Construction method for in-situ replacement of piers by jacking existing bridge superstructure

Abstract

The invention provides an existing bridge superstructure jacking in-situ pier replacement construction method which comprises the steps that S1, an overwater platform is installed on the basis of an existing bearing platform and an existing pier, and pile foundation construction is conducted through the overwater platform; s2, a hanging box cofferdam is installed on the basis of pile foundation construction, and bearing platform pouring construction is conducted; s3, a temporary support is erected on the newly-built bearing platform; s4, the multiple jacking devices conduct jacking synchronously so that the load of the existing bridge can act on the temporary support; s5, the existing bridge pier is dismantled, construction of a newly-built bridge pier and a pier top support is conducted on the newly-built bearing platform, and beam falling is conducted after the newly-built bridge pier and a pier cap reach the preset strength; and S6, dismantling the temporary support after the beam is dropped. The overwater platform is installed on the basis of the existing bearing platform and the existing bridge piers, so that the construction convenience is greatly improved, the jacking process is conducted on the basis of the newly-built bearing platform, a construction platform does not need to be erected, and the construction cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge maintenance, and particularly relates to a construction method for jacking up the upper structure of an existing bridge and replacing the pier in situ. Background Art

[0002] At present, in the construction of urban rail transit in China, it often happens that the interval tunnel conflicts with the pile foundation of the existing bridge. At this time, the bridge needs to be reconstructed. There are the following two existing technologies for reconstructing the bridge: one is to demolish and rebuild; the other is pile foundation underpinning. When constructing the replacement of the bridge pier in the environmental protection area, the space under the existing bridge body is limited, and it is necessary to separately build a steel trestle as a construction platform, resulting in a large construction cost.

[0003] Therefore, it is necessary to provide an improved technical solution for the deficiencies of the above existing technologies. Summary of the Invention

[0004] The purpose of the invention is to overcome the deficiencies in the above existing technologies, and the invention provides a construction method for jacking up the upper structure of an existing bridge and replacing the pier in situ.

[0005] In order to achieve the above purpose, the invention provides the following technical solutions: A construction method for jacking up the upper structure of an existing bridge and replacing the pier in situ, comprising: Step S1, installing a water platform based on the existing bearing platform and the existing pier, and carrying out pile foundation construction through the water platform; Step S2, installing a caisson cofferdam based on the pile foundation construction, and carrying out the construction of pouring the bearing platform through the caisson cofferdam, and pouring the existing pier and the newly built bearing platform into one body; Step S3, erecting temporary supports on the newly built bearing platform to support the existing bridge, and arranging a plurality of jacking devices above the existing pier; Step S4, synchronously jacking the plurality of jacking devices, and padding steel plates between the existing bridge and the temporary support as the jacking devices jack up, so as to act the load of the existing bridge on the temporary support; Step S5, demolishing the existing pier, carrying out the construction of the newly built pier and the pier top bearing on the newly built bearing platform, and carrying out beam lowering after the newly built pier and the pier cap reach the preset strength; Step S6, demolishing the temporary support after beam lowering.

[0006] Preferably, the temporary support is designed by calculating the load of the bridge deck system. The temporary support at the same support point includes two support frames located on both sides of the existing pier corresponding to the bridge alignment; Each support frame includes 4 double-leg I-beams as columns for bearing, and each column is welded to the steel plate embedded in the bearing platform. Channels are arranged between the columns as lacing bars to be connected into a unified whole, and the two support frames are fixed by flat connecting rods.

[0007] Preferably, in step S4, first lift the position of the bridge near the abutment. After the lifting device is in place, perform a preliminary lift first. Before the preliminary lift, remove or cut the connection bolts of the bearing above the existing pier.

[0008] Preferably, in step S5, drill holes in the existing pier and inject an expanding agent into the holes. The expanding agent causes the existing pier to burst through expansion. Use a pneumatic pick to remove the cracked concrete, and demolish the existing pier to the new pile cap in multiple layers longitudinally.

[0009] Preferably, in step S5, erect a fastener-style steel pipe support on the new pile cap, tie the pier body and pier cap steel bars according to the design drawings, and tie the embedded steel bars for the pier top bearing when tying the pier cap steel bars; The pier body formwork is spliced using modular steel formwork, and the gap between the pier body formwork and the new pile cap is sealed with mortar.

[0010] Preferably, in step S6, repair the shell platform before lowering the beam. Chisel the surface and implant steel bars on the front and side of the abutment, and set up formwork for pouring a layer of concrete on the front and side of the shell.

[0011] Preferably, the caisson cofferdam includes a suspension system, side plates, internal supports, and a bottom plate; Among them, holes corresponding to the pile foundations are provided on the bottom plate. After the side plates and the bottom plate are spliced, a trough-shaped structure corresponding to the pile cap is formed. Internal supports are provided along the upper edge of the inner wall of the side plates. The suspension system is arranged on the existing pier, and the suspension system is correspondingly hoisted on the internal supports.

[0012] Preferably, the suspension system includes a crossbeam distributed in a grid pattern between the existing pier and the existing bridge. A backing plate corresponding to the existing bridge is provided above the crossbeam, and the part of the crossbeam extending out of the existing pier is hoisted with an internal support through a chain block.

[0013] Preferably, a plurality of anti-floating supports are provided between the internal support and the crossbeam.

[0014] Beneficial effects: Install the water platform based on the existing pile cap and existing pier, thereby greatly improving the construction convenience. Perform the lifting process based on the new pile cap, so that there is no need to erect a construction platform, reducing the construction cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The schematic diagrams in the specification accompanying this application, which form a part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. Among them: Figure 1 is the installation schematic diagram of the water platform in the specific embodiment provided by the present invention; Figure 2Schematic diagram of the installation of the wedge in the specific embodiment provided by the present invention; Figure 3 Schematic diagram of the installation of the caisson cofferdam in the specific embodiment provided by the present invention; Figure 4 Top view sketch of the caisson cofferdam in the specific embodiment provided by the present invention.

[0016] In the figure: 1, existing bearing platform; 2, existing bridge; 3, lower foundation frame; 4, lower extension frame; 5, upper foundation frame; 6, upper extension frame; 7, lower pile position frame; 8, upper pile position frame; 9, wedge; 10, suspension cable; 11, bored pile; 12, side plate; 13, anti-floating support; 14, lifting beam; 15, internal support; 16, existing pier; 901, bottom plate; 902, linkage rod; 903, support rod; 904, support column. Detailed implementation manners

[0017] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0018] In the description of the present invention, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. The terms "connected" and "coupled" used in the present invention should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate component. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific situations.

[0019] Next, the present invention will be described in detail with reference to the drawings and in combination with the embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0020] As Figures 1-4As shown, a method for replacing the piers of an existing bridge superstructure by lifting the original position includes: step S1, installing a water platform based on the existing cap 1 and the existing bridge pier 16, and performing pile foundation construction through the water platform; installing two layers of water platforms from bottom to top, wherein the lower layer of the water platform is lowered into the water and positioned on the existing cap 1 after being assembled, and the upper layer of the water platform is fixed on the existing bridge pier 16 by a wedge 9; after the steel casing is hoisted in place, it is embedded into the riverbed by a vibrating hammer, and the steel casing is calibrated and leveled. The casing is fixed to the lower water platform to form a steel cofferdam; concrete is poured between the two layers of steel casing to separate the inner area of the steel casing from the river water outside; the drilling rig is located on the existing bridge deck to drill bored piles 11, and a floating mud pool is set on the lower water platform to store the mud generated by the construction of the bored piles 11; after drilling to the designed depth, the hole is cleaned, and the steel cage and steel cylinder are lowered to cast the pile foundation. After the pouring is completed, the steel casing is hoisted out in turn, and the water platform is dismantled from bottom to top.

[0021] Step S2, the box cofferdam is installed based on the pile foundation. The box cofferdam includes a suspension system, side panels 12, inner supports 15 and bottom plates 901. The box cofferdam can not only play the role of a cofferdam to isolate the river water during the construction process, but also serve as a template for the construction of the pedestal, which greatly saves the construction cost and improves the construction efficiency. The pedestal is cast through the box cofferdam, and the existing bridge pier 16 and the newly built pedestal are cast as one.

[0022] Step S3, set up temporary supports on the newly built abutment to support the existing bridge 2, and set up multiple jacking devices above the existing piers 16; during the pier replacement process, it is necessary to set up temporary supports on the newly built abutment frame (the existing piers 16 are horizontal and front and back), transfer the loads of steel beams, bridge deck systems, etc. to the temporary supports, and then remove the existing piers 16; temporary supports are designed by calculating the load of the bridge deck system, and the temporary supports at the same support point include two support frames located on both sides of the existing piers 16 corresponding to the direction of the bridge; each support frame includes 4 double-legged I-beams as columns to bear the load, each column is welded to the pre-buried steel plate of the abutment, and 150mm channel steels are set between the columns as tie bars to connect them into a unified whole, and the two support frames are fixed with 150mm channel steels as flat connecting rods.

[0023] In this embodiment, according to the size of the bridge, a set of jacking devices can be set up for each pier of a half-width beam, so as to adopt a half-width integral lifting bridge. In order to reduce the occurrence of cracks in the bridge deck during the lifting process, the bridge is first lifted near the abutment. After the jacking device is in place, it is first pre-jacked. Before pre-jacking, the connecting bolts of the support above the existing pier 16 are removed or cut off, that is, the two free ends of the steel beam (at the abutment) are lifted successively, and then the middle pier position is lifted.

[0024] The jack used in the jacking device is a flat jack of model YBD400-18. When lifting, the jacks must lift at the same rate to ensure that the upper steel beam and the bridge deck concrete are not damaged by the shear force caused by different jacking speeds.

[0025] Step S4: Synchronously jack up multiple jacking devices. After all preparatory work is completed, each jack is pre-jacked to ensure that each jack has contacted the bottom of the steel beam and is evenly stressed before the formal jacking work starts. Before pre-jacking, the connecting bolts of the existing bearings should be removed or cut off.

[0026] As the jacking device jacks up, steel plates are padded between the existing bridge 2 and the temporary support to transfer the load of the existing bridge 2 to the temporary support; the beam is jacked up in 4 stages, with a jacking amplitude of 5 mm for each stage and a total jacking height of 20 mm. To ensure the safe jacking up of the steel beam, steel plates are promptly padded into the gaps at the top of the support after each stage of lifting. The project department uses steel plates with thicknesses such as 5 mm, 10 mm, and 20 mm, so that steel plates can be promptly padded or replaced after each stage of lifting to ensure contact with the beam body.

[0027] Step S5: After the jacking is completed, the existing pier 16 is demolished, and the construction of the new pier and the pier top bearing is carried out on the new bearing platform. After the new pier and pier cap reach the preset strength, the beam is lowered; when lowering the beam, the steel beam is first jacked up (2 mm) with a jack. The process of lowering the beam is also divided into 4 stages, with each stage being 5 mm. Similar to the jacking up of the beam body, a scale is used to observe the lowering height of the beam body at the position of each jack during the process of lowering the beam. After each of the 4 jacks at each stage has completed the lowering height of that stage, the next stage of lowering the beam is carried out until the steel beam completely falls onto the installed bearing.

[0028] Step S6: After the beam is lowered, the temporary support is demolished. The demolition sequence should be to first demolish the cross beam from top to bottom, then use the chain hoist set at the steel beam to lift the cross beam to the bearing platform, and then cut and remove the lattice bars between the columns. Finally, cut the weld at the root of the column to separate the whole column from the bearing platform, and then slowly lift out each component with a crane.

[0029] In an alternative embodiment, in step S5, the existing pier 16 is demolished by drilling holes in the existing pier 16 and placing a silent expanding agent in the holes (i.e., "static blasting"). Drill holes in the existing pier 16 and inject the expanding agent into the holes. As the mixed breaking agent flows in, the slurry directly enters the wellbore, and the hydration reaction is accompanied by crystal deformation, generating a huge expansion pressure (radial compressive stress and circumferential tensile stress) applied to the hole wall over time.

[0030] The expanding agent causes the existing pier 16 to burst through expansion. Use a pneumatic pick to remove the cracked concrete and cut the exposed steel bars. Demolish the existing pier 16 to the new bearing platform in multiple layers along the longitudinal direction.

[0031] The pier body is demolished in 6 layers, with the demolition height of each layer being 1 m and the total height being 6 m.

[0032] In an alternative embodiment, in step S5, a fastener-style steel pipe support is erected on the newly built bearing platform, and the pier body and pier cap steel bars are tied according to the design drawings. When tying the pier cap steel bars, the embedded steel bars for the pier top bearing are tied. The pier body formwork is spliced using modular steel formwork. The surface of the formwork is required to be straight and smooth, the joints are tight, and a double-sided adhesive tape is pasted between the formwork gaps. When erecting the formwork, the outside of the formwork bottom is filled with mortar, and the inside is plastered with mortar for sealing to ensure tightness and no leakage of mortar. The pier body formwork and the newly built bearing platform are sealed with mortar.

[0033] In step S6, the shell platform is repaired before the beam is lowered. The front and side surfaces of the abutment are roughened and steel bars are planted, and formwork is set up on the front and side surfaces of the shell to pour a layer of C40 concrete with a thickness of 20 cm, thereby strengthening the abutment.

[0034] In an alternative embodiment, the caisson cofferdam includes a suspension system, side plates 12, and a bottom plate 901; Among them, holes corresponding to the pile foundations are provided on the bottom plate 901, and the holes are adapted to the pile foundation points and diameters. First, the side plates 12 and the bottom plate 901 are assembled. After the side plates 12 and the bottom plate 901 are spliced, a trough-shaped structure corresponding to the bearing platform is formed. Then, the cofferdam is lowered through the holes to the set position. An internal support 15 is provided along the upper edge of the inner wall of the side plates 12, and the suspension system is arranged on the existing pier 16 and is correspondingly hoisted on the internal support 15.

[0035] The side plates 12 adopt double-steel wall side plates 12. The vertical spacing of the panel skeletons is 100 mm channel steel with a spacing of 80 cm. Angle steel with a spacing of 50 cm and a size of 100 mm is arranged between the vertical channel steels and welded to the two side channel steels. The outer panel of the skeleton is made of 6 mm steel plate. The inner and outer panels are connected into a whole in the form of triangular supports by 100 mm channel steel. The size of the inner side plate 12 is the same as that of the bearing platform and serves as the side formwork in addition to the cofferdam during the casting of the bearing platform concrete.

[0036] The transverse bridge skeleton of the cofferdam bottom plate 901 consists of 4 I-beams with a size of 356 mm, and the longitudinal bridge skeleton consists of 150 mm channel steel with a spacing of 0.5 m. The bottom plate 901 panel is welded to the skeleton with 6 mm steel plate. To ensure the gap of the pile foundation reserved holes on the bottom plate 901, the steel plate of the bottom plate 901 is cut and welded on-site by measuring the specific position of the pile foundation. After the cofferdam is installed on the water surface, it is lowered into the water. After the position of the cofferdam is ready, underwater concrete with a thickness of 65 cm is poured at the bottom plate 901 for bottom sealing. The upper surface of the concrete after bottom sealing is the bottom surface of the newly built bearing platform. After the concrete reaches the required strength and the internal water is pumped out, the steel bars of the bearing platform can be tied.

[0037] In this embodiment, the suspension system includes a crossbeam 14 distributed in a cross shape between the existing bridge pier 16 and the existing bridge 2. A backing plate corresponding to the existing bridge 2 is provided above the crossbeam 14. The part of the crossbeam 14 extending out of the existing bridge pier 16 is hoisted by a chain block to support the internal support 15, so that the height of the caisson cofferdam can be adjusted according to the actual situation. A plurality of anti-floating supports 13 are provided between the internal support 15 and the crossbeam 14. Four vertical I-beams with a size of 356 mm are welded to the crossbeam 14 at the upper opening of the cofferdam box as anti-floating supports 13, so that the buoyancy of the river water on the cofferdam box is transmitted to the crossbeam 14, and the crossbeam 14 is fixed to the existing pier body, thus ensuring that the cofferdam box will not float up.

[0038] In an alternative embodiment, 4 pile foundations are correspondingly arranged for each newly-built bearing platform, and the four pile foundations corresponding to the same bridge pier are constructed in sequence according to the construction sequence.

[0039] The lower water platform includes a lower foundation frame 3 and a lower extension frame 4. Both the lower foundation frame 3 and the lower extension frame 4 are assembled by bolts with I-beams. The lower foundation frame 3 is distributed in a cross shape around the existing bridge pier 16. The internal space of the lower foundation frame 3 is adapted to the existing bridge pier 16 to ensure the stability of the lower foundation frame 3. The lower foundation frame 3 is correspondingly supported on the existing bearing platform 1 by support members, and the support members can be studs. The lower extension frame 4 is fixed to the parts of the upper foundation frame 5 extending outwards on both sides (in the bridge mileage direction) of the existing bearing platform 1 and extends to the corresponding pile positions at both ends of the existing bearing platform 1. Upper pile position frames 8 corresponding to the steel casing are provided at both ends of the lower extension frame 4. The upper pile position frames 8 are square frames surrounded by I-beams corresponding to the outer steel casing, so as to limit the steel casing and ensure the stability of the steel casing during construction.

[0040] The upper water platform includes an upper foundation frame 5 and an upper extension frame 6. The shapes of the upper foundation frame 5 and the lower foundation frame 3, and the upper extension frame 6 and the lower extension frame 4 are the same in the longitudinal projection, and are also assembled by bolts with square steel or I-beams. The upper foundation frame 5 is distributed in a cross shape around the existing bridge pier 16. A plurality of suspension cables 10 are provided above the upper foundation frame 5. The upper ends of the suspension cables 10 are connected to wedges 9, and the wedges 9 are correspondingly inserted between the existing bridge pier 16 and the existing bridge 2. The suspension cables 10 can be iron chains and are connected to the upper foundation frame 5 through chain blocks, so that the height can be adjusted according to actual needs. The upper extension frame 6 is fixed to the parts of the upper foundation frame 5 extending outwards on both sides (in the bridge mileage direction) of the existing bearing platform and extends to both ends (in the bridge transverse direction) of the existing bearing platform 1. Upper pile position frames 8 corresponding to the lower pile position frames 7 are provided at both ends of the upper extension frame 6, so as to assist in positioning the steel casing and the drill rig and ensure the stability of the construction.

[0041] In addition, the wedge 9 is detachably installed between the existing pier 16 and the existing bridge 2, and specifically includes a bottom plate 901, a support rod 903, and a linkage rod 902. The materials of the bottom plate 901, the support rod 903, and the linkage rod 902 are all high-strength steel. One end of the bottom plate 901 extends between the existing pier 16 and the existing bridge 2, thereby forming a support point to support the upper water platform. One end of the linkage rod 902 is hinged to the middle and rear part of the bottom plate 901. The length of the linkage rod 902 is greater than the gap width between the existing pier 16 and the existing bridge 2. One end of the support rod 903 is hinged to the middle of the linkage rod 902, and the other end extends out of the outer periphery of the existing pier 16 and is connected to the suspension cable 10. Under the traction of the suspension cable 10, the support rod 903 drives the linkage rod 902 upward with the edge of the bottom plate 901 as the fulcrum, and the linkage rod 902 squeezes the lower surface of the existing bridge 2, thereby forming a stable connection relationship to ensure the stability of the support.

[0042] Anti-slip patterns are provided at the upper end of the linkage rod 902. A support column 904 corresponding to the gap width between the existing pier 16 and the existing bridge 2 is provided at one end of the bottom plate 901 extending between the existing pier 16 and the existing bridge 2. The support column 904 prevents the support failure caused by the upward rotation of the bottom plate 901 under the traction of the suspension cable 10. A bent portion that turns downward is provided at the outer periphery of the existing pier 16 where the bottom plate 901 extends, and the bent portion is fixed to the outer wall of the existing pier 16 through anchor bolts, thereby ensuring the stability of the bottom plate 901.

[0043] Furthermore, the steel casing is a double-layer cylinder. The same layer of the steel casing can include multiple segments spliced with each other. The two adjacent segments up and down are fixed by welding. An inverted U-shaped clamping seat corresponding to the lower expansion frame 4 is provided on the outer wall of the outer layer of the steel casing, and the inverted U-shaped clamping seat is fixed to the outer wall of the steel casing by welding. A hinged segment corresponding to the inner wall of the steel casing is hinged on the lower pile position frame 7. Multiple hinged segments are evenly distributed around the circumference of the steel casing. The hinged segment extends into the inverted U-shaped clamping seat to drive the hinged segment to rotate downward and press against the inner wall of the steel casing under the self-weight of the steel casing, thereby ensuring that the steel casing will not shift circumferentially. The hinged segment is hinged to the lower pile position frame 7 through a hinge shaft, and the hinged segment is customized according to the measured position to avoid the construction difficulty caused by the driving error of the steel casing.

[0044] After the double-layer steel casing is driven, a connecting rod is welded to the upper end of the double-layer steel casing to ensure their stability.

[0045] In an optional embodiment, the steel casings are installed in the order of large first and then small. After the outer layer of the steel casing is hoisted in place, it sinks into the riverbed by its own gravity or is driven and embedded to a preset height by a vibrating hammer. Then, the distances between each inverted U-shaped clamping seat and the corresponding lower pile position frame 7 are measured, and the length design and installation of the hinged segments are carried out according to the measurement results. After the hinged segments are installed, the outer layer of the steel casing is driven and embedded to the specified elevation; The number of inverted U-shaped clamping seats is not less than 4, and the 4 inverted U-shaped clamping seats correspond to 4 hinge segments one by one. After lowering the inner steel casing, concrete pouring is carried out after the inner steel casing is embedded in place. Before the underwater concrete pouring of the pile foundation, the conduit should be trial-installed and its sealing performance should be detected to ensure that the conduit is well sealed and prevent slurry leakage during the concrete pouring. The pile foundation should be continuously poured to prevent pile breakage, and at the same time, the pouring speed should be controlled to avoid the floating of the steel reinforcement cage. Records should be made during the concrete pouring of the pile foundation to timely master the elevation of the concrete surface and calculate the buried depth of the conduit.

[0046] After the pile foundation pouring is completed and the pile foundation concrete has solidified, the steel casings are successively lifted out by a vibrating hammer. When the vibrating hammer is working, it should ensure vertical displacement and is strictly prohibited from having large swings in the horizontal direction to avoid disturbing the newly poured pile foundation.

[0047] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are within the scope of the claims of the present invention awaiting approval.

Claims

1. A construction method for jacking up the superstructure of an existing bridge and replacing the bridge pier at the original position, characterized in that, Including: Step S1: Install a water platform based on the existing bearing platform and existing bridge pier, and carry out pile foundation construction through the water platform; Step S2: Install a caisson cofferdam based on the pile foundation construction, and carry out the casting construction of the bearing platform through the caisson cofferdam, and cast the existing bridge pier and the newly built bearing platform into one body; Step S3: Set up temporary supports on the newly built bearing platform to support the existing bridge, and set up multiple jacking devices above the existing bridge pier; Step S4: Synchronously jack up multiple jacking devices, and pad steel plates between the existing bridge and the temporary support as the jacking devices jack up, so as to apply the load of the existing bridge on the temporary support; Step S5: Demolish the existing bridge pier, carry out the construction of the newly built bridge pier and pier top bearing on the newly built bearing platform, and carry out beam lowering after the newly built bridge pier and pier cap reach the preset strength; Step S6: Demolish the temporary support after beam lowering.

2. The construction method for replacing the pier at the original position by jacking up the superstructure of an existing bridge according to claim 1, characterized in that, Design the temporary support by calculating the load of the bridge deck system. The temporary support at the same support point includes two support frames located on both sides of the existing bridge pier corresponding to the bridge alignment; Each support frame includes 4 double-leg I-beams as columns for load-bearing. Each column is welded to the steel plate embedded in the bearing platform. Channels are arranged between the columns as lacing bars to be connected into a unified whole, and the two support frames are fixed by parallel connection rods.

3. The construction method for replacing the pier at the original position by jacking up the superstructure of an existing bridge according to claim 1, characterized in that, In Step S4, first jack up the position of the bridge close to the abutment. After the jacking device is in place, pre-jack first. Before pre-jacking, disassemble or cut off the connecting bolts of the bearing above the existing bridge pier.

4. The construction method for jacking up the upper structure of an existing bridge and replacing the bridge pier at the original position according to claim 1, characterized in that, In Step S5, drill holes in the existing bridge pier and inject an expanding agent into the holes. The expanding agent expands to burst the existing bridge pier, and use a pneumatic pick to remove the cracked concrete, and demolish the existing bridge pier to the newly built bearing platform in multiple layers longitudinally.

5. The construction method for jacking up the upper structure of an existing bridge and replacing the bridge pier at the original position according to claim 1, characterized in that, In Step S5, set up a fastener-type steel pipe support on the newly built bearing platform, bind the steel bars of the pier body and pier cap according to the design drawings, and bind the embedded steel bars of the pier top bearing when binding the pier cap steel bars; The pier body formwork is spliced with modular steel formwork, and the pier body formwork and the newly built bearing platform are sealed with mortar.

6. The construction method for replacing the pier at the original position by jacking up the superstructure of an existing bridge according to claim 1, characterized in that In Step S6, repair the shell platform before beam lowering, roughen and implant steel bars on the front and side of the abutment, and set up a casting formwork to pour a layer of concrete on the front and side of the shell.

7. The construction method for replacing the pier at the original position by jacking up the superstructure of an existing bridge according to claim 1, characterized in that, The caisson cofferdam includes a suspension system, side plates, internal supports and a bottom plate; Among them, holes corresponding to the pile foundations are provided on the bottom plate. After the side plates and the bottom plate are spliced, a trough-shaped structure corresponding to the bearing platform is formed. Internal supports are provided on the upper edge of the inner wall of the side plates. The suspension system is arranged on the existing bridge pier, and the suspension system is correspondingly hoisted on the internal supports.

8. The construction method for replacing the pier at the original position by jacking up the superstructure of an existing bridge according to claim 7, characterized in that, The suspension system includes a crossbeam distributed in a cross shape between the existing bridge pier and the existing bridge. A cushion plate corresponding to the existing bridge is provided above the crossbeam. The part of the crossbeam extending out of the existing bridge pier hoists the internal support through a chain block.

9. The construction method for jacking up the superstructure of an existing bridge and replacing the bridge pier at the original position according to claim 8, characterized in that, Multiple anti-floating supports are provided between the internal support and the crossbeam.

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