An adjustable diaphragm formwork and its construction method

Abstract

The present invention discloses an adjustable diaphragm formwork and its construction method, which relates to the technical field of diaphragm formwork implementation. It includes two symmetrically arranged I-beams, and multiple stirrups are welded between the two I-beams. Two panels are arranged between the two I-beams. In the present invention, special-shaped angle steels are installed on the precast beam in advance with screws, and the formwork is clamped inside to ensure that the web position is closely attached without leakage of grout, and at the same time, it also serves as a chamfer formwork for the web position. Sponges are blocked between the bottom formwork and the side formwork to prevent leakage of grout. To prevent the formwork from deforming and shifting and ensure the dimensions of the components, all formworks are tightened with full-thread screws to prevent the formwork from bulging during concrete pouring. A 5-mm-thick and 20-mm-wide rubber band is used as a sealing strip for the formwork joints. After the formwork is installed and adjusted, if there are still gaps between the formwork and the I-beam, transparent sealant is used for plugging, but it should be noted that the sealant shall not enter the cross-section of the diaphragm beam.

Description

Technical Field

[0001] The present invention relates to the technical field of diaphragm formwork construction, and particularly relates to an adjustable diaphragm formwork and its construction method. Background Art

[0002] The precast T-beams of a bridge are composed of beam ribs, wing plates and diaphragms. After installation, the distance between two adjacent T-beams is 70 cm. Adjacent wing plates and diaphragms are connected by pouring concrete to meet the overall stress requirements. At present, there are mainly two methods for the construction of the in-situ cast section of the diaphragm (the pouring connection section between adjacent diaphragms). One is to support the bottom formwork by erecting a scaffold under the bridge and use the scaffold as an operation platform for construction pouring; the other is to hang the bottom formwork with iron wires and fix it on the bridge deck, and the construction workers carry out steel bar and formwork construction through a simple hanging basket. Among them, in the first method, the erection and removal of the scaffold take a long time and cost a lot; in the second method, due to the large height of the diaphragm, the binding force of the iron wire on the bottom formwork is limited, and it is easy to produce slurry leakage. In addition, the bottom of the diaphragm within the construction range is not protected, which poses a great safety hazard to pedestrians and traffic under the bridge. Moreover, the construction workers use a simple hanging basket for construction, which is very dangerous and cannot effectively guarantee their lives. Summary of the Invention

[0003] The purpose of the present invention is to provide an adjustable diaphragm formwork and its construction method to solve the following technical problems: the diaphragm has a large height, the binding force of the iron wire on the bottom formwork is limited, and it is easy to produce slurry leakage. In addition, the bottom of the diaphragm within the construction range is not protected, which poses a great safety hazard to pedestrians and traffic under the bridge. Moreover, the construction workers use a simple hanging basket for construction, which is very dangerous and cannot effectively guarantee their lives.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] An adjustable diaphragm formwork includes two symmetrically arranged I-beams. A plurality of stirrups are welded between the two I-beams. Two formwork panels are arranged between the two I-beams. Reverse threaded rods are arranged on the sides of the two formwork panels. A plurality of full-threaded screws are installed on the inner sides of the two formwork panels.

[0006] As a further scheme of the present invention: the reverse threaded rod includes a steel pipe. Threaded rods are arranged on both sides of the steel pipe. Reinforcing bolts are sleeved on the threaded rods. Lifting lugs are arranged on the threaded rods.

[0007] As a further scheme of the present invention: one side of the I-beam is provided with an 8-cm chamfer.

[0008] As a further scheme of the present invention: a construction method of an adjustable diaphragm formwork includes the following steps:

[0009] Step 1. Erection of the construction operation platform for the diaphragm wall: Lifting lugs are welded at the four corners for hoisting the operation platform. The lifting ropes are made of 12-mm steel wire ropes, and the operation platform is lifted to the construction height by a winch. Horizontally place 2 No. 10 I-beams on the top of the I-shaped beam as the carrying poles of the operation platform, and fix the operation platform with rope clamps.

[0010] Step 2. Construction of the diaphragm wall reinforcement: Connect the reserved ends of the beam body and the reinforcement of the middle diaphragm wall. Note that before connecting the reinforcement, first check the roughened surfaces of the two ends of the precast beam's diaphragm wall, re-roughen the connecting surfaces that are not roughened thoroughly, and remove the surface floating slurry. The number of stirrups set for one diaphragm wall is 17, with one set every 10 cm. The spacer blocks are arranged in a quincunx pattern, with no less than 4 per square meter. The installation of the reinforcement of the cast-in-place middle cross beam should correspond neatly with the reserved reinforcement of the precast beam. For those with insufficient or unconnectable lapping lengths of the reserved main reinforcement, all shall be welded with tie bars.

[0011] Step 3. Overall linear control of the diaphragm wall: The designed width of the diaphragm wall is 30 cm. Since the I-shaped beam is precast in the back yard, the position of the embedded sleeve will be offset during construction, and coupled with the influence of the installation accuracy of the beam erection, the reinforcement installation will exceed the designed width during reinforcement installation. Therefore, in order to ensure the overall linearity of the diaphragm wall construction, for those with severely offset individual reinforcements after connection, the width of the diaphragm wall is widened, and the widened width is 30 - 35 cm.

[0012] Step 4. Formwork installation:

[0013] Use a standardized steel formwork. The formwork panel is made of 6-mm thick steel plate, the stiffening transverse ribs are made of 8# channel steel with a spacing of 30 cm, and the formwork bottom plate is made of 8-mm thick steel plate. Connect two formwork panels through connecting plates with left and right screw rods. By screwing in the left and right screw rods, the panels can be pushed against both sides. The formwork panels are symmetrically fabricated, with 2 pieces in a set. Two sets are required for pouring one diaphragm wall, a total of 4 formwork panels and 1 bottom plate. Install special-shaped angle steels on the precast beam in advance with screws, and clamp the formwork inside to ensure close contact at the web position without leakage of slurry, and at the same time serve as the chamfer formwork at the web position. The side formwork is reinforced with full-threaded screw rods, butterfly clamps and double-row φ48 steel pipes, tightened with PVC hard plastic pipes, and four points are reinforced on each surface.

[0014] Lift the formwork and slowly lower it above the position to be installed. Manually push the formwork into place. When the bottom connection seam is aligned, the formwork stands steadily and is held vertically, fix it in time with positioning bolts, and make a rough adjustment of the position. The rough adjustment of the formwork is achieved by applying force with a tensioning hoist. After the position is basically adjusted, immediately install the connecting bolts, but do not tighten them too tightly to facilitate precise adjustment of the formwork position.

[0015] As a further solution of the present invention: It also includes Step 5. Concrete construction and curing:

[0016] Before the concrete is poured into the formwork, its performance should be checked. The slump should be 150 - 170 mm. During pouring, it should be horizontally stratified at 30 cm - 40 cm. The upper layer of concrete should be poured before the lower layer of concrete starts to set or can be remolded. A PZ30 inserted vibrator should be used for vibration. When vibrating, the moving distance should not exceed 1.5 times the working radius of the vibrator and should keep a certain distance from the side formwork. The vibrator should be inserted quickly and pulled out slowly, inserted 5 - 10 cm into the lower layer of concrete, and vibrated evenly. Each point should be vibrated until the concrete stops sinking, no bubbles emerge, and it becomes flat and oozes slurry. After vibration, the vibrator should be slowly pulled out. The pouring height of the end crossbeam concrete should be flush with the bottom of the beam slab. After the concrete reaches the initial setting, it should be cured in time. Curing should be carried out using geotextiles + curing barrels or sprinkler curing, and the curing period should not be less than 7 days to prevent the concrete surface from cracking due to high temperature.

[0017] As a further scheme of the present invention: In step one, the geometric dimensions of the operation platform are: 7.2 m × 1.7 m × 1.7 m; the operation platform is composed of two 14# channel steels as the main beams connecting four small operation platforms; the main beams are two continuous 14# channel steels, 7.2 meters long, and each small platform is composed of two 10# channel steels 1.7 meters long. The bottom of the small operation platform is fully covered with 3 mm checkered steel plates.

[0018] As a further scheme of the present invention: In step two, the steel bar binding sequence is to first weld the main bars. For the transverse N1 and N2 bars in the cross diaphragm, sleeve connections are used inside the main beam, and N3 is welded. The main bars are 9 φ28 bars and 33 φ12 bars; then hold the stirrups, and the stirrups are 17 φ10 bars; then bind the tie bars, and the tie bars are 364 φ10 bars; after the steel bars are bound, attention should be paid to straightening the pre-embedded No. 7 bars.

[0019] The beneficial effects of the present invention:

[0020] In the present invention, special-shaped angle steels are installed on the precast beam in advance using screws, and the formwork is clamped inside to ensure that the web position is closely attached and there is no leakage of slurry, and it also serves as the chamfer formwork for the web position. Sponges are used to block between the bottom formwork and the side formwork to prevent slurry leakage. To prevent the formwork from deforming and shifting and ensure the dimensions of the components, all-thread screws are used to tighten between the formworks to prevent the formwork from bulging during concrete pouring. The formwork joints are sealed with a 5 mm thick and 20 mm wide rubber band. After the formwork is installed and adjusted, if there are still gaps between the formwork and the I-beam, transparent sealant is used for sealing, but attention should be paid that the sealant does not enter the cross diaphragm section. Description of the Drawings

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] Figure 1 It is the front view structural schematic diagram of the cross diaphragm formwork of the present invention;

[0023] Figure 2It is a top view structural schematic diagram of the diaphragm formwork of the present invention;

[0024] Figure 3 It is a front view structural schematic diagram of the positive and negative screw rods of the present invention;

[0025] Figure 4 It is the present invention Figure 1 The enlarged structural schematic diagram of area A in it;

[0026] Figure 5 It is a front view structural schematic diagram of the diaphragm construction operation platform of the present invention;

[0027] Figure 6 It is a structural schematic diagram of the overall linear adjustment of the diaphragm of the present invention;

[0028] Figure 7 It is a structural schematic diagram of the winch lifting the formwork of the present invention.

[0029] In the figure: 1, I-beam; 2, stirrup; 3, panel; 4, full-thread screw rod; 5, positive and negative screw rod; 6, rubber band; 51, steel pipe; 52, reinforcement bolt; 53, screw rod; 54, lifting lug. Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] Please refer to Figure 1-7 As shown, the present invention is an adjustable diaphragm formwork, including two symmetrically arranged I-beams 1, and a plurality of stirrups 2 are welded between the two I-beams 1. Two panels 3 are arranged between the two I-beams 1, and positive and negative screw rods 5 are arranged on the sides of the two panels 3, and a plurality of full-thread screw rods 4 are installed on the inner sides of the two panels 3.

[0032] The positive and negative screw rod 5 includes a steel pipe 51, screw rods 53 are arranged on both sides of the steel pipe 51, a reinforcement bolt 52 is sleeved on the screw rod 53, and a lifting lug 54 is arranged on the screw rod 53.

[0033] The top plate width of the I-beam is 1.25 m, the bottom plate width is 1 m, the web thickness is 20 cm, and the center distance between the two beams is 2 m. The widest part of the diaphragm is 1.8 m and the narrowest part is 0.75 m, with a thickness of 30 cm. There are 8*8 mm chamfers on both sides of the middle diaphragm, an 8 cm chamfer on one side of the end diaphragm, and no chamfer on the other end.

[0034] The construction sequence of the precast I-beam diaphragm casting is as follows: erection of the operation platform → welding of the diaphragm steel bars → installation of the formwork → concrete pouring → formwork removal and concrete curing.

[0035] A construction method for an adjustable diaphragm formwork: includes the following steps:

[0036] Step 1: Erection of the diaphragm construction operation platform: The geometric dimensions of the operation platform are 7.2m × 1.7m × 1.7m; the operation platform is composed of two 14# channel steels as the main beams connecting four small operation platforms; the main beams are two continuous 14# channel steels, 7.2 meters long, and each small platform is composed of two 10# channel steels 1.7 meters long. The bottom of the small operation platform is fully covered with 3mm checkered steel plates, as Figure 5 shown;

[0037] Lifting lugs are welded at the four corners to lift the operation platform, and 12mm steel wire ropes are used as the lifting ropes. The operation platform is lifted to the construction height by a winch; two 10# I-beams are placed horizontally on the top of the I-beam as the crossbeams of the operation platform, and the operation platform is fixed with rope clamps;

[0038] Step 2: Diaphragm steel bar construction: Connect the reserved ends of the beam body and the steel bars of the middle diaphragm. Note that before connecting the steel bars, first check the chiseled surfaces of the diaphragms at both ends of the precast beam, and re-chisel the surfaces with incomplete chiseling to remove the surface floating slurry; the number of stirrups set for one diaphragm is 17, one every 10 cm, and the spacers are arranged in a plum blossom shape, with no less than 4 per square meter; the installation of the steel bars of the cast-in-place middle crossbeam should be neatly aligned with the reserved steel bars of the precast beam one by one. For those with insufficient or unconnectable lap lengths of the reserved main steel bars, all should be welded with tie bars;

[0039] The steel bar binding sequence is to first weld the main steel bars. The transverse N1 and N2 steel bars of the diaphragm are connected by sleeves inside the main beam, and N3 is welded. The main steel bars are 9 φ28 steel bars and 33 φ12 steel bars; then hold the stirrups, and the stirrups are 17 φ10 steel bars; then bind the tie bars, and the tie bars are 364 φ10 steel bars; after the steel bar binding is completed, pay attention to straightening the pre-embedded No. 7 steel bars; when binding the steel bars, pay attention to constructing according to the drawings. After the transverse steel bars N1 and N2 of the diaphragm are connected by sleeves inside the main beam and N3 is welded to form a whole, then pour the concrete.

[0040] Quality requirements for diaphragm steel bar construction:

[0041] ① The varieties, specifications and technical properties of steel bars, straight thread joints and welding electrodes shall meet the requirements of the design and relevant current national standards.

[0042] ② The main bars of the steel bars are connected by two methods: straight thread sleeve joints and welding. The steel bars should be kept straight. The length of the straight thread connection joints should meet the requirements of the design and specifications. The exposed thread teeth of the steel bars should not exceed 2 threads. The integrity and length of the thread at the joint should meet the requirements, and there should be no bending at the joint.

[0043] ③ Before connecting the main bars of the steel bars, a connection process test should be carried out under the on-site conditions. Only after the test is qualified can the formal production of the steel bars be carried out.

[0044] ④ The quantity of the steel bars meets the design requirements. There should be no cracks, rust, oil stains, welding slag and other contaminants on the surface of the steel bars. The joints of the main bars and the stirrups should not be in the same cross-section, and should be set at 50% of the same cross-section. The joint spacing and the number of joints of the same steel bar should meet the requirements of the design and construction technical specifications.

[0045] ⑤ When tying the stirrups, the wire should face the inside of the steel bar skeleton to prevent the wire from extending into the protective layer to form a corrosion channel.

[0046] ⑥ The protective layer of the diaphragm is controlled by using concrete mortar pads, which are arranged in a plum blossom shape. During the steel bar tying process, the installation of the steel bar protective layer pads should be done well.

[0047] ⑦ The finished steel bars are guaranteed to be straight and have accurate dimensions. The construction errors of their diameter, main bar spacing and stirrup spacing meet the specification requirements.

[0048] ⑧ The allowable deviation values for steel bar fabrication are shown in the following table:

[0049] Table 1 Allowable deviation values for steel bar fabrication

[0050] ;

[0051] Step 3: Overall linear control of the diaphragm: Since vehicles need to pass under the bridge in this project, the linear control of the diaphragm is particularly important. The overall linear control of the diaphragm is divided into two parts. First, the positions of the embedded sleeves for beam fabrication should meet the requirements of relevant specifications, and the installation positions of the I-beams should be accurate. Second, the "three-line method" is adopted, that is: the center line of the diaphragm, and the two side lines of the diaphragm. The welding of the diaphragm steel bars should be controlled as straight as possible. After the welding of the steel bars in one hole is completed, pull a string to observe whether the steel bars in each hole are on the same horizontal line. If there is a deviation, adjust the position of the steel bar with a larger deviation. When installing the formwork, try to install the formwork according to the straightened horizontal line, as Figure 6 shown;

[0052] The designed width of the diaphragm is 30 cm. Since the I-beams are precast in the backfield, the positions of the embedded sleeves will be offset during construction. Coupled with the influence of the installation accuracy of the girder erection, the width of the steel bar installation will exceed the designed width during construction. Therefore, in order to ensure the overall linearity of the diaphragm construction, for individual steel bars with serious offset after connection, the width of the diaphragm is appropriately widened. The widened width is generally between 30 and 35 cm according to the actual situation on site.

[0053] Step 4: Formwork installation:

[0054] Use a standardized steel formwork. The formwork panel is made of 6-mm-thick steel plate, and the stiffening transverse ribs are made of 8# channel steel with a spacing of 30 cm. The formwork bottom plate is made of 8-mm-thick steel plate. Two formwork panels are connected by using left- and right-handed screw rods through connecting plates. By screwing in the left- and right-handed screw rods, the formwork panels can be pushed against both sides. The formwork panels are symmetrically fabricated, with two pieces in a set. Two sets are required for pouring one diaphragm, with a total of four formwork panels and one bottom plate. Install special-shaped angle steels on the precast beam in advance with screws, and clamp the formwork inside to ensure that the web positions are closely attached without leakage of mortar, and at the same time serve as the chamfer formwork for the web positions. The side formwork is reinforced with full-thread screw rods, butterfly clamps, and double-row φ48 steel pipes, tightened with PVC hard plastic pipes, and four points are reinforced on each side.

[0055] The surface of the formwork should be kept smooth and free of deformation, and the joints should be tight. Strictly control the end face dimensions of the diaphragm according to the requirements of the design drawings. Plug the gap between the bottom formwork and the side formwork with sponge to prevent mortar leakage. To prevent the formwork from deforming and shifting and ensure the dimensions of the components, all formworks are tightened with full-thread screw rods to prevent the formwork from bulging during concrete pouring. After the formwork installation is completed, the position of the formwork should be kept accurate. When it is found that the formwork may exceed the allowable deviation, it should be corrected in time.

[0056] Lift the formwork and slowly lower it above the position to be installed. Manually push the formwork into place. When the bottom joint is aligned, the formwork stands stably and is held vertically, fix it with positioning bolts in time, and make a rough adjustment of the position. The rough adjustment of the formwork is achieved by applying force with a tensioning hoist. After the position is basically adjusted, immediately install the connecting bolts, but do not tighten them too tightly to facilitate the precise adjustment of the formwork position.

[0057] Formwork fabrication and acceptance

[0058] The diaphragm formwork is entrusted to a professional manufacturer for processing and fabrication. It should be assembled and debugged according to the design drawings and formwork numbers. After the diaphragm formwork is assembled, check whether the connection bolts, tie rods, and other connection positions are connected. During acceptance, relevant tools and instruments should be used for measurement to check whether the dimensions are consistent with those shown in the pier drawings and construction drawings.

[0059] Formwork panel treatment

[0060] After the formwork enters the site, the surface rust shall be removed. After each use of the formwork, it shall be cleaned after demoulding. All rust and mortar on the large formwork shall be thoroughly cleaned. The rust shall be ground off with sandpaper and wiped clean with cotton yarn. The mortar splashed on the large formwork and the joint between two formworks shall be removed with a flat chisel. Finally, a release agent shall be brushed on the formwork surface. Before each use of the formwork for each floor, it must be cleaned thoroughly and a non-oily release agent shall be brushed comprehensively, which can effectively protect the formwork, improve the demoulding performance and ensure the visual quality of the concrete.

[0061] For large steel formworks, a special oil release agent shall be used. The coating process and technology of the special board treatment release agent are publicly available. The selection of the release agent must be based on the formwork used. An oily release agent shall be used for steel formworks, and waste engine oil is prohibited. The release agent shall be coated evenly without omission. When brushing, use cotton yarn to brush off the floating oil to prevent running and sagging. After rain or snow, it should be repainted.

[0062] The purpose of brushing the release agent on the inner surface of the concrete formwork is to reduce the adhesion between the concrete and the formwork and make it easy to separate, so that the concrete will not be damaged during demoulding due to too low initial strength of the concrete, keep the concrete surface smooth, and at the same time protect the formwork, prevent its deformation or rust, facilitate cleaning and reduce the repair cost. Therefore, the release agent must meet the following requirements:

[0063] 1. Concrete release agent: Good demoulding performance During demoulding, it is required that the release agent can make the formwork separate from the concrete smoothly, keep the concrete surface smooth and flat, and the corners and edges intact.

[0064] 2. Easy to apply, quick to form a film and easy to clean after demoulding It is better that the release agent can be both brushed and sprayed, and it should form a film quickly (generally within 20 minutes) and be easy to remove after demoulding, so as not to affect the construction progress and the production rate of products.

[0065] 3. Does not affect the decorative effect of the concrete surface There are no impregnation marks or yellowing and discoloration left on the concrete surface.

[0066] 4. Does not contaminate the steel bars and is harmless to the concrete It does not affect the bond strength between the concrete and the steel bars, does not change the setting time of the concrete mixture, and should not contain substances harmful to the performance of the concrete.

[0067] 4. Formwork installation

[0068] After the reinforcement of the diaphragm is completed, use the hanging bracket and winch to lift and hold the formwork and place it at the installation position, and install the diaphragm formwork piece by piece, as Figure 7 shown;

[0069] The formwork is slowly lowered above the installation position, and the formwork is manually pushed into place. When the bottom joint is aligned, the formwork stands firm and is held vertically, it is fixed in time with positioning bolts, and rough adjustment of the position is carried out. The rough adjustment of the formwork is achieved by applying force with a tension hoist. After the position is basically adjusted, the connecting bolts are immediately installed, but do not tighten them too much to facilitate the precise adjustment of the formwork position.

[0070] 1. A 5-mm thick and 20-mm wide rubber band is used as a sealing strip for the formwork joint. After the formwork is installed and adjusted, if there are still gaps between the formwork and the I-beam, transparent sealant is used for plugging, but note that the sealant must not enter the cross diaphragm section.

[0071] 2. To prevent the formwork from sliding, the degree of formwork deformation should be checked before formwork installation. If there is deformation, it should be repaired and only installed after meeting the requirements.

[0072] 3. Check the tightening degree of the connecting bolts of the bottom formwork, and try to make the bottom formwork section close to the pier body as much as possible. If the bolts are loose, they should be tightened in time.

[0073] 4. During the concrete pouring process, pay attention to observing the formwork. If there is looseness or leakage of slurry, stop the pump slurry and continue construction only after the treatment is completed.

[0074] Key points of formwork installation:

[0075] 1. Control of slurry leakage and stoppage of slurry. At the panel and the beam web, a 5-mm thick rubber band and positive and negative screw rods can basically achieve no slurry leakage. For the horseshoe of the I-beam, double-sided tape or foam rubber is used to stop the slurry.

[0076] 2. Control of the offset between the two panels of the cross diaphragm. Because there is a 5-cm adjustment section left in the middle of the formwork design, special attention should be paid to controlling the offset size of the formwork during formwork installation.

[0077] It also includes Step Five, concrete construction and curing: The designed grade of the cross beam concrete is C50. The concrete is centrally mixed at the mixing plant and transported to the site by tank trucks. There are the following three pouring methods: 1. Lift a special concrete hopper to the position above the cross diaphragm through a winch and vibrate manually with an inserted vibrator; 2. Lift the concrete hopper to the position above the cross diaphragm for pouring by a truck crane; 3. Transport the concrete to the position above the cross diaphragm by a gantry crane; 4. Pour directly through a concrete pump.

[0078] Before the concrete is placed into the formwork, its performance should be checked. The slump should be 150 - 170 mm. During pouring, it should be horizontally stratified at 30 cm - 40 cm intervals. The upper layer of concrete should be poured before the lower layer of concrete starts to set or can be remolded. The PZ30 inserted vibrating rod is used for vibration. When vibrating, the moving distance should not exceed 1.5 times the working radius of the vibrating rod and should keep a certain distance from the side formwork. The vibrating rod should be "inserted quickly and pulled out slowly", inserted 5 - 10 cm into the lower layer of concrete, and vibrated evenly. Each point should be vibrated until the concrete stops sinking, stops bubbling, and becomes flat and oozes slurry. After vibration, the vibrating rod should be slowly pulled out. The pouring height of the end crossbeam concrete should be flush with the bottom of the beam and slab. After the concrete reaches the initial setting, it should be cured in time. Curing is carried out using geotextile + curing barrel or watering. The curing period should not be less than 7 days to prevent the concrete surface from cracking due to high temperature.

[0079] The above has described an embodiment of the present invention in detail, but the content described is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the present invention application should still fall within the scope covered by the patent of the present invention.

Claims

1. An adjustable diaphragm formwork, characterized in that, It includes two symmetrically arranged I-beams (1), and multiple stirrups (2) are welded between the two I-beams (1). There are two panels (3) arranged between the two I-beams (1). Reverse threads screws (5) are arranged on the sides of the two panels (3), and multiple full-thread screws (4) are installed on the inner sides of the two panels (3). The reverse threads screw (5) includes a steel pipe (51). Threaded rods (53) are arranged on both sides of the steel pipe (51). Reinforcing bolts (52) are sleeved on the threaded rods (53), and lifting lugs (54) are arranged on the threaded rods (53). One side of the I-beam (1) is provided with a chamfer with a length dimension of 8 cm.

2. The construction method of an adjustable diaphragm formwork according to claim 1, characterized in that It includes the following steps: Step 1: Erection of the construction operation platform for the transverse diaphragm: Lifting lugs are welded at the four corners for hoisting the operation platform. The lifting ropes are made of 12-mm steel wire ropes, and the operation platform is lifted to the construction height by a winch. Two No. 10 I-beams are horizontally placed on the top of the I-beams as the crossbeams of the operation platform, and the operation platform is fixed by rope clamps. Step 2: Construction of the transverse diaphragm steel bars: Connect the reserved ends of the beam body and the steel bars of the middle transverse diaphragm. Note that before connecting the steel bars, first check the roughened surfaces of the transverse diaphragms at both ends of the precast beam, re-roughen the connecting surfaces that are not roughened thoroughly, and remove the surface floating slurry. The number of stirrups arranged for one transverse diaphragm is 17, with one stirrup arranged every 10 cm. The spacer blocks are arranged in a plum blossom shape, with no less than 4 spacer blocks per square meter. The installation of the cast-in-place middle crossbeam steel bars should be neatly aligned with the reserved steel bars of the precast beam one by one. For the reserved main steel bars with insufficient lap length or unable to be connected, all should be welded with tie bars. Step 3: Overall linear control of the transverse diaphragm: The designed width of the transverse diaphragm is 30 cm. Since the I-beams are precast in the back field, the positions of the embedded sleeves will be offset during construction. Coupled with the influence of the installation accuracy of the erected beams, the steel bars will exceed the designed width during installation. Therefore, in order to ensure the overall linearity of the transverse diaphragm construction, for the individual steel bars that are severely offset after connection, the width of the transverse diaphragm is widened, and the widened width is 30 - 35 cm. Step 4: Formwork installation: A fixed-type steel formwork is adopted. The panel is made of 6-mm thick steel plate, the stiffening transverse ribs are made of 8# channel steel with a spacing of 30 cm, and the formwork bottom plate is made of 8-mm thick steel plate. The two panels are connected by reverse threads screws through connecting plates. By screwing in the reverse threads screws, the panels can be pushed against both sides. The panels are symmetrically manufactured, with 2 pieces in a set. Two sets are required for pouring one transverse diaphragm, with a total of 4 panel pieces and one bottom plate. Special-shaped angle steels are installed on the precast beam in advance with screws, and the formwork is clamped inside to ensure close contact at the web position without leakage of slurry, and at the same time, it also serves as the chamfer formwork at the web position. The side formwork is reinforced with full-thread screws, butterfly buttons and double-row φ48 steel pipes, and tightened with PVC hard plastic pipes. Four points are reinforced on each surface. The formwork is lifted and slowly lowered above the position to be installed. The formwork is manually pushed into place. When the bottom connection seams are aligned, the formwork stands stably and is held vertically, it is fixed in time with positioning bolts, and rough adjustment of the position is carried out. The rough adjustment of the formwork is achieved by applying force with a pulling hoist. After the position is basically adjusted, the connecting bolts are immediately installed, but not tightened too tightly for precise adjustment of the formwork position.

3. The construction method of an adjustable diaphragm formwork according to claim 2, characterized in that, It also includes Step 5: Concrete construction and curing: Before the concrete is poured into the formwork, its performance shall be checked. The slump shall be 150 - 170 mm. During pouring, horizontal layering shall be carried out at 30 cm - 40 cm. The upper layer of concrete shall be poured before the lower layer of concrete begins to set or can be remolded. The PZ30 inserted vibrating rod shall be used for vibration. When vibrating, the moving distance shall not exceed 1.5 times the working radius of the vibrating rod and shall keep a certain distance from the side formwork; the vibrating rod shall be "inserted quickly and pulled out slowly", inserted 5 - 10 cm into the lower layer of concrete, and vibrated evenly. Each point shall be vibrated until the concrete stops sinking, no bubbles emerge, and the surface is flat and slurry overflows. After vibration, the vibrating rod shall be slowly pulled out; the pouring height of the end crossbeam concrete shall be flush with the bottom of the beam slab; after the concrete reaches the initial setting, it shall be cured in time. The curing shall adopt geotextile + curing barrel or water spraying curing, and the curing period shall not be less than 7 days to prevent the concrete surface from cracking due to too high temperature.

4. The construction method of an adjustable diaphragm formwork according to claim 2, characterized in that, In Step 1, the geometric dimensions of the operating platform are: 7.2 m × 1.7 m × 1.7 m; the operating platform is connected to four small operating platforms by using two 14# channel steels as the main beams; the main beams are two continuous 14# channel steels, 7.2 meters long. Each small platform is composed of two 10# channel steels, 1.7 meters long. The bottom of the small operating platform is fully covered with 3 mm diamond pattern steel plates.

5. The construction method of an adjustable diaphragm formwork according to claim 2, characterized in that, In Step 2, the steel bar binding sequence is as follows: first, the main steel bars are welded. For the transverse N1 and N2 steel bars of the cross diaphragm, sleeve connections are used inside the main beam, and N3 is welded. The main steel bars are 9 φ28 steel bars and 33 φ12 steel bars; then, the stirrups are held. The stirrups are 17 φ10 steel bars; then, the tie bars are bound. The tie bars are 364 φ10 steel bars; after the steel bars are bound, attention shall be paid to straightening the pre-buried No. 7 steel bars in advance.

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