A UHPC pedestrian bridge U-shaped beam without web reinforcement and its construction method

Abstract

The present invention discloses a UHPC pedestrian bridge U-shaped beam without web reinforcement and its construction method. The U-shaped beam comprises a UHPC base plate and two UHPC web plates, one at each end of the base plate. The two UHPC web plates and the base plate are connected to form a U-shape. Prestressed steel strands are arranged at the upper and lower ends of the UHPC web plates along the longitudinal direction of the bridge. The UHPC web plates do not require stirrups and are provided with multiple ventilation holes. The UHPC pedestrian bridge U-shaped beam without web reinforcement is lightweight, easy to manufacture, quick to erect, has a good landscape effect, and reduces wind resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of bridges, and in particular to a UHPC (ultra-high performance concrete) pedestrian bridge U-shaped beam without web reinforcement and a construction method thereof. Background Art

[0002] Currently, pedestrian bridge construction faces challenges such as tight deadlines, heavy traffic below the bridge, the need to maintain traffic flow, complex and difficult underground pipeline relocation, and increasingly demanding landscape effects. These challenges have led structural engineers to strive for unconventional and innovative approaches when designing pedestrian bridge structures.

[0003] Traditional pedestrian bridge designs, firstly, are limited by project cost constraints and are mostly constructed with concrete, with prefabricated bridge structures being preferred. Concrete structures are now less popular due to their bulkiness, monotony, poor aesthetic appeal, lack of harmony with surrounding urban architecture and the surrounding environment, and the need for scaffolding, which significantly impacts traffic under the bridge. Secondly, steel structures have drawbacks such as high cost, fatigue susceptibility, and poor corrosion resistance. Summary of the Invention

[0004] The main purpose of the present invention is to provide a UHPC pedestrian bridge U-shaped beam without web reinforcement and a construction method thereof. The UHPC pedestrian bridge U-shaped beam without web reinforcement has a light and thin structure, is easy to manufacture, is quick to erect, has a good landscape effect, and has low wind resistance.

[0005] To achieve the above objectives, according to one aspect of the present invention, a UHPC pedestrian bridge U-shaped beam without web reinforcement is provided, comprising a UHPC base plate and two UHPC web plates respectively provided at both ends of the UHPC base plate, wherein the two UHPC web plates and the UHPC base plate are connected to form a U-shape, wherein prestressed steel strands are arranged at the upper and lower ends of the UHPC web plates along the longitudinal direction of the bridge, and a plurality of ventilation holes are provided on the UHPC web plates.

[0006] Furthermore, an upper expansion head is provided at the upper end of the UHPC web, and a lower expansion head is provided at the lower end of the UHPC web. The prestressed steel bundle includes a one-hole prestressed steel bundle and a three-hole prestressed steel bundle. The one-hole prestressed steel bundle is arranged in the upper expansion head, and the three-hole prestressed steel bundle is arranged in the lower expansion head.

[0007] Furthermore, prestressed steel bundle structural reinforcements are provided on the periphery of the one-hole prestressed steel bundle and the three-hole prestressed steel bundle, and longitudinal structural reinforcements are provided in the upper expansion head and the lower expansion head along the longitudinal direction of the bridge, and the prestressed steel bundle structural reinforcements are connected to the longitudinal structural reinforcements.

[0008] Furthermore, transverse stress-bearing steel bars are arranged in the UHPC base plate along the transverse direction of the bridge, and longitudinal structural steel bars are arranged in the UHPC base plate along the longitudinal direction of the bridge. The transverse stress-bearing steel bars are connected to the longitudinal structural steel bars in the UHPC base plate, and the ends of the transverse stress-bearing steel bars are connected to the prestressed steel bundle structural steel bars outside the three-hole prestressed steel bundle.

[0009] Furthermore, the U-shaped beam is formed by splicing a plurality of standard beam sections and two support position beam sections through a splicing assembly.

[0010] Furthermore, the ends of the UHPC webs of the standard beam sections and the beam sections at the fulcrum positions are provided with web shear keys / grooves, and the ends of the UHPC bottom plates of the standard beam sections and the beam sections at the fulcrum positions are provided with bottom plate shear keys / grooves. Adjacent beam sections are spliced ​​together through the web shear keys / grooves and bottom plate shear keys / grooves to form a U-shaped beam.

[0011] Furthermore, no stirrups are provided in the UHPC bottom plate and the UHPC web plate.

[0012] According to another aspect of the present invention, a construction method for the above-mentioned UHPC pedestrian bridge U-shaped beam without web reinforcement is provided, comprising the following steps:

[0013] Step S1: Standard beam segments and support beam segments are prefabricated in the factory and cured. Ventilation holes are reserved before UHPC casting. Plastic bellows for prestressed steel tendons are embedded before UHPC casting. Web shear keys / grooves and bottom plate shear keys / grooves are cast in one go.

[0014] Step S2: Using a long-line prefabrication splicing process, apply epoxy resin adhesive sealant to the joints of each beam segment, install prestressed pipe sealing rings, accurately align the beam segments, accurately align the web shear keys / grooves and bottom plate shear keys / grooves, temporarily tension the prestressed steel tendons, and allow the epoxy resin to cure under a pressure of not less than 0.3 MPa;

[0015] Step S3: After all beam segments are temporarily spliced, the permanent prestressed steel strands are tensioned to put the entire U-shaped beam structure in a compressive state, and grouting and anchoring are performed to complete the U-shaped beam prefabrication.

[0016] Step S4: transport the entire span of the U-shaped beam to the bridge site, hoist the entire span into place, construct auxiliary facilities, and complete the bridge.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention applies ultra-high performance concrete materials to the main structure of the pedestrian overpass. The excellent mechanical properties of UHPC reduce the structural size and greatly reduce the deadweight of the structure, making the pedestrian overpass lighter, more beautiful, and easier to erect and install.

[0019] (2) In the UHPC pedestrian bridge without web reinforcement U-shaped beam of the present invention, the web of the U-shaped beam can be used as a pedestrian railing, eliminating the railing installation process.

[0020] (3) In the UHPC pedestrian bridge without web reinforcement U-shaped beam of the present invention, the entire cross-section of the U-shaped beam structure is placed in a compression state by arranging prestressed steel strands, thereby ensuring the structural safety of the UHPC pedestrian bridge and preventing structural cracking. No web stirrups and longitudinal structural steel bars are required in the middle of the UHPC web, and no stirrups are required in the UHPC bottom plate, thereby saving the amount of ordinary steel bars and avoiding the adverse effects of densely distributed steel bars on the performance of the UHPC.

[0021] (4) In the UHPC pedestrian bridge U-shaped beam without web reinforcement of the present invention, a plurality of ventilation holes are provided on the UHPC web. The ventilation holes can be opened according to the landscape shape, which not only reduces the wind resistance area of ​​the U-shaped beam but also increases the landscape effect.

[0022] (5) The UHPC pedestrian bridge without web reinforcement U-shaped beams of the present invention are prefabricated and spliced ​​in the factory, eliminating the temporary supports or temporary piers at the bridge site. The entire span is hoisted into place at one time, which greatly improves the installation efficiency and minimizes the impact on traffic under the bridge. There is no on-site connection of the beam sections, avoiding the safety risks and hidden dangers brought about by on-site connection construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 This is an elevation view of a standard beam section in the UHPC pedestrian bridge without web reinforcement U-shaped beam of the present invention.

[0025] Figure 2 for Figure 1 Schematic diagram of the AA section.

[0026] Figure 3 for Figure 1 Schematic diagram of the middle BB section.

[0027] Figure 4 This is an elevation view of the beam section at the support point of the U-shaped beam without web reinforcement of the UHPC pedestrian bridge of the present invention.

[0028] Figure 5 for Figure 4 Schematic diagram of the CC section.

[0029] Figure 6 This is a shear key / groove arrangement diagram of the end of the middle beam section of the U-shaped beam without web reinforcement of the UHPC pedestrian bridge of the present invention.

[0030] Figure 7 This is a schematic diagram of the shear key / groove sample of the web of the U-shaped beam without web reinforcement of the UHPC pedestrian bridge of the present invention.

[0031] Figure 8 This is a schematic diagram of the shear key / groove sample of the bottom plate of the U-shaped beam without web reinforcement of the UHPC pedestrian bridge of the present invention.

[0032] Figure 9 The figure is a schematic cross-sectional view of the arrangement of ordinary steel bars in the U-shaped beam without web reinforcement of the UHPC pedestrian bridge of the present invention.

[0033] The above drawings include the following reference numerals:

[0034] 1. UHPC base plate; 2. UHPC web plate; 3. Prestressed steel tendons; 4. Ventilation holes; 5. Prestressed steel tendon structural reinforcement; 6. Longitudinal structural reinforcement; 7. Transverse load-bearing reinforcement; 8. Standard beam section; 9. Beam section at support point; 10. Web shear key / groove; 11. Bottom plate shear key / groove; 21. Upper expansion head; 22. Lower expansion head; 31. One-hole prestressed steel tendons; 32. Three-hole prestressed steel tendons. DETAILED DESCRIPTION

[0035] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0036] Unless otherwise defined, all professional terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The words "one" or "an" and the like used in the patent application specification and claims of the present invention do not indicate a quantity limitation, but rather indicate the presence of at least one. Words such as "connect" or "connected" are not limited to direct connections, but may be indirectly connected through other intermediate connectors. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0037] See also Figures 1 to 9 A UHPC pedestrian bridge U-shaped beam without web reinforcement, according to an embodiment of the present invention, comprises a UHPC base plate 1 and two UHPC web plates 2, one at each end of the base plate 1. The two UHPC web plates 2 are connected to the two ends of the base plate 1 and extend upward to form a U-shaped beam structure. Prestressed steel strands 3 are arranged at the upper and lower ends of the UHPC web plates 2 along the longitudinal direction of the bridge. Multiple ventilation holes 4 are provided in the UHPC web plates 2.

[0038] The aforementioned UHPC pedestrian bridge's unreinforced U-shaped beam utilizes a base plate and web made of ultra-high-performance concrete (UHPC), significantly reducing the beam's structural dimensions, making it lighter and thinner, and easier to erect. By arranging prestressed steel strands 3 along the longitudinal direction of the bridge at the upper and lower ends of the UHPC web 2, the central portion of the UHPC web 2 eliminates the need for stirrups and longitudinal reinforcement. This not only saves on conventional steel but also mitigates the adverse effects of densely packed reinforcement on UHPC performance. By providing multiple ventilation holes 4 in the UHPC web 2, the U-shaped beam's wind resistance area is reduced, enhancing the pedestrian bridge's aesthetic appeal. The UHPC base plate 1 in this U-shaped beam serves as both the bridge deck to bear crowd loads and as a transverse connection, giving the main beam its "U"-shaped cross-section. The UHPC web 2 also serves as pedestrian railings.

[0039] Specifically, in this embodiment, an upper flared head 21 is provided at the upper end of the UHPC web 2, and a lower flared head 22 is provided at the lower end of the UHPC web 2; the prestressed steel strand 3 includes a one-hole prestressed steel strand 31 and a three-hole prestressed steel strand 32, wherein the one-hole prestressed steel strand 31 is pre-embedded in the upper flared head 21 of the UHPC web 2, and the three-hole prestressed steel strand 32 is pre-embedded in the lower flared head 22 of the UHPC web 2.

[0040] This arrangement, by tensioning a single-hole prestressed steel strand 31 and a three-hole prestressed steel strand 32 within the upper and lower flared ends 21 and 22 of the UHPC web 2, places the entire cross-section of the U-shaped beam under compression, ensuring the structural safety of the UHPC pedestrian bridge while preventing structural cracking. The densely distributed fine steel fibers within the UHPC enhance the shear and crack resistance of the U-shaped beam. The prestressed steel strands are embedded in plastic corrugated pipes prior to UHPC casting, using a post-tensioning process.

[0041] Furthermore, in this embodiment, prestressed steel strand structural reinforcement 5 is provided around the periphery of each of the single-hole prestressed steel strand 31 and the three-hole prestressed steel strand 32. Longitudinal structural reinforcement 6 is provided along the longitudinal direction of the bridge within both the upper and lower expanded heads 21 and 22, and the prestressed steel strand structural reinforcement 5 is connected to the longitudinal structural reinforcement 6. Transverse stress-bearing reinforcement 7 is provided along the transverse direction of the bridge within the UHPC base plate 1. Longitudinal structural reinforcement 6 is provided along the longitudinal direction of the bridge within the UHPC base plate 1, and the transverse stress-bearing reinforcement 7 is connected to the longitudinal structural reinforcement 6 within the UHPC base plate 1. The ends of the transverse stress-bearing reinforcement 7 are also connected to the prestressed steel strand structural reinforcement 5 around the periphery of the three-hole prestressed steel strand 32. This arrangement improves the structural strength of the U-shaped beam.

[0042] Furthermore, in this embodiment, stirrups are not installed in either the UHPC base plate 1 or the UHPC web 2. By installing a single-hole prestressed steel strand 31, a three-hole prestressed steel strand 32, and prestressed steel strand structural reinforcement 5 in the UHPC web 2, and providing transverse tension reinforcement 7 in the UHPC base plate 1, both the UHPC base plate 1 and the UHPC web 2 of the U-shaped beam have sufficient strength, eliminating the need for stirrups in the UHPC base plate 1 and the UHPC web 2. This not only reduces the use of ordinary steel bars, but also avoids the adverse effects of densely packed steel bars on UHPC performance.

[0043] In this embodiment, the U-shaped beam comprises several standard beam sections 8 and two support position beam sections 9. These standard beam sections 8 and the two support position beam sections 9 are sequentially spliced ​​together using splicing assemblies to form a U-shaped beam structure, thereby forming an assembled pedestrian overpass U-shaped beam. The two support position beam sections 9 are located at each end of the U-shaped beam, and the several standard beam sections 8 are connected between the two support position beam sections 9.

[0044] Specifically, in this embodiment, web shear keys / grooves 10 are provided at the ends of the UHPC webs 2 of the standard beam segments 8 and the fulcrum beam segments 9; bottom plate shear keys / grooves 11 are provided at the ends of the UHPC bottom plates 1 of the standard beam segments 8 and the fulcrum beam segments 9. Adjacent beam segments are spliced ​​together through the web shear keys / grooves 10 and bottom plate shear keys / grooves 11 to form a U-shaped beam. The two matching web shear keys / grooves 10 or two bottom plate shear keys / grooves 11 are arranged in a concave and convex configuration (i.e., the shear key at the end of one beam segment matches the shear groove at the end of another beam segment). During splicing, it is only necessary to match the web shear keys / grooves 10 and bottom plate shear keys / grooves 11 on the adjacent beam segments, then apply epoxy resin adhesive sealant to the joints of each beam segment, tension the prestressed steel strands, grout, and seal the anchors. The splicing construction is very convenient and quick.

[0045] The construction method of the UHPC pedestrian bridge U-beam without web reinforcement is as follows:

[0046] Step 1: Standard beam segments 8 and support beam segments 9 are prefabricated in the factory and steam-cured. Ventilation holes 4 are reserved before UHPC casting. Plastic bellows for prestressed steel tendons are embedded before UHPC casting. Web shear keys / grooves 10 and bottom plate shear keys / grooves 11 are cast in one go.

[0047] Step 2: Move the cured beam segments to the splicing site;

[0048] Step 3: Use the "long-line method" prefabrication splicing process, apply epoxy resin adhesive sealant to the joints of each beam segment, install prestressed pipe sealing rings, accurately align the beam segments, accurately align the web shear key / groove 10 and the bottom plate shear key / groove 11, temporarily tension the prestressed steel tendons, and allow the epoxy resin to cure under a pressure of not less than 0.3 MPa;

[0049] Step 4: After all beam segments are temporarily spliced, the permanent prestressed steel strands are tensioned to put the entire U-beam structure section under compression, grouting is performed, anchoring is performed, and the U-beam prefabrication is completed;

[0050] Step 5: Transport the entire span of the U-shaped beam to the bridge site, hoist the entire span into place, construct ancillary facilities, and complete the bridge.

[0051] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A UHPC pedestrian bridge U-shaped beam without web reinforcement, characterized in that: It comprises a UHPC base plate (1) and two UHPC webs (2) respectively arranged at both ends of the UHPC base plate (1), wherein the two UHPC webs (2) and the UHPC base plate (1) are connected to form a U-shape, and prestressed steel strands (3) are arranged at the upper and lower ends of the UHPC webs (2) along the longitudinal bridge direction, and a plurality of ventilation holes (4) are opened on the UHPC webs (2); An upper expansion head (21) is provided at the upper end of the UHPC web (2), and a lower expansion head (22) is provided at the lower end of the UHPC web (2). The prestressed steel bundle (3) includes a single-hole prestressed steel bundle (31) and a three-hole prestressed steel bundle (32). The single-hole prestressed steel bundle (31) is arranged in the upper expansion head (21), and the three-hole prestressed steel bundle (32) is arranged in the lower expansion head (22). Prestressed steel bundle structural steel bars (5) are provided on the periphery of the one-hole prestressed steel bundle (31) and the three-hole prestressed steel bundle (32), longitudinal structural steel bars (6) are provided in the upper expansion head (21) and the lower expansion head (22) along the longitudinal bridge direction, and the prestressed steel bundle structural steel bars (5) are connected to the longitudinal structural steel bars (6); The UHPC base plate (1) is provided with transverse stress-bearing steel bars (7) along the transverse bridge direction, and the UHPC base plate (1) is provided with longitudinal structural steel bars (6) along the longitudinal bridge direction. The transverse stress-bearing steel bars (7) are connected to the longitudinal structural steel bars (6) in the UHPC base plate (1), and the ends of the transverse stress-bearing steel bars (7) are connected to the prestressed steel bundle structural steel bars (5) outside the three-hole prestressed steel bundle (32); No stirrups are provided in the UHPC bottom plate (1) and the UHPC web plate (2); The U-shaped beam is formed by splicing a plurality of standard beam sections (8) and two support point position beam sections (9) through a splicing assembly.

2. The UHPC pedestrian bridge U-shaped beam without web reinforcement according to claim 1 is characterized in that: The ends of the UHPC webs (2) of the standard beam section (8) and the support position beam section (9) are both provided with web shear keys / grooves (10), and the ends of the UHPC bottom plates (1) of the standard beam section (8) and the support position beam section (9) are both provided with bottom plate shear keys / grooves (11), and adjacent beam sections are spliced ​​together through the web shear keys / grooves (10) and the bottom plate shear keys / grooves (11) to form the U-shaped beam.

3. The construction method of the UHPC pedestrian bridge U-shaped beam without web reinforcement according to claim 1 or 2, characterized in that: The following steps are involved: Step S1: prefabricate standard beam segments (8) and support beam segments (9) in sections in the factory and perform curing to form them. Ventilation holes (4) are reserved before UHPC casting. Plastic corrugated pipes of prestressed steel strands are embedded before UHPC casting. Web shear keys / grooves (10) and bottom plate shear keys / grooves (11) are cast and formed in one step. Step S2: using a long-line prefabrication splicing process to apply epoxy resin adhesive sealant at the joints of each beam segment, installing a prestressed pipe sealing ring, accurately aligning the beam segments, accurately aligning the web shear key / groove (10) and the bottom plate shear key / groove (11), temporarily tensioning the prestressed steel strands, and allowing the epoxy resin to solidify under a pressure of not less than 0.3 MPa; Step S3: After all beam segments are temporarily spliced, the permanent prestressed steel strands are tensioned to put the entire U-shaped beam structure in a compressed state, and grouting and anchoring are performed to complete the U-shaped beam prefabrication. Step S4: transport the entire span of the U-shaped beam to the bridge site, hoist the entire span into place, construct auxiliary facilities, and complete the bridge.

Images