CN115538772A - A closed formwork structure for cast-in-place stairs and its construction method - Google Patents

Abstract

The invention relates to a cast-in-place stair closed formwork structure and a construction method thereof, wherein the cast-in-place stair closed formwork structure comprises a support frame; the steel pipe is fixed at the upper end of the support frame, and the height of the steel pipe gradually rises from the lower platform beam to the upper platform beam; the square timber is supported on the steel pipe in a crossing way and is fixedly connected with the steel pipe; the bottom die is laid on the square timber and fixedly connected with the square timber; one end of the steel pipe group is fixed on the upper platform plate, and the lower end of the steel pipe group is fixed on the lower platform plate; each group of steel pipe groups comprises two steel pipes which are obliquely arranged and are parallel to the bottom die at intervals; the stepping unit comprises a stepping panel and a vertical plate, and the stepping unit forms an internal corner structure; the adjacent stepping units are fixed through a connecting structure, and the connecting structure is fixedly connected relative to the steel pipe group; the lower side of the side plate is fixedly connected with the bottom die, and the upper side of the side plate is fixedly connected with the steel pipe group in the left-right direction; a split bolt is arranged among the steel pipe group, the pedal plate and the bottom die; not only increases the support strength of the stepping unit and ensures the stepping size requirement after pouring.

Description

A closed formwork structure for cast-in-place stairs and its construction method

technical field

The invention belongs to the technical field of building construction, and in particular relates to a cast-in-situ stair closed formwork structure and a construction method thereof.

Background technique

There are two construction methods for cast-in-place stairs. First, during the pouring process, only the vertical slabs are supported, and the surface of the steps is closed manually. Each person can only construct one section of stairs at a time. This construction method takes a long time to pour, and It takes up mechanical time, and it is extremely inconvenient to vibrate the step surface, and it cannot be fully vibrated, which is prone to pockmarked stair treads and holes, which makes the pouring quality of the cast-in-place stairs poor. The second is to adopt a closed formwork structure. In this method, the support strength of the tread plate is low, and it is easy to step on it during the construction process, resulting in the problem of insufficient step height.

Contents of the invention

In view of this, the object of the present invention is to provide a cast-in-situ staircase closed formwork structure and its construction method to solve the problem that the tread plate support strength of the closed formwork method in the prior art is low, and it is easy to step on the tread plate, causing stepping. Highly inadequate technical issues.

In order to achieve the above object, the technical scheme adopted by a kind of cast-in-place staircase closed formwork structure of the present invention is:

A closed formwork structure for cast-in-situ stairs, comprising:

Support frame: supported between the upper platform beam and the lower platform beam, the lower end of the support frame is used to support the poured stairs, and the upper end of the support frame gradually rises from the lower platform beam to the upper platform beam;

Steel pipes: extending along the front and rear directions, the steel pipes are fixed on the upper end of the support frame, there are several steel pipes, and the height of the steel pipes gradually increases from the lower platform beam to the upper platform beam;

Square wood: installed obliquely between the upper and lower ladder beams, the square wood is cross-supported on the steel pipe and fixedly connected with the steel pipe;

Bottom form: lay on the square wood, and the bottom form is fixedly connected with the square wood;

Steel pipe group: there are at least two groups, one end of the steel pipe group is fixed on the upper platform, and the lower end of the steel pipe group is fixed on the lower platform;

Each group of steel pipe groups includes two steel pipes arranged obliquely and parallel to the bottom form at intervals;

Stepping unit: there are several groups, the stepping unit includes a tread plate and a vertical plate fixedly connected vertically with the tread plate, and the stepping unit forms an internal corner structure;

Adjacent step units are fixed through a connection structure, and the connection structure is fixedly connected to the steel pipe group;

Side plates: There are two pieces of side plates, which are installed obliquely between the upper platform beam and the lower platform beam. One end of the step unit is vertically attached to one of the side panels, and the other end of the step unit is vertically attached to the other side panel;

Pull bolts are arranged between the steel pipe group, the tread plate and the bottom mold.

Beneficial effects: adopting the closed formwork structure of the cast-in-place staircase of the present invention can reduce the honeycomb pockmarked surface of the staircase and the phenomenon that the vibration is not compact, the whole process of construction is controllable, and the cross-sectional size of the staircase is greatly guaranteed. Reduce the impact of construction on the quality of the building, reduce the risk of leakage and cracks on the board surface, and improve the construction quality.

During the construction process, it is possible to reduce the multiple positioning of the stair treads during the construction process. Once the positive angle of the step is positioned, the subsequent steps can be installed. It is more convenient to vibrate during the pouring process, which greatly improves the work efficiency of workers.

The step unit is directly connected to the steel pipe group, which not only increases the support strength of the step unit, but also the formwork structure can be used as a temporary construction staircase during the construction process, and the tread plate of the step unit will not be easily tilted, ensuring the step size requirements after pouring.

Further, two support blocks are fixed on the back of the riser of the step unit, the support blocks are arranged at intervals up and down, the upper surface of the upper support block is flush with the upper end of the riser, and the lower surface of the lower support block is close to the upper surface of the tread plate. surface.

Beneficial effects: the setting of the support block can increase the support strength of the vertical board, and the upper support block of the lower support unit in the adjacent step unit can also form a support for the edge of the tread plate of the upper support unit, increasing the strength of the tread plate. Support strength.

Further, the connection structure is an angle steel adapted to the male angle formed at the connection of the adjacent step unit, the angle steel includes a vertical steel plate and a horizontal steel plate welded vertically to the vertical steel plate, and the horizontal steel plate is fixed on the upper support block and the upper support block of the lower step unit On the tread plate of the upper step unit, the vertical steel plate is fixed on the upper support block of the lower step unit, and the angle steel is fixed with studs, which can pass between the two steel pipes of the steel pipe group, and the studs are fitted with nuts To fix the angle steel relative to the steel pipe group.

Beneficial effects: the connection structure not only facilitates the fixing of the male corner of the adjacent step unit, but also enables the fixed connection of the step unit and the steel pipe group, thereby ensuring the installation strength of the step unit.

The upper side of the side plate and the adjacent steel pipe group are fixed by buckles.

Beneficial effect: ensure that the side slab will not be deformed when concrete is poured, thereby ensuring the quality of pouring the side of the staircase.

The support frame includes several vertical rods, the vertical rods are extended along the up and down direction, the upper ends of the vertical rods are fixed with brackets, and the vertical rods are arranged in several rows at intervals in the left and right directions, the upper ends of each row of vertical rods gradually rise, and each row of vertical rods The rod corresponds to a steel pipe.

Beneficial effect: the structure of the supporting frame is set reasonably.

The steel pipe group includes an inclined section, an upper horizontal section fixed at the upper end of the inclined section, and a lower horizontal section fixed at the lower end of the inclined section. The upper horizontal section is supported and fixed on the upper platform, and the lower horizontal section is supported and fixed on the lower platform.

Beneficial effects: the setting of the upper horizontal section and the lower horizontal section of the steel pipe group can facilitate the fixing of the steel pipe group.

A construction method for a cast-in-situ stair closed formwork structure, comprising the following steps:

S1: Set up the support frame;

S2: Lay steel pipes and square timber on the support frame;

S3: Fixed and inclined bottom form on the square timber;

S4: Bind the reinforcement mesh, and lay and fix the reinforcement mesh on the bottom form according to the drawing requirements;

S5: Fix the steel pipe group between the upper support platform and the lower support platform, so that the inclined section of the steel pipe group is arranged in parallel with the bottom form;

S6: Place the completed sets of step units on the steel bars and below the steel pipe sets;

S7: Fix the side plates on the left and right sides of the bottom mold, and make the lower side of the side plates vertically fixedly connected with the bottom mold, and mark the position of the positive angle of the step unit on the side plate, so as to facilitate the installation of the step unit in the next step;

S8: Install the step units one by one according to the gradient of the stairs;

First install the first vertical board on the lower platform beam for positioning, then adjust the completed step units in sequence, and support the tread plate of the step unit on the top surface of the first vertical board, so that the top surface of the first vertical board is aligned with the first vertical board. The upper surface of the upper support block supports the tread plate together, so that the tread plate of the step unit and the first vertical plate form an external angle, and the angle steel is placed at the external angle, and the stud of the angle steel passes through the gap between the two steel bars of the steel bar group. When the external corner position is consistent with the external corner position of the step unit marked on the side plate, fix the stud relative to the reinforcement group with bolts; then fix other step units relative to the reinforcement group from bottom to top;

S9: Fix the upper sides of the side plates with buckles relative to the reinforcement group, so that the upper sides of the side plates are in close contact with the left and right sides of each pedal unit;

S10: Reinforce the pedal unit, install a tension bolt every three pedal units, so that the tension bolts pass through the steel pipe group, the tread plate, and the bottom mold in sequence;

S11: Concrete is poured. The concrete is poured from the bottom to the top of the stair section. During the pouring process, the vibrating pump vibrates evenly downward along the stair slab. It is advisable to observe a small amount of slurry flowing out of the vent hole during the pouring process;

S12: Remove the stair formwork: Now remove the half-stay bolts and buckles, then remove the steel pipe group, then remove the step units one by one, and then remove the two side panels; unscrew the nuts to pull out the steel pipes and square timber, and then remove the bottom form and support brackets removed.

Beneficial effects: adopting the construction method of the closed formwork support structure of the cast-in-place staircase of the present invention can reduce the honeycomb surface of the staircase and the phenomenon that the vibration is not dense, the whole construction process is controllable, and the cross-sectional size of the staircase is greatly guaranteed. Reduce the impact of construction on the quality of the building, reduce the risk of leakage and cracks on the board surface, and improve the construction quality.

During the construction process, it is possible to reduce the multiple positioning of the stair treads during the construction process. Once the positive angle of the step is positioned, the subsequent steps can be installed. It is more convenient to vibrate during the pouring process, which greatly improves the work efficiency of workers.

The step unit is directly connected to the steel pipe group, which not only increases the support strength of the step unit, but also the formwork structure can be used as a temporary construction staircase during the construction process, and the tread plate of the step unit will not be easily tilted, ensuring the step size requirements after pouring.

Further, before the S10 pedal unit is strengthened, vent holes are drilled on the tread plate, and two tread plates are spaced between the tread plates where two adjacent vent holes are located.

Beneficial effect: it is convenient to observe the pouring condition of concrete through the vent hole.

Description of drawings

Fig. 1 is the structural representation of a kind of cast-in-place staircase closed formwork structure of the present invention;

Fig. 2 is the side view of a kind of cast-in-place staircase closed formwork structure in Fig. 1;

Fig. 3 is a partial enlarged view of place A in Fig. 2;

Fig. 4 is the structural representation of the step unit of a kind of cast-in-place staircase closed formwork support structure in Fig. 1;

Fig. 5 is a structural schematic diagram of an angle steel of a closed formwork structure of a cast-in-place staircase in Fig. 1 .

Reference signs: 1-upper platform plate; 2-lower platform plate; 3-stepping unit; 4-angle steel; 5-steel pipe group; 6-side plate; 10-bottom mold; 11-pull bolts; 12-tread plate; 13-vertical plate; 14-upper support block; 15-lower support block; 16-horizontal steel plate; Screw piercing.

detailed description

A kind of cast-in-place staircase closed formwork structure of the present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments:

As shown in Figures 1 to 5, a closed formwork structure for cast-in-situ stairs of the present invention includes a support frame supported between the upper platform beam and the lower platform beam, and the lower end of the support frame is used to support the completed stairs. , the upper end of the support frame rises gradually from the lower platform beam to the upper platform beam. Specifically, the support frame includes several vertical rods 9, the vertical rods 9 are extended along the up and down direction, brackets are fixed on the upper ends of the vertical rods 9, and several rows of vertical rods 9 are arranged at intervals in the left and right direction, and the upper ends of each row of vertical rods 9 gradually raised. Define the width direction of the stairs as the left-right direction.

A steel pipe is fixed on the upper end of the support frame, and the steel pipe extends along the left and right directions, and there are several steel pipes, and the height of the steel pipe gradually increases from the lower platform beam to the upper platform beam; in the present embodiment, each row of uprights 9 corresponds to a steel pipe. There are square timbers cross-supported on the steel pipes, the square timbers are fixedly connected with the steel pipes, and the square timbers are arranged obliquely between the lower platform beam and the upper platform beam, so that the steel pipes and the square timbers form the supporting platform of the bottom mold 10 .

The bottom form 10 is laid on the square wood, and the bottom form 10 is fixedly connected with the square wood. On the base form 10, a steel mesh is obliquely bound, and steel pipe groups 5 are arranged at intervals above the steel mesh. At least two groups of steel pipe groups 5 are arranged in the left and right directions. One end of 5 is fixed on the upper platform plate 1, and the lower end of the steel pipe group 5 is fixed on the lower platform plate 2. Specifically, the steel pipe group 5 includes an inclined section, an upper horizontal section fixed at the upper end of the inclined section, and a lower section fixed at the lower end of the inclined section. In the horizontal section, the upper horizontal section is supported and fixed on the upper platform plate 1, and the lower horizontal section is supported and fixed on the lower platform platform; the inclined section is two steel pipes arranged obliquely and parallel to the bottom form 10 at intervals, and the two steel pipes pass through Relatively fixed, and the distance between the two steel pipes is kept at 800mm.

Several groups of step units 3 are arranged between the steel pipe group 5 and the steel mesh. The step unit 3 is a prefabricated component. The step unit 3 includes a tread plate 12 and a vertical plate 13 vertically fixedly connected to the tread plate 12. The step unit 3 forms a negative angle. Structure, in this embodiment, the length of the riser 13 is the width of the stair treads, the width of the riser 13 is the height of the stair steps, the riser 13 is a smooth and tidy formwork, and two support blocks are fixed on the back of the board, and the support blocks are arranged at intervals up and down , the upper surface of the upper support block 14 is flush with the upper end of the riser 13 , and the lower surface of the lower support block 15 is close to the upper surface of the tread plate 12 . The length of the step panel is the width of the stair step, and the width of the step panel 12 is the sum of the stair tread surface, the thickness of the riser, and the thickness of the upper support block 14, and the step panel 12 is selected as a smooth and tidy formwork. The tread plate 12 and the riser 13 are perpendicular to each other and fixed by nails.

Adjacent step units 3 are fixed by a connecting structure, and the connecting structure is fixedly connected to the steel pipe group 5; the connecting structure is an angle steel 4 adapted to the male angle formed at the connection of the adjacent step unit 3, and the angle steel 4 includes vertical steel plates 18 and vertical Steel plate 18 vertically welded horizontal steel plate 16, horizontal steel plate 16 is fixed on the upper support block 14 of the step unit 3 below and the tread plate 12 of the step unit 3 above, and the vertical steel plate 18 is fixed on the upper support block 14 of the step unit 3 below, A stud 17 is fixedly arranged on the angle steel 4 , and the stud 17 can pass between two steel pipes of the steel pipe group 5 . In order to facilitate the fixing of the angle steel 4 and the step unit 3 , in this embodiment, the vertical steel plate 18 and the horizontal steel plate 16 are respectively provided with screw holes 19 .

The left and right sides of the step unit 3 are respectively provided with side plates 6, the side plates 6 are obliquely arranged between the upper platform beam and the lower platform beam, the lower side of the side plate 6 is fixedly connected with the bottom mold 10, and the upper side of the side plate 6 In the left and right directions, it is fixedly connected to the steel pipe group 5, so that one end of the step unit 3 is vertically attached to one of the side plates 6, and the other end of the step unit 3 is vertically attached to the other side plate 6; in this embodiment, The upper side of the side plate 6 and the adjacent steel pipe group 5 are fixed by a buckle 7, and the buckle 7 is specifically a step-by-step tightening structure commonly used in building construction. The upper side of the left plate is fixed on the steel pipe group 5 on the left side by a step-by-step tight structure, and the upper side of the right side plate is fixed on the right steel pipe group 5 by a step-by-step tight structure.

Between the steel pipe group 5 , the tread plate 12 , and the bottom mold 10 are provided with pull bolts 11 , and the pull bolts 11 are arranged every three steps. Drill vent holes 8 on the tread plate 12, two tread plates 12 are separated between the tread plates 12 where two adjacent vent holes 8 are located, and two vent holes 8 with a diameter of about 1 cm are drilled on the tread plate 12, which should not be too large , easy to ooze, and not too small, and air bubbles will be generated if the exhaust is insufficient.

A construction method for a cast-in-situ stair closed formwork structure, comprising the following steps:

S1: Set up the support frame;

S2: Lay steel pipes and square timber on the support frame;

S3: the base form 10 fixedly inclined on the square timber;

S4: Binding the reinforcement mesh, laying and fixing the reinforcement mesh on the bottom form 10 according to the drawing requirements;

S5: Fix the steel pipe group 5 between the upper support platform and the lower support platform, so that the inclined section of the steel pipe group 5 is arranged in parallel with the bottom mold 10;

S6: Place several sets of step units 3 that have been fabricated on the top of the steel bars and below the steel pipe set 5;

S7: Fix the side plate 6 on the left and right sides of the bottom mold 10, and make the lower side of the side plate 6 vertically fixedly connected with the bottom mold 10, and mark the male corner position of the step unit 3 on the side plate 6 to facilitate the next step of installation step unit 3;

S8: Install step units 3 one by one according to the gradient of the stairs;

First install the first vertical plate on the lower platform beam for positioning, then adjust the finished step unit 3 in sequence, and support the tread plate 12 of the step unit 3 on the top surface of the first vertical plate, so that the top surface of the first vertical plate is in line with the first vertical plate. The upper surface of the upper support block 14 of a vertical board supports the tread plate 12 together, so that the tread plate 12 of the step unit 3 forms an external angle with the first vertical plate, and the angle steel 4 is placed at the external angle, and the studs of the angle steel 4 Pass through the gap between the two reinforcing bars of the reinforcing bar group. When the position of the male corner is consistent with the position of the male corner of the stepping unit 3 marked on the side plate 6, fix the stud 17 relative to the reinforcing bar group with nuts; fixed relative to the rebar group;

S9: Fix the upper sides of the side plates 6 with buckles 7 relative to the reinforcement group, so that the upper sides of the side plates 6 are in close contact with the left and right sides of each pedal unit;

S10: Reinforce the pedal unit, install a pair of tension bolts 11 every three pedal units, so that the tension bolts 11 pass through the steel pipe group 5, the tread plate 12, and the bottom mold 10 in sequence;

Before the reinforcement of the S10 pedal unit, drill vent holes 8 on the tread plate 12, and space two tread plates 12 between the tread plates 12 where two adjacent vent holes 8 are located;

S11: Concrete is poured from the bottom to the top of the stair section. During the pouring process, the vibrating pump vibrates evenly downward along the stair slab. During the pouring process, it is advisable to observe a small amount of slurry flowing out of the vent hole 8;

S12: Remove the stair formwork: first remove the pull bolts 11 and buckles 7, then remove the steel pipe group 5, then remove the step units 3 one by one, and then remove the two side plates 6; unscrew the nuts and take out the steel pipes and square timber , and then the bottom form 10 and the support frame are removed.

The cast-in-place stair closed formwork structure and construction method thereof of the present invention can reduce the phenomenon of stair honeycomb pockmarking and vibrating not compacted, the whole process of construction is controllable, and the cross-sectional size of the stairway is greatly guaranteed. Reduce the impact of construction on the quality of the building, reduce the risk of leakage and cracks on the board surface, and improve the construction quality.

During the construction process, it is possible to reduce the multiple positioning of the stair treads during the construction process. Once the positive angle of the step is positioned, the subsequent steps can be installed. It is more convenient to vibrate during the pouring process, which greatly improves the work efficiency of workers.

Each step unit 3 is directly connected to the steel pipe group 5 through the angle steel 4, which not only increases the supporting strength of the step unit 3, but also increases the strength of the step unit 3. The riser 13 that is provided with supporting block in the step unit 3 can support the edge of the step plate 12, and the formwork structure in the construction process can be used as a temporary construction staircase, even if construction workers pass through the formwork, the step unit 3 The tread plate 12 will not easily tilt, ensuring the step size requirement after pouring.

In addition, the present invention creatively uses the bottom mold 10 to be supported by the support frame, the step unit 3 is hoisted through the steel pipe group 5, and the side plate 6 is not only fixed on the bottom mold 10, but also fixed with the steel pipe group 5 through buckles, and, in the steel pipe group 5. There is a pull bolt 11 between the tread plate 12 and the bottom form 10, which ensures that the formwork structure has a strong structural strength, so that the formwork structure has a strong structural strength when it is used as a staircase. When used as a template for pouring stairs, it not only has high construction efficiency, but also has high pouring quality.

In the above embodiment, two support blocks are fixed on the back of the riser 13 of the stepping unit, and the support blocks are arranged at intervals up and down; in other embodiments, the support block may not be provided, or only one support block may be provided.

In the above embodiments, the connecting structure is an angle steel adapted to the male angle formed at the connection of adjacent step units. In other embodiments, the connecting structure can also be in other structural forms.

In the above-mentioned embodiment, the upper side of the side plate and the adjacent steel pipe group are fixed by buckles. In other embodiments, the buckle may not be provided. At this time, the two side plates are relatively fixed by pull bolts.

In the above embodiment, the support frame includes several vertical rods, the vertical rods are extended along the vertical direction, the upper ends of the vertical rods are fixed with brackets, and the vertical rods are arranged in several rows at intervals in the left and right directions, and the upper ends of each row of vertical rods are gradually raised. High, each row of vertical rods corresponds to a steel pipe; in other embodiments, the support frame can also be provided with horizontal bars fixed vertically to the vertical rods and oblique rods intersected with the vertical rods and horizontal rods to increase the structural strength of the support frame.

In the above embodiment, the steel pipe group includes an inclined section, an upper horizontal section fixed at the upper end of the inclined section, and a lower horizontal section fixed at the lower end of the inclined section, the upper horizontal section is supported and fixed on the upper platform, and the lower horizontal section is supported and fixed on the lower On the platform; in other embodiments, the upper horizontal section and the lower horizontal section may not be provided. At this time, the upper end of the inclined section is directly fixed and supported on the upper platform, and the lower end of the inclined section is directly fixed and supported on the lower platform.

Claims (8)

1. A closed formwork structure for cast-in-place stairs is characterized in that it comprises: Support frame: supported between the upper platform beam and the lower platform beam, the lower end of the support frame is used to support the poured stairs, and the upper end of the support frame gradually rises from the lower platform beam to the upper platform beam; Steel pipes: Extended along the left and right directions, the steel pipes are fixed on the upper end of the support frame, there are several steel pipes, and the height of the steel pipes gradually increases from the lower platform beam to the upper platform beam; Square wood: installed obliquely between the upper and lower ladder beams, the square wood is cross-supported on the steel pipe and fixedly connected with the steel pipe; Bottom form: lay on the square wood, and the bottom form is fixedly connected with the square wood; Steel pipe group: there are at least two groups, one end of the steel pipe group is fixed on the upper platform, and the lower end of the steel pipe group is fixed on the lower platform; Each group of steel pipe groups includes two steel pipes arranged obliquely and parallel to the bottom form at intervals; Stepping unit: there are several groups, the stepping unit includes a tread plate and a vertical plate fixedly connected vertically with the tread plate, and the stepping unit forms an internal corner structure; Adjacent step units are fixed through a connection structure, and the connection structure is fixedly connected to the steel pipe group; Side plates: There are two pieces of side plates, which are installed obliquely between the upper platform beam and the lower platform beam. One end of the step unit is vertically attached to one of the side panels, and the other end of the step unit is vertically attached to the other side panel; Pull bolts are arranged between the steel pipe group, the tread plate and the bottom mold. 2. A closed formwork structure for cast-in-place stairs according to claim 1, characterized in that two support blocks are fixed on the back of the riser of the step unit, the support blocks are arranged at intervals up and down, and the upper surface of the upper support block It is flush with the upper end of the riser, and the lower surface of the lower support block is close to the upper surface of the tread plate. 3. A closed formwork support structure for cast-in-place stairs according to claim 2, wherein the connection structure is an angle steel adapted to the male angle formed at the junction of the adjacent step unit, and the angle steel includes vertical steel plates and The vertical steel plate is vertically welded horizontal steel plate, the horizontal steel plate is fixed on the upper support block of the lower step unit and the tread plate of the upper step unit, the vertical steel plate is fixed on the upper support block of the lower step unit, and the angle steel is fixed with studs , the stud can pass between the two steel pipes of the steel pipe group, and the stud is fitted with a nut to fix the angle steel relative to the steel pipe group. 4. A closed formwork support structure for cast-in-place stairs according to any one of claims 1-3, characterized in that the upper side of the side plate and the adjacent steel pipe group are fixed by buckles. 5. A cast-in-place staircase closed formwork structure according to any one of claims 1-3, characterized in that the support frame includes several vertical rods, the vertical rods are extended in the vertical direction, and the upper ends of the vertical rods are fixed There are brackets, and several rows of uprights are arranged at intervals in the left and right directions, the upper ends of each row of uprights gradually rise, and each row of uprights corresponds to a steel pipe. 6. A closed formwork support structure for cast-in-situ stairs according to any one of claims 1-3, wherein the steel pipe group includes an inclined section, an upper horizontal section fixed at the upper end of the inclined section, and an upper horizontal section fixed at the inclined section. For the lower horizontal section at the lower end of the section, the upper horizontal section is supported and fixed on the upper platform, and the lower horizontal section is supported and fixed on the lower platform. 7. A construction method for a cast-in-situ stair closed formwork structure, characterized in that it comprises the following steps: S1: Set up the support frame; S2: Lay steel pipes and square timber on the support frame; S3: Fixed and inclined bottom form on the square timber; S4: Bind the reinforcement mesh, and lay and fix the reinforcement mesh on the bottom form according to the drawing requirements; S5: Fix the steel pipe group between the upper support platform and the lower support platform, so that the inclined section of the steel pipe group is arranged in parallel with the bottom form; S6: Place the completed sets of step units on the steel bars and below the steel pipe sets; S7: Fix the side panels on the left and right sides of the bottom mold, and make the lower side of the side panels vertically fixedly connected with the bottom mold, and mark the position of the positive angle of the step unit on the side panel, so as to facilitate the installation of the step unit in the next step; S8: Install the step units one by one according to the gradient of the stairs; First install the first vertical board on the lower platform beam for positioning, then adjust the completed step units in sequence, and support the tread plate of the step unit on the top surface of the first vertical board, so that the top surface of the first vertical board is aligned with the first vertical board. The upper surface of the upper support block supports the tread plate together, so that the tread plate of the step unit and the first vertical plate form an external angle, and the angle steel is placed at the external angle, and the stud of the angle steel passes through the gap between the two steel bars of the steel bar group. When the external corner position is consistent with the external corner position of the step unit marked on the side plate, fix the stud relative to the reinforcement group with bolts; then fix other step units relative to the reinforcement group from bottom to top; S9: Fix the upper sides of the side plates with buckles relative to the reinforcement group, so that the upper sides of the side plates are in close contact with the left and right sides of each pedal unit; S10: Reinforce the pedal unit, install a tension bolt every three pedal units, so that the tension bolts pass through the steel pipe group, the tread plate, and the bottom mold in sequence; S11: Pouring concrete, the concrete is poured from the bottom to the top of the stair section, and the vibrating pump vibrates evenly downward along the stair slab during the pouring process; S12: Remove the stair formwork: Now remove the half-stay bolts and buckles, then remove the steel pipe group, then remove the step units one by one, and then remove the two side panels; unscrew the nuts to pull out the steel pipes and square timber, and then remove the bottom form and support brackets removed. 8. The construction method of a closed formwork structure for cast-in-place stairs according to claim 7, characterized in that, before the S10 pedal unit is reinforced, air release holes are drilled on the tread plate, and the steps where two adjacent air release holes are located Two tread plates are spaced between the panels.

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