Railway hybrid beam with rear-mounted U-shaped cover steel-concrete combined section structure and its construction method

Abstract

The present invention discloses a railway hybrid beam with a rear-mounted U-shaped cover plate and a steel-concrete combined section structure and a construction method thereof. The structure includes a steel structure portion with a U-shaped rear-mounted cover plate, a steel skeleton formed by longitudinal, transverse and vertical ordinary steel bars and PBL steel bars in the concrete, concrete and prestressed steel bars. During construction, concrete is poured from the opening position of the open steel top plate in conjunction with the concrete pouring hole and vibrated to make it dense; before the concrete initially sets, the U-shaped cover plate pre-welded at one end of the horse plate is covered on the concrete, and after the concrete strength reaches the standard, the open steel top plate and the U-shaped cover plate are welded to form a whole; the present invention solves the problems of traditional steel-concrete combined section structures due to complex structure, many longitudinal and transverse partitions of the top and bottom plates, dense internal steel bars, difficulty in concrete pouring, loose vibration, concrete voiding, etc. The present invention improves the quality of concrete pouring, and the cover steel plate effectively improves the connection between the steel and concrete in the combined section, thereby improving force transmission and durability.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge engineering design and construction, and in particular relates to a railway hybrid beam with a rear-mounted U-shaped cover plate and a steel-concrete combined section structure and a construction method thereof. Background Art

[0002] A hybrid box girder refers to a box girder bridge in which the middle span is mostly or entirely steel, and the sides are partially or entirely concrete. Due to its strong spanning capacity and good load-bearing properties on the balanced side main span, it is increasingly being used and developed in long-span railway bridges. The steel-concrete junction must ensure both its own load-bearing requirements and a reasonable transition in stiffness, which is one of the key points and difficulties in hybrid beam design and construction. However, due to its complex structure, the numerous longitudinal and transverse partitions on the top and bottom plates, and the dense interior of ordinary steel bars, the steel beams only have a few holes at the top for concrete entry. This leads to defects such as incomplete pouring, loose vibration, and voids in the concrete junction. Consequently, during operation, the steel-concrete junction suffers from defects such as steel-concrete separation and water leakage, seriously affecting the force transmission and durability of the junction and even endangering the safety of the bridge. At the same time, the application of hybrid box girders in railway bridges is relatively late, and there is little data on the stress, force transmission, and deformation characteristics of the steel-concrete joint section under heavy loads on relevant railways. In order to solve the problems of difficult construction of the steel-concrete joint section and subsequent concrete pouring, and to ensure the safe operation of the railway, it is very urgent to develop a railway hybrid box girder steel-concrete joint section connection structure that is convenient for concrete pouring. Summary of the Invention

[0003] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and provide a railway hybrid beam with a rear-mounted U-shaped cover plate steel-concrete combined section structure and its construction method, so as to solve the problems of difficulty in concrete pouring and separation of steel and concrete in the construction of existing hybrid box beams.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] In a first aspect, a railway hybrid beam with a rear-mounted U-shaped cover plate and a steel-concrete combined section structure comprises an open steel top plate, a steel bottom plate, and a pressure plate; the two ends of the pressure plate are respectively welded to the inner sides of the open steel top plate and the steel bottom plate;

[0006] A middle web, a reinforcing web, and an edge web are provided on one side of the steel-concrete joint section, and multiple stiffening ribs are welded to the edge web. The upper and lower sides of the middle web, the reinforcing web, and the edge web are longitudinally fixed between the open steel top plate and the steel bottom plate. The open steel top plate or the steel bottom plate is vertically connected to the bottom edges of multiple short PBL perforated steel plates and multiple long PBL perforated steel plates.

[0007] The middle web, reinforcing web, side web, short PBL perforated steel plate and long PBL perforated steel plate are all connected to the bearing plate.

[0008] Furthermore, a plurality of U-shaped openings are provided on the open steel top plate, the opening width of the U-shaped opening is 300mm to 1200mm, the opening length is 600 to 1200mm, the arc radius in the U-shaped opening is 150mm to 600mm, and the spacing between two adjacent U-shaped openings is 300mm to 900mm.

[0009] Furthermore, the open steel top plate is provided with a concrete pouring hole near the pressure plate.

[0010] Furthermore, a plurality of short PBL perforated steel plates are fixed to the U-shaped opening bottom of the open steel top plate, and the plurality of short PBL perforated steel plates and the plurality of long PBL perforated steel plates are alternately arranged in sequence.

[0011] Furthermore, multiple circular holes with a diameter of 40 to 80 mm are opened on both the short PBL perforated steel plate and the long PBL perforated steel plate. PBL steel bars for strengthening the connection with concrete are passed through the circular holes. The PBL steel bars and the concrete surrounding them form PBL shear keys.

[0012] Furthermore, shear nails are welded on the open steel top plate, steel bottom plate and pressure plate, and the circular holes and ordinary steel bars are staggered with the shear nails and prestressed steel bar pipeline arrangement, so that the longitudinal ordinary steel bars, transverse ordinary steel bars, vertical ordinary steel bars in the concrete of the steel-concrete joint section and the PBL steel bars form a joint section concrete steel bar skeleton staggered with the steel top plate shear nail arrangement.

[0013] Furthermore, it also includes a U-shaped cover plate; shear nails are welded on the U-shaped cover plate, and multiple semicircular notches are opened at the end of the U-shaped cover plate.

[0014] Furthermore, the U-shaped cover plate is vertically welded to one end of multiple horse plates; before the concrete begins to set, the other ends of the multiple horse plates are placed on the open steel top plate 1 and weighted so that the U-shaped cover plate is flush with the open steel top plate, and the shear nails under the U-shaped cover plate are inserted into the unset concrete.

[0015] Furthermore, after the concrete strength reaches 90% or above the design strength, the open steel top plate and the U-shaped cover plate are welded, and cooling belts are arranged on both sides of the weld between the open steel top plate and the U-shaped cover plate to form a whole with the open steel top plate and the U-shaped cover plate.

[0016] In a second aspect, a construction method for a railway hybrid beam with a rear-mounted U-shaped cover plate steel-concrete combined section structure comprises the following steps:

[0017] S1. Prefabricate the open steel top plate, U-shaped cover plate, steel bottom plate, middle web plate, reinforced web plate, side web plate, shear studs, short PBL perforated steel plate, long PBL perforated steel plate, bearing plate, horse plate and stiffeners. After the open steel top plate is opened, remove the U-shaped cover plate and dig holes in the PBL plate at the same time.

[0018] S2. Weld the short PBL perforated steel plates and the long PBL perforated steel plates vertically to the open steel top plate, steel bottom plate and pressure plate according to the spacing, and weld the reinforcing webs, side webs, shear studs and stiffening ribs to complete the fabrication, transportation and erection of the combined steel structure.

[0019] S3. Pass the PBL steel bars through the holes and secure them, leaving a channel for the longitudinal prestressed steel bars; tie the longitudinal ordinary steel bars, transverse ordinary steel bars, vertical ordinary steel bars and PBL steel bars to form a concrete reinforcement skeleton in the combined section, with the reinforcement skeleton staggered with the shear studs of the open steel top plate;

[0020] S4. Weld shear studs on the U-shaped cover plate; punch a semicircular notch at the end of the U-shaped cover plate, and weld one end of multiple horse plates vertically to the U-shaped cover plate;

[0021] S5. Pour concrete at the opening of the open steel top plate and the concrete pouring hole and vibrate it. Before the concrete begins to set, place the other end of the horse plate on the open steel top plate and apply weight to make the U-shaped cover plate flush with the open steel top plate. Insert the shear nails under the U-shaped cover plate into the unset concrete.

[0022] S6. When the concrete strength reaches 90% or above the design strength, remove the horse plate and weld the open steel top plate and the U-shaped cover plate. Set cooling zones on both sides of the weld. Also weld the circular steel plate back to the concrete pouring hole to close the open steel top plate.

[0023] S7. Insert the longitudinal prestressed steel bars into the reserved channel, install anchors, gradually tension the prestressed reinforcement bars, and anchor them; after the tensioning of the prestressed reinforcement bars is completed, pour cement slurry into the reserved channel.

[0024] The railway hybrid beam with rear-mounted U-shaped cover plate steel-concrete combined section structure and the construction method thereof provided by the present invention have the following beneficial effects:

[0025] This invention builds on the conventional steel-concrete joint section top plate structure by combining web layout and the location of perforated PBL steel plates. The arrangement of conventional steel reinforcement in the joint section is optimized, and concrete is poured and vibrated from the openings in conjunction with the concrete pouring holes. This solves the problems of difficult, incomplete, and uneven concrete pouring caused by the complex structure of the steel-concrete joint section, the numerous longitudinal and transverse partitions in the top and bottom plates, and the dense internal reinforcement, thereby improving concrete pouring quality. The cover steel plate effectively enhances the connection between the steel and concrete sections in the joint section, improving force transmission and durability.

[0026] The present invention further reduces the possibility of extension of cracks at the steel-concrete interface by punching semicircular holes in the cover plate, thereby reducing the risk of separation of the steel-concrete interface.

[0027] The present invention covers the U-shaped cover plate on the concrete. After the concrete strength meets the requirements, the open steel top plate and the U-shaped cover plate are welded and cooled by a cooling belt to make them a whole. This can reduce the occurrence of water leakage, steel-concrete separation and other defects caused by rainwater seeping into the steel-concrete joint section from the steel nail plate during operation, improve the durability of the joint section, and reduce concrete damage caused by high temperature by cooling with a cooling belt during welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a cross-sectional structural diagram of the pressure plate of the present invention;

[0029] Figure 2 This is the structural diagram of the short PBL perforated steel plate of the steel-concrete combined section structure of the present invention;

[0030] Figure 3 This is the structural diagram of the long PBL perforated steel plate of the steel-concrete combined section structure of the present invention;

[0031] Figure 4 This is a plan view of the open top plate of the steel-concrete combined section structure of the present invention;

[0032] Figure 5 This is a plan view of the open top plate during welding of the steel-concrete combined section structure of the present invention;

[0033] Figure 6 This is a plan view of the top plate after the steel-concrete combined section structure welding is completed;

[0034] Figure 7 This is a structural diagram of the U-shaped cover plate of the steel-concrete combined section structure of the present invention;

[0035] Figure 8 This is a cross-sectional elevation view of a short PBL perforated steel plate of a steel-concrete combined section structure of the present invention;

[0036] Figure 9 This is a cross-sectional elevation view of the long PBL perforated steel plate of the steel-concrete combined section structure of the present invention;

[0037] Figure 10 This is the structural diagram of the steel-concrete combined section structure of the present invention;

[0038] Figure 11 This is a structural diagram of a U-shaped cover plate with a steel-concrete combined section structure of the present invention;

[0039] Among them, 1. Open steel top plate; 2. Pressure plate; 3. Steel bottom plate; 4. Side web; 5. Middle web; 6. Reinforced web; 7. Shear nails; 8. Short PBL perforated steel plate; 9. Long PBL perforated steel plate; 10. U-shaped cover plate; 11. Circular hole; 12. Prestressed steel bar; 13. Horse plate; 14. Stiffening rib; 15. Longitudinal ordinary steel bar; 16. PBL steel bar; 17. Transverse ordinary steel bar; 18. Vertical ordinary steel bar; 19. Concrete pouring hole; 20. Cooling zone. DETAILED DESCRIPTION

[0040] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0041] Example 1

[0042] refer to Figures 1 to 11 This embodiment provides a railway hybrid beam with a rear-mounted U-shaped cover plate and a steel-concrete joint section structure. This embodiment can improve the quality of concrete pouring, effectively enhance the durability of the steel-concrete joint section, and solve the problems of subsequent steel-concrete joint section separation, water leakage, and other defects. Specifically, it includes:

[0043] An open steel top plate 1, a steel bottom plate 3 and a pressure plate 2, with both ends of the pressure plate 2 welded to the inner sides of the open steel top plate 1 and the steel bottom plate 3 respectively;

[0044] A middle web 5, a reinforcing web 6 and a side web 4 are provided on one side of the steel-concrete joint section, and a plurality of stiffening ribs 14 are welded to the side web 4. The upper and lower sides of the middle web 5, the reinforcing web 6 and the side web 4 are longitudinally fixed between the open steel top plate 1 and the steel bottom plate 3.

[0045] The middle web 5, the reinforcing web 6, the side web 4, the short PBL perforated steel plate 8 and the long PBL perforated steel plate 9 are all connected to the pressure plate 2. The open steel top plate 1 is opened according to the web arrangement of the steel-concrete joint section, the positions of the short PBL perforated steel plate 8 and the long PBL perforated steel plate 9, and the U-shaped cover plate 10 is removed. A concrete pouring hole 19 is set on the open steel top plate 1 near the pressure plate 2.

[0046] This embodiment has an opening on the side of the steel top plate near the concrete beam, which is more conducive to the pouring and vibration of concrete than traditional steel top plates. The traditional steel-concrete joint section is blocked by the top and bottom plates, and the webs, numerous PBL plates, and ordinary steel bars make it difficult to pour concrete in the joint section and vibrate the concrete, affecting the compactness of the concrete. However, the open steel top plate 1 can achieve concrete pouring and vibration, making the concrete more compact. The open steel top plate 1 is opened according to the web layout and the position of the PBL perforated steel plate, reducing the impact of the steel top plate opening on the layout and stress of the steel-concrete joint section components. The U-shaped opening is less likely to cause stress concentration, making the internal stress generated within the steel plate uniform and reducing the impact on the stress of the steel plate.

[0047] The bottom edges of multiple short PBL perforated steel plates 8 and multiple long PBL perforated steel plates 9 are perpendicular to the open steel top plate 1 or the steel bottom plate 3; in this embodiment, 10 short PBL perforated steel plates 8 and 8 long PBL perforated steel plates 9 are preferably selected. Specifically, the 10 short PBL perforated steel plates 8 are fixed to the bottom of the U-shaped opening of the open steel top plate 1 and are alternately arranged with the 8 long PBL perforated steel plates 9 in sequence with a spacing of 600 mm; in this embodiment, the alternating arrangement of short PBL perforated steel plates 8 and long PBL perforated steel plates 9 can strengthen the steel-concrete connection, increase the force transmission path, and expand the force transmission area.

[0048] As a further preference of this embodiment, refer to Figure 2 and Figure 3 Circular holes 11 are provided on both the short PBL perforated steel plate 8 and the long PBL perforated steel plate 9. The circular holes 11 are provided uniformly, and the spacing between adjacent circular holes 11 is 15 cm. PBL steel bars 16 for strengthening the connection with concrete are connected to the circular holes 11. The PBL steel bars 16 together with the concrete wrapped therein form a PBL shear key.

[0049] In this embodiment, the circular holes 11 of the short PBL perforated steel plates 8 and the long PBL perforated steel plates 9 are arranged in the same manner, which facilitates the smooth passage of the PBL steel bars 16. After pouring concrete, the PBL steel bars 16 connect all the short PBL perforated steel plates 8 and the long PBL perforated steel plates 9 into one, so that the steel-concrete joint section has better integrity and also strengthens the connection tightness between the concrete and the steel member.

[0050] refer to Figure 4 In this embodiment, several U-shaped openings are formed in the open steel top plate 1, corresponding to the arrangement of the reinforcing webs 6 and side webs 4, as well as the long PBL perforated steel plates 9 and the short PBL perforated steel plates 8. The U-shaped openings have a width of 300 mm to 1200 mm, a length of 900 mm, an arc radius of 150 mm to 600 mm, and a spacing of 300 mm to 600 mm between adjacent U-shaped openings. The U-shaped openings in this embodiment are less likely to cause stress concentration, minimizing the impact on the stress on the steel plates.

[0051] refer to Figure 1 and Figure 6 Shear nails 7 are welded on the open steel top plate 1, the steel bottom plate 3 and the pressure plate 2. The distance between two adjacent shear nails 7 is usually 15 cm and can be adjusted between 10 and 20 cm. The shear nails 7 can limit interface slippage, prevent concrete from being lifted, make the joint section bear force smoothly, and increase the connection tightness between concrete and steel components.

[0052] refer to Figure 5 、 Figure 10 and Figure 11In this embodiment, the preferred size of the horse plate 13 is 200mm×15mm×75mm, and there is a semicircular notch at the bottom to facilitate welding construction.

[0053] Shear studs 7 are welded to the U-shaped cover plate 10. Their placement must match that of the shear studs 7 installed on the open steel top plate 1. Multiple semicircular notches are punched into the ends of the U-shaped cover plate 10, with a radius of 50mm and spacing of 150mm to prevent the propagation of cracks at the steel-concrete interface. Welding shear studs 7 into the U-shaped cover plate 10 strengthens the bond between the U-shaped cover plate 10 and the concrete, further enhancing the steel-concrete connection. Multiple semicircular notches are also punched into the ends of the U-shaped cover plate 10 to prevent the propagation of cracks at the steel-concrete interface.

[0054] The PBL steel bars 16 and the ordinary steel bars are staggered in the arrangement of the shear nails 7 and the prestressed steel bar 12 pipeline, so that the concrete reinforcement skeleton of the joint section formed by the longitudinal ordinary steel bars 15, the transverse ordinary steel bars 17, the vertical ordinary steel bars 18 and the PBL steel bars 16 is staggered in the arrangement of the shear nails 7 of the steel top plate. In this embodiment, the shear nails 7 transmit the shear force of the joint section, limit interface slippage, prevent concrete lifting, make the force of the joint section smooth, and increase the connection tightness between the concrete and the steel structure. The reinforcement skeleton formed by the overlap of the PBL steel bars 16 and the longitudinal, transverse, and vertical ordinary steel bars 15, 17, and 18 is staggered in the arrangement of the shear nails 7, so that the shear nails 7 of the U-shaped cover plate 10 can be smoothly inserted into the unset concrete.

[0055] This embodiment chooses to pour concrete and vibrate from the opening of the open steel top plate 1 and the concrete pouring holes 19, which solves the difficulty of concrete pouring caused by the complex structure of the steel-concrete joint section and the lack of vibration holes, and reduces the threat of defects such as steel-concrete separation.

[0056] During the specific operation of this embodiment, one end of a plurality of horse plates 13 is vertically welded to the U-shaped cover plate 10, and the other end of the horse plate 13 is placed on the open steel top plate 1 and appropriately weighted before the concrete is initially set, so that the U-shaped cover plate 10 is flush with the open steel top plate 1, and the shear nails 7 under the U-shaped cover plate 10 are inserted into the unset concrete, which can accurately position the U-shaped cover plate 10 and the open steel top plate 1 and improve the welding quality.

[0057] When the concrete strength reaches 90% or above the design strength, the open steel top plate 1 and the U-shaped cover plate 10 are welded and cooled by the cooling belt 20 to form a whole, thereby reducing the occurrence of water leakage, steel-concrete separation and other defects caused by rainwater infiltration during operation. During welding, cooling belts 20 are set on both sides of the weld to reduce the temperature and reduce concrete damage caused by high temperature.

[0058] The present invention cooperates with the concrete pouring holes 19 in the open steel top plate 1 to facilitate the binding construction of the steel bars of the junction section and the pouring and vibration of the concrete, thereby solving the problems of difficulty in pouring concrete, loose vibration, and unevenness caused by the complex structure of the steel-concrete junction section, the large number of longitudinal and transverse partitions of the top and bottom plates, and the dense internal steel bars. The concrete pouring quality is improved, the durability of the steel-concrete junction section is effectively improved, and the subsequent problems of steel-concrete separation, water leakage, and other defects in the steel-concrete junction section are solved.

[0059] Example 2

[0060] refer to Figures 1 to 11 This embodiment provides a construction method for a railway hybrid beam with a rear-mounted U-shaped cover plate for a steel-concrete composite section. This method can solve the problems of difficult concrete pouring, loose and uneven vibration caused by the complex structure of the steel-concrete composite section, the large number of longitudinal and transverse partitions on the top and bottom plates, and the dense internal steel bars. The method specifically includes the following steps:

[0061] Step S1: First, accurately prefabricate the following components according to the drawings. The prefabricated components include:

[0062] Open steel top plate 1, U-shaped cover plate 10, steel bottom plate 3, middle web plate 5, reinforcing web plate 6, side web plate 4, short PBL perforated steel plate 8, shear studs 7, long PBL perforated steel plate 9, bearing plate 2, horse plate 13 and stiffening ribs 14;

[0063] After the opening of the open steel top plate 1, the U-shaped cover plate 10 is removed and the pressure plate 2 is dug at the same time;

[0064] Step S2: Assemble the prefabricated components of step S1, and vertically weld a plurality of short PBL perforated steel plates 8 and a plurality of long PBL perforated steel plates 9 to corresponding positions of the open steel top plate 1, the steel bottom plate 3, and the pressure plate 2 according to a predetermined spacing;

[0065] Step S3: After the steel structure is constructed, the PBL steel bars 16 are passed through the holes and fixed, leaving a hole for the longitudinal prestressed steel bars 12; the longitudinal ordinary steel bars 15, the transverse ordinary steel bars 17, the vertical ordinary steel bars 18 and the PBL steel bars 16 are tied together to form a concrete reinforcement skeleton of the combined section, and the reinforcement skeleton is staggered with the steel top plate shear nails 7;

[0066] Step S4: Weld shear studs 7 onto the U-shaped cover plate 10. The shear studs 7 are arranged in the same manner as the shear studs 7 on the open steel top plate 1. A semicircular notch with a radius of 50 mm is punched at the end of the U-shaped cover plate 1010. Multiple horse plates 13 are welded perpendicularly to the U-shaped cover plate 10 at one end.

[0067] Step S5: pour concrete at the opening of the open steel top plate 1 and the concrete pouring hole 19 and vibrate it. Before the concrete initially sets, place the other end of the horse plate 13 on the open steel top plate 1 and properly weight it so that the U-shaped cover plate 10 is flush with the open steel top plate 1. Insert the shear nails 7 under the U-shaped cover plate 10 into the unset concrete.

[0068] Step S6: When the concrete strength reaches 90% or above the design strength, remove the horse plate 13 and weld the open steel top plate 1 and the U-shaped cover plate 10 to ensure a smooth weld.

[0069] During welding, cooling belts 20 are set on both sides of the weld to cool down the temperature. After welding, the concrete pouring hole 19 is covered with cement mortar to seal the steel top plate.

[0070] Step S7: insert the longitudinal prestressed steel bars 12 into the reserved channel, install anchors, gradually tension the prestressed reinforcement bars, and anchor them; after the tensioning of the prestressed reinforcement bars is completed, pour cement slurry into the reserved channel to protect the prestressed reinforcement bars from rust;

[0071] Step S8: Perform other construction on the casted steel-concrete joint section.

[0072] Although the specific embodiments of the invention are described in detail in conjunction with the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A railway hybrid beam with a rear-mounted U-shaped cover plate and a steel-concrete joint section structure, characterized by: It includes an open steel top plate, a steel bottom plate and a pressure plate; the two ends of the pressure plate are respectively welded to the inner sides of the open steel top plate and the steel bottom plate; A middle web, a reinforcing web and an edge web are provided on one side of the steel-concrete joint section, and a plurality of stiffening ribs are welded to the edge web; the upper and lower sides of the middle web, the reinforcing web and the edge web are longitudinally fixed between the open steel top plate and the steel bottom plate; the open steel top plate or the steel bottom plate is vertically connected to the bottom edges of the plurality of short PBL perforated steel plates and the plurality of long PBL perforated steel plates; The middle web, reinforcing web, side web, short PBL perforated steel plate and long PBL perforated steel plate are all connected to the bearing plate; The open steel top plate is provided with a plurality of U-shaped openings, the opening width of the U-shaped opening is 300mm~1200mm, the opening length is 600~1200mm, the arc radius of the U-shaped opening is 150mm~600mm, and the spacing between two adjacent U-shaped openings is 300mm~900mm; A plurality of short PBL perforated steel plates are fixed to the bottom of the U-shaped opening of the open steel top plate, and the plurality of short PBL perforated steel plates and the plurality of long PBL perforated steel plates are alternately arranged in sequence; It also includes a U-shaped cover plate; the bottom surface of the U-shaped cover plate is welded with shear nails, and the end of the U-shaped cover plate is provided with multiple semicircular notches; The top surface of the U-shaped cover plate is vertically welded to one end of a plurality of horse plates; before the initial setting of the concrete, the other ends of the plurality of horse plates are placed on the open steel top plate and weighted to make the U-shaped cover plate flush with the open steel top plate. The other ends of the plurality of horse plates are placed on the open steel top plate so that the U-shaped cover plate does not sink into the unset concrete, and the shear nails on the bottom surface of the U-shaped cover plate are inserted into the unset concrete; After the concrete strength reaches 90% or above the design strength, the open steel top plate and the U-shaped cover plate are welded, and cooling belts are arranged on both sides of the weld between the open steel top plate and the U-shaped cover plate to form the open steel top plate and the U-shaped cover plate into a whole; The open steel top plate is opened according to the web layout of the steel-concrete joint section, the positions of the short PBL perforated steel plate and the long PBL perforated steel plate, and the U-shaped cover plate is removed. Concrete pouring holes are set on the open steel top plate near the pressure plate.

2. The railway hybrid beam with rear-mounted U-shaped cover steel-concrete combined section structure according to claim 1 is characterized by: The open steel top plate is provided with a concrete pouring hole near the pressure bearing plate.

3. The railway hybrid beam with rear-mounted U-shaped cover steel-concrete combined section structure according to claim 1 is characterized by: The short PBL perforated steel plate and the long PBL perforated steel plate are both provided with a plurality of circular holes with a diameter of 40 to 80 mm. PBL steel bars for strengthening the connection with concrete are passed through the circular holes. The PBL steel bars and the concrete surrounding them form PBL shear keys.

4. The railway hybrid beam with rear-mounted U-shaped cover steel-concrete joint section structure according to claim 3 is characterized by: The open steel top plate, steel bottom plate and pressure plate are all welded with shear nails. The circular holes and ordinary steel bars are staggered with the arrangement of the shear nails and prestressed steel bars, so that the longitudinal ordinary steel bars, transverse ordinary steel bars, vertical ordinary steel bars in the concrete of the steel-concrete joint section and the PBL steel bars form a steel bar skeleton in the concrete of the joint section, and the steel bar skeleton is staggered with the arrangement of the shear nails of the steel top plate.

5. A construction method for a railway hybrid beam with a rear-mounted U-shaped cover plate steel-concrete combined section structure using any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Prefabricate the open steel top plate, U-shaped cover plate, steel bottom plate, middle web plate, reinforced web plate, side web plate, shear studs, short PBL perforated steel plate, long PBL perforated steel plate, bearing plate, horse plate and stiffeners. After the open steel top plate is opened, remove the U-shaped cover plate and dig holes in the PBL plate at the same time. S2. Weld the short PBL perforated steel plates and the long PBL perforated steel plates vertically to the open steel top plate, steel bottom plate and pressure plate according to the spacing, and weld the reinforcing webs, side webs, shear studs and stiffening ribs to complete the fabrication, transportation and erection of the combined steel structure. S3. Pass the PBL steel bars through the holes and secure them, leaving a channel for the longitudinal prestressed steel bars; tie the longitudinal ordinary steel bars, transverse ordinary steel bars, vertical ordinary steel bars and PBL steel bars to form a concrete reinforcement skeleton in the combined section, with the reinforcement skeleton staggered with the shear studs of the open steel top plate; S4. Weld shear studs on the bottom surface of the U-shaped cover plate; punch a semicircular notch at the end of the U-shaped cover plate, and weld one end of multiple horse plates vertically to the edge of the bottom surface of the U-shaped cover plate; S5. Pour concrete at the opening of the open steel top plate and the concrete pouring hole and vibrate it. Before the concrete begins to set, place the other end of the horse plate on the open steel top plate and apply weight to make the U-shaped cover plate flush with the open steel top plate. Insert the shear nails under the U-shaped cover plate into the unset concrete. S6. When the concrete strength reaches 90% or above the design strength, remove the horse plate and weld the open steel top plate and the U-shaped cover plate. Set cooling zones on both sides of the weld. Also weld the concrete pouring hole with a circular steel plate to cover it to close the open steel top plate. S7. Insert the longitudinal prestressed steel bars into the reserved channel, install anchors, gradually tension the prestressed reinforcement bars, and anchor them; after the tensioning of the prestressed reinforcement bars is completed, pour cement slurry into the reserved channel.

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