Summary of the construction plan for the main structure of the commercial pedestrian street building: The steel bars will be accepted in batches when they enter the site. The acceptance content includes checking the appearance of the signage, and then samples can be taken for mechanical performance testing in accordance with the relevant technical standards. , it can only be used after passing the inspection
This project has six floors, a frame structure, and the main body is the skeleton of the entire building. We must attach great importance to the construction quality of the project, rationally organize the labor force and project progress, and ensure the main structure Overall solid and safe.
(1) Construction process of the main cast-in-place structure
After the formwork and steel bars are completed for the columns and beams, the concrete is poured in one go. In order to speed up the progress and improve the work efficiency, make full use of the column construction Due to the short cycle, the columns, beams, and slabs can be relatively independent during structural construction to minimize the mutual influence of the two parts. Before the beam bottom formwork is laid, gaps will be left at the beam nodes on the column formwork, and according to In the sample diagram of the elevation of the beam bottom plate and the beam reinforcement, the bending length of the anchor bar at the beam end is used to determine the height of the column concrete pouring. When the above conditions are met, the column steel bars are tied, and the formwork is completed and accepted, the column concrete can be poured. Therefore, The column construction cycle is short, and the concrete construction can be completed before the beam and plate steel bars are tied.
(2) Steel bar engineering
1) Inspection of steel bars. Steel bars entering the site should have a factory quality certificate or test report, and each bundle of steel bars should have a label.
2) The steel bars will be accepted in batches when they enter the site. The acceptance content includes checking the appearance of the sign. Only then can samples be taken for mechanical performance testing in accordance with the relevant technical standards. They can only be used after passing the inspection.
3) When brittle fracture, cracks at bends, poor welding performance or significant non-sinking of mechanical properties occur during the processing of steel bars, chemical inspection or other inspections should be carried out.
4) When transporting and storing steel bars, labels must be retained, and corrosion and contamination must be avoided before and after inspection.
1. Steel bar processing
1) Before processing the steel bars, the appearance of the steel bars used should be inspected. The surface of the steel bars must be clean and free of damage, paint, paint stains and iron snipers. It is strictly prohibited to use steel bars with granular or flaky old rust.
2) The steel bars should be inspected before processing to ensure that there are no local bends. The inspected steel bars comply with the following regulations: When inspecting the steel bars by tensile method, the tensile ratio of the first-level steel bars should not be greater than 4%, and the tensile ratio of the second-level and third-level steel bars should not be greater than 4%. For steel bars, the tensile ratio should not be greater than 1%.
3) The shape, size and number of steel bars after installation, anchorage length and joint settings meet the design requirements.
4) The steel bars are cut according to the technical data in the drawings and reinforcement tables. During the cutting, if there are defects such as high degree of splitting, necking, obvious damage, excessive bending, etc. The steel bars should be partially removed and then used for cutting. The cuts of the steel bars should be smooth and there should be no horse tellurium shape or local bending.
5) Reinforcement bar forming should be based on the structural member reinforcement drawings, combined with the requirements for the thickness of the protective layer, joint form, bending steel and bending diameter, etc., calculate the reinforcement size, and use the sample drawing to conduct.
2. Stretching and welding of steel bars
1) When connecting steel bars, whether welding or binding, the distance between the end of the bent steel bar joint and the starting point of the steel bar bending should not be less than 10D , and should not be located at the largest bend of the component.
2) Before the formal welding of the steel bars, the welder responsible for the material joining task should conduct a trial welding according to the actual operating conditions to determine the reasonable process parameters and welding precautions and welding process standards.
3) The intersection points of the steel bars should be tied firmly with iron wire, and each tie point should be twisted two and a half turns.
4) For one-way stressed steel mesh, except for the intersection points of the two surrounding rows of steel bars, which should all be tied firmly, the middle part can be separated and tied a little, but the binding directions of the wires must be in a figure-eight shape with each other, two-way. Stress-bearing steel mesh, all intersection points of steel bars must be firmly tied. Depressions, weld burrs; cracks at the joints, undercut depth, pores, quantity and size of slag inclusions, and joint size deviations must comply with specifications.
5) Column bars are connected by air pressure welding, and their appearance should meet the following requirements:
The joint welds should be full and relatively uniform, there should be no obvious defects such as burns on the surface of the steel bars, and the steel bars at the joints should be The offset of the axis shall not exceed 0.1 times the diameter of the steel bar, and shall not be greater than 2mm, and the bending at the joint shall not be greater than 4%.
6) The welded joints of the stressed steel bars in the same component should be staggered from each other. The same steel bar must not have any welded joints in the section where the length of any welded joint is 35 times the diameter of the steel bar and not less than 500mm. For two joints, the cross-sectional area of ??the tension steel bar with joints should not exceed 50%.
3. Production and installation of steel bars
1) When the foundation floor adopts a double-layer steel mesh, steel braces or concrete braces should be provided below the upper mesh to ensure the position of the steel bars. Correct, the form and size of the steel bar supports are placed every 1 meter as shown in the figure, and the diameter is selected: when the plate thickness The seam surface should be smooth, and there should be no large depressions or welding burrs; there must be cracks at the joints; the undercut depth, pores, the number and size of slag inclusions, and the joint size deviation should comply with the specifications.
3) Column bars are connected by gas pressure welding, and their appearance must meet the following requirements:
The joint welds should be full and relatively uniform, and there should be no obvious defects such as burns on the surface of the steel bars; The offset of the axis of the steel bar shall not exceed 0.1 times the diameter of the steel bar, and shall not be greater than 2mm, and the bending at the joint shall not be greater than 4 degrees.
4) The welded joints of the stress-bearing steel bars placed in the same component should be staggered from each other. The same steel bar must not have any welded joints in the section where the length of any welded joint is 35 times the diameter of the steel bar and not less than 500mm. For two joints, the cross-sectional area of ??the tension steel bar with joints should not exceed 50%.
3. Production and installation of steel bars
1) When the foundation floor adopts double-layer steel mesh, steel concession feet or concrete feet should be installed under the upper layer of steel mesh to ensure that the steel bars are placed correctly. The form and size of the steel support legs are as shown in the figure. Place one every 1m and select the diameter: 8-10mm when the plate thickness h ≤ 30; 12-14mm when the plate thickness h = 30-50cm; when the plate surface When thickness h＞50cm, it is 16-18mm.
2) The hooks of the steel bars in the slab should be facing upwards and not to one side, but the hooks of the upper steel bars of the double-layer steel bars should be facing downwards.
3) The stirrups used to connect cast-in-place columns and foundations should be one column bar diameter smaller than the column stirrups to facilitate connection. The position of the inserted ribs must be firmly fixed to avoid deviation of the axis of the column.
4) When installing column reinforcements, the main reinforcements should be welded first, then the flux at the column feet should be cleaned, and finally the pre-calculated stirrups should be put on them.
5) Use chalk to draw the stirrup spacing on the standing column steel bars, and move the stirrups upward. The stirrups should be perpendicular to the main bars. The intersection points of the corners of the stirrups and the main bars should be tied. The intersection points of the main bars and the straight parts of the stirrups should be tied in a staggered pattern or in a grid pattern. The joints of the stirrups, that is, the hooks, overlap and should be arranged staggered along the vertical direction of the column.
6) According to the thickness of the column protective layer, tie the prefabricated non-mud mortar blocks with lead wire to the column steel bars to ensure the correct thickness of the concrete protective layer.
7) The steel bars of the lower columns are exposed on the floor. It is advisable to use tool-type column bars to retract them into one column bar diameter to facilitate the overlap of the steel bars of the upper columns. When the column section changes, the exposed part of the lower column steel bars must be shrunk accurately before tying the beam's steel bars.
8) When tying the steel bars of beams and plates, water and electricity pipelines should be prevented from lifting or loosening the steel bars.
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From real estate information download
Business Summary of the construction plan for the main structure of the pedestrian street building: The steel bars will be inspected in batches when they enter the site. The acceptance content includes checking the appearance of the sign. Only then can samples be taken for mechanical performance testing in accordance with the relevant technical standards. They can only be used after passing the inspection< /p>
From real estate information download) When the longitudinal load-bearing steel bars in the beam are arranged in double layers, short steel bars with a diameter ≥ mm should be used between the two rows of steel bars to maintain the design distance.
10) The joints of the stirrups in the beam should be staggered on the two shelf steel bars, and the rest should be on the same column.
11) The steel mesh binding of the board is the same as that of the foundation, but attention should be paid to the negative reinforcement on the upper part of the board to prevent it from being stepped on, especially for awnings, overhangs, balconies and other cantilever boards, the negative reinforcement must be strictly controlled position to avoid breakage.
12) For lintels connected to concrete walls and columns, the lintel reinforcements should be the same as the lintel bottom bars, and the spacing between lintel stirrups should be increased to 100mm.
13) Where the plate, secondary beam and main beam intersect, the steel bar of the plate is on top, the steel bar of the secondary beam is in the middle, and the steel bar of the main beam is on the bottom.
14) When the steel bars at the frame nodes are very densely interspersed, special attention should be paid to the clear distance between the main bars on the south side of the beam to be more than 30mm to facilitate the pouring of concrete.
15) The cooperative relationship between the binding of beam steel bars and the installation of formwork:
A. When the height of the beam is small, the steel bars of the beam are tied overhead on the top of the beam and then dropped. Bit.
B. When the height of the beam is large (≥1.2), the steel bars of the beam should be tied on the bottom formwork, and the two sides or one side of the formwork should be installed behind the formwork.
16) When the steel bars are double-layered, braces should be set between the two layers to fix the spacing between the two layers. The braces can be made of steel bars with a diameter of 6-10, and the length is equal to the two layers. The net distance between the steel mesh sheets is about 1 meter, and they are arranged staggered from each other.
17) The tie bars of concrete beams and columns must hook the main bars and stirrups. When the beam and column edges are level, the beam bars should be placed inside the column bars. When the primary and secondary beams are of the same height, additional bars should be set. The bottom steel bars are located within the main beam steel bars. When the bottom of the secondary beam is lower than the bottom of the main beam, additional steel bars should be installed.
4. Quality assurance measures for steel bar projects
1) Steel bar materials should be stored in warehouses or sheds to keep the ground dry. Steel bars cannot be stacked directly
On the ground, it must be lifted with concrete piers, concrete or grid wood, so that it is more than 200mm above the ground.
2) The steel bar inspection site should be equipped with a slope to be inspected and entered into the inventory. The warehouse should be divided into different steel bar stacking areas. Each pile of steel bars should have a label or hangout to indicate the variety, grade, diameter, technology, and indicate the number and number. The whole batch quantity, etc., the shape and markings of the steel bar threads must be checked during acceptance. If the steel factory does not follow the regulations, it must be identified against the contents of the technical certificate. The diameter of the steel bars is difficult to distinguish and must be checked with a caliper.
3) Check the steel bar factory certificate or test report. If any suspicious conditions are found, such as excessive strength or large fluctuations, re-examination should be carried out.
4) Strengthen the management of steel bar batching, and predetermine various shapes of steel bars based on the unit's equipment conditions and traditional operating experience. The cutting length and batching should be carefully considered. For steel bars that are relatively complicated at the beginning, it is best to release real samples first and pre-set appropriate operating parameters according to specific conditions as a demonstration.
5) Handling and stacking should be carried out with care, and the placement location should be flat. Try to go to the site according to construction needs and stack them in order of use to avoid unnecessary turning.
6) The steel frame assembly must be controlled according to the design geometric dimensions, and the production and processing dimensions of the ingredients must be accurate.
Before assembling the steel bars, the reinforcement should be checked according to the dimensions marked in the drawings. The size and placement must be corrected if inaccurate. The assembly must be firm and looseness and deformation are strictly prohibited.
7) The steel frame must be made and processed according to the drawings to ensure that the size and shape of each steel bar are accurate. The assembly should be firm, accurate, and with good integrity. When the steel frame is skewed, twisted, or deformed, Make corrections in time, then tie the lashing buckles firmly, and add cross lashings appropriately. In order to enhance the ability to resist deformation, diagonal tie bars and spot welds should be added to improve the strength and integrity of the skeleton.
8) The overhanging steel bars at the column head should be fixed using formwork and stirrups to prevent the overhanging steel bars from being dislocated and deformed.
9) The angle and straight length of the stirrup hooks must comply with the design and specification requirements. The spacing size should be strictly controlled during assembly: the openings should be staggered, the binding must be firm, and loosening and deflection are strictly prohibited.
(10) The lap tying in the tying of the steel frame should not be loosened or tripped. In order to increase the integrity of the formed steel frame, arc welding spots can be used at appropriate positions of the frame.
(11) The slurry pads must be suitable and reliable. The erected steel bars can be padded with iron wires and tied to the outside of the steel frame. At the same time, in order to ensure the thickness of the protective layer is accurate, iron wires can be used to pull the steel frame. Push the pads firmly against the formwork and strictly check the forming dimensions of the steel bars.
(12) The heavy frame should prevent the stirrups from deforming. If necessary, a strong structure should be added to the frame. The diameter is generally 10, and steel bars with the same diameter as the stirrups should be used as tie bars. The structural steel bars are connected to enhance the integrity of the skeleton. The tie bars can be set every 3-5 stirrups.
(13) The bent steel bars in the cantilever members should be installed strictly according to the direction of the structural stress to ensure the position of the structural stress bars. They should be inspected before pouring concrete and adjusted immediately if errors are found to eliminate hidden dangers. , to prevent accidents.
(14) To prevent the displacement of the double-layer mesh, stirrups or steel bars can be used to make brackets, and the upper and lower meshes can be tied together to form a whole. How to consider the accuracy of the position of the upper mesh can be done The location is determined by the steel support and hanging method.
(15) Before assembling the steel frame, you must be familiar with the drawings and check the ingredient list and bill of materials according to the drawings and the steel bar ingredient list, process them one by one, check whether the steel bar specifications are complete and accurate, and whether the initial quantity matches the drawing requirements , and should be assembled according to the installation sequence and steps in the drawings to prevent leakage of reinforcements.
(3) Formwork Engineering
Formwork engineering is an important guarantee for the quality of the main structure and will directly affect the concrete quality and construction progress.
In the construction stage of the main structure For sub-projects with the longest construction period and higher costs, the formwork preparation plan must comprehensively consider quality, schedule, cost, and constructability. On the premise of ensuring quality, safety, and progress, the input of turnover materials must be reduced. To reduce costs, the shape and structure of this project are complex and have arcs, but they are relatively regular and have many standard layers. The formwork uses a nine-ply board formwork and a customized formwork. For complex parts such as holes for stairs, 18mm thick multi-layer plywood is used as a formwork to isolate it. The emulsified isolation agent is used as the agent, and the formwork support system uses wooden columns to ensure the construction quality and construction progress of the formwork.
This project will be equipped with five sets of column vertical formwork, five sets of beam and plate formwork, five sets of staircase formwork for each seat, and sufficient formwork support for construction according to the construction progress requirements.
General requirements for formwork preparation:
Ensure that the shape and size of the project structure and each part are correct relative to the campus, have sufficient bearing capacity, stiffness and stability, and can be used during construction The dynamic load generated in the process, the formwork structure is simple, easy to assemble and disassemble, and is convenient for tying steel bars. The joints should not leak grout. The contact surface between the formwork surface and the concrete should be coated with an isolation agent. When designing the formwork and supports, measures should be taken to prevent the formwork from leaking. Deformed or burst.
Formwork engineering is an important part of concrete structure engineering. The formwork and its supports must have sufficient strength, stiffness and stability, and can reliably withstand the self-weight and lateral pressure of steel bars and concrete as well as construction loads. Ensure that the geometric dimensions and mutual positions of the engineering structure and components are correct, reasonable and simple, easy to disassemble and assemble, and the formwork is tight and does not leak slurry.
Quality standards during formwork installation
Project allowable deviationProject allowable deviation
Axis 5 The upper surface elevation of the bottom mold is plus or minus 5
Section size + 4-5 storey height, vertical 3
Height difference between two adjacent boards 2, smooth surface 5
1. Column and beam formwork construction:
Wall The nine-ply formwork of columns, beams, timber joists and wooden column supports, the vertical and horizontal spacing of cast-in-place beams, load-bearing frames and the number of pull bars must be calculated and determined, and arched according to the specifications. When beams and slabs When the span is ≧4 meters, the base plate should be arched, with the amplitude being 1/1000-3/1000 of the span.
All templates are copied and drawn by carpenters, and reviewed by construction and technical personnel. The formwork is prefabricated in the carpentry shed workshop and assembled on site. The cast-in-place beam-slab floor structure is modeled, focusing on the modeling quality of beam and column joints.
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From real estate information download
Summary of the construction plan for the main structure of the commercial pedestrian street building: The steel bars will be accepted in batches when entering the site. The acceptance content includes inspection After the appearance of the sign has been inspected, samples can be taken for mechanical performance testing in accordance with the relevant technical standards. They can only be used after passing the inspection
Download from real estate information The bottom plate of the beam and the side formwork should be in one piece Overlapping with columns, the inlaid joint must be set in the beam. This can avoid the beam-column node shrinkage and ensure the accuracy of the beam-column node size. The beam height of the frame is more than 500, and a 12-pair pull screw (jacket) is added to the middle of the beam height. plastic tube).
2. Construction of stair formwork:
The bottom form of the stairs is made of nine-ply board, and the step side formwork and step baffles are all made of nine-ply board. The step surface is designed to make the steps accurate in size and with clear edges and corners. After the steps are concreted, they are sealed with wooden boards. Since the top force on the formwork will be generated when pouring concrete, it is necessary to strengthen the control of screw deformation during construction.
1. Formwork removal
Vertical formwork removal: It can only be removed after its own strength can ensure that it will not deform and no corners will be lost or edges will be missing when the formwork is removed.
Horizontal formwork removal: When pouring and tamping concrete, make a set of test blocks to control the formwork removal time and maintain them under the same conditions as the actual ones. The formwork removal time is determined based on the test results of the test block and the size of the structural span.
The dismantling of the formwork shall comply with the following regulations:
a. The dismantling order must be issued by the technical person in charge before the dismantling work can be carried out;
b. It is not load-bearing The formwork can be removed only when its strength can ensure that its surface and edges are not lost.
c. Board, span; L75% When span L≥8M, R=100%L floor R≥75%;
d. During the formwork removal process, if it is found that the quality of the concrete affects the safety of the structure, the removal should be stopped immediately and reported to the technical person in charge for investigation and processing before removal.
E. Do a good job in protecting finished concrete products.
After the formwork is removed, it is immediately cleaned, trimmed, painted with release agent, and stacked for turnover.
4. Quality assurance and precautions for formwork:
a. The formwork needs to be designed and calculated to meet stiffness, strength and stability requirements, and can reliably withstand the weight of poured concrete. lateral pressure and other construction loads.
b. Before construction, the carpenter will turn over the sample and draw the template diagram and node diagram, and the construction and technical staff will review it before construction can begin. After the installation is completed, it will be reviewed and accepted by the relevant personnel of the project department.
c. Before formwork construction, a written technical explanation should be given to the team. A formwork removal notice must be issued by the project constructor before the formwork is removed.
d. When pouring and pounding concrete, special personnel must be present to supervise it.
(4) Concrete project
1. Concrete construction operation technology
a. Before pouring concrete, the formwork must be comprehensively inspected. Objects and construction waste must be cleaned up, and gaps in the formwork exceeding 2 mm should be blocked. The formwork and old concrete must be watered and moistened, and the construction joints must be grouted.
B. When pouring concrete into floor beams and slabs, start from one end and advance using the "pulling method". First pour the beam surface into a ladder shape, and then pour it together with the concrete of the slab when it reaches the floor slab position. The first layer of material should be cut slowly, so that the bottom of the beam is fully vibrated before the second layer of material is added. Use the "slurry driving method" to push the cement slurry around the stones along the bottom of the beam. Avoid touching the steel bars and embedded parts during vibration. , the thickness of the virtual paving when pouring the floor slab is slightly larger than the thickness of the slab. A flat vibrator is used for vertical pouring to support the tamping. Moving marks are constantly used to control the thickness of the concrete slab. After the vibration is completed, a secondary surface is used to reduce concrete shrinkage cracks.
C. At the junction of old and new concrete on slabs and columns, pour the patented concrete moist, lay thick concrete with appropriate cement mortar, and then pour it in layers. The pouring height of each layer should be excavated within 500. No construction joints shall be left during the concrete pouring and tamping process. When special construction joints are encountered, the construction joints shall be left in accordance with the design and specification requirements.
D. Stair concrete pouring. Stair section concrete is poured from bottom to top. First, tap the floor concrete. When reaching the step position, jump and pour the concrete together. Continue to push it upward and smooth it with a wooden trowel at any time. The construction joints of the tread surface stairs should be left three steps below the stairs or platform according to the situation. The construction joints should be set vertically to the floor. The self-care of the construction joints before each concrete pouring is the same as that of pillar concrete.
E. When using plug-in vibrators for concrete pouring, the plug-in vibrators should be inserted quickly and pulled out slowly. The insertion points should be evenly distributed and moved point by point in order without any omissions. The vibration should be evenly vibrated and the moving distance should not be larger than the vibrator. 1.5 positions of the rammer's action radius (generally 300-400 meters). During layered pouring, vibrate the upper second layer of concrete and insert more than 50 mm into the lower layer of concrete to eliminate the joint between the two layers. The moving distance of the flat vibrator should be able to ensure that the vibration The flat cover of the support device has some edges reinforced.
F. When pouring concrete, send steel workers and carpenters to observe the steel bars and formwork, reserve holes for embedded parts, insert bars, etc. to see if there is any displacement or blockage. If found, stop pouring immediately and check the poured concrete. Finished before initial setting.
G. After the concrete pouring is completed, it should be covered within 12 hours and watered for curing. In summer, weak wet straw bags or plastic films should be added for curing. The curing time should not be less than 7 days. For concrete mixed with retarder The structure that requires the agent and penetration should not be less than 14 days, and anti-freeze and heat preservation should be done in winter to prevent the concrete from being frozen during the initial setting and causing hidden dangers to the structure.
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