CN111778864A

CN111778864A - Bridge with small box girders prefabricated in longitudinal sections and construction method

Info

Publication number: CN111778864A
Application number: CN202010698186.8A
Authority: CN
Inventors: 陆元春; 胡方健; 顾颖; 孔璞; 陈卫伟; 陈龙
Original assignee: Shanghai Urban Construction Design Research Institute Group Co Ltd
Current assignee: Shanghai Urban Construction Design Research Institute Group Co Ltd
Priority date: 2020-07-20
Filing date: 2020-07-20
Publication date: 2020-10-16
Anticipated expiration: 2040-07-20

Abstract

The invention discloses a bridge with small box girders prefabricated in longitudinal sections and a construction method, wherein the bridge comprises more than two girders extending along the length direction of the bridge, wherein the two sides of the bridge are provided with edge girders, and a middle girder is arranged between the edge girders at the two sides; each beam comprises a plurality of prefabricated small box beams, and the prefabricated small box beams are manufactured and formed by a section method; every two adjacent beams are connected through a small box beam transverse cast-in-place section between corresponding prefabricated small box beams; the plurality of prefabricated small box girders comprise front fulcrum section prefabricated small box girders, front span inner beam section prefabricated small box girders, span middle section prefabricated small box girders, rear span inner beam section prefabricated small box girders and rear fulcrum section prefabricated small box girders. During construction, firstly, manufacturing sections of the prefabricated small box girder; then conveying all the prefabricated small box girders to a construction site to be spliced into girders; and finally, performing transverse connection of the beams. Compared with the traditional prefabricated section beam, the number of sections is greatly reduced, and the construction is simplified.

Description

Bridge with small box girders prefabricated in longitudinal sections and construction method

Technical Field

The invention relates to the technical field of bridges, in particular to a bridge with small box girders prefabricated in longitudinal sections and a construction method.

Background

In the field of bridge engineering, the applicable span of the existing prefabricated small box girder is 25m to 35 m. For bridges with span less than 25m, if small box girders are used, the small box girders are not economical enough, and the manufacturing cost is obviously higher than that of prefabricated hollow slab girders and cast-in-place girders; for bridges with the span of more than 35m, if prefabricated small box girders are used, the problem of overlarge structural weight is faced, and large-scale transport vehicles need to be equipped, which brings great difficulty to the construction of urban bridges. The transportation process of a large number of overweight prefabricated small box girders can bring great pressure to existing urban roads along the line, which can cause damage to roadbeds, road surfaces and underground pipelines, traffic jam and the like.

In the present urban bridge works prefabricated capping beams are increasingly used. With the increasing application of the integrally prefabricated capping beam (the capping beam tonnage is about 300 tons or less), the construction method for installing the prefabricated capping beam by using a large-tonnage crane on site is mature day by day, and the tonnage of the crane is no longer a problem of restricting the site installation. Therefore, the application of prefabricated box girders with span of more than 35m is mainly limited by transportation at present.

In urban bridge engineering, great requirements are placed on the continuity of the appearance of a bridge, particularly a viaduct. For a viaduct using the prefabricated small box girders, the span of the bridge at a road crossing (crossing a transverse cross road) and a river crossing is over 35m, and a steel-concrete combined girder with the shape basically consistent with that of the prefabricated small box girders is usually used, so that the aims of unifying the shape of the bridge, improving the structure crossing capability and limiting the structure weight to meet the capability of conventional construction equipment are fulfilled.

However, the cost of the steel-concrete composite beam is obviously higher than that of the prefabricated small box beam, and if a large amount of steel structures are adopted, the steel-concrete composite beam is not economical, and if the prefabricated small box beam is applied to urban bridge engineering with the span of more than 35m, the transportation problem needs to be solved.

Therefore, how to adopt the prefabricated small box girder to realize the construction of the bridge with the span of 35m to 50m becomes a technical problem which needs to be solved urgently by the technical personnel in the field.

Disclosure of Invention

In view of the defects in the prior art, the invention provides a bridge with a small box girder prefabricated in a longitudinal subsection manner and a construction method, and aims to realize the construction of a bridge with a span of more than 35m by adopting the small box girder, and cover the crossing road and the river of most urban viaducts.

In order to achieve the purpose, the invention discloses a bridge with small box girders prefabricated in longitudinal sections, which comprises more than two girders extending along the length direction of the bridge, wherein the two sides of the bridge are provided with edge girders, and a middle girder is arranged between the edge girders.

Each beam comprises a plurality of prefabricated small box beams, and the prefabricated small box beams are manufactured and formed by a section method;

every two adjacent beams are connected through a small box beam transverse cast-in-place section between the corresponding prefabricated small box beams;

the plurality of prefabricated small box girders comprise front fulcrum section prefabricated small box girders, front span inner cross beam section prefabricated small box girders, span middle section prefabricated small box girders, rear span inner cross beam section prefabricated small box girders and rear fulcrum section prefabricated small box girders;

each front fulcrum section prefabricated small box girder comprises a small box girder box body inner prefabricated part, a small box girder box body outer top plate prefabricated part and a front fulcrum cross beam prefabricated part;

each front span inner cross beam segment prefabricated small box girder comprises a small box girder box body inner prefabricated part, a small box girder box body outer top plate prefabricated part and a front span inner cross beam prefabricated part;

each midspan section prefabricated small box girder comprises a small box girder box body inner part and a small box girder box body outer top plate prefabricated part;

each rear span inner cross beam segment prefabricated small box girder comprises a small box girder box body inner prefabricated part, a small box girder box body outer top plate prefabricated part and a rear span inner cross beam prefabricated part;

each rear fulcrum section prefabricated small box girder comprises a small box girder box body inner prefabricated part, a small box girder box body outer top plate prefabricated part and a rear fulcrum beam prefabricated part;

the length of each beam is adjusted by changing the lengths of the front fulcrum section prefabricated small box beam, the rear fulcrum section prefabricated small box beam and the midspan section prefabricated small box beam;

prestressed steel bundles arranged along the bridge direction are arranged between every two adjacent small prefabricated box girders which respectively belong to two adjacent girders and are tightly connected together after the prestressed steel bundles are tensioned;

every two adjacent small prefabricated box girders belonging to the same girder are connected in a mode of arranging shear keys along the splicing seams in the bridge direction; coating epoxy resin glue on each sequential bridge-direction splicing seam;

each small prefabricated box girder comprises a top plate, a web plate and a bottom plate; the combination part of the top plate and the web plate and the combination part of the bottom plate and the web plate are respectively provided with a bearing;

the web plate of each front fulcrum section prefabricated small box girder and the web plate of each rear fulcrum section prefabricated small box girder are of variable thickness structures;

the variable thickness structure means that one side of the web close to the inner cross beam is a thinner side, and one side of the web close to the front fulcrum cross beam or the rear fulcrum cross beam is a thicker side; the thickened area of the variable-thickness structure is as follows: starting from the inner side wall of the corresponding front supporting point beam or rear supporting point beam to the inner cross beam spanning direction by about 4m to 9 m;

the top plate of each small box girder is provided with a plurality of annular reinforcing steel bars arranged along the transverse bridge direction;

on a horizontal projection plane, the projection of each annular steel bar is a straight line segment, and an included angle of 86-88 degrees is formed between the projection of each annular steel bar and the axis of the corresponding small box girder box body; when the installation of two adjacent prefabricated small box girders is finished, the exposed annular reinforcing steel bars are kept to be staggered with each other;

on a vertical plane vertical to the axis of the bridge, the annular reinforcing steel bars exposed by every two adjacent small prefabricated box girders are mutually staggered to form a closed area; a plurality of through long steel bars in the ring are arranged in the closed area along the bridge direction; a plurality of steel bars which are arranged along the bridge direction and are through long outside the closed area are arranged outside the closed area;

and the plurality of through long steel bars in the ring and the plurality of through long steel bars outside the ring are respectively arranged at two round ends, top edges or bottom edges of the closed graph.

Preferably, each of the edge beams comprises one front supporting point section prefabricated small box girder, and the front supporting point cross beam prefabricated part of the front supporting point section prefabricated small box girder is arranged at the front supporting point section of the corresponding edge beam; each middle beam comprises two front supporting point section prefabricated small box beams, and the front supporting point cross beam prefabricated parts of the two front supporting point section prefabricated small box beams are arranged at the front supporting point sections of the middle beam;

each boundary beam comprises a front span inner cross beam section prefabricated small box girder, and the front span inner cross beam prefabricated part of the front span inner cross beam section prefabricated small box girder is arranged at the front span inner cross beam section of the corresponding boundary beam; each middle beam comprises two front span inner cross beam sections for prefabricating small box beams, and the front span inner cross beam prefabricating parts of the two front span inner cross beam sections for prefabricating the small box beams are arranged at the front span inner cross beam sections of the middle beam;

the midspan section of each boundary beam and each middle beam comprises a plurality of prefabricated small box girders of the midspan section;

each boundary beam comprises a rear span inner cross beam section prefabricated small box girder, and the rear span inner cross beam prefabricated part of the rear span inner cross beam section prefabricated small box girder is arranged at the rear span inner cross beam section of the corresponding boundary beam; each middle beam comprises two rear span inner cross beam sections for prefabricating the small box girders, and the rear span inner cross beam prefabricating parts of the two rear span inner cross beam sections for prefabricating the small box girders are arranged at the rear span inner cross beam sections of the middle beam;

each boundary beam comprises a rear supporting point section prefabricated small box girder, and a rear supporting point cross beam prefabricated part of the rear supporting point section prefabricated small box girder is arranged at a rear span inner cross beam section of the corresponding boundary beam; each middle beam comprises two rear supporting point section prefabricated small box beams, and the rear supporting point cross beam prefabricated parts of the two rear supporting point section prefabricated small box beams are arranged at the rear span inner cross beam sections of the middle beam.

Preferably, each front support point section prefabricated small box girder, each front span inner crossbeam section prefabricated small box girder, each mid-span section prefabricated small box girder, each rear span inner crossbeam section prefabricated small box girder and each rear support point section prefabricated small box girder are provided with an in-vivo prestress system comprising a steel strand, a corrugated pipe and an anchorage.

Preferably, each small box girder transverse cast-in-place section is made of concrete materials, and the strength grade of each small box girder transverse cast-in-place section is higher than that of the corresponding prefabricated small box girder by more than 2 grades; or steel ingots with the same strength grade as the corresponding prefabricated small box girders are adopted to mill the steel fiber reinforced concrete, and the doping amount of the steel fiber is not less than 60kg/m 3;

the thickness of the transverse cast-in-place section of each small box girder corresponding to each front fulcrum section prefabricated small box girder, each front span inner cross beam section prefabricated small box girder, each middle span section prefabricated small box girder, each rear span inner cross beam section prefabricated small box girder and each rear fulcrum section prefabricated small box girder is respectively the same as the thickness of the corresponding parts of the front fulcrum section prefabricated small box girder, the front span inner cross beam section prefabricated small box girder, the middle span section prefabricated small box girder, the rear span inner cross beam section prefabricated small box girder and the rear fulcrum section prefabricated small box girder.

Preferably, the lengths of each front pivot point section prefabricated small box girder, each midspan section prefabricated small box girder and each rear pivot point section prefabricated small box girder are 8m to 20 m;

the length of each rear span inner cross beam section prefabricated small box girder and the length of each front span inner cross beam section prefabricated small box girder are both 0.3m to 0.5 m.

Preferably, the cross section of each prefabricated small box girder is in a multi-connected graph and comprises 2 multi-line sections which are continuous from head to tail; the total width of the section of each small prefabricated box girder is 2.7-4.0 m.

Preferably, each top plate is 0.19m to 0.25m thick, each web is 0.19m to 0.35m thick, and each bottom plate is 0.19m to 0.35m thick;

the thickness of the prefabricated part of the top plate outside each small box girder body is about 0.22m to 0.25 m; the thickness of the corresponding front supporting point beam prefabricated part, the rear supporting point beam prefabricated part, the front span inner beam prefabricated part or the rear span inner beam prefabricated part is 0.2m to 0.3 m.

Preferably, the axis of each small box girder is a straight line or a curve, and structures inside and outside each small box girder are matched with the axis in a lofting manner;

the transverse bridge length of the prefabricated part of the outer top plate of each small box girder is matched with the width of the bridge.

Preferably, the annular steel bar is continuously bent and formed by a whole steel bar; the interval between every two adjacent annular steel bars is 0.1-0.15 m;

and two ends of each annular reinforcing steel bar are exposed out of the prefabricated part of the outer top plate of the box body of the small box girder by 0.5-1.0 m.

The invention also provides a construction method of the bridge with the small box girder prefabricated in the longitudinal subsection, which comprises the following steps:

step 1, manufacturing a section of a prefabricated small box girder;

step 1.1, manufacturing a front span inner cross beam section prefabricated small box girder and a rear span inner cross beam section prefabricated small box girder;

the small box girders prefabricated on the front span inner cross beam sections and the small box girders prefabricated on the rear span inner cross beam sections adopt a unified steel formwork sleeving system, one of the small box girders is manufactured firstly, and the other small box girder is manufactured after demolding and maintenance;

2 splicing seams respectively exist in the small box girders prefabricated in the front span inner cross beam sections and the small box girders prefabricated in the rear span inner cross beam sections; each splicing seam is provided with a plurality of shear keys;

the plurality of shear keys are formed by using end templates which are completely matched with the shear keys in shape in the manufacturing stage;

step 1.2, manufacturing a span middle section prefabricated small box girder;

the outer template and the inner template of the template are both steel template systems, and the end templates of the template are cross-inner side splicing seams of a front cross inner beam section and cross-inner side splicing seams of a rear cross inner beam section;

before concrete is poured, a release agent is coated on the contact surface of the steel template system and the concrete, the surface of the cross-inner side splicing seam of the front-span inner beam section prefabricated small box girder and the surface of the cross-inner side splicing seam of the rear-span inner beam section prefabricated small box girder;

step 1.3, manufacturing a front supporting point section prefabricated small box girder and a rear supporting point section prefabricated small box girder;

for the small box girder prefabricated by the front supporting point segments, an outer template, an inner template and an outer side spanning end template of the used template are all steel template systems, and the inner side spanning end template is an outer side spanning splicing seam of the small box girder prefabricated by the front inner cross beam segments;

for the rear supporting point section, an outer template, an inner template and an outer side spanning end template of the used templates are all steel template systems, and the inner side spanning end template is an outer side spanning splicing seam of a prefabricated small box girder of the rear spanning inner beam section;

before concrete is poured, a release agent is coated on the contact surface of the steel template system and the concrete, the surface of the outside-crossing splicing seam of the front-crossing inner crossbeam segment prefabricated small box girder and the surface of the outside-crossing splicing seam of the rear-crossing inner crossbeam segment prefabricated small box girder;

step 2, splicing all the prefabricated small box girders into girders;

step 2.1, according to the following steps: sequentially hoisting and placing a front fulcrum section prefabricated small box girder, a front span inner beam section prefabricated small box girder, a span middle section prefabricated small box girder, a rear span inner beam section prefabricated small box girder and a rear fulcrum section prefabricated small box girder on a pedestal, and reserving a distance of 1m between splicing seams between two adjacent prefabricated small box girders;

2.2, coating epoxy resin glue on the splicing seams between the prefabricated small box girders, wherein the thickness of the epoxy resin glue coated on each splicing seam is 1-3 mm;

2.3, hoisting the midspan section prefabricated small box girder, putting 2 special cushion blocks below the midspan section prefabricated small box girder, then putting the midspan section prefabricated small box girder down and supporting the midspan section prefabricated small box girder on the special cushion blocks, and keeping the top edge of the midspan section prefabricated small box girder in the middle in a horizontal state;

each special cushion block is respectively positioned at two ends of the middle-span section prefabricated small box girder, and the distance between the outer side of each special cushion block and the splicing seam of the middle-span section is 0.5 m;

step 2.4, each special cushion block can realize the functions of micro-adjusting the elevation of the supported structure in the vertical direction to be 1mm to 20mm, micro-adjusting the turning gradient of the supported structure in the transverse bridge direction to be 1/2500 to 20/2500 and micro-adjusting the supported structure in the bridge direction to be 1mm to 20 mm;

2.5, respectively hoisting the prefabricated small box girder of the front span inner beam section and the prefabricated small box girder of the rear span inner beam section and moving the prefabricated small box girders to the vicinity of the prefabricated small box girder of the midspan section, keeping the distance between the splicing seams of the prefabricated small box girders of the front span inner beam section and the prefabricated small box girders of the rear span inner beam section and the splicing seams of the prefabricated small box girders of the midspan section at 20mm, and enabling the top edge of the splicing seams of the prefabricated small box girders of the front span inner beam section and the prefabricated small box girders of the rear span inner beam section to be higher than the top edge of the splicing seams of the midspan section by more than 20 mm;

respectively placing 1 special cushion block under the small box girder prefabricated by the front span inner cross beam section and the small box girder prefabricated by the rear span inner cross beam section, adjusting the bearing surfaces of the special cushion blocks to be flush with the bottom edges of the splicing seams of the span middle sections, then placing the small box girder prefabricated by the front span inner cross beam section and the small box girder prefabricated by the rear span inner cross beam section, and supporting the small box girders on the special cushion blocks;

micro-adjusting the special cushion blocks, and aligning the cross sections of the splicing seams of the small box girders prefabricated in the front-span inner beam section and the rear-span inner beam section with the cross sections of the splicing seams of the small box girders prefabricated in the midspan section in the forward bridge direction and the transverse bridge direction;

step 2.6, mounting temporary prestress tensioning devices on a top plate and a bottom plate in a box body of the front span inner cross beam section prefabricated small box girder, the rear span inner cross beam section prefabricated small box girder and the midspan section prefabricated small box girder, tensioning temporary prestress, enabling splicing seams of the front span inner cross beam section prefabricated small box girder, the rear span inner cross beam section prefabricated small box girder and the midspan section prefabricated small box girder to be tightly combined, and extruding epoxy resin glue coated on the splicing seams;

the tight combination means that the average pre-stress of the splicing seams is not less than 0.5 MPa;

step 2.7, hoisting the front-supporting point section prefabricated small box girder and the rear-supporting point section prefabricated small box girder respectively and moving the front-supporting point section prefabricated small box girder and the rear-supporting point section prefabricated small box girder to the positions close to the front-supporting inner beam section prefabricated small box girder and the rear-supporting inner beam section prefabricated small box girder, enabling the splicing seams of the front-supporting point section prefabricated small box girder and the rear-supporting point section prefabricated small box girder to be respectively kept at a distance of 20mm from the splicing seams of the front-supporting inner beam section prefabricated small box girder and the rear-supporting inner beam section prefabricated small box girder, and enabling the top edges of the splicing seams of the front-supporting point section prefabricated small box girder and the rear-supporting point section prefabricated small box girder to be higher than the top edges of the splicing seams;

respectively placing 2 special cushion blocks under the small box girder prefabricated by the front fulcrum section and the small box girder prefabricated by the rear fulcrum section, adjusting the bearing surfaces of the special cushion blocks to be flush with the bottom edges of splicing seams of the small box girder prefabricated by the front span inner cross beam section and the small box girder prefabricated by the rear span inner cross beam section, and then placing the small box girder prefabricated by the front fulcrum section and the small box girder prefabricated by the rear fulcrum section and supporting the small box girder on the special cushion blocks;

micro-adjusting a special cushion block, wherein the cross sections of splicing seams of the front supporting point section prefabricated small box girder and the rear supporting point section prefabricated small box girder are aligned with the cross sections of splicing seams of the midspan section prefabricated small box girder in the forward bridge direction and the transverse bridge direction;

the 4 special cushion blocks are respectively positioned at two ends of the front supporting point section prefabricated small box girder and the rear supporting point section prefabricated small box girder, and the joint seam and the girder end of the outer side of each special cushion block, which is 0.5m away from the front supporting point section prefabricated small box girder and the rear supporting point section prefabricated small box girder, are respectively positioned at two ends of the front supporting point section prefabricated small box girder and the rear supporting point section prefabricated small box girder;

step 2.8, mounting temporary prestress tensioning devices on a top plate and a bottom plate in a box body of the front fulcrum section prefabricated small box girder, the rear fulcrum section prefabricated small box girder and the midspan section prefabricated small box girder, tensioning temporary prestress, enabling splicing seams of the front fulcrum section prefabricated small box girder and the front midspan inner cross beam section prefabricated small box girder and splicing seams of the rear fulcrum section prefabricated small box girder and the rear midspan inner cross beam section prefabricated small box girder to be respectively and tightly combined, and extruding epoxy resin glue coated on the splicing seams;

step 2.9, mounting prestressed reinforcements, mounting prestressed reinforcement anchors, tensioning the prestressed reinforcements, mounting clamping pieces of the prestressed reinforcement anchors, pouring cement slurry into the prestressed pipeline until the prestressed pipeline is compact, sealing the anchors, and removing the temporary prestressed tensioning device; thus, a complete beam is obtained;

step 2.10, repeating the steps 2.1 to 2.9 to complete the assembly of all the beams;

step 3, transverse connection of beams;

3.1, transporting all the beams to a construction site, and installing the beams to the designated positions by adopting a crane;

step 3.2, installing a template of the small box girder transverse cast-in-place section on site;

step 3.3, installing the reinforcing steel bars of the front-supporting-point beam cast-in-place section, the reinforcing steel bars of the front-span inner beam cast-in-place section, the reinforcing steel bars of the rear-supporting-point beam cast-in-place section and the through-length reinforcing steel bars of the small box girder box body outer top plate cast-in-place section on site;

the length of the through long steel bar is basically consistent with the total length of one prefabricated small box girder, and the through long steel bar penetrates into a closed area surrounded by annular steel bars of adjacent prefabricated small box girders from a front pivot until the through long steel bar reaches a rear pivot;

the through long steel bar can be a whole steel bar, can also be a steel bar which is lengthened by welding, and can also be a steel bar which is lengthened by binding and lapping;

and 3.4, casting the concrete of the front supporting point beam cast-in-place section, the concrete of the front span inner beam cast-in-place section, the concrete of the rear supporting point beam cast-in-place section and the concrete of the small box girder box outer top plate cast-in-place section in situ.

The invention has the beneficial effects that:

compared with the traditional prefabricated section beam, the number of sections is greatly reduced, and construction is simplified; the invention adopts the form of in vivo prestress, can ensure the durability of the structure by controlling the grouting quality and reduce the maintenance cost of the structure.

The annular reinforcing steel bars of the prefabricated small box girder are arranged in a mode of being not perpendicular to the axis of the small box girder, so that the annular reinforcing steel bars of the adjacent prefabricated small box girders are sufficiently staggered on a plane, and the condition that the annular reinforcing steel bars collide with each other in the installation process of the adjacent prefabricated small box girders can be avoided.

When the sections are manufactured, the form of 'large sections + short sections' is adopted, the short sections are fully utilized as end templates, the stacking length of the sections during matching is shortened, the manufacturing land is saved, the installation weight of a temporary structure during construction is reduced, and the construction is more flexible and convenient.

The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

Fig. 1 shows a schematic cross-sectional structure of an embodiment of a two-beam of the present invention.

Fig. 2 shows a schematic cross-sectional structure of a three beam embodiment of the present invention.

Fig. 3 shows a schematic cross-sectional view of a fulcrum beam in an embodiment of a two-beam system of the invention.

Fig. 4 shows a schematic cross-sectional structure at the fulcrum beam in a three beam embodiment of the invention.

Fig. 5 is a schematic elevation view of an embodiment of the present invention.

Fig. 6 is a schematic cross-sectional view illustrating a prefabricated box girder according to an embodiment of the present invention.

Fig. 7 is a schematic cross-sectional view illustrating a second prefabricated box girder according to an embodiment of the present invention.

Fig. 8 is a schematic sectional view showing a third prefabricated box girder according to an embodiment of the present invention.

Fig. 9 is a schematic sectional view showing a portion of the ring-shaped reinforcing bars according to an embodiment of the present invention.

Fig. 10 is a schematic plan view showing a structure of a ring-shaped reinforcing bar portion according to an embodiment of the present invention.

Fig. 11 is a schematic cross-sectional view illustrating a portion of a full length reinforcement bar according to an embodiment of the present invention.

Fig. 12 shows a schematic elevational view of a prefabricated box girder spanning an inner beam segment according to an embodiment of the present invention.

FIG. 13 is a schematic cross-sectional view at AA of FIG. 12 illustrating the present invention.

Fig. 14 shows a schematic view of a prefabricated box girder of the prefabricated front pivot segment according to an embodiment of the invention.

Fig. 15 is a schematic diagram illustrating a splicing process of the front span inner beam section prefabricated small box girder, the rear span inner beam section prefabricated small box girder and the midspan section prefabricated small box girder in one embodiment of the invention.

Fig. 16 is a schematic diagram illustrating a splicing process of the front-supporting-point-section prefabricated small box girder and the rear-supporting-point-section prefabricated small box girder in one embodiment of the invention.

Fig. 17 shows a schematic diagram of the spliced front-supporting-point-section prefabricated small box girder and rear-supporting-point-section prefabricated small box girder in one embodiment of the invention.

Detailed Description

Examples

As shown in fig. 1 to 13, the bridge with the longitudinally-segmented prefabricated small box girders comprises more than two girders extending along the length direction of the bridge, wherein the two sides of the bridge are provided with edge girders, and the middle girder is arranged between the edge girders.

every two adjacent beams are connected through a small box beam transverse cast-in-place section between corresponding prefabricated small box beams;

the length of each beam is adjusted by changing the lengths of the front supporting point section prefabricated small box beam, the rear supporting point section prefabricated small box beam and the midspan section prefabricated small box beam;

the web plates of each front fulcrum section prefabricated small box girder and each rear fulcrum section prefabricated small box girder are of variable thickness structures;

the variable thickness structure means that one side of the web close to the inner cross beam is a thinner side, and one side of the web close to the front fulcrum cross beam or the rear fulcrum cross beam is a thicker side; the thickened area of the variable thickness structure is as follows: starting from the inner side wall of the corresponding front supporting point beam or rear supporting point beam to the inner cross beam spanning direction by about 4m to 9 m;

on the horizontal projection plane, the projection of each annular steel bar is a straight line segment, and an included angle of 86-88 degrees is formed between the projection of each annular steel bar and the axis of the corresponding box girder box body; when the installation of two adjacent small prefabricated box girders is finished, the exposed annular reinforcing steel bars are kept staggered;

on a vertical plane vertical to the axis of the bridge, annular reinforcing steel bars exposed by every two adjacent prefabricated small box girders are mutually staggered to form a closed area; a plurality of through long steel bars in the ring are arranged in the closed area along the bridge direction; a plurality of steel bars which are arranged along the bridge direction and are through long outside the closed area are arranged outside the closed area;

the plurality of circles of inner through long steel bars and the plurality of circles of outer through long steel bars are respectively arranged at two round ends, top edges or bottom edges of the closed graph.

The principle of the invention lies in that long sections are longitudinally adopted, the long sections comprise front-span section prefabricated small box girders, midspan section prefabricated small box girders and rear-span section prefabricated small box girders, and additional short sections comprise each girder in the form of front-span inner cross beam section prefabricated small box girders and rear-span inner cross beam section prefabricated small box girders, so that the number of the sections is greatly reduced and the construction is simplified compared with the traditional prefabricated section girders.

In some embodiments, each of the edge beams includes a front pivot section prefabricated box girder, and a front pivot cross girder prefabricated part of the front pivot section prefabricated box girder is arranged at the front pivot section of the corresponding edge beam; each middle beam comprises two front fulcrum section prefabricated small box beams, and front fulcrum beam prefabricated parts of the two front fulcrum section prefabricated small box beams are arranged at the front fulcrum section of the middle beam;

each boundary beam comprises a front span inner cross beam section prefabricated small box girder, and a front span inner cross beam prefabricated part of each front span inner cross beam section prefabricated small box girder is arranged at the front span inner cross beam section of the corresponding boundary beam; each middle beam comprises two front span inner cross beam sections for prefabricating the small box girders, and the front span inner cross beam prefabricating parts of the two front span inner cross beam sections for prefabricating the small box girders are arranged at the front span inner cross beam sections of the middle beam;

each edge beam and the midspan section of each middle beam respectively comprise a plurality of midspan section prefabricated small box beams;

each boundary beam comprises a rear span inner cross beam section prefabricated small box girder, and a rear span inner cross beam prefabricated part of the rear span inner cross beam section prefabricated small box girder is arranged at the rear span inner cross beam section of the corresponding boundary beam; each middle beam comprises two rear span inner cross beam sections for prefabricating the small box beam, and rear span inner cross beam prefabricating parts of the two rear span inner cross beam sections for prefabricating the small box beam are arranged at the rear span inner cross beam sections of the middle beam;

each boundary beam comprises a rear fulcrum section prefabricated small box girder, and a rear fulcrum beam prefabricated part of the rear fulcrum section prefabricated small box girder is arranged at a rear span inner beam section of the corresponding boundary beam; each middle beam comprises two rear fulcrum section prefabricated small box beams, and rear fulcrum beam prefabricated parts of the two rear fulcrum section prefabricated small box beams are arranged at the rear span inner beam section of the middle beam.

In some embodiments, each front pivot section prefabricated box girder, each front span inner beam section prefabricated box girder, each span middle section prefabricated box girder, each rear span inner beam section prefabricated box girder and each rear pivot section prefabricated box girder are provided with an in-vivo prestress system comprising steel strands, corrugated pipes and anchors.

In some embodiments, each small box girder transverse cast-in-place section is made of concrete, and the strength grade of each small box girder transverse cast-in-place section is higher than that of a corresponding prefabricated small box girder by more than 2 grades; or steel ingots with the same strength grade as the corresponding prefabricated small box girders are adopted to mill the steel fiber reinforced concrete, and the doping amount of the steel fiber is not less than 60kg/m 3;

the thickness of the transverse cast-in-place section of each front supporting point section prefabricated small box girder, each front span inner cross beam section prefabricated small box girder, each middle span section prefabricated small box girder, each rear span inner cross beam section prefabricated small box girder and each rear supporting point section prefabricated small box girder is respectively the same as the thickness of the corresponding front supporting point section prefabricated small box girder, the front span inner cross beam section prefabricated small box girder, the middle span section prefabricated small box girder, the rear span inner cross beam section prefabricated small box girder and the corresponding rear supporting point section prefabricated small box girder.

In some embodiments, the length of each front pivot segment precast box girder, each mid-span segment precast box girder and each rear pivot segment precast box girder is 8m to 20 m;

the lengths of the prefabricated small box girders of each rear span inner cross beam segment and the prefabricated small box girders of each front span inner cross beam segment are both 0.3m to 0.5 m.

In some embodiments, each prefabricated small box girder section is in a multi-connected graph and comprises 2 multi-line segments which are continuous from head to tail; the total width of the section of each prefabricated small box girder is 2.7m to 4.0 m.

In some embodiments, each top plate is 0.19m to 0.25m thick, each web is 0.19m to 0.35m thick, and each bottom plate is 0.19m to 0.35m thick;

In some embodiments, the axis of each box girder is a straight line or a curved line, and the structures inside and outside each box girder are matched with the axis lofting;

In some embodiments, the annular reinforcing steel bar is formed by continuously bending the whole reinforcing steel bar; the interval between every two adjacent annular steel bars is 0.1-0.15 m;

two ends of each annular reinforcing steel bar are exposed out of the prefabricated part of the outer top plate of the box body of the small box girder by 0.5-1.0 m.

As shown in fig. 14 to 17, the present invention further provides a construction method of a bridge with longitudinally segmented precast box girders, which comprises the following steps:

step 1, manufacturing a section of a prefabricated small box girder;

the method comprises the following steps that a unified steel formwork system is adopted for prefabricating small box girders on front-span inner beam sections and rear-span inner beam sections, one of the small box girders is manufactured firstly, and the other small box girder is manufactured after demolding and maintenance;

2 splicing seams respectively exist in the small box girder prefabricated in the front span inner cross beam section and the small box girder prefabricated in the rear span inner cross beam section; each splicing seam is provided with a plurality of shear keys;

the plurality of shear keys are formed by using end templates which are completely matched with the shapes of the shear keys in the manufacturing stage;

step 1.2, manufacturing a span middle section prefabricated small box girder;

step 2, splicing all the prefabricated small box girders into girders;

step 2.3, hoisting the midspan section prefabricated small box girder, placing 2 special cushion blocks below the midspan section prefabricated small box girder, then lowering the midspan section prefabricated small box girder and supporting the midspan section prefabricated small box girder on the special cushion blocks, and keeping the top edge of the midspan section prefabricated small box girder in the middle in a horizontal state;

each special cushion block is respectively positioned at two ends of the small box girder prefabricated at the midspan section, and the distance between the outer side of each special cushion block and the splicing seam of the midspan section is 0.5 m;

tightly combined, namely that the average pre-stress of the splicing seams is not less than 0.5 MPa;

step 3, transverse connection of beams;

the full-length steel bar is that the length of the full-length steel bar is basically consistent with the total length of one prefabricated small box girder, and the full-length steel bar penetrates into a closed area surrounded by the annular steel bars of the adjacent prefabricated small box girders from a front fulcrum until the full-length steel bar reaches a rear fulcrum;

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. The bridge comprises more than two beams extending along the length direction of the bridge, wherein the two sides of the bridge are provided with edge beams, and a middle beam is arranged between the edge beams on the two sides; the box girder structure is characterized in that each girder comprises a plurality of prefabricated small box girders, and the prefabricated small box girders are manufactured and formed by a section method;

2. The bridge of longitudinally segmented prefabricated box girders according to claim 1, wherein each of the edge girders comprises one of the front pivot section prefabricated box girders, the front pivot cross girder prefabricated part of the front pivot section prefabricated box girder being provided at the front pivot section of the corresponding edge girder; each middle beam comprises two front supporting point section prefabricated small box beams, and the front supporting point cross beam prefabricated parts of the two front supporting point section prefabricated small box beams are arranged at the front supporting point sections of the middle beam;

3. The bridge of longitudinally segmented prefabricated box girders according to claim 1, wherein each of the front supporting point segment prefabricated box girders, each of the front span inner beam segment prefabricated box girders, each of the span middle segment prefabricated box girders, each of the rear span inner beam segment prefabricated box girders and each of the rear supporting point segment prefabricated box girders are provided with an in-vivo prestress system comprising steel strands, corrugated pipes and anchors.

4. The bridge with the longitudinally segmented and prefabricated small box girders according to claim 1, wherein each small box girder transverse cast-in-place section is made of concrete materials, and the strength grade of each small box girder transverse cast-in-place section is higher than that of the corresponding prefabricated small box girder by more than 2 grades; or steel ingots with the same strength grade as the corresponding prefabricated small box girders are adopted to mill the steel fiber reinforced concrete, and the doping amount of the steel fiber is not less than 60kg/m 3;

5. The bridge of longitudinally segmented precast box girders according to claim 1, wherein the length of each front supporting point segment precast box girder, each midspan segment precast box girder and each rear supporting point segment precast box girder is 8-20 m;

6. The bridge with the longitudinally segmented precast box girders according to claim 1, wherein each precast box girder has a cross-sectional shape of a multiply-connected graph comprising 2 end-to-end continuous multi-line segments; the total width of the section of each small prefabricated box girder is 2.7-4.0 m.

7. The bridge of longitudinally segmented precast box girders according to claim 1, wherein each of the top plates has a thickness of 0.19m to 0.25m, each of the web plates has a thickness of 0.19m to 0.35m, and each of the bottom plates has a thickness of 0.19m to 0.35 m;

8. The bridge of longitudinally segmented precast box girders according to claim 1, wherein the axis of each box girder is a straight line or a curved line, and structures inside and outside each box girder are lofted to match the axis;

9. The bridge with the longitudinally segmented and prefabricated small box girders as claimed in claim 1, wherein the annular reinforcing steel bars are continuously bent and formed by using a whole reinforcing steel bar; the interval between every two adjacent annular steel bars is 0.1-0.15 m;

10. The construction method of the bridge with the longitudinally segmented precast box girders according to claim 1, comprising the following steps of:

step 1, manufacturing a section of a prefabricated small box girder;

step 1.2, manufacturing a span middle section prefabricated small box girder;

step 2, splicing all the prefabricated small box girders into girders;

step 3, transverse connection of beams;