A cantilever bridge head slab

Abstract

The invention discloses a cantilever bridgehead slab, which adopts a two-section bridgehead slab. The first section slab is connected with the bridge abutment foundation to form a cantilever shape. The thickness of the slab gradually decreases from the root of the cantilever to the end, and the lower inner angle of the slab is designed to be a round chamfer. A bending-resistant steel plate is arranged in the vertical section of the first section slab, a negative bending moment steel plate is arranged in the cantilever section of the first section slab, and an expansion joint device is installed between the near-bridge end of the first section slab and the beam body; the second section slab is arranged from directly below the cantilever end of the first section slab, and the first section slab and the second section slab are flexibly connected through a conversion system. The starting end of the second section slab is connected to a steel roller and extends into the bottom plate of the conversion system; a row of fixed ribbed steel pipes and three rows of retractable hollow steel pipes are arranged in each group along the transverse bridge direction of the top plate of the conversion system, and a total of three groups are arranged. The invention can convert the acting force into potential energy or horizontal kinetic energy and then release the bridgehead slab conversion system, avoid the phenomenon of excessive bending moment of the cantilever structure due to roadbed settlement, and realize the smooth transition of vehicles from the bridge to the roadbed.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge engineering, and in particular relates to a cantilever bridge head slab. Background Art

[0002] The vehicle jumping at the bridge head has always been one of the common quality problems that construction units have paid attention to, and it has also been a problem that designers have been troubled by for a long time. In the design of expressways, the conventional connection method for the transition between bridges and roadbeds is: to set an expansion joint between the beam and the abutment, set a bracket on the back of the abutment, and set up an integral cast-in-place bridge head slab on the bracket to complete the transition between the bridge and the roadbed. The above design method has two gaps in the bridge deck pavement layer, namely the beam and the abutment, and the abutment back and the bridge head slab. The former forms a through seam from top to bottom, which plays a buffering role for the bridge, while the latter cannot form a through seam from top to bottom. In actual operation, when the roadbed settles, the bridge head slab will rise near the bridge end, and the road surface will bulge and crack over time. Rainwater seeps into the ground through the cracks. Due to the influence of water, the settlement of the roadbed will be aggravated, thereby increasing the degree of the disease of the vehicle jumping at the bridge head. The connection between the bridge and the roadbed is a combination of rigidity and flexibility. The impact of high-speed vehicles on the roadbed from the moment they leave the bridge deck is also another factor causing the settlement of the roadbed. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a cantilever bridgehead cladding, eliminating the corbel structure in the conventional design method. The cladding adopts a two-section type, the first section is connected to the bridge abutment foundation to form a cantilever as a whole, and the second section is arranged from directly below the cantilever end of the first section. The first section and the second section are flexibly connected by a conversion system, and the conversion system can realize the conversion of the applied force into potential energy or horizontal kinetic energy, thereby eliminating the influence of the applied force on the cantilever section of the first section causing excessive bending moment, completely eliminating the problem of road cracking caused by the upward warping of the bridgehead cladding near the bridge end, realizing the rigid-flexible transition between the bridge and the roadbed, greatly improving the adverse effects of vehicle jumping, and improving driving safety and comfort.

[0004] A cantilever bridgehead cladding adopts a two-section bridgehead cladding, wherein the first section cladding is connected to the bridge abutment foundation to form an integral cantilever shape, the cladding thickness gradually decreases from the cantilever root to the end, and the lower inner angle of the cladding is designed to be a round chamfer, a bending-resistant steel plate is arranged in the vertical section of the first section cladding, a negative bending moment steel plate is arranged in the cantilever section of the first section cladding, and an expansion joint device is installed between the first section cladding near the bridge end and the beam body; the second section cladding is arranged from directly below the cantilever end of the first section cladding, the first section cladding and the second section cladding are flexibly connected through a conversion system, and the starting end of the second section cladding is connected to a steel roller and extends into the bottom plate of the conversion system; one row of fixed ribbed steel pipes and three rows of retractable hollow steel pipes are arranged in each group along the transverse bridge direction under the top plate of the conversion system, and a total of three groups are arranged.

[0005] Furthermore, the bottoms of the three rows of retractable hollow steel tubes are flush with each other and are set at a height difference with the bottom of the fixed ribbed steel tubes. The top of the steel roller of the secondary plate is set at a distance from the bottom of the fixed ribbed steel tubes. When the far end of the secondary plate sinks, the steel roller starts to move vertically to adapt to the force generated by the settlement until it is tightly attached to the fixed ribbed steel tubes, and the force is converted through potential energy to avoid additional bending moment on the cantilever section. At this time, there is a certain angle between the secondary plate and the first plate. As the far end of the secondary plate continues to sink, the steel roller will compress. The first row of retractable hollow steel tubes slides to the upper right, converting the force through horizontal kinetic energy. The whole process will not generate excessive additional bending moment on the cantilever section of the first section. If the roadbed settlement stops at this time, the steel rollers will be constrained on the left and right by the fixed ribbed steel tubes and the second row of retractable hollow steel tubes to maintain the stability of the secondary section. If the roadbed settlement continues to occur, the steel rollers will continue to move forward to the second row of retractable hollow steel tubes, and the cycle will be repeated to complete the conversion and transmission of the force until the roadbed settlement is completed.

[0006] The present invention has the following obvious advantages:

[0007] Cantilever construction technology has the characteristics of supporting points to bear negative bending moments, the cross-section can be made into variable cross-sections, and materials can be saved. Therefore, it is widely used in the construction of large-span bridges. However, due to its high requirements for the cross-section, it is often limited to box beams and T-beams. The thickness of the bridgehead slab is relatively small, and it is difficult to implement prestressed measures that meet the conditions. The existing technology cannot solve the problem of excessive bending moments caused by external forces when the cantilever slab is in normal use. The cantilever bridgehead slab described in the present invention provides a bridgehead slab conversion system that can convert the force into potential energy or horizontal kinetic energy and then release it, avoiding the phenomenon of excessive bending moments of the cantilever structure due to roadbed settlement, achieving a smooth transition of vehicles from the bridge to the roadbed, and completely solving the problem of cracking of the bridgehead pavement, improving the bridgehead vehicle jumping, and improving driving safety and comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a cross-sectional diagram of the bridgehead deck structure;

[0009] Figure 2 It is a plan view of the secondary section plate;

[0010] Figure 3 It is an enlarged schematic diagram of the conversion subject;

[0011] Figure 4 It is a schematic diagram of the AA section;

[0012] Figure 5 is a schematic cross-sectional view of the front plate;

[0013] Figure markings: 1-abutment, 2-first section plate, 3-second section plate, 4-conversion body, 5-top plate, 6-bottom plate, 7-rear plate, 8-front plate, 9-left side plate, 10-right side plate, 11-reinforced steel plate, 12-angle steel plate, 13-bending steel plate, 14-negative bending moment steel plate, 4-1-fixed bracket, 4-2-pad, 4-3-ribbed steel pipe, 4-4-telescopic bracket, 4-5-bracket, 4-6-hollow steel pipe, 4-7-steel roller, 4-8-rotating shaft, 4-9-chain rod, 4-10-connecting steel plate, h1-height difference between ribbed steel pipe and hollow steel pipe, h2-distance between the top of the steel roller and the bottom of the ribbed steel pipe. DETAILED DESCRIPTION

[0014] In order to enable those skilled in the art to better understand the technical solution of the present invention, a cantilever bridgehead slab provided by the present invention is described in detail below in conjunction with an embodiment. The following embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0015] The cantilever bridgehead slab provided by the present invention adopts a two-stage bridgehead slab. The first-stage slab is connected to the bridge abutment foundation to form a cantilever shape. The slab thickness gradually decreases from the root of the cantilever to the end, and the lower inner angle of the slab is designed to be a round chamfer. A bending-resistant steel plate is arranged in the vertical section of the first-stage slab, a negative bending moment steel plate is arranged in the cantilever section of the first-stage slab, and an expansion joint device is installed between the near-bridge end of the first-stage slab and the beam body; the second-stage slab is arranged from just below the cantilever end of the first-stage slab, and the first-stage slab and the second-stage slab are flexibly connected through a conversion system. The starting end of the second-stage slab is connected to a steel roller and extends into the bottom plate of the conversion system; a row of fixed ribbed steel pipes and three rows of retractable hollow steel pipes are arranged in each group along the horizontal bridge direction of the top plate of the conversion system, and a total of three groups are arranged. The bottoms of the three rows of retractable hollow steel pipes are flush with each other and have a certain height difference with the bottom of the fixed ribbed steel pipes. The top of the steel roller of the second-stage slab is kept at a certain distance from the bottom of the fixed ribbed steel pipes. When the far end of the secondary slab sinks, the steel roller starts to move vertically to adapt to the force generated by the settlement until it is tightly attached to the fixed ribbed steel pipe, converting the force through potential energy to avoid additional bending moment on the cantilever section; at this time, there is a certain angle between the secondary slab and the first slab. As the far end of the secondary slab continues to sink, the steel roller will compress the first row of retractable hollow steel pipes to slide to the upper right, converting the force through horizontal kinetic energy. The whole process will not generate too much additional bending moment on the cantilever section of the first slab. If the roadbed settlement stops at this time, the steel roller will be constrained on the left and right by the fixed ribbed steel pipe and the second row of retractable hollow steel pipes to maintain the stability of the secondary slab; if the roadbed settlement continues to occur, the steel roller will continue to move forward to the second row of retractable hollow steel pipes, and the cycle will be repeated to complete the conversion and transmission of the force until the roadbed settlement is completed. By using the conversion system, the force generated by the roadbed settlement can be released, avoiding the phenomenon of excessive bending moment in the cantilever section of the first slab due to the force, so that the cantilever bridge head slab can function normally during the transition from bridge to roadbed.

[0016] Example 1

[0017] like Figure 1 , Figure 3 and Figure 4 As shown, a cantilever bridge head slab includes: abutment 1, first section slab 2, second section slab 3, conversion body 4, top plate 5, bottom plate 6, back plate 7, front plate 8, left side plate 9, right side plate 10, reinforcing steel plate 11, angle steel plate 12, bending steel plate 13, negative bending moment steel plate 14. The conversion body 4 includes a fixed bracket 4-1, a pad 4-2, a ribbed steel pipe 4-3, a telescopic bracket 4-4, a bracket 4-5, a hollow steel pipe 4-6, a steel roller 4-7, a rotating shaft 4-8, a chain rod 4-9, and a connecting steel plate 4-10. The conversion system is composed of the conversion body 4, top plate 5, bottom plate 6, back plate 7, front plate 8, left side plate 9, right side plate 10, and angle steel plate 12. The first section slab 2, the conversion body 4, and the second section slab 3 are arranged in sequence from top to bottom.

[0018] like Figure 1 , Figure 2 As shown, the first section plate 2 is connected to the abutment 1 as a whole in a cantilever shape, the plate thickness gradually decreases from the cantilever root to the end, and the lower inner angle of the plate is designed to be a round chamfer, a bending steel plate 13 is set in the vertical section of the first section plate 2, and a negative bending moment steel plate 14 is set in the cantilever section of the first section plate 2; the top surface, bottom surface and left and right side surfaces of the starting end of the secondary section plate 3 are all wrapped with connecting steel plates 4-10, and the rotating shaft 4-8 is inserted into the steel roller 4-7 to form a roller that runs the entire length of the horizontal bridge, and is welded to the starting end of the secondary section plate 3 wrapped with the connecting steel plate 4-10 through the chain rods 4-9 on the left and right sides. The starting end of the secondary section plate 3 extends above the bottom plate 6 of the conversion system and is located directly below the cantilever end of the first section plate 2. The first section plate 2 and the secondary section plate 3 are connected through the conversion system.

[0019] like Figure 1 , Figure 3 and Figure 4As shown, the top plate 5, the bottom plate 6, the rear plate 7, the front plate 8, the left plate 9, and the right plate 10 together form a steel cuboid in the transverse direction of the bridge. The top plate 5 is pre-buried in advance when constructing the first section of the plate 2. A row of ribbed steel pipes 4-3 and three rows of hollow steel pipes 4-6 are arranged in each group along the transverse direction of the top plate 5. A total of three groups are arranged in the whole bridge. In order to reduce the counterweight of the cantilever section of the first section of the plate 2, all hollow steel pipes are used, and the transverse direction adopts a non-continuous arrangement with equal spacing. In order to prevent the steel roller 4-7 and the ribbed steel pipe 4-3 from slipping in place when they contact, the ribbed steel pipe 4-3 is specially set to be ribbed. After the ribbed steel pipe 4-3 is welded to the bracket 4-5 and the pad 4-2, it is firmly welded to the top plate 5 through two groups of fixed brackets 4-1. After the hollow steel pipe 4-6 is welded to the bracket 4-5 and the pad 4-2, it is firmly welded to the top plate 5 through two groups of telescopic brackets 4-4. When the steel roller 4-7 moves a certain displacement, in order to enable the ribbed steel pipe 4-3 and the hollow steel pipe 4-6 to have a restraining function on the steel roller 4-7 and facilitate the horizontal movement of the steel roller 4-7, the bottom of the three rows of hollow steel pipes 4-6 are flush and have a certain height difference h1 with the bottom of the ribbed steel pipe 4-3. When the roadbed settles, in order to reduce the force exerted by the steel roller 4-7 on the first section plate 2, a certain distance h2 should be kept between the top of the steel roller 4-7 and the bottom of the ribbed steel pipe 4-3. When the steel roller 4-7 moves vertically to be close to the bottom of the ribbed steel pipe 4-3, the secondary section plate 3 and the first section plate 2 form a certain angle, which is conducive to the conversion of the force into potential energy or horizontal kinetic energy, and is very beneficial to the force of the cantilever structure.

[0020] Furthermore, when the roadbed is in different geological conditions, the range of roadbed settlement can be adapted by increasing or decreasing the number of rows of hollow steel pipes 4-6 or increasing or decreasing the spacing between the bottom of the ribbed steel pipe 4-3 and the top of the steel roller 4-7.

[0021] like Figure 1 , Figure 5 As shown, in order to avoid stress concentration damage at the overlap between the secondary section plate 3 and the front plate 8, reinforcing steel plates 11 should be pre-embedded at the corresponding positions of the top plate and the bottom plate during the construction of the secondary section plate 3, and angle steel plates 12 should be used to reinforce the corners formed by the bottom plate 6 and the front plate 8.

[0022] The present invention is described in detail above in conjunction with the embodiments, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the field without departing from the purpose of the present invention, and should also be regarded as the protection scope of the present invention.

Claims

1. A cantilever bridgehead slab, characterized in that: A two-section bridge head cladding is adopted. The first section is connected to the bridge abutment foundation to form an integral cantilever shape. The plate thickness gradually decreases from the root to the end of the cantilever, and the lower inner angle of the plate is designed to be a rounded chamfer. A bending-resistant steel plate is arranged in the vertical section of the first section, a negative bending moment steel plate is arranged in the cantilever section of the first section, and an expansion joint device is installed between the end of the first section near the bridge and the beam body; the second section is arranged from directly below the cantilever end of the first section, and the first section and the second section are flexibly connected by a conversion system. The starting end of the second section is connected to a steel roller and extends into the bottom plate of the conversion system; one row of fixed ribbed steel pipes and three rows of retractable hollow steel pipes are arranged in each group along the transverse bridge direction under the top plate of the conversion system, with a total of three groups.

2. The cantilever bridgehead slab according to claim 1, characterized in that: The bottoms of the three rows of retractable hollow steel tubes are flush with each other and are set at a height difference with the bottom of the fixed ribbed steel tubes. The top of the steel roller of the secondary plate is set at a distance from the bottom of the fixed ribbed steel tubes. When the far end of the secondary plate sinks, the steel roller starts to move vertically to adapt to the force generated by the settlement until it is tightly attached to the fixed ribbed steel tubes, converting the force through potential energy to avoid additional bending moment on the cantilever section. At this time, there is a certain angle between the secondary plate and the first plate. As the far end of the secondary plate continues to sink, the steel roller will compress the first row of The retractable hollow steel tube slides to the upper right and transforms the force through horizontal kinetic energy. The whole process will not generate excessive additional bending moment on the cantilever section of the first section. If the roadbed settlement stops at this time, the steel roller will be constrained on the left and right by the fixed ribbed steel tube and the second row of retractable hollow steel tubes to maintain the stability of the secondary section. If the roadbed settlement continues to occur, the steel roller will continue to move forward to the second row of retractable hollow steel tubes, and the cycle will be repeated to complete the transformation and transmission of the force until the roadbed settlement is completed.

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