WO2023137999A1

WO2023137999A1 - Main beam unit having uhpc shuttering structure, main beam structure, and construction method therefor

Info

Publication number: WO2023137999A1
Application number: PCT/CN2022/103536
Authority: WO
Inventors: 邵旭东; 应李溶君; 赵旭东
Original assignee: 湖南大学
Priority date: 2022-01-18
Filing date: 2022-07-04
Publication date: 2023-07-27
Also published as: CN114319065B; CN114319065A

Abstract

A main beam unit having an ultra-high performance concrete (UHPC) shuttering structure, the main beam unit comprising a main beam body (100). At least one longitudinal bridge end portion of the main beam body (100) is provided with a UHPC shuttering structure, and the UHPC shuttering structure comprises a vertical plate (8) located at an end portion of the main beam body (100). A longitudinal bridge epitaxial plate (3) is extendably arranged on a side edge and bottom edge of the vertical plate (8) in a direction away from the main beam body (100). Further provided are a main beam structure and a construction method for the main beam structure. An end portion of the main beam body is provided with a UHPC shuttering structure, which provides a ready-made formwork for the construction of a cast-in-place joints at the top of a pier, so that a formwork for the construction of joints does not need to be erected at a construction site, and UHPC can be cast directly at the joints, which is convenient for construction and is beneficial for the rapid construction of a bridge structure.

Description

A main beam unit with UHPC formwork structure, main beam structure and construction method thereof

technical field

The invention belongs to the field of bridges, and in particular relates to a main beam unit, a main beam structure and a construction method thereof.

Background technique

Small and medium-span prefabricated bridges play a pivotal role in my country's bridge construction. According to statistics from the Ministry of Transport, by the end of 2020, there were approximately 786,400 small and medium-span bridges across the country, accounting for 86.2% of all highway bridges, an increase of 34,500 compared with 2019. In the face of such a large stock market and incremental market, promoting the development of prefabricated small and medium-span bridges is of great significance for changing bridge construction methods, improving bridge engineering quality, and shortening bridge construction periods.

At present, there are three main types of prefabricated bridges: prefabricated concrete beams, prefabricated steel-concrete composite beams, and prefabricated steel box girders, all of which have problems of varying degrees. Generally speaking, prefabricated bridges mainly have pain points such as low strength, heavy weight, inconvenient transportation and installation, and large amount of on-site welding.

Ultra-High Performance Concrete (UHPC for short) is a new type of cement-based composite material formulated based on the theory of maximum compactness. The steel fiber in the matrix significantly improves the tensile properties and toughness of the material. The internal density of the material makes it have excellent mechanical properties and good durability. In the field of bridge construction, fully and reasonably applying UHPC materials to prefabricated bridges can reduce the self-weight of the bridge structure, improve the strength and durability of the bridge, shorten the construction period of the bridge, simplify the construction process of the bridge, and improve the industrialization level of the bridge. However, the above-mentioned problems at the joints of prefabricated bridges still exist, and it is urgent to research and develop a new type of main beam structure.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, and provide a main beam unit with UHPC formwork structure, main beam structure and construction method thereof with high joint bearing capacity and easy construction. In order to solve the problems of the technologies described above, the technical solution proposed by the present invention is:

A main beam unit with a UHPC formwork structure, comprising a main beam body, at least one longitudinal bridge end of the main beam body is provided with a UHPC formwork structure, and the UHPC formwork structure includes a vertical plate located at the end of the main beam body, and the side and bottom edge of the vertical plate extend in a direction away from the main beam body.

In the above-mentioned main beam unit with UHPC formwork structure, the vertical plate is arranged at the end of the main beam body, which is basically the same in height and width as the main beam body, and its shape matches the cross-sectional shape of the main beam body. The extending plate of the longitudinal bridge is formed by extending outward from the bottom and side edges of the vertical plate, more preferably formed by extending outward from the edge of the bottom and the side, the upper surface of the extending plate of the longitudinal bridge is preferably flush with the upper surface of the main girder body, and the overall shape of the extending plate of the longitudinal bridge can be U-like.

Among the above-mentioned main beam units with UHPC formwork structure, when multiple main beam units form a main beam structure, the two ends of the longitudinal bridge of the main beam unit located in the middle of the main beam structure are provided with UHPC formwork structures to facilitate pouring joints, and the main beam units located at the end of the main beam structure can only be provided with UHPC formwork structures at one end of the longitudinal bridge.

In the above-mentioned main beam unit with UHPC formwork structure, preferably, the riser is provided with a plurality of tooth keys (UHPC) on the surface away from the main beam body. More preferably, the tooth key is a trapezoidal tooth key, the trapezoidal tooth key includes an upper top surface and a lower bottom surface, the area of the upper top surface is larger than the area of the lower bottom surface, the lower bottom surface is close to the vertical plate, and the upper top surface is away from the vertical plate; the distance between adjacent trapezoidal tooth keys in the height direction is 15-25cm (referring to the net distance between the lower bottom surfaces of two adjacent trapezoidal tooth keys), the inclination angle of the side of the trapezoidal tooth key is 45-75°, and the trapezoidal tooth key protrudes from the vertical plate. The thickness of the plate surface is 5-10cm (that is, the height of the trapezoidal side of the trapezoidal tooth key), the number of rows of the trapezoidal tooth key is 3-5 rows, and the number of columns of the trapezoidal tooth key is 2-5. In the present invention, a UHPC tooth key prefabricated together with the vertical plate is arranged at the end of the main girder body, which effectively enhances the crack resistance of the pier top joint, and at the same time enhances the vertical shear resistance of the interface between the prefabricated main beam unit and the post-cast UHPC joint, and improves the force transmission performance of the prefabricated body and the cast-in-place body in the longitudinal bridge direction; the optimal arrangement of the tooth key near the top can better exert its shear resistance. durability. By controlling the shape of the tooth key to be trapezoidal, the contact area between the ultra-high performance concrete wet joint and the prefabricated body can be increased, and the mechanical interlocking effect thereof can be enhanced, thereby improving the bearing capacity of the joint. The specific number and size of the above-mentioned UHPC tooth keys may be determined according to the actual situation.

In the above main beam unit with UHPC formwork structure, the main beam body includes a steel-UHPC composite beam or a UHPC single beam.

In the above-mentioned main beam unit with UHPC formwork structure, the UHPC single beam is a π-shaped beam; the steel-UHPC composite beam includes steel beams and UHPC beams; the steel beams include hot-rolled section steel, welded I-beam, cold-formed steel, etc., and the UHPC beam includes T-shaped beams, π-shaped beams, I-shaped beams, or rectangular flat-shaped beams, etc.; As for the connecting piece, the ends of the steel beams are embedded in the risers. In the present invention, compared with the welded I-beam, the hot-rolled section steel does not need to be welded, thereby reducing the residual stress and simplifying the construction process, thereby achieving the effects of reducing cost and shortening the construction period. On the whole, compared with ordinary steel-concrete composite beams, the above-mentioned steel-UHPC composite beams can significantly reduce the girder height and self-weight of the main girder, making the structure lighter; zero welding can be realized on site, which makes the structural construction faster; it can reduce the cost and life cycle cost, making the structure more competitive in the market. More preferably, the steel beam is a hot-rolled section steel, and the UHPC beam is a π-shaped beam. By setting multiple shear connectors on the upper flange of the steel beam, the steel beam and the UHPC beam can be fixed to form a whole, and by setting shear connectors on the upper flange, web and lower flange, it is convenient for the vertical plate to be fixed with the steel beam to form a whole.

In the above-mentioned main girder unit with UHPC formwork structure, preferably, the π-shaped beam includes a top plate, a pair of arc-shaped webs and a pair of bottom plates, the bottom plate is arranged at the bottom of the arc-shaped web, and a pair of the arc-shaped webs are symmetrically arranged at the bottom of the top plate along the longitudinal bridge to the center line; . Compared with the general UHPC beam, the π-shaped beam has no chamfer, which can reduce the local stress concentration phenomenon; the lines are smooth, and the transition between the line segments is smooth, making the cross-sectional shape more beautiful.

In the above-mentioned main beam unit with UHPC formwork structure, the shear connector can be a stud connector, an inverted T-shaped connector, a perforated steel plate connector or other new shear connectors. Taking the stud connector as an example, the diameter of the stud connector can be controlled to be 10-30 mm, and the height is 30-150 mm. The specific specifications depend on the size of the steel beam and the UHPC beam.

In the above-mentioned main beam unit with UHPC formwork structure, preferably, the top of at least one longitudinal bridge end of the main beam body is provided with a roughened half notch (two adjacent half notches are spliced to form a notch, which is used for cast-in-place concrete). By setting a half notch of a specific length, the weak interface can be set in the low tensile stress area, and the half notch needs to be chiseled to improve the interface crack resistance of the new and old concrete.

In the above-mentioned main beam unit with UHPC formwork structure, preferably, the half notch is provided with an extension steel bar extending outward from the inside of the main beam body, and the beam body below the half notch is also provided with an extension steel bar extending outward, and the extension degree of the extension steel bar is not less than 10 times the diameter of the extension steel bar. The length of the extension steel bar should be adapted to the size of the joint. By setting the extension steel bar, it is beneficial to improve the mechanical properties of the joint.

In the above-mentioned main beam unit with UHPC formwork structure, preferably, the vertical plate, the longitudinal bridge extension plate and the UHPC part in the main beam body are integrally prefabricated, and the upper surface of the longitudinal bridge extension plate is kept flush with the upper surface of the main beam body, the thickness of the longitudinal bridge extension plate is 5-10 cm, and the length of the longitudinal bridge is 10-50 cm. In the present invention, the vertical plate and the UHPC part of the main beam body are prefabricated integrally. The two can be regarded as an inseparable whole. After the half-notch is set, because the half-notch horizontal bridge retains side walls on both sides, it can be considered that the side wall retained at the end of the main beam body is also a component of the vertical plate. The side wall also extends to the seam to form the longitudinal bridge. is the longitudinal bridge to the epitaxial plate), and the two are seamlessly connected.

In the present invention, if the thickness of the extension board is less than 5cm, the ability to resist external effects is weak, and it may be damaged due to collision during the construction process. In addition, if the thickness of the outer plate is small, it is not conducive to pouring, and the quality of the shell is difficult to guarantee; As a force requirement for the mold shell, it can be applied to the beam bridges with common spans, and it can also ensure the quality of pouring and have good economy. The longitudinal bridge length of the extension slab is based on the following considerations: after the splicing of the adjacent formwork structures in the longitudinal direction, the space for the cast-in-place pier top is formed, so the longitudinal length needs to meet the requirements of the joint width of the pier top. For common medium-span beam bridges (20-60m), the simply supported variable continuous structure system is adopted, and the length of the cast-in-place joint at the top of the pier is basically in the range of 20-100cm. Suitable for common medium span girder bridges.

As a general technical idea, the present invention also provides a main girder structure, which is mainly formed by connecting a plurality of the above-mentioned main girder units in the longitudinal bridge direction, and the longitudinal bridges are closely connected to the longitudinal bridges of the adjacent main girder units to the extension plates to form a closed sealing area on the side and bottom for the cast-in-place joint concrete. In the present invention, the cross-sectional shape of the vertical plate can be adapted to the cross-sectional form of the main girder body, and a pair of adjacent longitudinal bridge-facing extension plates can be spliced at the pier top joint by filling water-stop rubber strips, etc., and the sealed area formed after splicing can be directly used as a formwork for the pier top cast-in-place joint, saving the time for setting up the formwork on site, and at the same time simplifying the on-site construction process to achieve the goal of rapid bridge construction.

As a general technical idea, the present invention also provides a construction method for the above-mentioned main beam structure, comprising the following steps:

S1: Install the main beam body and the formwork of the UHPC formwork structure in the prefabrication yard, and then pour UHPC to form the main beam unit with the UHPC formwork structure;

S2: Transport the main girder unit with UHPC formwork structure to the erection position with a beam transport vehicle, erect it with hoisting equipment, and complete the tight connection between the longitudinal bridge of the adjacent main girder unit and the extension plate to form a sealed area;

S3: UHPC is cast in-situ and cured in the above-mentioned sealed area, and the construction is completed.

Compared with the prior art, the present invention has the advantages of:

1. In the present invention, a UHPC formwork structure is arranged at the end of the main girder body, which provides a ready-made formwork for the cast-in-place joint structure of the pier top. It is not necessary to set up a formwork for the joint structure at the construction site, and the ultra-high performance concrete can be directly cast in-situ at the joint, which is convenient for construction and is conducive to the rapid construction of the bridge structure. At the same time, the use of UHPC formwork structure is conducive to improving the quality of the joints and improving the mechanical strength of the joints.

2. The main girder unit and the main girder structure of the present invention are simple in structure, clear in force, greatly simplify on-site construction procedures, have a wide range of applications, and have broad application prospects.

3. The construction method of the present invention is simple, and most of the products are prefabricated in the factory, which can reduce the workload of on-site casting and maintenance, and can greatly speed up the construction progress.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings used in the description of the embodiments or prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other accompanying drawings can also be obtained based on these drawings without creative work.

Fig. 1 is a three-dimensional structural schematic diagram of a main beam unit (Type I) with a UHPC formwork structure in Example 1.

Fig. 2 is a schematic side view of the main beam unit (Type I) with UHPC formwork structure in Embodiment 1.

FIG. 3 is a schematic structural diagram of the tooth key in Embodiment 1. FIG.

FIG. 4 is a schematic structural view of the main beam unit (Type I) in Embodiment 1.

Fig. 5 is a schematic cross-sectional view of the main girder unit (Type I) along the transverse bridge direction in Embodiment 1 (the internal reinforcement of the main girder is not shown in the figure).

Fig. 6 is a structural schematic diagram of steel beams welded with shear connectors in the main beam unit (type I) in Example 1.

Fig. 7 is a three-dimensional structural schematic diagram of the main beam unit (type I) with UHPC formwork structure spliced into the main beam structure in Example 1.

Fig. 8 is a three-dimensional structural schematic diagram of the main beam unit (Type II) with UHPC formwork structure in Example 2.

Fig. 9 is a schematic side view of the main beam unit (Type II) with UHPC formwork structure in Embodiment 2.

Fig. 10 is a schematic structural view of the main beam unit (Type II) in Embodiment 2.

Fig. 11 is a schematic cross-sectional view of the main girder unit (Type II) along the transverse bridge direction in Embodiment 2 (the internal reinforcement of the main girder is not shown in the figure).

Fig. 12 is a structural schematic diagram of steel beams welded with shear connectors in the main beam unit (Type II) in Example 2.

Fig. 13 is a three-dimensional schematic diagram of the main beam unit (Type III) with UHPC formwork structure in Example 3.

Fig. 14 is a schematic side view of the main beam unit (Type III) with UHPC formwork structure in Embodiment 3.

Fig. 15 is a schematic structural view of the main beam unit (Type III) in Embodiment 3.

Fig. 16 is a schematic cross-sectional view of the main beam unit (Type III) in Embodiment 3 (the internal reinforcement of the main beam is not shown in the figure).

illustration:

1. Hot-rolled section steel; 2. π-beam; 21. Top plate; 22. Arc-shaped web; 23. Bottom plate; 3. Extended plate towards longitudinal bridge; 4. Tooth key; 5. Half notch; 6. Extended steel bar; 7. Shear connector;

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more fully and in detail below in conjunction with the accompanying drawings and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meanings as commonly understood by those skilled in the art. The terminology used herein is only for the purpose of describing specific embodiments, and is not intended to limit the protection scope of the present invention.

Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

Example 1:

As shown in FIGS. 1-6 , the main girder unit (type I) with UHPC formwork structure of this embodiment includes a main girder body 100. At least one longitudinal bridge end of the main girder body 100 is provided with a UHPC formwork structure.

In this embodiment, the riser 8 is provided with a plurality of tooth keys 4 on the surface away from the main girder body 100 . Specifically, the trapezoidal tooth key comprises an upper top surface and a lower bottom surface, the area of the upper top surface is greater than the area of the lower bottom surface, the lower bottom surface is close to the vertical plate, and the upper top surface is away from the vertical plate; the distance between adjacent trapezoidal tooth keys in the height direction is 15-25cm (the above-mentioned ranges are all available), the inclination angle of the side of the trapezoidal tooth key is 45-75 ° (the above-mentioned ranges are all available, as shown in Figure 3 73 °), and the thickness of the trapezoidal tooth keys protruding from the surface of the vertical plate is 5-10cm (the above-mentioned ranges are all available). The number of rows of the tooth key is 3-5 (the above range is acceptable), and the number of columns of the trapezoidal tooth key is 2-5 (the above range is acceptable). In this embodiment, the number of columns, rows, distances and inclinations of the tooth keys 4 can be determined according to actual needs.

In this embodiment, the main girder body 100 is a steel-UHPC composite beam, and the steel-UHPC composite beam includes a steel beam and a UHPC beam. The steel beam is a commercially available hot-rolled steel 1, and the UHPC beam is a π-shaped beam 2; the upper flange of the hot-rolled steel 1 is provided with multiple shear connectors 7; In this embodiment, the above-mentioned shear connector 7 can be a stud, the diameter of the stud can be 10-30mm, and the height can be 30-150mm, and the specific specification depends on the size of the steel beam and the UHPC beam.

In this embodiment, the π-shaped beam 2 includes a top plate 21, a pair of arc-shaped webs 22 and a pair of bottom plates 23. The bottom plate 23 is arranged at the bottom of the arc-shaped web 22, and a pair of arc-shaped webs 22 are symmetrically arranged at the bottom of the top plate 21 along the longitudinal bridge to the center line; Arc transition.

In this embodiment, the top of at least one longitudinal bridge end of the main beam body 100 is provided with a half-notch 5 that has been chiseled, and side walls are reserved on both sides of the horizontal bridge of the half-notch 5 , and the longitudinal length of the half-notch 5 is L/6-L/10 (the above-mentioned range is acceptable), wherein L refers to the length of the main beam body 100.

In this embodiment, the half notch 5 is provided with an extended steel bar 6 extending outward from the inside of the main beam body 100, and the beam body below the half notch 5 is also provided with an extended steel bar 6 extending outward. The extension of the extended steel bar 6 is not less than 10 times the diameter of the extended steel bar 6.

In this embodiment, the riser 8, the longitudinal bridge extension plate 3 and the UHPC part in the main beam body 100 are integrally prefabricated, and the upper surface of the longitudinal bridge extension plate 3 is kept flush with the upper surface of the main beam body 100, the thickness of the longitudinal bridge extension plate 3 is 5-10 cm (the above range is acceptable), and the longitudinal bridge length is 10-50 cm (the above range is acceptable).

As shown in Figure 7, the main girder structure of this embodiment is mainly composed of a plurality of the above-mentioned main girder units connected longitudinally and bridgewise, and the longitudinal bridges are closely connected to the longitudinal bridges of adjacent main girder units to the extension plates 3 to form a sealed area with closed sides and bottoms for cast-in-place joint concrete.

This embodiment also provides a construction method for the above-mentioned main beam structure, comprising the following steps:

S1: install the main beam body 100 and the formwork of the UHPC formwork structure in the prefabrication yard, and then pour UHPC to form the main beam unit with the UHPC formwork structure;

S2: Transport the main girder unit with UHPC formwork structure to the erection position with a beam transport vehicle, erect it with hoisting equipment, and complete the close connection of the longitudinal bridge of the adjacent main girder unit to the extension plate 3 to form a sealed area;

Example 2:

As shown in FIGS. 8-12 , the main girder unit (Type II) with UHPC formwork structure of this embodiment includes a main girder body 100, at least one longitudinal bridge end of the main girder body 100 is provided with a UHPC formwork structure, and the UHPC formwork structure includes a riser 8 located at the end of the main girder body 100, and the side and bottom edge of the riser 8 extend in a direction away from the main girder body 100.

In this embodiment, the riser 8 is provided with a plurality of tooth keys 4 on the surface away from the main girder body 100 , and its specific arrangement can be the same as that of the first embodiment.

In this embodiment, the main girder body 100 is a steel-UHPC composite beam. The steel-UHPC composite beam includes a steel beam and a UHPC beam. The steel beam is a welded I-beam 10 , and the UHPC beam is a rectangular flat beam 9 ; multiple shear connectors 7 are provided on the upper flange of the welded I-beam 10 , and multiple shear connectors 7 are also provided at the ends of the welded I-beam 10 . In this embodiment, the above-mentioned shear connector 7 can be a stud, the diameter of the stud can be 10-30mm, and the height can be 30-150mm, and the specific specification depends on the size of the steel beam and the UHPC beam.

Other structures of the main beam unit in this embodiment can be the same as in Embodiment 1.

The main girder structure of this embodiment is mainly composed of a plurality of above-mentioned main girder units connected in the longitudinal bridge direction, and the longitudinal bridges are closely connected to the longitudinal bridges of adjacent main girder units to the extension plates 3 to form a sealed area with closed sides and bottoms for cast-in-place joint concrete.

The construction method of the main beam structure of this embodiment can be the same as that of Embodiment 1.

Example 3:

As shown in FIGS. 13-16 , the main girder unit (Type III) with UHPC formwork structure of this embodiment includes a main girder body 100, at least one longitudinal bridge end of the main girder body 100 is provided with a UHPC formwork structure, and the UHPC formwork structure includes a riser 8 located at the end of the main girder body 100, and the side and bottom edge of the riser 8 extend in a direction away from the main girder body 100.

In this embodiment, the main beam body 100 is a UHPC single beam, and the UHPC single beam is a π-shaped beam 2 . Specifically, the π-shaped beam 2 includes a top plate 21, a pair of arc-shaped webs 22 and a pair of bottom plates 23. The bottom plate 23 is arranged at the bottom of the arc-shaped web 22, and a pair of arc-shaped webs 22 are symmetrically arranged at the bottom of the top plate 21 along the longitudinal bridge to the center line; transition.

Claims

A main beam unit with a UHPC formwork structure, characterized in that it comprises a main beam body (100), at least one longitudinal bridge end of the main beam body (100) is provided with a UHPC formwork structure, and the UHPC formwork structure includes a riser (8) located at the end of the main beam body (100), and the side and bottom edge of the riser (8) extend in a direction away from the main beam body (100) and are provided with a longitudinal bridge outward extension plate (3).
The main beam unit according to claim 1, characterized in that, the riser (8) is provided with a plurality of teeth keys (4) on a surface away from the main beam body (100).
The main beam unit according to claim 2, characterized in that the tooth key (4) is a trapezoidal tooth key, the trapezoidal tooth key includes an upper top surface and a lower bottom surface, the area of the upper top surface is larger than the area of the lower bottom surface, the lower bottom surface is close to the vertical plate (8), and the upper top surface is far away from the vertical plate (8); the distance between the adjacent trapezoidal tooth keys in the height direction is 15-25cm, the inclination angle of the side of the trapezoidal tooth key is 45-75°, and the trapezoidal tooth key protrudes The thickness of the surface of the riser (8) is 5-10 cm, the number of rows of the trapezoidal tooth keys is 3-5, and the number of columns of the trapezoidal tooth keys is 2-5.
The main beam unit according to any one of claims 1-3, wherein the main beam body (100) comprises a steel-UHPC composite beam or a UHPC single beam, the steel-UHPC composite beam comprises steel beams and UHPC beams, the steel beam comprises hot-rolled steel (1) or welded I-beam (10), and the UHPC beam comprises T-beams, π-beams (2), I-beams or rectangular flat beams (9); the upper flange of the steel beam is provided with a plurality of shears The force connector (7), the web and the lower flange of the steel beam are also provided with a plurality of shear connectors (7) at the end, and the end of the steel beam is embedded in the vertical plate (8); the UHPC single beam is a π-shaped beam (2).
The main girder unit according to claim 4, wherein the π-shaped beam (2) comprises a top plate (21), a pair of arc-shaped webs (22) and a pair of bottom plates (23), the base plate (23) is arranged at the bottom of the arc-shaped web (22), and a pair of the arc-shaped webs (22) are symmetrically arranged at the bottom of the top plate (21) along the centerline of the longitudinal bridge; 22) The two sides of the cross-section of the transverse bridge are arc-shaped, and the contact transition between the two sides of the arc-shaped web (22) and the top plate (21) or the bottom plate (23) is arc-shaped transition.
According to the main beam unit according to any one of claims 1-3, it is characterized in that, the top of at least one longitudinal bridge end of the main beam body (100) is provided with a half-notch (5) processed by chiseling, side walls are reserved on both sides of the transverse bridge of the half-notch (5), and the longitudinal bridge length of the half-notch (5) is L/6-L/10, wherein L refers to the length of the main beam body (100).
The main beam unit according to claim 6, characterized in that, the half notch (5) is provided with an extended steel bar (6) extending outward from the inside of the main beam body (100), and the beam body below the half notch (5) is also provided with an extended steel bar (6) extending outward, and the extension of the extended steel bar (6) is not less than 10 times the diameter of the extended steel bar (6).
The main beam unit according to any one of claims 1-3, characterized in that, the vertical plate (8), the longitudinal bridge extension plate (3) and the UHPC part in the main beam body (100) are integrally prefabricated, and the upper surface of the longitudinal bridge extension plate (3) is flush with the upper surface of the main beam body (100), the thickness of the longitudinal bridge extension plate (3) is 5-10 cm, and the length of the longitudinal bridge direction is 10-50 cm.
A main girder structure, characterized in that it is mainly composed of the longitudinal bridges of the main girder units described in any one of claims 1-8, and the longitudinal bridges are closely connected to the longitudinal bridges of the adjacent main girder units to the extension plates (3) to form side and bottom sealed sealing areas for cast-in-place joint concrete.
A construction method for a main girder structure as claimed in claim 9, comprising the following steps:

S1: install the main beam body (100) and the formwork of the UHPC formwork structure in the prefabrication yard, and then pour UHPC to form the main beam unit with the UHPC formwork structure;

S2: Transport the main girder unit with UHPC formwork structure to the erection position with a beam transport vehicle, erect it with hoisting equipment, and complete the close connection of the longitudinal bridge of the adjacent main girder unit to the extension plate (3) to form a sealed area;

S3: UHPC is cast in-situ and cured in the above-mentioned sealed area, and the construction is completed.