CN115976962A - Construction method for closure section of external stiff framework of cast-in-place box girder - Google Patents

Abstract

The invention relates to a construction method of a closure section of an external stiff framework of a cast-in-place box girder, which comprises the following steps: installing a bracket of the side span pier stud; constructing a side span cast-in-place section; mounting a hanging bracket for construction of a hanging basket at a closure section; installing a stiff framework; and (5) installing and pouring a closure section template system. The invention has the beneficial effects that: the stiff framework locks box girders on two sides of the closure section before the concrete of the closure section is poured, so that the concrete of the closure section is effectively prevented from cracking before prestress is applied; the error between the on-site water discharge and the concrete pouring amount is effectively controlled through the treatment of the bin dividing and valve dividing; erecting a side span cast-in-place section template support by utilizing a bracket; the construction speed is fast, the structural stability is high, the construction is safe and controllable, and the construction method has a plurality of construction advantages of high stability, high efficiency, high benefit and the like during implementation, and has remarkable technical benefit.

Description

Construction method for closure section of external stiff framework of cast-in-place box girder

Technical Field

The invention belongs to the field of bridge engineering, and particularly relates to a construction method of a cast-in-place box girder external stiffened framework folding section, which is suitable for cast-in-place box girder engineering, particularly suitable for cast-in-place box girder folding section construction under complex terrain conditions such as cross-river conditions, cross-mountain areas and the like.

Background

Since the 21 st century, china develops rapidly in the high-speed traffic industry such as highways and railways, inevitably spans across mountains and valleys, rivers and other regions, and therefore a large number of large-span bridges need to be built to meet the development requirements. The prestressed concrete continuous beam bridge has the advantages of large spanning capacity, wide application range, reasonable integral stress, convenient construction, comfortable driving, good earthquake resistance and the like, and is rapidly developed in China in recent years.

From the practice of the large-span prestressed concrete continuous beam bridge constructed in China, the cantilever cast-in-place construction is mostly adopted, the finished pier top section is taken as a starting point, and the whole bridge is formed by folding the suspended hanging baskets from the vertical mold, the concrete pouring, the prestressed steel bars to the two sides in a span-to-span manner symmetrically section by section. With the continuous development of new processes and new technologies, the construction process of cantilever cast-in-place is continuously improved, the construction quality is continuously improved, and the cycle period of the operation of cantilever casting is continuously shortened; the construction efficiency and the overall quality of concrete are continuously improved; the construction machine, the basket hanging device, the cast-in-place technology and the like are greatly developed and quite horizontal, but a large optimization space exists in the construction treatment of the closure segment, for example, the concrete of the closure segment is easy to crack before prestress is applied, for example, the weight of two sides is difficult to control in the concrete pouring process of the closure segment, for example, the angle of a flange formwork of the closure segment is difficult to adjust, and the like.

In view of the above, there is a need for a construction method for a closure segment of an external stiff skeleton of a cast-in-place box beam, which has the advantages of high construction speed, high structural stability, safe and controllable construction and outstanding economic and technical benefits.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a construction method for a closure section of an external stiff framework of a cast-in-place box girder.

The construction method of the closure section of the external stiff skeleton of the cast-in-place box girder comprises the following steps:

s1, installing a bracket of the side span pier column: installing a bracket on the upper part of the side span pier stud, and installing a profile steel placing rack on the reverse side of the side span cast-in-place section of the bracket;

s2, constructing a side span cast-in-place section: erecting a side span cast-in-place section template support through a bracket, installing a balance water tank on a section steel shelving rack, binding side span cast-in-place section steel bars, pouring concrete and synchronously discharging water in the balance water tank;

s3, installing a hanging basket construction hanging bracket at the closure section: a hanging basket construction hanging bracket is arranged at the side span folding section, a balance water tank is arranged, a bottom basket is hung on a box girder top plate and a box girder bottom plate at two sides of the folding section by using hanging basket hanging rods, and a hanging basket modularized bottom die and hanging basket side dies are laid on the bottom basket; when the mid-span closure segment is constructed, the hanging basket on one side is dismantled, the hanging basket on the other side is moved forwards to the closure segment, and the suspension pouring segments of the box girders on the two sides are symmetrically provided with balance water tanks;

s4, installing a stiff framework: installing a stiff framework, tensioning a closure section top plate closure steel bundle, and installing a construction pedal on the stiff framework;

s5, installing and pouring a closure section template system: connecting a hanging basket modularization bottom die through an auxiliary hanging rod, adjusting the angle of a wing plate of the hanging basket, binding a bottom plate and a web plate reinforcing steel bar, and then installing an integrated type steel internal die; and symmetrically pouring the concrete at one time, and synchronously discharging water in the balance water tank.

Preferably, the method comprises the following steps: after the concrete strength of the cast-in-place box girder zero block and the first beam section reaches the design requirement, the rhombic hanging baskets are assembled and spliced on the cast-in-place box girder zero block and the cast-in-place box girder first beam section, the hanging baskets are pre-pressed and then cast by using the structure system of the hanging baskets, the hanging baskets move forwards after casting of the second block is completed and prestress is tensioned and grouted, and the third block is cast, and the circular casting construction is performed in sequence.

Preferably, in the step S1, the bracket is connected with the side span pier stud through a bracket hoop, the top of the bracket is additionally provided with a counter-pulling anchor cable for fixing, A bolt hole is reserved in the top surface of one side of the bracket and used for mounting the section steel shelving rack, and a through hole is reserved in the other side of the bracket and used for mounting a temporary prestress reverse-pulling anchor cable.

Preferably, in the step S2, when a side span cast-in-place section formwork support is erected, the prestress reverse-pulling anchor cable is relieved, a balance water tank is synchronously installed on the reverse side profile steel placing platform support, water injection operation on the balance water tank is completed, then cast-in-place section steel bars are bound, side span concrete is poured, water in the balance water tank is gradually discharged, and the weight reduced by water discharge of the water tank is kept consistent with the weight increased by concrete pouring; the balance water tank is arranged in the section steel shelving rack, a separate bin structure is arranged inside the balance water tank, the water capacity of each separate bin is calibrated, and each separate bin is provided with a water valve.

Preferably, in the step S4, an embedded anchor backing plate is arranged in the box girder suspension casting section, firstly, concrete with a certain thickness is embedded on the surface of the embedded anchor backing plate, the surface of the concrete is polished to be smooth, then a stiff framework is installed, the bottom end of the stiff framework is welded and fixed with the embedded anchor backing plate, and after the stiff framework is installed, a closure section top plate closure steel bundle is tensioned to the strength percentage; the stiffness framework is of a double-spliced I-shaped steel structure and symmetrically arranged on the top surfaces of the top plate and the bottom plate of the cast-in-place box girder, two ends of the stiffness framework arranged on the top plate of the cast-in-place box girder are welded with the embedded anchor backing plates arranged on the top surfaces of the cast-in-place box girder on two sides of the folding section, the top surface of the stiffness framework is also provided with a limiting plate, and a construction pedal is arranged in the limiting plate and is perpendicular to the direction of the stiffness framework.

Preferably, in step S5: installing an auxiliary suspender on a stiff skeleton arranged on a top plate of a cast-in-place box girder by welding a steel pipe cross brace, anchoring the bottom of the auxiliary suspender on a hanging basket modularized bottom die, then adjusting the angle of a wing plate of a hanging basket, binding a bottom plate and a web plate steel bar of a folding section steel reinforcement cage, and installing an integrated section steel inner die by using the stiff skeleton; the hanging basket wing plate is provided with an adjustable telescopic section, one end of the hanging basket wing plate is connected with the hanging basket side mold through a hinge shaft, the other end of the hanging basket wing plate is connected with a rail type side plate in a sliding mode, an electric control jacking device is connected below one end, connected with the rail type side plate, of the hanging basket wing plate, the end portion of the hanging basket wing plate is controlled to move up and down in the rail type side plate through the electric control jacking device, and the angle of the hanging basket wing plate is adjusted; rigid supports are arranged below the determined angle of the wing plates of the hanging basket.

Preferably, in the step S5, the integral type steel inner mold is provided with a hinge point, the integral type steel inner mold is abutted to the bottom plate steel bar and the web plate steel bar of the folding section steel bar cage through the inner mold support rod and the inner mold cross-support, the bottom end of the inner mold support rod is connected with a support base plate, and the support base plate is erected on the top surface of the stiff skeleton above the bottom plate of the folding section steel bar cage.

Preferably, in step S5, when the bottom plate and the web plate steel bars of the closure section steel bar cage are bound, the prestressed tendon pipelines are synchronously installed, the top plate steel bars and the positioning bars are continuously bound, the top plate prestressed pipelines are installed, and the positions of the steel bars, the pipelines and the anchor backing plates are checked.

The cast-in-place box girder external stiffened framework closure section construction structure is obtained by any one of the methods.

The invention has the beneficial effects that:

1) The external stiff skeleton is arranged at the closure section of the cast-in-place box girder, and the box girders at two sides of the closure section are locked before the concrete of the closure section is poured, so that the concrete of the closure section is effectively prevented from cracking before prestress is applied; and the construction pedal, the auxiliary suspender and the internal mold supporting bottom plate are arranged by the aid of the stiff skeleton, so that the construction efficiency and the construction safety are greatly improved.

2) The invention adopts the bin-divided type balance water tank, effectively controls the error between the on-site water discharge and the concrete pouring amount through the treatment of the bin-divided valves, and uniformly installs the balance water tank in the section steel shelving rack, thereby improving the structural stability of the balance water tank in the water injection and water discharge processes.

3) According to the invention, the side-span cast-in-place section template support is erected by using the bracket, and the prestress reverse-pull anchor cable is preset on the bracket side of the bracket, so that the deformation of the bracket after the template support is erected is effectively reduced, the balance water tank is synchronously arranged on the reverse side to reduce the deformation of the bracket in the side-span concrete pouring process, and the construction quality is greatly improved.

4) The invention develops an adjustable hanging basket wing plate, and realizes the height adjustment of the wing plate in a side plate track by arranging a hinge shaft and an adjustable telescopic section, thereby realizing the angle adjustment of the wing plate and ensuring the construction quality of the wing plate at a closure section.

Drawings

FIG. 1 is a schematic construction view of a closure section between suspension casting sections of a box girder according to the present invention;

FIG. 2 is a schematic layout of a closure segment cradle construction hanger of the invention;

FIG. 3 is a schematic illustration of a stiff skeleton construction according to the present invention;

FIG. 4 is a schematic view of a hanging basket template system of the present invention;

FIG. 5 is a thumbnail view of node A of FIG. 4;

FIG. 6 is a schematic view of the bracket structure of the present invention;

FIG. 7 is a schematic view of the construction of the closure between the suspension casting section of the box girder and the cast-in-place section of the support in the present invention;

fig. 8 is a schematic diagram of the internal mold structure of the closure segment of the present invention.

In the figure: 1-hanging basket construction hanging bracket; 2-hanging a basket suspender; 3-an auxiliary boom; 4-steel pipe cross bracing; 5, constructing a pedal; 6-stiff skeleton; 7-a balance water tank; an 8-water valve; 9-a section steel placing rack; 10-a box girder suspension casting section; 11-folding section steel reinforcement cage; 12-hanging basket modularization bottom die; 13-a limiting plate; 14-adjustable telescopic section; 15-rigid support; 16-hanging basket wing plate; 17-a hinge shaft; 18-a rail-mounted side plate; 19-electrically controlling jacking equipment; 20-hanging a basket side mold; 21-capping beam; 22-bracket; 23-a pier stud; 24-prestress reverse pulling the anchor cable; 25-a template holder; 26-a support; 27-boom anchorage end; 28-hinge point; 29-an inner mold strut; 30-an integrated section steel inner die; 31-a support floor; 32-inner mold waling; 33-embedding an anchor backing plate; 34-bracket hoop; 35-opposite pulling anchor cable.

Detailed Description

The present invention will be further described with reference to the following examples. The following examples are set forth merely to aid in the understanding of the invention. It should be noted that, for a person skilled in the art, several modifications can be made to the invention without departing from the principle of the invention, and these modifications and modifications also fall within the protection scope of the claims of the present invention.

Example one

As an embodiment, after the strength of concrete of a 0# block and a 1# block of a cast-in-place box girder reaches design requirements, a rhombic hanging basket is assembled on the cast-in-place box girder, 2# block pouring is carried out by utilizing a structural system after the hanging basket is pre-pressed, the hanging basket moves forward after 2# block pouring is finished and prestress is tensioned and grouted, 3# block pouring is carried out, and circulating pouring construction is carried out in sequence; the construction method of the closure section of the external stiff skeleton of the cast-in-place box girder comprises the following steps:

s1, installing a bracket of the side span pier stud: the bracket 22 is connected with the side span pier stud 23 through a bracket hoop 34, a counter-pull anchor cable 35 is additionally arranged at the top of the bracket 22 for fixing, a bolt hole is reserved in the top surface of one side of the bracket 22 and used for mounting a section steel placing rack 9, a through hole is locally reserved in the other side of the bracket 22 and used for mounting a temporary prestress counter-pull anchor cable 24, the prestress counter-pull anchor cable 24 is mounted on the side of the side span cast-in-place section of the bracket 22, and the section steel placing rack 9 is mounted on the opposite side of the side span cast-in-place section of the bracket 22;

s2, constructing a side span cast-in-place section: erecting a side span cast-in-place section template support 25 through a bracket 22, removing prestress to pull an anchor cable 24 reversely after the template support 25 is erected, synchronously installing a balance water tank 7 on a profile steel shelving rack 9 on the other side, completing water injection operation on the balance water tank 7, then binding side span cast-in-place section steel bars, pouring side span concrete, gradually discharging water in the balance water tank 7, and keeping the weight reduced by water discharged from the water tank to be consistent with the weight increased by concrete pouring;

s3, installing a hanging basket construction hanging bracket at the closure section: constructing a side span closure section in advance, installing a hanging basket construction hanging bracket 1 at the side span closure section, hanging a bottom basket on a box girder top plate and a bottom plate at two sides of the closure section by using a hanging basket hanging rod 2, and laying a hanging basket modularized bottom die 12 and hanging basket side dies 20 on the bottom basket; when the mid-span closure segment is constructed, firstly removing the hanging basket on one side, and then moving the hanging basket on the other side forwards to the mid-span closure segment; the hanging basket side section steel placing rack 9 is connected with a hanging basket foundation truss;

the folding section is provided with a balance water tank 7: the method comprises the following steps that a balance water tank 7 is arranged on one side of a side-span cantilever end of a side-span closure section, the balance water tanks 7 are symmetrically arranged on box girder suspension casting sections 10 on two sides of a middle-span closure section, the balance water tanks 7 are all arranged in a section steel placing rack 9, if the positions of the water tanks cannot be completely and symmetrically placed, the weight of the water tanks is adjusted through a water valve 8 according to the equal moment principle, and the weight is generally 1/2 of the weight of closure section cast-in-place box girder concrete;

s4, installing a stiff framework: the method comprises the steps of chiseling concrete with the thickness of 1cm and exposing embedded anchor backing plates 33 in advance, polishing the surfaces of the concrete to be smooth, installing a stiff framework 6, wherein the stiff framework 6 is of a double-spliced I-shaped steel structure and is symmetrically arranged on the top surfaces of a top plate and a bottom plate of a cast-in-place box girder, two ends of the stiff framework 6 are connected with the embedded anchor backing plates 33 on the top surfaces of the cast-in-place box girder on two sides of a closure section in a welding mode, limiting plates 13 are further arranged on the top surfaces of the stiff framework 6, and construction pedals 5 are installed in the limiting plates 13 and perpendicular to the direction of the stiff framework 6. One end of the stiff framework 6 is welded and fixed with the embedded anchor backing plate 33, the other end of the stiff framework is adjusted according to the actual length and then sealed and locked, after the stiff framework 6 is installed, the closure segment top plate closure steel bundle is stretched to 40% strength, and the construction pedal 5 is installed on the stiff framework 6;

s5, installing a closure section template system: an auxiliary suspender 3 is installed on a stiff skeleton 6 through a welded steel pipe cross brace 4, the bottom of the auxiliary suspender 3 is anchored on a hanging basket modularization bottom die 12, then the angle of a hanging basket wing plate 16 is adjusted, the hanging basket wing plate 16 is provided with an adjustable telescopic section 14, the tail end of the hanging basket wing plate 16 is connected with a hanging basket side die 20 through a hinge shaft 17, the front end of the hanging basket wing plate 16 can be adjusted in an up-and-down mode in a rail type side plate 18 through an electric control jacking device 19, and a rigid support 15 is arranged below the hanging basket wing plate 16 after the angle is determined; binding bottom plate and web plate steel bars of the folding section steel reinforcement cage 11, synchronously installing prestressed bundle pipelines, and installing an integrated section steel inner mold 30 by using a stiff skeleton 6; the integrated section steel inner die 30 is provided with a hinge point 28, and is abutted against the bottom plate steel bars and the web steel bars through an inner die support rod 29 and an inner die cross support 32, the inner die support rod 29 is arranged on a support base plate 31, and the support base plate 31 is erected on the top surface of the bottom plate stiff skeleton 6.

And (3) construction of steel bars and prestressed pipelines: and continuously binding the top plate steel bars and the positioning bars of the folding section steel bar cage 11, arranging the top plate prestressed pipeline, and checking the positions of the steel bars, the pipeline and the anchor backing plate.

Folding, locking and pouring concrete: and symmetrically pouring the closed section concrete at one time, gradually discharging water in the balance water tank 7 according to the pouring speed of the concrete, and keeping the weight reduced by discharging water in the balance water tank 7 consistent with the weight increased by pouring the concrete.

Example two

As another embodiment, the cast-in-place box girder external stiff skeleton closure segment construction structure of the cast-in-place box girder external stiff skeleton closure segment construction method in the first embodiment, as shown in fig. 1 to 8, includes a hanging basket construction hanger 1, a hanging basket hanger rod 2, a stiff skeleton 6, a section steel shelving rack 9, a hanging basket modular bottom die 12, hanging basket side dies 20, a corbel bracket 22 and an integrated section steel inner die 30;

as shown in fig. 6, the bracket 22 is connected to the side span pier 23 through a bracket anchor 34, and the top of the bracket 22 is fixed through a counter-pull anchor cable 35; when the side-span cast-in-place section formwork support 25 is not erected on the side of the side-span cast-in-place section of the bracket 22, a prestressed reverse-pull anchor cable 24 is arranged on the side of the side-span cast-in-place section of the bracket 22, and a balance water tank 7 is arranged on the reverse side of the side-span cast-in-place section of the bracket 22 through a section steel placing rack 9;

as shown in figure 1, the top plates of the box girder cantilever casting sections 10 on two sides of the closure part are also symmetrically provided with the balance water tanks 7 through the section steel shelving rack 9, and when the two sides cannot be completely symmetrical, the balance water tanks 7 on the two sides can be balanced by changing the weight.

The balance water tank 7 is arranged in the section steel shelving rack 9, a bin dividing structure is arranged inside the balance water tank 7, the water capacity of each independent bin is calibrated, and a water valve 8 is arranged in each bin dividing structure in the balance water tank 7. The section steel holding rack 9 on one side of the hanging basket can be connected with the hanging basket foundation truss. When concrete is poured, water in the balance water tank 7 is gradually discharged, and the weight reduced by discharging water in the water tank is kept consistent with the weight increased by pouring concrete.

As shown in fig. 6, the prestressed reverse-pulling anchor cables 24 are used for providing prestress for the bracket 22, and are removed synchronously when the side-span cast-in-place section formwork support 25 is installed; the bracket 22 is provided with a side span cast-in-place section template bracket 25 at the side span cast-in-place section and is also supported by a support 26.

As shown in fig. 7, a hanging basket construction hanger 1 is arranged at a box girder suspension casting section 10, the hanging basket construction hanger 1 is connected with a hanging basket modularization bottom die 12 through a hanging basket hanger rod 2, a stiff skeleton 6 is arranged on the top surfaces of a cast-in-place box girder top plate and a bottom plate, a pre-embedded anchor backing plate 33 is arranged in the box girder suspension casting section 10, two ends of the stiff skeleton 6 positioned on the top surface of the cast-in-place box girder top plate are welded with the pre-embedded anchor backing plates 33 on the top surfaces of the box girder suspension casting sections 10 on two sides of a closure section, and a tensioning prestress is applied to ensure the stability of the poured concrete; the top surface of the stiff skeleton 6 is also provided with a limiting plate 13, and a construction pedal 5 is arranged in the limiting plate 13 and is perpendicular to the stiff skeleton 6.

As shown in fig. 1 to 4 and 8, an auxiliary suspender 3 is anchored on a stiff skeleton 6 positioned on the top surface of a top plate of a cast-in-situ box girder through a steel pipe cross brace 4, and the bottom end of the auxiliary suspender 3 is connected with a hanging basket modular bottom die 12; hanging basket side dies 20 are arranged on two sides of the hanging basket modularization bottom die 12, and the integrated type steel inner die 30 is abutted to bottom plate reinforcing steel bars and web plate reinforcing steel bars of the folding section steel bar cage 11 through inner die supporting rods 29 and inner die cross supports 32.

A supporting bottom plate 31 is arranged above the stiff skeleton 6 arranged on the top surface of the cast-in-situ box girder bottom plate, and the internal mold support rod 29 is arranged above the supporting bottom plate 31.

As shown in fig. 4, the hanging basket wing plate 16 is further included, the hanging basket wing plate 16 is provided with an adjustable telescopic section 14, one end of the hanging basket wing plate 16 is connected with a hanging basket side die 20 through a hinge 17, the other end of the hanging basket wing plate 16 is connected with a rail type side plate 18 in a sliding mode, an electric control jacking device 19 is arranged below one end, connected with the rail type side plate 18, of the hanging basket wing plate 16, and a rigid support 15 is further arranged below the hanging basket wing plate 16.

Claims (9)

1. A construction method for a closure section of an external stiff framework of a cast-in-place box girder is characterized by comprising the following steps: the method comprises the following steps:

s1, installing a bracket of the side span pier column: a bracket (22) is arranged at the upper part of the side span pier stud (23), and a section steel placing rack (9) is arranged on the reverse side of the side span cast-in-place section of the bracket (22);

s2, constructing a side span cast-in-place section: erecting a side span cast-in-place section template support (25) through a bracket (22), installing a balance water tank (7) on a section steel placing rack (9), binding side span cast-in-place section steel bars, pouring concrete and synchronously discharging water in the balance water tank (7);

s3, installing a folding section hanging basket construction hanging bracket: a hanging basket construction hanging bracket (1) is installed at the side span folding section, a balance water tank (7) is arranged, a bottom basket is hung on a box girder top plate and a box girder bottom plate at two sides of the folding section by using a hanging basket hanging rod (2), and a hanging basket modularization bottom die (12) and a hanging basket side die (20) are laid on the bottom basket; when the mid-span closure section is constructed, the hanging basket on one side is dismantled, the hanging basket on the other side is moved forward to the closure section, and the box girder suspension casting sections (10) on the two sides are symmetrically provided with the balance water tanks (7);

s4, installing a stiff framework: installing a stiff framework (6), tensioning closure section top plate closure steel bundles, and installing a construction pedal (5) on the stiff framework (6);

s5, installing and pouring a closure section template system: the auxiliary hanger rod (3) is connected with the hanging basket modularization bottom die (12), the angle of a hanging basket wing plate (16) is adjusted, and an integrated type steel inner die (30) is installed after a bottom plate and a web plate reinforcing steel bar are bound; the concrete is symmetrically poured at one time, and water in the balance water tank (7) is synchronously discharged.

2. The construction method of the closure section of the external stiff skeleton of the cast-in-place box girder according to claim 1, characterized in that: after the concrete strength of the cast-in-place box girder zero block and the first beam section reaches the design requirement, the rhombic hanging baskets are assembled and spliced on the cast-in-place box girder zero block and the cast-in-place box girder first beam section, the hanging baskets are pre-pressed and then cast by using the structure system of the hanging baskets, the hanging baskets move forwards after casting of the second block is completed and prestress is tensioned and grouted, and the third block is cast, and the circular casting construction is performed in sequence.

3. The construction method of the externally-arranged stiff framework folding section of the cast-in-place box girder according to the claim 1, characterized in that in the step S (1), the bracket (22) is connected with the side span pier stud (23) through a bracket hoop (34), the top of the bracket (22) is additionally provided with a pulling anchor cable (35) for fixation, a bolt hole is reserved on the top surface of one side of the bracket (22) for installing the section steel placing rack (9), and a through hole is reserved on the other side of the bracket (22) for installing the temporary prestress reverse pulling anchor cable (24).

4. The construction method for the externally-arranged stiffened framework folding section of the cast-in-place box girder according to the claim 2 is characterized in that in the step S2, when a side span cast-in-place section template support (25) is erected, a prestress reverse pull anchor cable (24) is removed, a balance water tank (7) is synchronously installed on a reverse side profile steel placement rack (9), water injection operation for the balance water tank (7) is completed, then cast-in-place section steel bars are bound, side span concrete is poured, water in the balance water tank (7) is gradually discharged, and the weight of water discharged from the water tank is kept consistent with the weight increased by concrete pouring; the balance water tank (7) is arranged in the section steel shelving rack (9), a bin dividing structure is arranged inside the balance water tank (7), the water capacity of each independent bin is calibrated, and each independent bin is provided with a water valve (8).

5. The construction method of the externally arranged stiffened framework folding section of the cast-in-place box girder according to claim 1 is characterized in that in the step S4, an embedded anchor backing plate (33) is arranged in the box girder suspension casting section (10), firstly, concrete with a certain thickness on the surface of the embedded anchor backing plate (33) is embedded, the surface of the concrete is polished to be smooth, then, the stiffened framework (6) is installed, the bottom end of the stiffened framework (6) is fixedly welded with the embedded anchor backing plate (33), and after the stiffened framework (6) is installed, a top plate closure steel bundle of the folding section is tensioned to (40)% strength; the stiffening framework (6) is of a double-spliced I-shaped steel structure and symmetrically arranged on the top surfaces of the top plate and the bottom plate of the cast-in-place box beam, two ends of the stiffening framework (6) arranged on the top plate of the cast-in-place box beam are connected with embedded anchor backing plates (33) on the top surfaces of the cast-in-place box beams on two sides of the folding section in a welding mode, the top surface of the stiffening framework (6) is further provided with limiting plates (13), and construction pedals (5) are arranged in the limiting plates (13) in a direction perpendicular to the stiffening framework (6).

6. The construction method for the externally-arranged stiff skeleton folding section of the cast-in-place box girder according to claim 5, characterized in that in the step S5: an auxiliary suspender (3) is installed on a stiff skeleton (6) arranged on a top plate of a cast-in-place box girder by welding a steel pipe cross brace (4), the bottom of the auxiliary suspender (3) is anchored on a hanging basket modularization bottom die (12), then the angle of a hanging basket wing plate (16) is adjusted, and after a bottom plate and a web plate steel bar of a folding section steel reinforcement cage (11) are bound, an integrated section steel inner die (30) is installed by using the stiff skeleton (6); the hanging basket wing plate (16) is provided with an adjustable telescopic section (14), one end of the hanging basket wing plate (16) is connected with a hanging basket side die (20) through a hinge shaft (17), the other end of the hanging basket wing plate is connected with a rail type side plate (18) in a sliding mode, an electric control jacking device (19) is connected below one end, connected with the rail type side plate (18), of the hanging basket wing plate (16), the end portion of the hanging basket wing plate (16) is controlled to move up and down in the rail type side plate (18) through the electric control jacking device (19), and the angle of the hanging basket wing plate (16) is adjusted; rigid supports (15) are arranged below the angle of the hanging basket wing plates (16).

7. The construction method of the externally arranged stiffened skeleton folding section of the cast-in-place box girder according to claim 1, characterized in that in the step S5, the integrated section steel inner mold (30) is provided with a hinge point (28), the integrated section steel inner mold (30) is abutted to a bottom plate steel bar and a web plate steel bar of the folding section steel cage (11) through an inner mold stay bar (29) and an inner mold cross brace (32), the bottom end of the inner mold stay bar (29) is connected with a support base plate (31), and the support base plate (31) is erected on the top surface of the stiffened skeleton (6) above the bottom plate of the folding section steel cage (11).

8. The construction method for the externally arranged stiffened skeleton closure section of the cast-in-place box girder according to claim 6, wherein in the step S (5), when the bottom plate and the web plate steel bars of the closure section steel reinforcement cage (11) are bound, the prestressed tendon pipelines are synchronously installed, the top plate steel bars and the positioning bars are continuously bound, the top plate prestressed pipelines are arranged, and the positions of the steel bars, the pipelines and the anchor backing plate are checked.

9. Cast-in-place box girder external strength nature skeleton closes up a section construction structures, its characterized in that: obtainable by any of the processes described in claims 1 to 8.

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