A new type of external prestressed component of prestressed box beam

Abstract

The present invention provides a novel prestressed box girder external prestressing assembly, including external cables and an anchoring system, characterized in that the external cables include a main sleeve, a plurality of small sleeves arranged in the main sleeve, a plurality of steel strands arranged in the small sleeves and twisted with each other, cement slurry filled between the main sleeve and the small sleeves, and grease filled between the small sleeves and the steel strands. The prestressed box girder external prestressing assembly of the present invention can achieve multiple corrosion protection of the external steel strands and facilitate the replacement of cables at a later stage, and has good promotion and practical value.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction, and in particular relates to a novel external prestressed component of a prestressed box girder. Background Art

[0002] With the continuous improvement of bridge construction technology, the use of external prestressed tendons in bridges has been increasingly used in the construction process of modern bridges. External prestressed structures are flexible in layout, safe and reliable, and easy to construct and replace. They can greatly and effectively improve the bearing capacity of bridges, especially when the structure can work normally, and can adjust and replace cables, which is an advantage that other reinforcement methods cannot match. However, the external prestressed tendons are not wrapped in concrete and are extremely susceptible to adverse environmental influences, especially fire and corrosive chemicals. When the bridge is in an extremely corrosive environment, the corrosion protection of the external tendon strands will be the top priority of the external tendon design, which will be directly related to the service life of the external tendon or bridge structure. Summary of the invention

[0003] In view of the above problems, the present invention provides a novel external prestressed assembly of a prestressed box girder, which can achieve multiple corrosion protection of the outer stranded steel wires and facilitate the later replacement of the wires.

[0004] The present invention is achieved through the following technical solutions.

[0005] A novel prestressed box girder external prestressed component includes an external cable and an anchoring system, and is characterized in that the external cable includes a main casing, a plurality of small casings arranged in the main casing, a plurality of steel strands arranged in the small casings and twisted with each other, cement slurry filled between the main casing and the small casings, and grease filled between the small casings and the steel strands.

[0006] As a specific technical solution, the anchoring system includes a protective cover, an anchor plate, an anchor plate pad, an embedded pipe, a connecting tube connected in sequence, a spiral rib arranged on the outside of the anchor plate pad, and a clip arranged in the reserved steel strand passing hole of the anchor plate.

[0007] As a specific technical solution, a wax injection hole is reserved in the anchor plate pad, and an exhaust hole is provided on the embedded pipe.

[0008] As a specific technical solution, the connecting tube is provided with an exhaust hole at the upper part and a grouting hole at the lower part.

[0009] As a specific technical solution, the protective cover and the anchor plate are connected by bolts.

[0010] As a specific technical solution, a sealing device is provided between the embedded pipe and the connecting tube.

[0011] As a specific technical solution, the main sleeve is connected and fixed to the connecting tube through a clamp.

[0012] As a specific technical solution, a sealing tape is provided at the connection seam between the connecting tube and the main sleeve.

[0013] As a specific technical solution, the main casing is a HDPE pipe with a diameter of 80 to 150 mm.

[0014] As a specific technical solution, the small sleeve is a PE tube.

[0015] The beneficial effects of the present invention are:

[0016] 1. The external prestressed cable of the present invention adopts unbonded ordinary steel strands, and can achieve quadruple corrosion protection at the same time, and has less cost investment than unbonded epoxy steel strands and unbonded galvanized steel strands.

[0017] 2. The present invention separates the anchor end and the free end. The anchor end is shorter and is protected by wax injection, while the free end of the cable is longer and is protected by grout injection. The most economical anti-corrosion measures are adopted for different parts, and the purpose of replacing a single strand can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the present invention;

[0019] Figure 2 is a cross-sectional view of an external cable in the present invention;

[0020] Figure 3 It is a schematic diagram of the present invention after installation;

[0021] Figure 4 It is a schematic diagram of the combination of small casing, steel strand and grease in the outer cable;

[0022] The meanings of the symbols in the above figure are:

[0023] 1-external cable, 101-main casing, 102-small casing, 103-steel strand, 104-cement slurry, 105-grease;

[0024] 2-anchoring system, 201-protection cover, 202-anchor plate, 203-anchor plate pad, 204-buried pipe, 205-connecting tube, 2051-vent hole, 2052-grouting hole, 206 spiral reinforcement, 207-clip sheet, 208-sealing device;

[0025] 3-Holding hoop;

[0026] 4- Sealing tape;

[0027] 5-Oily wax;

[0028] 6- cement slurry;

[0029] 7- Steering gear. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc., are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Example

[0032] A new type of prestressed box girder external prestressing component, please refer to Figures 1 to 4 , including an extracorporeal cable 1 and an anchoring system 2; wherein the extracorporeal cable 1 includes a main casing 101, a plurality of small casings 102 arranged in the main casing 101, a plurality of steel strands 103 arranged in the small casings 102 and twisted with each other, cement slurry 104 filled between the main casing 101 and the small casings 102, and grease 105 filled between the small casings 102 and the steel strands 103; in the above structure, the grease 105, the small casing 102, the cement slurry 104, and the main casing 101 form a quadruple anti-corrosion structure for the steel strands 103; the steel strands 103, the grease 105, and the small casing 102 form non-bonded prestressed steel strands.

[0033] Further, in a preferred embodiment, see Figure 1 , Figure 3 The anchoring system 2 includes a protective cover 201, an anchor plate 202, an anchor plate pad 203, an embedded pipe 204, and a connecting tube 205 connected in sequence, a spiral rib 206 arranged on the outside of the anchor plate pad 203, and a clip 207 arranged in the reserved steel strand passing hole of the anchor plate 202; wherein, the anchor plate 202 has reserved steel strand passing holes, and the number of holes is consistent with the designed number of steel bundles; the clip 207 is used to anchor the steel strand during the steel strand tensioning process; the embedded pipe 204 is embedded in the concrete at the anchor end of the box girder, and forms a transition section channel with the connecting tube 205.

[0034] Further, in a preferred embodiment, see Figure 1 , Figure 3A wax injection hole 2031 is reserved in the anchor plate pad 203 for wax injection and corrosion protection at the anchor end after tensioning is completed; an exhaust hole 2051 is provided on the embedded pipe 204 for exhaust during the wax injection process of the anchor section.

[0035] Further, in a preferred embodiment, see Figure 1 , Figure 3 The upper part of the connecting tube 205 is provided with an exhaust hole 2051 for exhausting the wax injection process of the anchoring section; the lower part of the connecting tube 205 is provided with a grouting hole 2052 for injecting cement grout after the tensioning is completed.

[0036] Further, in a preferred embodiment, see Figure 1 , Figure 3 The protective cover 201 and the anchor plate 202 are connected by bolts.

[0037] Further, in a preferred embodiment, see Figure 3 The external prestressed assembly of the prestressed box girder of the present invention also includes a deflector 7 and a shock absorber; the deflector 7 is of a cluster type and is pre-buried in the concrete connected to the box body for external beam deflection; the shock absorber is used to reduce the vibration of the free end of the external cable during the later bridge operation process.

[0038] Further, in a preferred embodiment, see Figure 1 , Figure 3 A sealing device 208 is provided between the embedded pipe 204 and the connecting tube 205 to separate the wax injection anti-corrosion of the anchoring end and the grouting anti-corrosion of the free end.

[0039] Further, in a preferred embodiment, see Figure 1 , Figure 3 The main sleeve 101 is connected and fixed to the connecting tube 205 through the clamp 3.

[0040] Further, in a preferred embodiment, see Figure 1 , Figure 3 A sealing tape 4 is provided at the connection seam between the connecting tube 205 and the main sleeve 101.

[0041] Further, in a preferred embodiment, the main casing 101 is a HDPE pipe with a diameter of 80 to 150 mm.

[0042] Furthermore, in a preferred embodiment, the small casing 102 is a PE tube.

[0043] The installation construction method of the present invention is as follows:

[0044] 1) HDPE pipe welding and installation

[0045] Welding: HDPE pipe welding adopts hot melt tool butt welding connection. Before welding HDPE pipe, place the pipe in the clamping device and clamp it, and use parallel motorized rotary cutter to flatten the welded end faces of the two pipes under pressure. And ensure that the two end faces meet the flatness requirements when they contact each other.

[0046] Installation: Before installing the HDPE pipe, clean up the debris inside the steering gear, and then pass the HDPE pipe through the steering gear.

[0047] 2) Unbonded prestressed steel strand bundle

[0048] Cutting of unbonded prestressed steel strands: Cutting of steel strands should be carried out according to the design drawings. The cutting length of steel strands should take into account the tensioning working length at both ends. The steel strands are cut with a grinding wheel cutter.

[0049] Unbonded prestressed steel strand bundle

[0050] a) Number the cut steel strands and straighten them one by one to prevent entanglement;

[0051] b) The straightened steel strands are bundled with thin iron wires every 1 m;

[0052] c) Use a bundle threading machine to clean the pipeline before bundling to ensure that the pipeline is unobstructed and free of water or other debris;

[0053] d) The steel strands are matched with a bundle threading machine;

[0054] e) When threading the bundle, tie one end of the prestressed bundle with tape to facilitate threading and avoid scratching the pipe during threading.

[0055] f) When threading the bundle, it should be dragged back and forth without twisting to ensure that the steel strands are straight.

[0056] g) After bundling, ensure that the working length of the steel strands at both ends is not less than the design value.

[0057] 3) Installation of tensioning equipment and tensioning of steel strands

[0058] a) Installation of tensioning equipment

[0059] The installation order of the tensioning equipment from inside to outside is: anchor plate, working anchor, working clip, limit plate, jack, tool anchor, tool clip. After the bundle is threaded, clean the anchor plate first, install the working anchor in the groove of the anchor plate, and keep the working anchor and the anchor plate vertically and tightly together. Push the clip along the steel strand into the tapered hole of the working anchor until it cannot be pushed by hand, and then tamp it with a steel pipe. The clip should be installed flush. Install the jack and connect it to the oil pump, and install the tool anchor and tool anchor clip.

[0060] b) Steel strand tensioning

[0061] The steel strand tensioning adopts symmetrical tensioning at both ends at the same time. After the single box girder of the main bridge is fully closed, the external strand tensioning construction will begin. The tensioning sequence of the steel strand should be tensioning the long strand first and then the short strand, and the tensioning should be symmetrical at both ends.

[0062] Prestressing is carried out in two stages. The first stage is prestressing, and the tensioning force is 10% of the designed prestressing. After the prestressing is completed, the pipeline is grouting, and the second stage of prestressing is carried out after the cement slurry reaches the designed strength. The second stage of tensioning is carried out in three levels: 15%, 30%, and 100%. After each level of tensioning is completed, the load must be held for 5 minutes and tensioning records must be kept. The tensioning process adopts a dual standard control of tensioning force as the main and elongation as the auxiliary. During the tensioning process, the deviation between the actual elongation and the theoretical elongation should not be greater than ±6%. When tensioning to the design value, hold the load for 5 minutes. If the actual elongation value is within the allowable deviation range, slowly return the oil, anchor, and withdraw the top.

[0063] 4) Grouting and installation of protective cover

[0064] a) Install temporary tool protection cover

[0065] After the tensioning is completed, a portable grinding wheel cutter is used to cut the excess steel strands outside the anchor plate, and the reserved length is controlled according to the design drawings. Grease the inner wall of the tool protection cover with a layer of grease, install a temporary protection cover, remove it after the wax is injected and solidified, and install a permanent protection cover.

[0066] b) Grouting

[0067] Use an air compressor to blow away the debris in the hole. In the cement slurry, add water and admixtures first and then cement in the grout mixer. Grouting is done from bottom to top. Start the grouting pump. When the slurry output by the grouting pump reaches the required consistency, grouting begins. During the grouting process, the grouting pump keeps working continuously.

[0068] c) Install permanent protective cover

[0069] After the hole grouting is completed and reaches the required strength, the second stage of tensioning is carried out. After the tensioning is completed, the prestressed anchor head is treated with anti-corrosion treatment, the steel strand is re-applied with grease for anti-corrosion, wax is injected, and a permanent protective cover is installed.

[0070] d) Oil-injected wax

[0071] The oily wax is injected in two parts. One part is used between the anchor plate and the sealing plate of the anchor system, and the other part is used inside the protective cover. The oily wax is applied using a hot melt wax injection machine.

[0072] 5) Shock absorber installation

[0073] The external prestressed system vibration damper is mainly used to fix the external beam and reduce the vibration of the external beam under the action of dynamic load. The vibration damper is connected to the bridge body as a whole through embedded bolts. The external beam is tightened by tightening the nut.

Claims

1. A novel prestressed box girder external prestressing assembly, comprising an external cable (1) and an anchoring system (2), characterized in that: The external cable (1) comprises a main casing (101), a plurality of small casings (102) arranged in the main casing (101), a plurality of steel strands (103) arranged in the small casings (102) and twisted with each other, cement slurry (104) filled between the main casing (101) and the small casings (102), and grease (105) filled between the small casings (102) and the steel strands (103); The anchoring system (2) comprises a protective cover (201), an anchor plate (202), an anchor plate pad (203), a pre-buried pipe (204), and a connecting tube (205) connected in sequence, a spiral rib (206) arranged outside the anchor plate pad (203), and a clip (207) arranged in a hole reserved for passing a steel strand in the anchor plate (202); a wax injection hole (2031) is reserved in the anchor plate pad (203), and an exhaust hole (2051) is arranged on the pre-buried pipe (204); an exhaust hole (2051) is arranged on the upper part of the connecting tube (205), and a grouting hole (2052) is arranged on the lower part; and a sealing device (208) for isolating the wax injection anti-corrosion of the anchor end and the grouting anti-corrosion of the free end is arranged between the pre-buried pipe (204) and the connecting tube (205).

2. A novel prestressed box girder external prestressed component as claimed in claim 1, characterized in that The protective cover (201) and the anchor plate (202) are connected by bolts.

3. A novel prestressed box girder external prestressed component as claimed in claim 1, characterized in that The main sleeve (101) is connected and fixed to the connecting tube (205) via a clamp (3).

4. A novel prestressed box girder external prestressed component as claimed in claim 1, characterized in that A sealing tape (4) is provided at the connection seam between the connecting tube (205) and the main sleeve (101).

5. A novel prestressed box girder external prestressed component as claimed in claim 1, characterized in that The main casing (101) is a HDPE pipe with a diameter of 80 to 150 mm.

6. A novel prestressed box girder external prestressed component as claimed in any one of claims 1 to 5, characterized in that The small casing (102) is a PE tube.

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