Construction method of prestressed secondary tensioning of cap beam

Abstract

This invention discloses a method for secondary prestressing tensioning of a cap beam. Utilizing the weight of the suspended platform structure itself, the platform is hoisted into position, and the operating platform is installed using counter-tensioning. This method avoids anchorage damage to the cap beam, shortens the construction period, and significantly improves construction efficiency. It enables efficient and timely secondary prestressing tensioning of the cap beam after its initial placement. Furthermore, the tensioning components provide a continuous safety belt suspension foundation for the box beam placement construction. Compared to existing technologies, this method improves safety, reduces construction costs, ensures the overall quality of the cap beam, and provides a safety guarantee for the construction of the box beam.

Description

Technical Field

[0001] This invention relates to a bridge construction method, and more particularly to a prestressed secondary tensioning construction method for a cap beam. Background Technology

[0002] During the construction of urban viaducts, secondary prestressing tensioning is required after the cap beams are in place to ensure overall support strength. In existing technologies, secondary prestressing tensioning requires the small box girder (steel-concrete composite beam) to be installed on top of the cap beam and immediately tensioned after bearing load, achieving good tensioning results. However, at this stage, construction cannot be carried out on the bridge deck before it is formed. Typically, ground-based support frames and platforms are erected for tensioning operations. This method significantly increases construction costs, requires a time frame for temporary erection, and poses safety hazards due to unstable foundations and personnel movement. Consequently, secondary prestressing tensioning of the cap beams cannot usually be performed in a timely manner during construction, leading to potential quality issues related to linear deformation of the cap beams.

[0003] Furthermore, when the box girder was in place, suitable safety belt suspension points could not be found on the top of the cap girder, making it impossible to meet the requirement of correctly suspending safety belts for work at heights and near edges. Coupled with the frequent movement during operations, traditional fixing points were no longer sufficient, resulting in workers wearing safety belts without effective securing them, thus creating significant safety risks. Installing an operating platform on the cap girder, however, would damage it due to the need for anchoring, and the construction period would still be very long, reducing construction efficiency.

[0004] Therefore, it is necessary to improve the existing secondary tensioning construction operation of prestressed cap beams to enable efficient and timely secondary tensioning of prestressed cap beams. Compared with existing technologies, this will improve the safety level, reduce construction costs, ensure the overall quality of cap beams, and provide a safety guarantee for the construction of box girders. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a prestressed secondary tensioning construction method for cap beams, which can efficiently and timely perform prestressed secondary tensioning on cap beams. Compared with the prior art, this method improves the safety level, reduces construction costs, ensures the overall quality of cap beams, and provides a safety guarantee for the construction of box girders.

[0006] The prestressed secondary tensioning construction method for the cap beam of the present invention includes the following steps:

[0007] a. Construct and install the operating platform for secondary prestressing tensioning on the cap beam:

[0008] a1 lifts two baskets used to form the operating platform, with the lifting height of the two baskets corresponding to the two ends of the cap beam;

[0009] a2 is tensioned from both ends of the cap beam by two opposing suspended baskets, and the opposing tension, the weight of the suspended baskets themselves, and the support at the ends of the cap beam are used to fix the suspended baskets to both ends of the cap beam, which is used to provide an operating platform for the secondary tensioning of the cap beam prestress; forming the tensioning member of the opposing tensioning is suspended and located between the box beams on both sides of the cap beam.

[0010] b. Using the tensioning members from step a to provide a safety belt for the foundation for safe suspension, the box girder is positioned on the cap beam during construction.

[0011] c. After all the box girders are in place, the cap beams are subjected to secondary prestressing tensioning on the tensioning platform.

[0012] d. After the secondary prestressing tensioning is completed, the operating platform is dismantled.

[0013] Furthermore, the suspended basket includes a basket and an overlapping longitudinal beam. The overlapping longitudinal beam includes a long longitudinal beam with one end fixed to the far edge of the basket and extending to the upper surface of the cover beam after being in place, and a short longitudinal beam with one end fixed to the near edge of the basket and extending to the upper surface of the cover beam after being in place; in step a1, the lower surface of the overlapping longitudinal beam is attached to the upper surface of the cover beam.

[0014] Furthermore, the short longitudinal beams are a number of beams arranged side by side in the middle of the basket, and the long longitudinal beams are a number of beams arranged side by side in the middle of the basket, on both sides of the short longitudinal beams; an overlapping crossbeam is fixedly connected between adjacent overlapping longitudinal beams, and in step a1, the lower surface of the overlapping crossbeam is attached to the upper surface of the cover beam.

[0015] Furthermore, the lower surfaces of the overlapping longitudinal beams and overlapping transverse beams are roughened; the center of gravity of the suspended platform is located on one side of the overlapping longitudinal beams.

[0016] Furthermore, it also includes an anti-rollover beam assembly located at the bottom of the basket. The anti-rollover beam assembly includes at least two anti-rollover beams arranged horizontally side by side. In step a2, after being tensioned in opposite directions, the anti-rollover beams can be driven to abut against the lower surface of the cover beam to form a structure that resists the lateral rollover of the basket.

[0017] Furthermore, the basket includes a supporting body, a frame panel, and a bottom plate. The supporting body is a cuboid frame composed of bottom longitudinal beams, bottom transverse beams, frame vertical beams, top longitudinal beams, and top transverse beams. The bottom plate is fixed to the bottom of the cuboid frame to form the bottom of the operating platform. The frame panel is fixed between adjacent frame vertical beams and leaves room for the secondary tensioning of the prestressed cap beam.

[0018] The long side of the cuboid frame is located horizontally, and auxiliary vertical beams are provided between the horizontally parallel frame vertical beams, with a position reserved near the basket for the secondary tensioning of the prestressed cap beam; the two ends of the auxiliary vertical beams are fixed to the corresponding top and bottom horizontal beams of the frame, respectively; the long longitudinal beam is fixed to the corresponding frame vertical beam or the corresponding auxiliary vertical beam at the far end; and the short longitudinal beam is fixed to the frame vertical beam, the corresponding auxiliary vertical beam, or the corresponding top horizontal beam at the near end.

[0019] Auxiliary longitudinal beams for the bottom of the frame are also arranged in parallel between the longitudinal beams for the bottom of the frame, and the two ends of the auxiliary longitudinal beams for the bottom of the frame are respectively fixed to the corresponding transverse beams for the bottom of the frame.

[0020] Furthermore, the anti-tipping beam assembly also includes an outer cylindrical beam, the anti-tipping beam being fitted inside the outer cylindrical beam and capable of being driven to reciprocate longitudinally; the outer cylindrical beam is hinged to the basket and can swing along a vertical plane.

[0021] In step a2, the anti-tipping beam is driven to slide towards the bottom of the cover beam, and the outer cylindrical beam is driven to swing so that the anti-tipping beam abuts against the lower surface of the cover beam, locking the inner end of the anti-tipping beam to the basket.

[0022] Furthermore, a tensioning vertical beam is fixed to the lap beam and extends upward, and a tensioning longitudinal beam extends from the top of the tensioning vertical beam in the opposite direction; in step a1, the tensioning longitudinal beams of the baskets located at both ends of the cap beam are connected by tensioning members to form tension;

[0023] The connection between the overlapping longitudinal beam and the basket is a detachable fixed connection.

[0024] Furthermore, a tensioning inclined beam is also fixedly provided at the top of the tensioning vertical beam and at the far end of the basket;

[0025] The tensioned longitudinal beam is inclined at a small angle upwards towards the opposite side.

[0026] Furthermore, it also includes a tensioning and fixing assembly, which includes a tensioning crossbeam and a tensioning diagonal bar;

[0027] The end of the overlapping longitudinal beam forms a snap-fit ​​groove with an end opening. The tensioning crossbeam is snapped into the snap-fit ​​groove along the longitudinal direction. One end of the tensioning diagonal rod, which can swing along the longitudinal vertical plane, is hinged to the bottom of the basket. The other end passes through the through hole on the tensioning crossbeam and is detachably connected to the tensioning crossbeam, thus forming a tensioning reinforcement for the bottom of the basket.

[0028] The tensioning longitudinal beam is an I-beam, the tensioning member is an I-beam, and the tensioning member and the tensioning longitudinal beam are connected by steel plates attached to both sides of the web and by multiple sets of bolts.

[0029] Alternatively, the tensioning longitudinal beam is an I-beam, and the tensioning member is two strip steel plates attached to both sides of the web of the tensioning longitudinal beam and connected by multiple sets of bolts.

[0030] The beneficial effects of this invention are as follows: The prestressed secondary tensioning construction method for the cap beam of this invention utilizes the weight of the suspended platform structure itself to hoist the platform into place, and the operation platform can be installed in place by combining it with counter-tensioning. Overall, it does not cause anchorage damage to the cap beam, and the construction cycle is shorter, significantly improving construction efficiency. It enables efficient and timely secondary prestressing of the cap beam after the box girder is in place. Simultaneously, the tensioning component also provides a continuous safety belt suspension foundation for the box girder placement construction. Compared with existing technologies, this improves the safety level, reduces construction costs, ensures the overall quality of the cap beam, and provides a safety guarantee for the construction of the box girder. Attached Figure Description

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] Figure 1 This is a structural schematic diagram of the present invention in the construction state;

[0033] Figure 2 This is a top view of the structure of the present invention in the construction state;

[0034] Figure 3 for Figure 1 Enlarged view of point A;

[0035] Figure 4 for Figure 1 Enlarged view of point B;

[0036] Figure 5 for Figure 1 Enlarged view of point C;

[0037] Figure 6 for Figure 2 Enlarged view at point D

[0038] Figure 7 This is a schematic diagram of the basketball hoop structure. Detailed Implementation

[0039] As shown in the figure: The prestressed secondary tensioning construction method for the cap beam in this embodiment includes the following steps:

[0040] a. Construct and install the operating platform for secondary prestressing tensioning on cap beam 1:

[0041] a1 hoisting two baskets 5 used to form the operating platform, with the hoisting height of the two baskets 5 corresponding to the two ends of the cap beam 1; the tensioning points of the prestressed secondary tensioning of the cap beam are located at both ends of the cap beam, therefore, the baskets 5 are hoisted symmetrically at both ends of the cap beam, and the operating platform is formed by the operation method in step a2; here, the two ends of the cap beam 1 refer to the two ends of the cap beam in the longitudinal direction (unless otherwise specified in this invention, the longitudinal direction refers to the longitudinal direction of the cap beam), that is, corresponding to the transverse direction of the bridge, which will not be elaborated further here;

[0042] a2 performs counter-tensioning on the cap beam 1 from both ends, targeting two suspended troughs 5. This counter-tensioning, along with the weight of the troughs 5 and the longitudinal support of the cap beam 1, fixes the troughs 5 to both ends of the cap beam 1, providing an operating platform for the secondary prestressing tensioning of the cap beam. The tensioning member 4 is suspended and positioned between the box girders on both sides (lateral sides, corresponding to the longitudinal direction of the bridge) of the cap beam 1. Structurally, the two troughs 5 rest against both ends of the cap beam, and the tensioning member 4 is tensioned between the two troughs 5. Under the conversion action at the ends of the cap beam 1, the two troughs 5 utilize... The longitudinal tension component is formed by the weight of the platform itself, and mutual opposing tension is formed through the tensioning member 4. Combined with the weight of the platform and the supporting effect of the end of the cap beam, the fixing force of the platform 5 is formed, ensuring the stability of the platform, thus forming a prestressed secondary tensioning operation platform. Opposing tension refers to the two platforms 5 applying opposing tension forces to each other, which will not be elaborated here. The opposing tension structure allows the platform system to form a fixed installation by itself without destroying the cap beam 1 to fix the platform 5. It is also easy to disassemble and assemble, has a high reuse rate, helps to reduce the cost of use and improve work efficiency.

[0043] b. Using the tensioning member 4 of the opposing tensioning in step a, a safety belt is provided for the safety suspension foundation, and the box girder 2 is positioned on the cap beam for construction; the tensioning member 4 can also be used to suspend the safety belt to ensure construction safety;

[0044] c. After all box girders 2 are in place, the cap beam 1 is subjected to secondary prestressing tensioning on the tensioning platform. The secondary prestressing tensioning process and tensioning equipment are all existing technologies and will not be described in detail here. The tensioning equipment should be placed on the operating platform before tensioning, and will not be described in detail here.

[0045] d. After the secondary prestressing tensioning is completed, the operating platform is dismantled.

[0046] In this embodiment, the suspended platform 5 includes a basket 501 and overlapping longitudinal beams. The overlapping longitudinal beams include a long longitudinal beam 502 with one end fixed to the far edge of the basket and extending to the upper surface of the cover beam after being in place, and a short longitudinal beam 503 with one end fixed to the near edge of the basket and extending to the upper surface of the cover beam after being in place. In step a1, the lower surface of the overlapping longitudinal beam is attached to the upper surface of the cover beam 1. The near end and the far end are relative to the cover beam 1, and the one farther away is the far end. The structure in which longitudinal beams can be set at both the near end and the far end can ensure the support stability of the suspended platform and avoid the danger of falling. After the suspended platform 5 is in place, the overlapping longitudinal beam is attached to the upper surface of the cover beam 1, which has a certain hooking effect and can be used to resist the overturning torque formed by the pull, thereby helping to maintain the stability of the suspended platform 5.

[0047] In this embodiment, there are several short longitudinal beams 503 arranged side by side in the middle of the basket 501, and several long longitudinal beams 502 arranged side by side in the middle of the short longitudinal beams 503. Overlapping crossbeams 504 are fixedly connected between adjacent overlapping longitudinal beams. In step a1, the lower surface of the overlapping crossbeam 504 is attached to the upper surface of the cover beam 1. Adjacent overlapping longitudinal beams refer to the relationship between adjacent short longitudinal beams, adjacent long longitudinal beams, and adjacent long and short longitudinal beams, which will not be elaborated further here. The two ends of the overlapping crossbeam can be welded and fixed to the corresponding overlapping longitudinal beam to form a complete integrated structure. The short longitudinal beams 503 are arranged near the middle of the basket 501 to avoid affecting the tensioning operation due to passing through the frame opening, which will not be elaborated further here.

[0048] In this embodiment, the lower surfaces of the overlapping longitudinal beams and overlapping transverse beams 504 are roughened. This roughening process can be achieved using existing methods, such as using a non-metallic material with a high coefficient of friction or performing surface roughening by engraving. The non-metallic material is generally a detachable hard non-metallic material or a vulcanized rubber layer, which will not be elaborated further here. The center of gravity of the suspended platform is located on one side of the overlapping longitudinal beam. Through the design of the overlapping longitudinal beam and the suspended platform, and in conjunction with the setting of other components, the position of the center of gravity of the entire suspended platform can be adjusted, such as by extending the overlapping longitudinal beam or adding counterweights, which will not be elaborated further here. With the center of gravity located within the area of ​​the overlapping longitudinal beam, combined with the roughening process, the overlapping longitudinal beam further enhances its hook-like effect after the suspended platform is installed, resulting in better installation stability.

[0049] In this embodiment, an anti-tipping beam assembly 507 is also provided below the basket 501. The anti-tipping beam assembly includes at least two anti-tipping beams 5072 arranged horizontally side by side. In step a2, after tensioning in opposite directions, the anti-tipping beams 5072 can be driven to abut against the lower surface of the cover beam 1 to form a structure that resists the lateral flipping of the basket 501. By setting two anti-tipping beams 5072, the lateral flipping of the basket can be effectively resisted, thereby further increasing the stability and safety of the basket. The anti-tipping beams can be driven by existing mechanical drive methods or by manual drive. For example, the anti-tipping beams can reciprocate and be fitted inside a sleeve, and the sleeve is fixed to the basket. They can be manually pushed out when in use. Alternatively, they can be electrically driven by a motor to complete the above process, which will not be described in detail here.

[0050] In this embodiment, the basket 501 includes a supporting body, a frame panel 5016, and a base plate 5017. The supporting body is a cuboid frame composed of bottom longitudinal beams 5012, bottom transverse beams 5013, frame vertical beams 5011, top longitudinal beams 5014, and top transverse beams 5015. The base plate 5017 is fixed to the bottom of the cuboid frame to form the bottom of the operating platform. The frame panel 5016 is fixed between adjacent frame vertical beams 5011, leaving an operating position for the secondary tensioning of the prestressed cap beam. As shown in the figure, two bottom longitudinal beams 5012 and two bottom transverse beams 5013 form a rectangular bottom frame, and two top longitudinal beams 5014 and two top transverse beams 5015 form a rectangular top frame. The four corners of the rectangular bottom frame and the rectangular top frame are fixedly connected by four frame vertical beams 5011, thereby forming a cuboid frame. Of course, to ensure strength, some reinforcing beams can be added to the frame, which will not be elaborated here.

[0051] The long side of the cuboid frame is located horizontally, and auxiliary vertical beams 50111 are provided between the horizontally parallel frame vertical beams 50111. These auxiliary beams are positioned near the basket 501 to allow for secondary tensioning of the cap beam. The auxiliary beams 50111 should not interfere with the secondary tensioning construction; this will not be elaborated further. The two ends of the auxiliary beams 50111 are fixed to the corresponding top and bottom horizontal beams 5015 and 5013, respectively. The long longitudinal beams 502 are fixed to the corresponding far-end frame vertical beams 50111 or the corresponding auxiliary beams 50111, as shown in the figure. There are two long longitudinal beams 502, with their far ends fixed to the two auxiliary beams 50111. The corresponding ends of the long longitudinal beams are bent downwards, and the bent portions are connected to the corresponding auxiliary beams 50111. The inner surface of beam 50111 is overlapped and detachably fixed or welded. In this embodiment, a detachable fixed connection is used, which is replaceable and easy to transport and store. The short longitudinal beam 503 is fixed to the near-end frame vertical beam, the corresponding frame auxiliary vertical beam, or the corresponding frame top crossbeam. As shown in the figure, the end of the short longitudinal beam 503 is bent downward and the bent part overlaps with the inner surface of the corresponding frame auxiliary vertical beam 50111 and is detachably fixed or welded. In this embodiment, a detachable fixed connection is used, which is replaceable and easy to transport and store. Of course, the frame auxiliary vertical beam 50111 is described with the same marking. The setting of the frame auxiliary vertical beam 50111 located on the side of the basket 501 near the cover beam should not interfere with the secondary tensioning construction, and will not be described again here.

[0052] A frame bottom auxiliary longitudinal beam 50121 is also arranged in parallel between the frame bottom longitudinal beams 5012. The two ends of the frame bottom auxiliary longitudinal beams are respectively fixed to the corresponding frame bottom cross beams 5013. The frame bottom longitudinal beams 5012 are two beams that form the two short sides of a rectangular bottom frame. The frame bottom auxiliary longitudinal beams 50121 are set to ensure the support strength. They are generally fixed by welding, which will not be described in detail here.

[0053] In this embodiment, the anti-tipping beam assembly 507 further includes an outer cylindrical beam 5071. The anti-tipping beam 5072 is fitted inside the outer cylindrical beam and can be driven to slide back and forth longitudinally. The outer cylindrical beam 5071 is hinged to the basket 501 and can swing along the vertical plane, as shown in the figure. It is generally hinged to the corresponding basket auxiliary vertical beam and has sufficient strength. The two anti-tipping beams 5072 are arranged symmetrically in the transverse direction to ensure the anti-tipping effect, which will not be described in detail here.

[0054] In step a2, the anti-tipping beam 5072 slides towards the bottom of the cover beam 1, and the anti-tipping beam 5072 drives the outer cylindrical beam 5071 to swing so that the anti-tipping beam abuts against the lower surface of the cover beam 1, locking the inner end of the anti-tipping beam 5072 to the basket. As shown in the figure, in use, the anti-tipping beam 5072 slides outward, while driving the outer cylindrical beam 5071 to swing until the end of the anti-tipping beam 5072 abuts against the bottom of the cover beam, locking the anti-tipping beam 5072 inside the basket; there are various locking methods, the most common being locking with bolts, that is, bolt holes are made at the set positions on the anti-tipping beam 5072, and bolts are fixed on the bottom of the basket (usually on the auxiliary longitudinal beam at the bottom of the frame to ensure strength). After the swing is completed, the bolt holes are fitted onto the bolts and locked by nuts, which will not be described in detail here;

[0055] In this embodiment, a tensioning vertical beam 508 is fixed to the lap beam and extends upwards, and a tensioning longitudinal beam 505 extends from the top of the tensioning vertical beam 508 towards the opposite direction; in step a1, the tensioning longitudinal beams 505 of the baskets 501 at both ends of the cover beam 1 are connected by tensioning members 4 to form tension; as shown in the figure, the tensioning vertical beam 508 is fixed on the corresponding lap beam 504 and forms a stable support through the support diagonal beams set in four directions respectively.

[0056] The fixed connection between the overlapping longitudinal beams (including long longitudinal beams and short longitudinal beams) and the basket 501 is a detachable fixed connection, which is achieved by using bolts of a set size, and will not be described in detail here.

[0057] In this embodiment, a tensioning inclined beam 506 is also fixedly provided at the top of the tensioning vertical beam 508 and the far end of the basket 501; a direct connection is formed between the tensioning vertical beam and the basket to ensure the integrity of the basket and the coordination of the force; as shown in the figure, a frame-fixing auxiliary longitudinal beam is provided in the middle of the basket, and both ends are fixedly connected between two frame top crossbeams respectively. The far end of the tensioning inclined beam 506 is bent and the bent part overlaps on the frame-fixing auxiliary longitudinal beam and is fixedly connected by bolts in a detachable manner. The other end is fixed to the top of the tensioning vertical beam 508, forming a triangular stable tensioning structure;

[0058] The tensioning longitudinal beam 505 is inclined at a small angle upwards in the opposite direction; the tensioning longitudinal beam 505 is welded and fixed to the top of the tensioning vertical beam 508 for connection with the tensioning member 4, providing a structural foundation for opposing tensioning; the small angle of inclination can be automatically leveled after tensioning to ensure that the tension force can be fully applied to the suspended platform. The inclination angle generally does not exceed 3°, which will not be elaborated further here.

[0059] In this embodiment, a tensioning and fixing component 509 is also included, which includes a tensioning crossbeam 5091 and a tensioning diagonal bar 5092;

[0060] The ends of the overlapping longitudinal beams (including long and short longitudinal beams) form end-opening snap-fit ​​grooves. The snap-fit ​​grooves can be openings directly at the ends of the overlapping longitudinal beams, or they can be formed by welding other components, which will not be elaborated here. The tensioning crossbeam 5091 is longitudinally engaged in the snap-fit ​​grooves. One end of the tensioning diagonal rod 5092, which can swing along the longitudinal vertical plane, is hinged to the bottom of the basket, and the other end passes through the through hole on the tensioning crossbeam and is detachably connected to the tensioning crossbeam 5091, thus providing tension reinforcement to the bottom of the basket. The detachable connection structure can adopt the mechanical structure of existing technology, which will not be elaborated here. In this embodiment, the end of the tensioning diagonal rod 5092 that passes through the tensioning crossbeam 5091 is provided with an external thread, and is locked by a nut after passing through. As shown in the figure, there are two tensioning diagonal rods 5092, which are symmetrically located on both sides of the cover beam in the transverse direction to provide tension to the bottom of the basket, further increasing the overall integrity and reliability of the basket.

[0061] like Figure 5 As shown, the tensioning longitudinal beam 505 is an I-beam, and the tensioning member 4 is an I-beam. The tensioning member 4 and the tensioning longitudinal beam 505 are connected by steel plates attached to both sides of the web and by multiple sets of bolts. After installation, the structure is simple and stable. Of course, the tensioning longitudinal beam can also be an I-beam, and the tensioning member can be two strip steel plates attached to both sides of the web of the tensioning longitudinal beam and connected by multiple sets of bolts; the purpose of the invention can be achieved in the same way.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for secondary prestressing tensioning of a cap beam, characterized in that: Includes the following steps: a. Construct and install the operating platform for secondary prestressing tensioning on the cap beam: a1 lifts two baskets used to form the operating platform, with the lifting height of the two baskets corresponding to the two ends of the cap beam; a2 is tensioned from both ends of the cap beam by two opposing suspended baskets, and the opposing tension, the weight of the suspended baskets themselves, and the support at the ends of the cap beam are used to fix the suspended baskets to both ends of the cap beam, which is used to provide an operating platform for the secondary tensioning of the cap beam prestress; forming the tensioning member of the opposing tensioning is suspended and located between the box beams on both sides of the cap beam. b. Using the tensioning members from step a to provide a safety belt for the foundation for safe suspension, the box girder is positioned on the cap beam during construction. c. After all the box girders are in place, the cap beams are subjected to secondary prestressing tensioning on the tensioning platform. d. After the secondary prestressing tensioning is completed, the operating platform is dismantled; The suspended basket includes a basket and an overlapping longitudinal beam. The overlapping longitudinal beam includes a long longitudinal beam with one end fixed to the far edge of the basket and extending to the upper surface of the cover beam after being in place, and a short longitudinal beam with one end fixed to the near edge of the basket and extending to the upper surface of the cover beam after being in place. In step a1, the lower surface of the overlapping longitudinal beam is attached to the upper surface of the cover beam. A tensioning vertical beam is fixed to the lap longitudinal beam and extends upwards, and a tensioning longitudinal beam extends from the top of the tensioning vertical beam toward the opposite direction; in step a1, the tensioning longitudinal beams of the baskets located at both ends of the cap beam are connected by tensioning members to form tension; The top of the tensioning vertical beam and the far end of the basket are also fixedly provided with tensioning inclined beams; It also includes a tensioning and fixing assembly, which includes a tensioning crossbeam and a tensioning diagonal bar; The end of the overlapping longitudinal beam forms a snap-fit ​​groove with an end opening. The tensioning crossbeam is snapped into the snap-fit ​​groove along the longitudinal direction. One end of the tensioning diagonal rod, which can swing along the longitudinal vertical plane, is hinged to the bottom of the basket. The other end passes through the through hole on the tensioning crossbeam and is detachably connected to the tensioning crossbeam, thus forming a tensioning reinforcement for the bottom of the basket.

2. The prestressed secondary tensioning construction method for the cap beam according to claim 1, characterized in that: The short longitudinal beams consist of several beams arranged side by side in the middle of the basket. The long longitudinal beams consist of several beams arranged side by side in the middle of the basket. An overlapping crossbeam is fixedly connected between adjacent overlapping longitudinal beams. In step a1, the lower surface of the overlapping crossbeam is attached to the upper surface of the cover beam.

3. The prestressed secondary tensioning construction method for the cap beam according to claim 2, characterized in that: The lower surfaces of the overlapping longitudinal beams and overlapping transverse beams are roughened; the center of gravity of the suspended platform is located on one side of the overlapping longitudinal beams.

4. The prestressed secondary tensioning construction method for the cap beam according to claim 2, characterized in that: It also includes an anti-rollover beam assembly located at the bottom of the basket. The anti-rollover beam assembly includes at least two anti-rollover beams arranged horizontally side by side. In step a2, after being tensioned in opposite directions, the anti-rollover beams can be driven to abut against the lower surface of the cover beam to form a structure that resists the lateral rollover of the basket.

5. The prestressed secondary tensioning construction method for the cap beam according to claim 4, characterized in that: The basket includes a supporting body, a frame panel, and a bottom plate. The supporting body is a cuboid frame composed of bottom longitudinal beams, bottom transverse beams, frame vertical beams, top longitudinal beams, and top transverse beams. The bottom plate is fixed to the bottom of the cuboid frame to form the bottom of the operating platform. The frame panel is fixed between adjacent frame vertical beams and leaves room for the secondary tensioning of the prestressed cap beam. The long side of the cuboid frame is located horizontally, and auxiliary vertical beams are provided between the horizontally parallel frame vertical beams, with a position reserved near the basket for the secondary tensioning of the prestressed cap beam; the two ends of the auxiliary vertical beams are fixed to the corresponding top and bottom horizontal beams of the frame, respectively; the long longitudinal beam is fixed to the corresponding frame vertical beam or the corresponding auxiliary vertical beam at the far end; and the short longitudinal beam is fixed to the frame vertical beam, the corresponding auxiliary vertical beam, or the corresponding top horizontal beam at the near end. Auxiliary longitudinal beams for the bottom of the frame are also arranged in parallel between the longitudinal beams for the bottom of the frame, and the two ends of the auxiliary longitudinal beams for the bottom of the frame are respectively fixed to the corresponding transverse beams for the bottom of the frame.

6. The prestressed secondary tensioning construction method for the cap beam according to claim 5, characterized in that: The anti-tipping beam assembly also includes an outer cylindrical beam, the anti-tipping beam being fitted inside the outer cylindrical beam and capable of being driven to reciprocate longitudinally; the outer cylindrical beam is hinged to the basket and can swing along a vertical plane. In step a2, the anti-tipping beam is driven to slide towards the bottom of the cover beam, and the outer cylindrical beam is driven to swing so that the anti-tipping beam abuts against the lower surface of the cover beam, locking the inner end of the anti-tipping beam to the basket.

7. The prestressed secondary tensioning construction method for the cap beam according to claim 1, characterized in that: The connection between the overlapping longitudinal beam and the basket is a detachable fixed connection.

8. The prestressed secondary tensioning construction method for the cap beam according to claim 4, characterized in that: The tensioned longitudinal beam is inclined at a small angle upwards towards the opposite side.

9. The prestressed secondary tensioning construction method for the cap beam according to claim 1, characterized in that: The tensioning longitudinal beam is an I-beam, the tensioning member is an I-beam, and the tensioning member and the tensioning longitudinal beam are connected by steel plates attached to both sides of the web and by multiple sets of bolts. Alternatively, the tensioning longitudinal beam is an I-beam, and the tensioning member is two strip steel plates attached to both sides of the web of the tensioning longitudinal beam and connected by multiple sets of bolts.

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