Continuous beam integrated three-purpose support system structure of extradosed cable-stayed bridge and construction method

Abstract

According to the extradosed cable-stayed bridge continuous beam integrated three-purpose support system structure and the construction method, steel pipe stand columns are arranged on the widened bearing platform foundations on the front side and the rear side of a pier body to serve as temporary consolidation supports, foundation treatment is reduced, the requirement for bearing capacity can be met, and in the temporary consolidation lengthening process, climbing cones and I-shaped steel are pre-buried in the pier body, so that the construction cost is reduced, and the construction efficiency is improved. The method comprises the following steps: forming a first-layer frame body for pier cap construction by a climbing cone and a temporary consolidation steel pipe upright post, lengthening the steel pipe upright post after pier cap construction is completed, laying I-shaped steel and a disc buckle bracket on the first-layer frame body to construct a second-layer bracket body of a 0 # block, firstly removing the 0 # block frame body after the 0 # block construction is completed, and then removing the frame body of the pier cap through a discharging block. And finally, only the steel pipe stand columns are reserved for temporary consolidation of hanging basket construction. The problems that according to a traditional method, construction of pier caps and 0 # blocks is difficult to complete through a conventional support system, and no temporary consolidation space exists are solved. Belongs to the field of extradosed cable-stayed bridge construction.

Description

Technical Field

[0001] The invention relates to a low-tower cable-stayed bridge continuous beam integrated three-purpose bracket system structure and a construction method, belonging to the field of low-tower cable-stayed bridge construction. Background Art

[0002] At present, with the development of urban construction, more bridge projects need to cross rivers. In order to meet the requirements of river navigation, the bridge span design requirements are high. In order to meet the design and use requirements, low-tower cable-stayed bridges are more widely used in engineering construction. Low-tower cable-stayed bridges are a new type of structural form of bridges. It is a bridge structure between prestressed concrete continuous structure bridges and ordinary cable-stayed bridges. The beam size is small, the bridge has a large span capacity, is less restricted by the clearance under the bridge and the bridge deck elevation, has better wind resistance and stability than suspension bridges, and is more convenient for cantilever construction. It has the advantages of convenient construction, material saving, and high main beam stiffness.

[0003] The conventional pier body shape is pier body + arc-shaped pier cap, which can be directly constructed with steel membrane. If the conventional 0# block is located on land, or there is no such special-shaped pallet, steel pipe brackets, disc brackets, or triangular brackets can be directly used as the frame to make 0# blocks.

[0004] The construction conditions of low-tower cable-stayed bridges are mostly in water, and it is impossible to use disc brackets. The site is limited, and brackets can only be set up in the construction area of ​​the abutment. The pier body and the pier cap are at an angle, and the pier body is small, so it is difficult to set up a triangular bracket, which requires a large number of pieces, and the pier body cannot bear it. After the pier cap is completed, it is impossible to continue to set up brackets to construct the 0# block. Based on this design and construction conditions, it is difficult to use a conventional bracket system to complete the construction of the pier cap and 0# block (the pier cap is generally designed as an elliptical structure to meet the installation of dampers and large bearings. Part of the structure is cantilevered out of the pier body, and the 0# block is flush with the center line of the pier cap. The conventional underwater bracket method cannot simultaneously meet the cast-in-place construction of the pier cap and 0# block); The pier cap is a special-shaped structure, and the space and force structure cannot meet the safety requirements of temporary consolidation and anti-overturning during the cantilever construction of the continuous beam. In addition, the distance between the pier cap and the beam body is too small, and the conventional method of constructing temporary concrete pillars on the pier cap to temporarily consolidate the continuous beam is difficult to achieve, that is, there is no space for temporary consolidation; at the same time, the construction of the underwater pier cap, 0# block and temporary consolidation of the continuous beam requires the construction of independent support systems respectively, which not only increases the material cost, equipment investment and construction time, but also requires the construction and dismantling of the support many times during the construction process, which has a great impact on the construction efficiency and project progress, and also increases the construction safety risk and quality control difficulty.

[0005] For this purpose, a temporary underwater consolidation and support construction structure for the continuous beam of a low-tower cable-stayed bridge was designed, which can simultaneously meet the requirements of the cast-in-place construction of pier caps and 0# blocks and the temporary consolidation of the continuous beam. Summary of the invention

[0006] The present invention provides a three-purpose support system structure and construction method for a continuous beam of a low-tower cable-stayed bridge, so as to solve the problems that it is difficult to complete the construction of pier caps and 0# blocks using a conventional support system in the traditional method, and there is no space for setting temporary consolidation.

[0007] In order to solve the above problems, it is proposed to adopt such a three-purpose support system structure of a continuous beam of a low-tower cable-stayed bridge. A row of steel pipe columns are constructed on the front and rear sides of the pier body as temporary piers. The steel pipe columns are connected and reinforced by diagonal braces. The bottom pedestal is a widened secondary pedestal. The lower end of the steel pipe column is constructed and fixed on the secondary pedestal. Micro-expansion concrete is arranged in the steel pipe column. The hanging leg is fixed by pre-embedded climbing cones at the set position on the pier body. A rectangular incision is opened on the steel pipe column corresponding to the hanging leg. The main distribution beam passes through the steel pipe column through the rectangular incision and one end is laid on the hanging leg. Three-piece I-beams and unloading blocks are installed on the main distribution beam above the hanging leg to control the elevation, and double-piece I-beams in the transverse direction of the bridge are installed on the unloading blocks. Longitudinal support I-beams are distributed and installed on the double-piece I-beams. Square wood is installed on the support I-beams and bamboo plywood is laid to form a pier cap support system.

[0008] 0# block support system: On the basis of the longitudinal supporting I-beam frame, the bottom support bearing main beam is horizontally distributed, and the buckle frame is erected at longitudinal and transverse intervals to the designed elevation. I16 I-beam + full-covered square wood + bamboo plywood are placed on the top support to complete the construction of the 0# block support system;

[0009] Temporary consolidation system of box girder bottom plate: The 0# bottom plate is reserved with holes for consolidation of steel pipe columns and pier beams. Steel bars are evenly arranged inside and outside the steel pipe column 1. The steel bars are anchored in the steel pipe at the top of the pier for no less than 50 cm, and the anchorage length in the beam is no less than 100 cm.

[0010] In the above-mentioned support system structure, the main distribution beam is an I45 I-beam made of Q345B material, the three-piece I-beam is a three-piece I16 I-beam, the double-piece I-beam is a double-piece I45a I-beam, the supporting I-beam is an I32a I-beam, and the bottom support load-bearing main crossbeam is an I20 I-beam with a horizontal spacing of 60cm;

[0011] In the above support system structure, the steel pipe columns are arranged on the front and rear sides of the pier body and the secondary cap. The size of the secondary cap increases the strip foundation of 0.8*1*13.6m and is cast into one with the secondary cap. The steel bars are consistent with the secondary cap. There are 2 rows of steel pipe columns in front and back, 5 in each row, and a total of 10. The center of the steel pipe column is 4.6m away from the center of the pier. The distance between the adjacent piers on the size side is 9.2m. The steel pipe column adopts φ1000mm steel pipe, with a wall thickness of 20mm and a height of 14-18m. It is installed in two sections, and one section of concrete is cast for each installed section.

[0012] In the aforementioned support system structure, the two sections of steel pipe columns are welded with HRB400 grade Φ32 reinforcement steel bars inside and outside the steel pipe to form a "U"-shaped socket, and the steel pipe is inserted into the socket and fixed by welding with the reinforcement steel bars;

[0013] In the aforementioned support system structure, the top of the secondary pedestal is pre-buried with a steel plate of 1200*1200*20mm. Each steel plate is welded with π-shaped steel bars. The position and number of the π-shaped steel bars correspond to the steel pipe column 1 one by one. The spacing between the π-shaped steel bars is 10cm. There are 10 in total, which are inverted on the secondary pedestal. Two layers of Φ16mm anti-crack steel mesh are tied to the lower edge of the steel plate, with a vertical and horizontal spacing of 10*10cm and a layer spacing of 10cm.

[0014] The present invention also provides a construction method for a three-purpose support system for a continuous beam of a low-tower cable-stayed bridge.

[0015] 1) Construction of pier cap support system

[0016] Step 1: Embed steel plates and steel bars

[0017] The secondary pedestal is widened and a steel plate is embedded on the top of the secondary pedestal. Pi-shaped steel bars are welded on each steel plate. The pi-shaped steel bars correspond to the designed positions of the steel pipe columns. Anti-cracking steel mesh is tied to the lower edge of the steel plate.

[0018] Step 2: Install the steel pipe columns

[0019] Install steel pipe columns as temporary piers on the secondary caps on both sides of the pier body, two rows in each direction, 5 columns in each row, a total of 10 columns; the distance between the center of the pier is 4-5m, the distance between adjacent piers is 8-10m, and the height is 14-18m. The steel pipe columns are installed in two sections. Before the construction of the pier cap, only the lower section of the steel pipe column is constructed. After the construction, the concrete of the lower section is poured. Channel steel is used to brace and connect the steel pipe columns horizontally. The upper section of the steel pipe column is constructed before the replacement of bracing and the water collection of the cofferdam, hoisted into place and welded. The hoisting is carried out on the trestle using a 50t truck crane;

[0020] Step 3: Connect the steel pipe column to the pier

[0021] There are leg installation positions designed at the steel pipe columns on both sides of the pier body. Six pre-buried climbing cones are pre-buried at each leg installation position. The legs are fixed and installed through the pre-buried climbing cones. I-beams are used as the main distribution beams to be fixed on the steel pipe columns and the legs respectively.

[0022] Step 4: Build the cap beam cast-in-place platform

[0023] Three-piece I-beams and unloading blocks are installed on the main distribution beam. The bottom of the unloading block is fixed on the three-piece I-beam by welding to control the elevation. Double-piece I-beams in the transverse direction of the bridge are installed on the unloading block and fixed on the unloading block by welding. Longitudinal supporting I-beams are distributed and installed on the double-piece I-beams. Square timbers are installed on the supporting I-beams and bamboo plywood is laid to form a pier cap support system.

[0024] 2) Construction of 0# block support system

[0025] Step 1: After the pier cap is poured, remove the formwork and carry out maintenance;

[0026] Step 2: Build the 0# bracket

[0027] On the basis of the original longitudinal supporting I-beam, the bottom support bearing main beam is horizontally distributed; the buckle frame is erected at longitudinal and transverse intervals to the designed elevation, and the I-beam + full-paved square wood + bamboo plywood are placed on the top support to complete the construction of the 0# bracket system;

[0028] 3) Construction of temporary consolidation system for box beam bottom plate

[0029] Holes for consolidating steel pipe columns and pier beams are reserved on the 0# bottom plate, and steel bars are evenly arranged inside and outside the steel pipe columns. The steel bars are anchored in the steel pipe at the top of the pier for no less than 50 cm, and the anchoring length in the beam is no less than 100 cm. The steel bars at the ends of the beam are bent and welded firmly to the existing steel bars of the beam body. Shear steel bars 20 are added in the longitudinal and transverse directions of the box beam bottom plate, and 4 layers of compressive steel mesh 21 are added to the top of the steel pipe columns with a layer spacing of 10 cm and a longitudinal and transverse spacing of 10 cm for reinforcement. Concrete is poured into the steel pipe columns, and after the subsequent pouring of the beam body concrete, the underwater pier steel pipe columns and the beam body form a temporary consolidation system to jointly bear the subsequent construction loads.

[0030] Compared with the prior art, the present invention sets temporary consolidation on the widened foundation, which can reduce foundation treatment and meet the bearing capacity requirements. In the process of temporary consolidation extension, some climbing cones + I-beams are pre-embedded in the pier body, and the climbing cones and temporary consolidation steel pipe columns form the first-layer frame of the pier cap construction. After the pier cap construction is completed, the steel pipe columns are extended, and then I-beams + disc buckle brackets are laid on the first-layer frame to make the 0# block second-layer bracket frame. After the 0# block construction is completed, the 0# block frame is first dismantled, and then the pier cap frame is dismantled by unloading the block. Finally, only the steel pipe columns are retained as temporary consolidation for the hanging basket construction. The present invention can be completed with a set of bracket system. The pier caps, 0# blocks and temporary consolidation supports that could only be achieved by the previous three separate support systems can reduce construction time, improve construction efficiency, reduce the erection and dismantling of independent support systems, reduce material costs and equipment investment, and save resources by improving construction technology and adopting new support systems and underwater support construction methods; the construction structure and method described in the present invention can reduce safety risks in the construction process, such as reducing manual operations, reducing safety risks for construction personnel, reducing labor demand, and optimizing human resource allocation; by studying and applying key technologies for the construction of low-tower cable-stayed bridges, the construction technology level can be improved, the construction quality can be guaranteed, and the stability of the structure can be enhanced.

[0031] In summary, the structure and method of the present invention can not only improve construction efficiency and safety, but also reduce costs and improve project quality, which is of great significance to the smooth completion of the entire project. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic plan view of the pier cap construction frame in the first phase;

[0033] Figure 2 yes Figure 1 The structural diagram of the middle 1-1 direction (main view);

[0034] Figure 3 yes Figure 1 The structural diagram of the middle 2-2 direction;

[0035] Figure 4 yes Figure 1 The schematic diagram of the structure in the direction 3-3 (side view);

[0036] Figure 5 This is the structural diagram of the 1-1 direction (main view) when it is used as the 0# block construction frame in the second stage;

[0037] Figure 6 This is the structural diagram of the 3-3 direction (side view) when it is used as the 0# block construction frame in the second stage;

[0038] Figure 7This is a schematic diagram of the plane structure when the hanging basket is used as a temporary consolidation frame in the third stage;

[0039] Figure 8 This is the main structural diagram of the third stage when the hanging basket is used as a temporary consolidation frame;

[0040] Fig. 9 It is an end view of the steel pipe column and the reinforcement steel bars;

[0041] Fig.10 It is a structural diagram of the welded reinforcement steel bars of the lower section of the steel pipe column (the embedded connecting steel bars, etc. are not shown);

[0042] Fig.11 It is a structural diagram of the connection between the lower end of the steel pipe column and the cap;

[0043] Fig.12 It is the plan view of the shear reinforcement arrangement of the bottom plate of the steel tube column box girder;

[0044] Fig.13 This is the main view of the shear reinforcement arrangement of the bottom plate of the steel tube column box beam;

[0045] Fig.14 It is the plan view of the arrangement of compression reinforcements in the bottom slab of the steel tube column and box girder;

[0046] Fig.15 This is the main view of the compression reinforcement arrangement of the bottom plate of the steel tube column box girder. DETAILED DESCRIPTION

[0047] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] Example

[0049] Take a real engineering project as an example, refer to the attached Figure 1 To Attachment Fig.13, the present embodiment makes improvements on the support system. The specific improvement is to propose a three-purpose support system structure of a continuous beam of a low-tower cable-stayed bridge. A row of steel pipe columns 1 are constructed on the front and rear sides of the pier body 2 as temporary piers. The steel pipe columns 1 are connected and reinforced by diagonal braces 3. The bottom pedestal 4 is a widened secondary pedestal. The lower end of the steel pipe column 1 is constructed and fixed on the secondary pedestal. Micro-expansion concrete is arranged in the steel pipe column 1. The pier body 2 is fixed with a hanging leg 6 by pre-embedded climbing cone 5 at a set position. A rectangular incision is opened on the steel pipe column 1 corresponding to the hanging leg 6. The main distribution beam 7 passes through the steel pipe column 1 through the rectangular incision and one end is erected on the hanging leg 6. A three-piece I-beam 8 and a drop block 9 are installed on the main distribution beam 7 above the hanging leg 6 to control the elevation, and a double cross-bridge direction is installed on the drop block 9. I-beams 10 are assembled, and longitudinal supporting I-beams 11 are distributed and installed on the double-assembled I-beams 10. Square timbers are installed on the supporting I-beams 11 and bamboo plywood 12 is laid to form a pier cap support system, wherein the main distribution beam 7 is an I45 I-beam made of Q345B material, the triple-assembled I-beam 8 is a triple-assembled I16 I-beam 8, the double-assembled I-beam 10 is a double-assembled I45a I-beam 10, and the supporting I-beam 11 is an I32a I-beam 11. The bottom supporting load-bearing main crossbeam 13 is an I20 I-beam with a horizontal spacing of 60cm, wherein φ10 steel pipes 14 are constructed at the lower parts of the two ends of the main distribution beam 7 respectively, and the upper ends of the φ10 steel pipes 14 are installed with unloading blocks 9, and the cross-bridge double-assembled I-beams 10, supporting I-beams 11, square timbers and bamboo plywood 12 are installed on the unloading blocks 9.

[0050] 0# block support system: On the basis of the longitudinal supporting I-beam 11 frame, the bottom support bearing main beam 13 is horizontally distributed, and the buckle frame 16 is erected at longitudinal and transverse intervals to the designed elevation. I16 I-beam + full-covered square wood + bamboo plywood are placed on the top support to complete the construction of the 0# block support system;

[0051] Temporary consolidation system of box girder bottom plate: 0# bottom plate reserves holes for consolidation of steel pipe columns and pier beams. 15 HRB400 grade Φ32 steel bars are evenly arranged inside and outside the steel pipe columns, anchored in the steel pipe at the pier top for no less than 50cm, and anchored in the beam for no less than 100cm.

[0052] The specific implementation methods are as follows:

[0053] (1) Pier cap construction

[0054] Temporary consolidation measures adopt the steel pipe column 1 as a temporary pier beside the pier. The steel pipe column is set on the front and rear sides of the pier body 2 and the secondary cap. The secondary cap increases the size of the pier by 0.8*1*13.6m (width*height*width). The strip foundation is cast into one with the secondary cap. The steel bars are consistent with the secondary cap. There are 2 rows in front and back, 5 in each row, and a total of 10. The center of the pier is 4.6m away from the center of the pier. The distance between the adjacent piers on the large and small mileage sides is 9.2m. The steel pipe column 1 is a φ1000mm steel pipe with a wall thickness of 20mm and a height of about 16m. The diagonal braces 3 between the steel pipe columns 1 are connected by 18a channel steel and two 18a channel steels are used for horizontal connection. The steel pipe column and the pier body are connected by I45a I-beams and pre-embedded climbing cones in the pier body.

[0055] A steel plate 18 is embedded on the top of the secondary pedestal. The steel plate is 1200*1200*20mm. A π-shaped steel bar 19 is welded on each steel plate 18. The position and number of the π-shaped steel bars 19 correspond to the steel pipe column 1 one by one. The π-shaped steel bars 19 are spaced 10cm apart. There are 10 in total, which are inverted on the secondary pedestal. Two layers of Φ16mm anti-crack steel mesh are tied to the lower edge of the steel plate 18. The vertical and horizontal spacing is 10*10cm, and the layer spacing is 10cm.

[0056] The steel pipe column 1 is installed in two sections (the first section is 9m long, and the second section is about 7m long). One section of concrete is poured for each section installed. Before the pier cap construction, only the first section of the steel pipe column 1 (the lower section of the steel pipe column 1) is constructed. The first section and the second section are hoisted separately. One section of concrete is poured for each section installed. A 25t truck crane is used for hoisting. The remaining part of the steel pipe column 1 requires the concrete strength of the foundation to reach more than 75%. It is constructed before the replacement of support and the water collection of the cofferdam, and then hoisted into place and welded. A 50t truck crane is used for hoisting on the trestle.

[0057] HRB400 grade Φ32 reinforcing steel bars 17 are welded inside and outside the two sections of steel pipes to form a "U"-shaped socket, and the upper section of the steel pipe is inserted into the socket and fixed with the steel bars. Specific methods: 4 groups (2 HRB400 grade Φ32 reinforcing steel bars 17 in each group, 60 cm long) are symmetrically welded on one side on the inner and outer walls of the lower section of the steel pipe (the lower section of the steel pipe column 1) pre-buried in the pedestal 4, and the length of the steel bars extending into the hoisting docking part is 30 cm; 4 groups are also symmetrically welded on one side on the inner and outer walls of the upper section of the steel pipe of the hoisting docking part, and the length of the steel pipe extending into the lower section is 30 cm; the steel pipe of the hoisting docking part is clamped by 8 groups of reinforcing steel bars 17 to form a temporary stabilization measure. At this time, the crane sling cannot be relaxed and is still under stress to increase the stability of the steel pipe. After docking, check the verticality of the steel pipe immediately. After the verticality meets the requirements, weld the parts of the 8 groups of reinforcing steel bars 17 that are not welded to the steel pipe immediately. Only after welding is completed can the crane's sling be released, and the welding of the docking interface should be carried out as soon as possible. The welding length is the circumference of the steel pipe, and the weld height is 20mm.

[0058] The climbing cone 5 embedded in the pier body 2 is an M36 / D25 model climbing cone, and 6 climbing cones 5 are embedded in each hanging leg 6. The horizontal spacing of the climbing cone 5 is 16+16cm, and the vertical spacing is 15cm. The horizontal spacing of the hanging leg 6 is 317+312+288cm. As the supporting point of the main beam of the pier cap support system, a rectangular incision of the I45 I-beam of the main distribution beam of the pier cap support system is reserved at the position of the climbing cone 5 corresponding to the steel pipe column 1. The I45 I-beam made of Q345B material is passed through the steel pipe column 1 and erected on the hanging leg 6 to complete the erection of the main load-bearing components of the support. Three-piece I16 I-beams + unloading blocks + horizontal double-piece I45a I-beams + longitudinal I32a I-beams + horizontal 10*10 square wood + 17mm bamboo plywood are placed on the main distribution beam in turn to make a cast-in-place platform for the cap beam.

[0059] When reaching the position of pre-embedded climbing cone pier body, ① assemble the embedded system on the template according to the drawing and fix it to the template with bolts; ② after pouring, remove the bolts M36x75 and remove the template; ③ install the hanging leg 6 into the climbing cone 5; ④ after the construction is completed, remove the load-bearing bolts, supports and climbing cone 5 for reuse (when pre-embedded climbing cone 5, draw ink lines on the template and measure accurately with a tape measure to ensure the horizontality and verticality of the climbing cone 5).

[0060] 1. Construction of unloading block 9 and distribution beam: after the construction of hanging legs is completed, I45a I-beam is erected along the bridge direction as the main distribution beam 7. The I45a I-beam crosses the φ1000*20mm steel pipe column 1. Vertical steel bars are welded to the steel pipe column 1 at the crossing position to strengthen the force of the steel pipe column 1; ② Install three-piece I-beam 8 (three-piece I16 I-beam) and unloading block 9 on the I45a I-beam, and the bottom of the unloading block 9 is fixed to the three-piece I-beam 8 by welding; ③ After the installation of the unloading block 9 is completed, the elevation is controlled, and a double-piece I-beam 10 (double-piece I45a I-beam) is installed in the horizontal direction of the bridge, and is fixed to the unloading block 9 by welding; ④ Install the longitudinal supporting I-beam 11 (I32a I-beam) with a spacing of 60cm, and use double-piece I32a I-beams at the tower column position.

[0061] Pier cap construction: install 10*10 square timbers on the supporting I-beam 11 under the pier cap with a spacing of 20cm, lay 1.7cm bamboo plywood 12 on the square timber, tie the steel bars, use steel formwork for the pier cap side formwork, the spacing between tie rods is 60*150cm, use φ20 fine-rolled threaded steel to weld and pull the pallet steel bars, and finally pour the concrete using a sky pump.

[0062] (2) Construction of 0# block support system

[0063] After the pier cap is poured, the formwork is removed and maintained. On the basis of the supporting I-beam 11 distribution beam frame, I20 I-beams with a spacing of 60cm are horizontally erected as the bottom support and load-bearing main crossbeam of the 0# block buckle bracket. The buckle frame is erected at a vertical and horizontal spacing of 60cm*60cm and erected to the designed elevation. I16 I-beams + 10*10cm square wood + 17mm bamboo plywood are placed on the top support to complete the construction of the 0# block bracket system and assemble the 0# block formwork.

[0064] (3) Temporary consolidation construction of steel pipe column 1 in water and box beam bottom plate. Holes for consolidation of steel pipe column piers and beams are reserved on the bottom plate of block 0. Thirty bundles of HRB400 grade Φ32 steel bars 15 are evenly arranged along the inside and outside of steel pipe column 1. They are anchored 80 cm into the steel pipe column 1 at the top of the pier and 130 cm into the beam. The steel bars at the inner end of the beam are bent 90° and welded firmly to the existing beam body steel bars. In order to prevent shear and tensile damage at the consolidation part of the pier and beam in the later stage, reinforcement measures are taken. HRB400φ16 stirrups are added in the longitudinal and transverse directions of the bottom plate as shear reinforcement 20, with a spacing of 53mm, totaling 132. Four layers of compressive reinforcement mesh 21 made of HRB400φ16 steel bars are added to the top of the steel pipe column, with a layer spacing of 10cm and a longitudinal and transverse spacing of 10cm for reinforcement. C55 slightly expansive concrete is poured into the steel pipe column 1. After the subsequent beam body concrete is poured, the underwater pier steel pipe column and the beam body form a temporary consolidation system to jointly bear the subsequent construction load.

[0065] (4) According to the normal construction process, after the pre-stressing of block 0 is completed, the steel bars of block 0 are tied, and the prestressed pipes are installed. After passing the inspection, the concrete is poured. During the concrete pouring process, the deformation of the support is observed, and the concrete pouring sequence and speed are adjusted in time to ensure the safety and quality of the construction. After the concrete reaches the designed strength, the prestressing tensioning construction is carried out, and the construction of block 0 is completed. In the order of erection first and then dismantling, the support system except for the temporary consolidation of the underwater steel pipe column is dismantled in sequence.

[0066] (5) Carry out cantilever casting construction according to the design sequence, regularly inspect and maintain the support system and temporary consolidation devices, and complete the closing section construction and system conversion.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A construction method for a three-purpose integrated support system for a continuous beam of a low-tower cable-stayed bridge, characterized in that: The specific method is as follows: 1) Construction of pier cap support system Step 1: Embed steel plates and steel bars The secondary cap is widened and a steel plate is embedded on the top of the secondary cap. Pi-shaped steel bars are welded on each steel plate. The pi-shaped steel bars correspond to the designed positions of the steel pipe columns. Anti-cracking steel mesh is tied to the lower edge of the steel plate. Step 2: Install the steel pipe columns Install steel pipe columns as temporary piers on the secondary caps on both sides of the pier body, two rows in each direction, 5 columns in each row, a total of 10 columns; the distance between the center of the pier is 4-5m, the distance between adjacent piers is 8-10m, and the height is 14-18m. The steel pipe column is installed in two sections. Before the construction of the pier cap, only the lower section of the steel pipe column is constructed. After the construction, the concrete of the lower section is poured. Channel steel is used to brace and connect the steel pipe columns horizontally. The upper section of the steel pipe column is constructed before the replacement of bracing and the water collection of the cofferdam, hoisted into place and welded. The hoisting is carried out on the trestle using a 50t truck crane; Step 3: Connect the steel pipe column to the pier There are leg installation positions designed at the steel pipe columns on both sides of the pier body. Six pre-buried climbing cones are pre-buried at each leg installation position. The legs are fixed and installed through the pre-buried climbing cones. I-beams are used as the main distribution beams to be fixed on the steel pipe columns and the legs respectively. Step 4: Build the cap beam cast-in-place platform Three-piece I-beams and unloading blocks are installed on the main distribution beam. The bottom of the unloading block is fixed on the three-piece I-beam by welding to control the elevation. Double-piece I-beams in the transverse direction of the bridge are installed on the unloading block and fixed on the unloading block by welding. Longitudinal supporting I-beams are distributed and installed on the double-piece I-beams. Square timbers are installed on the supporting I-beams and bamboo plywood is laid to form a pier cap support system. 2) Construction of 0# block support system Step 1: After the pier cap is poured, remove the formwork and carry out maintenance; Step 2: Build the 0# bracket On the basis of the original longitudinal supporting I-beam, the bottom support bearing main beam is horizontally distributed; the buckle frame is erected at longitudinal and transverse intervals to the designed elevation, and the I-beam + full-paved square wood + bamboo plywood are placed on the top support to complete the construction of the 0# bracket system; 3) Construction of temporary consolidation system for box beam bottom plate Holes for consolidating steel pipe columns and pier beams are reserved on the 0# bottom plate, and steel bars are evenly arranged inside and outside the steel pipe columns. The steel bars are anchored in the steel pipe at the top of the pier for no less than 50 cm, and the anchoring length in the beam is no less than 100 cm. The steel bars at the ends of the beam are bent and welded firmly to the existing steel bars of the beam body. Shear steel bars 20 are added in the longitudinal and transverse directions of the box beam bottom plate, and 4 layers of compressive steel mesh 21 are added to the top of the steel pipe columns with a layer spacing of 10 cm and a longitudinal and transverse spacing of 10 cm for reinforcement. Concrete is poured into the steel pipe columns, and after the subsequent pouring of the beam body concrete, the underwater pier steel pipe columns and the beam body form a temporary consolidation system to jointly bear the subsequent construction loads.

2. A three-purpose support system for a continuous beam of a low-tower cable-stayed bridge, wherein a row of steel pipe columns (1) are constructed on the front and rear sides of the pier body (2) as temporary piers, and the steel pipe columns (1) are connected and reinforced by diagonal braces (3), characterized in that: The pedestal (4) at the bottom is a widened secondary pedestal. The lower end of the steel tube column (1) is constructed and fixed on the secondary pedestal. Micro-expansion concrete is arranged inside the steel tube column (1). The pier body (2) is fixed with a hanging leg (6) by pre-embedding a climbing cone (5) at a set position. A rectangular cutout is opened on the steel tube column (1) corresponding to the hanging leg (6). The main distribution beam (7) passes through the steel tube column (1) through the rectangular cutout and one end is laid on the hanging leg (6). A three-piece I-beam (8) and a drop block (9) are installed on the main distribution beam (7) above the hanging leg (6) to control the elevation. A double-piece I-beam (10) in the transverse direction of the bridge is installed on the drop block (9). Longitudinal support I-beams (11) are distributed and installed on the double-piece I-beams (10). Square wood is installed on the support I-beams (11) and bamboo plywood (12) is laid to form a pier cap support system. 0# block support system: on the basis of the longitudinal supporting I-beam (11) frame, the bottom support bearing main crossbeam (13) is horizontally distributed, and the buckle frame is vertically and horizontally spaced to the designed elevation. I16 I-beam + full-covered square wood + bamboo plywood are placed on the top support to complete the construction of the 0# block support system; Temporary consolidation system of box girder bottom plate: The 0# bottom plate is reserved with steel pipe column pier beam consolidation holes, and steel bars (15) are evenly arranged along the inside and outside of the steel pipe column (1). The steel bars are anchored in the pier top steel pipe for not less than 50 cm, and the anchoring length in the beam is not less than 100 cm.

3. According to claim 2, the three-purpose integrated support structure for the continuous beam of a low-tower cable-stayed bridge is characterized by: The main distribution beam (7) is an I45 I-beam made of Q345B material, the triple I-beam (8) is a triple I16 I-beam, the double I-beam (10) is a double I45a I-beam, the supporting I-beam (11) is an I32a I-beam, and the bottom support load-bearing main crossbeam (13) is an I20 I-beam with a horizontal spacing of 60 cm.

4. According to claim 2, the three-purpose integrated support structure for the continuous beam of a low-tower cable-stayed bridge is characterized by: The steel pipe columns (1) are arranged on the front and rear sides of the pier body (2) and the secondary cap. The secondary cap has a strip foundation of 0.8*1*13.6m added to the large and small mileages and is cast as a whole with the secondary cap. The steel bars are consistent with the secondary cap. The steel pipe columns (2) are arranged in 2 rows in front and back, 5 in each row, and a total of 10. The center of the steel pipe column (2) is 4.6m away from the center of the pier. The distance between the adjacent piers on the large and small mileage sides is 9.2m. The steel pipe columns are made of φ1000mm steel pipes with a wall thickness of 20mm and a height of 14-18m. They are installed in two sections, and one section of concrete is cast for each installed section.

5. According to claim 2, the three-purpose integrated support structure for the continuous beam of a low-tower cable-stayed bridge is characterized by: The two sections of steel pipe columns (1) are welded with HRB400 grade Φ32 reinforcing steel bars (17) inside and outside the steel pipe to form a "U"-shaped socket. The steel pipe is inserted into the socket and fixed by welding with the reinforcing steel bars (17).

6. The integrated three-purpose support system structure of the continuous beam of the low-tower cable-stayed bridge according to claim 2 is characterized by: The top of the secondary pedestal is pre-buried with a steel plate of 1200*1200*20mm. Each steel plate is welded with a π-shaped steel bar. The position and number of the π-shaped steel bars correspond to the steel pipe columns (1). The spacing between the π-shaped steel bars is 10cm. There are 10 π-shaped steel bars in total. They are inverted on the secondary pedestal. Two layers of Φ16mm anti-cracking steel mesh are tied to the lower edge of the steel plate. The vertical and horizontal spacing is 10*10cm, and the layer spacing is 10cm.

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