Main girder structure of extradosed cable-stayed bridge and construction method of main girder structure

Abstract

The invention belongs to the technical field of main beams of cable-stayed bridges, particularly relates to a main beam structure of an extradosed cable-stayed bridge and a construction method of the main beam structure, and solves the problems of insufficient safety and insufficient stress response in the prior art. A base is arranged at the bottom of the main beam, the base is composed of a main column and a plurality of foundation piles distributed at equal intervals, through arrangement of structures such as a crosswind shielding assembly and a cable fixing assembly, in the crosswind shielding assembly, a rotating shaft drives a flow guide plate to adjust the airflow direction in real time, and the transverse impact of wind loads on the main beam is reduced by changing the aerodynamic form; according to the cable fixing assembly, a first liquid viscous damper and a second liquid viscous damper are adopted to form a double-energy-consumption structure, dynamic loads transmitted by the cable are converted into heat energy to be consumed, meanwhile, through a rolling friction mechanism of auxiliary rotating balls in a wire guide block, cable vibration energy is effectively buffered, and structural instability caused by extreme loads is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of the main girder of a cable-stayed bridge, and particularly to a main girder structure of a low tower cable-stayed bridge and a construction method thereof. Background Art

[0002] At present, the main girder of a low tower cable-stayed bridge is the core component in the bridge structure that bears the load and transfers it to the bridge tower and the foundation.

[0003] In the design of the main girder structure of the existing low tower cable-stayed bridge, the traditional technology mainly faces three major technical bottlenecks: First, under the action of crosswind load, the main girder is prone to vortex-induced vibration and flutter. This periodic vibration will not only significantly reduce the driving comfort on the bridge deck, increase the risk of driver operation errors, but also accelerate the accumulation of fatigue damage to the main girder structure. In the long term, it will lead to durability problems such as concrete cracking and steel strand corrosion. Second, there is stress concentration at the connection node between the stay cable and the main girder. In the alternating stress field generated by live load and earthquake action, this area is prone to dynamic amplification effect, making the local stress level exceed the fatigue limit of the material, resulting in sudden failure risks such as anchorage area cracking and cable wire breakage. Third, the connection stiffness between the pile cap and the main girder is insufficient, resulting in an unclear horizontal load transfer path. Under extreme conditions such as strong wind and earthquake, the main girder-pile foundation system is prone to cooperative working failure, manifested as interface slip at the connection and uneven pile foundation stress, significantly weakening the overall seismic performance of the bridge and even causing catastrophic consequences such as overall overturning. Summary of the Invention

[0004] The purpose of the present invention is to provide a main girder structure of a low tower cable-stayed bridge and a construction method thereof, which solve the problems of insufficient safety and insufficient stress response.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A main girder structure of a low tower cable-stayed bridge and a construction method thereof, including a bridge body arranged on the main girder, and a plurality of stay cables evenly distributed at equal intervals are arranged between the bridge body and the main girder;

[0006] A base is arranged at the bottom of the main girder, and the base is composed of a main column and a plurality of piles evenly distributed at equal intervals. The plurality of piles are arranged at the bottom of the main column, and the piles and the main column are fixedly connected to each other. The base is used for fixing the main girder;

[0007] A crosswind shielding component is arranged inside the main girder, and the crosswind shielding component is composed of a plurality of rotating shafts evenly distributed at equal intervals. The rotating shafts are rotatably installed inside the main girder, and a flow deflector is sleeved on the outer peripheral surface of the rotating shafts. The crosswind shielding component is used for shielding crosswind of the main girder;

[0008] On both sides of the main beam, a number of cable fixing components are arranged at equal intervals. The cable fixing components are composed of a first liquid viscous damper and a second liquid viscous damper. The first liquid viscous damper and the second liquid viscous damper are installed at an acute angle on one side of the main beam. The cable fixing components are used for fixing the stay cables.

[0009] As a preferred embodiment of the present invention, a number of conical connecting blocks are arranged at equal intervals and symmetrically on the outer peripheral surface of the main column, and a number of connecting plates are arranged at equal intervals on the bottom of the main beam.

[0010] As a preferred embodiment of the present invention, a circular fixing plate is fixedly connected to the bottom of the connecting plate. A number of first joints are welded to the bottom of the circular fixing plate and are circumferentially distributed. A number of second joints are embedded in the interior of the foundation pile and are circumferentially distributed. The top of the foundation pile is fixedly connected to the circular fixing plate. A connecting buckle is commonly connected to the first joint and the second joint.

[0011] As a preferred embodiment of the present invention, four symmetrically arranged cylinders are installed inside the main beam. A straight shaft is installed at the output end of the cylinder. A long rack is fixedly connected to the top of the straight shaft. A gear is fixedly connected to one end of the rotating shaft. A number of gears are all meshed with the long rack.

[0012] As a preferred embodiment of the present invention, a first connecting shaft is slidably assembled at one end of the first liquid viscous damper. A fixing hook is installed on the first connecting shaft. The stay cable is connected to the fixing hook. A second connecting shaft is slidably assembled at one end of the second liquid viscous damper. A wire guiding block is installed on the second connecting shaft.

[0013] As a preferred embodiment of the present invention, two symmetrically arranged auxiliary rotating beads are rotatably installed on the wire guiding block. The outer peripheral surface of the stay cable is in contact with the auxiliary rotating beads.

[0014] A construction method for the main beam structure of a low tower cable-stayed bridge:

[0015] S71. Foundation installation: Pour the main column at the predetermined bridge location, and arrange the foundation piles at equal intervals at the bottom of the main column. Fix the foundation piles and the main column through concrete pouring or high-strength bolts to form the foundation.

[0016] S72. Main beam positioning: Lift the main beam above the foundation, align it with the conical connecting blocks on the outer peripheral surface of the main column through the connecting plates, and use temporary supports to fix the position of the main beam.

[0017] S73. Fixing the connecting plate and the foundation pile: Weld a circular fixing plate to the bottom of the connecting plate, lock the first joint at the bottom of the circular fixing plate and the second joint at the top of the foundation pile through the connecting buckle to complete the rigid connection between the main beam and the foundation.

[0018] S74. Installation of crosswind shielding assembly: Insert the rotating shaft into the shaft hole preset inside the main girder, and sleeved a flow deflector on the outer peripheral surface of the rotating shaft to ensure that the flow deflector can rotate freely around the rotating shaft;

[0019] S75. Installation of drive mechanism: Install a cylinder inside the main girder, connect the output end of the cylinder to the straight shaft, and fix a long rack on the top of the straight shaft so that the long rack meshes with the gear at the end of the rotating shaft;

[0020] S76. Arrangement of cable fixing components: Fix the first liquid viscous damper and the second liquid viscous damper at an acute angle respectively on the installation positions preset on both sides of the main girder to ensure that the intersection point of their axes is located on the center line of the cross-section of the main girder.

[0021] A construction method for the main girder structure of a low tower cable-stayed bridge further includes the following steps:

[0022] S81. Connection of stay cables: Pass one end of the stay cable through the wire block at the end of the second liquid viscous damper, make the outer peripheral surface of the cable fit with the auxiliary rotating beads, and slidably connect the wire block to the damper through the second connecting shaft;

[0023] S82. Tensioning and fixing of cables: Pass the other end of the stay cable through the fixing hook at the end of the first liquid viscous damper, adjust the position of the fixing hook through the first connecting shaft, and lock the fixing hook after pre-tensioning the cable;

[0024] S83. Commissioning of dampers: Start the cylinder to drive the straight shaft to move, drive the gear to rotate through the long rack, verify whether the rotation angle of the flow deflector meets the crosswind shielding requirements, and at the same time check whether the damping force output of the first and second liquid viscous dampers under the set displacement meets the design value;

[0025] S84. Overall acceptance: Conduct a combined loading test on the foundation, main girder, crosswind shielding assembly, and cable fixing assembly to verify the collaborative working performance of the structure under static load, dynamic load, and crosswind.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. Through the settings of structures such as the crosswind shielding assembly and the cable fixing assembly, in the crosswind shielding assembly, the rotating shaft drives the flow deflector to adjust the air flow direction in real time, and reduces the lateral impact of wind load on the main girder by changing the aerodynamic form; the cable fixing assembly adopts the first and second liquid viscous dampers to form a double energy dissipation structure, converts the dynamic load transmitted by the stay cables into heat energy consumption, and at the same time, through the rolling friction mechanism of the auxiliary rotating beads in the wire block, effectively buffers the vibration energy of the cables and avoids the structural instability caused by extreme loads.

[0028] 2. Through the settings of the base connection structure, auxiliary rotating beads and other structures, in the base connection structure, the conical joint block of the main column and the connecting plate transfer the horizontal load into vertical component forces through the wedge fitting effect, significantly enhancing the cooperative working ability of the main beam and the pile foundation; the symmetrically arranged auxiliary rotating beads in the wire block adjust the cable direction through adaptive rolling, evenly dispersing the contact stress of the stay cables and avoiding fatigue damage caused by local stress concentration, thereby prolonging the service life of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the overall structure schematic diagram of the present invention;

[0030] Figure 2 is the overall structure schematic diagram of the main beam of the present invention;

[0031] Figure 3 is the bottom view of the overall structure of the main beam of the present invention;

[0032] Figure 4 is the overall structure schematic diagram of the base of the present invention;

[0033] Figure 5 is the schematic diagram of the pile foundation connection structure of the present invention;

[0034] Figure 6 is the overall structure schematic diagram of the crosswind shielding component of the present invention;

[0035] Figure 7 is of the present invention Figure 6 magnified view of the label A in;

[0036] Figure 8 is the overall structure schematic diagram of the cable fixing component of the present invention.

[0037] In the figure: 1. Bridge body; 2. Main beam; 20. Stay cable;

[0038] 21. Base; 211. Main column; 212. Conical joint block; 213. Connecting plate; 214. Circular fixing plate; 215. First joint; 216. Pile foundation; 217. Second joint; 218. Connecting buckle;

[0039] 22. Crosswind shielding component; 221. Cylinder; 222. Straight shaft; 223. Long rack; 224. Rotating shaft; 225. Gear; 226. Deflector;

[0040] 23. Cable fixing component; 231. First liquid viscous damper; 232. First connecting shaft; 233. Fixed hook; 234. Second liquid viscous damper; 235. Second connecting shaft; 236. Wire block; 237. Auxiliary rotating bead. DETAILED DESCRIPTION OF THE INVENTION

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] Please refer to Figure 1-8 , in this embodiment, a main beam structure of a low tower cable-stayed bridge includes a bridge body 1 provided on the main beam 2, and a plurality of equally spaced stay cables 20 are provided between the bridge body 1 and the main beam 2;

[0043] A base 21 is provided at the bottom of the main beam 2. The base 21 is composed of a main column 211 and a plurality of equally spaced foundation piles 216. The plurality of foundation piles 216 are provided at the bottom of the main column 211, and the foundation piles 216 and the main column 211 are fixedly connected to each other. The base 21 is used for fixing the main beam 2;

[0044] A crosswind shielding assembly 22 is provided inside the main beam 2. The crosswind shielding assembly 22 is composed of a plurality of equally spaced rotating shafts 224. The rotating shafts 224 are rotatably installed inside the main beam 2, and a flow deflector 226 is sleeved on the outer peripheral surface of the rotating shafts 224. The crosswind shielding assembly 22 is used for shielding the crosswind of the main beam 2;

[0045] A plurality of equally spaced cable fixing assemblies 23 are provided on both sides of the main beam 2. The cable fixing assemblies 23 are composed of a first liquid viscous damper 231 and a second liquid viscous damper 234. The first liquid viscous damper 231 and the second liquid viscous damper 234 are installed at an acute angle on one side of the main beam 2. The cable fixing assemblies 23 are used for fixing the stay cables 20.

[0046] Specifically, the main body consists of a bridge body 1, a main beam 2, and a base 21. The base 21 adopts a combined design of a main column 211 and multiple foundation piles 216. The main column 211 is vertically arranged at the position of the bridge pier, and the foundation piles 216 are evenly distributed circumferentially along the bottom of the main column 211 and are fixed by pouring high-strength concrete, forming a stable pile foundation cap structure. The main beam 2 spans above the base 21, and its bottom is fitted with a tapered joint block 212 on the outer peripheral surface of the main column 211 through a welded connecting plate 213, realizing the rigid connection between the main beam 2 and the base 21. Inside the main beam 2, multiple groups of crosswind shielding components 22 are arranged at equal intervals longitudinally. Each group of components includes a rotating shaft 224, and both ends of the rotating shaft 224 are installed on the side wall of the main beam 2 through bearings, and a streamlined deflector 226 is sleeved on its outer peripheral surface. When encountering crosswinds, the deflector 226 can rotate around the rotating shaft 224 to a specific angle, reducing the lateral impact of the wind load on the main beam 2 by changing the airflow direction. Cable fixing components 23 are symmetrically arranged on both sides of the main beam 2. Each group of components consists of a first liquid viscous damper 231 and a second liquid viscous damper 234, which are welded to the side wall of the main beam 2 at an acute angle, and their ends are respectively connected to the stay cables 20. The first liquid viscous damper 231 directly anchors the end of the cable through a fixing hook 233, and the second liquid viscous damper 234 guides the cable path through a wire guide block 236, forming a double fixing and energy dissipation structure, effectively dispersing the dynamic load transmitted by the stay cables 20.

[0047] In this embodiment, a number of equally spaced and symmetrically arranged tapered joint blocks 212 are provided on the outer peripheral surface of the main column 211, and a number of equally spaced connecting plates 213 are provided at the bottom of the main beam 2.

[0048] Specifically, multiple groups of tapered joint blocks 212 are welded at equal intervals along the height direction on the outer peripheral surface of the main column 211. Each group of joint blocks has a symmetric trapezoidal structure, and its inclined surface is completely fitted with the inclined surface of the connecting plate 213 at the bottom of the main beam 2. The connecting plate 213 is machined into shape by a numerical control machine tool, and a circular fixing plate 214 is welded at the bottom. A number of first joints 215 are evenly distributed on the circumference of the bottom surface of the fixing plate. A second joint 217 is pre-embedded at the top of the foundation pile 216, and internal threads are provided on the inner wall of the second joint 217 to match the external threads of the first joint 215. During installation, the circular fixing plate 214 is covered on the top of the foundation pile 216, and the first joint 215 and the second joint 217 are locked one by one through a connecting buckle 218, forming a flange connection structure. This design significantly improves the shear resistance and anti-overturning ability of the main beam 2 and the base 21 through the wedge-shaped fitting of the tapered joint blocks 212 and the cooperation of multiple bolts, and at the same time facilitates accurate alignment and rapid assembly during the construction stage.

[0049] In this embodiment, the bottom of the connecting plate 213 is fixedly connected to a circular fixing plate 214, and a plurality of first joints 215 evenly distributed around the circumference are welded to the bottom of the circular fixing plate 214. A plurality of second joints 217 evenly distributed around the circumference are pre-embedded inside the foundation pile 216. The top of the foundation pile 216 and the circular fixing plate 214 are fixedly connected to each other, and a connecting buckle 218 is commonly connected to the first joint 215 and the second joint 217.

[0050] Specifically, four groups of symmetrically arranged cylinders 221 are preset inside the main beam 2. The cylinder body of the cylinder 221 is fixed to the bottom plate of the main beam 2 by bolts, and the end of its piston rod is connected to the straight shaft 222. A long rack 223 is welded on the top of the straight shaft 222, and the surface of the rack is quenched to improve wear resistance. The end of each group of rotating shafts 224 is keyed to the gear 225, and the module of the gear 225 is consistent with the module of the rack to ensure smooth meshing transmission. When the cylinder 221 receives the signal from the wind speed sensor, the piston rod pushes the straight shaft 222 to move longitudinally, driving the long rack 223 to drive multiple gears 225 to rotate synchronously, thereby adjusting the angle of the guide plate 226. The guide plate 226 is made of lightweight alloy material, and the surface is sprayed with an anti-corrosion coating. Its rotation range is controlled by a limit switch and can be steplessly adjusted between 0°-60° to achieve dynamic adaptation and energy dissipation of crosswind loads.

[0051] In this embodiment, four symmetrically arranged cylinders 221 are installed inside the main beam 2, and a straight shaft 222 is installed at the output end of the cylinder 221. A long rack 223 is fixedly connected to the top of the straight shaft 222, and one end of the rotating shaft 224 is fixedly connected to a gear 225. Several gears 225 are engaged with the long rack 223.

[0052] Specifically, a sliding cavity is provided at the end of the first liquid viscous damper 231, into which a first connecting shaft 232 is embedded. A U-shaped fixing hook 233 is welded to the end of the connecting shaft. After the diagonal cable 20 passes through the fixing hook 233, the end is secured by a hydraulic locking device. A guide sleeve is provided at the end of the second liquid viscous damper 234, into which a second connecting shaft 235 is slidably mounted. A conductor block 236 is welded to the end of the connecting shaft. The conductor block 236 has a V-shaped groove on its surface, into which two sets of auxiliary rotating beads 237 are embedded. The rotating beads are made of high-strength ceramic and have a chrome-plated surface. When the diagonal cable 20 passes through the conductor block 236, rolling friction is generated between the rotating beads, effectively reducing wear caused by cable vibration. When the bridge is subjected to live loads or earthquakes, the first and second liquid viscous dampers 234 utilize the viscous damping properties of silicone oil to convert the dynamic tension of the cable into heat energy dissipation. At the same time, the auxiliary rotating beads 237 adaptively adjust the cable's direction through rolling, avoiding localized stress concentration.

[0053] In this embodiment, a first connecting shaft 232 is slidably assembled at one end of the first liquid viscous damper 231. A fixing hook 233 is installed on the first connecting shaft 232, and the stay cable 20 is connected to the fixing hook 233. A second connecting shaft 235 is slidably assembled at one end of the second liquid viscous damper 234, and a wire guiding block 236 is installed on the second connecting shaft 235.

[0054] Specifically, the foundation pile 216 adopts a variable cross-section design, the pile diameter gradually increases along the depth, and the pile bottom is embedded in the moderately weathered rock stratum. The corrugated steel web is pre-embedded inside the main column 211, and prestress is applied by the post-tensioning method to form a structure with a gradient distribution of flexural stiffness. Structural adhesive is coated on the contact surface between the connecting plate 213 and the tapered joint block 212 of the main column 211, and shear key grooves are provided to prevent the connection surface from slipping. A rubber shock cushion layer is provided on the contact surface between the circular fixing plate 214 and the top of the foundation pile 216, and seismic energy is absorbed through compressive deformation. When the bridge is subjected to horizontal loads, the foundation 21 transfers the loads to the pile foundation through the rigid connection between the main column 211 and the foundation pile 216. The tapered joint block 212 at the connection between the main girder 2 and the foundation 21 converts part of the loads into vertical components through the wedge effect, reducing the shear stress of the connecting bolts. At the same time, the rubber cushion realizes energy buffering through hysteretic deformation.

[0055] In this embodiment, two symmetrically arranged auxiliary rotating beads 237 are rotatably installed on the wire guiding block 236, and the outer peripheral surface of the stay cable 20 is in contact with the auxiliary rotating beads 237.

[0056] Specifically, the angle adjustment of the flow deflector 226 is preset with multiple thresholds by the central control system according to the wind tunnel test data. When the real-time wind speed exceeds the set value, the driving mechanism of the cylinder 221 is started, and the precise control of the angle of the flow deflector 226 is realized through the rack and gear 225 transmission. At the same time, the first and second liquid viscous dampers 234 automatically adjust the damping coefficient according to the angle change of the flow deflector 226. When the flow deflector 226 is in the large-angle wind shielding state, the damper switches to the high-damping mode to suppress the additional tension generated by the wind-induced vibration of the cable. When the flow deflector 226 is in the small-angle flow guiding state, the damper switches to the low-damping mode to ensure the free deformation of the cable under live loads. The auxiliary rotating beads 237 in the wire guiding block 236 monitor the cable contact stress in real time through pressure sensors. When the stress exceeds the safety threshold, the hydraulic compensation mechanism of the second connecting shaft 235 is triggered to automatically adjust the position of the wire guiding block 236 to achieve the active balance of the cable force.

[0057] A construction method for the main girder structure of a low tower cable-stayed bridge:

[0058] S71. Installation of the foundation 21: Pour the main column 211 at the predetermined bridge location, and arrange the foundation piles 216 equidistantly at the bottom of the main column 211. Fix the foundation piles 216 and the main column 211 through concrete pouring or high-strength bolts to form the foundation 21;

[0059] S72. Positioning of the main beam 2: Lift the main beam 2 above the base 21, align it with the tapered connection block 212 on the outer peripheral surface of the main column 211 through the connection plate 213, and fix the position of the main beam 2 with temporary supports.

[0060] S73. Fixing the connection plate 213 to the foundation pile 216: Weld a circular fixing plate 214 at the bottom of the connection plate 213, and lock the first joint 215 at the bottom of the circular fixing plate 214 and the second joint 217 at the top of the foundation pile 216 with a connection buckle 218 to complete the rigid connection between the main beam 2 and the base 21.

[0061] S74. Assembly of the crosswind shielding component 22: Pass the rotating shaft 224 through the shaft hole preset inside the main beam 2, and sleeved a flow deflector 226 on the outer peripheral surface of the rotating shaft 224 to ensure that the flow deflector 226 can freely rotate around the rotating shaft 224.

[0062] S75. Installation of the drive mechanism: Install a cylinder 221 inside the main beam 2, connect the output end of the cylinder 221 to the straight shaft 222, and fix a long rack 223 at the top of the straight shaft 222 to make the long rack 223 mesh with the gear 225 at the end of the rotating shaft 224.

[0063] S76. Arrangement of the cable fixing component 23: Fix the first liquid viscous damper 231 and the second liquid viscous damper 234 at acute angles respectively on the preset installation positions on both sides of the main beam 2 to ensure that the intersection point of their axes is located on the center line of the cross-section of the main beam 2.

[0064] S81. Connection of the stay cable 20: Pass one end of the stay cable 20 through the wire guide block 236 at the end of the second liquid viscous damper 234, make the outer peripheral surface of the cable fit with the auxiliary rotating bead 237, and slidably connect the wire guide block 236 to the damper through the second connecting shaft 235.

[0065] S82. Tensioning and fixing of the cable: Pass the other end of the stay cable 20 through the fixing hook 233 at the end of the first liquid viscous damper 231, adjust the position of the fixing hook 233 through the first connecting shaft 232, and lock the fixing hook 233 after pre-tensioning the cable.

[0066] S83. Commissioning of the damper: Start the cylinder 221 to drive the straight shaft 222 to move, drive the gear 225 to rotate through the long rack 223, verify whether the rotation angle of the flow deflector 226 meets the crosswind shielding requirements, and at the same time check whether the damping force output of the first and second liquid viscous dampers 234 under the set displacement meets the design value.

[0067] S84. Overall acceptance: Conduct a combined loading test on the base 21, the main beam 2, the crosswind shielding component 22, and the cable fixing component 23 to verify the collaborative working performance of the structure under static load, dynamic load, and crosswind.

[0068] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A main beam structure of a low-tower cable-stayed bridge, comprising a bridge body (1) arranged on a main beam (2), a plurality of equally spaced cable stays (20) being arranged between the bridge body (1) and the main beam (2), and characterized in that: A base (21) is provided at the bottom of the main beam (2), and the base (21) is composed of a main column (211) and a plurality of equally spaced foundation piles (216). The plurality of foundation piles (216) are provided at the bottom of the main column (211), and the foundation piles (216) and the main column (211) are fixedly connected to each other. The base (21) is used to fix the main beam (21); A crosswind shielding assembly (22) is provided inside the main beam (2), the crosswind shielding assembly (22) being composed of a plurality of equally spaced rotating shafts (224), the rotating shafts (224) being rotatably mounted inside the main beam (2), and a guide plate (226) being sleeved on the outer circumference of the rotating shafts (224), and the crosswind shielding assembly (22) being used for crosswind shielding of the main beam (2); A plurality of equally spaced cable fixing assemblies (23) are provided on both sides of the main beam (2). The cable fixing assemblies (23) are composed of a first liquid viscous damper (231) and a second liquid viscous damper (234). The first liquid viscous damper (231) and the second liquid viscous damper (234) are installed at an acute angle on one side of the main beam (2). The cable fixing assemblies (23) are used to fix the inclined cables (20).

2. The main beam structure of a low pylon cable-stayed bridge according to claim 1, characterized in that: A plurality of tapered connecting blocks (212) arranged symmetrically and equidistantly are provided on the outer peripheral surface of the main column (211), and a plurality of connecting plates (213) distributed equidistantly are provided on the bottom of the main beam (2).

3. The main girder structure of a low pylon cable-stayed bridge according to claim 2, characterized in that: The bottom of the connecting plate (213) is fixedly connected to a circular fixing plate (214), the bottom of the circular fixing plate (214) is welded with a plurality of first joints (215) uniformly distributed around the circumference, the interior of the foundation pile (216) is pre-buried with a plurality of second joints (217) uniformly distributed around the circumference, the top of the foundation pile (216) and the circular fixing plate (214) are fixedly connected to each other, and a connecting buckle (218) is commonly connected to the first joint (215) and the second joint (217).

4. The main girder structure of a low tower cable-stayed bridge according to claim 1, characterized in that: Four symmetrically arranged cylinders (221) are installed inside the main beam (2). A straight shaft (222) is installed at the output end of the cylinder (221). A long rack (223) is fixedly connected to the top of the straight shaft (222). One end of the rotating shaft (224) is fixedly connected to a gear (225). Several gears (225) are meshed with the long rack (223).

5. The main beam structure of a low pylon cable-stayed bridge according to claim 1, characterized in that: One end of the first liquid viscous damper (231) is slidably equipped with a first connecting shaft (232), a fixing hook (233) is installed on the first connecting shaft (232), the inclined cable (20) and the fixing hook (233) are connected to each other, and one end of the second liquid viscous damper (234) is slidably equipped with a second connecting shaft (235), and a wire block (236) is installed on the second connecting shaft (235).

6. The main beam structure of a low pylon cable-stayed bridge according to claim 5, characterized in that: Two symmetrically arranged auxiliary rotating beads (237) are rotatably mounted on the conductor block (236), and the outer peripheral surface of the inclined cable (20) is in contact with the auxiliary rotating beads (237).

7. A construction method for the main girder structure of a low tower cable-stayed bridge according to any one of claims 1-6, characterized in that, The following steps are involved: S71. Installation of the base (21): Pour the main column (211) at the predetermined bridge position, and arrange the foundation piles (216) equidistantly at the bottom of the main column (211). Fix the foundation piles (216) and the main column (211) through concrete pouring or high-strength bolts to form the base (21). S72. Positioning of the main beam (2): Lift the main beam (2) above the base (21), align it with the tapered connecting block (212) on the outer peripheral surface of the main column (211) through the connecting plate (213), and fix the position of the main beam (2) with temporary supports. S73. Fixing of the connecting plate (213) and the foundation pile (216): Weld a circular fixing plate (214) at the bottom of the connecting plate (213), and lock the first joint (215) at the bottom of the circular fixing plate (214) and the second joint (217) at the top of the foundation pile (216) through the connecting buckle (218) to complete the rigid connection between the main beam (2) and the base (21). S74. Assembly of the crosswind shielding component (22): Insert the rotating shaft (224) into the axially bored hole preset inside the main beam (2), and sleeved the air deflector (226) on the outer peripheral surface of the rotating shaft (224) to ensure that the air deflector (226) can rotate freely around the rotating shaft (224). S75. Installation of the driving mechanism: Install the cylinder (221) inside the main beam (2), connect the output end of the cylinder (221) to the straight shaft (222), and fix the long rack (223) at the top of the straight shaft (222) to make the long rack (223) engage with the gear (225) at the end of the rotating shaft (224). S76. Arrangement of the cable fixing component (23): Fix the first liquid viscous damper (231) and the second liquid viscous damper (234) at acute angles respectively on the preset installation positions on both sides of the main beam (2) to ensure that the intersection point of their axes is located on the center line of the cross-section of the main beam (2).

8. The construction method of the main girder structure of a low pylon cable-stayed bridge according to claim 7, characterized in that: The following steps are also included: S81. Connection of the stay cables (20): Pass one end of the stay cable (20) through the wire guiding block (236) at the end of the second liquid viscous damper (234), make the outer peripheral surface of the cable fit with the auxiliary rotating bead (237), and slidably connect the wire guiding block (236) and the damper through the second connecting shaft (235). S82. Tensioning and fixing of the cable: Pass the other end of the stay cable (20) through the fixing hook (233) at the end of the first liquid viscous damper (231), adjust the position of the fixing hook (233) through the first connecting shaft (232), pre-tension the cable and then lock the fixing hook (233). S83. Debugging of the damper: Start the cylinder (221) to drive the straight shaft (222) to move, drive the gear (225) to rotate through the long rack (223), verify whether the rotation angle of the air deflector (226) meets the crosswind shielding requirements, and at the same time check whether the damping force output of the first and second liquid viscous dampers (234) under the set displacement meets the design value. S84. Overall acceptance: Conduct a combined loading test on the base (21), the main beam (2), the crosswind shielding component (22), and the cable fixing component (23) to verify the collaborative working performance of the structure under static load, dynamic load, and crosswind action.

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