Linear type pre-tensioning method small box girder with corrugated steel plates embedded in girder ends and manufacturing method of linear type pre-tensioning method small box girder
By embedding corrugated steel plates into the web of the small box girder and combining it with pre-tensioning construction, the problems of non-dense prestressed ducts and complex design of broken line reinforcement in post-tensioning were solved, achieving improvements in durability and construction convenience. The web is designed with a uniform cross-section and thin walls, reducing self-weight and cost.
Patent Information
- Application Number
- CN202511538101.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-27
- Publication Date
- 2026-01-27
AI Technical Summary
The existing post-tensioned prestressed construction process suffers from problems such as loose prestressing ducts, potential corrosion risks, and complex beam end structures. Furthermore, the broken-line prestressing tendon design of the pre-tensioned small box girder increases the construction difficulty, making it difficult to promote its application.
The straight-line pre-tensioned small box girder structure adopts corrugated steel plates embedded in the beam ends. By embedding corrugated steel plates in the web to bear shear force, the broken-line prestressing tendons in the web are eliminated. All-straight prestressed steel strands are used and arranged in the bottom plate. Combined with the pre-tensioning method, the bonding strength between the corrugated steel plates and concrete is ensured, and PVC pipes are sleeved on the steel strands to form a debonding section.
This has improved the durability and ease of construction of the prestressed system. The web can be made into a thin-walled structure with a uniform cross-section, reducing self-weight and prefabrication costs, simplifying the construction process, and improving demolding efficiency.
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Figure CN121407481A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of precast concrete bridge assembly technology, specifically to a linear pre-tensioned small box girder with corrugated steel plates embedded in the beam ends and its manufacturing method. Background Technology
[0002] Prestressed concrete small box girder bridges have become a common bridge type for small and medium-span municipal and highway bridges due to their aesthetic appeal, excellent mechanical properties, and economic advantages. However, the industry currently predominantly uses post-tensioned prestressed construction technology. This process requires pre-embedding corrugated ducts within the concrete beam. After the concrete reaches its strength, the prestressing strands are threaded, tensioned, and grouted. This process makes it difficult to guarantee 100% compactness of the grout within the prestressing ducts. Incomplete grouting creates a risk of corrosion for the prestressing tendons later, seriously affecting the long-term durability of the structure. Furthermore, to accommodate large-diameter prestressing ducts and anchoring systems at the beam ends, post-tensioned small box girders often require increased web thickness in the beam end region, frequently resulting in variable cross-section structures. This structural treatment not only directly increases the self-weight of the precast components but also makes demolding the core mold inside the box girder extremely difficult, impacting construction efficiency. To address the durability and structural complexity issues associated with post-tensioning, pre-tensioned prestressed technology has become a viable research direction. The pre-tensioning method eliminates the need for pre-installed pipes and grouting by directly tensioning the steel strands on the platform before pouring concrete, thus fundamentally eliminating the risk of corrosion of prestressed tendons.
[0003] However, in the pre-tensioning system, in order to effectively control the principal tensile stress generated by shear force in the web at the beam ends and prevent concrete cracking, it is usually necessary to install zigzag-shaped prestressing tendons in the web. Since the web of the small box girder itself is inclined, the bent steel strands exhibit a complex three-dimensional spatial shape. This places extremely high demands on the design and construction of the auxiliary facilities and fixing platforms required for tensioning, greatly increasing the technical difficulty and making it difficult for the pre-tensioned small box girder structure to be widely promoted and applied in engineering practice.
[0004] Therefore, there is an urgent need for a new small box girder structure scheme that can retain the durability advantages of pre-tensioned construction while avoiding complex zigzag reinforcement, thereby reducing the manufacturing threshold. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention proposes a linear pre-tensioned small box girder with corrugated steel plates embedded in the beam ends and its fabrication method. Corrugated steel plates are embedded in the web near the beam ends of the small box girder to bear shear forces, thus eliminating the need for zigzag prestressing tendons in the web. All prestressing tendons are straight and arranged in the bottom slab, constructed using the pre-tensioning method. This achieves a thin-web structure with a uniform cross-section, reducing self-weight and simplifying construction.
[0006] To achieve the above objectives, the present invention specifically adopts the following solution:
[0007] A linear prestressed small box girder with corrugated steel plates embedded in the beam ends includes a top plate, a web plate, and a bottom plate. The top plate, web plate, and bottom plate are constructed with equal thickness along the entire span. Corrugated steel plates are embedded in a certain section of the web plate near the two beam ends. Multiple bundles of linear prestressed steel strands are arranged in the bottom plate, and no prestressing tendons are arranged in the web plate.
[0008] Furthermore, the surface of the corrugated steel plate is provided with a structure for enhancing the bond with concrete; the structure is a short stud or an opening through which transverse reinforcing bars are inserted.
[0009] Furthermore, the transverse reinforcing bars passing through the holes in the corrugated steel plate are tied and fixed to the stirrups of the web.
[0010] Furthermore, the thickness of the corrugated steel plate is 6-10mm, the wave height is 50-80mm, and the wavelength is 200-300mm.
[0011] Furthermore, the straight steel strand has a debonding section near the beam end; the debonding section is formed by sleeved PVC pipe on the prestressed steel strand.
[0012] Furthermore, the small box girder also includes end diaphragms disposed at the ends of the girder.
[0013] Furthermore, the top plate, web plate, and bottom plate are made of self-compacting high-performance concrete of C60 to C80.
[0014] Correspondingly, a method for manufacturing a straight pre-tensioned small box girder with corrugated steel plates embedded in the beam ends includes the following steps:
[0015] A. Install corrugated steel plates on the precast platform and position them using temporary supports;
[0016] B. Tie the reinforcing cage of the small box girder, insert transverse reinforcing bars into the surface holes of the corrugated steel plate, and tie them to the web stirrups;
[0017] C. Tension the straight prestressed steel strands arranged in the base plate, and insert PVC pipes into the steel strands near the beam end to form the designed debonding length;
[0018] D. Pour the concrete for the small box girder, use high-frequency vibration to ensure compaction, and cure it to the specified age;
[0019] E. Symmetrically release all prestressed steel strands.
[0020] Furthermore, in step E, the prestressed steel strands are symmetrically laid out in the order of first the center and then the two sides.
[0021] Compared with the prior art, the present invention has the following beneficial technical effects:
[0022] This invention creates a robust composite load-bearing structure with the concrete web by creating holes in the surface of an embedded corrugated steel plate and then inserting transverse reinforcing bars. This significantly improves the bond strength and pull-out resistance between the corrugated steel plate and the concrete, effectively transferring and dispersing shear force, ensuring the reliability of their coordinated operation, and avoiding the risks of stress concentration and interface delamination. By employing a pre-tensioning construction process, all prestressing tendons are tensioned in one go before concrete pouring, eliminating the need for pre-reserved ducts and subsequent grouting, thus fundamentally ensuring the durability of the prestressed system. Since the shear force is borne by the corrugated steel plate, no prestressing tendons are needed in the web, allowing the web to be constructed as a thin-walled structure of uniform thickness across the entire span. This design reduces the structural weight, saves concrete materials, and lowers prefabrication costs. Furthermore, during demolding of variable cross-section box girders, the core mold is easily jammed at the expanded section at the beam end, while the internal cavity of a uniform cross-section box girder is unobstructed, reducing demolding difficulty and improving prefabrication efficiency.
[0023] Compared to the traditional pre-tensioning method, which requires spatially arranged polygonal reinforcement in the web, this method places all prestressing tendons in the base slab in a straight line. The tensioning equipment eliminates the need for complex spatial positioning mechanisms, and the platform design is greatly simplified, lowering the technical threshold and equipment investment required for the pre-tensioning process. This invention, through the ingenious combination of "corrugated steel plate shear resistance" and "straight-line pre-tensioning of the base slab," simultaneously improves durability, economy, and construction convenience. Attached Figure Description
[0024] Figure 1 An elevation view of a small box girder according to an embodiment of the invention.
[0025] Figure 2 A cross-sectional view of the web of a small box girder according to an embodiment of the invention.
[0026] Figure 3 This is a plan view of the web of a small box girder according to an embodiment of the invention.
[0027] Figure 4 An elevation view of the prestressed steel reinforcement layout of a small box girder according to an embodiment of the invention.
[0028] Figure 5 This is a cross-sectional view of a small box girder near the beam end in one embodiment of the invention.
[0029] Figure 6 This is a detailed drawing of a corrugated steel plate embedded in a small box girder according to an embodiment of the invention.
[0030] Numbers in the diagram:
[0031] 1. Top plate; 2. End diaphragm; 3. Bottom plate; 4. Web plate; 5. Corrugated steel plate; 6. Straight prestressed steel strand; 7. PVC pipe; 8. Horizontal reinforcement; 9. Holes. Detailed Implementation
[0032] The following detailed description provides specific embodiments to illustrate the present invention. Obviously, the described embodiments are only a portion, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0033] Please see Figures 1 to 5 This embodiment provides a linear pre-tensioned small box girder with corrugated steel plates embedded in the beam ends. The small box girder is a precast concrete component, mainly including a top plate 1, a web plate 4, a bottom plate 3, and end diaphragms 2 set at the beam ends. Among them, the top plate 1, web plate 4, and bottom plate 3 all adopt a structural form with uniform thickness along the entire span, which significantly reduces the difficulty of demolding the core mold and facilitates the standardized production of the structure.
[0034] In the sections with higher shear forces near both ends of the small box girder, corrugated steel plates 5 are embedded in the web 4. These corrugated steel plates 5 serve as the primary shear-resistant members, with the following structural parameters: thickness 6-10mm, wave height 50-80mm, and wavelength 200-300mm. The corrugated steel plates 5 are not arranged along the entire length; they are only installed within a specific length range at the beam ends, and are not present in the web 4 in the mid-span region.
[0035] Please see Figure 5 and Figure 6 To ensure that the corrugated steel plate 5 and the concrete web 4 can work together to withstand shear forces, a bonding-enhancing structure is provided on the surface of the corrugated steel plate 5. Specifically, several holes 9 are made in the corrugated steel plate 5, and transverse reinforcing bars 8 are inserted into these holes 9. These transverse reinforcing bars 8 are tied and fixed to the stirrups of the web 4 itself, thereby forming a strong mechanical interlock and connection after the concrete is poured, effectively preventing the delamination of the corrugated steel plate 5 from the concrete interface.
[0036] Please see Figure 4 All prestressing tendons are straight prestressed steel strands 6, and are all centrally arranged in the base slab 3. No zigzag or curved prestressing tendons are required in the web 4, greatly simplifying the configuration of the prestressing system. The straight prestressed steel strands 6 are all installed using the pre-tensioning method, tensioned on the platform before the beam concrete is poured.
[0037] To optimize stress distribution in the beam end region, a PVC pipe 7 is fitted onto the straight prestressed steel strand 6 near the beam end, thus forming a debonded section of a specific length. By adjusting the position and length of the PVC pipe 7, the range of this debonded section can be controlled to adapt to different stress requirements.
[0038] In a preferred embodiment, the top plate 1, web plate 4 and bottom plate 3 constituting the small box girder are all cast from self-compacting high-performance concrete with a strength grade of C60 to C80, which can ensure the compactness and overall quality of the thin-walled component concrete.
[0039] The following details the manufacturing method of this small box girder:
[0040] First, the corrugated steel plate 5 is precisely installed and positioned on the prefabricated pedestal using temporary supports.
[0041] Next, the steel reinforcement cage for the small box girder is tied. During this process, the transverse steel bars 8 are passed through the pre-set holes 9 on the corrugated steel plate 5 and reliably tied to the stirrups of the web plate 4 to form an integral steel reinforcement skeleton.
[0042] Then, prestressing tensioning is performed. All straight prestressed steel strands 6 arranged at the base plate position are tensioned to the design control stress. At the same time, PVC pipes 7 are inserted into the steel strands near the beam ends at the design positions to form the preset debonding length.
[0043] After tensioning is completed, pour the concrete for the small box girder. High-frequency vibrators should be used to ensure the concrete, especially around the corrugated steel plate 5, is fully compacted. After pouring, the component should be cured according to specifications until it reaches the designed age and strength.
[0044] Finally, prestressing is released. Following a symmetrical sequence, starting with the center and then the sides, all prestressed steel strands 6 are slowly released to effectively transfer the prestress to the concrete beam and avoid creating an unfavorable initial stress state within the beam.
[0045] This invention combines "corrugated steel plate shear resistance" with "pre-tensioning of the bottom plate in a straight line" to achieve a small box girder with a constant cross-section and thin web, while ensuring structural performance. This reduces the self-weight and simplifies the pre-tensioning construction process.
Claims
1. A linear pre-tensioned small box girder with corrugated steel plates embedded at the beam ends, characterized in that, It includes a top plate (1), a web plate (4) and a bottom plate (3), wherein the top plate (1), the web plate (4) and the bottom plate (3) are constructed with equal thickness along the entire span; the web plate (4) has corrugated steel plates (5) embedded in a certain section near the two beam ends; the bottom plate (3) is arranged with multiple bundles of straight prestressed steel strands (6), and the web plate (4) is not arranged with prestressed tendons.
2. The straight pre-tensioned small box girder with corrugated steel plates embedded at the beam ends as described in claim 1, characterized in that, The surface of the corrugated steel plate (5) is provided with a structure for enhancing the bond with concrete; the structure is a short stud or an opening (9) through which a transverse steel bar (8) passes.
3. The straight pre-tensioned small box girder with corrugated steel plates embedded at the beam ends as described in claim 2, characterized in that, The transverse steel bars (8) passing through the holes (9) of the corrugated steel plate (5) are tied and fixed to the stirrups of the web plate (4).
4. The straight pre-tensioned small box girder with corrugated steel plates embedded at the beam ends as described in claim 2, characterized in that, The corrugated steel plate (5) has a thickness of 6-10 mm, a wave height of 50-80 mm, and a wavelength of 200-300 mm.
5. The straight pre-tensioned small box girder with corrugated steel plates embedded at the beam ends as described in claim 2, characterized in that, The straight steel strand (6) has a debonding section near the beam end; the debonding section is formed by sleeved PVC pipe (7) on the prestressed steel strand (6).
6. The straight pre-tensioned small box girder with corrugated steel plates embedded at the beam ends as described in claim 2, characterized in that, The small box girder also includes an end diaphragm (2) disposed at the end of the girder.
7. The straight pre-tensioned small box girder with corrugated steel plates embedded at the beam ends as described in claim 2, characterized in that, The top plate (1), web plate (4) and bottom plate (3) are made of self-compacting high-performance concrete of C60 to C80.
8. A method for manufacturing a straight pre-tensioned small box girder with corrugated steel plates embedded at the beam ends, characterized in that, Includes the following steps: A. Install corrugated steel plates (5) on the precast platform and position them using temporary supports; B. Tie the steel cage of the small box girder, and insert transverse steel bars (8) into the surface holes (9) of the corrugated steel plate (5), and tie them to the web stirrups; C. Tension the straight prestressed steel strands (6) arranged in the base plate (3), and insert PVC pipes (7) into the steel strands near the beam end to form the designed debonding length; D. Pour the concrete for the small box girder, use high-frequency vibration to ensure compaction, and cure it to the specified age; E. Symmetrically release all prestressed steel strands (6).
9. The manufacturing method according to claim 8, characterized in that, In step E, the prestressed steel strands (6) are symmetrically laid out in the order of first the center and then the two sides.