CN113789711A - NC-UHPC combined assembly type prestressed concrete box girder, construction method and bridge thereof - Google Patents

Abstract

The invention discloses an NC-UHPC combined assembled prestressed concrete box girder which comprises a prefabricated NC top plate (11), a prefabricated NC bottom plate (21) and a prefabricated UHPC variable cross-section straight web plate (31), wherein the prefabricated UHPC variable cross-section straight web plate (31) is arranged in such a way that the plate surface areas of the two vertical ends of the web plate are larger than the plate surface area of the middle part of the web plate; by combining NC-UHPC, the advantages of high NC compressive strength and low price are fully utilized, the outstanding advantages of UHPC such as high strength, high elastic modulus, high durability, high toughness, high compactness, low creep and the like are fully exerted, and the steel plate has the advantages of excellent structural stress performance, light weight, high cost performance, light construction hoisting weight, reduced support construction, short construction period and the like.

Description

NC-UHPC combined assembly type prestressed concrete box girder, construction method and bridge thereof

Technical Field

The invention relates to the field of bridges, in particular to an NC-UHPC combined assembly type prestressed concrete box girder, a construction method and a bridge thereof.

Background

Currently, prefabricated bridge girders and composite structure bridge girders are being vigorously popularized in China. Compared with cast-in-place concrete box girders, the prefabricated assembled box girder and the combined structure box girder have the advantages of remarkably improving construction quality and green construction benefits, effectively reducing construction risks and adverse effects of construction on traffic and environment, improving production efficiency and the like. The traditional prefabricated section prestressed concrete box girder has high construction precision requirement, relatively long construction period and high requirements on beam storage and beam transportation, and has high requirements on site construction equipment no matter the whole-hole section assembly of a bridge girder erection machine or the section assembly of a cantilever method is adopted. The traditional concrete box girder has the defects of easy cracking of a web plate, large self weight and the like due to low tensile strength and shear strength of common concrete. Aiming at the problem, the defects of the traditional concrete box girder can be overcome by using the corrugated steel web concrete box girder and the steel truss web concrete composite girder, but the problems of large workload of later maintenance, concentrated stress of steel-concrete connection nodes, complex stress and the like also exist. Ultra-High Performance Concrete (UHPC for short) is a High-density cement-based composite engineering material prepared according to the maximum bulk density principle (porosity and macroporosity are reduced) and a low water-cement ratio, and has the outstanding advantages of High strength, High elastic modulus, High durability, High toughness, High compactness, low creep and the like. A plurality of engineering practices show that: the UHPC can remarkably reduce the size of a component, lighten the self weight of a structure and increase the spanning capacity under the condition of ensuring equivalent strength and durability.

In bridge engineering, although UHPC has been widely used in many aspects such as composite bridge deck pavement structure and old bridge reinforcement, from the current use situation, one of the main factors restricting the development of UHPC bridge structure is its high cost and high self-contraction characteristic. In the technical field of bridge structural engineering, if the main structural material is all made of UHPC, the method is not economical, and because the bridge structure needs to meet a plurality of performance targets such as strength, rigidity, stability and the like, the ultrahigh mechanical property of the bridge structure cannot be fully utilized, so that the advantages of the UHPC material are wasted in an idle mode.

Disclosure of Invention

In view of the above, the NC-UHPC combined assembly type prestressed concrete box girder and the construction method thereof of the present invention make full use of the advantages of high NC compressive strength and low price by combining NC-UHPC, fully exert the outstanding advantages of high UHPC strength, high elastic modulus, high durability, high toughness, high compactness, low creep, etc., and have the advantages of excellent structural stress performance, light weight, high cost performance, light construction hoisting weight, reduced support construction, short construction period, etc.

The NC-UHPC combined assembly type prestressed concrete box girder comprises a prefabricated NC top plate (11), a prefabricated NC bottom plate (21) and a prefabricated UHPC variable cross-section straight web plate (31), wherein the prefabricated UHPC variable cross-section straight web plate (31) is arranged in such a way that the plate surface areas of the two vertical ends of the web plate are larger than the plate surface area of the middle part of the web plate;

furthermore, the prefabricated UHPC variable cross-section straight web (31) is of an hourglass-shaped structure, wherein the plate surfaces at two vertical ends are respectively and gradually reduced towards the middle part;

furthermore, web vertical prestressed reinforcements (35) are pre-embedded in the prefabricated UHPC variable-cross-section straight web (31), oblique prestressed reinforcements (36) are arranged along the main tensile stress direction, top plate joint reinforcements (18) are pre-embedded in the prefabricated NC top plate (11), bottom plate joint reinforcements (27) are pre-embedded in the prefabricated NC bottom plate (21), web connecting joints (7) are arranged at two ends of each web vertical prestressed reinforcement (35), and the top plate joint reinforcements (18) and the bottom plate joint reinforcements (27) are vertically lapped with the web vertical prestressed reinforcements (35) respectively and are transversely and fixedly connected through the web connecting joints (7);

furthermore, web pre-embedded perforated steel plates (33) are arranged in the centers of the top edge and the bottom edge of the prefabricated UHPC variable cross-section straight web (31), holes in the web pre-embedded perforated steel plates (33) are transversely penetrated through web shear key pre-embedded steel pipes (34) and are firmly welded, and shear key steel bars (8 and 9) are arranged in the holes in the web pre-embedded perforated steel plates (33) and the steel pipes in the web pre-embedded steel pipes (34) in a penetrating mode;

furthermore, web plate reinforcing vertical ribs (32) are arranged in the centers of two opposite sides of the surface of the prefabricated UHPC variable cross-section straight web plate (31) along the longitudinal bridge direction;

further, a top plate reinforcing transverse rib (12) is arranged at the bottom edge of the prefabricated NC top plate (11) along the center of the longitudinal bridge direction, a bottom plate reinforcing transverse rib (22) is arranged at the top edge of the prefabricated NC bottom plate (21) along the center of the longitudinal bridge direction, and the top plate reinforcing transverse rib (12), the bottom plate reinforcing transverse rib (22) and the web plate reinforcing vertical rib (32) are correspondingly arranged;

furthermore, cast-in-place UHPC forms a top plate connecting belt (6) and a bottom plate connecting belt (5) respectively after the prefabricated NC top plates (11) and the prefabricated NC bottom plates (21) are assembled, splicing plates (37) are arranged at two ends of the web pre-buried perforated steel plate (33) along the longitudinal bridge direction, and the splicing plates (37) are connected into a whole through high-strength bolts (38) and are buried between the bottom plate connecting belt (5) and the top plate connecting belt (6);

furthermore, longitudinal prestressed steel bundle corrugated pipelines are arranged in the NC prefabricated top plate (11) and the NC prefabricated bottom plate (21), and the prestressed steel bundles penetrate through the longitudinal prestressed steel bundle corrugated pipelines and are tensioned and anchored through a steel bundle anchorage device (14);

furthermore, cantilever top plate reinforcing longitudinal beams (102) are arranged at cantilevers of the NC prefabricated top plate (11), UHPC prefabricated diagonal braces (10) are arranged at intersection positions of the cantilever top plate reinforcing longitudinal beams (102) and the top plate reinforcing transverse ribs (12), and the UHPC prefabricated diagonal braces (10) are connected with the top plate reinforcing transverse ribs (12) and the prefabricated NC bottom plate (21) through prefabricated diagonal brace UHPC cast-in-place connecting joints (101).

The invention also discloses a construction method of the NC-UHPC combined assembly type prestressed concrete box girder, which comprises the following steps:

step a, erecting temporary brackets on two sides of a pier, and installing an NC prefabricated bottom plate block unit (2) with a pier top section composed of a prefabricated NC bottom plate (21);

step b, installing a prefabricated UHPC solid web plate unit (4) with a pier top section composed of a prefabricated UHPC variable cross-section straight web plate (31), installing a prefabricated NC bottom plate (21) and a pier top section prefabricated UHPC solid web plate shear key penetrating steel bar (8), and pouring a UHPC cast-in-place web plate connecting joint (7);

c, mounting a prefabricated NC top plate block unit (1) formed by a prefabricated NC top plate (11) of the pier top section, mounting a shear key penetrating steel bar of the prefabricated NC top plate and a prefabricated UHPC solid web of the pier top section, and pouring a UHPC cast-in-place connecting joint;

d, mounting a prefabricated NC bottom plate block unit (2) formed by a prefabricated NC bottom plate (21) on the conventional beam section by using a temporary hanger and temporarily fixing the prefabricated NC bottom plate block unit;

step e, installing a prefabricated UHPC web plate unit (3) of a conventional beam section, which is composed of a prefabricated UHPC variable cross-section straight web plate (31), installing a high-strength bolt joint splice plate (37) connected with the finished sections, screwing and fastening high-strength bolts (38), installing a NC prefabricated bottom plate of the conventional beam section and a shear key penetrating steel bar (9) of the UHPC hourglass-shaped prefabricated web plate, pouring UHPC cast-in-place connecting joints, and pouring UHPC cast-in-place prefabricated web plate reinforced vertical rib connecting joints (7);

step f, installing a conventional beam section NC prefabricated roof plate unit (1) by adopting a temporary hanger and temporarily fixing; installing a conventional beam section prefabricated NC top plate (11) and a UHPC prefabricated web shear key penetrating steel bar (8), pouring a UHPC cast-in-place connecting joint, and pouring a UHPC web reinforced vertical rib connecting joint (7);

step g, casting UHPC cast-in-place bottom plate connecting strips (5) and UHPC cast-in-place top plate connecting strips (6) between the installed sections; after the UHPC cast-in-place strip is maintained to reach the design strength, a longitudinal prestressed steel beam anchorage device (14) is installed, a top plate longitudinal prestressed steel beam (13) is tensioned, and then prestressed grouting and anchor sealing are carried out;

and h, repeating the steps d to g by adopting a symmetrical cantilever splicing method, mounting the conventional precast beam sections section by section to full-bridge closure, and tensioning the prestressed closure steel bundles of the top plate and the bottom plate.

The invention also discloses a bridge which is provided with the NC-UHPC combined assembly type prestressed concrete box girder.

The invention has the beneficial effects that: the NC-UHPC combined assembly type prestressed concrete box girder and the construction method thereof disclosed by the invention have the advantages that the NC-UHPC is combined, the advantages of high NC compressive strength and low price are fully utilized, the outstanding advantages of high strength, high elastic modulus, high durability, high toughness, high compactness, low creep and the like of the UHPC are fully exerted, and the NC-UHPC combined assembly type prestressed concrete box girder has the advantages of excellent structural stress performance, light weight, high cost performance, light construction hoisting weight, reduced support construction, short construction period and the like.

Drawings

The invention is further described below with reference to the following figures and examples:

FIG. 1 is a vertical layout view of NC-UHPC combined prefabricated prestressed concrete box girders according to examples I and II of the present invention;

FIG. 2 is a cross-sectional view of an NC-UHPC combined prefabricated prestressed concrete box girder according to embodiment I of the present invention;

FIG. 3 is a cross-sectional view of an NC-UHPC combined prefabricated prestressed concrete box girder according to embodiment II of the present invention;

FIG. 4 is a three-dimensional perspective axial view of an NC-UHPC combined prefabricated prestressed concrete box girder according to embodiment I of the present invention;

FIG. 5 is a three-dimensional perspective axial view of an NC-UHPC combined prefabricated prestressed concrete box girder according to embodiment II of the present invention;

FIG. 6 is a schematic diagram showing the force mechanism of the NC-UHPC combined assembly type prestressed concrete box girder of the embodiment I and the embodiment II of the invention;

FIG. 7 is a typical cross-sectional view of an NC-UHPC combined prefabricated prestressed concrete box girder according to example I of the present invention;

FIG. 8 is a typical cross-sectional view of an NC-UHPC combined prefabricated prestressed concrete box girder according to embodiment II of the present invention;

FIG. 9 is an enlarged view of a portion of FIG. 7 and FIG. 8 at A;

fig. 10 is a partial enlarged view at B in fig. 7 and 8;

FIG. 11 is a schematic view of a three-dimensional exploded structure of a typical segment of an NC-UHPC combined prefabricated prestressed concrete box girder according to embodiment I of the present invention;

FIG. 12 is a schematic view of a three-dimensional exploded structure of a typical segment of an NC-UHPC combined prefabricated prestressed concrete box girder according to embodiment II of the present invention;

FIG. 13 is a schematic three-dimensional structural view of a typical segment precast top plate of an NC-UHPC combined prefabricated prestressed concrete box girder according to example I and example II of the present invention;

FIG. 14 is a schematic three-dimensional structure diagram of a typical segment precast floor slab of an NC-UHPC combined assembly type prestressed concrete box girder according to embodiment I and embodiment II of the present invention;

FIG. 15 is a view of the vertical and transverse arrangements of typical segmental precast webs of NC-UHPC combined prefabricated prestressed concrete box girders according to examples I and II of the present invention;

FIG. 16 is a schematic three-dimensional exploded view of a typical segmental precast web of an NC-UHPC combined prefabricated prestressed concrete box girder according to example I and example II of the present invention;

FIG. 17 is a schematic view showing the steps of a construction method of NC-UHPC combined prefabricated prestressed concrete box girders according to embodiment I and embodiment II of the present invention;

fig. 18 is a schematic view showing the pier-top beam section and a typical segment construction method of the NC-UHPC combined prefabricated prestressed concrete box girder according to the embodiment i and the embodiment ii of the present invention.

Wherein the figures include the following reference numerals: 1-NC prefabricated top plate block unit, 2-NC prefabricated bottom plate block unit, 3-prefabricated UHPC web plate block unit, 4-pier top section UHPC prefabricated solid web plate block unit, 5-bottom plate connecting band, 6-top plate connecting band, 7-web plate reinforcing vertical rib connecting joint, 8-prefabricated NC top plate and shear key penetrating steel bar of UHPC prefabricated variable cross section straight web plate, 9-prefabricated NC bottom plate and shear key penetrating steel bar of UHPC prefabricated variable cross section straight web plate, 10-UHPC prefabricated diagonal brace, 11-prefabricated NC top plate, 12-top plate reinforcing transverse rib, 13-top plate longitudinal prestress steel beam, 14-longitudinal prestress steel beam anchorage, 15-top plate shear key pre-embedded perforated steel plate, 16-top plate shear key pre-embedded steel pipe, 17-top plate shear key pre-embedded penetrating steel bar, 18-top plate joint steel bar, 19-prefabricated NC top plate longitudinal steel bar, 21-prefabricated NC bottom plate, 22-bottom plate reinforcing transverse rib, 23-longitudinal prestressed steel bundles of a bottom plate, 24-prefabricated NC (numerical control) bottom plate shear key embedded perforated steel plates, 25-NC prefabricated bottom plate shear key embedded steel pipes, 26-NC prefabricated bottom plate shear key embedded through steel bars, 27-NC prefabricated bottom plate and reinforced vertical rib connecting joint embedded steel bar joints, 28-NC prefabricated bottom plate longitudinal steel bars, 31-prefabricated UHPC (ultra high performance concrete) variable cross-section straight web plates, 32-web plate reinforced vertical ribs, 33-web plate embedded perforated steel plates, 34-web plate shear key embedded steel pipes, 35-web plate reinforced vertical rib vertical prestressed steel bars, 36-oblique prestressed steel bars, 37-splicing plates, 38-high-strength bolts, 101-prefabricated oblique stay bar UHPC cast-in-place connecting joints and 102-cantilever roof plate reinforced longitudinal beams.

Detailed Description

The NC-UHPC combined assembly type prestressed concrete box girder comprises a prefabricated NC top plate 11, a prefabricated NC bottom plate 21 and a prefabricated UHPC variable cross-section straight web plate 31, wherein the prefabricated UHPC variable cross-section straight web plate 31 is arranged in such a way that the plate surface areas of the two vertical ends of the web plate are larger than the plate surface area of the middle part of the web plate; the prefabricated prestressed concrete box girder consists of a pier top section and a conventional section, wherein the pier top section consists of a prefabricated NC top plate block unit 1, a prefabricated NC bottom plate block unit 2 and a pier top section prefabricated UHPC solid variable-section straight web plate block unit 4; the conventional section is composed of a prefabricated NC top plate block unit 1, a prefabricated NC bottom plate block unit 2 and a prefabricated UHPC variable cross-section straight web plate block unit 3. The prefabricated NC top plate unit 1 is composed of a prefabricated NC top plate 11, the prefabricated NC bottom plate unit 2 is composed of a prefabricated NC bottom plate 21, the UHPC solid variable-section straight web plate unit 4 is composed of a prefabricated UHPC variable-section straight web plate 31, and the prefabricated UHPC variable-section straight web plate 31 of the pier top section is thicker and firmer than a conventional section. The prefabricated UHPC variable cross-section straight web plate unit 3 is composed of a prefabricated UHPC variable cross-section straight web plate 31. The box girder adopts a straight web single-box single-chamber or single-box multi-chamber structure, the height of the web is kept constant, the pier top section is provided with a diaphragm girder, and the bottom of the pier top section is fixedly connected with a pier or provided with a support. The prefabricated NC top plate unit 1, the prefabricated NC bottom plate unit 2, the UHPC prefabricated variable cross-section straight web plate unit 3 and the pier top section prefabricated UHPC solid variable cross-section straight web plate unit (4) are all prefabricated in a factory standard mode. The top edge and the bottom edge of the prefabricated UHPC variable-section straight web plate 31 are the same as the prefabricated NC top plate 11 and the prefabricated NC bottom plate 21 in length along the bridge direction, the length is narrowed to the narrowest part at the center of the web plate, the prefabricated UHPC variable-section straight web plate can be regarded as a variable-section component gradually changed along the height direction of the web plate, and the stress mechanism of the box girder is similar to that of a double-Wolon truss structure. Because the web adopts UHPC, make full use of its high strength mechanical properties, make the board thickness attenuate, simultaneously through carrying out trompil to the web and hollowing out, show and alleviate the structure dead weight, effectively reduce substructure pier cross-sectional area and foundation engineering quantity. The traditional prefabricated box girder segment has large volume and heavy weight, the prefabricated box girder segment is broken into parts and disassembled into the NC top plate, the NC bottom plate and the UHPC web plate which are respectively and separately prefabricated, an inner mold and a supporting system of the prefabricated segment box girder are omitted, the light weight and the miniaturization of a prefabricated part are realized, the transfinite transportation is avoided, and the field hoisting weight is effectively reduced. The main beam adopts UHPC prefabricated open-pore web plates which are high-quality members manufactured in a factory, and the UHPC uses high-strength steel fibers, so that the UHPC has high tensile strength and ductility, and does not need to be configured with reinforcing steel bars, thereby avoiding the corrosion of the reinforcing steel bars caused by salt damage and concrete carbonization, having high durability and further improving the maintenance-free performance of the structure. Because the special structure of the UHPC variable cross-section straight web plate 31 is prefabricated, a hollowed hole formed between the web plate and the web plate can provide good lighting, so that the light in the internal space of the main beam is bright, and the inspection and the management and the protection are convenient. The hollowed holes formed between the webs can ensure good ventilation effect inside and outside the box girder, and effectively reduce the adverse effect of temperature gradient secondary stress generated by the temperature difference inside and outside the box girder on the structure of the box girder.

In this embodiment, the prefabricated UHPC variable cross-section straight web 31 is in an hourglass-shaped structure with vertical plate surfaces at two ends gradually reduced towards the middle part respectively (see fig. 15 and 16); the hollowed holes formed between the webs can provide good lighting, so that the light in the inner space of the girder is bright, and the inspection and the management and the protection are convenient. The hollowed holes formed between the webs can ensure good ventilation effect inside and outside the box girder, and effectively reduce the adverse effect of temperature gradient secondary stress generated by the temperature difference inside and outside the box girder on the structure of the box girder. The prefabricated UHPC variable cross-section straight web plate 31 of the conventional beam section uses high-strength fiber reinforced concrete with the compressive strength not lower than 80MPa, and common steel bars do not need to be arranged in the web plate. The box girder top plate formed by the prefabricated NC top plate 11 and the top plate connecting belt 6 is used as a bearing structure of bridge deck load, and bears the tensile force and pressure load action generated by a main girder together with the prefabricated NC bottom plate 21 and the bottom plate connecting belt 5, the prefabricated UHPC variable cross-section straight web plate 31 can be regarded as a variable cross-section component gradually changed along the height direction of the web plate, and the stress mechanism of the box girder is similar to that of a double-Valley truss structure (see figure 6).

In the embodiment, a web vertical prestressed steel bar 35 is pre-embedded in the prefabricated UHPC variable-cross-section straight web 31, an oblique prestressed steel bar 36 is arranged along a main tensile stress direction, a top plate joint steel bar 18 is pre-embedded in the prefabricated NC top plate 11, a bottom plate joint steel bar 27 is pre-embedded in the prefabricated NC bottom plate 21, web connecting joints 7 are arranged at two ends of the web vertical prestressed steel bar 35, and the top plate joint steel bar 18 and the bottom plate joint steel bar 27 are vertically overlapped with the web vertical prestressed steel bar 35 and are transversely and fixedly connected through the web connecting joints 7; the prefabricated NC top plate 11, the prefabricated NC bottom plate 21 and the prefabricated UHPC variable cross-section straight web plate 31 are connected into a whole through web plate reinforcing vertical rib connecting joints 7 so as to ensure the transverse stiffness and the torsional stiffness of the box girder.

The prefabricated UHPC variable cross-section straight web plate 31 is symmetrically provided with vertical prestressed reinforcements 35 along prefabricated web plate reinforcing vertical ribs on two sides and is provided with oblique prestressed reinforcements 36 along the main tensile stress direction; the method comprises the steps of firstly, temporarily anchoring stretched prestressed tendons on a pedestal, then pouring UHPC, releasing the prestressed reinforcements when the UHPC is maintained to be not lower than 90% of the designed strength value and the prestressed reinforcements are bonded with the UHPC sufficiently, and applying prestress to the hourglass-shaped UHPC prefabricated web plate by means of bonding and anchoring of the UHPC and the prestressed reinforcements. The allocation quantity of the prestressed reinforcements is based on that no tensile stress is generated under the constant load effect, and no crack is generated under the worst design load combination effect.

In the embodiment, a web pre-embedded perforated steel plate 33 is arranged in the center of the top edge and the bottom edge of the prefabricated UHPC variable cross-section straight web 31, holes in the web pre-embedded perforated steel plate 33 are transversely penetrated through a web shear key pre-embedded steel pipe 34 and are firmly welded, and shear key steel bars 8 and 9 penetrate through the holes in the web pre-embedded perforated steel plate 33 and the steel pipe in the web pre-embedded steel pipe 34; prefabricated web plate pre-embedded perforated steel plates 33 are arranged in the centers of the top edge and the bottom edge of a prefabricated UHPC variable-cross-section straight web plate 31 of a conventional beam section, an opening pre-embedded in the hourglass-shaped UHPC prefabricated web plate 31 is transversely crossed by a web plate shear key pre-embedded steel pipe 34 and is firmly welded, and an NC prefabricated top plate and UHPC hourglass-shaped prefabricated web plate shear key penetrating steel bar 8 or an NC prefabricated bottom plate and shear key penetrating steel bar 9 of the UHPC hourglass-shaped prefabricated web plate are arranged in the center of each round hole of the prefabricated web plate pre-embedded perforated steel plate 33 and the center of each steel pipe of the web plate shear key pre-embedded steel pipe 34 (see fig. 9, 10 and 13-16).

In this embodiment, web reinforcing vertical ribs 32 are arranged in the centers of two opposite sides of the surface of the prefabricated UHPC variable cross-section straight web 31 along the longitudinal bridge direction; a top plate reinforcing transverse rib 12 is arranged at the bottom edge of the prefabricated NC top plate 11 along the center of the longitudinal bridge direction, a bottom plate reinforcing transverse rib 22 is arranged at the top edge of the prefabricated NC bottom plate 21 along the center of the longitudinal bridge direction, and the top plate reinforcing transverse rib 12, the bottom plate reinforcing transverse rib 22 and the web plate reinforcing vertical rib 32 are correspondingly arranged; (see fig. 4, 11), the top plate reinforcing cross rib 12, the bottom plate reinforcing cross rib 22 and the web reinforcing vertical rib 32 are aligned in position with each other and equal in thickness.

In the embodiment, cast-in-place UHPC is respectively formed between the prefabricated NC top plates 11 and between the prefabricated NC bottom plates 21 after being assembled to form a top plate connecting band 6 and a bottom plate connecting band 5, splicing plates 37 are respectively arranged at two ends of the web pre-embedded perforated steel plate 33 in the longitudinal bridge direction, and the splicing plates 37 are connected into a whole through high-strength bolts 38 and are embedded between the bottom plate connecting band 5 and the top plate connecting band 6; prefabricated NC top plate units 1 among all the sections are connected by UHPC cast-in-place top plate connecting belts 6; the NC prefabricated bottom plate units 2 are connected by UHPC cast-in-place bottom plate connecting belts 5. The top plate connecting strip 6 and the bottom plate connecting strip 5 are both formed by cast-in-place UHPC at the joint of the assembled prefabricated NC bottom plate 21 and the assembled prefabricated NC top plate 11.

In the embodiment, longitudinal prestressed steel bundle corrugated pipelines are arranged in the NC prefabricated top plate 11 and the prefabricated NC bottom plate 21, and the prestressed steel bundles penetrate through the longitudinal prestressed steel bundle corrugated pipelines and are tensioned and anchored through a steel bundle anchorage 14; referring to fig. 8, 9 and 10, longitudinal prestressed steel bundle corrugated pipes are arranged in the prefabricated NC top plate unit 1 and the prefabricated NC bottom plate unit 2 of the NC-UHPC combined assembly type prestressed concrete box girder, and are connected by longitudinal prestressed steel bundles, and a longitudinal prestressed steel bundle anchorage 14 is arranged at the end of a segment to perform tension anchorage and provide a prestressed stress, so as to offset a tensile stress generated on the section of the girder body by self weight, vehicle load and the like.

In the embodiment, a cantilever top plate reinforcing longitudinal beam 102 is arranged at a cantilever of an NC prefabricated top plate 11, a UHPC prefabricated diagonal brace 10 is arranged at the intersection position of the cantilever top plate reinforcing longitudinal beam 102 and a top plate reinforcing transverse rib 12, and the UHPC prefabricated diagonal brace 10 is connected with the top plate reinforcing transverse rib 12 and a prefabricated NC bottom plate 21 through a prefabricated diagonal brace UHPC cast-in-place connecting joint 101; if the width of the bridge deck needs to be increased, the stress of the cantilever part of the NC prefabricated top plate is assisted by properly increasing the length of the transverse bridge cantilever of the NC prefabricated top plate 11 and arranging the UHPC prefabricated diagonal brace 10 between the NC prefabricated top plate 11 and the NC prefabricated bottom plate 21 on the premise of not increasing the number of boxes or changing the width of the boxes.

The invention also discloses a construction method of the NC-UHPC combined assembly type prestressed concrete box girder, which comprises the following steps:

step a, erecting temporary brackets on two sides of a pier, and installing an NC prefabricated bottom plate block unit (2) with a pier top section composed of a prefabricated NC bottom plate (21);

step b, installing a prefabricated UHPC solid web plate unit (4) with a pier top section composed of a prefabricated UHPC variable cross-section straight web plate (31), installing a prefabricated NC bottom plate (21) and a pier top section prefabricated UHPC solid web plate shear key penetrating steel bar (8), and pouring a UHPC cast-in-place web plate connecting joint (7);

c, mounting a prefabricated NC top plate block unit (1) formed by a prefabricated NC top plate (11) of the pier top section, mounting a shear key penetrating steel bar of the prefabricated NC top plate and a prefabricated UHPC solid web of the pier top section, and pouring a UHPC cast-in-place connecting joint;

d, mounting a prefabricated NC bottom plate block unit (2) formed by a prefabricated NC bottom plate (21) on the conventional beam section by using a temporary hanger and temporarily fixing the prefabricated NC bottom plate block unit;

step e, installing a prefabricated UHPC web plate unit (3) of a conventional beam section, which is composed of a prefabricated UHPC variable cross-section straight web plate (31), installing a high-strength bolt joint splice plate (37) connected with the finished sections, screwing and fastening high-strength bolts (38), installing a NC prefabricated bottom plate of the conventional beam section and a shear key penetrating steel bar (9) of the UHPC hourglass-shaped prefabricated web plate, pouring UHPC cast-in-place connecting joints, and pouring UHPC cast-in-place prefabricated web plate reinforced vertical rib connecting joints (7);

step f, installing a conventional beam section NC prefabricated roof plate unit (1) by adopting a temporary hanger and temporarily fixing; installing a conventional beam section prefabricated NC top plate (11) and a UHPC prefabricated web shear key penetrating steel bar (8), pouring a UHPC cast-in-place connecting joint, and pouring a UHPC web reinforced vertical rib connecting joint (7);

step g, casting UHPC cast-in-place bottom plate connecting strips (5) and UHPC cast-in-place top plate connecting strips (6) between the installed sections; after the UHPC cast-in-place strip is maintained to reach the design strength, a longitudinal prestressed steel beam anchorage device (14) is installed, a top plate longitudinal prestressed steel beam (13) is tensioned, and then prestressed grouting and anchor sealing are carried out;

step h, repeating the step d to the step g by adopting a symmetrical cantilever splicing method, installing the conventional precast beam sections segment by segment to full-bridge closure, and tensioning the prestressed closure steel bundles of the top plate and the bottom plate;

and i, dismantling the temporary support of the side span and the temporary brackets on the two sides of the pier to complete the construction of the girder.

Referring to fig. 6 to 7 and 9 to 12, the embedded steel pipes 16, 25 and 34 embedded in the NC precast top plate shear key, the NC precast bottom plate shear key and the precast web plate shear key are used as shear pins of the shear key and inner formworks of the circular holes of the shear key.

The cast-in-situ UHPC filling gaps among the NC prefabricated top plate unit 1, the NC prefabricated top plate unit 2, the UHPC hourglass-shaped prefabricated web plate unit 3 or the pier top section UHPC prefabricated solid web plate unit 4 adopts short steel fibers with the length not more than 15mm to ensure the fluidity of the cast-in-situ UHPC, and fills and compacts the gaps by the UHPC by filling and compacting the short steel fibers which are embedded in the NC prefabricated top plate shear key embedded steel pipe 16 and the NC prefabricated bottom plate shear key embedded steel pipe 25 into the gaps.

Compared with the prior art, the invention has the following beneficial effects:

(1) the NC prefabricated top plate, the NC prefabricated bottom plate and the UHPC prefabricated web plate are prefabricated in advance in a factory and are installed on site, the solidification time of the UHPC cast-in-place wet joint strip is short, and the erection period of the box girder is greatly shortened.

(2) The NC prefabricated top plate, the NC prefabricated bottom plate and the UHPC prefabricated web plate can be prefabricated in a standardized way by adopting a shaped template, and the flat curve, the vertical curve, the pre-arch, the gradual change of the ultrahigh cross slope of the bridge deck and the like of the bridge can be adjusted and adapted by utilizing the UHPC cast-in-place wet joint among all sections.

(3) The engineering load of the infrastructure and the foundation is reduced. Because the web adopts UHPC, make full use of its high strength mechanical properties, make the board thickness attenuate, simultaneously through carrying out trompil to the web and hollowing out, show and alleviate the structure dead weight, effectively reduce substructure pier cross-sectional area and foundation engineering quantity.

(4) The traditional prefabricated box girder segment has large volume and heavy weight, the prefabricated box girder segment is broken into parts and disassembled into the NC top plate, the NC bottom plate and the UHPC web plate which are respectively and separately prefabricated, an inner mold and a supporting system of the prefabricated segment box girder are omitted, the light weight and the miniaturization of a prefabricated part are realized, the transfinite transportation is avoided, and the field hoisting weight is effectively reduced.

(5) The UHPC material is used for the cast-in-place joint of the connecting node member, the material consumption is less, the structure is simple, the construction period is shortened, the strength of the connecting section is enhanced, and the defect that the connecting node of the prefabricated member is weak in stress is overcome. The wet joint connection is guaranteed to be no longer a weak link of the prefabricated assembly structure.

(6) Energy conservation, emission reduction, low carbon and environmental protection. As the number of materials used in the upper and lower structures is greatly reduced, compared with the NC box girder bridge with the same specification, the CO in the construction period₂The emission amount is reduced.

(7) And the maintenance-free performance is improved. The main beam adopts UHPC prefabricated open-pore web plates which are high-quality members manufactured in a factory, and the UHPC uses high-strength steel fibers, so that the UHPC has high tensile strength and ductility, and does not need to be configured with reinforcing steel bars, thereby avoiding the corrosion of the reinforcing steel bars caused by salt damage and concrete carbonization, having high durability and further improving the maintenance-free performance of the structure.

(8) The hollowed holes in the web plate can provide good lighting, so that the light in the inner space of the main beam is bright, and the inspection and the management and the protection are convenient.

(9) The hollowed holes in the web plate can ensure good ventilation effect inside and outside the box girder, and effectively reduce the adverse effect of temperature gradient secondary stress generated by the temperature difference inside and outside the box girder on the box girder structure.

Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.

Claims (11)

1. The utility model provides a NC-UHPC combination assembled prestressed concrete box girder which characterized in that: the prefabricated UHPC variable cross-section straight web plate comprises a prefabricated NC top plate (11), a prefabricated NC bottom plate (21) and a prefabricated UHPC variable cross-section straight web plate (31), wherein the prefabricated UHPC variable cross-section straight web plate (31) is arranged in such a way that the area of the surfaces of the two vertical end plates of the web plate is larger than that of the surface of the middle plate.

2. The NC-UHPC combined prefabricated prestressed concrete box girder according to claim 1, wherein: the prefabricated UHPC variable cross-section straight web plate (31) is of a hourglass-shaped structure with vertical two end plate surfaces gradually reduced towards the middle part respectively.

3. The NC-UHPC combined prefabricated prestressed concrete box girder according to claim 2, wherein: the prefabricated UHPC variable cross-section straight web plate is characterized in that web plate vertical prestressed reinforcements (35) are pre-embedded in the prefabricated UHPC variable cross-section straight web plate (31), oblique prestressed reinforcements (36) are arranged along the main tensile stress direction, top plate joint reinforcements (18) are pre-embedded in the prefabricated NC top plate (11), bottom plate joint reinforcements (27) are pre-embedded in the prefabricated NC bottom plate (21), web plate connecting joints (7) are arranged at two ends of the web plate vertical prestressed reinforcements (35), and the top plate joint reinforcements (18) and the bottom plate joint reinforcements (27) are vertically overlapped with the web plate vertical prestressed reinforcements (35) respectively and are transversely and fixedly connected through the web plate connecting joints (7).

4. The NC-UHPC combined prefabricated prestressed concrete box girder according to claim 3, wherein: the prefabricated UHPC variable cross-section straight web plate (31) is characterized in that web plate pre-embedded perforated steel plates (33) are arranged in the centers of the top edge and the bottom edge of the prefabricated UHPC variable cross-section straight web plate (31), holes in the web plate pre-embedded perforated steel plates (33) are transversely crossed by web plate shear key pre-embedded steel pipes (34) and are firmly welded, and shear key steel bars (8, 9) are arranged in the holes in the web plate pre-embedded perforated steel plates (33) and the steel pipes in the web plate pre-embedded steel pipes (34) in a penetrating mode.

5. The NC-UHPC combined prefabricated prestressed concrete box girder according to claim 4, wherein: and web plate reinforcing vertical ribs (32) are arranged in the centers of two opposite sides of the surface of the prefabricated UHPC variable-cross-section straight web plate (31) along the longitudinal bridge direction.

6. The NC-UHPC combined prefabricated prestressed concrete box girder according to claim 5, wherein: the bottom edge of the prefabricated NC top plate (11) is provided with a top plate reinforcing transverse rib (12) along the center of the longitudinal bridge direction, the top edge of the prefabricated NC bottom plate (21) is provided with a bottom plate reinforcing transverse rib (22) along the center of the longitudinal bridge direction, and the top plate reinforcing transverse rib (12), the bottom plate reinforcing transverse rib (22) and the web plate reinforcing vertical rib (32) are correspondingly arranged.

7. The NC-UHPC combined prefabricated prestressed concrete box girder according to claim 6, wherein: cast-in-situ UHPC forms a top plate connecting belt (6) and a bottom plate connecting belt (5) respectively after being assembled between the prefabricated NC top plates (11) and between the prefabricated NC bottom plates (21), splicing plates (37) are arranged at two ends of the web pre-buried perforated steel plate (33) along the longitudinal bridge direction, and the splicing plates (37) are connected into a whole through high-strength bolts (38) and are buried between the bottom plate connecting belt (5) and the top plate connecting belt (6).

8. The NC-UHPC combined prefabricated prestressed concrete box girder according to claim 7, wherein: longitudinal prestressed steel bundle corrugated pipelines are arranged in the NC prefabricated top plate (11) and the NC prefabricated bottom plate (21), and the prestressed steel bundles penetrate through the longitudinal prestressed steel bundle corrugated pipelines and are tensioned and anchored through a steel bundle anchorage device (14).

9. The NC-UHPC combined prefabricated prestressed concrete box girder according to any one of claims 1 to 8, wherein: a cantilever top plate reinforcing longitudinal beam (102) is arranged at a cantilever of an NC prefabricated top plate (11), a UHPC prefabricated diagonal brace (10) is arranged at the intersection position of the cantilever top plate reinforcing longitudinal beam (102) and a top plate reinforcing transverse rib (12), and the UHPC prefabricated diagonal brace (10) is connected with the top plate reinforcing transverse rib (12) and a prefabricated NC bottom plate (21) through a prefabricated diagonal brace UHPC cast-in-place connecting joint (101).

10. The construction method of the NC-UHPC combined assembly type prestressed concrete box girder as claimed in claim 1, wherein: the method comprises the following steps:

step a, erecting temporary brackets on two sides of a pier, and installing an NC prefabricated bottom plate block unit (2) with a pier top section composed of a prefabricated NC bottom plate (21);

step b, installing a prefabricated UHPC solid web plate unit (4) with a pier top section composed of a prefabricated UHPC variable cross-section straight web plate (31), installing a prefabricated NC bottom plate (21) and a pier top section prefabricated UHPC solid web plate shear key penetrating steel bar (8), and pouring a UHPC cast-in-place web plate connecting joint (7);

c, mounting a prefabricated NC top plate block unit (1) formed by a prefabricated NC top plate (11) of the pier top section, mounting a shear key penetrating steel bar of the prefabricated NC top plate and a prefabricated UHPC solid web of the pier top section, and pouring a UHPC cast-in-place connecting joint;

d, mounting a prefabricated NC bottom plate block unit (2) formed by a prefabricated NC bottom plate (21) on the conventional beam section by using a temporary hanger and temporarily fixing the prefabricated NC bottom plate block unit;

step e, installing a prefabricated UHPC web plate unit (3) of a conventional beam section, which is composed of a prefabricated UHPC variable cross-section straight web plate (31), installing a high-strength bolt joint splice plate (37) connected with the finished sections, screwing and fastening high-strength bolts (38), installing a NC prefabricated bottom plate of the conventional beam section and a shear key penetrating steel bar (9) of the UHPC hourglass-shaped prefabricated web plate, pouring UHPC cast-in-place connecting joints, and pouring UHPC cast-in-place prefabricated web plate reinforced vertical rib connecting joints (7);

step f, installing a conventional beam section NC prefabricated roof plate unit (1) by adopting a temporary hanger and temporarily fixing; installing a conventional beam section prefabricated NC top plate (11) and a UHPC prefabricated web shear key penetrating steel bar (8), pouring a UHPC cast-in-place connecting joint, and pouring a UHPC web reinforced vertical rib connecting joint (7);

step g, casting UHPC cast-in-place bottom plate connecting strips (5) and UHPC cast-in-place top plate connecting strips (6) between the installed sections; after the UHPC cast-in-place strip is maintained to reach the design strength, a longitudinal prestressed steel beam anchorage device (14) is installed, a top plate longitudinal prestressed steel beam (13) is tensioned, and then prestressed grouting and anchor sealing are carried out;

and h, repeating the steps d to g by adopting a symmetrical cantilever splicing method, mounting the conventional precast beam sections section by section to full-bridge closure, and tensioning the prestressed closure steel bundles of the top plate and the bottom plate.

11. A bridge, characterized in that: the bridge is provided with the NC-UHPC combined assembled prestressed concrete box girder of any one of claims 1 to 8.

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