Box-type composite beam, box-type composite beam construction method and large-span cable-stayed bridge

Abstract

The invention discloses a box-type composite beam, a construction method of the box-type composite beam and a large-span cable-stayed bridge, and relates to the technical field of bridge construction, the box-type composite beam comprises a first bottom plate, a second bottom plate, a third bottom plate and a fourth bottom plate, the first bottom plate is erected on a lower cross beam of a bridge tower of the large-span cable-stayed bridge; the first top plate is arranged on one side, far away from the bridge tower lower cross beam, of the first bottom plate; the first web plate is arranged between the first top plate and the first bottom plate, and the two ends of the first web plate are fixedly connected with the first top plate and the first web plate correspondingly; the prestressed concrete filled steel tube is arranged between the first top plate and the first bottom plate, and the prestressed concrete filled steel tube is fixedly connected with the first top plate, the first bottom plate and the first web plate. The prestressed concrete filled steel tube is arranged in the box-type composite beam erected on the lower cross beam of the bridge tower, and the prestressed concrete filled steel tube is pressed to resist the transverse bending moment, so that the steel consumption of the box-type composite beam is reduced, and the engineering cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, specifically to a box-girder composite beam, a construction method for box-girder composite beams, and a long-span cable-stayed bridge. Background Technology

[0002] With the continuous increase in demand for interconnectivity between land and sea transportation networks, the application of cross-sea bridges is becoming increasingly widespread. Among them, the main bridge of navigation channel needs to meet the requirements of large ships, and often adopts a long-span structural design; while cable-stayed bridges (such as suspension bridges and cable-stayed bridges) have become the mainstream choice for the main bridge of navigation channel in sea areas due to their excellent long-span crossing capacity.

[0003] However, the main span of the navigation channel bridge in the sea area has reached 2000m. Under dead load, in addition to bearing huge axial forces, the main girder in the bridge tower area also has to withstand huge lateral bending moments due to the extreme wind conditions such as high wind speeds, strong gusts, and typhoons that the sea area faces year-round. To resist the lateral bending moments, it is necessary to increase the amount of steel used in the box-girder composite beams at the crossbeams under the bridge towers, which increases the project cost. Summary of the Invention

[0004] This invention provides a box-type composite beam, a construction method for box-type composite beams, and a long-span cable-stayed bridge, which can solve the problem that in order to resist lateral bending moments, it is necessary to increase the amount of steel used in the box-type composite beams at the crossbeams under the bridge towers, thus increasing the project cost.

[0005] In a first aspect, embodiments of the present invention provide a box-type composite beam, the box-type composite beam comprising: The first base plate is erected on the crossbeam under the bridge tower of the long-span cable-stayed bridge. The first top plate is disposed on the side of the first bottom plate away from the lower crossbeam of the bridge tower; The first web plate is disposed between the first top plate and the first bottom plate, and both ends of the first web plate are fixedly connected to the first top plate and the first web plate, respectively. The prestressed steel tube concrete is disposed between the first top plate and the first bottom plate, and is fixedly connected to the first top plate, the first bottom plate, and the first web plate.

[0006] In conjunction with the first aspect, in one embodiment, the prestressed steel-tube concrete comprises: First steel pipe; A shear connector, wherein the shear connector is fixedly disposed on the inner wall of the first steel pipe; Prestressed steel strands are disposed inside the first steel pipe; Concrete, which is filled inside the first steel pipe.

[0007] In conjunction with the first aspect, in one implementation, it includes: A horizontal longitudinal diaphragm, which is perpendicular to the first web plate, and its two ends are fixedly connected to the prestressed steel tube concrete and the first web plate, respectively. A vertical diaphragm, which is parallel to the first web plate, has one end fixedly connected to the prestressed steel pipe concrete and the other end fixedly connected to the first bottom plate or the first top plate.

[0008] In conjunction with the first aspect, in one implementation, it includes: The transverse diaphragm is fixedly connected to the first top plate, the first bottom plate, the first web plate, the prestressed steel pipe concrete, the horizontal longitudinal diaphragm, and the vertical longitudinal diaphragm.

[0009] Secondly, embodiments of the present invention provide a construction method for a box-type composite beam, which includes the following steps: S1, precast multi-segment prestressed steel-concrete composite; S2, the first segment of the box girder composite beam is erected on the crossbeam under the bridge tower of the long-span cable-stayed bridge; S3, the first segment of precast prestressed steel tube concrete is placed inside the first segment of box-type composite beam erected on the crossbeam under the bridge tower of the long-span cable-stayed bridge, the prestressed steel strands inside the first segment of prestressed steel tube concrete are tensioned, and the first segment of prestressed steel tube concrete is fixedly connected to the first segment of box-type composite beam. S4. Continue to erect the next segment of the box-type composite beam. Place the next segment of precast prestressed steel tube concrete into the interior of the next segment of the box-type composite beam, and connect one end of the prestressed steel strand in the prestressed steel tube concrete of this segment to one end of the prestressed steel strand in the previous segment of the precast prestressed steel tube concrete. Tension the prestressed steel strand in the prestressed steel tube concrete of this segment, and fix the prestressed steel tube concrete of this segment to the box-type composite beam of this segment. S5. Repeat step S4 until the construction of the box-type composite beam is completed.

[0010] In conjunction with the second aspect, one implementation includes the following steps: Shear connectors are welded onto the inner wall of the first steel pipe in the prestressed steel-concrete composite tube. The prestressed steel strands are laid inside the first steel pipe; Concrete is filled inside the first steel pipe, and the prestressed steel strands are temporarily tensioned at both ends until the concrete filling the first steel pipe shrinks and creeps to a preset deformation. The prestressed steel strands are then released to complete the prefabrication.

[0011] Thirdly, embodiments of the present invention provide a long-span cable-stayed bridge, using the aforementioned box-girder composite beam, and further comprising: Transition steel box girder, which is erected on both sides of the box-type composite beam; A steel box girder is erected on the side of the transition steel box girder away from the box-type composite beam.

[0012] In conjunction with the third aspect, in one implementation, it further includes: A pressure plate is disposed between the box-type composite beam and the transition steel box beam; the two sides of the pressure plate are fixedly connected to the box-type composite beam and the transition steel box beam, respectively.

[0013] In conjunction with the third aspect, in one embodiment, the transition steel box girder includes: Second roof plate; The second base plate is disposed on one side of the second top plate; The second web plate is disposed between the second top plate and the second bottom plate, and its two ends are fixedly connected to the second top plate and the second bottom plate respectively. A horizontal stiffening rib is provided between the second top plate, the second bottom plate and the second web plate, and is fixedly connected to the second web plate and the pressure plate, respectively. The vertical stiffening rib is disposed between the second top plate, the second bottom plate and the second web plate, and is fixedly connected to the second top plate, the second bottom plate and the pressure plate respectively.

[0014] In conjunction with the third aspect, in one embodiment, the steel box girder includes: Third roof slab; The third base plate is disposed on one side of the third top plate, and the third base plate and the third top plate are connected to form a whole; The third web plate is disposed between the third top plate and the third bottom plate, and its two ends are fixedly connected to the third top plate and the third bottom plate respectively.

[0015] The beneficial effects of the technical solutions provided by the embodiments of the present invention include: This invention discloses a box-type composite beam, a construction method for the box-type composite beam, and a long-span cable-stayed bridge. The box-type composite beam includes: a first bottom plate, which is erected on the lower crossbeam of the bridge tower of a long-span cable-stayed bridge; a first top plate, which is disposed on the side of the first bottom plate away from the lower crossbeam of the bridge tower; a first web, which is disposed between the first top plate and the first bottom plate, and whose two ends are fixedly connected to the first top plate and the first web, respectively; and prestressed steel tube concrete, which is disposed between the first top plate and the first bottom plate, and is fixedly connected to the first top plate, the first bottom plate, and the first web. This invention uses prestressed steel tube concrete inside the box-type composite beam erected on the lower crossbeam of the bridge tower. The prestressed steel tube concrete resists lateral bending moment under compression, reducing the amount of steel used in the box-type composite beam and lowering the project cost. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is an elevation view of a long-span cable-stayed bridge according to an embodiment of the present invention; Figure 2 This is a detailed drawing of a long-span cable-stayed bridge (A) according to an embodiment of the present invention. Figure 3 This is a standard cross-sectional view of a box-type composite beam according to an embodiment of the present invention; Figure 4 This is a standard cross-sectional view of the transition steel box girder according to an embodiment of the present invention; Figure 5 This is a standard cross-sectional view of the steel box girder according to an embodiment of the present invention; Figure 6 This is a detailed drawing of box-type composite beam B according to an embodiment of the present invention; Figure 7 This is a cross-sectional view of the long-span cable-stayed bridge I-I according to an embodiment of the present invention; Figure 8 This is a cross-sectional view of the long-span cable-stayed bridge II-II according to an embodiment of the present invention; Figure 9 This is a detailed drawing of the transition steel box girder C according to an embodiment of the present invention.

[0018] In the diagram: 1. Box-type composite beam; 11. Prestressed steel-concrete composite beam; 111. First steel pipe; 112. Concrete; 113. Prestressed steel strands; 114. Shear connector; 12. First top plate; 13. First bottom plate; 14. First web; 15. Horizontal longitudinal diaphragm; 16. Vertical longitudinal diaphragm; 17. Transverse diaphragm; 2. Transition steel box girder; 22. Second top plate; 23. Second bottom plate; 24. Second web; 25. Horizontal stiffener; 26. Vertical stiffener; 3. Steel box girder; 32. Third top plate; 33. Third bottom plate; 34. Third web; 4. Bearing plate. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The main beams in the bridge tower area of ​​the cross-sea bridge are typical compression-bending members. If a pure steel main beam structure is used, it will pose a severe challenge to the strength and stability of the structure. It will not only significantly increase the amount of steel used and increase the project cost, but may also affect the rationality of the structural stress system and be detrimental to the optimization of overall mechanical performance.

[0021] like Figure 1 , 2 As shown in Figure 3, this embodiment of the invention provides a box-type composite beam 1, which includes: a first bottom plate 13, which is erected on the lower crossbeam of the bridge tower of a long-span cable-stayed bridge; a first top plate 12, which is disposed on the side of the first bottom plate 13 away from the lower crossbeam of the bridge tower; a first web 14, which is disposed between the first top plate 12 and the first bottom plate 13, and both ends of the first web 14 are fixedly connected to the first top plate 12 and the first web 14 respectively; and a prestressed steel tube concrete 11, which is disposed between the first top plate 12 and the first bottom plate 13, and is fixedly connected to the first top plate 12, the first bottom plate 13, and the first web 14.

[0022] The box-girder composite girder 1 includes a first bottom plate 13 erected on the lower crossbeam of the bridge tower of a long-span cable-stayed bridge and a first top plate 12 disposed on the side of the first bottom plate 13 away from the lower crossbeam of the bridge tower. The first bottom plate 13 and the first top plate 12 are fixedly connected at both ends to form a whole. Multiple webs are also provided inside the box-girder composite girder 1, and the two ends of the webs are fixedly connected to the first bottom plate 13 and the first top plate 12 respectively.

[0023] Multiple webs include multiple first webs 14 disposed inside the box-type composite beam 1 near the connection between the first bottom plate 13 and the first top plate 12.

[0024] There are two prestressed steel tube concrete 11s, which are set inside the box-type composite beam 1 along the direction of the main beam. The prestressed steel tube concrete 11s are also close to the connection between the first bottom plate 13 and the first top plate 12, and are welded to the first web plate 14, the first bottom plate 13, and the first top plate 12 to form a whole.

[0025] When encountering extreme wind conditions such as high wind speeds, strong gusts, and typhoons, the prestressed steel-concrete composite tube 11 installed on one side of the box-girder composite beam 1 will deform under compression, generating a force to resist lateral bending moment and improving the load-bearing capacity of the box-girder composite beam 1. Placing the prestressed steel-concrete composite tube 11 on both sides of the web of the box-girder composite beam 1 allows the concrete to fully utilize its compressive strength under the combined action of dead load and extreme crosswinds, significantly improving the load-bearing capacity of the main beam.

[0026] When this invention is applied to the bridge towers of a cable-stayed-suspension bridge with a main span of 1800m, and the main tower area uses a box-girder composite beam with a UHPC concrete cross-sectional area to steel cross-sectional area ratio of 1:1, compared with a pure steel box girder, the compressive stress of the steel structure under dead load can be reduced from 187MPa to 138MPa, and under the combined action of dead load and extreme crosswind, the compressive stress of the steel structure can be reduced from 458MPa to 336MPa. Through the above data comparison, the advantages of this invention are obvious; it can significantly reduce the stress on the main girder steel structure, reduce the amount of steel used, and save on project costs.

[0027] This invention incorporates prestressed steel-concrete composite beams mounted on the crossbeams beneath bridge towers. The prestressed steel-concrete composite beams resist lateral bending moments through bending compression, thereby reducing the amount of steel used in the box-type composite beams and lowering project costs.

[0028] like Figure 6 , 8 As shown, in one embodiment, the prestressed steel-concrete composite tube 11 includes: a first steel pipe 111; a shear connector 114, the shear connector 114 being fixedly disposed on the inner wall of the first steel pipe 111; a prestressed steel strand 113, the prestressed steel strand 113 being disposed inside the first steel pipe 111; and concrete 112, the concrete 112 being filled inside the first steel pipe 111.

[0029] The shear connector 114 installed inside the first steel pipe 111 ensures that the first steel pipe 111 and the internally poured concrete 112 can work together. By effectively transferring the shear force at the interface between the two, relative slippage and vertical separation are prevented, thereby improving the load-bearing capacity and stiffness of the overall structure.

[0030] Multiple prestressed steel strands 113 are arranged inside the first steel pipe 111. Before the load is applied, the prestressed steel strands 113 are tensioned and prestress is generated in the concrete 112. This can effectively counteract the tensile stress in the concrete 112 caused by the external load, thereby improving crack resistance and stiffness, delaying the appearance of cracks and limiting their development.

[0031] Concrete 112 is a high-strength UHPC concrete.

[0032] Under the combined action of dead load and extreme crosswind, a tensile stress of about 12 MPa will be generated in concrete 112. In order to prevent concrete 112 from cracking, prestress is applied to concrete 112 so that the tensile stress in concrete 112 is within the allowable value under the most unfavorable combination of action during the operation phase, which effectively prevents concrete cracking.

[0033] This invention, by setting prestressed steel strands inside prestressed steel tube concrete, can effectively counteract the tensile stress caused by external loads, thereby improving the crack resistance and stiffness of prestressed steel tube concrete.

[0034] like Figure 6 , 7 As shown, in one embodiment, it includes: a horizontal longitudinal diaphragm 15, which is perpendicular to the first web 14, and its two ends are fixedly connected to the prestressed steel tube concrete 11 and the first web 14 respectively; and a vertical longitudinal diaphragm 16, which is parallel to the first web 14, with one end fixedly connected to the prestressed steel tube concrete 11 and the other end fixedly connected to the first bottom plate 13 or the first top plate 12.

[0035] A horizontal longitudinal diaphragm 15 and a vertical longitudinal diaphragm 16 are fixedly connected to the outermost first steel pipe 111 of the prestressed steel-concrete composite tube 11. The horizontal longitudinal diaphragm 15 is also fixedly connected to the first web 14, and the vertical longitudinal diaphragm 16 is also fixedly connected to the first bottom plate 13 or the first top plate 12. Furthermore, the first steel pipe 111 is fixedly connected to the horizontal longitudinal diaphragm 15 and the vertical longitudinal diaphragm 16 by welding; the horizontal longitudinal diaphragm 15 and the vertical longitudinal diaphragm 16 are also fixedly connected to the first web 14, the first bottom plate 13, and the first top plate 12 by welding to form a whole.

[0036] This invention uses horizontal and vertical longitudinal diaphragms to fix and connect prestressed steel tube concrete and box-type composite beams into a whole.

[0037] like Figure 6 , 7 As shown in Figure 8, in one embodiment, it includes: a transverse diaphragm 17, which is fixedly connected to the first top plate 12, the first bottom plate 13, the first web plate 14, the prestressed steel pipe concrete 11, the horizontal longitudinal diaphragm 15, and the vertical longitudinal diaphragm 16.

[0038] To further enhance the stability of the connection structure between the prestressed steel-concrete composite tube 11 and the box girder, transverse diaphragms 17 are installed at intervals along the longitudinal direction of the bridge. The transverse diaphragms 17 are perpendicular to the centerline of the prestressed steel-concrete composite tube 11 and are located outside the prestressed steel-concrete composite tube 11. The transverse diaphragms 17 are also fixedly connected to the first top plate 12, the first bottom plate 13, the first web plate 14, the horizontal longitudinal diaphragms 15, and the vertical longitudinal diaphragms 16 to form a whole.

[0039] This invention increases the stability of the combination of prestressed steel tube concrete and box girder by setting transverse diaphragms fixedly connected to the first top plate, first bottom plate, first web plate, horizontal longitudinal diaphragm and vertical longitudinal diaphragm on the outside of the prestressed steel tube concrete.

[0040] like Figure 3 , 6 As shown in Figure 8, this embodiment of the invention also provides a construction method for a box-type composite beam. Using the aforementioned box-type composite beam, the method includes the following steps: S1, precasting multiple segments of prestressed steel-concrete composite beam 11; S2, erecting the first segment of the box-type composite beam 1 onto the lower crossbeam of the bridge tower of a long-span cable-stayed bridge; S3, placing the first segment of precast prestressed steel-concrete composite beam 11 inside the first segment of the box-type composite beam 1 erected on the lower crossbeam of the bridge tower of a long-span cable-stayed bridge, tensioning the prestressed steel strands 113 inside the first segment of the prestressed steel-concrete composite beam 11, and connecting the first segment of the prestressed steel-concrete composite beam 11 with the first segment of the box-type composite beam. S4. Continue to erect the next segment of the box-type composite beam 1, place the next segment of precast prestressed steel pipe concrete 11 into the interior of the next segment of the box-type composite beam 1, and connect one end of the prestressed steel strand 113 in the prestressed steel pipe concrete 11 to one end of the prestressed steel strand 113 in the previous segment of the precast prestressed steel pipe concrete 11, tension the prestressed steel strand 113 in the prestressed steel pipe concrete 11, and fix the prestressed steel pipe concrete 11 to the box-type composite beam 1; S5. Repeat step S4 until the construction of the box-type composite beam 1 is completed.

[0041] The prestressed steel-concrete composite tube 11 needs to be prefabricated before the main bridge construction and stored for at least 6 months to allow the concrete 112 inside the prestressed steel-concrete composite tube 11 to shrink and creep to the predetermined deformation. During the erection process, the box girder composite beam 1 needs to be erected first on the crossbeam under the bridge tower of the long-span cable-stayed bridge, and then the prefabricated prestressed steel-concrete composite tube 11 is fixedly connected to the inside of the box girder composite beam 1, near both sides of the box girder composite beam 1. Furthermore, the prestressed steel-concrete composite tube 11 is welded to the inside of the box girder composite beam 1 through horizontal longitudinal diaphragms 15 and vertical longitudinal diaphragms 16.

[0042] Furthermore, since the box-type composite beam 1 is too large and inconvenient to construct, the box-type composite beam 1 is designed to be connected by multiple segments of box-type composite beam 1.

[0043] First, the first segment of the box-girder composite beam 1 is erected onto the lower crossbeam of the bridge tower of the long-span cable-stayed bridge. Then, the first segment of precast prestressed steel tube concrete 11 is placed inside the first segment of the box-girder composite beam 1 erected on the lower crossbeam of the bridge tower of the long-span cable-stayed bridge. After the prestressed steel strands 113 inside the first segment of precast prestressed steel tube concrete 11 are tensioned, the first segment of precast prestressed steel tube concrete 11 is fixedly connected to the first segment of the box-girder composite beam 1.

[0044] After the first segment of the box-type composite beam 1 is fixedly connected to the first segment of the precast prestressed steel tube concrete 11, the second segment of the box-type composite beam 1 is erected on both sides of the first segment of the box-type composite beam 1, and the second segment of the box-type composite beam 1 is fixedly connected to the first segment of the box-type composite beam 1 to form a whole. Then, the second segment of the precast prestressed steel tube concrete 11 is placed inside the second segment of the box-type composite beam 1, and one end of the prestressed steel strand 113 inside the second segment of the precast prestressed steel tube concrete 11 is connected to the prestressed steel strand 113 inside the first segment of the precast prestressed steel tube concrete 11. After the prestressed steel strand 113 inside the second segment of the precast prestressed steel tube concrete 11 is tensioned, the second segment of the precast prestressed steel tube concrete 11 is fixedly connected to the second segment of the box-type composite beam 1. Furthermore, connectors are provided at both ends of the prestressed steel strand 113, and the prestressed steel strands 113 inside the two segments of the precast prestressed steel tube concrete 11 are connected to form a whole through the connectors.

[0045] The next segment of the box-type composite beam 1 is erected sequentially on both sides of the box-type composite beam 1 that is connected as a whole until the construction of the box-type composite beam 1 is completed.

[0046] Furthermore, the number of prestressed steel strands 113 inside the precast prestressed concrete tube 11 decreases sequentially from the bridge tower towards both ends. Since the lateral bending moment borne by the main beam gradually decreases from the bridge tower towards both sides, the number of prestressed steel strands 113 inside the precast prestressed concrete tube 11 inside the multi-segment box-girder composite beam 1 can be reduced sequentially from the bridge tower towards both ends to save steel usage.

[0047] This invention first erects a box-type composite beam, then welds prestressed steel-concrete composite tubes, and first tensions and preserves the prestress at both ends of the steel-concrete composite tubes for 6 months to fully release the shrinkage and creep deformation of the concrete before combining it with the steel beam, which can reduce the stress redistribution of the concrete.

[0048] like Figure 6 , 8As shown, in one embodiment, the precast multi-segment prestressed steel tube concrete 11 includes the following steps: welding shear connectors 114 to the inner wall of the first steel tube 111 of the prestressed steel tube concrete 11; laying prestressed steel strands 113 inside the first steel tube 111; filling the inside of the first steel tube 111 with concrete 112, and tensioning the prestressed steel strands 113 at both ends until the concrete 112 filling the first steel tube 111 shrinks and creeps to a preset deformation, thus completing the precasting.

[0049] The shear connector 114 is welded to the inner wall of the first steel pipe 111 and is connected to the first steel pipe 111 to form an integral whole.

[0050] Concrete 112 is poured inside the first steel pipe 111. Prestressed steel strands 113 are also installed in the concrete 112 to resist the tensile stress generated in the concrete 112 under crosswind.

[0051] The prestressed steel-concrete composite tube 11 is prefabricated before the main bridge construction and stored for at least 6 months. During storage, the prestressed steel strands 113 at both ends of the prestressed steel-concrete composite tube 11 should be tensioned to fully release the shrinkage and creep of the prestressed steel-concrete composite tube 11. After 6 months of storage, the prestressed steel strands 113 are removed.

[0052] By pouring concrete 112 inside the first steel pipe 111, the confinement effect of the steel pipe on the concrete can be fully utilized, effectively improving the compressive strength of the concrete, thereby reducing the cross-sectional area of ​​the concrete and effectively avoiding the problem of concrete cracking.

[0053] This invention connects the prestressed concrete tube prestressed steel tube to the box girder after the prestressing is completed, which can effectively prevent the prestress from being transferred to the steel beam section.

[0054] like Figure 1 , 2 As shown, this embodiment of the invention also provides a long-span cable-stayed bridge using the aforementioned box-type composite beam, and further includes: a transition steel box girder 2, which is erected on one side of the box-type composite beam 1; and a steel box girder 3, which is erected on the side of the transition steel box girder 2 away from the box-type composite beam 1.

[0055] The main girder of the long-span cable-stayed bridge consists of three parts: a box girder composite beam 1, a transition steel box girder 2, and a steel box girder 3. The box girder composite beam 1 is erected on the crossbeam under the bridge tower. Both sides of the box girder composite beam 1 are connected to one side of the transition steel box girder 2 via bearing plates 4. The other side of the transition steel box girder 2 is also connected to the steel box girder 3. Based on the stress characteristics of the main girder at different locations, the main girder bears axial compression and lateral bending moment at the bridge tower, where the box girder composite beam 1 can save steel. The main girder experiences less stress further away from the bridge tower, so the lightweight steel box girder 3 is used. To ensure a smooth transfer of load from the steel box girder 3 to the box girder composite beam 1, a transition steel box girder 2 is installed between the box girder composite beam 1 and the steel box girder 3.

[0056] This invention ensures that the load on the steel box girder is transferred to the box-type composite girder by setting a transition steel box girder between the box-type composite girder and the steel box girder.

[0057] like Figure 1 , 2 As shown in Figures 7 and 8, in one embodiment, the system further includes a pressure plate 4, which is disposed between the box-type composite beam 1 and the transition steel box beam 2; the two sides of the pressure plate 4 are fixedly connected to the box-type composite beam 1 and the transition steel box beam 2, respectively.

[0058] The main girder of the long-span cable-stayed bridge consists of three parts: a box-girder composite girder 1, a transition steel box girder 2, and a steel box girder 3. The box-girder composite girder 1 is erected on the crossbeam under the bridge tower. Both sides of the box-girder composite girder 1 are connected to one side of the transition steel box girder 2 through bearing plates 4. The other side of the transition steel box girder 2 is also fixedly connected to the steel box girder 3.

[0059] This invention ensures that the load on the steel box girder is smoothly transferred to the box girder by setting a transition steel box girder between the box-type composite girder and the steel box girder, and by fixing the box-type composite girder and the transition steel box girder together with a bearing plate.

[0060] like Figure 4 , 9 As shown, in one embodiment, the transition steel box girder 2 includes: a second top plate 22; A second base plate 23 is disposed on one side of the second top plate 22; a second web plate 24 is disposed between the second top plate 22 and the second base plate 23, with its two ends fixedly connected to the second top plate 22 and the second base plate 23 respectively; a horizontal stiffening rib 25 is disposed between the second top plate 22, the second base plate 23 and the second web plate 24, and is fixedly connected to the second web plate 24 and the pressure plate 4 respectively; and a vertical stiffening rib 26 is disposed between the second top plate 22, the second base plate 23 and the second web plate 24, and is fixedly connected to the second top plate 22, the second base plate 23 and the pressure plate 4 respectively.

[0061] The transition steel box girder 2 includes a second bottom plate 23 and a second top plate 22 disposed on one side of the second bottom plate 23. The second bottom plate 23 and the second top plate 22 are fixedly connected at both ends to form a whole. Multiple webs are also provided inside the transition steel box girder 2, and the two ends of the webs are fixedly connected to the second bottom plate 23 and the second top plate 22 respectively.

[0062] Multiple webs include multiple second webs 24 disposed inside the transition steel box girder 2 near the connection between the second bottom plate 23 and the second top plate 22.

[0063] The transition steel box girder 2 has the same shape and structure as the box-type composite girder 1, and the positions of the multiple webs inside the transition steel box girder 2 also correspond one-to-one with the positions of the multiple webs inside the box-type composite girder 1. The multiple webs are fixedly connected to the bearing plate 4.

[0064] The transition steel box girder 2, corresponding to the prestressed steel tube concrete 11 position of the box-type composite beam 1, is equipped with multiple horizontal stiffeners 25 and multiple vertical stiffeners 26. The horizontal stiffeners 25 and vertical stiffeners 26 can smoothly transition the stress of the steel box girder 3 to the box-type composite beam 1.

[0065] This invention connects the box-type composite beam and the steel box beam into a smooth whole by setting a transition steel box beam with the same shape and structure as the box-type composite beam.

[0066] like Figure 5 As shown, in one embodiment, the steel box girder 3 includes: a third top plate 32; a third bottom plate 33, the third bottom plate 33 being disposed on one side of the third top plate 32, the third bottom plate 33 being connected to the third bottom plate 33 to form an integral whole; and a third web plate 34, the third web plate 34 being disposed between the third top plate 32 and the third bottom plate 33, with its two ends being fixedly connected to the third top plate 32 and the third bottom plate 33 respectively.

[0067] The shape of the steel box girder 3 is the same as that of the box-type composite girder 1 and the transition steel box girder 3. The steel box girder 3 is the suspended part of the main beam and is mainly used for vehicles that pass under load.

[0068] The steel box girder 3 includes a third bottom plate 33 and a third top plate 32 disposed on one side of the third bottom plate 33. The third bottom plate 33 and the third top plate 32 are fixedly connected at both ends to form a whole. Multiple third web plates 34 are also provided inside the transition steel box girder 3. The two ends of the third web plates 34 are fixedly connected to the third bottom plate 33 and the third top plate 32 respectively, and the multiple third web plates 34 correspond one-to-one with the multiple web plates disposed inside the transition steel box girder 2.

[0069] This invention ensures that the box girder, steel box girder, and transition steel box girder are smoothly connected into a whole by setting a steel box girder with the same shape and structure as the box girder composite beam.

[0070] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0071] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0072] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A box-type composite beam, characterized in that, The box-type composite beam (1) includes: The first base plate (13) is erected on the crossbeam under the bridge tower of the long-span cable-stayed bridge; The first top plate (12) is located on the side of the first bottom plate (13) away from the lower crossbeam of the bridge tower; The first web plate (14) is disposed between the first top plate (12) and the first bottom plate (13), and the two ends of the first web plate (14) are fixedly connected to the first top plate (12) and the first web plate (14) respectively. Prestressed steel tube concrete (11) is disposed between the first top plate (12) and the first bottom plate (13), and the prestressed steel tube concrete (11) is fixedly connected to the first top plate (12), the first bottom plate (13) and the first web plate (14).

2. A box-type composite beam according to claim 1, characterized in that, The prestressed steel-concrete composite tube (11) includes: First steel pipe (111); Shear connector (114), which is fixedly disposed on the inner wall of the first steel pipe (111); Prestressed steel strands (113) are disposed inside the first steel pipe (111); Concrete (112) is filled inside the first steel pipe (111).

3. A box-type composite beam according to claim 1, characterized in that, include: A horizontal longitudinal diaphragm (15) is perpendicular to the first web plate (14), and its two ends are fixedly connected to the prestressed steel pipe concrete (11) and the first web plate (14), respectively. A vertical diaphragm (16) is parallel to the first web plate (14), one end of which is fixedly connected to the prestressed steel pipe concrete (11), and the other end of which is fixedly connected to the first bottom plate (13) or the first top plate (12).

4. A box-type composite beam according to claim 3, characterized in that, include: The transverse diaphragm (17) is fixedly connected to the first top plate (12), the first bottom plate (13), the first web plate (14), the prestressed steel pipe concrete (11), the horizontal longitudinal diaphragm (15), and the vertical longitudinal diaphragm (16).

5. A construction method for a box-type composite beam, using the box-type composite beam according to any one of claims 1-4, characterized in that, Includes the following steps: S1, precast multi-segment prestressed steel tube concrete (11). S2, the first segment of the box-type composite beam (1) is erected on the crossbeam under the bridge tower of the long-span cable-stayed bridge; S3, place the first segment of precast prestressed steel pipe concrete (11) into the interior of the first segment of box-type composite beam (1) erected on the crossbeam under the bridge tower of the long-span cable-stayed bridge, tension the prestressed steel strands (113) inside the first segment of prestressed steel pipe concrete (11), and fix the first segment of prestressed steel pipe concrete (11) to the first segment of box-type composite beam (1); S4, continue to erect the next segment of box-type composite beam (1), put the next segment of precast prestressed steel pipe concrete (11) into the inside of the next segment of box-type composite beam (1), and connect one end of the prestressed steel strand (113) in the segment of prestressed steel pipe concrete (11) to one end of the prestressed steel strand (113) in the previous segment of precast prestressed steel pipe concrete (11), tension the prestressed steel strand (113) in the segment of prestressed steel pipe concrete (11), and fix the segment of prestressed steel pipe concrete (11) to the segment of box-type composite beam (1); S5, repeat step S4 until the construction of the box-type composite beam (1) is completed.

6. The construction method for a box-type composite beam according to claim 5, characterized in that, The precast multi-segment prestressed steel-tube concrete (11) includes the following steps: A shear connector (114) is welded on the inner wall of the first steel pipe (111) of the prestressed steel-concrete composite tube (11). The prestressed steel strands (113) are laid inside the first steel pipe (111); The first steel pipe (111) is filled with concrete (112), and the prestressed steel strands (113) are temporarily tensioned at both ends until the concrete (112) filled in the first steel pipe (111) shrinks and creeps to the preset deformation, and the prestressed steel strands (113) are released to complete the prefabrication.

7. A long-span cable-stayed bridge, using the box-girder composite beam as described in any one of claims 1-4, characterized in that, Also includes: Transition steel box girder (2), the transition steel box girder (2) is erected on both sides of the box-type composite beam (1); A steel box girder (3) is erected on the side of the transition steel box girder (2) away from the box-type composite beam (1).

8. A long-span cable-stayed bridge according to claim 7, characterized in that, Also includes: The pressure plate (4) is disposed between the box-type composite beam (1) and the transition steel box beam (2); the two sides of the pressure plate (4) are fixedly connected to the box-type composite beam (1) and the transition steel box beam (2) respectively.

9. A long-span cable-stayed bridge according to claim 8, characterized in that, The transition steel box girder (2) includes: Second top plate (22); The second base plate (23) is disposed on one side of the second top plate (22); The second web plate (24) is disposed between the second top plate (22) and the second bottom plate (23), and its two ends are fixedly connected to the second top plate (22) and the second bottom plate (23) respectively; Horizontal stiffening rib (25) is provided between the second top plate (22), the second bottom plate (23) and the second web plate (24), and is fixedly connected to the second web plate (24) and the pressure plate (4) respectively; Vertical stiffening rib (26) is provided between the second top plate (22), the second bottom plate (23) and the second web plate (24), and is fixedly connected to the second top plate (22), the second bottom plate (23) and the pressure plate (4) respectively.

10. A long-span cable-stayed bridge according to claim 9, characterized in that, The steel box girder (3) includes: Third top plate (32); The third base plate (33) is disposed on one side of the third top plate (32), and the third base plate (33) is connected to the third top plate (32) to form a whole; The third web plate (34) is disposed between the third top plate (32) and the third bottom plate (33), and its two ends are fixedly connected to the third top plate (32) and the third bottom plate (33) respectively.

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