Cold and hot combined reinforcement method for distortion fatigue details of steel bridge

Abstract

The present application relates to a kind of cold, hot combination reinforcing method of steel bridge distortion fatigue detail, and main component of steel bridge is connected by weld mode, and the longer distortion fatigue crack of detail of operating steel bridge is generated due to distortion behavior of bridge thin-walled structure, if must be repaired, crack is eliminated, should use cold, hot combination reinforcing method to reinforce.Adopting the method to reinforce, first, the fatigue crack is repaired using heat maintenance method, then carbon fiber reinforced resin matrix composite, multi-limb angle steel, carbon fiber reinforced resin matrix composite are pasted in the place to be reinforced in turn, form carbon fiber cloth-angle steel composite reinforcing structure, before the strength of adhesive layer is not consolidated, need to be fixed using auxiliary device, this reinforcing mode is suitable for the reinforcement of fatigue crack above 100mm, can effectively constrain distortion at steel bridge fatigue detail, improve the ability of detail to retard distortion fatigue crack initiation and propagation, with the advantages of convenient construction, low cost, excellent performance etc.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering technology, specifically relating to a cold and hot combined reinforcement method for the distortion fatigue details of steel bridges. Background Technology

[0002] The details at the lower end of the U-rib web of the weld connecting the transverse diaphragm and U-rib of the steel bridge deck, the details at the weld connecting the top plate and U-rib, and the details in the gaps between the steel bridge webs are typical distortion fatigue details. Under the combined effects of residual welding tensile stress and vehicle and temperature stress, distortion fatigue cracking is prone to occur. Long distortion fatigue cracks can significantly reduce the structural stiffness and ultimate bearing capacity. Under large service loads, crack instability and propagation may be induced, leading to bridge collapse and seriously endangering the safety of vehicles and pedestrians. Therefore, it is essential to properly repair severely affected areas of distortion fatigue cracking. Traditional crack remelting reinforcement methods can repair cracked areas and eliminate cracks, but this hot reinforcement method introduces new residual welding stress and welding defects, making secondary fatigue cracking likely after hot reinforcement. Therefore, there is an urgent need to develop an efficient reinforcement method that can both repair existing fatigue cracks in details and reduce in-plane fatigue stress in details, effectively suppressing secondary fatigue cracking in details after reinforcement. Summary of the Invention

[0003] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and develop a method for cold and hot combined reinforcement of steel bridges with reliable stress and convenient construction.

[0004] The technical solution adopted to solve the above-mentioned technical problems is: a cold and hot combined reinforcement method for the distortion fatigue details of steel bridges, including the following steps:

[0005] S1. For cracks in distortion fatigue details with a length exceeding 100mm, use methods such as remelting and welding for heat maintenance to eliminate the original cracks. The preheating range must extend 100mm beyond the crack tip. Among them, distortion fatigue details include details at the lower end of the U-rib web of the weld connecting the transverse diaphragm and U-rib of the steel bridge deck, details at the weld connecting the top plate and U-rib, and details of the gap between the steel bridge web.

[0006] S2. After the temperature drops to ambient temperature, grind off the excess weld height, clean and roughen the bonding surface of the carbon fiber reinforced resin matrix composite material of the base material in the distortion fatigue details, and grind and sandblast the surface of the angle steel.

[0007] S3. After treating the base material and the surface of the reinforced angle steel, apply epoxy resin primer with a thickness of 0.3 to 0.5 mm evenly to the bonding surface of the base material to be reinforced. Then, attach the first layer of carbon fiber cloth. Use a debubbling roller to roll the carbon fiber cloth several times along the fiber direction to ensure that the carbon fiber cloth is fully impregnated with epoxy resin, ensuring that the carbon fiber cloth is completely bonded to the base material and does not lift up.

[0008] S4. After the surface of the first layer of carbon fiber cloth is touch dry, apply 0.3-0.5mm of epoxy resin adhesive evenly to the surface of the first layer of carbon fiber cloth and roll it multiple times along the fiber direction with a debubbling roller. Near the weld, press the debubbling roller firmly multiple times. Then attach the second layer of carbon fiber cloth and repeat several times until the predetermined number of carbon fiber cloth layers is reached to form a carbon fiber reinforced resin matrix composite material.

[0009] S5. When the surface of the carbon fiber reinforced resin matrix composite material loses its fluidity but still has strong adhesion, apply an epoxy resin adhesive layer of 1.0 to 1.5 mm thickness to a predetermined position on the carbon fiber reinforced resin matrix composite material, and then attach the angle steel to the carbon fiber reinforced resin matrix composite material. If there are gaps between the carbon fiber reinforced resin matrix composite material and the angle steel, a small amount of epoxy resin adhesive can be used to fill them.

[0010] S6. Attach several sets of auxiliary reinforcement devices 10-20mm away from the edge of the angle steel. Fix the base to the surface of the base material with modified acrylic adhesive and install a limiting device on the lower base. Then, insert the strip into the base, raise the strip with shims, and ensure that the bottom surface of the strip is flush with the upper surface of the angle steel. Tighten the nut to fix it.

[0011] S7. After the bottom carbon fiber reinforced resin matrix composite material is completely bonded to the angle steel and has formed strength, remove the auxiliary reinforcement device and remove the adhesive left by the auxiliary reinforcement device. Then repeat steps S3 to S4 on the angle steel and carbon fiber reinforced resin matrix composite material to bond the carbon fiber reinforced resin matrix composite material to form a composite layer of combined reinforcement structure to bear the force together.

[0012] In step S7 of the present invention, the combined reinforcement structure is composed of carbon fiber cloth, angle steel, and carbon fiber cloth.

[0013] The carbon fiber reinforced resin matrix composite material of the present invention is formed by coating several layers of carbon fiber cloth with epoxy resin adhesive and bonding them together.

[0014] In step S4 of the present invention, the carbon fiber reinforced resin matrix composite base layer is formed by bonding 4 to 6 layers of carbon fiber cloth with epoxy resin adhesive, and each layer of carbon fiber cloth is bonded alternately by orthogonal or oblique bonding.

[0015] The carbon fiber cloth bonding area of ​​the present invention extends 100-200mm beyond the perimeter of the angle steel, and the edge of the angle steel extends 50-150mm beyond the crack tip at the distortion fatigue detail.

[0016] The angle steel of the present invention has a leg width of not less than 120mm, a leg length of not less than 200mm, and a leg thickness of 10-14mm; the angle steel is made by cold rolling or by processing through-welded steel plate.

[0017] The auxiliary reinforcement device of the present invention is as follows: a bolt rod assembly is provided on the surface of the base, through holes are provided at both ends of the strip, the strip is sleeved on the bolt rod assembly, and a limit device is provided between one of the bases and the strip.

[0018] The angle steel of the present invention is one of unequal-sided double-limb angle steel, equilateral double-limb angle steel, and triple-limb angle steel.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. This invention combines thermal maintenance methods such as crack remelting with composite reinforcement methods of carbon fiber cloth and multi-limb angle steel. It not only fuses and repairs the fatigue cracks of the original steel bridge, but also improves the local stiffness of the structure and reduces the fatigue stress in the details by adopting cold reinforcement measures. This avoids the problem of secondary fatigue cracking after single thermal reinforcement, and also avoids the leakage and corrosion problems in the crack area when cold reinforcement is used alone.

[0021] 2. This invention utilizes epoxy resin adhesive to bond and fix the combination structure of carbon fiber reinforced resin matrix composite material and angle steel in the fatigue cracking remelting zone of steel bridge, thereby leveraging the flexible reinforcement characteristics of carbon fiber cloth and the relatively rigid reinforcement characteristics of steel plate to achieve a reinforcement effect that combines rigidity and flexibility.

[0022] 3. This invention uses a composite structure of carbon fiber reinforced resin matrix composite material and steel plate for reinforcement. The carbon fiber reinforced resin matrix composite material is composed of several layers of carbon fiber cloth coated with epoxy resin adhesive and bonded together. This can give full play to the good bonding and tensile properties of carbon fiber cloth and reduce fatigue stress in the details. The steel plate bonded to the surface of the carbon fiber reinforced resin matrix composite material can further improve the structural stiffness of the reinforced area, significantly reduce fatigue stress in the details, and achieve the technical purpose of effectively inhibiting the initiation and propagation of fatigue cracks in the details.

[0023] 4. The present invention employs an auxiliary reinforcement device that combines slats, a limiting device, and a bolted base. This device can provide reliable temporary fixation before the adhesive layer between the multi-limb angle steel and the carbon fiber reinforced resin matrix composite material has fully solidified and formed strength. The modified acrylic adhesive is used to fix the bolted base to the steel structure surface, which is convenient for installation and removal and does not damage the original structure.

[0024] In summary, the reinforcement structure of the present invention has the technical characteristics of excellent repair effect, good durability, lightweight construction, simple construction and low cost. It is suitable for the reinforcement of cracks in distortion fatigue details with a length of more than 100mm, and can be extended to the repair and reinforcement of fatigue cracks caused by distortion in steel bridges. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the steel bridge deck reinforcement structure of the present invention.

[0026] Figure 2 This invention relates to a heat-strengthening method for four cracks in the weld connecting the diaphragm and the U-rib.

[0027] Figure 3 This invention demonstrates the heat-strengthening effect on the four cracks at the weld joint connecting the diaphragm and the U-rib.

[0028] Figure 4 yes Figure 1 A three-dimensional structural diagram showing the temporary fixation at four weld joints connecting the central transverse diaphragm and the U-rib.

[0029] Figure 5 This is a three-dimensional structural schematic diagram of the unequal-sided double-limb angle steel 7.

[0030] Figure 6 This is a schematic diagram of the auxiliary reinforcement device 10 of the present invention.

[0031] Figure 7 yes Figure 1 A partial three-dimensional structural diagram of four weld joints connecting the central transverse diaphragm and the U-rib.

[0032] Figure 8 This invention relates to a method for heat-strengthening cracks at the weld seam 1 connecting the top plate and the U-rib.

[0033] Figure 9 This invention demonstrates the heat-strengthening effect of the weld seam 1 connecting the top plate and the U-rib.

[0034] Figure 10 yes Figure 1 A three-dimensional structural diagram of the temporary fixation at the weld seam 1 connecting the top plate and the U-rib.

[0035] Figure 11 This is a three-dimensional structural schematic diagram of an equilateral double-limb angle steel 8.

[0036] Figure 12 yes Figure 1 A partial three-dimensional structural diagram of the weld seam 1 connecting the top plate and the U-rib.

[0037] Figure 13 This invention relates to a method for thermally reinforcing cracks at the gaps between stiffening ribs and webs.

[0038] Figure 14 This invention demonstrates the effect of heat reinforcement of cracks at the gaps between the stiffening ribs and webs.

[0039] Figure 15 This is a schematic diagram of the three-dimensional structure for temporary fixing of the vertical stiffening rib gaps of the present invention.

[0040] Figure 16 This is a three-dimensional structural schematic diagram of the three-limb angle steel 12.

[0041] Figure 17This is a schematic diagram of a local three-dimensional structure at the gap between the web plates of the vertical stiffening ribs.

[0042] Figure 18 This is a schematic diagram of the structure of the carbon fiber reinforced resin matrix composite material 9 of the present invention.

[0043] In the diagram: 1. Weld connecting the top plate and the U-rib; 2. Top plate of the steel bridge deck; 3. U-rib; 4. Weld connecting the transverse diaphragm and the U-rib; 5. Transverse diaphragm; 6. Hole in the transverse diaphragm; 7. Unequal-sided double-limb angle steel; 8. Equal-sided double-limb angle steel; 9. Carbon fiber reinforced resin matrix composite material; 10. Auxiliary reinforcement device; 11. Upper flange plate; 12. Three-limb angle steel; 13. Vertical stiffening rib; 14. Web of the steel plate girder; 15. Horizontal node plate; 16. Lower flange plate; 9-1. Carbon fiber cloth; 9-2. Epoxy resin adhesive; 10-1. Base; 10-2. Strip; 10-3. Limiting device. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to these embodiments.

[0045] Example 1

[0046] This example illustrates a cold and hot combined reinforcement method for addressing distortion fatigue details at the lower end of the U-rib web of the weld connecting the diaphragm and the U-rib. Figures 1-7 In the steel bridge deck, the bottom of the top plate 2 is provided with several sets of U-ribs 3. The top plate 2 and the U-ribs are welded together to form a weld 1 connecting the top plate and the U-ribs. A transverse diaphragm 5 is provided between adjacent U-ribs. The transverse diaphragm 5 is welded to the U-ribs to form a weld 4 connecting the transverse diaphragm and the U-ribs. The transverse diaphragm 5 has a weld hole on the side near the weld 1 connecting the top plate and the U-ribs and a hole 6 on the side near the bottom of the U-ribs. This embodiment mainly focuses on reinforcing the cracks that appear in the details of the web of the U-rib at the lower end of the weld 4 connecting the transverse diaphragm and the U-ribs, that is, cracks appear at the weld 4 connecting the transverse diaphragm and the U-ribs and the hole 6. The specific method includes the following steps:

[0047] S1. Remelt and heat-maintain the details of the U-rib web at the lower end of the weld connecting the diaphragm and the U-rib to eliminate the original cracks. The preheating range exceeds the crack tip by 100mm. The heat strengthening methods include, but are not limited to, welding, remelting, and hot cutting.

[0048] S2. After the temperature at the lower end of the U-rib web of the weld connecting the diaphragm and the U-rib has dropped to ambient temperature, grind off the excess weld height. Then, clean and roughen the bonding surfaces of the base material and carbon fiber reinforced resin composite material 9 at the lower end of the U-rib web of the weld connecting the diaphragm and the U-rib. The angle steel surface needs to be ground and sandblasted. Figure 18As shown, the carbon fiber reinforced resin matrix composite material 9 in this embodiment is formed by impregnating and bonding several layers of carbon fiber cloth 9-1 with epoxy resin adhesive 9-2. Unequal-sided double-limb angle steel 7 is bonded to the surface of the carbon fiber reinforced resin matrix composite material 9 to improve the distortion resistance of the transverse diaphragm U-rib, thereby effectively improving the stress performance of typical details and effectively suppressing the initiation and propagation of distortion fatigue cracks at the location of the transverse diaphragm U-rib.

[0049] S3. Apply epoxy resin primer with a thickness of 0.3 to 0.5 mm evenly to the bonding surface of the area to be reinforced. In this embodiment, the thickness of the primer layer is controlled to be 0.4 mm. Then, bond the first layer of carbon fiber cloth 9-1 and use a debubbling roller to roll the carbon fiber cloth 9-1 along the fiber direction several times until the carbon fiber cloth 9-1 is fully impregnated with epoxy resin and the carbon fiber cloth 9-1 is tightly attached to the surface of the base material without obvious lifting.

[0050] S4. After the surface of the first layer of carbon fiber cloth 9-1 is touch dry, apply 0.3-0.5mm of epoxy resin adhesive 9-2 evenly to the surface of the first layer of carbon fiber cloth 9-1 and roll it 2-3 times along the fiber direction with a debubbling roller to bond the second layer of carbon fiber cloth 9-1. Repeat this process several times until the predetermined number of bonding layers of 5 is reached to form a carbon fiber reinforced resin matrix composite material 9. In this embodiment, the thickness of the adhesive layer between each carbon fiber cloth 9-1 is 0.5mm.

[0051] S5. Apply a 1.0–1.5 mm thick epoxy resin layer to the predetermined position on the carbon fiber reinforced resin matrix composite material 9. When the adhesive layer has essentially lost its fluidity but still maintains strong adhesion, attach the unequal-sided double-limb angle steel 7 to the carbon fiber reinforced resin matrix composite material 9. The carbon fiber cloth 9-1 should extend 100–200 mm beyond the perimeter of the angle steel. Each limb of the unequal-sided double-limb angle steel 7 should be at least 120 mm wide, at least 200 mm long, and 10–14 mm thick; it should be cold-rolled or processed from welded steel plates. The edge should extend 50–150 mm beyond the crack tip at the lower end of the U-rib web where the diaphragm and U-rib connect to the weld.

[0052] S6. Several sets of auxiliary reinforcement devices 10 are attached 10-20mm away from the edge of the unequal-sided double-limb angle steel 7. In this embodiment, the auxiliary reinforcement device 10 is composed of a base 10-1, a strip 10-2, a limiting device 10-3, and a bolt rod assembly. The auxiliary reinforcement device 10 has two sets of bases 10-1, each with a size of 35×40mm. An M10 bolt rod assembly is welded to the center of the base. The strip 10-2 is 300mm long and has through holes at both ends with a length of 30mm. The bolt rod assembly is placed in the through holes and tightened with nuts. In practice, a limiting device 10-3 is provided between the lower base 10-1 and the strip 10-2. The limiting device 10-3 is a steel strip with a hole at one end. When in use, the steel strip is screwed onto the surface of the unequal-sided double-limb angle steel 7 to be reinforced, and the nuts of the bolt rod assembly are tightened to complete the temporary auxiliary reinforcement.

[0053] S7. After the bottom carbon fiber reinforced resin matrix composite material 9 and the unequal-sided double-limb angle steel 7 have reached sufficient strength, the auxiliary reinforcement device 10 is removed. Then, steps S3 to S4 are repeated on the angle steel and the carbon fiber reinforced resin matrix composite material 9 to bond the carbon fiber reinforced resin matrix composite material 9 together to form a composite layer of combined reinforcement structure to bear the load. That is, the combined reinforcement structure consists of carbon fiber cloth 9-1, unequal-sided double-limb angle steel 7, and carbon fiber cloth 9-1. In this embodiment, the base layer of carbon fiber reinforced resin matrix composite material 9 is formed by bonding 4 to 6 layers of carbon fiber cloth 9-1 with epoxy resin adhesive 9-2. The arrangement of each layer of carbon fiber can be orthogonal or obliquely alternating.

[0054] Example 2

[0055] exist Figures 8-12 This embodiment describes a cold and hot combined reinforcement method for the distortion fatigue details of a steel bridge. It primarily targets the reinforcement of cracks appearing at the weld detail connecting the top plate and the U-rib of the steel bridge deck. Specifically, cracks appear at weld 1 connecting the top plate and the U-rib; the remaining structure is identical to that of Embodiment 1. The specific method includes the following steps:

[0056] S1. Remelt and heat-maintain the weld 1 connecting the top plate and the U-rib to eliminate the original crack. The preheating range exceeds 100mm from the crack tip. The heat strengthening methods include, but are not limited to, welding, remelting, and thermal cutting.

[0057] S2. After the weld seam 1 connecting the top plate and the U-rib cools to ambient temperature, grind off the excess weld seam. Then, clean and roughen the bonding surfaces of the base material and carbon fiber reinforced resin composite material 9 at the weld seam 1 connecting the top plate and the U-rib. The angle steel surface needs to be ground and sandblasted. Figure 18As shown, the carbon fiber reinforced resin matrix composite material 9 in this embodiment is formed by impregnating and bonding several layers of carbon fiber cloth 9-1 with epoxy resin adhesive 9-2. The carbon fiber reinforced resin matrix composite material 9 has good bonding and tensile properties, which can reduce the stress at the crack tip. The equilateral double-limb angle steel 8 bonded to the surface of the carbon fiber reinforced resin matrix composite material 9 improves the distortion resistance of the top plate U-rib, thereby effectively improving the stress performance of typical details and effectively inhibiting the initiation and propagation of distortion fatigue cracks.

[0058] S3. Apply epoxy resin primer with a thickness of 0.3 to 0.5 mm evenly to the surface to be reinforced after treatment. In this embodiment, the adhesive layer thickness is 0.5 mm. Adhere the first layer of carbon fiber cloth 9-1, and use a debubbling roller to roll the carbon fiber cloth 9-1 several times along the fiber direction until the carbon fiber cloth 9-1 is fully impregnated with epoxy resin and the carbon fiber cloth 9-1 is tightly attached to the surface of the base material without obvious lifting.

[0059] S4. After the surface of the first layer of carbon fiber cloth 9-1 is touch dry, apply 0.3-0.5mm of epoxy resin adhesive 9-2 evenly to the surface of the first layer of carbon fiber cloth 9-1 and roll it 2-3 times along the fiber direction with a debubbling roller. Then, attach the second layer of carbon fiber cloth 9-1. Repeat this process several times until the predetermined thickness is reached to form a carbon fiber reinforced resin matrix composite material 9. In this embodiment, the adhesive layer thickness between each carbon fiber cloth 9-1 is 0.5mm.

[0060] S5. Apply a 1.0-1.5mm thick epoxy resin layer to a predetermined position on the carbon fiber reinforced resin matrix composite material 9, and then attach the equilateral double-leg angle steel 8 to the carbon fiber reinforced resin matrix composite material 9. The area of ​​the carbon fiber cloth 9-1 should extend 100-200mm beyond the perimeter of the double-leg equilateral angle steel 8. Each leg of the double-leg equilateral angle steel 8 should be at least 120mm wide, at least 200mm long, and 10-14mm thick; it should be cold-rolled or processed from welded steel plate. The edge should extend 50-150mm beyond the crack tip at the weld 1 connecting the top plate and the U-rib.

[0061] S6. Several sets of auxiliary reinforcement devices 10 are attached 10-20mm away from the edge of the double-limb equilateral angle steel 8. In this embodiment, the auxiliary reinforcement device 10 is composed of a base 10-1, a strip 10-2, a limiting device 10-3, and a bolt rod assembly. The auxiliary reinforcement device 10 has two sets of bases 10-1, each with a size of 35×40mm. An M10 bolt rod assembly is welded to the center of the base. The strip 10-2 is 300mm long and has through holes at both ends with a length of 30mm. The bolt rod assembly is placed in the through holes and tightened with a nut. In practice, a limiting device 10-3 is provided between the lower base 10-1 and the strip 10-2. The limiting device 10-3 is a steel strip with a hole at one end. When in use, the steel strip is screwed onto the surface of the double-limb equilateral angle steel 8 to be reinforced, and the nut of the bolt rod assembly is tightened to complete the temporary auxiliary reinforcement.

[0062] S7. After the bottom carbon fiber reinforced resin matrix composite material 9 and the double-limb equilateral angle steel 8 have reached sufficient strength, remove the auxiliary reinforcement device 10. Then, repeat steps S3 to S4 on the angle steel and the carbon fiber reinforced resin matrix composite material 9 to bond the carbon fiber reinforced resin matrix composite material 9 together to form a composite layer of combined reinforcement structure to bear the load. That is, the combined reinforcement structure consists of carbon fiber cloth 9-1, double-limb equilateral angle steel 8, and carbon fiber cloth 9-1. In this embodiment, the base layer of carbon fiber reinforced resin matrix composite material 9 is formed by bonding 4 to 6 layers of carbon fiber cloth 9-1 with epoxy resin adhesive 9-2. The arrangement of each layer of carbon fiber can be orthogonal or oblique bonding.

[0063] Example 3

[0064] exist Figures 13-17 This embodiment relates to a cold and hot combined reinforcement method for steel bridge distortion fatigue details. Vertical stiffeners 13 are provided between the upper flange plate 11 and the lower flange plate 16, perpendicular to the web 14 of the steel plate girder. Horizontal node plates 15 pass through the vertical stiffeners 13 and are perpendicular to the web 14 of the steel plate girder. This embodiment mainly targets the reinforcement of cracks appearing at out-of-plane deformation details of the steel beam web, specifically cracks appearing at the welds between the vertical stiffeners 13 and the upper flange plate 11 and the web 14 of the steel plate girder. The specific method includes the following steps:

[0065] S1. Remelt and heat-maintain the weld cracks of the vertical stiffening ribs 13, the upper flange plate 11, and the web plate 14 of the steel plate beam to eliminate the original cracks. The preheating range exceeds 100mm from the crack tip. The heat strengthening methods include, but are not limited to, welding, remelting, and hot cutting.

[0066] S2. After the weld joints of the vertical stiffening ribs 13, the upper flange plate 11, and the web plate 14 of the steel plate beam have cooled to ambient temperature, and the excess weld height has been ground off, the bonding surfaces of the base material and the carbon fiber reinforced resin composite material 9 at the weld joints of the vertical stiffening ribs 13, the upper flange plate 11, and the web plate 14 of the steel plate beam are cleaned and roughened. The angle steel surface needs to be ground and sandblasted. Figure 18 As shown, the carbon fiber reinforced resin matrix composite material 9 in this embodiment is formed by impregnating and bonding several layers of carbon fiber cloth 9-1 with epoxy resin adhesive 9-2. The carbon fiber reinforced resin matrix composite material 9 has good bonding and tensile properties, which can reduce the stress at the crack tip. The three-limb angle steel 12 is bonded to the surface of the carbon fiber reinforced resin matrix composite material 9 to improve the stiffness of the gap between the horizontal node plate 13 and the web plate of the steel plate beam 14, thereby effectively improving the stress performance of the web gap and effectively inhibiting the initiation and propagation of distortion fatigue cracks. Compared with the method of reinforcing by bonding carbon fiber cloth alone or by bonding angle steel alone, the composite structure of carbon fiber reinforced resin matrix composite material 9 and three-limb angle steel 12 has the characteristics of good durability and good resistance to distortion fatigue.

[0067] S3. Apply epoxy resin primer with a thickness of 0.3 to 0.5 mm evenly to the surface of the area to be reinforced after treatment. In this embodiment, the adhesive layer thickness is 0.5 mm. Adhere the first layer of carbon fiber cloth 9-1, and use a debubbling roller to roll the carbon fiber cloth 9-1 several times along the fiber direction to fully impregnate the epoxy resin adhesive with the carbon fiber cloth 9-1.

[0068] S4. After the surface of the first layer of carbon fiber cloth 9-1 is touch dry, apply 0.3-0.5mm of epoxy resin adhesive 9-2 evenly to the surface of the first layer of carbon fiber cloth 9-1 and roll it 2-3 times along the fiber direction with a debubbling roller. Then, attach the second layer of carbon fiber cloth 9-1. Repeat this process several times until the predetermined thickness is reached to form a carbon fiber reinforced resin matrix composite material 9. In this embodiment, the adhesive layer thickness between each carbon fiber cloth 9-1 is 0.5mm.

[0069] S5. Apply a 1.0-1.5 mm thick epoxy resin adhesive layer to a predetermined position on the carbon fiber reinforced resin matrix composite material 9, and then attach the three-limb angle steel 12 to the carbon fiber reinforced resin matrix composite material 9; the area of ​​the carbon fiber cloth 9-1 attached extends 100-200 mm beyond the perimeter of the three-limb angle steel 12. Each limb of the three-limb angle steel 12 has a width of not less than 120 mm, a length of not less than 200 mm, and a thickness of 10-14 mm; it is made by cold rolling or by processing through-welding steel plate. Furthermore, the edge extends 50-150 mm beyond the crack tip at the weld between the vertical stiffening rib 13 and the upper flange plate 11 and the web plate of the steel beam 14.

[0070] S6. Several sets of auxiliary reinforcement devices 10 are attached at a distance of 10-20mm from the edge of the three-limb angle steel 12. In this embodiment, the auxiliary reinforcement device 10 is composed of a base 10-1, a strip 10-2, a limiting device 10-3, and a bolt rod assembly. The auxiliary reinforcement device 10 has two sets of bases 10-1, each with a size of 35×40mm. An M10 bolt rod assembly is welded to the center of the base. The strip 10-2 is 300mm long and has through holes at both ends, each 30mm long. The bolt rod assembly is placed in the through holes and tightened with nuts. In practice, a limiting device 10-3 is provided between the lower base 10-1 and the strip 10-2. The limiting device 10-3 is a steel strip with a hole at one end. When in use, the steel strip is screwed onto the surface of the three-limb angle steel 12 to be reinforced, and the nuts of the bolt rod assembly are tightened to complete the temporary auxiliary reinforcement.

[0071] S7. After the bottom carbon fiber reinforced resin matrix composite material 9 and the three-limb angle steel 12 have reached sufficient strength, remove the auxiliary reinforcement device 10. Then, repeat steps S3 to S4 on the angle steel and the carbon fiber reinforced resin matrix composite material 9 to bond the carbon fiber reinforced resin matrix composite material 9 together to form a composite layer of combined reinforcement structure to bear the load. That is, the combined reinforcement structure consists of carbon fiber cloth 9-1, three-limb angle steel 12, and carbon fiber cloth 9-1. In this embodiment, the base layer of carbon fiber reinforced resin matrix composite material 9 is formed by bonding 4 to 6 layers of carbon fiber cloth 9-1 with epoxy resin adhesive 9-2. The arrangement of each layer of carbon fiber can be orthogonal or oblique bonding.

Claims

1. A method for cold and hot combined reinforcement of distortion fatigue details in steel bridges, characterized in that... Includes the following steps: S1. For cracks in distortion fatigue details with a length exceeding 100mm, use methods such as remelting and welding for heat maintenance to eliminate the original cracks. The preheating range must extend 100mm beyond the crack tip. Among them, distortion fatigue details include details at the lower end of the U-rib web of the weld connecting the transverse diaphragm and U-rib of the steel bridge deck, details at the weld connecting the top plate and U-rib, and details of the gap between the steel bridge web. S2. After the temperature drops to ambient temperature, grind off the excess weld height and clean and roughen the bonding surface of the carbon fiber reinforced resin matrix composite material (9) of the parent material at the distortion fatigue detail. Grind and sandblast the surface of the angle steel. S3. After treating the base material and the surface of the reinforced angle steel, apply epoxy resin primer with a thickness of 0.3 to 0.5 mm evenly to the bonding surface of the base material to be reinforced. Then, attach the first layer of carbon fiber cloth (9-1). Use a debubbling roller to roll the carbon fiber cloth (9-1) several times along the fiber direction to ensure that the carbon fiber cloth (9-1) is fully impregnated with epoxy resin, ensuring that the carbon fiber cloth (9-1) is completely bonded to the base material and does not lift up. S4. After the surface of the first layer of carbon fiber cloth (9-1) is touch dry, apply 0.3-0.5mm of epoxy resin adhesive (9-2) evenly to the surface of the first layer of carbon fiber cloth (9-1) and roll it multiple times along the fiber direction with a debubbling roller. Near the weld, press firmly with a debubbling roller multiple times. Then, attach the second layer of carbon fiber cloth (9-1) and repeat several times until the predetermined number of carbon fiber cloth layers is reached to form a carbon fiber reinforced resin matrix composite material (9). S5. When the surface of the carbon fiber reinforced resin matrix composite (9) loses its fluidity but still has strong adhesion, apply an epoxy resin adhesive layer of 1.0 to 1.5 mm thickness to a predetermined position on the carbon fiber reinforced resin matrix composite (9), and attach the angle steel to the carbon fiber reinforced resin matrix composite (9). If there is a gap between the carbon fiber reinforced resin matrix composite (9) and the angle steel, fill it with a small amount of epoxy resin adhesive. S6. Several sets of auxiliary reinforcement devices (10) are pasted at a distance of 10-20mm from the edge of the angle steel. The base (10-1) is fixed to the surface of the base material with modified acrylic adhesive, and a limiting device (10-3) is installed on the lower base (10-1). Then, the strip (10-2) is inserted into the base (10-1), and the strip is raised with a shim to ensure that the bottom surface of the strip is flush with the upper surface of the angle steel. Then, the strip is tightened with a nut. The auxiliary reinforcement device (10) is as follows: the surface of the base (10-1) is provided with a bolt rod assembly, the two ends of the strip (10-2) are provided with through holes, the strip (10-2) is sleeved on the bolt rod assembly, and a limiting device (10-3) is provided between one of the bases (10-1) and the strip (10-2). S7. After the bottom carbon fiber reinforced resin matrix composite material (9) is completely bonded to the angle steel and forms strength, remove the auxiliary reinforcement device (10) and remove the base adhesive left by the auxiliary reinforcement device. Then repeat steps S3 to S4 on the angle steel and carbon fiber reinforced resin matrix composite material (9) to bond the carbon fiber reinforced resin matrix composite material (9) to form a composite layer of combined reinforcement structure to bear the force together.

2. The cold and hot combined reinforcement method for the distortion fatigue details of steel bridges according to claim 1, characterized in that: The combined reinforcement structure in step S7 consists of carbon fiber cloth, angle steel, and carbon fiber cloth.

3. The cold and hot combined reinforcement method for the distortion fatigue details of steel bridges according to claim 1, characterized in that: The carbon fiber reinforced resin matrix composite material (9) is formed by coating several layers of carbon fiber cloth (9-1) with epoxy resin adhesive (9-2) and bonding them together.

4. The cold and hot combined reinforcement method for steel bridge distortion fatigue details according to claim 1, characterized in that: In step S4, the carbon fiber reinforced resin matrix composite material (9) base layer is made of 4 to 6 layers of carbon fiber cloth (9-1) coated with epoxy resin adhesive (9-2) and bonded together. Each layer of carbon fiber cloth (9-1) is bonded together by alternating orthogonal or oblique bonding.

5. The cold and hot combined reinforcement method for steel bridge distortion fatigue details according to claim 1, characterized in that: The carbon fiber cloth (9-1) is pasted over an area 100-200 mm beyond the perimeter of the angle steel, and the edge of the angle steel extends 50-150 mm beyond the crack tip at the distortion fatigue detail.

6. The cold and hot combined reinforcement method for steel bridge distortion fatigue details according to claim 1, characterized in that: The angle steel has a leg width of not less than 120mm, a leg length of not less than 200mm, and a leg thickness of 10-14mm; the angle steel is made by cold rolling or by processing through-welded steel plates.

7. The cold and hot combined reinforcement method for steel bridge distortion fatigue details according to claim 1, characterized in that: The angle steel is one of the following: unequal-sided double-limb angle steel (7), equilateral double-limb angle steel (8), and triple-limb angle steel (12).

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