Hoisting-dragging-positioning construction method for bent cap under low-clearance bridge

Abstract

A hoisting, dragging and positioning construction method for installing a bent cap under a low-clearance bridge. A first pier 11 is constructed under the bridge, and a second pier 12 is constructed no

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of engineering construction, and in particular to a hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge. BACKGROUND

[0002] An overpass, or "three-dimensional intersection bridge", is a stacked, multidirectional and non-interfering modern land bridge built at important traffic intersections of cities. It is mainly intended to eliminate the conflict of cross-road traffic by means of spatial isolation, ensuring free-flowing movement of straight-going vehicles on two crossing roads. In fact, the overpass makes the flat road three-dimensional, so that it can accommodate more traffic.

[0003] When the overpass is built, multiple pairs of piers are constructed sequentially along a predetermined direction. A steel bent cap is erected on each pair of piers to support an upper structure of the bridge. Subsequent construction is performed on the steel bent cap.

[0004] For the above related art, when a new viaduct is built under an existing bridge, and a crane is used to lift the steel bent cap onto the bridge pier, the crane hook is affected by the existing bridge above and cannot directly lift the steel cap beam in place. SUMMARY

[0005] In order to mount a steel bent cap under the existing bridge and the low-clearance condition, the present disclosure provides a hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge.

[0006] The hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge provided by the present disclosure employs the following technical solutions:

[0007] A hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge includes the following steps:

[0008] SI: constructing a pier: respectively constructing a first pier and a second pier at a predetermined position under a bridge and a predetermined position out of the bridge;

[0009] S2: erecting a support: erecting a first support at a side of the first pier close to the second pier, and erecting a second support around the second pier, the first support and the second support each being provided with an auxiliary sliding assembly;

[0010] S3: hoisting a steel bent cap: hoisting the steel bent cap to the auxiliary sliding assembly on the first support and the auxiliary sliding assembly on the second support;

[0011] S4: dragging and positioning the steel bent cap: dragging the steel bent cap with the auxiliary sliding assembly until ends of the steel bent cap are respectively located above the first pier and the second pier, and positioning and fixing the steel bent cap on the pier; and

[0012] S5: dismantling the support, and restoring traffic.

[0013] According to the above technical solution, with the support at the pier, after the steel bent cap is hoisted to the support, the support can bear the steel bent cap under the low-clearance condition. By changing a positioning method from direct hoisting to translation on the support, the present disclosure gets rid of limitations of the existing bridge on hoisting of the crane for the steel bent cap, and can allow the steel bent cap to slide to the top of the pier, thereby completing construction of the steel bent cap. Meanwhile, the support can bear the steel bent cap stably. Compared with the hoisting of the crane, the present disclosure can allow the steel bent cap to slide in place on the support according to a predetermined angle, without excessive adjustment, thereby achieving better transportation stability.

[0014] Preferably, the auxiliary sliding assembly includes a first electric hoist, a supporting member, and a polytetrafluoroethylene (PTFE) plate; the first electric hoist is hung on the first support; the first electric hoist is connected to a first steel wire rope; an end of the first steel wire rope away from the first electric hoist is fixedly connected to the steel bent cap; the supporting member is fixedly mounted on a transverse frame of the support; the PTFE plate is provided at a top of the supporting member; and a connector is provided between the first pier and the first support;

[0015] the step S3 specifically includes: hoisting the steel bent cap to supporting members of two supports; and

[0016] the step S4 specifically includes: mounting the auxiliary sliding assembly in place, starting the first electric hoist to drag the steel bent cap, until the end of the steel bent cap is aligned at a top of the pier, mounting a jack at a top of the support, raising the steel bent cap with the jack, dismantling the supporting member, and positioning the steel bent cap on the pier through the jack.

[0017] According to the above technical solution, firstly, when the steel bent cap is hoisted to the PTFE plate on the support, friction between the steel bent cap and the support is reduced through a smooth plate surface, facilitating slide of the steel bent cap. Meanwhile, the PTFE plate is used to reduce a frictional force between the steel bent cap and the support, and the plate is not prone to deformation, such that a higher bearing capacity can be provided, and damage of the steel bent cap under the action of gravity to other structures capable of reducing the sliding frictional force is mitigated, thereby improving the bearing stability.

[0018] Secondly, in order to adjust the steel bent cap such that the sliding steel bent cap can be accurately positioned on the pier, the supporting member is provided, and a bottom of the supporting member is higher than the top of the pier. The steel bent cap can be slid freely on the pier through the supporting member to a predetermined positioning position. Then, the steel bent cap is lifted through the jack.

[0019] Thirdly, the first support and the first pier are connected through the connector. This improves the stability of the first support, such that the steel bent cap can be stably pulled by the first electric hoist on the first support, thereby mitigating structural damage to the first support under the action of a counter-acting force.

[0020] Preferably, two vertical frames are fixedly provided at the top of the support; the two vertical frames are respectively located at two sides of the support along a length direction of the steel bent cap; and sides of the two vertical frames close to one another each are provided with a limiting roller;

[0021] the step S2 specifically includes: after a main body of the support is built, erecting the vertical frame at one side; and

[0022] the step S3 specifically includes: after the steel bent cap is hoisted to the support in place, erecting the vertical frame at the other side and the limiting roller.

[0023] According to the above technical solution, the two sides of the steel bent cap along the length direction in sliding abut against the limiting rollers on the vertical frames. This reduces the sliding deviation and improves the sliding stability. Meanwhile, after the vertical frame at one side is erected, the steel bent cap is directly hoisted from the side to the support, thereby reducing slide of the steel bent cap on the support to accelerate the construction progress.

[0024] Preferably, the connector includes a connecting frame and an encasement plate; the encasement plate is sleeved on the top of the pier; a plurality of uplift-resistant pins are provided on an inner wall of the encasement plate; and the connecting frame includes one end connected to the encasement plate of the first support, and the other end connected to the first support; and

[0025] the step SI specifically further includes: when the pier is cast, presetting a boss at the top of the pier, mounting the encasement plate on the boss, and pouring concrete into the encasement plate to fix the encasement plate on the pier.

[0026] Since the pier is formed by concrete casting, an external facade of the pier lacks a material connected to the support. According to the above technical solution, the encasement plate is sleeved on the pier, and the concrete is poured into the encasement plate, such that the encasement can be fixed on the pier. Then, two ends of the connecting frame are respectively welded on the encasement plate and the first support to reinforce the first support. Meanwhile, the encasement plate can be welded to the steel bent cap to form temporary fixation, reducing movement of the positioned steel bent cap, and facilitating subsequent reinforcement.

[0027] Preferably, the encasement plate includes two mutually spliced individual units; the pier is provided with a mounting groove along a circumferential direction of the boss; and the encasement plate is provided with a fastener for locking the two mutually spliced individual units; and

[0028] the encasement plate is mounted on the boss specifically as follows: respectively hoisting the two individual units to two sides of the boss in a horizontal direction, sliding the individual unit along the horizontal direction and wedging the individual unit into the pier until the individual unit is located directly above the mounting groove, positioning the individual unit and locking the two individual units with the fastener.

[0029] A reinforcement cage is reserved at a predetermined mounting position of the encasement plate on the pier. For an excessively small spacing between a top of the reinforcement cage and the existing bridge, it is hard to directly sleeve the whole encasement plate on the top of the pier. According to the above technical solution, the encasement plate is divided into two individual units. The individual unit is wedged into the top of the pier from the side, and locked by the fastener, thereby realizing mounting of the encasement plate. By splitting the encasement plate and mounting the encasement plate from the side, the mounting method gets rid of limitations of the existing bridge on the encasement plate in a vertical direction, and facilitates the mounting of the encasement plate.

[0030] Preferably, a fixing frame is provided on the first pier; a fixed hole for allowing the steel bent cap to penetrate through is formed in the fixing frame; the fixing frame is provided with a second electric hoist; a position of the second electric hoist is higher than a position of the first electric hoist; a second steel wire rope is provided on the second electric hoist; and an end of the second steel wire rope away from the second electric hoist is connected to the steel bent cap; and

[0031] the step S4 specifically further includes: synchronously starting the first electric hoist and the second electric hoist, until the steel bent cap is slid in place.

[0032] According to the above technical solution, the second electric hoist is provided at the position higher than the position of the first electric hoist, such that a tensile force for the steel bent cap in the horizontal direction is increased, further dragging the steel bent cap to accelerate the construction progress.

[0033] Preferably, a side of the fixing frame close to the second support is provided with a telescopic rod and an elastic member; the telescopic rod includes one end detachably connected to the fixing frame, and the other end fixedly connected to the elastic member; the steel bent cap is detachably provided with a fixing member; a fixing groove is formed in the fixing member; an opening of the fixing groove faces the first support and directly faces the elastic member; and when the steel bent cap is dragged in place, the elastic member is inserted into the fixing member through the fixing groove; and

[0034] the step S4 specifically further includes: starting the first electric hoist and the second electric hoist, until the elastic member is inserted into the fixing member.

[0035] After the first electric hoist and the second electric hoist are used together to drag the steel bent cap, the steel bent cap is slid on the smooth PTFE plate. The steel bent cap has large inertia for the large weight. It may be slid excessively and misaligned at the pier after dragged. According to the above technical solution, after the steel bent cap is slid in place, the fixing member abuts against the elastic member. Kinetic energy of the steel bent cap is absorbed by elastic deformation of the elastic member and the telescopic rod, to mitigate secondary movement of the steel bent cap after the steel bent cap is slid in place.

[0036] Preferably, a pouring groove is formed circumferentially in the fixing frame along a cross-sectional direction of the fixed hole; a connecting rod is provided in the pouring groove; and an end of the connecting rod away from a junction is configured to connect the steel bent cap; and

[0037] after the step S4, the hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge specifically further includes: after the steel bent cap is dragged in place, fixedly connecting the connecting rod to the steel bent cap, using a plugging assembly to plug a gap between the fixing frame and the steel bent cap as well as gaps at two sides of the pouring groove, and pouring concrete into the pouring groove until the pouring groove is filled with the concrete.

[0038] According to the above technical solution, after the steel bent cap is positioned on the pier, the connecting rod is connected to the steel bent cap to serve as the reinforcement cage. Then, the plugging assembly is used to plug the gap between the fixing frame and the steel bent cap. After the concrete is poured, the temporary fixing frame serves as a fixing structure between the steel bent cap and the pier to reinforce connection stability between the steel bent cap and the pier.

[0039] Preferably, the plugging assembly includes a first air bag and a driving rod; at each of two ends of the fixing groove along a length direction of the steel bent cap, the fixing frame is provided with the first air bag; a driving groove is formed in the fixing frame along a vertical direction and located in the fixing groove and directly below the steel bent cap; the driving rod is slidably mounted on the fixing frame through the driving groove; a second air bag is provided at a bottom of the driving groove; the second air bag communicates with the first air bag through an air tube; and an end of the driving rod away from the steel bent cap abuts against the second air bag; and

[0040] the plugging assembly is used specifically as follows: aligning the steel bent cap at the driving rod, and positioning the steel bent cap on the fixing frame.

[0041] According to the above technical solution, after the steel bent cap is dragged in place and the steel bent cap is positioned with the jack, the bottom of the steel bent cap abuts against the driving rod, such that the driving rod is slid in the driving groove. The driving rod squeezes the second air bag to transmit air in the second air bag to the first air bag through the air tube, such that the first air bag expands to abut against a sidewall of the steel bent cap for sealing. By this time, the concrete can be poured between two first air bags to fix the steel bent cap and the pier. The plugging structure makes use of a pressure when the steel bent cap is positioned as a power source, thereby driving the air to transmit. Meanwhile, the expanded air bag serves as the plugging structure. On one hand, the air bag can be tightly attached to the steel bent cap to reduce the gap, achieving a better plugging effect. On the other hand, the air bag expands quickly, which realizes plugging quickly to accelerate the construction progress.

[0042] In conclusion, the present disclosure has at least one of the following beneficial technical effects:

[0043] 1. By changing a positioning method from direct hoisting to translation on the support, the present disclosure gets rid of limitations of the existing bridge on hoisting of the crane for the steel bent cap, and can allow the steel bent cap to slide to the top of the pier, thereby completing construction of the steel bent cap.

[0044] 2. The encasement plate is divided into two individual units. The individual unit is wedged into the top of the pier from the side, and locked by the fastener, thereby realizing mounting of the encasement plate. By splitting the encasement plate and mounting the encasement plate from the side, the mounting method gets rid of limitations of the existing bridge on the encasement plate in a vertical direction, and facilitates the mounting of the encasement plate.

[0045] 3. The connecting rod is connected to the steel bent cap to serve as the reinforcement cage. Then, the plugging assembly is used to plug the gap between the fixing frame and the steel bent cap. After the concrete is poured, the temporary fixing frame serves as a fixing structure between the steel bent cap and the pier to reinforce connection stability between the steel bent cap and the pier. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1 is a schematic view of a state illustrating mounting of a pier according to an embodiment of the present disclosure;

[0047] FIG. 2 is a schematic structural view of a pier and an encasement plate according to an embodiment of the present disclosure;

[0048] FIG. 3 is a top view of an encasement plate according to an embodiment of the present disclosure;

[0049] FIG. 4 is a schematic view of a state illustrating mounting of a support according to an embodiment of the present disclosure;

[0050] FIG. 5 is an enlarged view of A shown in FIG. 4 according to an embodiment of the present disclosure;

[0051] FIG. 6 is a schematic view of a state illustrating that a steel bent cap is positioned completely according to an embodiment of the present disclosure;

[0052] FIG. 7 is a schematic view of a state illustrating that a steel bent cap is positioned on a fixing frame according to an embodiment of the present disclosure;

[0053] FIG. 8 is a schematic structural view of a fixing frame according to an embodiment of the present disclosure; and

[0054] FIG. 9 is a sectional view of a fixing frame according to an embodiment of the present disclosure.

[0055] Reference numerals:

[0056] 1: pier, 11: first pier, 12: second pier, 13: boss, 14: connecting frame, 2: encasement plate, 21: uplift-resistant pin, 22: individual unit, 23: fastener, 3: support, 31: first support, 32: second support, 33: vertical frame, 331: limiting roller, 4: auxiliary sliding assembly, 41: first electric hoist, 42: supporting member, 43: first steel wire rope, 5: steel bent cap, 6: fixing frame, 61: fixed hole, 62: second electric hoist, 63: second steel wire rope, 64: telescopic rod, 65: elastic member, 66: pouring groove, 67: connecting rod, 7: plugging assembly, 71: first air bag, 72: driving rod, and 73: second air bag. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0057] The present disclosure will be further described in detail below with reference to FIGS. 1-9.

[0058] An embodiment of the present disclosure provides a hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge. Referring to FIG. 1 and FIG. 2, the construction method includes the following steps:

[0059] SI: A pier 1 is constructed: A formwork of a first pier 11 and a formwork of a second pier 12 are respectively erected at a predetermined position under an existing bridge and a predetermined position out of the bridge. Concrete is poured into each formwork. After the concrete is solidified, the first pier 11 and the second pier 12 are formed.

[0060] SI. 1: When the pier 1 is cast, a boss 13 is preset at a top of the pier 1, so as to mount an encasement plate 2 on the boss 13.

[0061] SI.2: The encasement plate 2 is mounted on the boss 13. The concrete is poured into the encasement plate 2 to fix the encasement plate 2 on the pier 1. A plurality of uplift-resistant pins 21 are provided on an inner wall of the encasement plate 2. After the concrete is poured, a contact area between the concrete and the encasement plate 2 is increased through the uplift-resistant pins 21, such that a connection strength between a body of the pier 1 and the encasement plate 2 is improved, laying a foundation for connection between the pier 1 and a support 3.

[0062] Referring to FIG. 2 and FIG. 3, the encasement plate 2 includes two mutually spliced individual units 22. In the embodiment, the individual unit 22 has an L-shaped cross-section. The pier 1 is provided with a mounting groove along a circumferential direction of the boss 13. The encasement plate 2 is provided with a fastener 23 for locking the two mutually spliced individual units 22. In the embodiment, the fastener 23 is a bidirectional threaded rod. Different threaded segments of the bidirectional threaded rod are respectively threadedly connected to the two individual units 22. When a bottom edge of the encasement plate 2 is inserted into the mounting groove, a side bottom edge of the individual unit 22 of the encasement plate 2 abuts against the boss 13. When the two individual units 22 are to be locked, screwing the bidirectional threaded rod can drive the two individual units 22 to get close to each other. Under an action of abutment of the boss 13, the individual unit 22 is locked.

[0063] In the step SI.2, the encasement plate 2 is mounted on the boss 13 specifically as follows: The two individual units 22 are respectively hoisted to two sides of the boss 13 in a horizontal direction. The individual unit 22 is slid along the horizontal direction and wedged into the pier 1 until the individual unit 22 is located directly above the mounting groove. By this time, the individual unit 22 is positioned into the mounting groove, and the two individual units 22 are locked with the fastener 23.

[0064] S2: The support 3 is erected: Referring to FIG. 4, a first support 31 is erected at a side of the first pier 11 close to the second pier 12. A predetermined construction position of the first support 31 is a maximum position to which an end of a steel crossbeam close to the bridge reaches in hoisting of a crane. A second support 32 is provided around the second pier 12. The first support 31 and the second support 32 each are provided with an auxiliary sliding assembly 4. A connector is provided between the first pier 11 and the first support 31.

[0065] The connector includes a connecting frame 14 and the encasement plate 2. The connecting frame 14 includes one end connected to the encasement plate 2 of the first support 31, and the other end connected to the first support 31. Referring to FIG. 5, two vertical frames 33 are fixedly provided at a top of the support 3. The two vertical frames 33 are respectively located at two sides of the support 3 along a length direction of the steel bent cap 5. Sides of the two vertical frames 33 close to one another each are provided with a limiting roller 331.

[0066] S2.1: Referring to FIG. 4, after a main body of the support 3 is erected completely, the vertical frame 33 at one side is provided first. When the steel bent cap 5 is hoisted, the steel bent cap 5 can be directly hoisted to the support 3 at the side not provided with the vertical frame 33, omitting a process for driving the steel bent cap 5 to slide.

[0067] S3: The steel bent cap 5 is hoisted: Referring to FIG. 5 and FIG. 6, the steel bent cap 5 is hoisted to the auxiliary sliding assembly 4 on the first support 31 and the auxiliary sliding assembly on the second support 32.

[0068] Referring to FIG. 5 and FIG. 6, the auxiliary sliding assembly 4 includes a first electric hoist 41, a supporting member 42, and a PTFE plate. The first electric hoist 41 is hung on the first support 31. The first electric hoist 41 is connected to a first steel wire rope 43. An end of the first steel wire rope 43 away from the first electric hoist 41 is fixedly connected to the steel bent cap 5. The supporting member 42 is fixedly mounted on a transverse frame of the support 3. A top of the supporting member 42 is higher than the top of the pier 1. The PTFE plate is provided at the top of the supporting member 42.

[0069] S3.1: The steel bent cap 5 is hoisted to supporting members 42 of two supports 3.

[0070] S3.2: After the steel bent cap 5 is hoisted to the supporting member 42 of the support 3 in place, the vertical frame 33 at the other side and the limiting roller 331 are erected. Through limiting rollers 331 at two sides, a condition in which the sliding path is deviated when the steel bent cap 5 is slid is reduced.

[0071] S4: The steel bent cap 5 is dragged and positioned: The steel bent cap 5 is dragged with the auxiliary sliding assembly 4 until ends of the steel bent cap 5 are respectively located above the first pier 11 and the second pier 12. The steel bent cap 5 is positioned and fixed on the pier 1.

[0072] The step S4 specifically includes: Referring to FIG. 6, the auxiliary sliding assembly 4 is mounted in place. The steel bent cap 5 is dragged, until the end of the steel bent cap 5 is aligned at the top of the pier 1. A jack is mounted at the top of the support 3. The steel bent cap 5 is raised with the jack, until a bottom of the steel bent cap 5 does not abut against the PTFE plate on the supporting member 42. The supporting member 42 is dismantled, and the steel bent cap 5 is lowered through the jack and positioned on the pier 1. By this time, the steel bent cap 5 is fixed.

[0073] Referring to FIG. 7, a fixing frame 6 is provided at a top of the first pier 11. A fixed hole 61 for allowing the steel bent cap 5 to penetrate through is formed in the fixing frame. The fixing frame 6 is provided with a second electric hoist 62. A position of the second electric hoist 62 is higher than a position of the first electric hoist 41. A second steel wire rope 63 is provided on the second electric hoist 62. An end of the second steel wire rope 63 away from the second electric hoist 62 is connected to the steel bent cap 5.

[0074] S4.1: The first electric hoist 41 and the second electric hoist 62 are synchronously started, until the steel bent cap 5 is slid in place.

[0075] Referring to FIG. 8, a side of the fixing frame 6 close to the second support 32 is provided with a telescopic rod 64 and an elastic member 65. The telescopic rod 64 includes one end detachably connected to the fixing frame 6, and the other end fixedly connected to the elastic member 65. The steel bent cap 5 is detachably provided with a fixing member. A fixing groove is formed in the fixing member. An opening of the fixing groove faces the first support 31 and directly faces the elastic member 65. When the steel bent cap 5 is dragged in place, the elastic member 65 is inserted into the fixing member through the fixing groove. Since a tensile force for the steel bent cap 5 in the horizontal direction is increased, and the steel bent cap 5 has large inertia, in order to brake the sliding steel bent cap 5, the steel bent cap slid in place abuts against the fixing groove through the elastic member 65, thus braking the whole steel bent cap 5. Meanwhile, through deformation of the elastic member 65, damage caused by an impact of the elastic member 65 after abutment is reduced.

[0076] After the step S4.1, the first electric hoist 41 and the second electric hoist 62 are started, until the elastic member 65 is inserted into the fixing member.

[0077] Referring to FIG. 8 and FIG. 9, a pouring groove 66 is formed circumferentially in the fixing frame 6 along a cross-sectional direction of the fixed hole 61. A connecting rod 67 is provided in the pouring groove 66. An end of the connecting rod 67 away from a junction is configured to connect the steel bent cap 5.

[0078] S4.2: After the steel bent cap 5 is dragged in place, the connecting rod 67 is fixedly connected to the steel bent cap 5. A plugging assembly 7 is used to plug a gap between the fixing frame 6 and the steel bent cap 5 and gaps at two sides of the pouring groove 66. Concrete is poured into the pouring groove 66 until the pouring groove 66 is filled with the concrete.

[0079] Referring to FIG. 9, the plugging assembly 7 includes a first air bag 71 and a driving rod 72. At each of two ends of the fixing groove along a length direction of the steel bent cap 5, the fixing frame 6 is provided with the first air bag 71. A driving groove is formed in the fixing frame 6 along a vertical direction and located in the fixing groove and directly below the steel bent cap 5. The driving rod 72 is slidably mounted on the fixing frame 6 through the driving groove. A second air bag 73 is provided at a bottom of the driving groove. The second air bag 73 communicates with the first air bag 71 through an air tube. An end of the driving rod 72 away from the steel bent cap 5 abuts against the second air bag 73.

[0080] The plugging assembly 7 is used specifically as follows: The steel bent cap 5 is aligned at the driving rod 72, and the steel bent cap 5 is positioned on the fixing frame 6. The driving rod 72 squeezes the second air bag 73 to transmit air to the first air bag 71, such that the first air bag 71 expands to abut against the steel bent cap 5, thereby plugging the gap between the steel bent cap 5 and the fixing frame 6. In order to facilitate pouring of the concrete, the fixing frame 6 is taken as a formwork for the concrete. After the concrete is solidified, the pier 1 is connected to the steel bent cap 5, omitting the process for fixing the steel bent cap 5.

[0081] S5: The support 3 is dismantled, and traffic is restored.

[0082] The above are preferred embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present disclosure shall fall within the protection scope of the present disclosure.

Claims

1. A hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge, comprising the following steps:SI: constructing a pier (1): respectively constructing a first pier (11) and a second pier (12) at a predetermined position under a bridge and a predetermined position out of the bridge;S2: erecting a support (3): erecting a first support (31) at a side of the first pier (11) close to the second pier (12), and erecting a second support (32) around the second pier (12), the first support (31) and the second support (32) each being provided with an auxiliary sliding assembly (4);S3: hoisting a steel bent cap (5): hoisting the steel bent cap (5) to the auxiliary sliding assembly (4) on the first support (31) and the auxiliary sliding assembly (4) on the second support (32);S4: dragging and positioning the steel bent cap (5): dragging the steel bent cap (5) with the auxiliary sliding assembly (4) until ends of the steel bent cap (5) are respectively located above the first pier (11) and the second pier (12), and positioning and fixing the steel bent cap (5) on the pier (1); andS5: dismantling the support (3), and restoring traffic.

2. The hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge according to claim 1, wherein the auxiliary sliding assembly (4) comprises a first electric hoist (41), a supporting member (42), and a polytetrafluoroethylene (PTFE) plate; the first electric hoist (41) is hung on the first support (31); the first electric hoist (41) is connected to a first steel wire rope (43); an end of the first steel wire rope (43) away from the first electric hoist (41) is fixedly connected to the steel bent cap (5); the supporting member (42) is fixedly mounted on a transverse frame of the support (3); the PTFE plate is provided at a top of the supporting member (42); and a connector is provided between the first pier (11) and the first support (31);the step S3 specifically comprises: hoisting the steel bent cap (5) to supporting members (42) of two supports (3); andthe step S4 specifically comprises: mounting the auxiliary sliding assembly (4) in place, starting the first electric hoist (41) to drag the steel bent cap (5), until the end of the steel bent cap (5) is aligned at a top of the pier (1), mounting a jack at a top of the support (3), raising the steel bent cap (5) with the jack, dismantling the supporting member (42), and positioning the steel bent cap (5) on the pier (1) through the jack.

3. The hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge according to claim 2, wherein two vertical frames (33) are fixedly provided at the top of the support (3); the two vertical frames (33) are respectively located at two sides of the support (3) along a length direction of the steel bent cap (5); and sides of the two vertical frames (33) close to one another each are provided with a limiting roller (331);the step S2 specifically comprises: after a main body of the support (3) is built, erecting the vertical frame (33) at one side; andthe step S3 specifically comprises: after the steel bent cap (5) is hoisted to the support (3) in place, erecting the vertical frame (33) at the other side and the limiting roller (331).

4. The hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge according to claim 2, wherein the connector comprises a connecting frame (14) and an encasement plate (2); the encasement plate (2) is sleeved on the top of the pier (1); a plurality of uplift-resistant pins (21) are provided on an inner wall of the encasement plate (2); and the connecting frame (14) comprises one end connected to the encasement plate (2) of the first support (31), and the other end connected to the first support (31); andthe step SI specifically further comprises: when the pier (1) is cast, presetting a boss (13) at the top of the pier (1), mounting the encasement plate (2) on the boss (13), and pouring concrete into the encasement plate (2) to fix the encasement plate (2) on the pier (1).

5. The hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge according to claim 4, wherein the encasement plate (2) comprises two mutually spliced individual units (22); the pier (1) is provided with a mounting groove along a circumferential direction of the boss (13); and the encasement plate (2) is provided with a fastener (23) for locking the two mutually spliced individual units (22); andthe encasement plate (2) is mounted on the boss (13) specifically as follows: respectively hoisting the two individual units (22) to two sides of the boss (13) in a horizontal direction, sliding the individual unit (22) along the horizontal direction and wedging the individual unit (22) into the pier (1) until the individual unit (22) is located directly above the mounting groove, positioning the individual unit (22) and locking the two individual units (22) with the fastener (23).

6. The hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge according to claim 2, wherein a fixing frame (6) is provided on the firstpier (11); a fixed hole (61) for allowing the steel bent cap (5) to penetrate through is formed in the fixing frame; the fixing frame (6) is provided with a second electric hoist (62); a position of the second electric hoist (62) is higher than a position of the first electric hoist (41); a second steel wire rope (63) is provided on the second electric hoist (62); and an end of the second steel wire rope (63) away from the second electric hoist (62) is connected to the steel bent cap (5); andthe step S4 specifically further comprises: synchronously starting the first electric hoist (41) and the second electric hoist (62), until the steel bent cap (5) is slid in place.

7. The hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge according to claim 6, wherein a side of the fixing frame (6) close to the second support (32) is provided with a telescopic rod (64) and an elastic member (65); the telescopic rod (64) comprises one end detachably connected to the fixing frame (6), and the other end fixedly connected to the elastic member (65); the steel bent cap (5) is detachably provided with a fixing member; a fixing groove is formed in the fixing member; an opening of the fixing groove faces the first support (31) and faces directly the elastic member (65); and when the steel bent cap (5) is dragged in place, the elastic member (65) is inserted into the fixing member through the fixing groove; andthe step S4 specifically further comprises: starting the first electric hoist (41) and the second electric hoist (62), until the elastic member (65) is inserted into the fixing member.

8. The hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge according to claim 7, wherein a pouring groove (66) is formed circumferentially in the fixing frame (6) along a cross-sectional direction of the fixed hole (61); a connecting rod (67) is provided in the pouring groove (66); and an end of the connecting rod (67) away from a junction is configured to connect the steel bent cap (5); andafter the step S4, the hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge specifically further comprises: after the steel bent cap (5) is dragged in place, fixedly connecting the connecting rod (67) to the steel bent cap (5), using a plugging assembly (7) to plug a gap between the fixing frame (6) and the steel bent cap (5) as well as gaps at two sides of the pouring groove (66), and pouring concrete into the pouring groove (66) until the pouring groove (66) is filled with the concrete.

9. The hoisting-dragging-positioning construction method for a bent cap under a low-clearance bridge according to claim 8, wherein the plugging assembly (7) comprises a first air bag (71) and a driving rod (72); at each of two ends of the fixing groove along a lengthdirection of the steel bent cap (5), the fixing frame (6) is provided with the first air bag (71); a driving groove is formed in the fixing frame (6) along a vertical direction and located in the fixing groove and directly below the steel bent cap (5); the driving rod (72) is slidably mounted on the fixing frame (6) through the driving groove; a second air bag (73) is provided at a bottom of the driving groove; the second air bag (73) communicates with the first air bag (71) through an air tube; and an end of the driving rod (72) away from the steel bent cap (5) abuts against the second air bag (73); andthe plugging assembly (7) is used specifically as follows: aligning the steel bent cap (5) at the driving rod (72), and positioning the steel bent cap (5) on the fixing frame (6).

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