Fabricated steel-UHPC (Ultra High Performance Concrete) external prestressing combined box girder as well as construction method and application thereof

Abstract

The invention discloses a fabricated steel-UHPC external prestressing combined box girder and a construction method and application thereof, and relates to the technical field of bridge engineering, the fabricated steel-UHPC external prestressing combined box girder comprises a prefabricated steel-UHPC combined top plate, a prefabricated steel-UHPC combined bottom plate, a prefabricated steel-UHPC combined web plate, a steel diaphragm plate and an external prestressing system. The box girders are formed by combining prefabricated slabs, the prefabricated web plates are firmly connected with the prefabricated top plate and the prefabricated bottom plate through welded steel plates and post-poured UHPC, and arrangement and tensioning of external prestress are achieved by arranging steel anchor boxes and steering gears in box chambers. According to the combined box girder, the steel and the UHPC are combined to form a structural form that the steel plate is wrapped by the UHPC, and the advantages of high strength, high durability, high toughness, high compactness, low creep and the like of the UHPC and the advantages of high strength, high elastic modulus and weldability of steel are fully utilized, so that the box girder has the advantages of being excellent in structural stress performance, light in overall weight, good in durability, small in later-stage deformation, low in cost and the like. And the hoisting device is especially suitable for bridges in urban rail transit or urban railways.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering technology, specifically to a prefabricated steel-UHPC external prestressed composite box girder, its construction method, and its application. Background Technology

[0002] Due to their excellent structural integrity and durability, ordinary prestressed concrete box girders are now widely used in urban rail transit and suburban railway bridges. However, ordinary prestressed concrete box girders are heavy, often requiring bridge erection machines for construction, demanding high technical skills. Furthermore, the significant shrinkage and creep of ordinary concrete in the later stages negatively impacts the stability of train operation. With the vigorous development of ultra-high performance concrete (UHPC), it is widely used as the main material in bridge engineering. UHPC possesses advantages such as high strength, high modulus of elasticity, high durability, and low creep. While ensuring durability and strength requirements, it can significantly reduce structural dimensions, lighten structural weight, and reduce later-stage shrinkage and creep deformation.

[0003] In the field of bridge engineering technology, existing technologies have proposed prestressed concrete box girders that utilize UHPC (Underground High-Pressure Polymer) throughout. This structure has numerous UHPC diaphragms and anchor blocks, requiring complex internal and external formwork fabrication and demanding high standards for UHPC casting. Existing technologies have also proposed steel core-UHPC composite box girders, where the steel internal formwork is directly integrated into the box girder. Furthermore, existing technologies have proposed segmental precast steel pin diaphragm UHPC box girders, where the steel diaphragms are cast into the UHPC. Both of these structures still require complex internal and external formwork fabrication, demand high standards for UHPC casting, and lack prestressing, limiting their applicable span.

[0004] Because UHPC (Ultra-High-Pressure Polymer) has different material properties from traditional concrete, specialized construction methods are needed when it is used as the main material for bridge structures. Lighter, thinner structures promote prefabrication, thereby improving overall structural quality and reducing construction difficulty. Therefore, this paper proposes a prefabricated steel-UHPC externally prestressed composite box girder, its construction method, and its application to address these issues. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to propose a prefabricated steel-UHPC external prestressed composite box girder, its construction method and application, so as to solve the problems in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a prefabricated steel-UHPC external prestressed composite box girder and its construction method and application, comprising a prefabricated steel-UHPC composite top slab, a prefabricated steel-UHPC composite bottom slab, a prefabricated steel-UHPC composite web, steel flanges, steel diaphragms and an external prestressing system; The precast steel-UHPC composite web includes a precast steel-UHPC composite outer web and a precast steel-UHPC composite inner web; the steel flange includes a steel edge flange and a steel middle flange.

[0007] Preferably, the precast steel-UHPC composite top plate is composed of a UHPC top plate, a steel top plate, and shear studs; the precast steel-UHPC composite bottom plate is composed of a UHPC bottom plate, a steel bottom plate, and shear studs; the precast steel-UHPC composite web is composed of a UHPC web, a steel web, and shear studs; the precast steel-UHPC composite outer web is located on the side near the steel edge flange; and the precast steel-UHPC composite inner web is located on the side near the steel middle flange.

[0008] Preferably, the precast steel-UHPC composite top plate is fully welded with shear studs on one side of the steel plate, and shear studs are welded at the junction of the steel plate and the steel web on the other side of the steel plate, and steel flange plates are welded laterally on both sides of the same side; the precast steel-UHPC composite bottom plate is fully welded with shear studs on one side of the steel plate; the precast steel-UHPC composite web is fully welded with shear studs on one side of the steel plate.

[0009] Preferably, the precast steel-UHPC composite web has a longitudinally reserved space at both ends of the plate before casting UHPC; the precast steel-UHPC composite bottom plate has a longitudinally reserved space at both ends of the plate before casting UHPC.

[0010] Preferably, the precast steel-UHPC composite top plate and the precast steel-UHPC composite web plate are connected by transverse welding of steel flanges and steel web plates, and by longitudinal welding of steel top plate and steel web plates; the precast steel-UHPC composite web plate and the precast steel-UHPC composite bottom plate are connected by longitudinal welding of steel web plates and steel bottom plates.

[0011] Preferably, a longitudinal top post-cast strip is formed between the precast steel-UHPC composite top plate and the precast steel-UHPC composite web through cast-in-place UHPC; a longitudinal bottom post-cast strip is formed between the precast steel-UHPC composite bottom plate and the precast steel-UHPC composite web through cast-in-place UHPC.

[0012] Preferably, the steel diaphragm has holes for external stress steel strands, and the steel diaphragm is welded to the steel top plate, steel web plate and steel bottom plate. The steel diaphragm and the steel flange plate are arranged in a one-to-one correspondence.

[0013] Preferably, the external prestressing system includes external prestressing steel strands, steel anchor boxes, steel steering gears, and vibration damping devices; the steel anchor boxes, steel steering gears, and vibration damping devices are all welded to the composite box girder.

[0014] Preferably, the precast steel-UHPC composite roof slab has a post-casting space longitudinally left on one side edge of the slab, the steel roof slab is connected by longitudinal welding, the steel flange plate is connected by transverse welding, and the longitudinal roof slab post-casting strip is formed by cast-in-place UHPC.

[0015] As a preferred embodiment, a construction method for a prefabricated steel-UHPC externally prestressed composite box girder includes the following steps: S1: Weld shear studs to one side of the steel roof slab, and cast UHPC on the same side of the steel roof slab; weld shear studs at the junction of the steel roof slab and the web on the other side of the steel roof slab, and weld steel edge flanges laterally on both sides of the same side to form a precast steel-UHPC composite roof slab. S2: Weld shear studs to one side of the steel web, cast UHPC on the same side of the steel web and reserve post-casting space at both ends along the longitudinal direction to form a precast steel-UHPC composite web; S3: Weld shear studs to one side of the steel base plate, pour post-cast UHPC on the same side of the steel base plate and reserve post-casting space at both ends along the longitudinal direction to form a precast steel-UHPC composite base plate; S4: Weld the steel bottom plate and steel top plate to the steel web plate longitudinally; weld the steel flange plate to the steel web plate transversely; S5: A longitudinal top post-cast strip is formed between the precast steel-UHPC composite top slab and the precast steel-UHPC composite web through cast-in-place UHPC, and a longitudinal bottom post-cast strip is formed between the precast steel-UHPC composite bottom slab and the precast steel-UHPC composite web through cast-in-place UHPC. S6: Weld the steel diaphragms to the steel top plate, steel web plate and steel bottom plate one by one; S7: Fabricate steel anchor boxes, steel steering gears, and vibration damping devices, and weld them to the corresponding positions on the composite box girder; S8: Tension external prestressed steel strands and anchor them to the steel anchor box.

[0016] Prefabricated steel-UHPC external prestressed composite box girder is preferred for use in bridges.

[0017] Compared with existing technologies, the prefabricated steel-UHPC external prestressed composite box girder, its construction method, and its application provided by this invention have the following beneficial effects: (1) The prefabricated steel-UHPC external prestressed composite box girder proposed in this invention, from the perspective of structural lightness and prefabrication, divides the prefabricated steel-UHPC external prestressed composite box girder into prefabricated steel-UHPC composite top plate, prefabricated steel-UHPC composite bottom plate, prefabricated steel-UHPC composite web plate, steel flange plate, steel diaphragm plate and external prestressing system, thereby improving the prefabrication level of the structure, reducing the production of internal and external molds, reducing the construction difficulty of the structure and saving production costs.

[0018] (2) The prefabricated steel-UHPC external prestressed composite box girder proposed in this invention has a steel plate mostly wrapped by UHPC. The two work together to enhance the overall load-bearing capacity of the structure, reduce the self-weight of the structure, and improve the durability of the structure.

[0019] (3) The prefabricated steel-UHPC external prestressed composite box girder proposed in this invention adopts an external prestressing system to avoid the increase in structural plate thickness caused by internal prestressing, further reducing the self-weight of the structure, and facilitating later maintenance and replacement; the external prestressed steel strands are arranged and anchored through prefabricated steel deflectors and steel anchor boxes, avoiding the need to set up complex templates and pour UHPC anchor blocks after casting, improving construction efficiency and reducing construction difficulty. Attached Figure Description

[0020] Figure 1 This is a semi-expanded three-dimensional structural diagram of the present invention; Figure 2 This is a schematic diagram of the structural connection relationship in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the structural connection relationship in Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of the cross-section of the shear stud arrangement of the present invention; Figure 5 This is an exploded view of the three-dimensional structure of the present invention; Figure 6 This is a schematic diagram of the structural connection relationship in Embodiment 3 of the present invention.

[0021] In the picture: 1. Precast steel-UHPC composite roof slab; 2. Precast steel-UHPC composite outer web slab; 3. Steel diaphragm; 4. Precast steel-UHPC composite bottom slab; 5. Steel edge flange plate; 6. Steel middle flange plate; 7. Post-cast UHPC; 8. Precast steel-UHPC composite inner web slab. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0024] Example 1: A single-track passenger and freight railway scenario in a mountainous area; A single-track passenger and freight railway in a mountainous area of ​​an underdeveloped country traverses multiple low hills and mountains, requiring numerous bridges with small to medium spans (20-35m). The region has complex geological conditions, with some bridge sites located on steep slopes, making it difficult to access large bridge-building equipment. Furthermore, freight trains carry heavy loads, placing high demands on the bridges' load-bearing capacity and durability, and resulting in significant challenges and costs for subsequent maintenance. Traditional prestressed concrete box girders are heavy, posing high risks during transportation and erection on steep slopes, while ordinary steel bridges have high corrosion protection requirements, making them unsuitable for long-term freight transport needs.

[0025] Considering the load characteristics of single-track railways, this scheme adopts a single-box, single-cell section, simply supported beam structural system, such as... Figure 2 As shown, the width of the precast steel-UHPC composite top slab is designed to be 6.5m, the width of the precast steel-UHPC composite bottom slab is 2.5m, and the spacing between the top of the precast steel-UHPC composite web plates is 3.5m to ensure that the load distribution requirements of the train wheelsets are met. The spacing of the steel diaphragms is set to 2.5m to enhance the lateral stiffness of the structure and avoid lateral deformation caused by heavy freight loads.

[0026] Due to transportation limitations caused by steep slopes in the mountainous area, the weight of prefabricated components was controlled to within 30 tons. Small crawler cranes were used in conjunction with transfer frames for component transportation and erection. Utilizing the modular characteristics of the prefabricated steel-UHPC composite web, top slab, and bottom slab, a temporary prefabrication yard was set up near the bridge site to reduce long-distance transportation costs. During construction, the structure was quickly assembled through longitudinal welding and cast-in-place UHPC post-cast strips, shortening the construction period by 40% compared to traditional box girder construction.

[0027] The advantages of this solution compared to existing technologies are as follows: the high durability of UHPC material can resist corrosion in the humid and foggy environment of mountainous areas; after the steel plates are encased in UHPC, frequent anti-corrosion maintenance is unnecessary, reducing later operating costs. The external prestressing system can be adjusted for secondary tensioning according to changes in freight volume (such as a 15% increase in freight volume later), meeting the load change requirements. At the same time, the structure's self-weight is reduced by approximately 50% compared to traditional concrete box girders, effectively reducing the bearing pressure on bridge piers and reducing the difficulty and cost of foundation construction for bridges in mountainous areas.

[0028] Example 2: A scenario involving a double-track intercity passenger railway; like Figure 3 As shown, a double-track intercity passenger railway in a domestic metropolitan area is designed for a speed of 250 km / h. The line traverses urban areas, and some bridges need to cross existing roads. The standard span of the bridges is 25-35 meters, while the spans of bridges crossing existing roads are greater than 50 meters. This line needs to meet the requirements of simultaneous operation of trains in both directions, which places high demands on the lateral stiffness and torsional performance of the bridges. At the same time, the urban construction environment is complex, requiring coordination with existing traffic to minimize the impact of construction on the lives of surrounding residents.

[0029] This design employs a double-box, single-cell structure, with each box corresponding to one track, connected by steel beams to form a unified structure. The width of the precast steel-UHPC composite roof slab in each box is 5.5m, the top spacing of the precast steel-UHPC composite web plates is 3m, and the longitudinal spacing of the steel diaphragms is 2.5m. Reinforcing steel diaphragms are added at the connection points between the two boxes to enhance overall torsional resistance. An external prestressing system is implemented in each box, with external prestressed steel strands bearing the load of their respective tracks, ensuring balanced structural stress during bidirectional train operation.

[0030] For bridges with conventional spans (25~35m), this scheme adopts a simply supported beam structure system. Compared with traditional concrete box girders, the structural self-weight is reduced by about 50%, allowing for construction using small crawler cranes, eliminating reliance on large bridge erecting machines, effectively reducing construction difficulty, and improving construction efficiency.

[0031] For bridges spanning existing roads (span ≥ 50m), this scheme adopts a continuous rigid frame system and uses the balanced cantilever assembly method for construction. The precast components are longitudinally divided into 5 segments, each weighing less than 30t, and cantilever assembly is carried out using hanging baskets. During assembly, temporary external prestressing tendons are used to fix the components, avoiding disruption to existing road traffic, minimizing the impact on traffic under the bridge, and reducing the impact on the surrounding residents' ecological environment.

[0032] Example 3: A four-line urban rail transit scenario; A double-track railway needs to have a turnaround track or an additional connecting track near the station, thus forming a four-track railway.

[0033] In this scenario, such as Figure 6 As shown, the bridge needs to have a wide width and high lateral stiffness, while also considering its connection with the city's existing infrastructure. During construction, it must ensure the normal operation of urban traffic, and subsequent maintenance must be convenient and efficient.

[0034] The overall bridge width is designed to be 22m, employing a four-box single-cell connected structure. Each box corresponds to one track, and the boxes are connected by steel-UHPC composite crossbeams with a longitudinal spacing of 3m. The width of the precast steel-UHPC composite top slab in each box is 5.2m, and the spacing between the precast steel-UHPC composite web plates is 3.8m. The steel diaphragms use an I-shaped cross-section with a thickness of 16mm to enhance lateral shear and torsional resistance. The external prestressing system is arranged according to the functional zones of the track. Different tracks can have different numbers of prestressed steel strands arranged based on calculations, achieving differentiated stress design and reducing costs.

[0035] Given the dense urban road network, component transportation and erection were carried out at night. A "segmented construction" strategy was adopted, using small crawler cranes for erection. The middle box structure was constructed first, serving as a construction platform, before the side box structures were built, improving construction efficiency and reducing the impact on urban traffic. The cast-in-place UHPC post-pouring strip used self-compacting UHPC material to reduce noise generated by vibration operations and meet urban construction noise control requirements.

[0036] The steel anchor boxes and steel steering gears of the external prestressing system are installed inside the box girder, with an internal space height greater than 2 meters, facilitating subsequent inspection and replacement of the external prestressing steel strands. Simultaneously, fiber optic sensors are embedded within the precast steel-UHPC composite roof slab to monitor structural stress and deformation in real time. Data is wirelessly transmitted to the operation and maintenance management platform, enabling intelligent monitoring of the bridge's condition and reducing manual inspection costs. Furthermore, the high durability of UHPC material extends the bridge's design lifespan and reduces traffic disruption caused by frequent bridge maintenance in urban built-up areas.

[0037] Please refer to the above work process. Figures 1 to 6 .

[0038] It should be noted that, in this document, 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.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A prefabricated steel-UHPC external prestressed composite box girder, characterized in that: It includes a precast steel-UHPC composite top slab (1), a precast steel-UHPC composite bottom slab (4), a precast steel-UHPC composite web, steel flanges, steel diaphragms (3), and an external prestressing system; The precast steel-UHPC composite web includes a precast steel-UHPC composite outer web (2) and a precast steel-UHPC composite inner web (8); the steel flange includes a steel edge flange (5) and a steel middle flange (6).

2. The prefabricated steel-UHPC external prestressed composite box girder according to claim 1, characterized in that: The precast steel-UHPC composite top plate (1) is composed of a UHPC top plate, a steel top plate and shear studs. The precast steel-UHPC composite bottom plate (4) is composed of a UHPC bottom plate, a steel bottom plate and shear studs. The precast steel-UHPC composite web is composed of a UHPC web, a steel web and shear studs. The precast steel-UHPC composite outer web (2) is located on the side near the steel edge flange plate (5). The precast steel-UHPC composite inner web (8) is located on the side near the steel middle flange plate (6).

3. The prefabricated steel-UHPC external prestressed composite box girder according to claim 2, characterized in that: The precast steel-UHPC composite top plate (1) is fully welded with shear studs on one side of the steel plate and with shear studs at the junction of the steel plate and the steel web on the other side. Steel flange plates are welded laterally on both sides of the same side. The precast steel-UHPC composite bottom plate (4) is fully welded with shear studs on one side of the steel plate. The precast steel-UHPC composite web is fully welded with shear studs on one side of the steel plate.

4. The prefabricated steel-UHPC external prestressed composite box girder according to claim 3, characterized in that: The precast steel-UHPC composite web has a longitudinal space reserved at both ends of the plate before casting UHPC (7); the precast steel-UHPC composite bottom plate (4) has a longitudinal space reserved at both ends of the plate before casting UHPC (7).

5. The prefabricated steel-UHPC external prestressed composite box girder according to claim 4, characterized in that: The precast steel-UHPC composite top plate (1) and the precast steel-UHPC composite web are connected by transverse welding of steel flanges and steel web, and by longitudinal welding of steel top plate and steel web; the precast steel-UHPC composite web and the precast steel-UHPC composite bottom plate (4) are connected by longitudinal welding of steel web and steel bottom plate.

6. The prefabricated steel-UHPC external prestressed composite box girder according to claim 5, characterized in that: The precast steel-UHPC composite top plate (1) and the precast steel-UHPC composite web are connected by cast-in-place UHPC to form a longitudinal top post-cast strip; the precast steel-UHPC composite bottom plate (4) and the precast steel-UHPC composite web are connected by cast-in-place UHPC to form a longitudinal bottom post-cast strip; the steel diaphragm (3) is reserved with holes for external tension steel strands, and the steel diaphragm (3) is welded to the steel top plate, steel web and steel bottom plate, and the steel diaphragm (3) is set one-to-one with the steel flange plate.

7. The prefabricated steel-UHPC external prestressed composite box girder according to claim 1, characterized in that: The external prestressing system includes external prestressing steel strands, steel anchor boxes, steel steering gears, and vibration damping devices; the steel anchor boxes, steel steering gears, and vibration damping devices are all welded to the composite box girder.

8. The prefabricated steel-UHPC external prestressed composite box girder according to any one of claims 1-7, characterized in that: The precast steel-UHPC composite top plate (1) has a post-casting space left along the longitudinal direction on one side edge of the plate. The steel top plate is connected by longitudinal welding, and the steel flange plate is connected by transverse welding. The longitudinal top plate post-casting strip is formed by cast-in-place UHPC.

9. A construction method for a prefabricated steel-UHPC externally prestressed composite box girder, applicable to the prefabricated steel-UHPC externally prestressed composite box girder as described in any one of claims 1-8, characterized in that: Includes the following steps: S1: Weld shear studs on one side of the steel roof plate and cast UHPC (7) on the same side of the steel roof plate; weld shear studs at the junction of the steel roof plate and the web plate on the other side, and weld steel edge flanges (5) on both sides of the same side to form a precast steel-UHPC composite roof plate (1). S2: Weld shear studs on one side of the steel web, cast UHPC (7) on the same side of the steel web, and reserve post-casting space at both ends along the longitudinal direction to form a precast steel-UHPC composite top plate (1). S3: Weld shear studs on one side of the steel base plate, pour post-cast UHPC (7) on the same side of the steel base plate, and reserve post-casting space at both ends along the longitudinal direction to form a precast steel-UHPC composite top plate (1). S4: Weld the steel bottom plate and steel top plate to the steel web plate longitudinally; weld the steel middle flange plate (6) to the steel web plate transversely; S5: A longitudinal top post-cast strip is formed between the precast steel-UHPC composite top plate (1) and the precast steel-UHPC composite web through cast-in-place UHPC, and a longitudinal bottom post-cast strip is formed between the precast steel-UHPC composite bottom plate (4) and the precast steel-UHPC composite web through cast-in-place UHPC to cast UHPC (7). S6: Weld the steel diaphragm (3) to the steel top plate, steel web plate and steel bottom plate one by one; S7: Fabricate steel anchor boxes, steel steering gears, and vibration damping devices, and weld them to the corresponding positions on the composite box girder; S8: Tension external prestressed steel strands and anchor them to the steel anchor box.

10. A prefabricated steel-UHPC externally prestressed composite box girder as described in any one of claims 1-9, characterized in that, Applications in bridges.

Images