Construction method for combination of steel box hybrid beam cable-stayed bridge cable bent tower steel anchor beam and concrete bracket

Abstract

The invention provides a construction method for combining steel box hybrid beam cable-stayed bridge cable bent tower steel anchor beams and concrete brackets, and belongs to the technical field of bridge cable bent tower construction. Tower column pouring and sectional arrangement are carried out, each section of tower column comprises two steel anchor beams, construction is carried out by firstly installing the steel anchor beams and then pouring concrete, and a tower body and a first bracket steel bar are bound; the construction method comprises the steps of bracket embedded steel plate positioning and mounting, bottom section steel anchor beam support erecting, steel anchor beam machining and transporting to a construction site, bottom section steel anchor beam lifting, positioning and temporary fixing, support heightening, tower body and second bracket steel bar binding, second steel anchor beam lifting, positioning and temporary fixing and tower body and bracket concrete pouring. In the steel anchor beam mounting stage, the transverse direction and the longitudinal direction of the main tower are measured at the same time, construction is carried out to key procedures, according to design and monitoring requirements, full-bridge linear measurement, bridge axis measurement, main tower deviation and torsion measurement are carried out, discharging holes and vibrating holes are formed, and concrete bracket quality defects caused by difficult discharging in the pouring process are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of bridge cable tower construction, and in particular to a construction method for combining a steel anchor beam and a concrete bracket of a steel box hybrid beam cable-stayed bridge cable tower. Background Art

[0002] At present, the commonly used cable anchoring forms in China include cable anchoring steel anchor beam structure and tower column annular prestressed structural anchoring form. Among them, the anchored steel anchor beam is to pass the cable through the cableway embedded in the tower wall and anchor it on the anchor blocks at both ends of the steel anchor beam. The steel anchor beam is supported on the concrete bracket on the inner side of the hollow tower column through the anchor pad. The concrete bracket is cast and constructed simultaneously with the tower column. In addition, the steel anchor beam can also be supported on the steel bracket. Conventional steel brackets are manufactured at the same time as the steel anchor beam in a professional steel component manufacturer, hoisted and installed as a whole, and reinforced concrete construction of the same section is carried out after the installation is qualified.

[0003] The existing cable anchoring construction has the following problems: (1) The steel anchor beam and concrete bracket are difficult to install and require high positioning accuracy. The installation accuracy of the steel anchor beam and concrete bracket directly affects the force distribution of the cable. (2) The stress concentration of the concrete bracket is strengthened by reinforcement. The steel bars of the concrete bracket are dense, making it difficult to pour concrete during pouring. Coarse aggregate is not easy to disperse. There is a pre-buried steel plate on the top of the bracket, so it is difficult for coarse aggregate to enter the bracket part. The concrete is not easy to be compacted, which will affect the concrete strength to varying degrees. In order to solve the above problems, a construction method of a steel box hybrid beam cable-stayed bridge tower steel anchor beam and concrete bracket is designed. Summary of the invention

[0004] The purpose of the present invention is to provide a construction method for combining a steel box hybrid beam cable-stayed bridge tower steel anchor beam and a concrete bracket, so as to solve the technical problems existing in the background technology.

[0005] The main tower end of the cable-stayed bridge of this application adopts two anchoring methods: steel anchor beam and concrete anchor tooth block. The steel anchor beam structure is composed of an anchor beam and a concrete corbel, which mainly bears the horizontal component of the cable-stayed cable. There are 19 pairs of cable-stayed cables on each side span and 19 pairs of cable-stayed cables on each middle span. 14 sets of steel anchor beams are arranged in a single tower column of the cable tower, and a total of 56 sets in the whole bridge. The anchor beams are numbered from GML06 to GML19 from bottom to top, and cables No. 1 to 5 are anchored with concrete anchor blocks. The connection method between the anchor beam and the concrete corbel is high-strength bolt connection, and 12 sets of M30 high-strength bolts are used at each end.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The construction method of the steel box hybrid beam cable-stayed bridge cable tower steel anchor beam and concrete corbel combination is arranged in sections according to the tower column casting. Each tower column section contains two steel anchor beams. The steel anchor beams are installed first and then the concrete is poured. First, the tower body and the first corbel are reinforced, the corbel pre-embedded steel plate is positioned and installed, the bottom section steel anchor beam bracket is erected, the steel anchor beam is processed and transported to the construction site, the bottom section steel anchor beam is hoisted, positioned, and temporarily fixed, the bracket is raised, the tower body and the second corbel are reinforced, the second steel anchor beam is hoisted, positioned, and temporarily fixed, and the tower body and corbel are poured with concrete.

[0008] Furthermore, the specific process of processing and transporting the steel anchor beam to the construction site is as follows: the steel anchor beam is welded and formed in the factory and trial assembled, and the overall geometric dimensions, plate surface flatness, docking deviation and bolt hole overlap rate are inspected. After passing the inspection, the anti-corrosion coating of each part is completed. After the anchor beam is processed, the overall geometric dimensions, pad contact surface flatness and bolt hole overlap rate are inspected. After passing the inspection, the high-strength bolts of the anchor beam are preliminarily pre-tightened to prevent relative displacement and sliding when the steel anchor beam is lifted as a whole, so as to ensure the subsequent installation accuracy. The steel anchor beam is transported to the site by land using a special transport vehicle. During transportation, a steel wire rope is used to fix the beam body to the car floor to reduce the deformation of the steel anchor beam during transportation and the wear and tear of the external coating. The steel anchor beam is lifted from the transport vehicle by a tower crane and stored at the construction site at the bottom of the tower, and the tower crane is used for overall lifting.

[0009] Furthermore, when the bracket is erected, it is necessary to arrange the positioning bracket. The specific process is as follows: the weight of the steel anchor beam is concentrated at the two end positions. Combined with the force characteristics of the positioning support frame, in order to increase the contact area between the positioning support frame and the embedded parts of the foundation and ensure the stability of the positioning support frame, the bottom bearing beam between the support frame and the embedded corbel is set to a three-piece I25 I-beam to ensure sufficient rigidity. Before installation, the longitudinal and transverse axes and elevations of the tower column are measured and calibrated in order to accurately control the erection height and plane position of the bracket. The positioning support frame is installed in segments along the transverse bridge direction, and the parallel connection between the steel pipe columns is flange-connected for subsequent disassembly.

[0010] Furthermore, the specific process of installing the steel anchor beam is as follows: the installation of the bottom section steel anchor beam requires the embedding of a corbel in the inner wall of the tower column as the foundation of the bracket. The subsequent tower column construction involves the simultaneous installation of two steel anchor beams. If the foundation embedded parts are used as the load-bearing fulcrum of the beam body, the construction of the embedded parts will be limited by the box room space in the tower column and the embedded plate structure of the elevator and ladder in the tower, making installation and removal difficult and the construction cumbersome. The steel anchor beams of sections GML8-GML19 use the installed steel anchor beams instead of the foundation embedded parts as the force support points of the double-layer steel anchor beams;

[0011] The bottom load-bearing beam of the positioning support frame is made of I25 I-beam, which is placed on the top of the installed steel anchor beam. At the same time, steel pads are set on the top surfaces of the load-bearing beam and the steel anchor beam to reduce the damage of the support frame to the anchor beam coating. Double-piece 22# channel steel is installed on the bottom surface of the load-bearing steel anchor beam, which is connected to the top load-bearing beam through 2 φ32mm fine-rolled threaded steel bars to press and lock the load-bearing beam and the steel anchor beam.

[0012] Furthermore, the specific process of bracket erection is as follows: after the bottom load-bearing beam of the positioning support frame is locked with the steel anchor beam, the steel pipe columns and the parallel scissors braces of the support frame are installed, and they are installed piece by piece along the transverse direction of the main tower. The steel pipe columns and the bottom load-bearing beams are connected and locked with high-strength bolts, and finally the transverse load-bearing beams are installed. After the bracket is installed in place, the longitudinal and transverse axis positions of the tower body are measured and marked with red paint for use. At the same time, the top surface of the bracket is leveled as much as possible, and the three-dimensional adjustment device is installed in place according to the designed steel anchor beam stress point, and the bottom is fixed to the positioning support frame load-bearing beam through a limit plate.

[0013] Furthermore, when the steel anchor beam is lifted, the steel anchor beam is lifted by four lifting ears symmetrically welded on the steel anchor beam. The temporary lifting points of the steel anchor beam are set on both sides of the transverse bridge of the steel anchor beam, and are connected by steel wire ropes and clamps. The steel wire ropes and clamps are selected according to the maximum lifting weight of 10t. After calculation, a single steel wire rope with a diameter of φ24mm and a 100kN clamp are selected.

[0014] Furthermore, when positioning the steel anchor beam, the support position is marked in advance with red paint at the bottom of the steel anchor beam according to the designed force support point, and the first steel anchor beam GML6 that has passed the acceptance and pre-assembled to meet the requirements is slowly lifted to the predetermined installation position of the upper tower column using the tower crane equipped on site. When the height difference between the bottom of the steel anchor beam and the top of the three-dimensional adjustment device is roughly the same, the plane position of the steel anchor beam is adjusted so that the force support position at the bottom of the steel anchor beam corresponds to the three-dimensional adjustment device, and the steel anchor beam is slowly placed on the fine adjustment device at the top of the positioning support frame to complete the initial positioning;

[0015] After the initial positioning of the first steel anchor beam is completed, the positioning bolts are installed first, and then fine-tuned through the three-dimensional fine-tuning device to make the center line of the steel anchor beam coincide with the center line of the tower column section. Finally, the plane position, elevation, flatness and inclination of the steel anchor beam are re-measured. By applying robot measurement, the system error caused by human aiming is avoided. The robot has an angle measurement accuracy of 0.5″, a distance measurement of 0.6mm+1ppm, a prism-free 1000m, and an ATR automatic search for 1000m. It can automatically search for targets at night and track and aim for precise measurement, which can meet the precision positioning requirements of steel anchor beams and improve efficiency.

[0016] After the first layer of steel anchor beams are accurately positioned, continue to tie the tower body steel bars and the second layer of steel anchor beam corbel steel bars. After the steel bars are tied, install the upper steel anchor beam positioning support frame piece by piece along the transverse direction of the bridge. The upper and lower support frames are connected by high-strength bolt flanges. During the lifting and installation process, the support frame should be prevented from colliding with the steel anchor beam to prevent the frame from damaging the anti-corrosion coating of the steel anchor beam. A three-dimensional adjustment device is installed on the top of the bracket, and the installation method is the same as the first section of the steel anchor beam positioning adjustment device.

[0017] Furthermore, during the pouring of the tower body and the corbel concrete, after the steel anchor beam is accurately positioned, the tower column formwork concrete engineering is carried out. When the concrete strength meets the requirements, the positioning support frame is removed, the steel anchor beam is measured and accepted, and the subsequent batch of steel anchor beams are installed. In order to ensure the density of the concrete of the corbel pre-embedded steel plate, the number of vibrations of the concrete near the pre-embedded steel plate should be increased during the vibration process, and the steel plate should be knocked at any time to detect whether the concrete below is dense;

[0018] The specific process of removing the positioning support frame is as follows: the order of removing the positioning support frame is opposite to the order of installation, and it is removed step by step from top to bottom;

[0019] 1) Remove the three-dimensional adjustment device on the top surface of the upper load-bearing beam and the high-strength bolts connecting the flange of the load-bearing beam, use a tower crane to lift one end of the load-bearing beam, that is, the upward side of the tower column, and slowly move the load-bearing beam to the upward side of the tower column through a hand winch. Finally, lift the load-bearing beam vertically and lift it away from the tower column through the space between the steel anchor beam and the tower wall;

[0020] 2) First, remove the high-strength bolts at the bottom of the upper support frame steel pipe. After removing the top load-bearing beam, separate the support frame into two independent frames along the transverse direction of the bridge. Then use a tower crane to remove the frames piece by piece through the space between the steel anchor beam and the tower wall.

[0021] 3) The method for removing the lower positioning support frame is the same as that for the upper support frame.

[0022] Furthermore, when the steel anchor beam is hoisted, positioned, and temporarily fixed, one end of the anchor beam and the corbel is fixed and the other end is free, and the side and middle spans are staggered. The contact surface between the free sliding end anchor beam and the corbel adopts an embedded sliding friction pair. The contact surface between the steel anchor beam and the embedded steel plate of the concrete corbel is processed by a milling machine to a 4mm deep groove, and a 4mm thick stainless steel plate is embedded and pasted. The surface of the stainless steel plate is machined and lubricated with silicone grease to reduce the friction coefficient. The friction coefficient is not greater than 0.05. In order to ensure that the force of the steel anchor beam is clear, the high-strength bolts on one side are screwed into place after the steel anchor beam is hoisted into place, and then the inclined cable is tensioned. After the inclined cable is tensioned, the bolts on the other side are screwed. After the bridge is completed, both ends of the steel anchor beam are bolted to the concrete corbel.

[0023] After the steel anchor beam is hoisted, the corresponding segment tower column concrete is poured according to the construction schedule. Before tensioning the corresponding inclined cables, the high-strength bolts temporarily connected on the sliding side are released until the preload is 0 to ensure that the nuts and washers do not fall off, and the temporary positioning and supporting components are removed.

[0024] Furthermore, the steel anchor beam is a box-shaped structure, which consists of an anchor pad, an anchor plate, an anchor stiffening plate, a vertical stiffening plate, a box-shaped tension plate, a transverse diaphragm and a supporting plate. The cable anchor head acts on the anchor pad, and transmits the pressure to the tension plate and the support through the supporting plate and the stiffening plate. The horizontal component of force is borne by the tension plate, and the vertical component of force is transmitted to the corbel and then to the tower column. The anchor pad and anchor plate are pressure-bearing components, with plate thicknesses of 60mm and 40mm respectively. An anchor stiffening plate with a thickness of 40mm is set under the anchor plate. The tension plates on both sides are tension-bearing components, and the plate thickness is divided into two specifications of 36 and 32mm according to the cable force. In order to increase the stability of the steel plate of the steel anchor beam, a vertical stiffening plate with a thickness of 24mm is welded on the outer side of the side tension plate, and a top plate with a thickness of 30mm is set on the top surface between the box-shaped tension plates.

[0025] Concrete corbels are the supporting structure of steel anchor beams. Each steel anchor beam is directly supported on a pair of corbel embedded top plates. The embedded top plates are made of 40mm thick steel plates. In order to better combine with concrete, shear nails are arranged on the embedded plates. The shear nails are Φ22mm cylindrical head welded nails with a length of 200mm. Six φ33mm round holes are set on both sides of the embedded plate at the fixed end, and six φ33×40mm long round holes are set on both sides of the embedded plate at the sliding end. M30 high-strength bolts pass through the round holes and are embedded in the concrete corbels. Two 20mm thick pads are set between the steel anchor beam and the corbel top plate.

[0026] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0027] During the installation stage of the steel anchor beam of the present invention, it is required to measure the linear shape of the steel anchor beam under different assembly processes and different working conditions, and simultaneously measure the horizontal and vertical directions of the main tower. When the construction reaches the key process, the linear shape of the entire bridge, the bridge axis, the offset and torsion of the main tower are measured according to the design and monitoring requirements, and feeding holes and vibration holes are set to avoid quality defects of the concrete corbel due to difficulties in feeding during the pouring process. The number of steel anchor beams is optimized, and concrete corbels are used instead of steel corbels, which can shorten the construction period by half a month and save the project cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are only for the purpose of enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0030] like Figure 1 As shown, the construction method of the steel box hybrid beam cable-stayed bridge cable tower steel anchor beam and concrete corbel is arranged in sections according to the casting of the tower column. Each tower column contains two steel anchor beams. The steel anchor beams are installed first and then the concrete is poured. First, the tower body and the first corbel are reinforced, the corbel pre-embedded steel plate is positioned and installed, the bottom section steel anchor beam bracket is erected, the steel anchor beam is processed and transported to the construction site, the bottom section steel anchor beam is hoisted, positioned, and temporarily fixed, the bracket is raised, the tower body and the second corbel are reinforced, the second steel anchor beam is hoisted, positioned, and temporarily fixed, and the tower body and corbel are poured with concrete.

[0031] Steel anchor beam transportation:

[0032] (1) After the anchor beam is processed, the overall geometric dimensions, flatness of the pad contact surface and the overlap rate of the bolt holes are inspected. The steel anchor beam is welded and assembled in the factory, and the overall geometric dimensions, plate surface flatness, docking deviation and overlap rate of the bolt holes are inspected. After passing the inspection, the anti-corrosion coating of each part is completed.

[0033] (2) After passing the inspection, the high-strength bolts of the anchor beam are preliminarily pre-tightened to prevent relative displacement and sliding of the steel anchor beam when it is lifted as a whole, thereby ensuring the accuracy of subsequent installation.

[0034] (3) The steel anchor beam is transported to the site by land using a special transport vehicle. During transportation, a steel wire rope is used to fix the beam body to the bottom plate of the carriage to reduce the deformation of the steel anchor beam during transportation and the wear and tear of the external coating. The steel anchor beam is lifted from the transport vehicle by a tower crane and stored at the construction site at the bottom of the tower, and the tower crane is used for overall lifting.

[0035] Arrangement of positioning bracket:

[0036] The weight of the steel anchor beam is concentrated at the two end positions, combined with the force characteristics of the positioning support frame. In order to increase the contact area between the positioning support frame and the embedded foundation parts and ensure the stability of the positioning support frame, the bottom bearing beam between the support frame and the embedded bracket is set to three I25 I-beams to ensure sufficient rigidity. Before installation, the longitudinal and transverse axes and elevations of the tower column are measured and calibrated to accurately control the erection height and plane position of the bracket. The positioning support frame is installed in sections along the transverse bridge direction, and the parallel connection between the steel pipe columns is connected by flanges for subsequent disassembly.

[0037] Steel anchor beam installation:

[0038] The installation of the bottom steel anchor beam requires the embedding of a corbel on the inner wall of the tower column as the foundation of the bracket. The subsequent tower column construction involves the simultaneous installation of two steel anchor beams. If the foundation embedded parts are used as the load-bearing fulcrum of the beam body, the construction of the embedded parts will be restricted by various structures such as the box room space inside the tower column and the elevator and ladder embedded plates inside the tower, making installation and removal difficult and construction cumbersome. Therefore, the steel anchor beams of sections GML8-GML19 use the installed steel anchor beams instead of the foundation embedded parts as the force support points of the double-layer steel anchor beams.

[0039] The bottom load-bearing beam of the positioning support frame is made of I25 I-beam, which is placed on the top of the installed steel anchor beam. At the same time, steel pads are set on the top surfaces of the load-bearing beam and the steel anchor beam to reduce the damage of the support frame to the anchor beam coating. The bottom surface of the load-bearing steel anchor beam is installed with double-jointed 22# channel steel, which is connected to the top load-bearing beam through 2 φ32mm fine-rolled threaded steel bars, and the load-bearing beam and the steel anchor beam are pressed and locked.

[0040] (1) Bracket installation

[0041] After the bottom load-bearing beam of the positioning support frame is locked with the steel anchor beam, the steel pipe columns and the parallel scissor braces of the support frame are installed piece by piece along the transverse direction of the main tower. The steel pipe columns and the bottom load-bearing beams are connected and locked with high-strength bolts. Finally, the transverse load-bearing beams are installed. After the bracket is installed in place, the longitudinal and transverse axis positions of the tower body are measured and marked with red paint for standby use, and the top surface of the bracket is leveled as much as possible. The three-dimensional adjustment device is installed in place according to the designed steel anchor beam force point, and the bottom is fixed to the positioning support frame load-bearing beam through a limit plate.

[0042] (2) Lifting of steel anchor beam

[0043] The steel anchor beam is hoisted by four lifting lugs symmetrically welded on the steel anchor beam. The temporary lifting points of the steel anchor beam are set on both sides of the transverse bridge of the steel anchor beam. It is connected by steel wire rope and clamp ring. The steel wire rope and clamp ring are selected according to the maximum lifting weight of 10t. After calculation, a single steel wire rope with a diameter of φ24mm and a 100kN clamp ring are selected.

[0044] (3) Steel anchor beam positioning

[0045] According to the designed load-bearing support points, the support positions are marked with red paint at the bottom of the steel anchor beam in advance, and the first steel anchor beam GML6 that has passed the acceptance and pre-assembled to meet the requirements is slowly lifted to the predetermined installation position of the upper tower column using the tower crane equipped on site. When the height difference between the bottom of the steel anchor beam and the top of the three-dimensional adjustment device is roughly equivalent, the plane position of the steel anchor beam is adjusted so that the load-bearing support position at the bottom of the steel anchor beam corresponds to the three-dimensional adjustment device, and the steel anchor beam is slowly placed on the fine-adjustment device at the top of the positioning support frame to complete the initial positioning.

[0046] After the initial positioning of the first steel anchor beam is completed, the positioning bolts are installed first, and then fine-tuned through the three-dimensional fine-tuning device to make the center line of the steel anchor beam coincide with the center line of the tower column section, and finally the plane position, elevation, flatness and inclination of the steel anchor beam are remeasured. The project avoids system errors caused by manual aiming by applying Leica's high-end robot TS60 (angle measurement accuracy of 0.5″, distance measurement of 0.6mm+1ppm, prism-free 1000m, ATR automatic mark search 1000m), with high measurement accuracy, powerful functions, strong automation, and the ability to automatically search for targets at night and track and aim for precise measurement, which can meet the needs of accurate positioning of steel anchor beams and improve efficiency.

[0047] After the first layer of steel anchor beams are precisely positioned, continue to tie the tower body steel bars and the second layer of steel anchor beams’ corbel steel bars. After the steel bars are tied, install the upper steel anchor beam positioning support frame piece by piece along the transverse direction of the bridge. The upper and lower support frames are connected by high-strength bolt flanges. During the lifting and installation process, avoid the support frame colliding with the steel anchor beam to prevent the frame from damaging the anti-corrosion coating of the steel anchor beam. Install a three-dimensional adjustment device on the top of the bracket. The installation method is the same as the first section of the steel anchor beam positioning adjustment device.

[0048] (4) Tower column concrete construction

[0049] After the steel anchor beam is precisely positioned, the tower column formwork concrete engineering construction is carried out. When the concrete strength meets the requirements, the positioning support frame is removed, the steel anchor beam is measured and accepted, and the subsequent batch of steel anchor beams are installed.

[0050] At the same time, in order to avoid contamination of the lower steel anchor beam during construction, geotextile or film is used for wrapping and protection according to the on-site material conditions. In order to ensure the compactness of the concrete of the corbel pre-embedded steel plate, the number of vibrations of the concrete near the pre-embedded steel plate should be increased during the vibration process, and the steel plate should be knocked at any time to check whether the concrete below is compact.

[0051] (5) Removal of positioning bracket

[0052] The order of removing the positioning support frame is opposite to the order of installation, and it should be removed step by step from top to bottom.

[0053] 1) Remove the three-dimensional adjustment device on the top surface of the upper load-bearing beam and the high-strength bolts connecting the flange of the load-bearing beam, use a tower crane to lift one end of the load-bearing beam (on the upward side of the tower column), and slowly move the load-bearing beam to the upward side of the tower column through a hand winch. Finally, lift the load-bearing beam vertically and lift it away from the tower column through the space between the steel anchor beam and the tower wall.

[0054] 2) First, remove the high-strength bolts at the bottom of the steel pipe of the upper support frame. After removing the top load-bearing beam, the support frame is separated into two independent frames along the transverse direction of the bridge. Then use a tower crane to remove the frame piece by piece through the space between the steel anchor beam and the tower wall.

[0055] 3) The method for removing the lower positioning support frame is the same as that for the upper support frame.

[0056] The horizontal force of the cable along the bridge is divided into two parts: the constant load cable force is borne by the anchor beam, and the later operational load cable force is borne by the anchor beam and the tower wall. To achieve this force mode, ① During the construction process, one end of the anchor beam and the bracket is fixed and the other end is free, and the side and middle spans are staggered. ② The contact surface between the free sliding end anchor beam and the bracket adopts an embedded sliding friction pair. The contact surface between the steel anchor beam and the embedded steel plate of the concrete bracket is processed by a milling machine to a 4mm deep groove, and a 4mm thick stainless steel plate is embedded and pasted. The surface of the stainless steel plate is machined and lubricated with silicone grease to reduce the friction coefficient, which is not greater than 0.05. In order to ensure that the steel anchor beam is clearly stressed, after the steel anchor beam is hoisted into place, the high-strength bolts on one side are screwed into place first, and then the inclined cable is tensioned; after the inclined cable is tensioned, the bolts on the other side are screwed; after the bridge is completed, both ends of the steel anchor beam are bolted to the concrete bracket.

[0057] After the steel anchor beam is hoisted, the corresponding segment tower column concrete is poured according to the construction schedule. Before tensioning the corresponding inclined cables, the high-strength bolts temporarily connected on the sliding side are released until the preload is 0 (be careful to ensure that the nuts and washers do not fall off), and the temporary positioning and supporting components are removed.

[0058] After the tensioning of the entire bridge's cable stays is completed, the bottom plate of the sliding side steel anchor beam is finally tightened to connect with the concrete corbel embedded steel plate bolts.

[0059] In order to avoid the adverse effect of the large unbalanced horizontal component of the cable-stayed cables on the cable towers, the side span and mid span cable-stayed cables are required to be tensioned synchronously and symmetrically.

[0060] The steel anchor beam is a box-shaped structure, which consists of an anchor pad, an anchor plate, an anchor stiffening plate, a vertical stiffening plate, a box-shaped tie plate, a transverse diaphragm and a support plate. The cable anchor head acts on the anchor pad. The pressure is transmitted to the tie plate and the support through the support plate and the stiffening plate. The horizontal component of force is borne by the tie plate, and the vertical component of force is transmitted to the corbel and then to the tower column. The anchor pad and anchor plate are the main pressure-bearing components, with plate thicknesses of 60mm and 40mm respectively; a stiffening plate under the anchor plate is set under the anchor plate, with a thickness of 40mm; the tie plates on both sides are the main tensile components, and the plate thickness is divided into two specifications of 36 and 32mm according to the cable force. In order to increase the stability of the steel plate of the steel anchor beam, a vertical stiffening plate with a thickness of 24mm is welded on the outside of the side tie plate; a top plate with a thickness of 30mm is set on the top surface between the box-shaped tie plates.

[0061] Concrete corbels are the supporting structure of steel anchor beams. Each steel anchor beam is directly supported on a pair of corbel embedded top plates. The embedded top plate is made of 40mm thick steel plate. In order to better combine with concrete, shear nails are arranged on the embedded plate. The shear nails are Φ22mm cylindrical head welded nails with a length of 200mm. Six φ33mm round holes are set on both sides of the fixed end embedded plate, and six φ33×40mm long round holes are set on both sides of the sliding end embedded plate. M30 high-strength bolts pass through the round holes and are embedded in the concrete corbels. Two 20mm thick pads are set between the steel anchor beam and the corbel top plate.

[0062] Setting feeding holes and vibration holes can avoid quality defects of concrete corbels caused by difficulties in feeding during pouring. Optimizing the number of steel anchor beams, using concrete corbels instead of steel corbels, shortening the construction period by half a month and saving engineering costs.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A construction method for combining a steel box hybrid beam cable-stayed bridge tower steel anchor beam and a concrete bracket, characterized in that: The tower columns are cast in sections. Each section of the tower column contains two steel anchor beams. The construction is carried out by installing the steel anchor beams first and then pouring concrete. First, the tower body and the first corbel are reinforced, the corbel embedded steel plate is positioned and installed, the bottom section steel anchor beam bracket is erected, the steel anchor beam is processed and transported to the construction site, the bottom section steel anchor beam is hoisted, positioned, and temporarily fixed, the bracket is raised, the tower body and the second corbel are reinforced, the second steel anchor beam is hoisted, positioned, and temporarily fixed, and the tower body and corbel concrete is poured.

2. The construction method of the steel box hybrid beam cable-stayed bridge tower steel anchor beam and concrete bracket combination according to claim 1 is characterized by: The specific process of processing and transporting steel anchor beams to the construction site is as follows: the steel anchor beams are welded and formed in the factory and trial assembled, and the overall geometric dimensions, plate surface flatness, docking deviation and bolt hole overlap rate are inspected. After passing the inspection, the anti-corrosion coating of each part is completed. After the anchor beam is processed, the overall geometric dimensions, pad contact surface flatness and bolt hole overlap rate are inspected. After passing the inspection, the high-strength bolts of the anchor beam are preliminarily pre-tightened to prevent relative displacement and sliding when the steel anchor beam is lifted as a whole, to ensure the subsequent installation accuracy. The steel anchor beam is transported to the site by land using a special transport vehicle. During transportation, a steel wire rope is used to fix the beam body to the car floor to reduce the deformation of the steel anchor beam during transportation and the wear and tear of the external coating. The steel anchor beam is lifted from the transport vehicle by a tower crane and stored at the construction site at the bottom of the tower, and the tower crane is used for overall lifting.

3. The construction method of combining steel box hybrid beam cable-stayed bridge tower steel anchor beam and concrete bracket according to claim 1 is characterized by: When the bracket is erected, it is necessary to arrange the positioning bracket. The specific process is as follows: the weight of the steel anchor beam is concentrated at the two end positions. Combined with the force characteristics of the positioning support frame, in order to increase the contact area between the positioning support frame and the embedded parts of the foundation and ensure the stability of the positioning support frame, the bottom bearing beam between the support frame and the embedded corbel is set to three-piece I25 I-beam to ensure sufficient rigidity. Before installation, the longitudinal and transverse axes and elevations of the tower column are measured and set to accurately control the erection height and plane position of the bracket. The positioning support frame is installed in segments along the transverse bridge direction, and the parallel connection between the steel pipe columns is flange-connected for subsequent disassembly.

4. The construction method of combining steel box hybrid beam cable-stayed bridge tower steel anchor beam and concrete bracket according to claim 1 is characterized by: The specific process of installing the steel anchor beam is as follows: the installation of the bottom section steel anchor beam requires the embedding of the bracket in the inner wall of the tower column as the foundation of the bracket. The subsequent tower column construction involves the installation of two steel anchor beams at the same time. If the foundation embedded parts are used as the load-bearing fulcrum of the beam body, the construction of the embedded parts will be restricted by the box room space in the tower column and the embedded plate structure of the elevator and ladder in the tower, making installation and removal difficult and the construction cumbersome. The steel anchor beams of sections GML8-GML19 use the installed steel anchor beams instead of the foundation embedded parts as the force support points of the double-layer steel anchor beams; The bottom load-bearing beam of the positioning support frame is made of I25 I-beam, which is placed on the top of the installed steel anchor beam. At the same time, steel pads are set on the top surfaces of the load-bearing beam and the steel anchor beam to reduce the damage of the support frame to the anchor beam coating. Double-piece 22# channel steel is installed on the bottom surface of the load-bearing steel anchor beam, which is connected to the top load-bearing beam through 2 φ32mm fine-rolled threaded steel bars to press and lock the load-bearing beam and the steel anchor beam.

5. The construction method of combining steel box hybrid beam cable-stayed bridge tower steel anchor beam and concrete bracket according to claim 3 is characterized by: The specific process of bracket erection is as follows: after the bottom load-bearing beam of the positioning support frame is locked with the steel anchor beam, the steel pipe columns and the parallel scissors braces of the support frame are installed, and they are installed piece by piece along the transverse direction of the main tower. The steel pipe columns and the bottom load-bearing beams are connected and locked with high-strength bolts, and finally the transverse load-bearing beams are installed. After the bracket is installed in place, the longitudinal and transverse axis positions of the tower body are measured and marked with red paint for use. At the same time, the top surface of the bracket is leveled as much as possible, and the three-dimensional adjustment device is installed in place according to the designed steel anchor beam stress point, and the bottom is fixed to the positioning support frame load-bearing beam through a limit plate.

6. The construction method of combining steel box hybrid beam cable-stayed bridge tower steel anchor beam and concrete bracket according to claim 1, characterized in that: When lifting the steel anchor beam, the steel anchor beam is lifted by four lifting ears symmetrically welded on the steel anchor beam. The temporary lifting points of the steel anchor beam are set on both sides of the transverse bridge of the steel anchor beam, and are connected by steel wire ropes and clamps. The steel wire ropes and clamps are selected according to the maximum lifting weight of 10t. After calculation, a single steel wire rope with a diameter of φ24mm and a 100kN clamp are selected.

7. The construction method of combining steel box hybrid beam cable-stayed bridge tower steel anchor beam and concrete bracket according to claim 1, characterized in that: When positioning the steel anchor beam, the support position is marked with red paint at the bottom of the steel anchor beam in advance according to the designed force support point, and the first steel anchor beam GML6 that has passed the acceptance and pre-assembled to meet the requirements is slowly lifted to the predetermined installation position of the upper tower column using the tower crane equipped on site. When the height difference between the bottom of the steel anchor beam and the top of the three-dimensional adjustment device is roughly the same, the plane position of the steel anchor beam is adjusted so that the force support position at the bottom of the steel anchor beam corresponds to the three-dimensional adjustment device, and the steel anchor beam is slowly placed on the fine adjustment device at the top of the positioning support frame to complete the initial positioning; After the initial positioning of the first steel anchor beam is completed, the positioning bolts are installed first, and then fine-tuned through the three-dimensional fine-tuning device to make the center line of the steel anchor beam coincide with the center line of the tower column section. Finally, the plane position, elevation, flatness and inclination of the steel anchor beam are re-measured. By applying robot measurement, the system error caused by human aiming is avoided. The robot has an angle measurement accuracy of 0.5″, a distance measurement of 0.6mm+1ppm, a prism-free 1000m, and an ATR automatic search for 1000m. It can automatically search for targets at night and track and aim for precise measurement, which can meet the precision positioning requirements of steel anchor beams and improve efficiency. After the first layer of steel anchor beams are accurately positioned, continue to tie the tower body steel bars and the second layer of steel anchor beam corbel steel bars. After the steel bars are tied, install the upper steel anchor beam positioning support frame piece by piece along the transverse direction of the bridge. The upper and lower support frames are connected by high-strength bolt flanges. During the lifting and installation process, the support frame should be prevented from colliding with the steel anchor beam to prevent the frame from damaging the anti-corrosion coating of the steel anchor beam. A three-dimensional adjustment device is installed on the top of the bracket, and the installation method is the same as the first section of the steel anchor beam positioning adjustment device.

8. The construction method of combining steel box hybrid beam cable-stayed bridge tower steel anchor beam and concrete bracket according to claim 3 is characterized by: During the pouring of the tower body and corbel concrete, after the steel anchor beam is accurately positioned, the tower column formwork concrete engineering is carried out. When the concrete strength meets the requirements, the positioning support frame is removed, the steel anchor beam is measured and accepted, and the subsequent batch of steel anchor beams are installed. In order to ensure the density of the concrete of the corbel pre-embedded steel plate, the number of vibrations of the concrete near the pre-embedded steel plate should be increased during the vibration process, and the steel plate should be knocked at any time to check whether the concrete below is dense; The specific process of removing the positioning support frame is as follows: the order of removing the positioning support frame is opposite to the order of installation, and it is removed step by step from top to bottom; 1) Remove the three-dimensional adjustment device on the top surface of the upper load-bearing beam and the high-strength bolts connecting the flange of the load-bearing beam, use a tower crane to lift one end of the load-bearing beam, that is, the upward side of the tower column, and slowly move the load-bearing beam to the upward side of the tower column through a hand winch. Finally, lift the load-bearing beam vertically and lift it away from the tower column through the space between the steel anchor beam and the tower wall; 2) First, remove the high-strength bolts at the bottom of the upper support frame steel pipe. After removing the top load-bearing beam, separate the support frame into two independent frames along the transverse direction of the bridge. Then use a tower crane to remove the frames piece by piece through the space between the steel anchor beam and the tower wall. 3) The method for removing the lower positioning support frame is the same as that for the upper support frame.

9. The construction method of combining steel box hybrid beam cable-stayed bridge tower steel anchor beam and concrete bracket according to claim 1, characterized in that: When the steel anchor beam is hoisted, positioned, and temporarily fixed, one end of the anchor beam and the corbel is fixed and the other end is free, and the side and middle spans are staggered. The contact surface between the free sliding end anchor beam and the corbel adopts an embedded sliding friction pair. The contact surface between the steel anchor beam and the embedded steel plate of the concrete corbel is processed by a milling machine to a 4mm deep groove, and a 4mm thick stainless steel plate is embedded and pasted. The surface of the stainless steel plate is machined and lubricated with silicone grease to reduce the friction coefficient. The friction coefficient is not greater than 0.

05. In order to ensure that the force of the steel anchor beam is clear, the high-strength bolts on one side are screwed into place after the steel anchor beam is hoisted into place, and then the inclined cable is tensioned. After the inclined cable is tensioned, the bolts on the other side are screwed. After the bridge is completed, both ends of the steel anchor beam are bolted to the concrete corbel. After the steel anchor beam is hoisted, the corresponding segment tower column concrete is poured according to the construction schedule. Before tensioning the corresponding inclined cables, the high-strength bolts temporarily connected on the sliding side are released until the preload is 0 to ensure that the nuts and washers do not fall off, and the temporary positioning and supporting components are removed.

10. The construction method of combining steel box hybrid beam cable-stayed bridge tower steel anchor beam and concrete bracket according to claim 1, characterized in that: The steel anchor beam is a box-shaped structure, consisting of an anchor pad, an anchor plate, an anchor stiffening plate, a vertical stiffening plate, a box-shaped tension plate, a transverse diaphragm and a supporting plate. The cable anchor head acts on the anchor pad, and transmits the pressure to the tension plate and the support through the supporting plate and the stiffening plate. The horizontal component of force is borne by the tension plate, and the vertical component of force is transmitted to the corbel and then to the tower column. The anchor pad and anchor plate are pressure-bearing components, with plate thicknesses of 60mm and 40mm respectively. An anchor stiffening plate with a thickness of 40mm is set under the anchor plate. The tension plates on both sides are tension-bearing components, and the plate thickness is divided into two specifications of 36 and 32mm according to the cable force. In order to increase the stability of the steel plate of the steel anchor beam, a vertical stiffening plate with a thickness of 24mm is welded on the outer side of the side tension plate, and a top plate with a thickness of 30mm is set on the top surface between the box-shaped tension plates. Concrete corbels are the supporting structure of steel anchor beams. Each steel anchor beam is directly supported on a pair of corbel embedded top plates. The embedded top plates are made of 40mm thick steel plates. In order to better combine with concrete, shear nails are arranged on the embedded plates. The shear nails are Φ22mm cylindrical head welded nails with a length of 200mm. Six φ33mm round holes are set on both sides of the embedded plate at the fixed end, and six φ33×40mm long round holes are set on both sides of the embedded plate at the sliding end. M30 high-strength bolts pass through the round holes and are embedded in the concrete corbels. Two 20mm thick pads are set between the steel anchor beam and the corbel top plate.

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