CN113789711B - NC-UHPC combined assembled prestressed concrete box girder, construction method and bridge thereof - Google Patents
NC-UHPC combined assembled prestressed concrete box girder, construction method and bridge thereof Download PDFInfo
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- CN113789711B CN113789711B CN202111277665.3A CN202111277665A CN113789711B CN 113789711 B CN113789711 B CN 113789711B CN 202111277665 A CN202111277665 A CN 202111277665A CN 113789711 B CN113789711 B CN 113789711B
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D2/00—Bridges characterised by the cross-section of their bearing spanning structure
- E01D2/04—Bridges characterised by the cross-section of their bearing spanning structure of the box-girder type
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D21/00—Methods or apparatus specially adapted for erecting or assembling bridges
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D2101/00—Material constitution of bridges
- E01D2101/20—Concrete, stone or stone-like material
- E01D2101/24—Concrete
- E01D2101/26—Concrete reinforced
- E01D2101/28—Concrete reinforced prestressed
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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 formed by arranging the plate surface area of the two vertical ends of the web plate to be larger than the plate surface area of the middle part, and the NC-UHPC combined prestressed concrete box girder fully utilizes the advantages of high NC compressive strength and low price, fully exerts the outstanding advantages of high strength, high elastic modulus, high durability, high toughness, high compactness, low creep and the like of the UHPC, and has the advantages of excellent structural stress performance, light weight, high cost performance, light construction hoisting weight, reduced bracket construction, short construction period and the like.
Description
Technical Field
The invention relates to the field of bridges, in particular to an NC-UHPC combined assembled prestressed concrete box girder, a construction method and a bridge thereof.
Background
Currently, china is greatly expanding prefabricated assembled bridges and composite structure bridges. Compared with the cast-in-place concrete box girder, the prefabricated box girder and the combined structure box girder have the advantages of remarkably improving construction quality and green construction benefit, effectively reducing construction risks, adversely affecting traffic and environment by construction, improving production efficiency and the like. The traditional prefabricated segment prestressed concrete box girder has high construction precision requirement, relatively long prefabrication period and high requirement on girder storage and transportation, and the requirements on site construction equipment are high no matter the whole hole segment assembly of a bridge girder erection machine or the cantilever segment assembly is adopted. The traditional concrete box girder has the defects of easy cracking of web plates, great self weight and the like because of low self tensile 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 post-maintenance workload, concentrated stress, complex stress and the like of the steel-concrete connection node exist at the same time. Ultra-High Performance Concrete (UHPC for short) is a high-density cement-based composite engineering material prepared according to the principle of maximum bulk density (reducing porosity and macropores) and low water-gel ratio, and has the outstanding advantages of high strength, high elastic modulus, high durability, high toughness, high compactness, low creep and the like. Many engineering practices show that UHPC can obviously reduce the size of the component, lighten the dead weight of the structure and increase the spanning capacity under the condition of ensuring the same strength and durability.
In bridge engineering, although UHPC has been widely used in various aspects such as combining bridge deck pavement structures and reinforcing old bridges, one of the main factors restricting the development of UHPC bridge structures from the current use situation is its high cost and high self-shrinkage characteristics. In the technical field of bridge structural engineering, if the main structural material is fully made of UHPC, the UHPC material is uneconomical, and the ultrahigh mechanical property of the bridge structure cannot be fully utilized because the bridge structure needs to meet a plurality of performance targets such as strength, rigidity and stability, so that the advantages of the UHPC material are wasted.
Disclosure of Invention
In view of the above, the NC-UHPC combined assembly type prestressed concrete box girder and the construction method thereof fully utilize the advantages of high NC compressive strength and low price by combining NC-UHPC, fully exert the outstanding advantages of UHPC such as high strength, high elastic modulus, high durability, high toughness, high compactness, low creep and the like, and have the advantages of excellent structural stress performance, light weight, high cost performance, light construction hoisting weight, reduced bracket construction, short construction period and the like.
The NC-UHPC combined assembled prestressed concrete box girder comprises a prefabricated NC top plate (11), a prefabricated NC bottom plate (21) and a prefabricated UHPC variable-section straight web (31), wherein the prefabricated UHPC variable-section straight web (31) is arranged in such a way that the surface area of two vertical ends of the web is larger than that of the middle plate;
further, the prefabricated UHPC variable cross-section straight web plates (31) are of an hourglass structure with the vertical two end plate surfaces gradually reduced towards the middle part respectively;
further, web vertical prestress steel bars (35) are embedded in the prefabricated UHPC variable-section straight web plates (31) and oblique prestress steel bars (36) are arranged along the main tensile stress direction, top plate joint steel bars (18) are embedded in the prefabricated NC top plate (11), bottom plate joint steel bars (27) are embedded in the prefabricated NC bottom plate (21), web connecting joints (7) are arranged at two ends of the web vertical prestress steel bars (35), and the top plate joint steel bars (18) and the bottom plate joint steel bars (27) are vertically overlapped with the web vertical prestress steel bars (35) respectively and are fixedly connected transversely through the web connecting joints (7);
Further, web embedded perforated steel plates (33) are arranged at the centers of the top edge and the bottom edge of the prefabricated UHPC variable-section straight web plate (31), holes in the web embedded perforated steel plates (33) are transversely crossed by web shear key embedded steel pipes (34) and are firmly welded, and shear key steel bars (8, 9) are arranged in the holes in the web embedded perforated steel plates (33) and the steel pipes in the web embedded steel pipes (34) in a penetrating manner;
further, web reinforcing vertical ribs (32) are arranged at the centers of two opposite sides of the plate surface of the prefabricated UHPC variable-section straight web (31) along the longitudinal bridge direction;
Further, a top plate reinforcing transverse rib (12) is arranged at the center of the bottom edge of the prefabricated NC top plate (11) along the longitudinal bridge direction, a bottom plate reinforcing transverse rib (22) is arranged at the center of the top edge of the prefabricated NC bottom plate (21) along 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;
Further, after being assembled between the prefabricated NC top plates (11) and between the prefabricated NC bottom plates (21), the cast-in-situ UHPC respectively forms a top plate connecting belt (6) and a bottom plate connecting belt (5), splice plates (37) are arranged at two ends of the web embedded perforated steel plates (33) along the longitudinal bridge direction, and the splice plates (37) are connected into a whole through high-strength bolts (38) and embedded between the bottom plate connecting belt (5) and the top plate connecting belt (6);
Further, longitudinal prestress steel beam corrugated pipes are arranged in the NC prefabricated top plate (11) and the prefabricated NC bottom plate (21), and the prestress steel beams penetrate through the longitudinal prestress steel beam corrugated pipes and are tensioned and anchored through steel beam anchors (14);
Further, cantilever top plate reinforcing longitudinal beams (102) are arranged at cantilever positions of NC prefabricated top plates (11), UHPC prefabricated diagonal bracing rods (10) are arranged at intersection positions of the cantilever top plate reinforcing longitudinal beams (102) and top plate reinforcing transverse ribs (12), and the UHPC prefabricated diagonal bracing rods (10) are connected with the top plate reinforcing transverse ribs (12) and the prefabricated NC bottom plates (21) through prefabricated diagonal bracing rod UHPC cast-in-situ connection 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, temporary brackets are erected on two sides of a pier, and NC prefabricated bottom plate block units (2) formed by prefabricated NC bottom plates (21) are installed on the top sections of the piers;
B, installing a prefabricated UHPC solid web plate unit (4) formed by a prefabricated UHPC variable-section straight web plate (31) at the pier top section, installing a prefabricated NC bottom plate (21) and a prefabricated UHPC solid web shear key penetrating through a steel bar (8) at the pier top section, and pouring a UHPC cast-in-situ web connecting joint (7);
c, installing a prefabricated NC top plate block unit (1) formed by a pier top section prefabricated NC top plate (11), installing a NC prefabricated top plate and a pier top section UHPC prefabricated solid web shear key penetrating through a reinforcing steel bar, and pouring a UHPC cast-in-situ connection joint;
D, installing a prefabricated NC bottom plate block unit (2) formed by prefabricating an NC bottom plate (21) by adopting a temporary hanging bracket through a conventional beam Duan You, and temporarily fixing;
Step e, installing a prefabricated UHPC web plate unit (3) formed by prefabricating a UHPC variable-section straight web plate (31) by a conventional beam Duan You, installing a high-strength bolt connecting joint splice plate (37) connected with the completed section, screwing and fixing a high-strength bolt (38), installing a conventional beam section NC prefabricated bottom plate and a UHPC hourglass-shaped prefabricated web plate shear key penetrating steel bar (9), pouring a UHPC cast-in-situ connecting joint, and pouring a UHPC cast-in-situ prefabricated web plate reinforcing vertical rib connecting joint (7);
F, installing a conventional beam section NC prefabricated roof plate block unit (1) by adopting a temporary hanging bracket and temporarily fixing, installing a conventional beam Duan Yuzhi NC roof plate (11) and a UHPC prefabricated web shear key penetrating through a steel bar (8), pouring a UHPC cast-in-situ connection joint, and pouring a UHPC web reinforced vertical rib connection joint (7);
step g, pouring a UHPC cast-in-situ bottom plate connecting belt (5) between the installed sections and a UHPC cast-in-situ top plate connecting belt (6), installing a longitudinal prestressed steel beam anchor (14) and tensioning a top plate longitudinal prestressed steel beam (13) after the UHPC cast-in-situ belt is cured to reach the design strength, and then performing prestressed grouting and anchor sealing;
And h, repeating the steps d-g by adopting a symmetrical cantilever assembly method, installing the conventional precast beam Duan Zhi section by section, closing the full bridge, tensioning the top plate and the bottom plate, and closing the steel beam by prestress.
The invention also discloses a bridge, which is provided with the NC-UHPC combined assembly type prestressed concrete box girder.
The NC-UHPC combined assembly type prestressed concrete box girder and the construction method thereof disclosed by the invention have the beneficial effects that the NC-UHPC is combined, 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 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 bracket construction, short construction period and the like.
Drawings
The invention is further described below with reference to the accompanying drawings and examples:
FIG. 1 is a floor plan of an NC-UHPC composite fabricated prestressed concrete box girder of example I and example II of the present invention;
FIG. 2 is a cross-sectional layout view of an NC-UHPC composite fabricated prestressed concrete box girder according to embodiment I of the present invention;
FIG. 3 is a cross-sectional layout view of an NC-UHPC composite fabricated prestressed concrete box girder according to embodiment II of the present invention;
FIG. 4 is a three-dimensional perspective view of an NC-UHPC composite fabricated prestressed concrete box girder according to embodiment I of the present invention;
FIG. 5 is a three-dimensional perspective view of an NC-UHPC composite fabricated prestressed concrete box girder of embodiment II of the present invention;
FIG. 6 is a schematic diagram of the stress mechanism of NC-UHPC combined assembly type prestressed concrete box girders according to the embodiment I and the embodiment II of the invention;
FIG. 7 is a typical cross-sectional view of an NC-UHPC fabricated prestressed concrete box girder of embodiment I of the present invention;
FIG. 8 is a typical cross-sectional view of an NC-UHPC fabricated prestressed concrete box girder of embodiment II of the present invention;
Fig. 9 is a partial enlarged view at a in fig. 7 and 8;
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 composite fabricated 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 fabricated prestressed concrete box girder according to embodiment II of the present invention;
FIG. 13 is a schematic three-dimensional view of a typical segmented prefabricated roof panel of NC-UHPC fabricated prestressed concrete box girders of example I and example II of the present invention;
FIG. 14 is a schematic three-dimensional view of a typical segmented precast floor segment of an NC-UHPC modular prestressed concrete box girder of example I and example II of the present invention;
FIG. 15 is an elevational and cross-sectional layout view of a typical segmented precast web of an NC-UHPC modular prestressed concrete box girder of embodiments I and II of the present invention;
FIG. 16 is a schematic view of a three-dimensional exploded view of a typical segmented precast web of an NC-UHPC modular prestressed concrete box girder of example I and example II of the present invention;
FIG. 17 is a schematic diagram showing the steps of a construction method of NC-UHPC combined assembly type prestressed concrete box girders according to the embodiment I and the embodiment II of the present invention;
Fig. 18 is a schematic illustration of pier top beam segments and typical segment construction method steps of NC-UHPC composite fabricated prestressed concrete box girders according to example I and example II of the present invention.
Wherein the above figures include the following reference numerals: 1-NC prefabricated roof plate unit, 2-NC prefabricated bottom plate unit, 3-prefabricated UHPC web plate unit, 4-pier top section UHPC prefabricated solid web plate unit, 5-bottom plate connecting belt, 6-roof connecting belt, 7-web reinforced vertical rib connecting joint, 8-prefabricated NC roof and UHPC prefabricated variable cross section straight web shear key penetrating steel bar, 9-prefabricated NC bottom plate and UHPC prefabricated variable cross section straight web shear key penetrating steel bar, 10-UHPC prefabricated diagonal brace, 11-prefabricated NC roof, 12-roof reinforced transverse rib, 13-roof longitudinal prestress steel beam, 14-longitudinal prestress steel beam anchor, 15-roof shear key embedded perforated steel plate, 16-roof shear key embedded steel pipe, 17-roof shear key embedded penetrating steel bar, 18-roof joint steel bar, the reinforced concrete vertical beam comprises the following components of a 19-prefabricated NC top plate longitudinal steel bar, a 21-prefabricated NC bottom plate, a 22-bottom plate reinforcing transverse rib, a 23-bottom plate longitudinal prestressed steel beam, a 24-prefabricated NC bottom plate shear key embedded perforated steel plate, a 25-NC prefabricated bottom plate shear key embedded steel tube, a 26-NC prefabricated bottom plate shear key embedded penetrating steel bar, a 27-NC prefabricated bottom plate and reinforcing vertical rib connecting joint embedded steel bar joint, a 28-NC prefabricated bottom plate longitudinal steel bar, a 31-prefabricated UHPC variable-section straight web, a 32-web reinforcing vertical rib, a 33-web embedded perforated steel plate, a 34-web shear key embedded steel tube, a 35-web reinforcing vertical rib prestressed steel bar, a 36-oblique prestressed steel bar, a 37-splice plate, a 38-high-strength bolt, a 101-prefabricated diagonal brace UHPC cast-in-situ connecting joint and a 102-cantilever top plate reinforcing longitudinal beam.
Detailed Description
The NC-UHPC combined assembled 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 vertical two end plate surface areas of the prefabricated UHPC variable cross-section straight web plate 31 are larger than the middle plate surface area, the assembled prestressed concrete box girder consists of a pier top section and a conventional section, the pier top section consists of a prefabricated NC top plate unit 1, a prefabricated NC bottom plate unit 2 and a pier top section prefabricated UHPC solid variable cross-section straight web plate unit 4, and the conventional section consists of a prefabricated NC top plate unit 1, a prefabricated NC bottom plate unit 2 and a prefabricated UHPC variable cross-section straight web plate unit 3. The prefabricated NC top plate block unit 1 is composed of a prefabricated NC top plate 11, the prefabricated NC bottom plate block unit 2 is composed of a prefabricated NC bottom plate 21, and the UHPC solid variable cross-section straight web plate block unit 4 is composed of a prefabricated UHPC variable cross-section straight web plate 31, except that the prefabricated UHPC variable cross-section straight web plate 31 of the pier top section is thicker than that of the conventional section. The prefabricated UHPC variable-section straight web plate unit 3 is composed of prefabricated UHPC variable-section straight webs 31. The box girder adopts a straight web single box single chamber or single box multi-chamber structure, the girder is equal in height, the web height is kept unchanged, the pier top section is provided with a diaphragm girder, and the pier top section girder bottom is fixedly connected with a pier or is provided with a support. The NC top plate unit 1 is prefabricated, the NC bottom plate unit 2 is prefabricated, the UHPC prefabricated variable-section straight web plate unit 3 is prefabricated, and the pier top section prefabricated UHPC solid variable-section straight web plate unit (4) is prefabricated in a factory standardized mode. The top edge and the bottom edge of the prefabricated UHPC variable-section straight web 31 are the same as the length of the prefabricated NC top plate 11 and the prefabricated NC bottom plate 21 along the bridge direction, and are narrowest at the center of the web, so that the prefabricated UHPC variable-section straight web can be regarded as a variable-section member gradually changing along the height direction of the web, and the stress mechanism of the box girder is similar to that of a double-Wolen truss structure. Because the web adopts UHPC, the high-strength mechanical property of the web is fully utilized, the thickness of the plate is thinned, and meanwhile, the structural dead weight is obviously reduced by perforating and hollowing the web, and the bridge pier cross section area of the lower structure and the quantity of basic engineering are effectively reduced. The traditional precast box girder segment has large volume and heavy weight, the precast box girder segment is integrated into zero, the precast box girder segment is disassembled into the NC top plate, the NC bottom plate and the UHPC web plate which are precast separately, an inner die and a supporting system of the precast box girder of the precast segment are omitted, the weight reduction and the miniaturization of precast components are realized, overrun transportation is avoided, and the on-site hoisting weight is effectively reduced. The UHPC prefabricated perforated web plate is a high-quality member manufactured in a factory, and the UHPC is made of high-strength steel fibers, so that the UHPC prefabricated perforated web plate has high tensile strength and ductility, and no steel bars are required to be arranged, so that the corrosion of the steel bars caused by salt damage and concrete carbonization cannot occur, the UHPC prefabricated perforated web plate has high durability, and the maintenance-free performance of the structure is further improved. Due to the special structure of the prefabricated UHPC variable-section straight web plate 31, the hollowed-out holes formed between the web plates can provide good lighting, so that the inner space of the main beam is bright in light, and the inspection and the management and the protection are convenient. The hollowed-out holes formed between the webs can ensure good ventilation effect inside and outside the box girder, and effectively reduce adverse effect of temperature gradient secondary stress generated by temperature difference inside and outside the box girder on the box girder structure.
In this embodiment, the vertical two end plates of the prefabricated UHPC variable-section straight web 31 are respectively reduced to the middle part to form an hourglass structure (see fig. 15 and 16), and the hollowed holes formed between the webs can provide good lighting, so that the light of the inner space of the main beam is bright, and the inspection and the management and the protection are convenient. The hollowed-out holes formed between the webs can ensure good ventilation effect inside and outside the box girder, and effectively reduce adverse effect of temperature gradient secondary stress generated by temperature difference inside and outside the box girder on the box girder structure. The prefabricated UHPC variable cross-section straight web 31 of the conventional beam section uses high-strength fiber reinforced concrete with compressive strength not lower than 80MPa, and common steel bars are not required to be arranged in the web. The box girder top plate formed by the prefabricated NC top plate 11 and the top plate connecting belt 6 is used as a bridge deck load bearing structure, and together with the prefabricated NC bottom plate 21 and the bottom plate connecting belt 5, bears the tensile and compressive load action generated by the main girder, the prefabricated UHPC variable-section straight web 31 can be regarded as a variable-section member gradually changing along the height direction of the web, and the stress mechanism of the box girder is similar to that of a double-walen truss structure (see fig. 6).
In this embodiment, the vertical pre-stressed web plate 35 is pre-embedded in the vertical web plate 31 of the prefabricated UHPC variable cross section, and the oblique pre-stressed web plate 36 is arranged along the direction of the main tensile stress, the top plate joint reinforcement 18 is pre-embedded in the top plate 11 of the prefabricated NC, the bottom plate joint reinforcement 27 is pre-embedded in the bottom plate 21 of the prefabricated NC, the two ends of the vertical pre-stressed web plate 35 are respectively provided with the web plate connecting joints 7, the top plate joint reinforcement 18 and the bottom plate joint reinforcement 27 are respectively vertically overlapped with the vertical pre-stressed web plate 35 and are transversely and fixedly connected through the web plate connecting joints 7, and the vertical web plate reinforcing rib connecting joints 7 are connected to form a whole so as to ensure the transverse rigidity of the top plate 11 of the prefabricated NC bottom plate 21 and the vertical web plate 31 of the prefabricated UHPC variable cross section and the torsional rigidity of the box girder.
The vertical prestress steel bars 35 are symmetrically arranged along the vertical ribs of the prefabricated web plates at two sides of the prefabricated UHPC variable-section straight web plate 31, the inclined prestress steel bars 36 are configured along the direction of main tensile stress, the tensioned prestress steel bars are temporarily anchored on a pedestal, then UHPC is poured, when the UHPC maintenance reaches not less than 90% of the designed strength value, the prestress steel bars are loosened when the prestress steel bars and the UHPC are ensured to be sufficiently bonded, and the prestress is applied to the hourglass-shaped UHPC prefabricated web plates by means of the bonding anchoring of the UHPC and the prestress steel bars. The number of the prestressed reinforcement is based on the fact that no tensile stress is generated under the action of constant load, and no cracks are generated under the action of the combination of the least unfavorable design load.
In this embodiment, web embedded perforated steel plates 33 are disposed at the top edge and bottom edge centers of the prefabricated UHPC variable-section straight web 31, the perforated holes on the web embedded perforated steel plates 33 are traversed and welded firmly by using web shear key embedded steel pipes 34, shear key steel bars 8 and 9 are disposed in the perforated holes of the web embedded perforated steel plates 33 and the steel pipes of the web embedded steel pipes 34 in a penetrating manner, prefabricated web embedded perforated steel plates 33 are disposed at the top edge and bottom edge centers of the prefabricated UHPC variable-section straight web 31 of the conventional beam section, the perforated holes embedded in the hourglass-shaped UHPC prefabricated web 31 are traversed and welded firmly by using web shear key embedded steel pipes 34, NC prefabricated top plates and UHPC hourglass-shaped prefabricated web shear key penetrating steel bars 8 or NC prefabricated bottom plates and shear key penetrating steel bars 9 of the UHPC hourglass-shaped prefabricated web are disposed at the center of each round hole of the prefabricated web embedded perforated steel plates 33 and at the center of each steel pipe of the web shear key embedded steel pipes 34 (see fig. 9, 10, 13-16).
In this embodiment, web reinforcing vertical ribs 32 are disposed at the centers of two opposite sides of the plate surface of the prefabricated UHPC variable-section straight web 31 along the longitudinal bridge direction, a top plate reinforcing transverse rib 12 is disposed at the center of the bottom edge of the prefabricated NC top plate 11 along the longitudinal bridge direction, a bottom plate reinforcing transverse rib 22 is disposed at the center of the top edge of the prefabricated NC bottom plate 21 along the longitudinal bridge direction, and the top plate reinforcing transverse rib 12, the bottom plate reinforcing transverse rib 22 and the web reinforcing vertical ribs 32 are correspondingly disposed (see fig. 4 and 11), and the positions of the top plate reinforcing transverse rib 12, the bottom plate reinforcing transverse rib 22 and the web reinforcing vertical ribs 32 are mutually aligned, and the thicknesses are equal.
In this embodiment, after the prefabricated NC top plates 11 and the prefabricated NC bottom plates 21 are assembled, the cast-in-situ UHPC respectively forms a top plate connecting band 6 and a bottom plate connecting band 5, two ends of the web pre-buried perforated steel plate 33 along the longitudinal bridge direction are respectively provided with a splice plate 37, the splice plates 37 are connected into a whole by high-strength bolts 38 and are embedded between the bottom plate connecting band 5 and the top plate connecting band 6, the prefabricated NC top plate units 1 between the sections are connected by adopting the UHPC cast-in-situ top plate connecting band 6, and the NC prefabricated bottom plate units 2 are connected by adopting the UHPC cast-in-situ bottom plate connecting band 5. The top plate connecting belt 6 and the bottom plate connecting belt 5 are formed by casting UHPC at joints of the prefabricated NC bottom plate 21 and the prefabricated NC top plate 11 after assembly.
In this embodiment, longitudinal prestressed steel beam corrugated pipes are respectively disposed in the NC prefabricated top plate 11 and the prefabricated NC bottom plate 21, and the prestressed steel beams penetrate through the longitudinal prestressed steel beam corrugated pipes and are anchored by the steel beam anchors 14 in a tensioning manner, and referring to fig. 8, 9 and 10, longitudinal prestressed steel beam corrugated pipes are respectively disposed in the prefabricated NC top plate block unit 1 and the prefabricated NC bottom plate block unit 2 in the NC-UHPC combined assembly type prestressed concrete box girder, and are connected by the longitudinal prestressed steel beams, and the longitudinal prestressed steel beam anchors 14 are disposed at the end portions of the segments to perform tensioning anchoring and provide prestress so as to offset tensile stresses generated by dead weights, vehicle loads and the like on the cross section of the girder body.
In the embodiment, cantilever top plate reinforcing longitudinal beams 102 are arranged at the cantilever positions of NC prefabricated top plates 11, UHPC prefabricated diagonal braces 10 are arranged at the intersection positions of the cantilever top plate reinforcing longitudinal beams 102 and top plate reinforcing transverse ribs 12, the UHPC prefabricated diagonal braces 10 are connected with the top plate reinforcing transverse ribs 12 and the prefabricated NC bottom plates 21 through prefabricated diagonal brace UHPC cast-in-situ connection joints 101, if the bridge deck width needs to be increased, the transverse bridge directional cantilever length of the prefabricated NC top plates 11 is increased appropriately on the premise that the number of the boxes is not increased or the width of the boxes is changed, and UHPC prefabricated diagonal braces 10 are arranged between the NC prefabricated top plates 11 and the prefabricated NC bottom plates 21 so as to assist the stress of cantilever parts of the NC prefabricated top plates.
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, temporary brackets are erected on two sides of a pier, and NC prefabricated bottom plate block units (2) formed by prefabricated NC bottom plates (21) are installed on the top sections of the piers;
B, installing a prefabricated UHPC solid web plate unit (4) formed by a prefabricated UHPC variable-section straight web plate (31) at the pier top section, installing a prefabricated NC bottom plate (21) and a prefabricated UHPC solid web shear key penetrating through a steel bar (8) at the pier top section, and pouring a UHPC cast-in-situ web connecting joint (7);
c, installing a prefabricated NC top plate block unit (1) formed by a pier top section prefabricated NC top plate (11), installing a NC prefabricated top plate and a pier top section UHPC prefabricated solid web shear key penetrating through a reinforcing steel bar, and pouring a UHPC cast-in-situ connection joint;
D, installing a prefabricated NC bottom plate block unit (2) formed by prefabricating an NC bottom plate (21) by adopting a temporary hanging bracket through a conventional beam Duan You, and temporarily fixing;
Step e, installing a prefabricated UHPC web plate unit (3) formed by prefabricating a UHPC variable-section straight web plate (31) by a conventional beam Duan You, installing a high-strength bolt connecting joint splice plate (37) connected with the completed section, screwing and fixing a high-strength bolt (38), installing a conventional beam section NC prefabricated bottom plate and a UHPC hourglass-shaped prefabricated web plate shear key penetrating steel bar (9), pouring a UHPC cast-in-situ connecting joint, and pouring a UHPC cast-in-situ prefabricated web plate reinforcing vertical rib connecting joint (7);
F, installing a conventional beam section NC prefabricated roof plate block unit (1) by adopting a temporary hanging bracket and temporarily fixing, installing a conventional beam Duan Yuzhi NC roof plate (11) and a UHPC prefabricated web shear key penetrating through a steel bar (8), pouring a UHPC cast-in-situ connection joint, and pouring a UHPC web reinforced vertical rib connection joint (7);
step g, pouring a UHPC cast-in-situ bottom plate connecting belt (5) between the installed sections and a UHPC cast-in-situ top plate connecting belt (6), installing a longitudinal prestressed steel beam anchor (14) and tensioning a top plate longitudinal prestressed steel beam (13) after the UHPC cast-in-situ belt is cured to reach the design strength, and then performing prestressed grouting and anchor sealing;
Step h, repeating the step d-step g by adopting a symmetrical cantilever assembly method, installing a conventional precast beam Duan Zhi full-bridge closure section by section, and tensioning a top plate and a bottom plate prestress closure steel beam;
And i, removing the temporary brackets on the two sides of the bridge pier and the temporary bracket of the side span to finish the girder construction.
Referring to fig. 6-7 and 9-12, the above-mentioned steel pipes embedded in the NC precast top plate shear key 16, NC precast bottom plate shear key embedded steel pipes 25 and precast web shear key embedded steel pipes 34 are used as the shear pins of the shear keys and the inner templates of the circular openings of the shear keys.
The cast-in-situ UHPC filling gaps among the NC prefabricated top plate block unit 1, the NC prefabricated top plate block unit 2 and the UHPC hourglass-shaped prefabricated web plate block unit 3 or the pier top section UHPC prefabricated solid web plate block unit 4 adopts short steel fibers with the length not more than 15mm to ensure the fluidity, and the gaps are filled and filled by UHPC through the pre-embedded steel pipes 16 of the NC prefabricated top plate shear key and the pre-embedded steel pipes 25 of the NC prefabricated bottom plate shear key.
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 are prefabricated in advance in factories and installed on site, the solidification time of the UHPC cast-in-situ wet joint belt 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 mode by adopting a shaping template, and the bridge flat curve, the vertical curve, the pre-arch, the bridge deck ultra-high transverse slope gradual change and the like can be adjusted and adapted by utilizing the UHPC cast-in-situ wet joint belt among the sections.
(3) Reducing the amount of engineering of the substructure and foundation. Because the web adopts UHPC, the high-strength mechanical property of the web is fully utilized, the thickness of the plate is thinned, and meanwhile, the structural dead weight is obviously reduced by perforating and hollowing the web, and the bridge pier cross section area of the lower structure and the quantity of basic engineering are effectively reduced.
(4) The traditional precast box girder segment has large volume and heavy weight, the precast box girder segment is integrated into zero, the precast box girder segment is disassembled into the NC top plate, the NC bottom plate and the UHPC web plate which are precast separately, an inner die and a supporting system of the precast box girder of the precast segment are omitted, the weight reduction and the miniaturization of precast components are realized, overrun transportation is avoided, and the on-site hoisting weight is effectively reduced.
(5) The UHPC material is used for the cast-in-situ joint for connecting the node components, the material consumption is small, the structure is simple, the construction period is shortened, the strength of the connecting section is enhanced, and the defect of weak stress of the connecting node of the prefabricated component is overcome. The wet joint connection is no longer a weak link of the prefabricated assembly structure.
(6) Energy saving, emission reduction, low carbon and environmental protection. Since the number of materials used for the upper and lower structures is greatly reduced, the CO 2 emissions during construction are reduced compared with NC box girder bridges of the same scale.
(7) And the maintenance-free performance is improved. The UHPC prefabricated perforated web plate is a high-quality member manufactured in a factory, and the UHPC is made of high-strength steel fibers, so that the UHPC prefabricated perforated web plate has high tensile strength and ductility, and no steel bars are required to be arranged, so that the corrosion of the steel bars caused by salt damage and concrete carbonization cannot occur, the UHPC prefabricated perforated web plate has high durability, and the maintenance-free performance of the structure is further improved.
(8) The hollowed-out holes on the web plate can provide good lighting, so that the light of the inner space of the main beam is bright, and the inspection and the management and the protection are convenient.
(9) The hollowed-out holes on the web plate can ensure good ventilation effect inside and outside the box girder, and effectively reduce adverse effect of temperature gradient secondary stress generated by temperature difference inside and outside the box girder on the box girder structure.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and 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 and equivalents may be made thereto without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered by the scope of the claims of the present invention.
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| JP5941767B2 (en) * | 2012-06-26 | 2016-06-29 | 三井住友建設株式会社 | Construction method of box girder bridge |
| KR101482522B1 (en) * | 2013-04-03 | 2015-01-30 | 주식회사 장헌산업 | Nodular Box Girder, and Nodular Box Girder Bridge and Constructing Method thereof |
| CN106381814B (en) * | 2016-11-21 | 2018-07-06 | 宁波交通工程建设集团有限公司 | Roll over shape steel web continuous box girder jenny mould bases cantilever structure and its construction |
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