Construction method of portal pier cap beam across existing line

Abstract

This invention discloses a construction method for a portal pier cap beam spanning an existing railway line, comprising the following steps: cap foundation construction; pier body construction; completion of construction of both sides of the portal pier body; cap beam support installation; laying the cap beam bottom formwork on the intermediate support platform; installing the cap beam reinforcement cage; hoisting the cap beam reinforcement cage, fabricated on the ground, onto the cap beam bottom formwork; installing the cap beam side formwork and end formwork; and pouring concrete to form the cap beam. The cap beam support of this invention adopts a protective structure composed of a mid-span double-layer Bailey beam, adjusting the load point of the cap beam to the middle of the Bailey beam. This ensures the strength of the large-span Bailey beam support while leaving space for the erection of upper and lower protective scaffolding, providing a foundation for the good integration of the protective scaffolding and cap beam support system. This effectively solves the problems existing in cap beam support and protection during the construction of cap beams spanning existing railway lines.

Description

Technical Field

[0001] This invention belongs to the field of road and bridge construction technology, specifically relating to a construction method for portal pier cap beams spanning existing railway lines. Background Technology

[0002] Currently, there are more and more bridge projects in China that use portal pier cap beams for overpasses. During the construction of the cap beam support in the overpass area, due to the proximity to the operating line, steel columns cannot be set in the middle of the span during construction, so multi-span steel support systems cannot be used. This has caused great difficulties for the construction of large-span portal pier cap beams across existing lines.

[0003] Because the construction crosses an existing power line, the protection level required during construction is extremely high to ensure the normal and safe operation of the existing line, requiring a completely waterproof level. Furthermore, the close proximity of the bottom of the construction cap beam to the high-voltage live parts of the existing line makes it impossible to erect a separate protective scaffold during actual protection construction, all of which significantly complicate the cap beam construction. Summary of the Invention

[0004] The purpose of this invention is to provide a construction method for portal pier cap beams spanning existing railway lines, so as to solve the above-mentioned technical problems existing in the construction of portal pier cap beams spanning subway and high-speed rail lines.

[0005] This invention is achieved through the following technical solution: The construction method for portal pier cap beams crossing existing railway lines includes the following steps: S1. Construction of the foundation; S2. Pier construction; complete the construction of the pier bodies on both sides of the portal pier; S3. Installation of the cap beam support; Steel pipe columns are installed around the two piers, sand boxes are installed on top of the steel pipe column supports, and main cross beams are erected and installed on the sand boxes of the two steel pipe column supports. Then, the spliced ​​Bailey frame is hoisted and installed at both ends of the main cross beam, forming two sets of double-layer Bailey beam components that are relatively spaced at both ends of the main cross beam. A lower protective shed and a lower walking platform are erected on the lower layer of the two sets of double-layer Bailey beam components. A middle support platform is erected on the middle layer of the double-layer Bailey beam components. An upper walking platform and an upper protective shed are erected on the left and right sides of the upper layer of the double-layer Bailey beam components. S4. Lay the bottom formwork of the cap beam on the middle support platform; S5. Install the reinforcing steel cage of the cap beam; hoist the entire reinforcing steel cage of the cap beam, which has been fabricated on the ground, onto the bottom formwork of the cap beam; S6. Install the side and end formwork of the cap beam; S7. Pour concrete to form the cap beam.

[0006] In some embodiments, in step S3, the main crossbeam is made of I-beam, and U-shaped clips for limiting the Bailey bridge are welded on the main crossbeam. The installation positions of each group of Bailey bridges are marked on the main crossbeam in advance. Then, the main crossbeam is hoisted into the sand box to complete the erection and installation of the main crossbeam.

[0007] In some embodiments, in step S3, the assembled Bailey bridge is hoisted onto the main crossbeam in the order of first the middle and then the two sides, and each Bailey bridge is fixedly installed on the main crossbeam using Bailey bridge limiting U-shaped clips.

[0008] In some embodiments, in step S3, the processed main distribution beam is sequentially inserted between two sets of double-layer Bailey beam assemblies to form a middle-layer support platform between the two sets of double-layer Bailey beam assemblies.

[0009] In some embodiments, in step S3, an installation distribution beam is inserted into the gap between the lower trusses of the two sets of double-layer Bailey beam assemblies, and a lower protective shed and a lower walking platform are erected on the installation distribution beam.

[0010] In some embodiments, the lower protective canopy includes a lower main protective canopy located between two sets of double-layer Bailey beam assemblies and a lower side protective canopy located outside the double-layer Bailey beam assemblies.

[0011] In some embodiments, the upper protective shed and the lower protective shed are frame structures formed by splicing aluminum templates.

[0012] In some embodiments, in step S5, the lower crossbeam of the lifting device passes through the cap beam reinforcement cage in sequence. The lower crossbeams are evenly distributed along the longitudinal direction of the cap beam reinforcement cage. Then, the lower crossbeams are connected to the upper crossbeam of the lifting device, and the entire cap beam reinforcement cage is hoisted into the cap beam formwork.

[0013] In some embodiments, the lifting device is a Bailey bridge structure, and the upper crossbeam is sequentially inserted into the truss gap of the lifting device along the longitudinal direction. During lifting, the upper crossbeam and the corresponding lower crossbeam are connected at both ends by precision-rolled threaded steel bars.

[0014] In some embodiments, after the cap beam is cast and formed, the method further includes a step of removing the cap beam support, including: Remove the side formwork of the cap beam, erect a top hoisting support on the top slab of the cap beam, and temporarily suspend the bottom formwork of the cap beam through the top hoisting support; Sand is released from the sand box, and the main crossbeam is removed. Dismantle the upper protective shed and the middle support platform, then disassemble the double-layer reinforced Bailey beams from the middle, remove the upper Bailey beams, and retain the lower Bailey beams; A bottom formwork dismantling platform is erected on the upper end of the lower Bailey beam. The suspended bottom formwork of the cap beam is lowered onto the bottom formwork dismantling platform, and then the bottom formwork of the cap beam is dismantled. The lower protective shed and the lower Bailey beam were dismantled in sequence to complete the removal of the cap beam support.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: The girder support of this invention adopts a protective structure composed of a mid-span double-layer Bailey beam. The load point of the girder is adjusted to the middle of the Bailey beam, which ensures the strength of the large-span Bailey beam support while leaving space for the construction of the upper and lower protective sheds. This provides a foundation for the good integration of the protective sheds and the girder support system, thus effectively solving the problems in girder support and protection during the construction of girder spanning existing lines.

[0016] The present invention utilizes the structural characteristics of a mid-span double-layer Bailey bridge in the installation and construction of the cap beam support system. The entire cap beam support system and protective canopy are easy to erect and operate. The cap beam support and protective canopy structure provide a foundation for cap beam construction while providing an operating platform for construction personnel, which facilitates cap beam construction and ensures safety during the construction process and the normal operation of the existing line.

[0017] In the construction method of this invention, when dismantling the cap beam support, the bottom formwork is suspended first, then the upper Bailey beam is dismantled, and finally the bottom formwork is dismantled. This method effectively solves the problem of the bottom formwork being difficult to dismantle after the cap beam construction.

[0018] Compared with the traditional cast-in-place cap beam construction process, the method of hoisting the entire steel reinforcement cage of the cap beam during the construction process effectively reduces the amount of work to be done during the track opening period above the existing track area, greatly shortens the construction period, and saves costs, resulting in good economic and social benefits. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a structural view of the cap beam support installation in the construction method of the portal pier cap beam across the existing railway line of the present invention.

[0021] Figure 2 This is a schematic diagram of the cap beam support structure in the construction method of the portal pier cap beam across the existing railway line of the present invention.

[0022] Figure 3 This is a left view of the cap beam support structure in the construction method of the portal pier cap beam across the existing railway line of the present invention.

[0023] Figure 4This is a schematic diagram showing the state of the steel reinforcement cage of the cap beam being hoisted onto the cap beam support in the construction method of the portal pier cap beam across the existing railway line according to the present invention.

[0024] Figure 5 This is a schematic diagram of the steel reinforcement cage hoisting structure of the portal pier cap beam in the construction method of the present invention.

[0025] Figure 6 This is a schematic diagram of the dismantling process of the cap beam support in the construction method of the portal pier cap beam across the existing railway line of the present invention.

[0026] Figure 7 This is a schematic diagram of the top hoisting support structure in the construction method of the portal pier cap beam across the existing railway line of the present invention.

[0027] in: 1. Cap beam support, 2. Pier body, 3. Steel pipe column support, 4. Sand box, 5. Lifting equipment, 501. Upper crossbeam, 502. Lower crossbeam, 6. Cap beam steel reinforcement cage, 7. Cap beam; 10. Double-layer Bailey beam assembly; 101. Upper Bailey beam; 102. Lower Bailey beam; 11. Lower walking platform; 12. Lower main protective canopy; 13. Lower side protective canopy; 14. Upper walking platform; 15. Upper protective canopy. 21. Main crossbeam; 22. Main distribution beam; 23. Installation distribution beam; 31. Base template; 41. Top hoisting support. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0029] In the construction of portal pier cap beams spanning existing railway lines, this invention adopts a mid-span double-layer reinforced Bailey beam structure to adjust the load point of the cap beam to the middle of the Bailey beam. This ensures the strength of the large-span Bailey beam support while leaving space for the erection of protective scaffolding, providing a foundation for the good integration of the protective scaffolding and support system. This effectively solves the problems existing in support and protection during cap beam construction.

[0030] While the mid-span double-layer reinforced Bailey beam structure can effectively solve the support and protection issues during cap beam construction, it also makes it difficult to remove the bottom formwork after cap beam construction. To address this issue, this invention employs a construction method that first suspends the bottom formwork, then removes the upper Bailey beam, and finally removes the bottom formwork, thus effectively solving the problem.

[0031] During the dismantling of the bottom formwork, a top hoisting support was set up on the upper part of the cap beam. The bottom formwork was first suspended by high-strength threaded steel bars. Then, the double-layer reinforced Bailey beam was dismantled from the middle. After the upper Bailey beam was hoisted away, the bottom formwork was lowered and then hoisted out from the side. This effectively solved the problem of the difficulty in dismantling the cap beam formwork and the double-layer reinforced Bailey beam.

[0032] Using aluminum formwork as the protective material for the protective scaffolding creates a fully enclosed protective scaffolding, which effectively solves the problems of insufficient protective capacity of wooden formwork and heavy self-weight of steel formwork, providing a reliable guarantee for the safety of the cap beam construction.

[0033] The following section uses the construction of a portal pier cap beam spanning an existing subway line as an example to illustrate the construction method of the portal pier cap beam spanning an existing subway line according to the present invention. The construction method includes the following steps: S1, Foundation Construction Rotary drilling rigs are used for pile foundation construction. After the pile foundation construction is completed, the pile heads are removed, the pile cap reinforcement is tied, steel column base connecting reinforcement is pre-embedded on the pile cap, and the pile cap concrete is poured.

[0034] S2, Pier 2 Construction After the foundation concrete is poured, the pier reinforcement is tied. The portal pier adopts a segmented construction method, with each segment being 8m high. The construction is divided into 3 segments. When the reinforcement is tied to the segment division point, steel columns are pre-embedded in the pier body to connect the columns with steel plates, and then the pier body concrete is poured.

[0035] S3, Installation of cap beam support 1 S31, Installation of steel pipe column support 3: The lower part of the Bailey bridge uses φ609mm steel pipe columns with a wall thickness of 16mm as supporting columns. The steel pipe columns are erected to support the load and transfer it to the pile platform, and then from the pile platform to the pile foundation. To ensure that the steel pipe columns are subjected to uniform and balanced stress and that they stand vertically on the rectangular foundation, the inclination of the steel pipe columns is no greater than 1 / 600, the deviation of a single segment is no greater than 10mm, and the deviation of the total height is no greater than 3.5mm.

[0036] Mark the location for the steel pipe column support on the top surface of the foundation, and pre-embed or install HRB400 18mm diameter steel bars and thread them for bolt connection (the pull-out resistance of the steel bars shall not be less than 60kN, the length of the steel bars anchored into the foundation shall not be less than 0.4m, and the exposed threads shall not be less than 2 threads).

[0037] After the steel pipe columns are hoisted into place by a truck crane, they are securely connected to the base flange with bolts. After the steel pipe columns are installed, lateral supports are welded to ensure the lateral stability of the steel pipe columns.

[0038] During the construction of the steel pipe columns, 16 C18 steel bars are installed at each column location, with an installation depth of not less than 0.4m. The top of the steel bars is wired and connected to the steel pipe column flange via sleeves. The steel pipe columns are arranged in four rows along the pier body, with three columns per row on the side closest to the existing power line, and the spacing between the steel pipe columns is 4.301m. During installation, steel wedges are used to fine-tune the verticality of the steel pipe columns, ensuring that their verticality meets the specification requirement of 1 / 600. Finally, grout is applied to the column base, and the connecting sleeves are tightened.

[0039] The steel pipe columns are connected by [10 channel steel ear plates. The [10 channel steel is welded into a truss structure, hoisted to the welding position, and connected to the pre-embedded steel plate of the pier body. A connection is made every 6m.

[0040] S32, Sandbox 4 Installation: After the steel pipe columns are installed, an unloading device is installed between the beams and the columns to facilitate the later removal of the steel pipe supports. The unloading device uses a 40cm high sand box. Before installation, the sand box is pre-compressed to eliminate uneven settlement caused by the sand box during concrete pouring.

[0041] A 40cm high sand box is installed on top of a steel pipe column support via its flange connection. The flange connection between the steel pipe column and the sand box ensures that the center line of the sand cylinder in the sand box is aligned with the center line of the steel pipe column. The height of the sand box is calculated according to the actual design requirements, ensuring the sand filling height within the sand cylinder is met.

[0042] S33, Main crossbeam 21 installation: The main crossbeam 21 is made of I56a I-beam, with a single length of 6m. It is reinforced by welding 2cm thick steel plates at the support points of the I56a I-beam, forming three ribs at each support point. After welding, Bailey bridge beam limiting U-shaped clips are welded onto the main crossbeam.

[0043] The installation positions of each Bailey bridge frame are marked on the main crossbeam 21. One or two I56a I-beams are joined together (intermittent spot welding) to form a whole, and then hoisted to the top of the sand box and installed in place.

[0044] S34, Bailey beam installation When assembling the Bailey bridge, first install the middle Bailey section, and then install the sections symmetrically from the middle outwards. The specifications of the Bailey section are 27×3.2×0.45.

[0045] After the Bailey bridge is installed, it is connected to a flower rack to form a whole, thereby increasing the overall stability.

[0046] The Bailey panels are assembled on the bottom surface into a single long beam, with three panels per group, and the Bailey frames are connected into a whole by a crossbeam.

[0047] After assembly, double-layered [10 channel steel is welded at the support point where the Bailey beam contacts the main crossbeam to reinforce the vertical members and ensure the local stability of the Bailey beam support point.

[0048] Twelve double-layer reinforced Bailey bridge panels are longitudinally installed on a cap beam support, six on each side, with three panels connected by a decorative window. The installation positions of each Bailey bridge frame are marked on the main crossbeam according to the design spacing. A crane is used to hoist the connected Bailey bridge frames into place in the order of first the middle, then the sides, and each Bailey bridge frame is fixed to the main crossbeam using channel steel U-shaped clamps, completing the assembly of the double-layer reinforced Bailey beam. This double-layer reinforced Bailey beam consists of two sets of double-layer Bailey beam assemblies 10 arranged at relatively intervals at both ends of the main crossbeam. Each double-layer Bailey beam assembly 10 includes an upper Bailey beam 101 and a lower Bailey beam 102 stacked together. (Refer to...) Figure 1 , Figure 2 and Figure 3 .

[0049] S35. Erection and installation of the lower-level protective scaffolding: Using a combination of manual labor and a truck crane, 40 I10 steel distribution beams, each 9m long, were used as installation distribution beams 23 and sequentially inserted into the gaps of the lower truss of the double-layer reinforced Bailey beam. Two beams were laid in each truss gap, with a spacing of 30cm.

[0050] The I10 I-beam distribution beam extends from both ends to the sides of the double-layer reinforced Bailey bridge. A lower main protective canopy 12 is erected on the distribution beam between the two sets of double-layer Bailey bridge components. A lower walking platform 11 and a lower side protective canopy 13 are erected at both ends of the distribution beam extending outside the double-layer Bailey bridge components. The lower main protective canopy 12, the lower side protective canopy 13, and the lower walking platform 11 together form the lower protective system, providing a platform and space for the installation of the cap beam support and the construction of the cap beam. The lower main protective canopy provides protection for the cap beam construction, ensuring a completely leak-proof environment and guaranteeing the safe operation of the existing line during construction.

[0051] Specifically, aluminum formwork is erected on the installation distribution beams located in the middle and on both sides of the double-layer reinforced Bailey beams to form the lower protective scaffold. The use of aluminum formwork ensures the strength of the protective structure while also ensuring its sealing performance, achieving "no leakage" during construction.

[0052] The lower protective scaffolding was constructed using 4mm thick aluminum formwork, with the formwork panels connected by a socket and pin joint. The smooth side of the aluminum formwork faced downwards, while the ribbed side faced upwards. The guardrails were also assembled from aluminum formwork panels. The aluminum formwork panels were first pre-assembled in sections on the ground, each section being 3m long, and then hoisted and installed using a truck crane.

[0053] S36. Erection and installation of the intermediate support platform: On the ground, the I25a main distribution beam 22 is processed by cutting the 12m steel section into two 6m long steel sections. The two steel sections are intermittently welded together. The steel sections are then inserted into the gap of the middle truss of the double-layer reinforced Bailey beam using a combination of manual labor and a truck crane. This forms a support platform in the middle layer of the double-layer reinforced Bailey beam, which serves as the load-bearing layer for the cap beam construction and is used to install the bottom formwork of the cap beam.

[0054] Specifically, multiple main distribution beams 22 are sequentially inserted between two sets of double-layer Bailey beam assemblies 10 along the longitudinal direction of the double-layer Bailey beam assembly 10, thus forming a middle-layer support platform composed of main distribution beams between the two sets of double-layer Bailey beam assemblies.

[0055] At this time, the middle support platform is located directly above the lower main protective shed 12. In this way, during the construction of the cap beam, the middle support platform provides a foundation for supporting the cap beam formwork system, while the lower main protective shed 13 provides protection for the cap beam construction, ensuring that there is no water leakage during the construction process.

[0056] S37, Erection and installation of the upper protective scaffolding 15: Upper walking platforms 14 are erected on the left and right sides (the upper ends of the two double-layer Bailey beam components) of the upper layer of the double-layer reinforced Bailey beam. Aluminum formwork is then erected on the upper walking platforms 14 to form an upper protective scaffold 15, thus forming an upper-level operational protection system. The upper walking platforms provide space for the construction of the cap beam and the installation of the cap beam formwork.

[0057] At this time, a fully enclosed protective canopy is installed to form a support structure for the cap beam.

[0058] This provides a foundation for the subsequent installation of the cap beam formwork, and also provides operational space for the installation of the cap beam formwork. The fully enclosed structure formed by the use of aluminum formwork can effectively ensure that there is no water leakage during the construction of the cap beam, providing a reliable guarantee for the safety of the cap beam construction across the existing line.

[0059] S4, Installation of bottom formwork for cap beam 31 After the cap beam support is installed, the bottom formwork 31 of the cap beam is laid on the middle support platform of the double-layer reinforced Bailey beam. The bottom formwork 31 is made of 8mm steel plate. Figure 7 As shown.

[0060] S5. Install the steel reinforcement cage for the cap beam. The installation of the reinforcing steel cage for the cap beam involves fabricating the cage as a whole on the ground, and then hoisting it into the cap beam formwork as a whole, referring to... Figure 4 .

[0061] S51, Lifting Gear 5 Fabrication: Two 15m long single-layer Bailey beams are used as the longitudinal beams of the lifting device. 0.9m decorative windows are used to connect the top and middle of the Bailey beams. Then, 22 0.45m long φ25 precision rolled threaded steel bars are used to connect the 11 upper crossbeams 501 of the lifting device to the Bailey beams through the chord bolt holes to complete the fabrication of the lifting device.

[0062] The lower crossbeam 502 of the lifting device is made of [10 channel steel cut into 3m long segments. Six φ25 precision rolled threaded steel anchor plates are set in the middle to weld two [10 channel steels together. The spacing between the channel steels is set to 3cm. There are a total of 11 lower crossbeams 502 of the lifting device.

[0063] S52, Fabrication of the steel reinforcement cage for the cap beam: Double-row disc-lock scaffolding is erected on the ground, and the two rows of scaffolding are connected by couplers using ordinary steel pipes; first, the longitudinal reinforcement of the cap beam is laid on the ordinary steel pipes, then the stirrups are tied, then the lateral and bottom longitudinal reinforcement is tied, and finally the corrugated pipes are threaded through and fixed, and tied on the ground to form the cap beam reinforcement skeleton 6.

[0064] S53, hoisting of the cap beam reinforcement cage 6: After the reinforcing steel cage 6 of the cap beam is tied on the ground, the lower crossbeams 502 of the lifting device 5 are passed through the reinforcing steel cage 6. The lower crossbeams 502 are evenly distributed along the longitudinal direction of the reinforcing steel cage. Then, the lifting device is suspended in the air, and the upper crossbeam 501 of the lifting device 5 is connected to the lower crossbeams 502 by 22 1m long φ25 precision-rolled threaded steel bars. The lifting device is then lifted, and the entire reinforcing steel cage of the cap beam is hoisted onto the bottom formwork of the cap beam. This ensures that the reinforcing steel cage of the cap beam does not deform throughout the entire span during the hoisting process.

[0065] Specifically, refer to Figure 5 The lower crossbeam 502 of the lifting device 5 is passed sequentially through the cap beam reinforcement cage 6. The lower crossbeams are evenly distributed along the longitudinal direction of the cap beam reinforcement cage. Then, the lower crossbeam 502 is connected to the upper crossbeam 501 of the lifting device, and the entire cap beam reinforcement cage is hoisted into the cap beam formwork. The lifting device is a Bailey bridge structure. The upper crossbeam 501 is sequentially passed through the truss gaps of the lifting device along the longitudinal direction and is fixedly connected to the truss. During hoisting, the upper crossbeam 501 and the corresponding lower crossbeam 502 are connected at both ends by precision-rolled threaded steel bars.

[0066] After the steel reinforcement cage of the cap beam is hoisted into place, the steel reinforcement in the non-crossing areas on both sides is tied, and the corrugated pipe is extended and the inner lining sleeve is installed.

[0067] The steel reinforcement cage of the cap beam is fabricated on the ground and then hoisted as a whole to the bottom formwork 31 of the cap beam. This method can effectively solve the problem of the construction cycle being affected by the limited window period during the construction process across the existing line. As a result, the construction cycle can be greatly shortened and the construction progress can be guaranteed without affecting the normal operation of the subway line.

[0068] Because the overall span of the cap beam reinforcement cage is large, it is easy for it to deform during the hoisting process. Once deformation occurs, it will affect the construction quality of the cap beam. Therefore, a special hoisting tool for the cap beam reinforcement cage has been made. Using this hoisting tool and hoisting method can effectively ensure that the cap beam reinforcement cage will not deform during the hoisting process.

[0069] S6. Installation of side formwork, end formwork, and top slab for cap beam. After the steel reinforcement cage of the cap beam is tied on the cap beam support, the side formwork, end formwork and top plate are installed, and the side formwork is reinforced with tie rods.

[0070] The side formwork is made of 6mm steel plate, and the side formwork frame is made of I12 and 12mm steel plates, with three I25a I-beams welded together.

[0071] The end formwork is made of 8mm steel plate, the frame is made of 160×80×5mm rectangular tube and 12mm steel plate, and the middle part of the cap beam formwork and the top plate are reinforced with φ25 precision rolled threaded steel for tie rods.

[0072] At this point, a cap beam formwork is erected within the middle support platform of the double-layer reinforced Bailey beam with a U-shaped frame structure, providing an operating platform for the installation of the cap beam formwork and providing effective protection for the cap beam construction through the double-layer reinforced Bailey beam structure.

[0073] S7, Concrete Pouring The cap beam is made of C50 concrete and is poured in one go. The cap beam concrete must be poured within a 3-hour window period.

[0074] After the concrete is poured, the prestressed steel strands are installed.

[0075] S8, Removal of the cap beam support On the upper walking platform of the double-layer reinforced Bailey beam, the side formwork of the cap beam is removed; A double-span I10 flat beam is installed on top of the cap beam to form a top hoisting support 41. φ25 precision-rolled threaded steel is used to temporarily suspend the bottom formwork 31 of the cap beam, as per [reference needed]. Figure 6 and Figure 7 .

[0076] The main crossbeam is unloaded, and the unloading operation is carried out from one end to the other. First, sand is released from the sand box, and the sand release operation is carried out simultaneously to ensure that the main crossbeam is unloaded smoothly. Then, the upper walking platform 14 and the upper protective canopy 15 are gradually dismantled by a combination of manual and mechanical means. The I25a main distribution beam 22, which serves as the middle support platform, is pulled out from the side. The double-layer reinforced Bailey beam is dismantled from the middle. The bolt connection between the upper and lower Bailey beams is released. The upper Bailey beam is removed, and the lower Bailey beam is retained. On the upper end face of the lower Bailey beam, an I10 support distribution beam is installed below the bottom formwork to form a bottom formwork dismantling platform, creating a space for dismantling the bottom formwork between the bottom formwork dismantling platform and the bottom formwork of the cap beam.

[0077] The suspended bottom formwork 31 of the cap beam is lowered onto the bottom formwork dismantling platform. Then, with the help of manual labor and machinery, the bottom formwork is gradually pulled out from the side to complete the dismantling of the bottom formwork of the cap beam.

[0078] Remove the I10 support distribution beam, the lower protective canopy, the I10 installation distribution beam 23 used to support the lower protective canopy, and finally remove the lower Bailey beams 102 on both sides. Then, the I56a main crossbeam 21, sand box 4, and steel pipe column support 3 are removed in sequence to complete the removal of the cap beam support.

[0079] Compared with the traditional cast-in-place cap beam construction process, the method of hoisting the entire steel reinforcement cage of the cap beam during the construction process effectively reduces the amount of work to be done during the maintenance window above the existing track area, greatly shortens the construction period, and saves costs. Taking the construction of three cap beams across the existing subway line in a certain rail transit project as an example, this construction method saved 48 days of construction time and more than 1 million yuan in costs, achieving good economic and social benefits.

[0080] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., used to indicate the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of this invention is usually placed in during use. They are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0081] Furthermore, the use of terms such as "horizontal" and "vertical" in the description of this invention does not imply that the components are required to be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0082] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A construction method for a portal pier deck beam across an existing line, characterized by, Includes the following steps: S1. Construction of the foundation; S2. Pier construction; complete the construction of the pier bodies on both sides of the portal pier; S3. Installation of the cap beam support; Steel pipe columns are installed around the two piers, sand boxes are installed on top of the steel pipe column supports, and main cross beams are erected and installed on the sand boxes of the two steel pipe column supports. Then, the spliced ​​Bailey frame is hoisted and installed at both ends of the main cross beam, forming two sets of double-layer Bailey beam components that are relatively spaced at both ends of the main cross beam. A lower protective shed and a lower walking platform are erected on the lower layer of the two sets of double-layer Bailey beam components. A middle support platform is erected on the middle layer of the double-layer Bailey beam components. An upper walking platform and an upper protective shed are erected on the left and right sides of the upper layer of the double-layer Bailey beam components. The installation distribution beams are sequentially inserted into the gaps of the lower truss of the double-layer reinforced Bailey beams, with both ends extending out to the sides of the double-layer reinforced Bailey beams. A lower main protective canopy is erected on the installation distribution beams between the two sets of double-layer Bailey beam components. Lower walking platforms are erected at the two ends of the installation distribution beams that extend to the outside of the double-layer Bailey beam components. The main distribution beams are inserted sequentially into the gaps of the middle truss of the double-layer reinforced Bailey beams along the longitudinal direction of the double-layer Bailey beam assembly, forming a middle support platform composed of the main distribution beams between the two sets of double-layer Bailey beam assemblies. S4. Lay the bottom formwork of the cap beam on the middle support platform; S5. Install the steel reinforcement cage for the cap beam; The entire steel reinforcement cage of the cap beam, which has been fabricated on the ground, will be hoisted onto the bottom formwork of the cap beam. S6. Install the side and end formwork of the cap beam; S7. Pour concrete to form the cap beam.

2. The method for constructing a portal pier deck beam across an existing line according to claim 1, characterized in that, In step S3, the main crossbeam is made of I-beams. U-shaped clips for Bailey bridge positioning are welded onto the main crossbeam, and the installation positions of each Bailey bridge group are marked on the main crossbeam in advance. Then, the main crossbeam is hoisted into the sand box to complete the erection and installation of the main crossbeam.

3. The method for constructing a portal pier deck beam across an existing line according to claim 2, characterized in that, In step S3, the assembled Bailey bridge frames are hoisted onto the main crossbeam in the order of first the middle and then the two sides, and each Bailey bridge frame is fixedly installed on the main crossbeam using Bailey bridge frame limiting U-shaped clips.

4. The method for constructing a portal pier deck beam across an existing line according to claim 1, wherein The lower protective canopy includes a lower main protective canopy located between two sets of double-layer Bailey beam assemblies and a lower side protective canopy located outside the double-layer Bailey beam assemblies.

5. The method for constructing a portal pier deck beam across an existing line according to claim 1 or 4, characterized in that, The upper and lower protective sheds are frame structures formed by splicing aluminum templates.

6. The method for constructing a portal pier deck beam across an existing line according to claim 1, wherein In step S5, the lower crossbeam of the lifting device is passed through the cap beam reinforcement cage in sequence. The lower crossbeams are evenly distributed along the longitudinal direction of the cap beam reinforcement cage. Then, the lower crossbeams are connected to the upper crossbeam of the lifting device, and the entire cap beam reinforcement cage is hoisted into the cap beam formwork.

7. The method for constructing a portal pier deck beam of an existing line according to claim 6, wherein The lifting device is a Bailey bridge structure. The upper crossbeam is sequentially inserted into the truss gaps of the lifting device along the longitudinal direction. During lifting, the upper crossbeam and the corresponding lower crossbeam are connected at both ends by precision-rolled threaded steel bars.

8. The method for constructing a portal pier deck beam across an existing line according to claim 1, wherein After the cap beam is cast, the process also includes the step of dismantling the cap beam support, including: Remove the side formwork of the cap beam, erect a top hoisting support on the top slab of the cap beam, and temporarily suspend the bottom formwork of the cap beam through the top hoisting support; Sand is released from the sand box, and the main crossbeam is removed. Dismantle the upper protective shed and the middle support platform, then disassemble the double-layer reinforced Bailey beams from the middle, remove the upper Bailey beams, and retain the lower Bailey beams; A bottom formwork dismantling platform is erected on the upper end of the lower Bailey beam. The suspended bottom formwork of the cap beam is lowered onto the bottom formwork dismantling platform, and then the bottom formwork of the cap beam is dismantled. The lower protective shed and the lower Bailey beam were dismantled in sequence to complete the removal of the cap beam support.

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