A, steel raw materials
1. Yellow floating rust appears on the surface of steel bar, which turns red seriously, turns dark brown after a long time, and even scales peel off.
draw
cause
Poor storage, rain and snow erosion, long storage period, humid warehouse environment and poor ventilation.
Preventive and therapeutic measures
1, raw materials of steel bars should be stored in warehouses or sheds, and the ground should be kept dry. Steel bars should not be directly stacked on the ground, and drainage measures should be taken around the site, and the stacking period should be shortened as much as possible. Light yellow and slight floating rust do not need to be treated.
2. Reddish brown rust spots can be removed by manual steel brush, and mechanical methods should be adopted as far as possible. For serious corrosion and peeling of rust, it is necessary to study whether to degrade the use. Click here to download the construction technical data for free.
2. The varieties and grades of steel bars are mixed, and the steel bars with different diameters are piled up together, which is difficult to distinguish and affects the use. Especially secondary steel and tertiary steel.
draw
cause
Improper management of raw material warehouse and lax system; If the diameters are similar, they can sometimes be distinguished by visual inspection; The technical proof materials were not sent to the warehouse together with the physical reinforcement.
Preventive and therapeutic measures
1, raw materials piled up and semi-finished products processed shall be marked with materials and specifications.
2. Carefully check the materials and specifications before blanking, especially the secondary steel and tertiary steel.
Second, the reinforced mechanical test
Phenomena and problems
The scientific experiment on the strength of steel raw materials and joints is not standardized: the batch number and quantity of steel materials list are inconsistent with the experimental report, and the engineering parts are not detailed. Mechanical experiments were not carried out in batches according to the requirements of the specification.
1, raw materials
Preventive and control measures
In the tensile test, each group has 2 pieces, about 500mm long. 350 mm. The same factory, the same heat number, the same specification and the same delivery status, every 60t is an acceptance batch, and less than 60t is counted as a batch. (Round steel bar specimens are taken from different plates, and any two or more straight steel bars are intercepted).
2, flash welding joint
Preventive and control measures
300 welded joints of steel bars with the same grade and diameter completed by the same welder in the same team shall be regarded as a batch. Samples Six samples were randomly cut from the finished product. Three of them are about 500mm long in tensile test and 350mm long in cold bending test.
3, arc welding head
Preventive and control measures
Engineering welding conditions: 300 joints of the same joint type test and the same steel grade are accepted as a batch. On-site conditions: For the same joint type test, 300 joints on each floor of the same steel grade are regarded as an acceptance batch, and less than 300 joints are also counted as a batch. Samples Three samples with a length of about 500mm were randomly cut from the finished product for tensile test.
4, electroslag pressure welding head
Preventive and control measures
300 joints of the same reinforcement level in each floor or construction section shall be counted as a batch, and less than 300 joints shall be counted as a batch. Samples Three samples with a length of about 500mm were randomly cut from the finished product for tensile test.
5, air pressure welding joint
Preventive and control measures
300 joints of the same reinforcement level in each floor or construction section shall be counted as a batch, and less than 300 joints shall be counted as a batch. Samples Three samples with a length of about 500mm were randomly cut from the finished product for tensile test.
6. Lift and remove the connecting joint.
Preventive and control measures
On-site inspection of reinforced mechanical joints shall be carried out according to the acceptance batch. Under the same construction conditions, joints of the same grade, type and specification of the same batch of materials shall be used, with 500 joints as an acceptance batch for inspection and pre-acceptance, and less than 500 joints as an acceptance batch. For each acceptance batch of joints, three joint specimens must be randomly intercepted in the project for tensile strength test.
Third, the protection of finished steel products
1. After the thread of straight thread at the end of steel bar is processed, the thread is not effectively protected.
draw
Preventive and control measures
After the straight thread thread at the end of steel bar is processed, put on a plastic cap to protect the thread.
2. The reserved steel bars in post-cast strip and construction joints have been put on hold for a long time, without rust protection.
draw
Preventive and control measures
If the reserved reinforcement in the post-cast strip, construction joint and other parts is put on hold for more than 3 months, the reserved reinforcement must be rusted (painted with cement slurry on the surface of the reinforcement).
Four, steel processing
1, stirrup hook length is not enough.
draw
cause
1, the length of steel bar blanking is not enough. 2. There is deviation in the processing machinery. 3, labor saving and convenient installation.
Preventive and therapeutic measures
1, carefully check the drawings, be familiar with the specification requirements, and accurately calculate the ingredient list.
2. Batch processing should be carried out after the actual lofting is verified.
3. Check the construction machinery and correct the deviation.
4. Like the S-shaped tractor, manually bend it back after installation 135. (as shown in figure 2).
5. The length of the straight part of the stirrup after bending: for general structures, it should not be less than 5 times the diameter of the stirrup; Structures with seismic requirements shall not be less than 10 times of stirrup diameter.
2. Hook angle of stirrup is less than 135.
draw
Preventive and control measures
Bending angle of stirrup hook: for general structure, it should not be less than 90; Structures with seismic requirements should be 135.
3. The steel bar in the threaded disc is straightened, and the alloy top block in the machine is too tight, resulting in the damage of the steel rib.
draw
cause
The steel bar in the threaded disc is straightened, and the alloy top block in the machine is too tight, which leads to the damage of the steel rib.
Preventive and control measures
Straighten the rebar in the threaded disc and adjust the alloy top block in the machine according to the rebar specification. Ensure that the reinforcement can be straightened, and the reinforcement ribs shall not be damaged, and cold drawing is not allowed to reduce weight.
4. The bending radius of stirrups is too large.
draw
cause
According to the specifications of steel bars, no bending machine is selected.
Preventive and control measures
When 1 and 135 hooks need to be made at the ends of steel bars, the bending inner diameter d of HRB335 and HRB400 steel bars should not be less than 4 times the diameter of steel bars, and the length of the straight part after the hooks are bent should meet the design requirements.
2. Bending angle of stirrup hook: For general structure, it should not be less than 90; Structures with seismic requirements should be 135.
3. The length of the straight part of the stirrup after bending: for general members, it should not be less than 5 times of the stirrup diameter, and for structures with seismic requirements, it should not be less than 10 times of the stirrup diameter.
Five, steel binding
1, there are too few binding points between reinforcement and stirrup at the bottom of beam.
draw
Preventive and control measures
Requirements: The intersection of steel bars at the corner of the beam should be firmly bound at all points, and the intersection of the middle part can be firmly bound alternately, but the stressed steel bars should not be displaced. Click here to download the construction technical data for free.
2, steel binding is not standardized, not strong, and there are many phenomena of missing binding.
Preventive and control measures
Requirements:
1, the direction of wire netting should be changed, showing a figure of eight.
2, binding joint should use three pairs of wire fastened.
3, mesh in steel binding (such as beam through) range should be arc.
4, two-way reinforced fabric should be curved.
5, reinforced into the bearing part should be arc.
Note: Each steel bar must be bound at three points within the overlapping length, with double wires at 30mm at both ends of the overlapping steel bar and one in the middle.
Six, reinforced displacement
1. Displacement of overhanging reinforcement of wall column.
draw
cause
1, the formwork is not fixed firmly, and something collides during the construction, resulting in the dislocation of steel bars.
2. The stirrup is made incorrectly, and the binding is not firm, which leads to the deformation of the steel skeleton.
3. The protective layer is uneven.
4. The high density of steel bars in beam-column joints leads to the dislocation of steel bars in wall columns.
5. When pouring concrete, the steel bar was touched, and it was not recovered in time.
Preventive and control measures
1, add temporary stirrups to the cantilever part, install it according to the pattern position, then fix it with formwork, repeat and pour concrete. If there is any displacement, it should be corrected before pouring concrete.
2, pay attention to the cast operation, try not to collide with steel bars, and check and correct them in time by special personnel during the cast process.
3. Before pouring concrete, mark the position of column and wall steel dowel with paint on the board or beam, and then fix it with welding positioning hoop or horizontal steel dowel (for steel dowel of board wall).
4. When adjusting the spacing (or displacement) of steel bars, the steel bars should be bent slowly with the bending angle less than 1:6.
Seven, reinforced protective layer
1, when the structure or component is dismantled, it is found that there are steel bars exposed on the concrete surface.
draw
cause
The protective cushion is too thin or falls off, the steel bar forming size is inaccurate, or the steel bar skeleton is improperly bound, which causes the skeleton size to be too large and conflicts with the formwork locally. When vibrating concrete, the vibrator knocks on the steel bar, causing the steel bar to shift or the binding buckle to loosen.
Preventive and control measures
Cushions should be properly and reliably padded. When erecting the steel bar with embedded wire, tie it to the outside of the steel bar skeleton. In order to make the thickness of protective layer accurate, pull the steel skeleton onto the formwork with iron wire, squeeze and pad it, and strictly check the forming size of steel bar. The steel skeleton shall be bound outside the formwork to control its overall size, which shall not exceed the allowable value.
The material selection of reinforced protective layer pad should ensure the strength and thickness. Ensure that the number of pads is sufficient. The slab shall be installed with two-way pads at the intersection edge (angle) 100mm away from the beam or wall, and the vertical and horizontal spacing of the pads is about 800mm, which is installed below the intersection point of steel bars at the lower part of the slab.
Eight, reinforced connection joint
1. Too many joints in the same section: when binding or installing the steel skeleton, it is found that there are too many joints in the same section, and the percentage of its cross-sectional area to the total cross-sectional area of steel bars exceeds the specified value in the specification.
draw
cause
1, steel ingredients were neglected and the length of raw materials was not seriously considered.
2. Ignore the joints configured in the same section of the member, and the distance shall not be less than the lap length.
Preventive and control measures
1, find out the meaning of the same section specified in the specification.
2. The ingredients shall be numbered according to the bill of materials.
Specification requirements:
1. Allowable percentage of joint area: (1) In the same connection section (the length of the connection section of steel bar binding lap joint is 1.3Ll), the percentage of lap joint area of longitudinal tensile reinforcement shall meet the following requirements: a. Beam, plate and wall components shall not be greater than 25%. B, column component is not easy to be greater than 50%. Longitudinal compressive reinforcement is not easy to be greater than 50%. (2) The length of the connection section between the mechanical connection of steel bar and the welded joint is 35d(d is the larger diameter of longitudinal steel bar) and not less than 500mm. The area percentage of lap joints of longitudinal tensile reinforcement shall meet the following requirements: A. The tensile area shall not be greater than 50%, and the compressive area shall not be limited. B, the joint is not easy to set in the beam end and column end stirrup encryption area of the frame with seismic fortification requirements. When unavoidable, the mechanical joint with equal strength and high quality should not be greater than 50%.
2. The steel joint should be set in a place with less stress. It is not advisable to set two or more joints for the same longitudinal reinforcement. The distance from the end of the joint to the bending starting point of the steel bar should not be less than 10 times the diameter of the steel bar.
Nine, reinforced straight thread sleeve connection
1, the straight thread connection of steel bar is not constructed according to the specification requirements.
draw
cause
The straight thread used for steel bar connection is too long and unmarked, and there are too many threads in some joints, so it is impossible to tell whether the threads are screwed in place.
Preventive and control measures
Mark the thread teeth with paint (1/2 sleeve length) as the basis for quality inspection. Requirements: The general contractor and the supervisor shall conduct 100% inspection on all straight thread sleeve joints.
1, steel cutting, grinding wheel cutting machine should be adopted, the end face of the incision should be perpendicular to the axis, and there should be no horseshoe shape or deviation.
2, straight thread joint should use torque wrench or pipe wrench for construction.
3. The screwed straight threaded joint shall be marked, and the length of the single-side exposed threaded buckle shall not exceed 2P.
Ten, steel electroslag pressure welding connection
1, axis deviation of electroslag pressure welding, uneven welding package.
draw
Preventive and control measures
All unqualified joints should be removed and re-welded. Re-disclose the construction technology of steel bar connection to operators and replace unqualified welders. Re-make the electroslag pressure welding joint specimen for second interview, and the subsequent construction can be carried out only after it is qualified.
Welding defects and treatment measures
Axis offset: 1. Straighten the ends of steel bars. 2, the correct installation of fixture and steel bar. 3. Avoid excessive jacking pressure. 4. Repair or replace the fixture in time.
Bending: 1. Straighten the ends of steel bars. 2, pay attention to the installation and support of the upper reinforcement. 3. Avoid unloading the fixture too quickly after welding. 4. Repair or replace the fixture in time.
Undercutting: 1, reducing welding current. 2, shorten the welding time. 3. Pay attention to the starting point and stopping point of the upper jaw to ensure that the upper reinforcement is pressed in place.
Incomplete penetration: 1. Increase welding current. Avoid too short welding time. 3, maintenance fixture, to ensure that the steel bar down freely.
Uneven welding package: 1, and the steel bar section should be straight. 2. Fill the flux as evenly as possible. 3. Extend the welding time and increase the melting amount appropriately.
Pore: 1, flux as required. 2, remove the rust of steel welding parts. 3. Ensure that the joint is correctly buried in the flux.
Fuel: 1. Remove rust from steel bars. 2. Strengthen the reinforcement as much as possible.
Welding ladle dripping: 1, completely blocking the leakage hole of flux cylinder. 2. Avoid recycling flux too quickly after welding.
Acceptance requirements (visual inspection): 1. The height of the surrounding welding package protruding from the steel bar surface should be greater than or equal to 4 mm. There should be no burn defect at the contact between the steel bar and the electrode. 3. The bending angle of the joint shall not be greater than 4. 4, the axis of the joint offset shall not be greater than 0. 1 times the diameter of the steel bar, and shall not be greater than 2 mm ..
Remarks: electroslag pressure welding is suitable for the connection of vertical steel bars in cast-in-place concrete structures such as columns, walls and structures; After vertical welding, it shall not be placed horizontally in beams, plates and other components as horizontal reinforcement. When welding ribbed steel bars, it is easy to weld longitudinal ribs to longitudinal ribs.
Eleven, reinforced lap
1, the welding lap length of reinforcement is not enough.
draw
The lap length of steel bar binding is not enough.
cause
The blanking length of steel bar is not enough.
Preventive and control measures
1, carefully check the drawings, be familiar with the specification requirements, and accurately calculate the ingredient list.
2, check the ingredients list and component size when reinforced installation.
Specification requirements:
1, the minimum lap length of longitudinal tensile reinforcement should meet the requirements of acceptance specifications, and attention should be paid to it.
(1), the lap length of the street bound by compressed steel bars should be 0.7 times the value in the table.
(2) In any case, the lap length of longitudinal tensile reinforcement shall not be less than 300 mm ... The lap length of compressive reinforcement shall not be less than 200mm.
(3) The lap length of two steel bars with different diameters shall be calculated according to the diameter of the thinner steel bar.
(4) Within the lap length of street binding, three points should be bound.
2. Arc welding connection: When steel bars are welded by arc welding, the overlapping double-sided welding length is 4d(5d) and the overlapping single-sided welding length is 8d( 10d).
Twelve, steel bar anchorage
1, reinforcement anchorage length is not enough.
draw
cause
The blanking length of steel bar is not enough.
Preventive and control measures
1, carefully check the drawings, be familiar with the specification requirements, and accurately calculate the ingredient list.
2, check the ingredients list and component size when reinforced installation.
3, when the steel bar straight into the bearing length does not meet the requirements of anchorage, can be used in the form of bending.
Thirteen, steel skeleton binding
1, steel skeleton of structural beam is deformed.
draw
cause
1, the binding point of steel skeleton is not firm.
2, the concrete protective layer pad is not in place, under the action of external force, steel skeleton deformation.
3. Inspection is not in place before pouring concrete.
Preventive and control measures
1, the binding point of steel skeleton is firmly bound.
2. The rebar position is accurate, and the concrete protective layer pad is in place. So as to avoid the influence of external force during the construction of the subsequent process. Click here to download the construction technical data for free.
2. The structural beam reinforcement is in multiple rows, and the binding position does not meet the requirements.
draw
cause
1, technical disclosure is unclear.
2. The combination point is not strong.
Preventive and control measures
1, strengthen technical disclosure and inspection.
2, steel skeleton binding point binding is firm.
3. The rebar position is accurate, and the concrete protective layer pad is in place. So as to avoid the influence of external force during the construction of the subsequent process.
4, lift the second row of negative bending moment reinforcement, ensure the spacing with the first row of reinforcement in 25 mm ..
Fourteen, the structure of the reserved hole reinforcement
1. The reserved hole of the structural plate cuts off the steel bar, and the steel bar does not reach the designated position.
draw
cause
1, technical disclosure is unclear.
2. The installation project only pays attention to its own convenience and fails to form a technical connection with civil engineering.
3. Inspection and acceptance are not in place.
Preventive and control measures
1, technical disclosure before construction.
2. Atlas 04G 10 1-4(P35-36):
(1) When the side length of the rectangular hole is not more than 300 and the diameter of the circular hole is not more than 300, the reinforcement bypasses the hole and no additional reinforcement is set.
(2) when the rectangular hole edge is longer than 300 but the diameter of the circular hole is not greater than 1000, the longitudinal reinforcement shall be reinforced according to the specifications, quantity and length. When the design is not specified, two steel bars with a diameter of not less than 12mm and not less than 50% of the total area of longitudinal steel bars cut in the same direction shall be set on each side. The strength grade of the steel bar is the same as that of the cut steel bar, but I don't know it is a grade, and the spacing is 30 mm
2. The reserved hole in the shear wall cuts off the steel bar, and the steel bar does not reach the designated position.
draw
Preventive and control measures
Atlas 09G901-2 (3-11~ 3-12):
1, round hole: ① When the diameter is less than or equal to 300, the reinforcement shall be designed according to the notes. When there is no indication in the design, two steel bars with a diameter of not less than 12mm and not less than 50% of the total area of longitudinal steel bars cut in the same direction shall be set on each side, and the strength grade of the steel bars is the same as that of the cut steel bars. (2) when the diameter is greater than 300 and less than or equal to 800, should be set according to the design instructions. (3) When the diameter is greater than 800, the reinforcement of the concealed beam at the top and bottom of the hole shall be marked according to the design. When there is no shear wall coupling beam at the top or bottom of the hole, the reinforcement of the concealed beam shall not be repeated.
2. Square hole: ① When the hole edge size is less than or equal to 800, the reinforcement should be designed according to the notes. When there is no indication in the design, two steel bars with a diameter of not less than 12mm and not less than 50% of the total area of longitudinal steel bars cut in the same direction shall be set on each side, and the strength grade of the steel bars is the same as that of the cut steel bars. (2) When the size of the side of the square hole is greater than 800, the reinforcement of the concealed beam at the top and bottom of the hole shall be marked according to the design. When there is no shear wall coupling beam at the top or bottom of the hole, the concealed beam shall not be reinforced repeatedly.
Fifteen, steel planting
1, rebar planting is not firm (no binder).
draw
cause
1, the drilling depth is not enough.
2. The adhesive does not meet the requirements.
3. It was not emptied after drilling.
4. It did not stand 12 hours after rebar planting.
Preventive and control measures
1, to ensure the drilling depth.
2. Use qualified structural steel planting feet.
3. Clean the floating ash after drilling.
4. After reinforced planting, let it stand for 12 hours without disturbance.
5, in the secondary structure construction should be according to the wall modulus or component size blanking planting steel bar.
Reinforcement planting construction method:
Construction process: drilling-venting-glue filling-rebar planting-gel.
1, drill holes with impact electric drill. When drilling, the aperture and drilling depth should meet the design requirements.
2, when emptying, first use blowing method to remove dust in the hole, and then use hole cleaning brush to clean the hole, which should be done several times. At the same time, it should not be washed with water, so as to avoid the water remaining in the hole weakening the role of the adhesive.
3. Inject the adhesive evenly from the bottom of the hole with a rebar planting syringe.
4. Gently implant the steel bar in the hole parallel to the hole direction clockwise until it is inserted into the bottom of the hole and the adhesive overflows.
5. Fix the exposed end of steel bar so that it is not affected by external force until it condenses.
ID: gczjkt
good news
ID:sghyzj
ID:gczlkt
ID:gczbpt
ID:jzjyswx
▲
Construction workers' union (circular standard)
ID:jzgrlm
ID:jzgcnc