Small-radius curve conjoined U-shaped beam for magnetic suspension and construction method of small-radius curve conjoined U-shaped beam

Abstract

The small-radius curve conjoined U-shaped beam comprises a beam body and a prestressing tendon arranged in the beam body, the beam body comprises a bottom plate, a middle web plate and side web plates, the middle web plate is arranged in the middle of the bottom plate, and the side web plates are arranged on the two transverse sides of the bottom plate. The prestressing tendons comprise top plate tendons, web plate tendons and bottom plate tendons, the top plate tendons are located in the upper flanges of the side web plates and the middle web plates, the web plate tendons are located in the side web plates, and the bottom plate tendons are located in the bottom plate. The invention further provides a construction method of the small-radius curve conjoined U-shaped beam. According to the small-radius curve conjoined U-shaped beam, the number and indexes of the adopted prestressing tendons are greatly reduced, the prestress arrangement is reasonable, meanwhile, a transverse prestress steel cable does not need to be arranged, the characteristic that loads are approximately evenly distributed on a magnetic suspension line is attached, the overall dead weight is small, the construction period is short, and the engineering cost is low.

Description

Technical Field

[0001] The invention belongs to the field of magnetic levitation, and in particular relates to a magnetic levitation beam and a construction method thereof. Background Art

[0002] With the development of bridge construction, more and more elevated track forms have emerged. The structural forms of conventional elevated bridges mainly include box beams, T beams, plate beams, etc.

[0003] Due to the obvious advantages of U-beams in terms of aesthetics, noise reduction, and low building height, they have been increasingly widely used in urban rail transit projects (such as light rail and maglev). When U-beams are used in the field of maglev, two parallel U-beams are usually set up to meet the needs of up and down lines. Two parallel U-beams usually have the problem of too many prestressed beams, which will increase the construction steps and increase the project cost. In addition, when U-beams are used in the field of maglev, they are restricted by the complex terrain and road conditions of the city. In order to give full play to the advantages of the curve passing and climbing ability of maglev, small radius curves need to be set up to pass through certain special sections, and the dynamic response problem of the maglev vehicle-track system is significant. In addition, the radial force caused by prestressed tensioning will cause additional torque and bending moment in the small radius curve beam. The degree of torque and bending moment is affected by factors such as the number, position, layout shape and tensioning stress of the prestressed beams, which will lead to bridge diseases during the maglev operation stage. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a small-radius curved connected U-shaped beam for magnetic levitation and a construction method thereof, which has simple construction, low engineering cost and reasonable prestressed bundle arrangement.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is: A small-radius curved connected U-shaped beam for magnetic levitation, comprising a beam body and a prestressed beam arranged in the beam body, the beam body comprising a bottom plate, a middle web plate and side web plates, the middle web plate being arranged in the middle of the bottom plate, the side web plates being arranged on both lateral sides of the bottom plate, the prestressed beam comprising a top plate beam, a web plate beam and a bottom plate beam, the top plate beam being located in the upper flanges of the side web plates and the middle web plates, the web plate beam being located in the side web plates, and the bottom plate beam being located in the bottom plate.

[0006] In the above-mentioned small-radius curved connected U-shaped beam, preferably, the top plate bundle is a top plate prestressed tendon, and a plurality of the top plate prestressed tendons are arranged in parallel in the upper flanges of the side webs and the middle webs.

[0007] In the above-mentioned small-radius curved connected U-shaped beam, preferably, the bottom plate bundle includes edge prestressed tendons arranged on both sides of the bottom plate and middle prestressed tendons arranged in the middle of the bottom, the edge prestressed tendons are arranged close to the side webs, and the middle prestressed tendons are located below the middle webs, and multiple edge prestressed tendons and multiple middle prestressed tendons are arranged in parallel.

[0008] In the above-mentioned small-radius curved connected U-shaped beam, preferably, the number of the middle prestressed tendons is greater than the number of the edge prestressed tendons.

[0009] In the above-mentioned small-radius curved connected U-shaped beam, preferably, the web beam is a web prestressed tendon arranged in a broken line shape, with a high point and a low point, the high point is connected to the top plate beam, and the low point is connected to the edge prestressed tendon.

[0010] In the above-mentioned small radius curved connected U-shaped beam, preferably, the arrangement positions of the top plate bundle, the web plate bundle and the bottom plate bundle are biased towards the outside of the small radius curved connected U-shaped beam, and the central symmetry lines of the top plate bundle, the web plate bundle and the bottom plate bundle are located outside the vertical center line of the middle web, and the above-mentioned outside refers to the side of the small radius curved connected U-shaped beam away from its center.

[0011] In the present invention, our research shows that the dynamic response problem of the maglev vehicle-track system on a small radius curve is significant, and when the prestressed tensioning method of the traditional U-beam is used for a small radius curve connected U-beam, there will be additional torque and bending moment. The present invention proposes a small radius curve connected U-beam, and optimizes the arrangement of the prestressed tendons, which can effectively control the bending and torsional deformation and vibration response increment of the entire bridge. By making the number of middle prestressed tendons greater than the number of edge prestressed tendons, the large number of middle prestressed tendons can weaken the web overload effect, overcome the problem that the lateral component force generated when the longitudinal tendons are tensioned in the small radius curve connected U-beam is easy to cause cracks in the web concrete, and this arrangement is more suitable for small radius curve connected U-beam. By making the arrangement position of the top plate beam, the web beam and the bottom plate beam biased to the outside of the small radius curve connected U-beam, it can prevent the outside of the small radius curve connected U-beam from being excessively pulled and cracked or damaged, which helps to balance the torque and enhance the torsional performance of the small radius curve connected U-beam. In addition, compared with the traditional U-shaped beam, the appropriately thickened web of the present invention can meet the requirements of flat bending and anchoring of the web bundle, and disperse the web bundle as much as possible, leaving enough clear spacing to prevent concrete from being crushed.

[0012] In the above-mentioned small radius curved connected U-shaped beam, preferably, the beam body is integrally formed by high-performance concrete, the number of spans × span of each unit of the small radius curved connected U-shaped beam is (2-4) × 25m, the curve radius R (inner curve radius R) is not less than 75m, the top plate bundle, the web bundle and the bottom plate bundle are all made of low relaxation steel strands, and the index of the low relaxation steel strand is 21.4kg / m 3 The top plate beam adopts 7 beams 9-φ s 15.2mm low relaxation steel strand, the web beam uses 6 bundles of 12-φ s 15.2mm low relaxation steel strand, the bottom plate bundle uses 15 bundles of 12-φ s 15.2mm low relaxation steel strand.

[0013] The small radius curved U-shaped beam of the present invention is considered as a fully prestressed component, and tensile stress is not allowed. The physical and chemical properties of the material will directly affect the performance of the U-shaped beam structure. Considering the bearing capacity and rigidity of the bridge, the present invention adopts high-performance concrete to form the beam in one piece. The high-performance concrete adopts C50 concrete, and the beam concrete is mixed with polypropylene fiber, with a mixing amount of 0.9kg / m 3 The main beam is made of high-performance concrete, and the beam concrete is mixed with polypropylene fiber, which significantly improves the performance and safety of the bridge. It can be used in small radius curve sections, and also increases the life and reliability of the bridge.

[0014] The steel strands of the combined U-shaped beam of the present invention are φ s 15.2mm low relaxation steel strand, tensile strength standard value f pk =1860MPa, elastic modulus E P =1.95×10 5 MPa. For the case where the span number × span diameter of each U-shaped beam with a small radius curve is (2-4) × 25m and the curve radius R is not less than 75m, a total of 28 bundles of low relaxation steel strands are used, and the index of low relaxation steel strands is 21.4kg / m 3 Compared with the conventional U-beam structure, the number and index of low relaxation steel strands are greatly reduced. Among them, the top plate beam adopts 7 beams of 9-φ s 15.2mm low relaxation steel strand, web beam using 6 bundles of 12-φ s 15.2mm low relaxation steel strand, bottom plate bundle uses 15 bundles of 12-φ s 15.2mm low-relaxation steel strand. The layout principle of low-relaxation steel strand is to avoid embedded parts such as supports and anti-falling beam blocks.

[0015] In the above-mentioned small-radius curved connected U-shaped beam, preferably, a rail support platform is provided on the bottom plate between the side web plate and the middle web plate, and a drainage hole and an emergency drainage port are respectively provided on both sides of the rail support platform.

[0016] In the above-mentioned small-radius curved connected U-shaped beam, preferably, a waterproof layer is provided on the bottom plate, a waterproof layer extending from the bottom plate to the side of the rail support platform is provided at the junction of the bottom plate and the rail support platform, a concrete slope layer is provided below the waterproof layer, and the waterproof layer includes a sealing paint layer, a waterproof primer layer and a waterproof topcoat layer from bottom to top; the total thickness of the waterproof layer is not less than 600μm and not more than 800μm, the dry film thickness of the waterproof primer layer is not less than 400μm, and the dry film thickness of the waterproof topcoat layer is not less than 200μm.

[0017] In the present invention, the waterproof layer is composed of a sealing paint layer, a waterproof primer layer, and a waterproof topcoat layer. The sealing paint layer is formed by a sealing paint, the waterproof primer layer is formed by a thin-coating polyurethane waterproof primer (PPU-M1), and the waterproof topcoat layer is formed by a thin-coating polyurethane waterproof topcoat (PPU-M2). The total thickness of the waterproof layer should not be less than 600μm, and should not be greater than 800μm. The dry film thickness of the primer layer should not be less than 400μm, and the dry film thickness of the topcoat layer should not be less than 200μm. The construction process is: water collection slope setting → base surface treatment → sealing paint layer construction → primer (PPU-M1) construction → topcoat (PPU-M2) construction. In addition to setting a 2% transverse drainage slope for the beam body, when centralized drainage is required, the beam body located on the flat slope of the line should also be set with a longitudinal water collection slope of not less than 2‰ according to the position of the centralized drainage pipe. The centralized drainage pipe is set on the downslope side of the beam, and each U-beam has a total of 8 centralized drainage pipes. When the U-beam is located on the longitudinal slope of the line, the longitudinal slope of the line can be used for drainage. The centralized drainage pipe is set at one end of the downslope side of the beam. There are 4 centralized drainage pipes for each U-beam. The water collection slope adopts structural slope finding and is set when the beam is made. After slope finding, the thickness of the bottom plate shall not be less than the original design structure size. At the same time, 4 emergency drainage pipes are added near the centralized drainage pipe for emergency use.

[0018] The present invention can increase the height of the rail support platform, and the height from the rail surface to the bottom surface of the rail support platform is controlled to be above 1.1m, ensuring that the position of the train pedal is higher than the top of the upper flange of the small-radius curve connected U-shaped beam.

[0019] As a general technical concept, the present invention also provides a construction method for the above-mentioned small-radius curved connected U-shaped beam. At the construction site of the small-radius curved connected U-shaped beam, the pre-tensioning method is adopted, and a tensioning process of single-beam initial adjustment, overall initial tensioning, and single-beam final tensioning is adopted. The over-tensioning coefficient is adjusted in combination with the arch value of the small-radius curved connected U-shaped beam after tensioning, and the tensioning force value of a single prestressed tendon is individually controlled.

[0020] The construction method of the present invention adopts the pre-tensioning method, the tensioning process of "single-beam initial adjustment, overall initial tensioning, and single-beam final tensioning", the "double control method" control and intelligent tensioning system ensure the synchronous tensioning of the prestressed tendons, and the super-tensioning coefficient is adjusted by combining the upper arch value of the small-radius curve connected U-shaped beam after tensioning, so as to effectively control the tensioning force value of a single prestressed tendon. Through a reasonable tensioning sequence of prestressed steel strands, the loss of prestress is reduced to a minimum. The prestressed tendons and pipelines are adjusted accordingly according to the slope based on the symmetry center line of the beam body as the reference line. When adjusting the prestressed tendons and pipelines at the beam end cut corners, first ensure that the dimensions of each bending starting point and anchor point to the beam end boundary meet the design dimensions of the prestressed tendons, and then make corresponding adjustments to the prestressed tendons and the horizontal sections of the pipelines. The beam body steel bars are tied as a whole, first the bottom plate and web steel bars are tied, and then the top plate steel bars are tied. When the beam body steel bars collide with the prestressed tendons, the beam body steel bars can be appropriately moved or bent. The minimum protective layer of the beam reinforcement is 35mm, and the tail section of the binding wire should not extend into the protective layer. Corresponding annular reinforcements are added at all reserved holes in the beam body, and the reinforcements at the drainage holes can be appropriately moved, and spiral reinforcements and inclined well-shaped reinforcements are added for reinforcement.

[0021] For traditional large U-shaped beams, in order to ensure structural safety and stability, the number and index of prestressed beams are relatively high. Beams with larger transverse widths generally require additional transverse prestressed beams, which increases costs and construction periods. The suspension force actively controlled by the maglev line is obviously different from the wheel-rail contact force, which makes the dynamic interaction mechanism and law between the maglev vehicle and the U-shaped beam quite different from the wheel-rail system. The present invention proposes a new connected U-shaped beam, and optimizes the layout and tensioning of prestressed beams to fit the characteristics of the approximately uniformly distributed load of the maglev vehicle suspension state. It does not need to set transverse prestressed beams and can be applied to small radius curve lines.

[0022] The prestressed arrangement method for the connected U-beam proposed in the present invention has significantly fewer or lower numbers and indicators of prestressed bundles than traditional large U-beams, which can reduce construction steps and lower project costs. Moreover, the optimized prestressed arrangement method can solve the significant problem of the dynamic response of the maglev vehicle-track system, avoid the occurrence of additional torque and bending moment, and reduce bridge diseases. The present invention optimizes the arrangement of prestressed bundles, matches the steel strands with the connected U-beams, greatly reduces the number and indicators of the steel strands used, and reduces the cost; at the same time, excessive prestress will have a significant impact on the vehicle-bridge coupled vibration of the maglev line. The present invention effectively reduces the vertical vibration response increment of the vehicle-bridge coupled maglev line, including the acceleration of the bridge and the displacement of the maglev vehicle suspension frame, by independently controlling the final tensioning force value of each prestressed tendon; moreover, cracks in the previous U-beams usually occur at the junction of the bottom plate and the web, and this transition area Stress concentration is prone to occur, and the bridge is subjected to bending and torsion. The connected U-shaped beam of the present invention arranges prestressed tendons on both sides and the middle of the bottom plate below the web, and the middle prestressed tendons are more than the prestressed tendons on both sides, which effectively improves the durability of the bridge. In addition, the present invention prevents the outer side of the connected U-shaped beam with a small radius curve from being excessively pulled and cracked or damaged by balancing the torque and enhancing the torsional performance of the connected U-shaped beam with a small radius curve.

[0023] Compared with the prior art, the advantages of the present invention are: 1. The small radius curve connected U-shaped beam of the present invention has a simple structure, smooth curves, and good overall visual effect; the side webs on both sides of the U-shaped beam section can play a role similar to a sound barrier, which can reduce the impact of vehicle noise on the surrounding environment to a certain extent; the side webs on both sides of the U-shaped beam can prevent derailed vehicles from overturning and falling, providing a reliable guarantee for driving safety; the width and height of the U-shaped beam are small, ensuring the clearance under the bridge, and the overall deadweight is small; adding a middle web in the middle of the U-shaped beam has better overall force performance and is suitable for a larger span. Overall, the force of the U-shaped beam structure meets the requirements of the design specifications and has good mechanical properties and landscape effects.

[0024] 2. The number and index of prestressed bundles used in the small-radius curved connected U-shaped beam of the present invention are greatly reduced, the prestressing arrangement is reasonable, and there is no need to set up transverse prestressed steel cables. It fits the characteristics of the nearly uniformly distributed load of the magnetic levitation line, has a small overall dead weight, a short construction period, and a low project cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a three-dimensional diagram of the small-radius curved connected U-shaped beam of the present invention.

[0027] Figure 2 It is a structural schematic diagram of the small radius curved connected U-shaped beam of the present invention.

[0028] Figure 3 This is a elevational layout diagram of the prestressed tendons of the small-radius curved connected U-shaped beam of the present invention (pre-tensioning method).

[0029] Figure 4 This is a cross-sectional arrangement diagram of the prestressed tendons of the small-radius curved connected U-shaped beam of the present invention (pre-tensioning method).

[0030] Figure 5 It is a schematic diagram of the waterproof layer system of the small radius curved connected U-shaped beam of the present invention.

[0031] Figure 6 It is a schematic diagram of the waterproof layer structure of the small radius curved connected U-shaped beam of the present invention.

[0032] Legend 1. Side web; 2. Middle web; 3. Bottom plate; 4. Upper flange; 6. Track support; 7. Top plate bundle; 8. Web bundle; 9. Bottom plate bundle; 10. Web steel bundle variation curve; 12. Waterproof layer; 121. Waterproof topcoat layer; 122. Waterproof primer layer; 123. Sealing paint layer; 13. Drain hole; 14. Emergency drain outlet; 15. Concrete slope layer. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0034] It should be noted that when an element is described as being "fixed, fixed, connected or connected to" another element, it can be directly fixed, fixed, connected or connected to the other element, or it can be indirectly fixed, fixed, connected or connected to the other element through other intermediate connectors.

[0035] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0036] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0037] Example: like Figure 1-Figure 4 As shown, the small-radius curved connected U-shaped beam for magnetic levitation in this embodiment includes a beam body and a prestressed beam arranged in the beam body. The beam body includes a bottom plate 3, a middle web 2 and a side web 1. The middle web 2 is arranged in the middle of the bottom plate 3, and the side web 1 is arranged on both lateral sides of the bottom plate 3. The prestressed beam includes a top plate beam 7, a web beam 8 and a bottom plate beam 9. The top plate beam 7 is located in the upper flange 4 of the side web 1 and the middle web 2, the web beam 8 is located in the side web 1, and the bottom plate beam 9 is located in the bottom plate 3.

[0038] Specifically, in this embodiment, the top plate bundle 7 is a top plate prestressed tendon, and a plurality of top plate prestressed tendons are arranged in parallel in the upper flanges 4 of the side webs 1 and the middle webs 2. The bottom plate bundle 9 includes edge prestressed tendons arranged on both sides of the bottom plate 3 and middle prestressed tendons arranged in the middle of the bottom. The edge prestressed tendons are arranged close to the side webs 1, and the middle prestressed tendons are located below the middle webs 2. The edge prestressed tendons and the middle prestressed tendons are both arranged in parallel in plurality. The number of middle prestressed tendons is greater than the number of edge prestressed tendons. The web bundle 8 is a web prestressed tendon arranged in a broken line shape, and is provided with a high point and a low point. The high point is connected to the top plate bundle 7, and the low point is connected to the edge prestressed tendons. For details, please refer to Figure 3 Web steel tendon variation curve 10.

[0039] More specifically, Figure 4 As shown, in this embodiment, the span number × span diameter of each small radius curved U-shaped beam is (2-4) × 25m, the inner curve radius R is 100m, and a total of 28 low-relaxation steel strands are used. The top plate strand 7, the web plate strand 8 and the bottom plate strand 9 all use low-relaxation steel strands, and the index of the low-relaxation steel strand is 21.4kg / m 3 , the top plate beam 7 adopts 7 beams 9-φ s 15.2mm low relaxation steel strand, web bundle 8 uses 6 bundles of 12-φ s 15.2mm low relaxation steel strand, bottom plate bundle 9 uses 15 bundles of 12-φ s 15.2mm low relaxation steel strand.

[0040] In this embodiment, the beam body is formed in one piece using high-performance concrete. The high-performance concrete uses C50 concrete. The beam body concrete is mixed with polypropylene fiber, and the mixing amount is 0.9kg / m 3 .

[0041] like Figure 4 As shown, in this embodiment, the top plate bundle 7, the web plate bundle 8 and the bottom plate bundle 9 are arranged to the outside of the small radius curved U-shaped beam, and the central symmetry line of the top plate bundle 7, the web plate bundle 8 and the bottom plate bundle 9 is located outside the vertical center line of the middle web 2. The outside refers to the side of the small radius curved U-shaped beam away from its center. Specifically, the outside is as shown in FIG. Figure 1 , Figure 4 As indicated in the figure, the central symmetry line of the top plate bundle 7, the web bundle 8 and the bottom plate bundle 9 is originally located in the middle of the middle web 2 (as shown in Figure 4 ), in this embodiment, the central symmetry line is offset outward, that is, to the right, to control the bending and torsional deformation and vibration response increment of the entire bridge, which is better suitable for the maglev connected U-beam.

[0042] like Figure 5 , Figure 6 As shown, in this embodiment, a rail support platform 6 is provided on the bottom plate 3 between the side web 1 and the middle web 2, and a drainage hole 13 and an emergency drainage port 14 are provided on both sides of the rail support platform 6 on the bottom plate 3.

[0043] In this embodiment, a waterproof layer 12 is provided on the base plate 3, and a waterproof layer 12 extending from the base plate 3 to the side of the rail support platform 6 is provided at the junction of the base plate 3 and the rail support platform 6. A concrete slope layer 15 is provided below the waterproof layer 12. The waterproof layer 12 includes a sealing paint layer 123, a waterproof primer layer 122 and a waterproof topcoat layer 121 from bottom to top; the total thickness of the waterproof layer 12 is not less than 600 μm and not more than 800 μm, the dry film thickness of the waterproof primer layer 122 is not less than 400 μm, and the dry film thickness of the waterproof topcoat layer 121 is not less than 200 μm.

[0044] The present embodiment also provides a construction method for the above-mentioned small-radius curved connected U-shaped beam. At the construction site of the small-radius curved connected U-shaped beam, the pre-tensioning method is adopted, and the tensioning process of single-beam initial adjustment, overall initial tensioning, and single-beam final tensioning is adopted. The over-tensioning coefficient is adjusted in combination with the arch value of the small-radius curved connected U-shaped beam after tensioning, and the tensioning force value of a single prestressed tendon is independently controlled.

[0045] In a certain project in a certain area, a continuous beam bridge with a span of 3×25m is used, with a small radius (the inner curve radius R is 100m, such as Figure 1The continuous beam (as shown) adopts the above-mentioned small radius curved connected U-shaped beam. The total length of each span U beam is 24.9m, the calculated span is 24.1m, the standard section beam height is 1.8m, the top width is 10.2m, the bottom width is 8.78m, the thickness of the side web 1 is 0.4m, and the thickness of the middle web 2 is 0.6m. The beam body is arranged along the center line of the right line of the line designed at the work point, and the corresponding beam body contour drawings are all the unfolded dimensions along the center line of the right line of the line. The arrangement of the prestressed tendons is as follows Figure 4 As shown, a total of 28 low-relaxation steel strands are used. The top plate strand 7, the web plate strand 8 and the bottom plate strand 9 all use low-relaxation steel strands. The index of the low-relaxation steel strand is 21.4kg / m 3 , the top plate beam 7 adopts 7 beams 9-φ s 15.2mm low relaxation steel strand, web bundle 8 uses 6 bundles of 12-φ s 15.2mm low relaxation steel strand, bottom plate bundle 9 uses 15 bundles of 12-φ s The 15.2mm low-relaxation steel strands have a tensioning control stress of 72% of the standard value of the ultimate strength of the prestressed tendons, specifically 1339.2MPa. The number and indexes of the steel strands are significantly lower than those used in traditional U-beams.

[0046] After calculation and analysis, under the static and live loads of the small radius curve working condition of the maglev, the maximum vertical displacement of the U-shaped beam in the mid-span is 3.829mm, and the deflection-span ratio is 1 / 6294.1, which is less than 1 / 4600; the vertical rotation angle at the beam end is 0.457‰rad, which is less than 1‰rad; the first-order vertical bending natural frequency n0=5.053>64 / L=2.66Hz, and the force performance can meet the design specification requirements and has good economy.

Claims

1. A small radius curved U-shaped beam for magnetic levitation, characterized in that: The invention comprises a beam body and a prestressed beam arranged in the beam body, wherein the beam body comprises a bottom plate (3), a middle web plate (2) and an edge web plate (1), wherein the middle web plate (2) is arranged in the middle of the bottom plate (3), and the edge web plates (1) are arranged on both lateral sides of the bottom plate (3), and the prestressed beam comprises a top plate beam (7), a web beam (8) and a bottom plate beam (9), wherein the top plate beam (7) is located in the upper flanges (4) of the edge web plates (1) and the middle web plates (2), the web beam (8) is located in the edge web plates (1), and the bottom plate beam (9) is located in the bottom plate (3).

2. The small radius curve connected U-shaped beam according to claim 1, characterized in that: The top plate bundle (7) is a top plate prestressed tendon, and a plurality of the top plate prestressed tendons are arranged in parallel in the upper flanges (4) of the side webs (1) and the middle webs (2).

3. The small radius curve connected U-shaped beam according to claim 1, characterized in that: The bottom plate bundle (9) comprises edge prestressed tendons arranged on both sides of the bottom plate (3) and middle prestressed tendons arranged in the middle of the bottom, the edge prestressed tendons being arranged close to the side webs (1), the middle prestressed tendons being located below the middle webs (2), and a plurality of the edge prestressed tendons and the middle prestressed tendons being arranged in parallel.

4. The small radius curve connected U-shaped beam according to claim 3, characterized in that: The number of the middle prestressed tendons is greater than the number of the edge prestressed tendons.

5. The small radius curve connected U-shaped beam according to claim 3, characterized in that: The web bundle (8) is a web prestressed tendon arranged in a broken line shape and is provided with a high point and a low point, wherein the high point is connected to the top plate bundle (7) and the low point is connected to the edge prestressed tendon.

6. The small radius curve connected U-shaped beam according to claim 1, characterized in that: The top plate bundle (7), the web plate bundle (8) and the bottom plate bundle (9) are arranged toward the outside of the small radius curved connected U-shaped beam, and the central symmetry line of the top plate bundle (7), the web plate bundle (8) and the bottom plate bundle (9) is located outside the vertical center line of the middle web (2), and the above-mentioned outside refers to the side of the small radius curved connected U-shaped beam away from its center.

7. The small radius curved connected U-shaped beam according to any one of claims 1 to 6, characterized in that: The beam body is integrally formed using high-performance concrete. The span number × span diameter of each unit of the small-radius curved U-shaped beam is (2-4) × 25 m, and the curve radius R is not less than 75 m. The top plate bundle (7), the web bundle (8) and the bottom plate bundle (9) all use low-relaxation steel strands, and the index of the low-relaxation steel strands is 21.4 kg / m 3 The top plate bundle (7) adopts 7 bundles of 9-φ s 15.2 mm low relaxation steel strand, the web bundle (8) uses 6 bundles of 12-φ s 15.2 mm low relaxation steel strand, the bottom plate bundle (9) uses 15 bundles of 12-φ s 15.2mm low relaxation steel strand.

8. The small radius curved connected U-shaped beam according to any one of claims 1 to 6, characterized in that: A rail support platform (6) is provided on the bottom plate (3) between the side web plate (1) and the middle web plate (2), and a drainage hole (13) and an emergency drainage port (14) are respectively provided on the bottom plate (3) on both sides of the rail support platform (6).

9. The small radius curve connected U-shaped beam according to claim 8, characterized in that: A waterproof layer (12) is provided on the bottom plate (3); a waterproof layer (12) extending from the bottom plate (3) to the side of the rail support platform (6) is provided at the junction of the bottom plate (3) and the rail support platform (6); a concrete slope layer (15) is provided below the waterproof layer (12); the waterproof layer (12) comprises, from bottom to top, a sealing paint layer (123), a waterproof primer layer (122) and a waterproof topcoat layer (121); the total thickness of the waterproof layer (12) is not less than 600 μm and not more than 800 μm, the dry film thickness of the waterproof primer layer (122) is not less than 400 μm, and the dry film thickness of the waterproof topcoat layer (121) is not less than 200 μm.

10. A construction method for a small radius curved connected U-shaped beam as claimed in any one of claims 1 to 9, characterized in that: At the construction site of the small-radius curved connected U-shaped beam, the pre-tensioning method is adopted, and the tensioning technology of single-beam initial adjustment, overall initial tensioning and single-beam final tensioning is adopted. The over-tensioning coefficient is adjusted in combination with the camber value of the small-radius curved connected U-shaped beam after tensioning, and the tensioning force value of a single prestressed tendon is controlled individually.

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