A reverse construction method for cast-in-place beams of side piers of a cable-stayed and rotating bridge

Abstract

A reverse-construction method for the cast-in-place side piers of a cable-stayed, rotating bridge involves constructing the pier columns, which are supported by both the main bridge's cast-in-place beams and the approach bridge's cast-in-place beams, in two stages. The first stage begins with construction to the base elevation of the main bridge's cast-in-place beam pad stone. During this initial construction phase, reinforcement is reserved for the approach bridge's side pier columns during the second stage. Once the initial concrete strength reaches 85% of the design strength, support for the approach bridge's cast-in-place beams is constructed. Precautions are taken to reserve tensioning notches for the main beam's joint prestressing, preventing temporary supports from encroaching on the original design support locations. The cast-in-place beams of the main bridge are constructed in accordance with the design requirements, with scaffolding to complete the construction of the cast-in-place sections at the side piers and the closure blocks after rotation. After the concrete strength of the closure blocks meets the requirements, the tensioning grouting and anchoring of the closure prestressed steel strands are completed. Then, according to the pier construction requirements, the side piers of the approach bridge are raised, the cushion stones and the pre-embedded supports are completed. After the concrete strength of the side piers and supports of the approach bridge meets the standards, the permanent supports are installed, the temporary support columns of the approach bridge are removed, and the cast-in-place beams of the approach bridge are completely placed on the permanent supports, completing the system conversion of the cast-in-place beams of the approach bridge.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction, and in particular relates to a reverse construction method for cast-in-situ beams of a side pier of an oblique-stayed and rotating bridge. Background Art

[0002] The existing construction method for similar side pier platforms on cable-stayed, rotating bridges is as follows: ① The side piers with elevated platforms are constructed in two stages. The first stage is to construct them flush with the top of the lower pier of the main bridge's cast-in-place beam. This completes the cast-in-place section at the side pier and the closure block after the rotation. Once the concrete strength of the closure block meets the required requirements, the prestressed steel tendons are tensioned, grouted, and anchored. The approach bridge's side piers are then raised and the cast-in-place approach bridge beams are constructed according to the pier column construction requirements. This method is well suited for the construction of side piers and beams with different height differences. However, this conventional sequential construction method presents the following issues: ① Sequential construction requires a long construction cycle, making it difficult to meet the construction schedule requirements of short, frequent, and fast-paced projects. ② The leasing period for machinery, equipment, and circulating materials is long, resulting in low utilization and high construction costs. ③ The construction cycle is extended, increasing project management costs. This reverse-sequential construction method, which breaks with conventional procedures, is particularly suitable for pier and beam construction projects with tight deadlines and side pier designs with elevated piers. Summary of the Invention

[0003] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a method for reverse construction of cast-in-situ beams of the side piers of a cable-stayed swivel bridge, which adjusts the traditional construction sequence from bottom to top, from pier to beam, and main first and secondary later, thereby avoiding the long construction time required when using conventional construction methods. The use of temporary piers realizes the supporting function of the cast-in-situ beams, and while realizing the construction of the adjacent cast-in-situ beams of the swivel main beam first, it also meets the space for joint closing operations required for the subsequent construction of the swivel main beam. The original sequential construction is adjusted to parallel construction, and the construction tasks on some key lines are adjusted to non-key lines, shortening the length of the key lines, improving the effective utilization rate of mechanical equipment, shortening the rental period of mechanical equipment and materials, and reducing the cost of project management. Moreover, the application is more in line with the design intent, which can fully reflect the true meaning of the designer setting the joint closing section in the early stage of bridge design.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A method for reverse construction of cast-in-situ beams of a side pier of an oblique-stayed swivel bridge is characterized by comprising the following steps:

[0006] Step 1: Install a spiral pipe support column filled with concrete at the top of the side pier, a flange and a stiffening plate of the spiral pipe support column, an H-shaped steel for unloading, a wedge-shaped block at the bottom of the beam at the top of the support column, and a template for the wedge-shaped block at the bottom of the beam;

[0007] Step 2: By assembling the above components according to the construction sequence, the pier columns with high and low piers are constructed in two stages; in the first stage, the pier columns are constructed to a position flush with the top of the low pier of the main beam, avoiding the position of the prestressed tensioning notch of the main beam joint, and the plane position and elevation of the temporary support column of the cast-in-situ beam of the approach bridge are set at the top of the pier on the side of the approach bridge;

[0008] Step 3. According to the elevation of the top of the side pier of the approach bridge, cut a 609x16mm spiral tube as the support column of the cast-in-place beam of the approach bridge, set a t=10mm, 900x900mm steel plate on the top surface of the support column as the flange of the support column, and evenly set 8 150x150mm, t=10mm triangular steel plates around the flange and the support column as stiffening plates of the flange. Intermittent welding is used between the flange steel plate and the supporting spiral tube, and full welding is used between the stiffening plate, flange and spiral tube; a circular hole with a diameter of 200mm is opened in the center of the flange as the feeding hole and vibration hole for pouring concrete for the support column, and 4 air outlets with a diameter of 10mm are evenly opened on the flange steel plate at a position 5cm away from the spiral tube wall of the support column. Pour C50 micro-expansive concrete into the spiral tube from the center hole of the flange and vibrate it densely;

[0009] Step 4: Cut six 900mm long 25H-shaped steels and install three on the top of each support column flange. Install the H-shaped steels along the bridge direction, centering them on the top of the steel pipe support columns and keeping them close together. Install square wood and bamboo plywood on the top of the H-shaped steels as the outer formwork for the wedge block at the bottom of the beam.

[0010] Step 5: Construct the cast-in-place sections of the main bridge side piers and the cast-in-place beams of the approach bridge simultaneously on the supports according to the cast-in-place beam construction method. After the main beam rotation is completed, construct the main bridge closure section on the supports. After the concrete strength of the closure section reaches the design strength, construct the main beam closure prestressed tendons, and perform grouting on the prestressed tendons and seal the tensioning notches.

[0011] Step 6: Install the high pier steel bars and formwork on the approach bridge side of the side pier top, install the approach bridge pad stone steel bars, pour the high pier concrete on the approach bridge side, and after the concrete strength of the high pier on the approach bridge side reaches 2.5 MPa, install the approach bridge pad stone steel bars, install the bearing embedded bolts, pour the pad stone concrete, and install the spherical bearing on the approach bridge side after the concrete strength meets the requirements;

[0012] Step 7: Use gas cutting to cut the H-shaped steel sections one by one along the web of the top of the temporary support column to separate the H-shaped steel sections from the web. Pull out the cut steel sections one by one from between the bottom of the beam and the temporary support column. Remove the square timber and formwork at the wedge block position at the bottom of the beam at the temporary support. Support the cast-in-place beam on the permanent support to complete the system conversion.

[0013] The lower end of the temporary support column of the cast-in-place beam of the approach bridge is a steel pipe support filled with C50 slightly expansive concrete. The top surface of the steel pipe support column is flush with the top of the side pier of the approach bridge. A flange and a stiffening rib are set on the top surface of the steel pipe support column. A 25 I-steel is installed on the top surface of the flange, and a 20 I-steel is installed on the 25 I-steel. Thick bamboo plywood is laid on the 20 I-steel, and a wedge-shaped block of the beam bottom is erected on the thick bamboo plywood.

[0014] 16 threaded steel bars are arranged in the wedge-shaped block at the bottom of the beam.

[0015] The beneficial effects of the present invention are:

[0016] The present invention is designed to adapt to cast-in-situ box beams with inner transverse diaphragms. Compared with conventional steel pipe frame construction, it has the advantages of short construction period, fast construction speed, low investment in manpower, material and financial resources, high material turnover utilization rate, and convenient operation.

[0017] 1. Taking the construction of cast-in-situ box girders of the main bridge of the Chengxiang River Bridge on National Highway 241 as an example, this cast-in-situ box girder with inner transverse diaphragms was initially constructed by erecting steel pipe frames, but the economic benefits were significantly improved by adopting this improved inner sliding beam construction method.

[0018] The manpower input has been reduced, and each beam section has been reduced by about 30 working days. The labor wage for each working day is calculated at 260 yuan, and each beam section can save about 7,800 yuan in labor costs. The main bridge of the Chengxiang River Super Bridge has a total of 4 T-structures, and there are a total of 72 beam sections that can be constructed using this method, which can save about 560,000 yuan in labor costs.

[0019] The investment in temporary steel bar materials is reduced. When conventionally setting up steel pipe racks, horse stool bars need to be installed at the bottom of each steel pipe rack. Each beam section requires approximately 260 kg of horse stool bars. Calculated at 6,000 yuan per ton of steel, there are a total of 72 beam sections, which saves approximately 112,000 yuan in steel bar costs for temporary construction.

[0020] The construction period was shortened by 2.5 days per beam segment. A total of 72 beam segments were constructed using the modified internal sliding beams across four main piers, saving a total of six months. Based on the rental cost of 40,000 yuan per 6015 tower crane, this saved 240,000 yuan. Furthermore, the rental costs of other small machinery and materials, as well as other indirect costs, are significant expenses.

[0021] 2. Compared with conventional steel pipe rack construction, this method avoids the tedious construction steps of frequent steel pipe rack erection and dismantling, material transportation, and other complex processes. This significantly shortens the construction time for each beam segment. The cast-in-place box girders of the Chengxiang River Bridge were initially constructed using steel pipe racks, with each segment taking approximately 15 days to construct. However, the use of this modified internal sliding beam construction method reduced the construction time for each beam segment to 12.5 days, significantly improving the overall construction schedule.

[0022] In the early stages of construction, steel pipe racks were erected on the reinforcement of the base plate. During the pouring of the box girder top slab concrete, the base plate concrete had not yet solidified, causing significant disturbance to the concrete. Consequently, the pouring speed had to be slowed down. Due to the large pouring area, the pouring was discontinuous, resulting in numerous cold joints that affected the concrete's appearance. However, with this modified internal sliding beam construction method, the entire box girder top slab load is transferred to the completed beam sections and hanging basket via the sliding beam. This prevents disturbance to the floor concrete during concrete pouring, while also accelerating the pouring speed, avoiding the formation of cold joints and improving the concrete's appearance.

[0023] In summary, the present invention is used to construct continuous beams with inner transverse beams, and the front and rear inner formwork of the transverse beams are constructed by means of slideways. The inner formwork is installed and removed quickly, the quality of concrete is guaranteed, the construction is safe and reliable, the construction efficiency is improved, the application scope of the hanging basket construction is expanded, and the social benefits are obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Flowchart of the present invention.

[0025] Figure 2 This is a schematic diagram of the present invention.

[0026] Figure 3 This is a diagram of the construction sections of the side piers of the present invention;

[0027] Figure 4 This is a schematic diagram of the plane positions of the supports, blocks and temporary buttresses at the side piers of the present invention.

[0028] Figure 5 This is a diagram of a temporary buttress on the top of a side pier according to the present invention.

[0029] Figure 6 This is a schematic diagram of the temporary support column of the cast-in-place beam of the approach bridge, with the lower end of the steel pipe support filled with C50 slightly expansive concrete.

[0030] Figure 7 Schematic diagram of setting 16 threaded steel bars in the wedge block at the bottom of the beam. DETAILED DESCRIPTION

[0031] The present invention is further described below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0032] like Figure 1 、 2 As shown, a method for reverse construction of cast-in-situ beams of a side pier of a tilted and rotated bridge is characterized by comprising the following steps:

[0033] Step 1: Construction Preparation

[0034] (1) Based on the actual conditions of the cast-in-place beam construction site, a qualified design unit is commissioned to design the cast-in-place beam support system and temporary support columns of the approach bridge, calculate the strength, rigidity and stability of the support system, and ensure the safety and reliability of the cast-in-place beam support construction.

[0035] (2) The technical director shall organize the technical staff to study the construction drawings and specifications together. After the construction plan is approved, the technical staff and relevant management staff shall be organized to study the core content of the plan together, master the key points of construction control, and complete the briefing work for the workers.

[0036] (3) Determine the resource allocation and on-site preparation of personnel, materials, and machinery based on the construction plan.

[0037] Step 2: First construction of side piers;

[0038] First, divide the pier column construction sections, and construct the shadow part first to meet the bottom elevation of the main beam support pad stone to meet the main beam construction needs. The pier on the approach side will be raised according to the design requirements and the steel bars and joints will be reserved. Figure 3 .

[0039] Step 3: Setting up temporary supporting piers for cast-in-situ beams of approach bridge;

[0040] The longitudinal position of the temporary support column in the mileage direction is kept consistent with the permanent support line of the cast-in-situ beam of the approach bridge. The horizontal position is as close to the permanent support position as possible without affecting the prestressing construction of the main beam, so as to ensure the optimal stress state of the cast-in-situ beam when supported by the temporary support column. Taking a pier column of this project as an example, according to the working space and position of the main beam prestressing construction on the pier column, the temporary support column is set horizontally at a position with a 2.5m offset. Figure 4 shown.

[0041] The temporary support column system consists, from top to bottom, of wedge-shaped blocks at the bottom of the beam, supporting timbers, removed H-shaped steel beams, and concrete-filled steel pipe support columns. To increase the bearing capacity of the steel pipe support columns, C50 slightly expansive concrete was poured into the columns, and stiffening plates were added between the columns and the flange steel plate brackets at the top of the columns.

[0042] Temporary support steel pipe columns utilize Ø609×16 spiral tubes. These columns are placed on top of the first completed pier. To prevent the steel pipe support columns from sliding, they are welded to the embedded rebar at the pier top. The top surface of the steel pipe support columns is aligned with the top of the approach piers to facilitate later removal of the temporary support columns. Flanges and stiffening ribs are installed at the top of the spiral tubes to enhance the support performance of the steel pipe column flanges. Concrete pouring within the steel pipe support columns requires a dense, shrink-free structure. A feed hole is located in the center of the top base plate to facilitate vibration and degassing during concrete pouring, ensuring the density of the concrete within the steel pipe columns.

[0043] Step 4: Construction of cast-in-place beams of approach bridge;

[0044] (1) After the construction of the temporary piers is completed, the cast-in-situ support formwork system for the approach bridge is immediately set up. The cast-in-situ beam support adopts the Z-type disc-type support for cast-in-situ construction. On the top of the support, the I14 I-beam distribution beam is placed in the cross direction of the bridge, and then 10cm×10cm square timber is laid on it in the direction of the bridge. A 15mm thick plywood bottom formwork is laid on the square timber to ensure that the support system has sufficient bearing capacity and a stable structural state. At the same time, attention should be paid to the connection and reinforcement of the support system at the temporary piers. Figure 5 .

[0045] (2) After the pre-stressing of the formwork is completed and the pre-arch adjustment is carried out, the beam reinforcement project and prestressing construction are carried out. The order of reinforcement installation construction is: bottom plate → cross beam → web plate → partition plate → supporting inner formwork → top plate → embedded parts.

[0046] (3) When pouring the beam body concrete, pour it longitudinally from low to high and from large to small deformation, and pour it horizontally symmetrically. The concrete of the beam top plate and flange plate should be laid and vibrated at one time. After the concrete pouring is completed and the second slurry is collected, the beam surface concrete should be roughened with roughening equipment in a timely manner. After that, a dedicated person should be assigned to carry out the concrete maintenance work.

[0047] (4) After the concrete strength of the beam body meets the conditions for prestressed construction, the prestressed tendons of the beam body are tensioned in the order of longitudinal → transverse, first the long tendons, then the short tendons, first the web, then the bottom plate, and finally the top plate. At the same time, all longitudinal prestressed tendons are tensioned in accordance with the principle of "left-right symmetry, simultaneous at both ends" to complete the prestressed construction.

[0048] (5) After concrete pouring, non-load-bearing formwork should be removed after the concrete strength reaches 2.5 MPa. The support and bottom formwork of the load-bearing formwork must be removed after prestressing is established. The removal order follows: flange plate → web plate → bottom plate, and the removal should be symmetrical from the mid-span to the piers at both ends.

[0049] Step 5: Construction of cast-in-place beams of the main bridge;

[0050] (1) The cast-in-place section of the main bridge side pier is cast in-place using a full-span bracket. The bracket also uses a heavy-duty disc bracket formwork system. During the construction of the cast-in-place section, attention should be paid to reserving the embedded steel plates required for locking the rotating and closure sections. The positioning of the prestressed pipe must be accurate to ensure that it corresponds to the position of the rotating beam section to prevent misalignment during the positioning and installation of the prestressed pipe.

[0051] (2) The locking of the joint section adopts the "external rigid skeleton locking" scheme. The rigid skeleton connecting steel plates are pre-buried in advance during the construction of the segments on both sides of the joint section. Continuous observation (every 2 hours) is carried out 48 hours before the concrete pouring of the joint section to understand the changes in the elevation and distance length of the joint mouth. The concrete pouring time should be selected when the temperature is the lowest on the day and the temperature rises slowly after pouring. The 67m3 concrete of the joint section is controlled to be poured within 5 hours, and a dedicated person is assigned to carry out maintenance.

[0052] (3) After the joint section is poured, the concrete strength reaches the design requirements and the prestressing of the joint section begins. The prestressing sequence is longitudinal first, then transverse, and finally vertical. Before starting the prestressing, the rigid skeleton locked in the joint section is released to ensure that the concrete in the joint section can be compressed and deformed freely during the prestressing of the joint section.

[0053] (4) After the prestressed strength meets the requirements, remove the brackets of the joint section and the cast-in-place section, loosen the top supports on the brackets, separate the joint section formwork from the beam concrete, and then remove the brackets, formwork, and drop the beam of the cast-in-place section and the joint section.

[0054] Step 6: Secondary construction of side piers;

[0055] After the formwork supports near the cast-in-place beam supports of the approach bridge, except for the temporary piers, were removed, the side pier supporting the approach bridge end was raised according to the design requirements. The remaining pier, cast-in-place beam support pads, pier top blocks, pier side dampers, and lightning protection grounding terminals were completed. The pier body was designed to be encased in a layer of steel plate. This steel plate serves as the permanent structure of the pier column, and the pier column formwork can be constructed with this outer steel plate. Once the pier column steel plate, rebar, and concrete are all completed, a topcoat is applied, matching the concrete color as required by the design.

[0056] Step 7: Conversion of the cast-in-situ beam system of the approach bridge;

[0057] After the prestressed construction of the main beam is completed and the tensioning grooves are sealed, and the secondary concrete of the approach bridge side piers and the approach bridge support pedestal concrete strength meet the design requirements, the embedded bolts of the permanent supports on the approach bridge side are tightened and loosened one by one, and the connecting bolts between the upper and lower seat plates of the supports are loosened. The temporary support columns of the approach bridge and the formwork of the wedge-shaped blocks at the bottom of the top beam that are exposed on the concrete surface of the pier top are cut and removed to complete the conversion of the cast-in-place beam system of the approach bridge.

[0058] like Figure 6As shown, the lower end of the temporary support column of the cast-in-situ beam of the approach bridge is a steel pipe support filled with C50 slightly expansive concrete. The top surface elevation of the steel pipe support column is flush with the top of the side pier column of the approach bridge. A flange and a stiffening rib are set on the top surface of the steel pipe support column. A 25 I-steel is installed on the top surface of the flange, and a 20 I-steel is installed on the 25 I-steel. Thick bamboo plywood is laid on the 20 I-steel, and a wedge block of the beam bottom is erected on the thick bamboo plywood.

[0059] like Figure 7 As shown, 16 threaded steel bars are provided in the wedge-shaped block at the bottom of the beam.

[0060] Example

[0061] The Chengxiang River Bridge of the National Highway 241 realignment project from Beiwang Township to the county seat in Fushan County:

[0062] 1. Project Overview

[0063] The eastern extension of Xinyang Avenue is a main urban road in the core area of ​​Yangqu County. It starts from Shouyi Road in the west and ends at Shuangyang Road in the east. The road runs east-west with a red line width of 30 to 35 meters. It is a newly built road, and an overpass scheme is adopted at the Yangqu railway station node.

[0064] The upper span is 540 meters long, with a design range of K1+345.726 to K1+885.726. It consists of four spans, with a span arrangement of 2 x 43m continuous box girders, 2 x 39m continuous box girders, a (2 x 150)m single-pylon cable-stayed rotating span, and 2 x 35m continuous box girders. The main bridge deck is 26.18m wide, while the approach bridge deck widths range from 19 to 26.18m.

[0065] The side piers of the main bridge are piers 4# and 6#. The main beam is 3.5m high. The two adjacent cast-in-place beams are a 2.5m-high 2×39m continuous box girder (second unit) and a 2.0m-high 2×35m continuous box girder (fourth unit). Therefore, the piers 4# and 6# are designed as high-low platforms. The top and bottom plates of the cast-in-place approach beams are prestressed in a box-type, single-end tensioning system. The main beam top plate is prestressed in a box-type, single-end tensioning system, while the bottom plate is prestressed in a segmented system.

[0066] 2. Application effect

[0067] The cable-stayed rotating bridge over the Beitongpu Railway was constructed using this improved pier-girder reverse construction method, achieving the goal of parallel construction of the rotating main beam and the cast-in-place beam of the adjacent approach bridge. This greatly shortened the construction period, improved the effective utilization rate of mechanical equipment, reduced the time cost of project management, and achieved good economic and social benefits. The application effect is good.

[0068] This improved construction method eliminates the need to separately calculate the construction time for the adjacent approach bridge's cast-in-place beams and deck accessories. Traditional construction requires the completion of low-level pier and beam tensioning before the high-level pier elevation and approach bridge construction can proceed. The time required from the start of high-level pier construction to the completion of the adjacent cast-in-place beams and accessories is calculated as follows: 10 days for high-level pier construction, 7 days for construction of the approach bridge's side sills and supports, 2 days for installation of the bottom and end formwork for the approach bridge's cast-in-place beams at the side piers, 30 days for the approach bridge's cast-in-place beam reinforcement and concrete construction, 7 days for curing the approach bridge's cast-in-place beam concrete, 7 days for prestressing and grouting the approach bridge's cast-in-place beams, 5 days for prestressing grouting curing, 5 days for removing the bridge supports, and 15 days for the approach bridge's deck accessories. Compared to the traditional construction method, this improved construction method saves 88 days, or approximately three months, without considering any uncontrollable factors.

[0069] Conventional construction methods typically involve simultaneous construction of two approach bridges after the main girder of the main bridge is completed to minimize construction time. Each approach bridge requires two 25t truck cranes for a total of 12 months. The rental fee for each 25t crane is 36,000 yuan, resulting in a total of 432,000 yuan. Construction unit management fees are calculated at 600,000 yuan per month, resulting in a three-month cost of 1.8 million yuan. Excluding other costs, the improved reverse-construction method of piers and beams saves approximately 2.432 million yuan compared to traditional methods, including project management fees and large-scale construction machinery.

Claims

1. A method for reverse construction of cast-in-situ beams of side piers of a tilted and rotated bridge, characterized in that: The following steps are involved: Step 1: Install a spiral pipe support column filled with concrete at the top of the side pier, a flange and a stiffening plate of the spiral pipe support column, an H-shaped steel for unloading, a wedge-shaped block at the bottom of the beam at the top of the support column, and a template for the wedge-shaped block at the bottom of the beam; Step 2: By assembling the above components according to the construction sequence, the pier columns with high and low piers are constructed in two stages; in the first stage, the pier columns are constructed to a position flush with the top of the low pier of the main beam, avoiding the position of the prestressed tensioning notch of the main beam joint, and the plane position and elevation of the temporary support column of the cast-in-situ beam of the approach bridge are set at the top of the pier on the side of the approach bridge; Step 3. According to the elevation of the top of the side pier of the approach bridge, cut a 609x16mm spiral tube as the support column of the cast-in-place beam of the approach bridge, set a t=10mm, 900x900mm steel plate on the top surface of the support column as the flange of the support column, and evenly set 8 150x150mm, t=10mm triangular steel plates around the flange and the support column as stiffening plates of the flange. Intermittent welding is used between the flange steel plate and the supporting spiral tube, and full welding is used between the stiffening plate, flange and spiral tube; a circular hole with a diameter of 200mm is opened in the center of the flange as the feeding hole and vibration hole for pouring concrete for the support column, and 4 air outlets with a diameter of 10mm are evenly opened on the flange steel plate at a position 5cm away from the spiral tube wall of the support column. Pour C50 micro-expansive concrete into the spiral tube from the center hole of the flange and vibrate it densely; Step 4: Cut six 900mm long 25H-shaped steels and install three on the top of each support column flange. Install the H-shaped steels along the bridge direction, centering them on the top of the steel pipe support columns and keeping them close together. Install square wood and bamboo plywood on the top of the H-shaped steels as the outer formwork for the wedge block at the bottom of the beam. Step 5: Construct the cast-in-place sections of the main bridge side piers and the cast-in-place beams of the approach bridge simultaneously on the supports according to the cast-in-place beam construction method. After the main beam rotation is completed, construct the main bridge closure section on the supports. After the concrete strength of the closure section reaches the design strength, construct the main beam closure prestressed tendons, and perform grouting on the prestressed tendons and seal the tensioning notches. Step 6: Install the high pier steel bars and formwork on the approach bridge side of the side pier top, install the approach bridge pad stone steel bars, pour the high pier concrete on the approach bridge side, and after the concrete strength of the high pier on the approach bridge side reaches 2.5 MPa, install the approach bridge pad stone steel bars, install the bearing embedded bolts, pour the pad stone concrete, and install the spherical bearing on the approach bridge side after the concrete strength meets the requirements; Step 7: Use gas cutting to cut the H-shaped steel sections one by one along the web of the top of the temporary support column to separate the H-shaped steel sections from the web. Pull out the cut steel sections one by one from between the bottom of the beam and the temporary support column. Remove the square timber and formwork at the wedge block position at the bottom of the beam at the temporary support. Support the cast-in-place beam on the permanent support to complete the system conversion.

2. The method for reverse construction of cast-in-situ beams of side piers of an oblique-stayed rotating bridge according to claim 1 is characterized in that: The lower end of the temporary support column of the cast-in-place beam of the approach bridge is a steel pipe support filled with C50 slightly expansive concrete. The top surface of the steel pipe support column is flush with the top of the side pier of the approach bridge. A flange and a stiffening rib are set on the top surface of the steel pipe support column. A 25 I-steel is installed on the top surface of the flange, and a 20 I-steel is installed on the 25 I-steel. Thick bamboo plywood is laid on the 20 I-steel, and a wedge-shaped block of the beam bottom is erected on the thick bamboo plywood.

3. The method for reverse construction of cast-in-situ beams of side piers of an oblique-stayed rotating bridge according to claim 1 is characterized in that: 16 threaded steel bars are arranged in the wedge-shaped block at the bottom of the beam.

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