Reverse construction method of flat slab terrace structure

Abstract

The invention provides a flat slab terrace structure reverse construction method, which comprises the following steps of: welding a layer of frame column rib positioning corrugated pipe and a bearing platform steel bar before bearing platform concrete is poured, performing template reinforcement on a foundation short column and a column cap structure after the bearing platform concrete is poured, and mounting the column cap steel bar and a layer of structural slab column cap area reserved steel bar; then, first-layer frame column foundation part grouting, frame column rib inserting, hoisting and concrete pouring are conducted; hoisting a two-layer structure precast beam, paving a steel bar truss floor support plate and constructing floor slab reinforced concrete; and finally, the first-layer structural slab is constructed again while the second-layer frame columns are constructed. According to the method, the damage of construction machinery such as a truck crane and a beam transporting flat car to the first-layer carborundum floor during hoisting operation of the two-layer structure is avoided, meanwhile, the equal-strength time of a concrete structure required by construction of the first-layer structure due to insufficient soil sources in a short time is avoided, the construction period is shortened, the operability is high, and the method is mature and reliable; the method is especially suitable for construction of a multi-layer assembly type structure factory building project.

Description

Technical Field

[0001] The invention belongs to the technical field of building construction, and in particular relates to a reverse construction method for a beamless floor slab structure. Background Art

[0002] With the continuous development of prefabricated structures, storage and logistics rooms have introduced the prestressed prefabricated beam overall hoisting system in large bridge projects into construction, improved the conventional frame system construction process, and changed the second floor from a cast-in-place structure to a prefabricated structure system. The first floor of a conventional factory building is a building floor constructed on the backfill layer. When hoisting the second floor structure, it is only necessary to backfill the earth to the bottom of the floor structure, and the hoisting operation is carried out on the backfill soil. However, due to the shortage of soil sources, some construction projects cannot meet the conditions for earth backfilling operations in a short period of time. Therefore, a first-layer structural floor is constructed by setting up a bracket, which results in the hoisting machinery operating on the first-layer structural board when the prefabricated beams of the second-layer assembly system are hoisted. There will be a problem that the finished product protection is difficult after the one-time molding of the diamond sand structure floor, and it is difficult to ensure that there is no color difference when repairing the damaged diamond sand surface layer. At the same time, there will be many problems such as the second-layer structure hoisting operation needs to wait for the completion of the construction of the first-layer structural board and reach the design strength before construction. In summary, how to solve the construction difficulties of one-time molding of a diamond sand floor and early insertion of the second-layer structure is a problem that needs to be solved urgently. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a reverse construction method for a beamless floor structure, which solves the problem of protecting the finished product after a layer of diamond sand structure floor is formed at one time, and also transforms the construction of the second floor into an independent system which is no longer restricted by the construction progress of the first floor structure.

[0004] The present invention achieves the above technical objectives through the following technical means.

[0005] A top-down construction method for a beamless floor structure comprises the following steps: Step 1: Construction preparation: organize construction personnel, optimize drawings, and conduct technical briefing; Step 2: Construction process simulation; Step 3: Install the corrugated pipe for positioning the reinforcement of the first-floor frame column; Step 4: pouring of foundation cap concrete; Step 5: Strengthen the foundation short columns and column cap formwork; Step 6: Install the column cap reinforcement and the reserved reinforcement in the column cap area of ​​the first-floor structural slab; Step 7: pouring concrete for foundation short columns and column caps; Step 8: Grouting of corrugated pipes for positioning reinforcement of frame columns on the first floor; Step 9: Hoisting of one layer of column reinforcement and large steel formwork; Step 10: Concrete pouring of the first-floor frame columns; Step 11: Hoisting of second-floor precast beams and steel truss floor decking; Step 12: Second layer slab reinforcement binding and concrete pouring; Step 13: Construction of one layer of structural slab.

[0006] Furthermore, the specific process of step 3 is as follows: Step 3.1: Select the foundation column foot node; Step 3.2: Clean the bellows to remove grease and cut into pieces. After cutting, seal the lower end temporarily with transparent tape. Step 3.3: Assemble and fix the steel frame of the corrugated pipe, and weld and fix the steel frame of the corrugated pipe to the steel bars of the foundation cap, wherein at least three positioning meshes are arranged on the upper, middle and lower parts of the corrugated pipe, and positioning angle bars are arranged at the corners, and are firmly fixed to the template; Step 3.4: Pre-embed the corrugated pipe body into the foundation pedestal and foundation short column area, and pre-embed the pull ring; insert the steel pipe into the corrugated pipe to protect the corrugated pipe from damage during the subsequent pouring and vibration of the foundation short column and column cap concrete, and seal it with tape.

[0007] Furthermore, the specific process of step 5 is as follows: Step 5.1: Expand the foundation short column template by 50mm on each side, and add wire mesh to strengthen the excessive protective layer; Step 5.2: Set up supporting poles at the bottom of the column cap formwork; Step 5.3: The 650mm thick foundation short column concrete from the bottom of the column cap template to the top of the first-floor structural slab uses a strength grade of C40, and the column cap concrete uses a strength grade of C35. Here, a quick-and-easy closing net is used for high and low grade interception. The interception range of the quick-and-easy closing net is a circle of 100mm wide around the first-floor frame column; Step 5.4: The back ribs of the column formwork are reinforced with square steel tubes.

[0008] Furthermore, in the step 7, high-grade foundation short column concrete is poured first, and two vibrating rods are used to simultaneously vibrate from two diagonally opposite points during the pouring process. After the pouring of the foundation short column concrete is completed, the low-grade column cap concrete is poured; after the pouring of the foundation short column and column cap concrete is completed and the concrete is initially set, the steel pipe in the corrugated pipe is pulled out, and the excess corrugated pipe is cut off. After the cutting is completed, the corrugated pipe is 5 cm higher than the surface of the foundation short column, and a matching cover is covered at the upper end of the corrugated pipe.

[0009] Furthermore, the specific process of step 8 is as follows: Step 8.1: Lofting the top line of the foundation short column; Step 8.2: Level the bottom of the column mold; use mortar to level the bottom of the column mold. The mortar of the leveling layer is strictly prohibited from entering the column section; Step 8.3: Set up the column formwork to fix the steel bars; plant two formwork fixing steel bars on each side of the column formwork section; Step 8.4: Grouting of the rebar holes; When grouting the rebar holes, grouting is done one hole at a time through a grouting duct connected to a special grouting material mixer truck. The grouting surface should be slightly lower than the hole mouth. The earliest start time of grouting to the completion of rebar insertion in the column should not exceed 30 minutes.

[0010] Furthermore, the specific process of step 9 is as follows: Step 9.1: Lifting the column formwork; the main hook and the auxiliary hook rise simultaneously to lift the column formwork to a certain height from the ground, and the main hook is lifted to lift the column formwork to a vertical state. To avoid collision between the steel wire and the tool-type guardrail, etc., the main hook is hung with a shoulder pole to connect with the upper end of the column formwork; Step 9.2: Insert the steel cage into the grouting hole; multiple people cooperate to insert the steel cage into the hole filled with grout and place it in the center of the grouting hole; Step 9.3: Fix the column formwork and adjust the verticality; use a theodolite or a plumb bob hung on the column formwork to check the verticality, adjust the tensioners in each direction according to the verticality, and tighten the tensioners after ensuring the verticality of the column formwork; the steel wire rope of the middle column is fixed to the embedded hooks at the surrounding pedestals, and the side columns and corner columns are fixed to the temporary road surface in addition to the embedded hooks at the pedestals, and the hooks are fixed with expansion bolts on the pavement.

[0011] Furthermore, the specific process of step 10 is as follows: Step 10.1: Binding of conduit: Bind a hose to the end of the concrete pump pipe to extend it; Step 10.2: Concrete pouring: The pump pipe inserted into the reserved space is slowly lifted while pouring, and vibrated with two vibrators; Step 10.3: Construction of beam pads on top of columns; Use wooden formwork or customized steel formwork to make beam pad templates, and pour concrete for beam pads at the same time as the frame columns of the first floor; Step 10.4: Verticality review.

[0012] Furthermore, the specific process of step 11 is as follows: Step 11.1: When the second-floor precast beam is hoisted inside the span, a crawler crane of more than 50t is used for installation; when it is hoisted outside the span, a crawler crane of more than 85t is used for installation; Step 11.2: When hoisting, install the main beam first, then the secondary frame beam and the secondary beam, and ensure that the beam shelving length is not less than 150mm; when hoisting, the angle between the wire rope and the horizontal is ≥60°; Step 11.3: Review the installation dimensions of the second-floor precast beams, including the beam end shelving length, verticality, and beam spacing; Step 11.4: After the frame beam is installed, take temporary reinforcement measures; Step 11.5: Paste foam tape; ensure that the edge of the steel decking of the secondary beam is flat, clean and remove dust, and paste foam tape on the shelf surface, beam-column nodes, and the connection between the wooden formwork and the steel truss floor decking between the primary and secondary beams to prevent leakage when pouring the floor slab; Step 11.6: Lay the steel truss floor decking; when laying the steel truss floor decking, install the splicing buckles on the edge of the steel truss floor decking in place, and drive self-tapping screws at the splicing buckles to strengthen the connection and integrity between the steel truss floor decking; when laying the steel truss floor decking, set no less than 3 self-tapping screws between the plates, ensure the shelving length during construction, and ensure that the vertical reinforcement is placed on the secondary beam protection layer.

[0013] Furthermore, the specific process of step 12 is as follows: Step 12.1: Tie up the reinforcement of the second floor slab and pre-embed water and electricity; hoist and transport the steel bars that have been laid down to the floor, and install the negative reinforcement of the main beam, secondary frame beam and the upper part of the secondary beam according to the design drawings and specifications. When there are many negative reinforcements on the secondary frame beam and the main beam, tie them according to the T-section; tie up the bottom reinforcement along the direction of the steel truss according to the drawings, and tie up the bottom distribution reinforcement and additional reinforcement in the other direction; reserve and embed the wire box according to the drawings of water, electricity and fire protection, and be careful not to damage the steel bars during construction; tie up the surface reinforcement and the additional reinforcement along the direction of the steel grid according to the drawings, and tie up the upper distribution reinforcement and additional reinforcement in the other direction, and tie up the additional distribution reinforcement at the upper part of the shelving place; Step 12.2: Concrete pouring; Use a laser leveling machine to vibrate and roughly level the floor in a timely manner during pouring; During the concrete pouring process, send two construction surveyors to be responsible for on-site tracking and verification of the elevation to ensure that the horizontal elevation of the concrete meets the design requirements; When pouring concrete, use a vibrating rod to vibrate it fully; Considering the load-bearing capacity of the steel truss floor deck, use a light laser leveling machine for leveling.

[0014] Furthermore, the specific process of step 13 is as follows: Step 13.1: The reinforced concrete construction of the first floor structural slab is the same as that of the second floor structural slab; Step 13.2: When the floor surface begins to harden, sprinkle diamond sand, and use a mechanical trowel equipped with a metal blade to polish and calender it. Repeat the operation several times. Construction workers wear soft flat shoes to avoid damaging the surface. Fine corners are manually calendered. Step 13.3: Carry out water curing on the polished wear-resistant floor.

[0015] The present invention has the following beneficial effects: It is mainly used for the reverse construction of the first-layer structural floor of a multi-story factory building after the upper main structure is completed. It solves the problem of protecting the finished product after the first-layer corundum structural floor is formed once. At the same time, it also transforms the construction of the second layer into an independent system and is no longer subject to the construction progress of the first layer structure. The construction method provided by the present invention avoids the damage of the first layer of corundum floor by construction machinery such as car cranes and beam transport flatbed trucks during the hoisting operation of the second-layer structure. At the same time, it avoids the strong time required for the concrete structure of the first layer structure construction due to insufficient soil source in a short period of time, thereby shortening the construction period. This technology is highly operational, mature and reliable, especially in the construction of multi-story prefabricated structural factory projects, the advantages are more obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the reverse construction flow chart of the beamless floor structure slab.

[0017] Figure 2 This is a schematic diagram of the hoisting of the first-floor frame columns.

[0018] Figure 3 This is a schematic diagram of the hoisting of the second-floor precast beams.

[0019] Figure 4 It is a cross-sectional view of the fixed node of the main reinforcement corrugated tube of the frame column.

[0020] Figure 5 It is a plan view of the positioning mesh nodes.

[0021] Figure 6 It is a plan view of the slab-column node of a single floor.

[0022] Figure 7 This is a cross-sectional view of a slab-column node.

[0023] Figure 8 It is a cross-sectional view of the second-floor truss floor decking paving node.

[0024] Fig. 9 It is a plan view of the node of a structural plate.

[0025] In the figure: 1. crawler crane; 2. first-floor frame column; 3. first-floor plate-column node; 4. precast beam; 5. positioning angle reinforcement; 6. positioning mesh; 7. foundation pedestal; 8. foundation short column; 9. corrugated pipe; 10. column cap; 11. column cap additional reinforcement; 12. Φ12@150 first-floor structural slab full-length upper reinforcement; 13. quick closing mesh; 14. hoop reinforcement; 15. column cap reinforcement; 16. steel truss floor deck; 17. second-floor slab reinforcement; 18. first-floor structural slab. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] Reference Figure 1 The top-down construction method of the beamless floor structure of the present invention specifically includes the following steps: Step 1: Construction preparation; Step 1.1: Establish a top-down construction team for beamless floor slabs and clarify the organizational structure and personnel division of labor; Step 1.2: Optimize according to the original design drawings. In view of the problem that the one-time finished product of the diamond sand structure floor is difficult to protect, and the second-layer structure hoisting operation needs to wait until the first-layer structure plate is completed and reaches the design strength before construction, the first-layer diamond sand structure floor is adjusted by adjusting the construction sequence and using the reverse method to prioritize the second-layer structure hoisting operation; Step 1.3: Carefully analyze the construction drawings and optimized drawings, understand the design intent and depth, and formulate a reverse construction plan for the structural floor slab suitable for on-site construction; Step 1.4: Based on the actual situation on site, the feasibility of the scheme and the quality after forming, the reverse construction process of the beamless floor structure slab is finally determined; Step 1.5: Provide technical briefing and pre-job technical training to all workers.

[0028] Step 2: Construction process simulation; A BIM model is established for construction model to simulate the entire reverse construction process of the beamless floor structure slab, to ensure the molding quality of the beamless floor structure slab throughout the construction process and to ensure the early interspersed construction of the second-floor structure.

[0029] Step 3: Reference Figure 4 , 5 As shown, the first-floor frame column 2 column reinforcement positioning corrugated pipe 9 is installed; Step 3.1: Selection of foundation column foot nodes; the bottom elevation of the column formwork leveling layer is the top elevation of the foundation short column 8, which is suitable for the bottom of columns of 800×800mm and above in the warehouse, and the corrugated pipe 9 is directly pre-buried to the top of the foundation short column 8; Step 3.2: Cutting the bellows 9; clean and remove grease from the bellows 9 before cutting, the cutting length is the anchor length + 15cm; after cutting, the lower end is temporarily sealed with transparent glue (the sealing length does not exceed 10cm) to prevent the poured concrete from entering the bellows 9; Step 3.3: The corrugated pipe 9 is assembled and fixed; according to the positioning diagram of the corrugated pipe 9, the steel bar skeleton of the corrugated pipe 9 is assembled and fixed, at least three Φ16 (i.e., 16mm in diameter) positioning meshes 6 are set at the top, middle and bottom, and four Φ12 positioning angle bars 5 are set at the corners. The spacing between the side positioning angle bars 5 is not greater than 500mm, and they are subsequently firmly fixed to the foundation short column 8 and the column cap 10 template; if the corrugated pipe 9 is displaced during the subsequent concrete pouring process, the position of the corrugated pipe 9 needs to be adjusted in time; Step 3.4: Pre-embed the corrugated pipe 9; pre-embed the corrugated pipe 9 as a whole into the area of ​​the foundation pedestal 7 and the foundation short column 8, and pre-embed the pull ring, which is made of round steel with a diameter of 14 mm, and is subsequently extended into the concrete and fixed with the steel bar; at the same time, insert the steel pipe into the corrugated pipe 9 to ensure that the corrugated pipe 9 is not damaged during the subsequent concrete pouring and vibration of the foundation short column 8 and the column cap 10, and seal it with tape.

[0030] Step 4: pouring concrete of foundation cap 7; The concrete pouring of foundation pedestal 7 is carried out in layers, and the concrete is vibrated by dragging along the pouring direction with an inserted vibrator, and the concrete thickness is checked with an iron ruler. After the vibration is completed, it is leveled with a wooden scraper, and then flattened and compacted with a wooden trowel after watering.

[0031] Step 5: Reference Figure 6 , 7 As shown in 9, the foundation short column 8 and the column cap 10 formwork are reinforced; Step 5.1: The foundation short column 8 needs to be enlarged by 50mm on each side because the corrugated tube 9 fixes the steel bars. The excessive protective layer needs to be reinforced with additional wire mesh; Step 5.2: Support poles need to be set up at the bottom of the column cap 10 template board, and the spacing between the support poles is 1200×1200mm; Step 5.3: The concrete strength of the 650mm thick foundation short column 8 from the bottom of the column cap 10 to the top of the first-floor structural slab 18 is C40, while the concrete strength of the column cap 10 is C35. Here, a quick-closed net 13 is required for high and low grade interception. The interception range of the quick-closed net 13 is a circle of 100mm width around the first-floor frame column 2; Step 5.4: The back ribs of the column formwork are made of square steel tubes, and the square and round buckles are reinforced at a spacing of 500mm.

[0032] Step 6: Reservation of steel bars in the column cap area of ​​the first-floor structural slab 18; Step 6.1: The plate reinforcement at the column cap has the same size and specifications as the column cap additional reinforcement 11. The length of the column cap additional reinforcement 11 is 500mm extending from the side of the column cap 10. The column cap 10 is also provided with Φ14@200 hoop reinforcement 14 and Φ16@150 column cap reinforcement 15. Step 6.2: After the reserved steel bars of the first-layer structural slab 18 pass through the foundation short column 8, a lap length is reserved, and the staggered length of the lap joints of two adjacent steel bars is 1.3LLE.

[0033] Step 7: pouring concrete for the foundation short column 8 and the column cap 10; Concrete pouring is to pour high-grade short foundation column 8 concrete first, and use two 50 vibrating rods to vibrate synchronously from two diagonally opposite points during the pouring process. After the short foundation column 8 concrete pouring is completed, the low-grade column cap 10 concrete is poured; After the concrete pouring of the foundation short column 8 and the column cap 10 is completed and the concrete has initially set, the steel pipe in the corrugated pipe 9 is pulled out and the excess corrugated pipe 9 is cut off. After the cutting, the corrugated pipe 9 should be 5 cm higher than the surface of the foundation short column 8. A matching cover is placed on the upper mouth of the corrugated pipe 9 to prevent garbage from entering the pipe and protect the finished corrugated pipe 9.

[0034] Step 8: Grouting of a layer of column reinforcement corrugated pipe 9; Step 8.1: Locate the top line of the foundation short column 8; pop out the column center line, column section edge line and control line; before installing the column formwork, make a final review of the foundation short column 8, mainly to review the elevation and coordinates, determine the position of the column formwork, and mark it with a marker pen to facilitate subsequent placement; Step 8.2: Level the bottom of the column mold; Use mortar to level the bottom of the column mold, the height is generally 50mm, and the mortar of the leveling layer is strictly prohibited from entering the column section; Step 8.3: Set up the column formwork to fix the steel bars; plant two template fixing steel bars on each side of the column formwork section, and the steel bar diameter is generally ≥14mm; Step 8.4: Grouting of the rebar insertion holes; When grouting the rebar insertion holes, grouting is done one hole at a time through a grouting duct connected to a special grouting material mixer truck (it is strictly forbidden to pour the grouting material so that it flows into the hole). The grouting surface is slightly lower than the hole mouth by 10 cm. The earliest start time of grouting to the completion of rebar insertion in the column shall not exceed 30 minutes.

[0035] Step 9: Hoisting of one layer of column reinforcement and large steel formwork; Step 9.1: Lifting the column formwork; the main hook and the auxiliary hook rise simultaneously to lift the column formwork to a certain height from the ground, and the main hook is lifted to lift the column formwork to a vertical state. To avoid collision between the steel wire and the tool-type guardrail, etc., the main hook is hung with a shoulder pole to connect with the upper end of the column formwork; Step 9.2: Insert the steel bars into the grouting holes; 3 to 4 people work together to insert the steel cage into the hole filled with grout, and try to make the steel bars in the center of the grouting hole; Step 9.3: The column form is fixed and adjusted for verticality; use a theodolite or a plumb bob hung on the column form to check the verticality and adjust the tensioners in each direction according to the verticality. After ensuring the verticality of the column, tighten the tensioners. The steel wire rope of the middle column is fixed to the pre-buried hooks at the surrounding pedestals. In addition to the pre-buried hooks at the pedestals, the side columns and corner columns can be fixed to the temporary road surface. Two M16*140 expansion bolts are used to fix the hooks on the road surface.

[0036] Step 10: Concrete pouring of first-floor frame column 2; Step 10.1: Binding of conduit: It is advisable to tie a hose extension at the end of the concrete pump pipe to ensure that it is firmly tied; Step 10.2: Concrete pouring; control the concrete slump to 180mm, and ensure that there is no segregation after the concrete pouring is completed; the pump pipe inserted into the reserved space is slowly lifted while pouring, and two 50-type vibrators with a length of 12m are used for vibrating; Step 10.3: Construction of beam pads at the top of columns; Use wooden formwork or customized steel formwork to pour concrete for beam pads, and pour them at the same time as the frame column 2 of the first floor. The control value of the top elevation of the beam pad is the elevation of the bottom of the beam minus the thickness of the mortar 10mm; Step 10.4: Verify verticality. After the concrete is poured, use a theodolite to check verticality. If the verticality changes, adjust it in time using the tensioner.

[0037] Step 11: Reference Figure 2 , 3 As shown in 8, the second-floor prefabricated beams 4 (including main beams, secondary frame beams, secondary beams, frame beams) and the steel truss floor decking slabs 16 are hoisted; Step 11.1: Crane positioning; when the second-floor precast beam 4 is lifted inside the span, a crawler crane 1 with a weight of more than 50 t is used for installation, and when it is lifted outside the span, a crawler crane 1 with a weight of more than 85 t is used for installation; Step 11.2: Hoisting into place; when hoisting, install the main beam first, then install the secondary frame beam and secondary beam, and ensure that the beam shelving length is not less than 150mm; when hoisting, the angle between the wire rope and the horizontal should be ≥60° and not less than 45°; Step 11.3: Check the installation dimensions; Check the installation dimensions of the second-floor precast beam 4, mainly including the beam end shelf length, verticality, and beam spacing; non-standard secondary beam spacing will cause the steel deck to need to be cut or the shelf size to be too small, which will waste labor or pose a safety hazard. Use a laser rangefinder to check the beam spacing with an error of ±5mm; Step 11.4: Temporary fixing measures: After the frame beam is installed, the stability is poor and temporary reinforcement measures are required to prevent it from being blown down by strong winds and causing safety accidents; Step 11.5: Paste foam tape; ensure that the edge of the steel decking plate of the secondary beam is flat, clean and remove dust, and paste foam tape on the shelf surface, beam-column nodes and the connection between the wooden formwork and the steel truss floor decking plate 16 between the primary and secondary beams to prevent leakage when pouring the floor slab; Step 11.6: Lay the steel truss floor decking 16; when installing the steel truss floor decking 16, workers must strictly implement safety protection measures, wear safety belts as required, and secure their lifelines; when laying the steel truss floor decking 16, the splicing buckles on the edges of the steel truss floor decking 16 must be installed in place, and self-tapping screws must be installed at the splicing buckles to strengthen the connection and integrity between the steel truss floor decking 16; when laying the steel truss floor decking 16, no less than 3 self-tapping screws must be installed between the boards, and the shelving length must be ensured during construction, and the vertical reinforcement must be ensured to be shelved on the secondary beam protective layer.

[0038] Step 12: Reference Figure 8 As shown, the second layer of slab reinforcement 17 is tied and concrete is poured; Step 12.1: Binding of the second-layer slab reinforcement 17 and pre-embedding of water and electricity; hoist and transport the steel bars to the floor, and install the negative reinforcement on the main beam, secondary frame beam and secondary beam according to the design drawings and specifications. When there are many negative reinforcements on the secondary frame beam and main beam, they can be tied according to the T-section; the bottom reinforcement is tied along the direction of the steel truss according to the drawings, and the bottom distribution reinforcement and additional reinforcement are tied in the other direction. Pre-embedding of the junction box is carried out according to the professional drawings of water, electricity and fire protection. Be careful not to damage the steel bars during construction; the surface reinforcement and surface reinforcement additional reinforcement are tied along the direction of the steel grid according to the drawings, and the upper distribution reinforcement and additional reinforcement are tied in the other direction, and the attached distribution reinforcement is tied on the upper part of the shelving place; Step 12.2: Concrete pouring; When pouring the floor, a laser leveling machine is used to vibrate and roughly level it in time; During the concrete pouring process, two construction surveyors are assigned to track and check the elevation on site to ensure that the horizontal elevation of the concrete meets the design requirements. The steel bars at the beam-column joints are densely arranged, and the steel strands are interlaced. When pouring, a vibrating rod should be used to vibrate them fully; Considering the load bearing capacity of the steel truss floor deck 16, a light laser leveling machine can be used for leveling.

[0039] Step 13: Construction of a layer of structural panels 18; Step 13.1: The reinforced concrete construction of the first-floor structural slab 18 is the same as that of the second-floor structural slab; Step 13.2: When the floor surface begins to harden, sprinkle diamond sand and polish it with a mechanical trowel equipped with a metal blade. Repeat the operation 3 to 4 times; (Construction workers must wear soft flat shoes to avoid damaging the surface) Manually polish the fine edges and corners; Step 13.3: Carry out water maintenance on the polished wear-resistant floor (mainly to prevent the evaporation of surface moisture and ensure the stable growth of the strength of the wear-resistant material). The maintenance time is 7 days.

[0040] The construction method of the first-layer structural slab is adopted, and the first-layer frame column 2 is constructed first, and the hoisting operation of the second-layer prefabricated structure is interspersed in advance. The construction order of the structure below ±0.000m is pile foundation → foundation pedestal 7 → foundation short column 8 → column cap 10 structure → a 100mm wide first-layer structural slab 18 around the first-layer frame column 2. Before pouring the pedestal concrete, the first-layer frame column 2 column reinforcement positioning corrugated pipe 9 is welded and fixed to the pedestal steel bar. After the pedestal concrete is poured, the foundation short column 8 and column cap 10 structure are reinforced with formwork, and the column cap steel bar and the reserved steel bar in the column cap area of ​​the first-layer structural slab are installed. After the column cap 10 and short column concrete are poured and reach a certain strength, the foundation part of the first-layer frame column 2 is grouted, the frame column is inserted, hoisted, and concrete poured. After the first-layer frame column 2 reaches the design strength, the second-layer structure prefabricated beam 4 is hoisted, the steel truss floor slab 16 is laid, and the floor slab reinforced concrete is constructed. Finally, while the second-layer frame column is being constructed, the construction of the first-layer structural slab 18 is returned. This construction method avoids the damage of the first-layer diamond sand floor by construction machinery such as truck cranes and beam transport flatbed trucks during the hoisting operation of the second-layer structure. At the same time, it avoids the strong time required for the concrete structure of the first-layer structure construction due to insufficient soil source in a short period of time, thus shortening the construction period. This technology is highly operable, mature and reliable, especially in the construction of multi-layer prefabricated structure factory projects, the advantages are more obvious.

[0041] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A top-down construction method for a beamless floor structure, characterized in that: The process includes the following: Step 1: Construction preparation: organize construction personnel, optimize drawings, and conduct technical briefing; Step 2: Construction process simulation; Step 3: Install the column reinforcement positioning corrugated pipe (9) of the first-floor frame column (2); Step 4: pouring concrete of foundation cap (7); Step 5: Reinforce the formwork of the foundation short column (8) and the column cap (10); Step 6: Install the column cap (10) reinforcement and the reserved reinforcement in the column cap area of ​​the first-layer structural slab (18); Step 7: pouring concrete for the foundation short column (8) and the column cap (10); Step 8: Grouting of the column reinforcement positioning corrugated pipe (9) of the first-floor frame column (2); Step 9: Hoisting of one layer of column reinforcement and large steel formwork; Step 10: Concrete pouring of the first-floor frame column (2); Step 11: hoisting the second-floor prefabricated beams (4) and the steel truss floor decking (16); Step 12: Binding of the second layer slab reinforcement (17) and pouring of concrete; Step 13: Construction of one structural slab (18).

2. The top-down construction method of the beamless floor structure according to claim 1 is characterized in that: The specific process of step 3 is as follows: Step 3.1: Select the foundation column foot node; Step 3.2: Clean the bellows (9) to remove grease and cut into pieces. After cutting, seal the lower end temporarily with transparent glue. Step 3.3: Assemble and fix the steel frame of the corrugated pipe (9), and weld and fix the steel frame of the corrugated pipe (9) to the steel bars of the foundation cap, wherein at least three positioning mesh sheets (6) are arranged at the top, middle and bottom of the corrugated pipe (9), and positioning angle bars (5) are arranged at the corners; Step 3.4: The corrugated pipe (9) is pre-buried in the foundation pedestal (7) and the foundation short column (8) area, and the pull ring is pre-buried at the same time; and a steel pipe is inserted into the corrugated pipe (9) to protect the corrugated pipe (9) from damage during the subsequent concrete pouring and vibration of the foundation short column (8) and the column cap (10), and the steel pipe is sealed with tape.

3. The top-down construction method of the beamless floor structure according to claim 1 is characterized in that: The specific process of step 5 is as follows: Step 5.1: The template of the foundation short column (8) is enlarged by 50 mm on each side, and steel wire mesh is added to strengthen the excessive protective layer; Step 5.2: Set up supporting poles at the bottom of the column cap (10) template; Step 5.3: The concrete of the 650mm thick foundation short column (8) from the bottom of the column cap (10) formwork plate to the top of the first-layer structural plate (18) is selected to have a strength grade of C40, and the concrete of the column cap (10) is selected to have a strength grade of C35. Here, a quick-closing net (13) is used for high and low grade interception. The interception range of the quick-closing net (13) is a circle of 100mm width around the first-layer frame column (2); Step 5.4: The back ribs of the column formwork are reinforced with square steel tubes.

4. The top-down construction method of the beamless floor structure according to claim 2 is characterized in that: In the step 7, the high-grade foundation short column (8) concrete is poured first, and two vibrating rods are used to synchronously vibrate from two diagonally opposite points during the pouring process. After the pouring of the foundation short column (8) concrete is completed, the low-grade column cap (10) concrete is poured. After the pouring of the foundation short column (8) and the column cap (10) concrete is completed and the concrete is initially set, the steel pipe in the corrugated pipe (9) is pulled out, and the excess corrugated pipe (9) is cut off. After the cutting is completed, the corrugated pipe (9) is 5 cm higher than the surface of the foundation short column (8), and a matching cover is covered at the upper end of the corrugated pipe (9).

5. The top-down construction method for a beamless floor structure according to claim 4 is characterized in that: The specific process of step 8 is as follows: Step 8.1: Lofting the top line of the foundation short column (8); Step 8.2: Use mortar to level the bottom of the column mold. The mortar of the leveling layer is strictly prohibited from entering the column section; Step 8.3: Set up the column formwork to fix the steel bars; plant two formwork fixing steel bars on each side of the column formwork section; Step 8.4: Grouting of the rebar holes; When grouting the rebar holes, grouting is done one hole at a time through a grouting duct connected to a special grouting material mixer truck. The grouting surface should be slightly lower than the hole mouth. The earliest start time of grouting to the completion of rebar insertion in the column should not exceed 30 minutes.

6. The top-down construction method of the beamless floor structure according to claim 5 is characterized in that: The specific process of step 9 is as follows: Step 9.1: Lifting the column formwork; the main hook and the auxiliary hook rise simultaneously to lift the column formwork to a certain height from the ground, and the main hook is lifted to lift the column formwork to a vertical state. To avoid collision between the steel wire and the tool-type guardrail, etc., the main hook is hung with a shoulder pole to connect with the upper end of the column formwork; Step 9.2: Insert the steel cage into the grouting hole; multiple people cooperate to insert the steel cage into the hole filled with grout and place it in the center of the grouting hole; Step 9.3: Fix the column formwork and adjust the verticality; use a theodolite or a plumb bob hung on the column formwork to check the verticality, adjust the tensioners in each direction according to the verticality, and tighten the tensioners after ensuring the verticality of the column formwork; the steel wire rope of the middle column is fixed to the embedded hooks at the surrounding pedestals, and the side columns and corner columns are fixed to the temporary road surface in addition to the embedded hooks at the pedestals, and the hooks are fixed with expansion bolts on the pavement.

7. The top-down construction method of the beamless floor structure according to claim 1 is characterized in that: The specific process of step 11 is as follows: Step 11.1: When the second-floor precast beam (4) is lifted inside the span, a crawler crane (1) with a weight of 50 t or more is used for installation; when the second-floor precast beam (4) is lifted outside the span, a crawler crane (1) with a weight of 85 t or more is used for installation; Step 11.2: When hoisting, install the main beam first, then the secondary frame beam and the secondary beam, and ensure that the beam shelving length is not less than 150mm; when hoisting, the angle between the wire rope and the horizontal is ≥60°; Step 11.3: Review the installation dimensions of the second-floor precast beam (4); Step 11.4: After the frame beam is installed, take temporary reinforcement measures; Step 11.5: Ensure that the edge of the steel decking of the secondary beam is flat, clean and dust-free, and stick foam tape on the mounting surface, beam-column joints, and the connection between the wooden formwork and the steel truss floor decking (16) between the primary and secondary beams to prevent leakage when pouring the floor slab; Step 11.6: When laying the steel truss floor deck (16), install the splicing buckles at the edges of the steel truss floor deck (16) in place, and drive self-tapping screws at the splicing buckles to strengthen the connection and integrity between the steel truss floor deck (16); when laying the steel truss floor deck (16), set no less than 3 self-tapping screws between the boards, ensure the shelving length during construction, and ensure that the vertical reinforcement is shelved on the secondary beam protection layer.

8. The top-down construction method of the beamless floor structure according to claim 7 is characterized in that: The specific process of step 12 is as follows: Step 12.1: Binding of second-layer slab reinforcement (17) and pre-embedding of water and electricity; hoist and transport the steel bars to the floor, and install the main beam, secondary frame beam and upper negative reinforcement of the secondary beam according to the design drawings and specifications. When there are many negative reinforcements on the secondary frame beam and main beam, bind them according to the T-section; bind the bottom reinforcement along the direction of the steel truss according to the drawings, and bind the bottom distribution reinforcement and additional reinforcement in the other direction; reserve and embed the junction box according to the water, electricity and fire protection drawings; bind the surface reinforcement and additional surface reinforcement along the direction of the steel grid according to the drawings, and bind the upper distribution reinforcement and additional reinforcement in the other direction, and bind the additional distribution reinforcement at the upper part of the shelving place; Step 12.2: Concrete pouring: When pouring the floor, vibrate it thoroughly with a vibrator and use a laser leveling machine for leveling.

9. The top-down construction method of the beamless floor structure according to claim 1 is characterized in that: The specific process of step 13 is as follows: Step 13.1: The reinforced concrete construction of the first-floor structural slab (18) is the same as that of the second-floor structural slab; Step 13.2: When the floor surface begins to harden, sprinkle diamond sand on it and polish it with a mechanical wiping disc equipped with a metal blade. Repeat the operation several times and polish the fine corners manually. Step 13.3: Carry out water curing on the polished wear-resistant floor.

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