A self-anchored suspension bridge with a main cable ground anchor

Abstract

The present invention provides a self-anchored suspension bridge with a main cable ground anchor, which includes a main cable, pylons, stiffening girders, suspenders and side piers. The pylons are located on both sides or in the middle of the bridge deck. A main cable saddle is arranged at the top of the pylon to support the main cable. Rotating cable saddles are provided at both ends of the stiffening girder. The main cable vertically descends and is anchored on the foundation of the side pier after passing around the rotating cable saddle at the end of the stiffening girder. The anchorage section of the main cable below the rotating cable saddle includes an integral cable section and a cable dispersion section. A cable dispersion sleeve is provided between the two sections. The cable dispersion sleeve is provided with a fixed support in the longitudinal direction of the bridge. The suspenders are evenly arranged between the main cable and the stiffening girder. The side pier is located below the end of the stiffening girder, and a bearing is arranged at the top of the side pier to support the stiffening girder. The present invention provides a self-anchored suspension bridge with a main cable ground anchor. By vertically descending and anchoring the main cable on the foundation of the side pier after passing around the rotating cable saddle at the end of the stiffening girder, the structure of the main cable anchorage area at the beam end can be greatly simplified, facilitating the anchorage and maintenance of the main cable.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge construction engineering, and particularly to a self-anchored suspension bridge with a main cable ground anchor. Background Art

[0002] A suspension bridge refers to a bridge that uses the main cable suspended by the cable towers as the main load-bearing member of the superstructure. According to the different anchoring positions of the main cable, it is divided into a ground-anchored suspension bridge and a self-anchored suspension bridge. The end of the main cable of the ground-anchored suspension bridge is anchored to the anchor piers on both banks, and the anchor piers are used to bear the tension of the main cable. Although the spanning ability is large, the scale of the anchor piers is large and the cost is expensive. The main cable of the self-anchored suspension bridge is anchored at both ends of the main beam, and there is no need to set up a huge anchor. An internal self-balanced system is formed by the compression of the stiffening beam, which has good economic indicators within a certain range and also provides a solution for building suspension bridges in areas where it is difficult to build anchor piers.

[0003] The main cable anchorage area at the end of the self-anchored suspension bridge is a key point related to the structural safety of the whole bridge. It not only has to bear the main cable anchoring force, but also transfer the concentrated cable force to the entire stiffening beam section. Therefore, the design of the main cable anchorage and the main cable force transfer method is very important. At present, the main cable anchorage structures of self-anchored suspension bridges are roughly divided into three categories:

[0004] (1) Concrete anchorage system. A concrete anchor box is set, and the main cable is dispersed and anchored after entering the concrete anchor box. In this kind of anchorage form, generally, the anchor body needs to be made very large, and a large space is required for the main cable to disperse, and there is also the problem of concrete cracking.

[0005] (2) Steel structure anchorage system. Compared with the concrete anchorage system, the use of a steel structure system can effectively reduce the volume of the anchor body. Due to the large main cable force, the required steel consumption is very large. Due to the stability problem of the steel structure, many rib plates need to be added to the anchor body, and the structure of the anchor body is relatively complex.

[0006] (3) Ring-shaped anchorage system. The main cable uses steel wire ropes and is continuously wound around the prestressed concrete capping beam. This kind of anchorage system can effectively reduce the size of the anchorage structure and improve the seismic performance, but the erection difficulty of the main cable is large and the force of the anchor body is complex.

[0007] In addition, at present, the main cable of the self-anchored suspension bridge generally adopts a post-anchored structure. Compared with the front-anchored structure of the ground-anchored suspension bridge, the installation difficulty of the cable strands in the post-anchored structure is large, it is difficult to effectively anti-corrode the cable strands in the casing, and it is not convenient for maintenance, which affects the service life of the bridge. Summary of the Invention

[0008] To solve the above existing problems, the present invention provides a self-anchored suspension bridge with a main cable ground anchor. The main cable is vertically downward anchored on the foundation of the side pier after passing around the turning saddle at the end of the stiffening girder, which can greatly simplify the structure of the main cable anchorage area at the beam end and facilitate the anchorage and maintenance of the main cable. To achieve this purpose:

[0009] The present invention provides a self-anchored suspension bridge with a main cable ground anchor, including a main cable, cable towers, a stiffening girder, suspenders and side piers. The cable towers are located on both sides or in the middle of the bridge deck. The main saddle is arranged at the top of the cable tower to support the main cable. Turning saddles are arranged at both ends of the stiffening girder. The main cable is vertically downward anchored on the foundation of the side pier after passing around the turning saddle at the end of the stiffening girder. The anchorage section of the main cable below the turning saddle includes an integral cable section and a cable dispersion section. A cable dispersion sleeve is provided between the two sections. The cable dispersion sleeve is provided with a fixed support in the longitudinal direction of the bridge. The suspenders are evenly arranged between the main cable and the stiffening girder. The side piers are located below the ends of the stiffening girder. A bearing is arranged at the top of the side pier to support the stiffening girder.

[0010] As a further improvement of the present invention, the anchorage of the main cable on the foundation of the side pier adopts a front-anchored structure, and this application can adopt a front-anchored structure.

[0011] As a further improvement of the present invention, the stiffening girder is a steel girder, a concrete girder or a steel-concrete composite girder, and steel girders, concrete girders and steel-concrete composite girders can all be used in this application.

[0012] As a further improvement of the present invention, the self-anchored suspension bridge adopts a two-span or multi-span layout form, and two-span or multi-span layout forms can all be used in this application.

[0013] The beneficial effects of the present invention:

[0014] 1. The main cable only turns through the turning saddle at the end of the stiffening girder, without the need for an anchor box structure with complex structure and force, which simplifies the structure of the main cable anchorage area at the beam end.

[0015] 2. The anchorage of the main cable on the foundation of the side pier adopts a front-anchored structure, which is convenient for the anchorage and maintenance of the main cable.

[0016] 3. The main cable is supported by the turning saddle at the beam end. The resultant force of the main cable tensions on both sides of the turning saddle will apply a horizontal force and a downward vertical force to the beam end. The horizontal force compresses the stiffening girder and forms a self-balanced system, and the downward vertical force is transmitted to the side pier and its foundation through the beam end, offsetting most of the tension of the main cable on the side pier foundation, and the design is scientific and reasonable.

[0017] 4. In a traditional self-anchored suspension bridge, the main cable generates an uplift force on the beam end anchorage area. Usually, a counterweight is required at the end of the stiffening beam to prevent the tension of the bearings at the side piers. In the present invention, the vertical force of the main cable on the beam end is a downward pressure, and the bearings at the side piers will not be in tension. The unbalanced tension of the main cable on the side pier foundation is offset by the self-weight of the side pier and the foundation, thus a large amount of counterweight can be saved, reducing the cost and construction difficulty.

[0018] 5. The main cable is vertically anchored to the foundation of the side pier, without generating a horizontal force on the side pier foundation, avoiding the problem that the anchor block of a traditional earth-anchored suspension bridge bears horizontal tension. Brief Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the structural system of the self-anchored suspension bridge with the main cable anchored to the ground in the present invention;

[0020] Figure 2 It is a schematic diagram of the structural force balance at the beam end in the present invention;

[0021] Figure 3 It is a schematic diagram of the force balance of the side pier foundation in the present invention;

[0022] Figure 4 It is a schematic diagram of the structural force balance at the rotating saddle at the beam end in the present invention.

[0023] In the figure, the labels are: 1. Main cable; 2. Cable tower; 3. Stiffening beam; 4. Suspender; 5. Main saddle; 6. Rotating saddle; 7. Side pier; 8. Cable spreader; 9. Bearing. Detailed Description of the Invention

[0024] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments:

[0025] The present invention provides a self-anchored suspension bridge with the main cable anchored to the ground. The main cable is vertically anchored to the foundation of the side pier after passing around the rotating saddle at the end of the stiffening beam, which can greatly simplify the structure of the main cable anchorage area at the beam end and facilitate the anchorage and maintenance of the main cable.

[0026] The present invention provides as Figure 1A self-anchored suspension bridge with a main cable anchor shown, including a main cable 1, a pylon 2, a stiffening girder 3, a suspender 4, and an abutment 7. The pylon 2 is located on both sides or in the middle of the bridge deck. A main cable saddle 5 is provided at the top of the pylon to support the main cable 1. Rotating cable saddles 6 are provided at both ends of the stiffening girder 3. The main cable 1 vertically anchors on the foundation of the abutment 7 after passing around the rotating cable saddles 6 at the beam ends. The anchorage section of the main cable 1 below the rotating cable saddle includes an integral cable section and a cable dispersion section. A cable dispersion sleeve 8 is provided between the two sections to disperse the cable strands of the main cable for anchoring. The cable dispersion sleeve 8 is provided with a fixed support in the longitudinal direction of the bridge to prevent the cable strands in the cable dispersion section from having large longitudinal deformations under the action of temperature, which may cause changes in the internal forces of the cable strands. The suspenders 4 are evenly arranged between the main cable 1 and the stiffening girder 3. The abutment 7 is located below the end of the stiffening girder 3, and a bearing 9 is provided at the top of the abutment to support the stiffening girder.

[0027] Further, the anchorage of the main cable 1 on the abutment foundation adopts a front-anchorage structure, which can facilitate the anchorage and maintenance of the main cable.

[0028] Further, the stiffening girder 3 can adopt a steel girder, a concrete girder, or a steel-concrete composite girder

[0029] Further, the self-anchored suspension bridge can adopt layout forms such as double-span, multi-span, etc.

[0030] The schematic diagram of the structural force balance at the beam end of the present invention is as Figure 2 shown, T is the tension of the main cable, θ is the tangent angle of the main cable above the bridge deck at the rotating cable saddle, and the main cable below the stiffening girder is vertically arranged.

[0031] According to the force decomposition, the horizontal component of the tension of the main cable above the rotating cable saddle is: Tcosθ, and this horizontal force is the pressure transmitted from the main cable to the stiffening girder. The horizontal tension of the main cable and the pressure of the stiffening girder form an internal self-balanced system.

[0032] The vertical component of the tension of the main cable above the rotating cable saddle is: Tsinθ, the vertical tension of the main cable below the rotating cable saddle is: T, and the vertical force provided by the resultant force of the main cable at the rotating cable saddle to the beam end is T - Tsinθ = T(1 - sinθ), and the direction of the force is vertically downward.

[0033] According to the force balance, the reaction force of the beam bottom bearing is equal in magnitude and opposite in direction to the vertical force provided by the resultant force of the main cable at the rotating cable saddle to the beam end, that is, the vertical force of the main cable on the beam end is a downward pressure, and the bearing will not be in tension.

[0034] The schematic diagram of the force balance of the abutment foundation of the present invention is as Figure 3 shown, T is the tension of the main cable, θ is the tangent angle of the main cable above the bridge deck at the rotating cable saddle, and G is the self-weight of the abutment and the foundation.

[0035] The unbalanced tension of the abutment foundation is: T - T(1 - sinθ) - G = Tsinθ - G,

[0036] When the above formula is less than 0, that is, when G > T sinθ, there will be no uplift force on the side pier foundation.

[0037] The schematic diagram of the structural force balance at the cable saddle at the beam end of the present invention is as Figure 4 shown. T is the tension of the main cable, θ is the tangent angle of the main cable above the bridge deck at the cable saddle, the main cable below the stiffening girder is vertically arranged, α is the angle between the sliding surface of the cable saddle and the main cable, and the relationship between α and θ is as follows:

[0038] α = [180 o - (90 o + θ)] / 2 = 45 o – θ / 2

[0039] That is, the angle between the sliding surface of the cable saddle and the horizontal plane is:

[0040] α + θ = 45 o – θ / 2 + θ = 45 o + θ / 2

[0041] The supporting force provided by the cable saddle to the main cable is:

[0042] 2Tsinα = 2Tsin(45 o – θ / 2)

[0043] The direction of the supporting force provided by the cable saddle to the main cable is perpendicular to the sliding surface of the cable saddle.

[0044] The downward pressure of the main cable on the cable saddle is equal in magnitude and opposite in direction to the supporting force provided by the cable saddle to the main cable.

[0045] The following further details the present invention with an actual project as an example.

[0046] The overall layout of the self-anchored suspension bridge in this embodiment is the same as that of the Taohuayu Yellow River Bridge, which is a two-tower three-span self-anchored steel box girder suspension bridge with a span layout of (160 + 406 + 106) m. The elevation layout is as Figure 1 shown. The bridge deck width is 39 m, there are 2 main cables in total, arranged on both sides of the steel box girder. Each main cable has 37 cable strands, and each cable strand consists of 127 high-strength galvanized steel wires with a diameter of 5.3 mm. The main cable of this bridge is anchored using a steel structure anchoring system. The anchorage section is 25.84 m long, integrating functions such as main cable anchorage, cable force diffusion, cable spreader, ballast, bearings, and expansion joints, and the structure is very complex.

[0047] According to the design of the bridge, the tangent angle at the main cable anchorage of a single main cable is 15.152 o , and the cable force at the main cable anchorage of a single main cable under the operating condition is 53076 kN. The uplift force provided by the main cable to the stiffening girder is 53076 × sin15.152o = 13873 kN. The uplift force provided by two main cables on one side for the stiffening girder is 2 × 13873 = 27746 kN. To ensure that there is no uplift force at the bearings at the main cable anchorage beam section, in this bridge, a dead weight is applied to the double-layer steel box girder at the end of the stiffening girder box at the main cable anchorage beam section. The dead weight on one side is 27500 kN, and the remaining small amount of uplift force is offset by the pressure of the self-weight of the beam acting on the bearings. The total dead weight of the whole bridge is 55000 kN, and 2200 m 3 of concrete is used for the dead weight.

[0048] The side piers of the bridge are designed as hollow thin-walled piers. There are two side piers at the corresponding positions on one side and the main cable. The pier body has a single-box single-room cross-section, and the foundation adopts bored cast-in-place piles plus a cap. Taking the north side pier of the bridge as an example, the concrete volume of a single side pier is 1298 m 3 , and the concrete volume of its cap is 737 m 3 , with a total of 2035 m 3 , and the self-weight is 50875 kN, which is much greater than the uplift force of a single main cable of 13873 kN. Therefore, when adopting the main cable ground anchor scheme provided by the invention, using the self-weight of the side pier and the foundation as the dead weight, there will be no uplift force on the side pier foundation, and 2200 m 3 of concrete dead weight for the whole bridge can be saved, reducing the cost and construction difficulty. The vertical force of the main cable on the beam end is a downward pressure, and the bearings of the side piers will not be in tension either.

[0049] When adopting the scheme of the present invention, only a turning saddle needs to be set for the anchorage of the main cable at the beam end. Since the turning angle of the main cable is relatively close to the angle at the main saddle at the tower top, the size of the turning saddle is roughly the same as that of the tower top saddle. The downward pressure of the main cable on the turning saddle is 2 × 53076 × sin(45 o – 15.152 o / 2) = 64509 kN. Only a stiffening structure needs to be set at the beam end to bear the pressure of the turning saddle, and there is no need to consider the spreading and anchoring of the main cable strands, which can greatly simplify the structure.

[0050] The main cable anchorage section below the turning saddle is arranged in the side pier box chamber. The box chamber of the side pier is used as the cable dispersion chamber of the main cable. According to the anchorage requirements of the main cable dispersion section, it is only necessary to gradually widen 1 m on each side of the bottom cross-section of the side pier along the bridge to meet the requirements. The bearings above the side pier are changed to 2 bearings in the transverse direction, and the position of the bearings along the bridge is moved to near the center of the side pier to bear the downward pressure of the main cable transmitted by the turning saddle. The main cable anchorage section enters the side pier box chamber from the middle position between the 2 bearings. The longitudinal fixed support of the cable dispersion sleeve is arranged on the side wall of the side pier box chamber. The anchorage of the main cable strands adopts a front-anchoring structure, which is convenient for construction and maintenance.

[0051] The above are only the preferred embodiments of the present invention, and are not any other form of limitation to the present invention. Any modification or equivalent change made according to the technical essence of the present invention still belongs to the scope of protection required by the present invention.

Claims

1. A Self-anchored suspension bridge with main cable anchored to the ground , comprising a main cable (1), a cable tower (2), a stiffening girder (3), a suspension cable (4) and an abutment (7), characterized in that: The cable towers (2) are located on both sides or in the middle of the bridge deck. A main cable saddle (5) is provided at the top of the cable tower (2) to support the main cable (1). Rotating cable saddles (6) are provided at both ends of the stiffening girder (3). The main cable (1) passes around the rotating cable saddle (6) at the end of the stiffening girder (3) and then vertically anchors to the foundation of the side pier (7). The anchorage section of the main cable (1) below the rotating cable saddle (6) includes an integral cable section and a fan-shaped cable section. A fan-shaped cable sheath (8) is provided between the two sections. The fan-shaped cable sheath (8) is provided with a fixed support in the longitudinal direction of the bridge. The suspenders (4) are evenly arranged between the main cable (1) and the stiffening girder (3). The side pier (7) is located below the end of the stiffening girder (3). A bearing (9) is provided at the top of the side pier (7) to support the stiffening girder (3); The anchorage of the main cable (1) to the foundation of the side pier (7) adopts a front-anchored structure; The stiffening girder (3) is a steel girder, a concrete girder or a steel-concrete composite girder; the self-anchored suspension bridge adopts a two-span or multi-span layout form.

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