Steel arch bridge vault watertight door and sealing method thereof

Abstract

The invention discloses a steel arch bridge vault watertight door and a sealing method thereof, relates to the technical field of bridge engineering, and aims to solve the problems of large assembly clearance, quick material aging, high operation torque and the like of a traditional sealing structure. The device comprises a watertight door outer cover, a composite rubber pad and a low-torque transmission mechanism. The outer cover of the watertight door adopts a double-curvature design, the curvature error is less than 0.1 mm / m, and the outer cover is matched with the curvature radius of 15-25m of the vault; the composite rubber pad is of an EPDM / CR / FKM three-layer gradient hardness structure (the hardness is 65-75 HA), the thickness is 8.0 + / -0.2 mm, and strain optimization is achieved through vulcanization bonding. The transmission mechanism adopts a gear amplification type hand wheel, the transmission ratio is 1: 2.5, the maximum torque is 8 N.m, and low-torque opening and closing are achieved. The sealing method comprises the steps of double-curved-surface machining, composite pad installation and pressing detection, the pressing force is controlled to range from 0.15 MPa to 0.20 MPa, and the pressure drop rate of a pressure maintaining test is smaller than or equal to 2%. The large-span steel arch bridge maintenance channel has the advantages of being high in curved surface adaptability, good in sealing performance, convenient to maintain, long in service life and the like and is suitable for large-span steel arch bridge maintenance channels.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering technology, specifically to a watertight door for the arch crown of a steel arch bridge and its sealing method. Background Technology

[0002] Currently, there are three major technical defects in the maintenance access channels at the top of steel arch bridges: Sealing failure: There is a 3-8mm assembly gap between the traditional flat cover plate and the curved arch. In the Fenhe River Basin with an annual precipitation of 500mm, the average annual water infiltration rate reaches 17%, which accelerates the corrosion of the internal steel structure. Material aging: Under ultraviolet radiation, the hardness of ordinary nitrile rubber gaskets decreases by ≥30% within 2 years, the compression set exceeds 40%, and the sealing pressure drops from the initial 0.10MPa to 0.03MPa; Inconvenient to operate: The torque of the existing screw mechanism is as high as 25 N·m, and the success rate of single-person operation is less than 60%. Although CN107542409A proposed the concept of curved surface sealing, it did not solve the stress concentration problem at the interface between rubber materials and metal, and lacked a design for the negative pressure condition of the arch. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one objective of this invention is to propose a watertight door for the arch of a steel arch bridge and its sealing method, which solves problems such as sealing failure, material aging, and inconvenient operation through a curved surface adaptive sealing structure, optimized design of composite rubber gaskets, and a low-torque transmission mechanism.

[0004] To solve the above problems, the present invention provides a watertight door for the arch of a steel arch bridge, including an outer cover of the watertight door, an inner cover fixed to the inside of the arch, and a screw connecting the outer cover of the watertight door and a handwheel. The outer cover of the watertight door is equipped with a double-curvature pressure-bearing surface, which seals with the curved surface of the arch, matching the curvature radius of the arch in the range of 15~25m, with a curvature error of less than 0.1mm / m; the edge of the outer cover of the watertight door is equipped with a stepped sealing groove. The stepped sealing groove is embedded with a composite sealing gasket; The inner cover is equipped with a transmission mechanism, which includes a gear transmission box. The input shaft of the gear transmission box is connected to a handwheel, and the output shaft is connected to a screw, which is used to drive the outer cover of the watertight door to open and close. The upper end of the screw is connected to the outer cover of the watertight door via a spherical bearing, and the lower end is connected to the handwheel via a gear transmission box; the inner cover is fixed to the inner side of the arch with bolts, and the bolt preload is controlled at 45 N·m; the clearance of the spherical bearing is 0.05 mm to ensure flexible movement.

[0005] Preferably, the composite sealing gasket has a three-layer composite structure, including a top layer, a middle layer, and a bottom layer; The surface layer is made of EPDM rubber, with a thickness of 1.5 mm and a Shore hardness of 65±2HA; The middle layer is made of neoprene rubber with a thickness of 5.0 mm; The bottom layer is made of fluororubber, with a thickness of 1.5mm and a Shore hardness of 75±2HA; The layers are bonded together by vulcanization, with a total thickness of 8.0±0.2mm, forming a gradient hardness structure to optimize strain distribution and reduce the stress concentration factor to 1.2.

[0006] Preferably, the gearbox is a two-stage gear transmission mechanism with a transmission ratio of 1:2.2 to 1:2.8; The output end of the gear transmission box is equipped with a thrust ball bearing with a rated axial load of not less than 5kN and a radial clearance of not more than 0.05mm. The handwheel is equipped with an 18-tooth ratchet mechanism with a maximum output torque of 8 N·m, which is used to apply clamping force through the screw.

[0007] Preferably, the depth of the stepped sealing groove is 12±0.5mm, the bottom of the groove has a drainage angle of 15°±1°, and the groove wall has a transition radius of R0.5mm to avoid shearing damage to the composite sealing gasket during the compression process.

[0008] Preferably, the outer cover of the watertight door is made of 6061-T6 aluminum alloy, and the double-curvature pressure-bearing surface is CNC machined with a contour tolerance not exceeding IT7 grade. The screw is made of 304 stainless steel with a trapezoidal thread, specification Tr24×5, and the surface is hard chrome plated with a roughness Ra of no more than 0.8μm; The gearbox inside the inner cover is filled with VG32 grease to reduce friction.

[0009] Preferably, the watertight door also includes a sealing test interface, located on the side of the inner cover, for connecting a compressed air source to conduct a pressure test; When closed, the watertight door cover can withstand wind speeds of up to 140 km / h, meeting the QL-150 standard.

[0010] A sealing method for a watertight door on the arch of a steel arch bridge includes the following steps: Step S1: Machine the double curvature sealing surface of the watertight door cover according to the curvature radius of the arch, so that the curvature error is no greater than 0.1mm / m and the profile tolerance does not exceed IT7 grade; Step S2: The composite sealing gasket of EPDM rubber, neoprene rubber and fluororubber is molded at 170±5℃ and glued into the stepped sealing groove of the watertight door cover, and left to stand for 24 hours to cure. Step S3: Use the handwheel to drive the screw to compress the composite gasket, and control the compression force to be 0.15 - 0.20 MPa, so that the watertight outer cover of the door is in sealing fit with the vaulted surface; Among them, the handwheel amplifies the torque through a gear transmission mechanism, and the transmission ratio is 1:2.5. To achieve an outer cover opening height of 150 mm, only 90° rotation of the handwheel is required.

[0011] Preferably, after step S3, a seal detection step is further included; The seal detection adopts the compressed air pressure holding method. Inject 0.18 MPa compressed air into the sealing cavity, hold the pressure for 30 minutes, and the pressure drop rate not exceeding 2% is qualified.

[0012] Preferably, in step S2, before bonding the composite gasket, first apply a 0.2 mm thick silane coupling agent on the installation surface of the vault to enhance the bonding strength; The replacement period of the composite gasket is once every 5 years. When replacing, only the bolts of the inner cover need to be disassembled, and there is no need to damage the vault structure.

[0013] The advantages of a watertight door for the vault of a steel arch bridge and its sealing method according to the present invention compared with the prior art are as follows: 1. The outer cover of the curved surface adaptive sealing structure is cast from 6061T6 aluminum alloy, and a double-curved bearing surface (curvature error ≤ 0.1 mm / m) matching the curvature of the vault is precisely machined on the inner surface. A stepped sealing groove with a depth of 12 mm is provided at the edge, the bottom inclination angle of the groove is 15° to guide the water to flow out, and a 0.5 mm chamfer is provided on the groove wall to avoid shear damage of the rubber gasket.

[0014] 2. The optimized design of the composite rubber gasket adopts a three-layer composite structure: the surface layer is 1.5 mm thick EPDM (ultraviolet resistant), the middle layer is 5.0 mm thick CR (compression resistant), and the bottom layer is 1.5 mm thick fluororubber (resistant to medium penetration). The Shore hardness gradient design of the composite gasket (surface layer 65HA → bottom layer 75HA) optimizes the strain distribution under a compression force of 0.15 MPa, and the stress concentration coefficient is reduced to 1.2.

[0015] 3. The low-torque transmission mechanism: The screw is made of 304 stainless steel trapezoidal thread (Tr24×5), and is matched with a self-lubricating copper nut. The handwheel is provided with an 18-tooth ratchet mechanism, and the maximum output torque is 8 N.m. An innovative torque amplifier is set inside the inner cover, and the transmission ratio is 1:2.5. To achieve an outer cover opening height of 150 mm, only 90° rotation of the handwheel is required. Verified by wind tunnel tests, the airtightness of this device reaches QL-150 level (GB / T7106) at a wind speed of 140 km / h, and the sealing pressure retention rate is ≥ 95% after �00,000 opening and closing cycles. Brief Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a longitudinal sectional view of the watertight door in this invention: showing the curved surface fit between the outer cover of the watertight door and the arch, the screw passing through the arch and connecting to the handwheel, and the inner cover of the watertight door being fixed by welding; Figure 2 This is a diagram of the sealing structure of the present invention: showing the structure of the composite rubber gasket inside the stepped groove; Figure 3 , Figure 4 The transmission mechanism of the present invention is shown in detail: the handwheel applies pressure and thrust to the sealing rubber strip through the screw, thereby controlling the opening and sealing effect of the watertight door.

[0018] In the diagram: 1-Outer cover; 2-Screw; 3-Handwheel; 4-Inner cover; 5-Composite sealing gasket. Detailed Implementation

[0019] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0020] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings.

[0022] A watertight door for the arch of a steel arch bridge includes an outer cover 1, an inner cover 4 fixed to the inside of the arch, and a screw 2 connecting the outer cover and a handwheel 3.

[0023] The outer cover of the watertight door is equipped with a double-curvature pressure-bearing surface, which is sealed and matched with the curved surface of the arch. The radius of curvature of the arch is 15~25m, and the curvature error is less than 0.1mm / m. The edge of the outer cover of the watertight door is equipped with a stepped sealing groove.

[0024] The stepped sealing groove is embedded with a composite sealing gasket 5.

[0025] The inner cover is equipped with a transmission mechanism, which includes a gear transmission box. The input shaft of the gear transmission box is connected to a handwheel, and the output shaft is connected to a screw, which is used to drive the outer cover of the watertight door to open and close.

[0026] The upper end of the screw is connected to the outer cover of the watertight door via a spherical bearing, and the lower end is connected to the handwheel via a gear transmission box; the inner cover is fixed to the inner side of the arch with bolts, and the bolt preload is controlled at 45 N·m; the clearance of the spherical bearing is 0.05 mm to ensure flexible movement.

[0027] Preferably, the composite sealing gasket has a three-layer composite structure, including a top layer, a middle layer, and a bottom layer: The surface layer is made of ethylene propylene diene monomer (EPDM) rubber, with a thickness of 1.5 mm, a Shore hardness of 65±2HA, and excellent UV resistance. The middle layer is made of neoprene rubber (CR) with a thickness of 5.0 mm and has strong compression resistance; The bottom layer is made of fluororubber (FKM), with a thickness of 1.5mm and a Shore hardness of 75±2HA, making it resistant to media penetration. The layers are bonded together by vulcanization, with a total thickness of 8.0±0.2mm, forming a gradient hardness structure to optimize strain distribution and reduce the stress concentration factor to 1.2.

[0028] Preferably, the gear transmission box is a two-stage gear transmission mechanism with a transmission ratio of 1:2.2 to 1:2.8; the output end of the gear transmission box is equipped with a thrust ball bearing with a rated axial load of not less than 5kN and a radial clearance of not more than 0.05mm; the handwheel is equipped with an 18-tooth ratchet mechanism with a maximum output torque of 8N·m, used to apply clamping force through the screw.

[0029] Preferably, the depth of the stepped sealing groove is 12±0.5mm, the bottom of the groove has a drainage angle of 15°±1°, and the groove wall has a transition radius of R0.5mm to avoid shearing damage to the composite sealing gasket during the compression process.

[0030] Preferably, the outer cover of the watertight door is cast from 6061-T6 aluminum alloy, and the double-curvature pressure-bearing surface is CNC machined with a profile tolerance not exceeding IT7 grade; the screw adopts 304 stainless steel trapezoidal thread with a specification of Tr24×5, and the surface is hard chrome plated with a roughness Ra not greater than 0.8μm; the gear transmission box of the inner cover is filled with VG32 grease to reduce friction.

[0031] Preferably, the watertight door also includes a sealing test interface, located on the side of the inner cover, for connecting a compressed air source to conduct a pressure test; when the outer cover of the watertight door is closed, it can withstand the airtightness requirement of a wind speed of 140km / h, reaching the QL-150 standard (according to GB / T7106).

[0032] A sealing method for a watertight door on the arch of a steel arch bridge includes the following steps: 1. Step S1: Machining the outer cover of the watertight door: Machining the double curvature sealing surface of the outer cover of the watertight door according to the curvature radius of the arch, so that the curvature error is no greater than 0.1mm / m and the profile tolerance does not exceed IT7 grade.

[0033] 2. Step S2: Install composite sealing gasket: The composite sealing gasket of EPDM rubber, neoprene rubber and fluororubber is molded at 170±5℃ and glued into the stepped sealing groove of the watertight door cover, and left to stand for 24 hours to cure; before bonding, apply a 0.2mm thick silane coupling agent to the arch mounting surface to enhance the bonding strength.

[0034] 3. Step S3: Pressing and sealing: The composite sealing gasket is pressed by the screw driven by the handwheel. The pressing force is controlled at 0.15~0.20MPa to make the watertight door cover and the arched curved surface seal together. The handwheel amplifies the torque through the gear transmission mechanism with a transmission ratio of 1:2.5, so that the handwheel only needs to be rotated 90° to open the cover to a height of 150mm.

[0035] 4. Step S4: Sealing test: Using the compressed air pressure holding method, inject 0.18MPa compressed air into the sealing cavity and hold the pressure for 30 minutes. The pressure drop rate is not greater than 2% to be considered qualified.

[0036] The composite gasket should be replaced every 5 years. Replacement only requires removing the inner cover bolts and does not require damaging the dome structure.

[0037] To more clearly illustrate the specific embodiments of the present invention, several examples are provided below: Example 1: Installation of watertight door on the arch of the Fenhe River Bridge on Hefen Road 1. Component machining: The outer cover of the watertight door is CNC machined with an arch curvature radius R=18m, and the profile tolerance of the double curvature sealing surface is controlled at IT7 level.

[0038] Composite sealing gasket molding: EPDM, CR and FKM are bonded together after vulcanization at 170°C for 30 minutes.

[0039] The screw surface is hard chrome plated, with a roughness Ra≤0.8μm.

[0040] 2. On-site installation: Clean the arch mounting surface and apply a 0.2mm thick silane coupling agent.

[0041] Embed the composite sealing gasket with adhesive backing into the stepped groove and let it stand for 24 hours to cure.

[0042] The upper end of the screw is connected to the outer cover via a spherical bearing (clearance 0.05mm), the preload of the inner cover bolts is controlled at 45N·m, and the gearbox is injected with VG32 grease.

[0043] 3. Sealing test: After closing the outer cover, inject 0.18MPa compressed air through the seal test interface, maintain the pressure for 30 minutes, and the pressure drop ≤2% is considered qualified.

[0044] Wind tunnel tests have verified that the air tightness reaches QL-150 level at a wind speed of 140km / h.

[0045] Example 2: Maintenance and Replacement The composite gasket should be inspected every 5 years. If the hardness decreases by more than 10% or cracks appear, it should be replaced.

[0046] When replacing, remove the inner cover bolts, take out the old gasket, clean the groove, and then install the new gasket. No welding or cutting of the dome structure is required.

[0047] Finally, any aspects not fully described in this invention utilize existing mature products and technologies.

[0048] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A watertight door for the arch of a steel arch bridge, characterized in that: It includes an outer cover for a watertight door, an inner cover fixed to the inside of the arch, and a screw connecting the outer cover for the watertight door to the handwheel; The outer cover of the watertight door is provided with a double-curvature pressure-bearing surface, which is sealed and matched with the curved surface of the arch, matching the curvature radius of the arch in the range of 15~25m, with a curvature error of less than 0.1mm / m; the edge of the outer cover of the watertight door is provided with a stepped sealing groove. The stepped sealing groove is embedded with a composite sealing gasket. The inner cover is equipped with a transmission mechanism, which includes a gear transmission box. The input shaft of the gear transmission box is connected to a handwheel, and the output shaft is connected to the screw, which is used to drive the outer cover of the watertight door to open and close. The upper end of the screw is connected to the outer cover of the watertight door via a spherical bearing, and the lower end is connected to the handwheel via the gear transmission box; the inner cover is fixed to the inner side of the arch with bolts, and the bolt preload is controlled at 45 N·m; the clearance of the spherical bearing is 0.05 mm to ensure flexible movement.

2. The watertight door for the arch of a steel arch bridge according to claim 1, characterized in that: The composite sealing gasket has a three-layer composite structure, including a top layer, a middle layer, and a bottom layer; The surface layer is made of EPDM rubber with a thickness of 1.5 mm and a Shore hardness of 65±2HA. The intermediate layer is made of neoprene rubber with a thickness of 5.0 mm; The bottom layer is made of fluororubber, with a thickness of 1.5 mm and a Shore hardness of 75±2HA; The layers are bonded together by vulcanization, with a total thickness of 8.0±0.2mm, forming a gradient hardness structure to optimize strain distribution and reduce the stress concentration factor to 1.

2.

3. The watertight door for the arch of a steel arch bridge according to claim 1, characterized in that: The gearbox is a two-stage gear transmission mechanism with a transmission ratio of 1:2.2 to 1:2.

8. The output end of the gear transmission box is equipped with a thrust ball bearing with a rated axial load of not less than 5kN and a radial clearance of not more than 0.05mm. The handwheel is equipped with an 18-tooth ratchet mechanism with a maximum output torque of 8 N·m, which is used to apply clamping force through the screw.

4. The watertight door for the arch of a steel arch bridge according to claim 1, characterized in that: The stepped sealing groove has a depth of 12±0.5mm, a drainage angle of 15°±1° at the bottom, and a transition radius of R0.5mm on the groove wall to prevent shearing damage to the composite sealing gasket during the compression process.

5. A watertight door for the arch of a steel arch bridge according to claim 1, characterized in that: The outer cover of the watertight door is cast from 6061-T6 aluminum alloy, and the double-curvature pressure-bearing surface is CNC machined with a contour tolerance not exceeding IT7 grade. The screw is made of 304 stainless steel with a trapezoidal thread, specification Tr24×5, and the surface is hard chrome plated with a roughness Ra of no more than 0.8μm; The gearbox inside the inner cover is filled with VG32 grease to reduce friction.

6. A watertight door for the arch of a steel arch bridge according to claim 1, characterized in that: The watertight door also includes a sealing test interface, located on the side of the inner cover, for connecting a compressed air source to perform a pressure test; When closed, the watertight door cover can withstand wind speeds of up to 140 km / h, meeting the QL-150 standard.

7. A sealing method for a watertight door at the crown of a steel arch bridge as described in claim 1, characterized in that, Includes the following steps: Step S1: Machine the double curvature sealing surface of the watertight door cover according to the curvature radius of the arch, so that the curvature error is no greater than 0.1mm / m and the profile tolerance does not exceed IT7 grade; Step S2: The composite sealing gasket of EPDM rubber, neoprene rubber and fluororubber is molded at 170±5℃ and glued into the stepped sealing groove of the watertight door cover, and left to stand for 24 hours to cure. Step S3: Drive the screw by the handwheel to compress the composite gasket, and control the compression force to be 0.15 - 0.20 MPa, so that the outer cover of the watertight door is in sealing fit with the vaulted surface; Among them, the handwheel amplifies the torque through a gear transmission mechanism, and the transmission ratio is 1:2.5, so that only a 90° rotation of the handwheel is required for the opening height of the outer cover to be 150 mm.

8. A sealing method for a watertight door at the crown of a steel arch bridge according to claim 7, characterized in that: After step S3, a seal detection step is further included; The seal detection adopts the compressed air pressure holding method. Inject 0.18 MPa of compressed air into the seal cavity, hold the pressure for 30 minutes, and the pressure drop rate not exceeding 2% is qualified.

9. A sealing method for a watertight door at the crown of a steel arch bridge according to claim 7, characterized in that: In step S2, before bonding the composite gasket, first apply a 0.2 mm thick silane coupling agent on the vault installation surface to enhance the bonding strength; The replacement period of the composite gasket is once every 5 years. When replacing, only the inner cover bolts need to be disassembled, and the vault structure does not need to be damaged.

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