed.
Therefore, the operation should be standardized, and finished product protection measures should be taken. It is forbidden for operators to walk on steel bars at will to prevent the above phenomenon. According to statistics, about 70% of residential floor cracks are caused by the incorrect position of reinforced protective layer, and the harm caused cannot be ignored. Therefore, we should fully realize the importance of reasonable protective layer thickness of steel bars to engineering structures.
Whether the foreman or the quality inspector, we should pay attention to whether the thickness of the mortar pad prefabricated on site is correct. Before pouring concrete, deformed steel bars must be repaired.
2, wall, plate reinforced pad:
(1) Foundation slab reinforced cushion block: precast concrete cushion block is adopted, and the thickness of reinforced protective layer under longitudinal stress is not less than 4cm, and it is not less than 7cm without cushion block.
(2) The spacing of the pads is 80cm, and they are arranged in a plum blossom shape.
3. Strengthening pad of cantilever structure
In building structures, the usual beam-slab structure is supported at both ends, either on the beam or on the wall.
Under the vertical load, a positive bending moment is generated in the beam, and the bottom of the beam or slab is in tension, so the main reinforcement in tension is arranged below. This is the most basic mechanical knowledge that your teacher said at school.
However, cantilever structure is different. Under the vertical load, the cantilever beam produces negative bending moment, and the upper side is in tension, so the main reinforcement in tension is arranged on the upper side.
If the protective layer of the upper reinforcement is too large, the bearing capacity of the cantilever part will be reduced. Everyone should know the calculation method of the protective layer of cantilever plate, which needs special attention. Then the steel stripper must calculate the lower side of the steel bar, how high the cushion block should be or how high the steel bar stool should be to ensure the correct size of the protective layer after the steel bar is bound. If you don't understand the principle, putting steel bars below will inevitably lead to quality accidents of balconies, awnings and overhangs.
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