This project is mainly composed of six floors and frame structure, and the main body is the skeleton of the whole building. We must attach great importance to the construction quality of the project, reasonably organize the labor force and the progress of the project, and ensure the overall firmness and safety of the main structure.
(A) the main cast-in-place structure construction process
After the formwork and reinforcement are completed, concrete will be poured at one time. In order to speed up the progress, improve work efficiency and make full use of the short construction period of columns, columns, beams and plates can be separated during structural construction to minimize the interaction between the two parts. Before the beam bottom formwork is laid, the beam nodes on the column formwork will be left blank, and the pouring height of column concrete will be determined according to the elevation of the beam bottom floor and the bending length of the anchor bar at the beam end in the sample diagram of beam reinforcement. Meet the above conditions.
(2) Reinforcement works
1) rebar inspection. When steel bars enter the site, there should be factory quality certificate or test report, and each bundle of steel bars is marked.
2) Steel bars shall be accepted in batches when entering the site. The acceptance content includes checking the appearance of the sign, and then taking samples for mechanical performance test according to the relevant technical standards, and using them only after passing the inspection.
3) In case of brittle fracture, crack at bend, poor welding performance or obvious decrease in mechanical properties of steel bars during processing, chemical inspection or other inspection shall be conducted.
4) Steel bars must be marked during transportation and storage, and corrosion and pollution should be avoided before and after inspection.
1, steel processing
1) Before reinforcing bar processing, check the appearance of reinforcing bar. Steel surface must be clean, free of damage, paint, paint dirt and iron filings. It is forbidden to use steel bars with granular or flaky old rust.
2) Steel bars shall be investigated before processing to ensure that there is no local distortion. The investigated steel bars meet the following requirements: when the steel bars are investigated by tensile method, the tensile rate of the first-class steel bars should not be greater than 4%, and the tensile rate of the second-class and third-class steel bars should not be greater than 65438 0%.
3) The shape, size, installation quantity, anchorage length and joint setting of reinforcement shall meet the design requirements.
4) Steel bar blanking shall be carried out according to the drawing technical data and steel bar table. When blanking, steel bars with defects such as high splitting, necking, obvious damage and excessive bending should be partially removed before cutting. Steel bar incision should be smooth, and there should be no marten-like and local bending.
5) Steel bar forming should be carried out according to the steel bar details of structural members, combined with the requirements of protective layer thickness, joint form, bending steel bar and bending diameter. , the size of reinforcement can only be calculated after the sample drawing is adopted.
2. Stretching and welding of steel bars
1) When steel bars are connected, whether welding or binding, the distance between the end of the bent steel bar joint and the starting point of steel bar bending should not be less than 10D, nor should it be located at the maximum bending part of the member.
2) Before the formal welding of steel bars, the welder who undertakes the task of material connection shall conduct trial welding according to the actual working conditions to determine reasonable process parameters, welding precautions and welding process standards.
3) Steel bar intersections shall be securely bound with wire, and each point shall be wound for two and a half turns.
4) One-way stressed steel mesh, except for the intersection of two rows of steel bars around, the middle part can be bound at intervals, but the direction of wire binding must be splayed, and the two-way stressed steel mesh must be fastened. Depression, flash; There should be no cracks, undercut depth, porosity, slag inclusion number and size at the joint, and the joint size deviation should meet the specification requirements.
5) Column rebar shall be connected by air pressure welding, and its appearance shall meet the following requirements:
Welds should be full and uniform, and there should be no obvious defects such as burns on the surface of steel bars. The deviation of steel bar axis at the joint shall not exceed 0. 1 times the steel bar diameter, and shall not exceed 2㎜ at the same time, and the bending at the joint shall not exceed 4%.
6) The welded joints of steel bars in the same component shall be staggered, and the length of any welded joint shall be 35 times of the diameter of steel bars, and within a section of not less than 500㎜, there shall be no two joints in the same steel bar, and the sectional area of steel bars with joints shall not exceed 50%.
3, steel production and installation
1) When the foundation slab adopts double-layer steel mesh, steel brace or concrete brace should be set below the upper steel mesh to ensure the correct position of steel bars. The form and size of steel braces are as shown in the figure, and one is placed every 1 m, and the diameter is selected as follows: when the plate is thick,
2) Steel bars shall be connected by welding, and the welded products shall be inspected to ensure that the weld surface is smooth, and there shall be no large sag or flash; There shall be no cracks at the joints; The deviation of undercut depth, porosity, slag inclusion quantity and size, and joint size should meet the specification requirements.
3) Column rebar shall be connected by air pressure welding, and its appearance shall meet the following requirements:
Weld joints should be full and uniform, and there should be no obvious defects such as burns on the surface of steel bars; The deviation of steel bar axis at the joint should not exceed 0 of steel bar diameter. 1 times, at the same time, it shall not be greater than 2mm, and the joint bending shall not be greater than 4 degrees.
4) The welded joints of stressed steel bars placed high in the same component should be staggered, and the length of any welded joint should be 35 times of the diameter of the steel bar, and there should be no two joints in the same steel bar with a cross section of not less than 500mm, and the cross-sectional area of tensile steel bars with joints should not exceed 50%.
3. Fabrication and installation of steel bars
1) When the foundation slab adopts double-layer steel mesh, the upper steel mesh should be set under the steel yielding brace or concrete brace to ensure the correct placement of steel bars. The form and size of steel support are shown in the figure. When the thickness h is less than or equal to h≤30, the diameter per 1m is 8-10 mm; When the thickness h = 30-50 cm, it is12-14 mm; When the thickness h > 50 cm, it is16-18 mm.
2) The hook of the steel bar in the plate should be upward, and not backward to one side, but the hook of the upper steel bar of the double-layer steel bar should be downward.
3) The stirrup of the steel dowel used to connect the cast-in-place column with the foundation should be smaller than the stirrup of the column by one column rebar diameter for connection. The position of steel dowel must be fixed firmly to avoid column axis deviation.
4) When installing column rebar, the main rebar should be welded first, then the flux at the column foot should be cleaned up, and finally the stirrup calculated in advance should be put on it.
5) Draw the stirrup spacing with chalk on the column rebar that has been set up, and move the stirrup upward. Stirrup is perpendicular to the main reinforcement, the intersection of stirrup corner and main reinforcement should be bound, and the intersection of main reinforcement and straight part of stirrup or plaid pattern should be staggered. Stirrup joints, that is, hook lap, should be staggered along the column.
6) According to the thickness of the column protective layer, tie the prefabricated mud-free mortar pad to the column reinforcement with lead wire to ensure the correctness of the thickness of the concrete protective layer.
7) The reinforcement of the lower column is exposed from the floor. It is advisable to put the tool-type column rebar into a column rebar diameter, so that the rebar of the upper column can overlap. When the column section changes, the exposed part of the lower column reinforcement must shrink accurately before binding the beam reinforcement.
8) When binding the beam and slab reinforcement, it is necessary to prevent the reinforcement from being lifted or loosened by the hydropower pipeline.
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Summary of construction scheme of main structure of commercial pedestrian street building: acceptance of reinforcement in batches when entering the site. The acceptance content includes checking the appearance of the sign, and then taking samples according to relevant technical standards for mechanical performance test, which can only be used after passing the inspection.
When the longitudinal stressed steel bars in the beam are arranged in double layers, short steel bars with a diameter of ≥mm should be identified between two rows of steel bars to keep their design distance.
10) The joints of stirrups in beams should be staggered on two shelf bars, and the rest are in the same column.
1 1) The steel mesh binding of the slab is the same as that of the foundation, but attention should be paid to the negative reinforcement on the upper part of the slab to prevent it from being trampled, especially the cantilever slab such as awning, cornice and balcony, and the position of the negative reinforcement should be strictly controlled to avoid fracture.
12) The lintel gluten connected with concrete walls and columns is the same as the reinforcement at the bottom of lintel, and the spacing of lintel stirrups is encrypted to100 mm. ..
13) Where the slab, secondary beam and main beam intersect, the reinforcement of slab is above, the reinforcement of secondary beam is in the middle, and the reinforcement of main beam is below.
14) When the reinforcement at the frame node is very dense, special attention should be paid to the clear distance of the main reinforcement in the south of the beam to be greater than 30mm, so as to facilitate concrete pouring.
15) Coordination between beam steel binding and formwork installation;
A, when the height of the beam is small, the steel bar of the beam is tied to the top surface of the beam overhead and then settled.
B, the height of the beam is larger (above 1.2), and the reinforcement of the beam should be bound on the bottom formwork, and the formwork on both sides or one side should be installed.
16) At the same time, when double-layer steel bars are used, tie bars should be set between the two layers of steel bars, and the spacing between the two layers of steel bars should be fixed. Stains can be made of steel bars with a diameter of 6- 10, the length is equal to the clear distance between two layers of steel bars, and the spacing is about 1 m, which is staggered.
17) The Rachel bars of concrete beams and columns must be hooked on the main bars and stirrups. When the beam and column are at peace, the beam reinforcement should be placed in the column reinforcement. When the height of primary and secondary beams is the same, the attached bottom reinforcement should be set in the main beam reinforcement. When the bottom of the secondary beam is lower than the bottom of the main beam, additional reinforcement shall be set.
4, steel engineering quality assurance measures
1) Reinforced materials shall be stored in warehouses or sheds, and the ground shall be kept dry, and shall not be directly stacked.
When stacked on the ground, it must be lifted by concrete pier, concrete or lattice, so that it is more than 200㎜ from the ground.
2) Steel bars shall be accepted and put into storage by gradient personnel, and the warehouse shall be divided into different steel bar stacking areas. Each pile of steel bars shall be labeled or listed, indicating the variety, grade, diameter, technology, number and batch number, etc. Upon acceptance, the shape and mark of rebar thread shall be checked. If the steel mill fails to do it according to the regulations, it shall be recognized according to the technical certificate. It is difficult to distinguish the diameter of steel bars, so check with calipers.
3) Check the factory certificate or test report of steel bar, and recheck it if suspicious circumstances such as high strength or large fluctuation are found.
4) Strengthen the management of steel bar batching, and determine various shapes of steel bars in advance according to the equipment situation and traditional operation experience of this unit. The blanking length and ingredients are well considered. For the steel bar with complicated beginning, it is best to release the actual sample first and preset the appropriate operating parameters according to the specific situation, which is a demonstration.
5) Handling and stacking should be handled with care and placed smoothly. Try to go to the site according to the construction needs, and pile up according to the purpose to avoid unnecessary turnover.
6) The steel skeleton assembly must be controlled according to the design geometric size, and the ingredients must be made, and the processing size must be accurate.
Before assembling steel bars, check the size and placement of steel bars according to the dimensions marked on the drawings. If it is not accurate, it must be adjusted until it is accurate. The assembly shall be firm, and looseness and deformation are strictly prohibited.
7) The fabrication and processing of steel skeleton must be carried out according to the drawings, so that the size and shape of each steel bar are accurate, and the assembly should be firm, accurate and complete. When the steel skeleton is skewed, twisted and deformed, it should be corrected in time, and then the binding buckle should be fastened, and the cross binding should be appropriately increased. In order to enhance the anti-deformation ability, diagonal tie bars and spot welding should be added to improve the strength and integrity of the skeleton.
8) The legs at the stigma shall be fixed with formwork and stirrups to prevent the legs from dislocation and deformation.
9) The angle and straight length of stirrup hook must meet the design and specification requirements, and the spacing size should be strictly controlled during assembly: the openings should be staggered, the binding should be firm, and loose force and deviation are strictly prohibited.
(10) In the binding of steel skeleton, lap binding should not be loose. In order to increase the integrity of the formed steel skeleton, arc welding spots can be used at appropriate positions of the skeleton.
(1 1) The mortar pad shall be reasonable and reliable. Steel bars can be erected with blocks buried with iron wires and tied to the outside of the steel skeleton. At the same time, in order to make the protective layer thickness accurate, the steel skeleton should be pulled to the template with iron wire, and the cushion block should be pressed tightly to strictly check the forming size of the steel bar.
(12) The skeleton with heavy weight should prevent the stirrup from deforming. If necessary, the structure should be strengthened, and its diameter is generally 10. The steel bar with the same diameter as the stirrup should be used as the reinforcement of the tie bar connection structure to enhance the integrity of the skeleton. Brace can be set every 3-5 stirrups.
(13) Install bending steel bars in cantilever steel bars in strict accordance with the structural stress direction, ensure the position of structural stress steel bars, and conduct inspection before pouring concrete, and adjust immediately if errors are found, so as to eliminate hidden dangers and prevent accidents.
(14) In order to prevent the displacement of double-layer mesh, brackets can be made of stirrups or steel bars, and the upper and lower mesh pieces can be tied together to form a whole. How to consider the accuracy and position of the mesh can be determined by hanging steel bars.
(15) Before assembling the steel skeleton, be familiar with the drawings, process the ingredient list and bill of materials one by one according to the drawings and the steel ingredient list, check whether the steel specifications are complete and accurate, whether the initial quantity meets the requirements of the drawings, and assemble according to the installation sequence and steps of the drawings to prevent steel leakage.
(3) Formwork engineering
Formwork engineering is an important guarantee for the quality of the main structure, which will directly affect the concrete quality and construction progress.
In the sub-project with the longest construction period and high cost in the main structure construction stage, the template preparation scheme must be comprehensively considered from the aspects of quality, progress, cost and constructability, and the investment in turnover materials and costs should be reduced on the premise of ensuring quality, safety and progress. The external structure of this project is complex and has an arc, but it is relatively regular and has many standard floors. The template is made of nine plywood templates. Stairs leave holes and other complex parts, the template adopts 18㎜ thick multi-layer plywood, the isolation agent is emulsified isolation agent, and the template support system adopts wooden columns to ensure the construction quality and progress of the template.
According to the requirements of the construction progress, this project has five sets of column formwork, five sets of beam and slab formwork and five sets of stair formwork, with sufficient quantities of formwork support.
General requirements for template preparation:
Ensure that the shape and size of the engineering structure and each part are correct relative to the campus, and have sufficient bearing capacity, stiffness and stability to meet the dynamic load generated during construction. The formwork is simple in structure, easy to assemble and disassemble, easy to bind steel bars, and the joints do not leak slurry. The contact surface between formwork surface and concrete should be coated with isolation agent. When designing templates and supports, measures should be taken to prevent the templates from deforming or bursting.
Formwork engineering is an important part of concrete structure engineering. Formwork and its supports must have sufficient strength, rigidity and stability, and can reliably bear the dead weight, lateral pressure and construction load of steel bars and concrete, so as to ensure that the geometric dimensions and mutual positions of engineering structures and components are correct, reasonable and simple, easy to assemble and disassemble, and tight without leakage.
Quality standard of template installation
Allowable deviation of project
5 The elevation of the upper surface of the shaft bottom die is 5.
Section size +4-5 stories high, vertical 3
The height difference between two adjacent plates is 2, and the surface is plane 5.
1, column and beam formwork construction:
The formwork of wall, column and beam adopts nine plywood, supported by wooden joists and columns, the vertical and horizontal spacing of cast-in-place beam and bearing frame and the number of Rachel bars are calculated and determined, and the arch is arched according to the specification requirements. When the beam and slab span is ≥4m, the bottom slab should be arched, with the range of11000-3/65444.
All templates shall be turned over by carpenters, and the turn-over diagram shall be drawn, which shall be rechecked by construction technicians. The formwork is prefabricated in the wooden shed workshop, assembled on site, and the cast-in-place beam-slab floor structure is formed, with the emphasis on the forming quality of beam-column joints.
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Summary of construction scheme of main structure of commercial pedestrian street building: acceptance of reinforcement in batches when entering the site. The acceptance content includes checking the appearance of the sign, and then taking samples according to relevant technical standards for mechanical performance test, which can only be used after passing the inspection.
The bottom plate and side formwork of the real estate data download beam should overlap with the column as a whole, and embedded joints must be set in the beam to avoid the shrinkage of the beam-column joint and ensure the accurate size of the beam-column joint. When clearing the frame, if the beam height exceeds 500, add a 12 opposite pulling screw (covered with plastic hard pipe) in the middle of the beam height.
2, stair template construction:
Nine splints are used for stair bottom formwork, and nine splints are used for step side formwork and step baffle. In order to make the step size accurate and angular, after concrete pouring, the step surface is closed with wooden boards. Because concrete pouring will produce jacking force on the formwork, it is necessary to strengthen the control of screw deformation during construction.
1, template removal
Demolition of formwork: it can only be dismantled if its own strength can ensure that the formwork will not be deformed or lose its edges and corners.
Demolition of horizontal formwork: when pouring concrete, make a group of test blocks, control the time of formwork removal and maintain them under the same conditions as the actual situation. According to the test results of test blocks and the size of structural span, the time of formwork removal is determined.
The removal of the template shall meet the following requirements:
First, the technical director must issue a demolition order before the demolition work can be carried out;
B, non-bearing template should be in the strength can guarantee the surface and edges from loss, can be removed.
C, plate and span; L75%% span L≥8M, r = 100% l Floor r ≥ 75%;
D, in the process of ripping, if it is found that the quality of concrete affects the safety of the structure, it should immediately stop the demolition and report it to the technical director for research and handling.
E, do a good job in the protection of concrete products.
After the formwork is dismantled, it should be cleaned, trimmed and coated with release agent immediately, and piled up in a centralized way for turnover.
4, template quality assurance and matters needing attention:
A, the template needs to meet the requirements of stiffness, strength and stability through design and calculation, and can reliably bear the construction load such as the weight and lateral pressure of the poured concrete.
B, before construction, carpentry sample drawing template diagram and node diagram, construction and technical review before construction. After the installation is completed, it will be accepted by relevant personnel of the project department.
C, template before construction, the team for written technical disclosure, form removal notice issued by the project builder.
D, cast concrete, there should be modes.
(4) Concrete engineering
1, concrete construction operation technology
A, before pouring concrete, must conduct a comprehensive inspection of the template, template sundry and construction waste must be cleaned up, template gap should be blocked more than 2MM, template and old concrete must be watered wet, construction joints must be set with cement slurry.
B, slab beam slab concrete, starting from one end with the "cement slurry method", the beam surface will be poured into a step, when the floor position is reached, and then pouring together with the floor concrete. The first layer of blanking is slow, so that the bottom of the beam can be fully vibrated before laying the second layer of material. Use the "grouting method" to wrap the slurry along the bottom of the beam with stones and push it forward to avoid touching the steel bars and embedded parts during vibration. The virtual paving thickness of floor slab casting is slightly larger than the slab thickness, and the slab vibrator is used for vertical casting, and the moving sign is continuously used to control the concrete slab thickness. After vibrating, the secondary surface is used to reduce shrinkage cracks of concrete.
C, the joint of new and old concrete of slab column is wetted with patented concrete, thick concrete is paved with cement mortar, and then poured in layers. The pouring height of each layer shall be less than 500, and no construction joints shall be left during concrete pouring. In case of special circumstances, construction joints shall be designed according to the design and specification requirements.
D, stair concrete pouring, stair section concrete pouring from bottom to top, first vibrated floor concrete, arrive at the step position dump truck pouring concrete together, constantly push up, and at any time with a wooden trowel smooth stair construction joints on the step surface. According to the situation, construction joints should be set perpendicular to the floor, and the self-protection of construction joints should be treated with column concrete before each concrete pouring.
E, using plug-in vibrating concrete pouring should be inserted quickly and pulled slowly, and the insertion points should be evenly distributed, moved point by point, and carried out in sequence, so as to achieve uniform vibrating, and the moving distance should not be greater than 1.5 (generally 300-400 meters) of the action radius of the vibrator. When pouring in layers, the upper concrete shall be vibrated and inserted into the lower concrete for more than 50㎜ to eliminate the joint between the two layers and ensure the moving distance of the flat vibrator.
F, when pouring concrete, send steel workers and carpenters to observe the steel bar and formwork, reserved holes and built-in parts, steel dowel for displacement or blockage, and so on and so forth. Stop pouring immediately after it is found, and finish dressing before the initial setting of the poured concrete.
G, after the completion of concrete pouring, it should be covered within 12 hours, and watered for curing. In summer, it should be cured with weak wet straw bags or plastic films, and the curing time should not be less than 7 days. For the structure mixed with retarder and permeability requirements, it should not be less than 14 days, and it should do a good job of anti-freezing and heat preservation in winter to avoid structural hidden dangers caused by freezing during initial setting of concrete.
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