Steel bridge distortion fatigue carbon fiber cloth and multi-limb angle steel composite reinforcement structure and process

Abstract

A kind of steel bridge distortion fatigue carbon fiber cloth and multi-limb angle steel composite reinforcing structure and process, vertical steel plate beam web is arranged between upper wing plate and lower wing plate, vertical stiffening rib is arranged between steel plate beam web and wing plate, horizontal node plate is vertically arranged in the height direction of steel plate beam web, vertical stiffening rib vertically passes through horizontal node plate, and horizontal node plate web gap area and vertical stiffening rib web gap area are reinforced using carbon fiber reinforced resin base and multi-limb angle steel composite structure;When reinforcing using the reinforcing process, before the strength of composite structure glue layer is not consolidated to form, auxiliary device needs to be fixed, after removing auxiliary reinforcing device, carbon fiber cloth is pasted on the surface of angle steel to form composite reinforcing structure layer.The reinforcing structure is suitable for 50-100mm long distortion fatigue crack reinforcement, can effectively improve the stress performance of web gap, improve the ability of inhibiting detail distortion fatigue crack initiation and expansion, has the advantages of convenient construction, low cost and excellent performance.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering technology, specifically relating to a composite reinforcement structure and process of carbon fiber cloth and multi-limb angle steel for steel bridge distortion fatigue. Background Technology

[0002] With the increasing traffic volume, the fatigue problem of existing steel bridges is becoming increasingly prominent. In steel bridge design, to avoid introducing welding residual stress at the connection between the horizontal node plate and the web of the main girder, holes are usually made in the horizontal node plate to allow vertical stiffeners to pass through, leaving a gap between the vertical stiffeners and the tension flange. This results in the gap between the web of the vertical stiffeners and the web of the horizontal node plate. In actual operation, under vehicle loads, deflection differences will occur between the main girders, causing distortion deformation at the web gaps with lower stiffness. This leads to large distortion stress at the welded details, causing fatigue cracks to initiate and propagate at these points, posing a hidden danger to the safety of the bridge. Therefore, effective reinforcement measures are needed to repair and strengthen existing steel bridges to address fatigue cracks caused by distortion deformation. Traditional repair measures for fatigue cracks in web gaps include setting crack arrest holes at the crack tip or using crack fusion methods. However, crack arrest holes can only temporarily delay crack propagation, and crack fusion can lead to secondary fatigue cracking. Therefore, there is an urgent need to develop a reinforcement structure that can both avoid secondary fatigue cracking and effectively suppress the formation and propagation of fatigue cracks caused by distortion and deformation at the web gaps. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a steel bridge distortion fatigue reinforcement structure composed of carbon fiber cloth and angle steel that is reasonable in structure, simple in construction, has excellent stress performance and convenient in construction.

[0004] The technical solution adopted to solve the above-mentioned technical problems is: a composite reinforcement structure of carbon fiber cloth and multi-limb angle steel for steel bridge distortion fatigue. A steel plate beam web is vertically arranged between the upper and lower flanges. Vertical stiffeners are vertically arranged between the web and the flanges. A horizontal node plate is vertically arranged in the height direction of the web of the steel plate beam. The vertical stiffeners pass through the horizontal node plates vertically. A concrete bridge deck is cast in a mold on the upper part of the upper flange. The web gap of the vertical stiffeners is formed by the upper flange, the web, and the vertical stiffeners. The web gap of the horizontal node plates is formed by the web, the vertical stiffeners, and the horizontal node plates. The area between the web gap of the horizontal node plates and the web gap of the vertical stiffeners is reinforced by a composite structure of carbon fiber reinforced resin matrix and angle steel.

[0005] The carbon fiber reinforced resin matrix of the present invention is formed by coating several layers of carbon fiber cloth with epoxy resin adhesive and bonding them together.

[0006] The composite structure of the present invention is composed of several layers of carbon fiber cloth, angle steel, and several layers of carbon fiber cloth.

[0007] In this invention, the carbon fiber reinforced resin matrix is ​​bonded to the web, vertical stiffening ribs, and horizontal node plates of a steel plate beam using structural adhesive. Angle steel is bonded to the carbon fiber reinforced resin matrix using structural adhesive, and the carbon fiber reinforced resin matrix is ​​bonded to the angle steel using structural adhesive to form a composite structure.

[0008] The structural adhesive of this invention is an epoxy resin adhesive. The thickness of the epoxy resin adhesive between the web of the steel plate beam, the vertical stiffening ribs, the horizontal node plates and the carbon fiber reinforced resin matrix is ​​0.3 to 0.5 mm, and the thickness of the epoxy resin adhesive between the carbon fiber reinforced resin matrix and the angle steel is 1.0 to 1.5 mm.

[0009] The angle steel of the present invention has a leg width of not less than 80mm, a leg length of not less than 100mm, and a leg thickness of 6-12mm; the angle steel is made by cold rolling or by processing steel plate.

[0010] The composite structure of the present invention is temporarily fixed by a slat-assisted reinforcement device, which consists of a screw assembly welded to the upper part of the base, through holes machined on the slats, the screw assembly disposed in the through holes, and a limit device provided between the slats and the base.

[0011] The reinforcement process of the composite reinforcement structure of carbon fiber cloth and multi-limb angle steel for steel bridge distortion fatigue of the present invention is characterized by including the following steps:

[0012] S1. Clean and roughen the bonding surfaces of the vertical stiffening ribs, steel plate beam web, upper flange, and carbon fiber reinforced resin matrix. The surface of the angle steel needs to be ground and sandblasted.

[0013] S2. Apply epoxy resin primer with a thickness of 0.3 to 0.5 mm evenly to the bonding surface of the treated vertical stiffening ribs and steel plate beam web, bond the first layer of carbon fiber cloth, and use debubbling rollers to roll the carbon fiber cloth multiple times along the fiber direction to fully impregnate the epoxy resin with the carbon fiber cloth.

[0014] S3. After the surface of the first layer of carbon fiber cloth is touch dry, apply 0.3-0.5mm of epoxy resin evenly to the surface of the first layer of carbon fiber cloth and roll it 2-3 times along the fiber direction with a debubbling roller. Then, attach the second layer of carbon fiber cloth and repeat this process several times until the predetermined thickness is reached to form a carbon fiber reinforced resin matrix.

[0015] S4. Apply a 1.0-1.5mm thick structural adhesive layer to a predetermined position on the carbon fiber reinforced resin matrix, and then attach the angle steel to the carbon fiber reinforced resin matrix.

[0016] S5. Attach an even number of auxiliary reinforcement device bases 10-20mm away from the edge of the angle steel, and install a limiting device on the lower base. Then, insert the opening on the strip into the screw of the fixed base and tighten it with a nut.

[0017] S6. After the bottom carbon fiber reinforced resin matrix and the angle steel have formed strength, remove the slatted auxiliary reinforcement device, and then repeat steps S2 to S3 to attach 2 to 4 layers of carbon fiber cloth to the surface of the angle steel as a protective layer for the reinforcement structure.

[0018] The carbon fiber reinforced resin matrix of the present invention is formed by bonding 4 to 6 layers of carbon fiber cloth with epoxy resin adhesive, and each layer of carbon fiber cloth is orthogonally or obliquely bonded.

[0019] The carbon fiber cloth bonding area obtained by this invention is 50-150mm larger than the perimeter of the angle steel.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. This invention utilizes structural adhesive to bond and fix the composite structure of carbon fiber reinforced resin matrix and multi-limb angle steel to the vertical stiffening ribs and web, avoiding the damage to the adhesive layer caused by the opening and closing of fatigue cracks at the weld toe of the web-vertical stiffening rib under fatigue load when multi-limb angle steel is bonded alone, thus preventing the bonded angle steel from peeling off. It also overcomes the shortcomings of bonding carbon fiber cloth alone, which only slightly improves the stiffness of the web gap distortion and cannot suppress the propagation of fatigue cracks.

[0022] 2. This invention uses a composite structure of carbon fiber reinforced resin matrix and multi-limb angle steel for reinforcement. The carbon fiber reinforced resin matrix is ​​composed of several layers of carbon fiber cloth coated with epoxy resin adhesive and bonded together. This fully utilizes the good bonding and tensile properties of carbon fiber cloth, which can reduce the stress at the crack tip. The multi-limb angle steel is bonded to the surface of the carbon fiber reinforced resin matrix to improve the stiffness of the web gap, thereby effectively improving the stress performance of the web gap and effectively inhibiting the propagation of 50-100mm long distortion fatigue cracks.

[0023] 3. The present invention employs an auxiliary reinforcement device that combines slats, limiting devices, and a fixed base. This device provides reliable temporary fixation between the multi-limb angle steel and the carbon fiber reinforced resin matrix composite material before the adhesive layer has fully solidified and gained strength. At the same time, it uses modified acrylic adhesive to fix the steel bridge deck without damaging the original structure.

[0024] In summary, the reinforcement structure of this invention has the advantages of good durability, strong resistance to distortion fatigue, lightweight structure, simple construction, and low cost. This reinforcement structure is suitable for reinforcing distortion fatigue cracks with a length of 50-100mm. It can be widely applied to the field of distortion fatigue reinforcement of steel bridges. Attached Figure Description

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

[0026] Figure 2 This is a schematic diagram of a local three-dimensional structure for reinforcing the web gap of the horizontal node plate in Example 1.

[0027] Figure 3 This is a schematic diagram of the local three-dimensional structure of the reinforcement of the web gap of the vertical stiffening rib in Example 2.

[0028] Figure 4 yes Figure 2 , 3 A three-dimensional structural diagram of the middle angle steel 3.

[0029] Figure 5 This is a schematic diagram of the composite structure of carbon fiber reinforced resin matrix 4 and angle steel 3 of the present invention.

[0030] Figure 6 This is a schematic diagram of the structure of the carbon fiber reinforced resin matrix 4 of the present invention.

[0031] Figure 7 This is a schematic diagram of the three-dimensional structure for temporary fixing of the horizontal node plate web gap reinforcement according to the present invention.

[0032] Figure 8 This is a schematic diagram of the three-dimensional structure for temporary fixation of the vertical stiffening rib web gap reinforcement of the present invention.

[0033] Figure 9 This is a three-dimensional structural schematic diagram of the slat-assisted reinforcement device 9 of the present invention.

[0034] Figure 10 This is an application example of the present invention.

[0035] In the diagram: 1. Steel bridge deck; 2. Upper flange; 3. Angle steel; 4. Carbon fiber reinforced resin matrix; 5. Steel plate girder web; 6. Vertical stiffening rib; 7. Horizontal node plate; 8. Lower flange; 9. Slat auxiliary reinforcement device; 4-1. Carbon fiber cloth; 4-2. Epoxy resin adhesive; 9-1. Base; 9-2. Slat; 9-3. Limiting device. Detailed Implementation

[0036] 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.

[0037] Example 1

[0038] exist Figure 1 , 2In section 4, the present invention relates to a distortion fatigue strengthening structure for a composite steel bridge made of carbon fiber cloth and multi-limb angle steel. A steel plate girder web 5 is vertically arranged between the upper flange 2 and the lower flange 8. Vertical stiffening ribs 6 are vertically arranged between the steel plate girder web 5 and the flange. A horizontal node plate 7 is vertically arranged along the height direction of the steel plate girder web 5. The vertical stiffening ribs 6 pass vertically through the horizontal node plate 7. A steel bridge deck 1 is cast in a mold on the upper flange 2. The gap between the horizontal node plate web and the steel plate girder web is formed by the steel plate girder web 5, the vertical stiffening ribs 6, and the horizontal node plate 7. A composite structure of carbon fiber reinforced resin matrix 4 and angle steel 3 is used to strengthen the area of ​​the gap between the horizontal node plate web and the steel plate girder web. Figure 5 , 6 As shown, the composite structure described above consists of several layers of carbon fiber cloth 4-1, angle steel 3, and several layers of carbon fiber cloth 4-1. Specifically, the carbon fiber reinforced resin matrix 4 is bonded to the web 5, vertical stiffeners 6, and horizontal node plates 7 of the steel plate beam using structural adhesive. The angle steel 3 is bonded to the carbon fiber reinforced resin matrix 4 using structural adhesive, and several layers of carbon fiber cloth 4-1 are bonded to the surface of the angle steel 3 using structural adhesive as a protective layer for the reinforcement structure. The aforementioned structural adhesive is epoxy resin adhesive. The thickness of the epoxy resin adhesive between the web 5, vertical stiffeners 6, horizontal node plates 7, and carbon fiber reinforced resin matrix 4 is 0.3–0.5 mm, and the thickness of the epoxy resin adhesive between the carbon fiber reinforced resin matrix 4 and the angle steel 3 is 1.0–1.5 mm. Figure 5 , 6 As shown, the carbon fiber reinforced resin matrix 4 is formed by bonding several layers of carbon fiber cloth 4-1 with epoxy resin adhesive 4-2. In this embodiment, the carbon fiber reinforced resin matrix 4 is formed by bonding 5 layers of carbon fiber cloth 4-1 with epoxy resin adhesive 4-2. The carbon fiber reinforced resin matrix 4 has good bonding and tensile properties, which can reduce the stress at the crack tip. By bonding angle steel 3 to the surface of the carbon fiber reinforced resin matrix 4, the stiffness of the web gap of the horizontal node plate is improved, 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 4 and angle steel 3 has the characteristics of good durability and good resistance to distortion fatigue.

[0039] like Figure 8As shown, the composite reinforcement structure formed by angle steel 3 and carbon fiber reinforced resin matrix 4 needs to be temporarily fixed before it gains strength. This invention uses a slat-assisted reinforcement device 9 for temporary fixing. Specifically, the slat-assisted reinforcement device 9 is composed of a base 9-1, a slat 9-2, a limiting device 9-3, and a screw assembly. A screw assembly is welded to the upper part of the base 9-1. A through hole is machined on the slat 9-2. The length of the slat 9-2 should preferably be 280–300 mm, and the thickness should preferably be 3–5 mm. The slat should have an opening 20 mm–40 mm long. The screw assembly is placed inside the through hole. A limiting device 9-3 is provided between the slat 9-2 and the base 9-1. The limiting device 9-3 is a 30×50 mm or 30×80 mm steel plate, with an opening diameter of 11 mm at one end. (Details follow...) Figure 7 As shown, the auxiliary reinforcement device base 9-1 measures 35×40mm, with an M10 bolt welded to the center. The strip is 300mm long, and the holes at both ends are 30mm long. In use, several even-numbered bases 9-1 are adhered to the desired location using modified acrylic adhesive, with an adhesive layer thickness of not less than 2mm. The number of limiting devices 9-3 is half the number of bases 9-1. The limiting devices 9-3 are adjusted to fit tightly against the composite structure surface, and the bolt assembly is tightened for temporary reinforcement.

[0040] Example 2

[0041] In the above embodiment 1, in Figure 1 , 3 In embodiment 4, the vertical stiffening rib 6 is welded to the lower flange 8 of the test beam. A 40mm*40mm triangular weld hole is provided on the vertical stiffening rib 6. The web gap of the vertical stiffening rib is formed by the upper flange 2, the web of the steel plate beam 5, and the vertical stiffening rib 6. A composite structure of carbon fiber reinforced resin matrix 4 and angle steel 3 is used to reinforce the area of ​​the web gap of the vertical stiffening rib. The aforementioned composite structure consists of several layers of carbon fiber cloth 4-1, angle steel 3, and several layers of carbon fiber cloth 4-1. Specifically, a 40mm web gap is formed at the upper flange 2 of the test beam. Carbon fiber reinforced resin matrix 4 is pasted to a predetermined thickness at the web of the steel plate beam 5, the vertical stiffening rib, and the upper flange 2 in the area of ​​the web gap of the vertical stiffening rib. Angle steel 3 is pasted on the carbon fiber reinforced resin matrix 4. One leg of the multi-limb angle steel is pasted on the web side, one leg on the vertical stiffening rib side, and the other leg on the upper flange side. Several layers of carbon fiber cloth 4-1 are bonded to the surface of the angle steel 3 using structural adhesive. The remaining components and their connection methods are the same as in Example 1.

[0042] In the above embodiments 1 and 2, the width of each leg of the angle steel 3 is not less than 80mm, the length of each leg is not less than 100mm, and the thickness of each leg is 6 to 12mm; the angle steel 3 is made by cold rolling or by processing steel plate.

[0043] In practice, the specifications and dimensions of the angle steel 3 and the carbon fiber reinforced resin matrix 4 can be adjusted according to the actual usage.

[0044] The reinforcement process of the steel bridge distortion fatigue reinforcement structure composed of carbon fiber cloth and angle steel involved in Examples 1-2 above includes the following steps:

[0045] S1. Clean and roughen the bonding surfaces of the vertical stiffening ribs 6, the web of the steel plate beam 5, the upper flange 2 and the carbon fiber reinforced resin matrix 4. The surface of the angle steel 3 needs to be ground and sandblasted.

[0046] S2. Apply epoxy resin primer with a thickness of 0.3 to 0.5 mm evenly to the bonding surface of the treated vertical stiffening ribs 6 and the web of the steel plate beam 5, then bond the first layer of carbon fiber cloth 4-1, and use a debubbling roller to roll the carbon fiber cloth 4-1 multiple times along the fiber direction to fully impregnate the epoxy resin with the carbon fiber cloth 4-1.

[0047] S3. After the surface of the first layer of carbon fiber cloth 4-1 is dry to the touch, apply 0.3-0.5mm of epoxy resin adhesive 4-2 evenly to the surface of the first layer of carbon fiber cloth 4-1 and roll it 2-3 times along the fiber direction with a debubbling roller. Then, attach the second layer of carbon fiber cloth 4-1. Repeat this process several times until the predetermined thickness is reached to form the carbon fiber reinforced resin matrix 4.

[0048] S4. Apply a 1.0-1.5 mm thick structural adhesive layer to a predetermined position on the carbon fiber reinforced resin matrix 4, and then attach the angle steel 3 to the carbon fiber reinforced resin matrix 4.

[0049] S5. Attach an even number of auxiliary reinforcement device bases 9-1 at a distance of 10-20mm from the edge of angle steel 3, and install a limiting device 9-3 on the lower base 9-1. Then, insert the opening on the strip 9-2 into the screw of the fixed base 9-1 and tighten it with a nut.

[0050] S6. After the bottom carbon fiber reinforced resin matrix 4 and the angle steel 3 have reached the required strength, remove the slatted auxiliary reinforcement device 9, and then repeat steps S2 to S3 to attach 2 to 4 layers of carbon fiber cloth 4-1 to the surface of the angle steel 3 as a protective layer for the reinforcement structure.

[0051] The aforementioned carbon fiber reinforced resin matrix 4 is composed of 4 to 6 layers of carbon fiber cloth 4-1 bonded together with epoxy resin adhesive 4-2. Each layer of carbon fiber cloth 4-1 is bonded orthogonally or obliquely. The bonding area of ​​the carbon fiber cloth 4-1 should extend 50 to 150 mm beyond the perimeter of the angle steel 3 to ensure the bonding stability of the angle steel 3.

[0052] Experiment 1

[0053] like Figure 10As shown, to test the reinforcement effect, the inventors conducted a reinforcement effect evaluation test. The reinforced specimen is an I-shaped steel beam welded from an upper flange 2, a lower flange 8, vertical stiffeners 6, and a steel plate beam web 5, with double horizontal node plates 7. The upper flange 2 and lower flange 8 are rectangular steel plates with a length of 600mm, a width of 300mm, and a thickness of 24mm; the steel plate beam web 5 is a rectangular steel plate with a length of 600mm, a height of 870mm, and a thickness of 8mm; the vertical stiffeners 6 are rectangular steel plates with a length of 120mm, a height of 870mm, and a thickness of 6mm; the horizontal node plates 7 are rectangular steel plates with a length of 360mm, a height of 230mm, and a thickness of 10mm, with a semi-circular notch of 83mm radius. The vertical stiffeners 6 pass through the semi-circular notch and connect to the steel plate beam web 5; the gap between the horizontal node plate webs is reinforced using a composite structure of carbon fiber reinforced resin matrix 4 and angle steel 3. The carbon fiber reinforced resin matrix 4 is bonded to the web 5 and vertical stiffeners 6 of the steel plate beam using epoxy resin adhesive. The angle steel 3 has a leg thickness of 8 mm and is bonded to the carbon fiber reinforced resin matrix 4 using epoxy resin adhesive with a thickness of 1.0 mm. In this specimen, the carbon fiber reinforced resin matrix 4 is composed of 5 layers of carbon fiber cloth 4-1 coated with epoxy resin adhesive 4-2 and bonded together. The distance between the upper end of the carbon fiber reinforced resin matrix 4 and the upper flange 2, and the distance between the lower end of the carbon fiber reinforced resin matrix 4 and the lower flange 8, are both 150 mm. Fatigue cracks were pre-induced on the I-beam specimen, and tests were conducted on the reinforced specimen. The test results are as follows:

[0054] I. Testing Instruments

[0055] MTS servo hydraulic control system; TDS-602 static resistance strain gauge (made in Japan); WBD type electromechanical dial indicator (made by Wenling Kete Electronic Instrument Factory, Zhejiang Province).

[0056] II. Reinforcement Effect Test

[0057] 1. Specimen design parameters

[0058] The specimen was made of Q345 steel with an elastic modulus of 2.06 × 10⁻⁶. 5 MPa. The distance between the two loading points is 440mm.

[0059] 2. Test apparatus and loading procedure

[0060] Both the upper flange 2 and the lower flange 8 of the specimen were fixed to the base with high-strength bolts. A cyclic loading was applied perpendicular to the web of the steel plate girder on the vertical stiffening rib 6 to simulate the load transmitted by the cross bracing in an actual steel bridge. During the test, the specimen was first subjected to pre-existing crack fatigue loading until cracks initiated in the gap between the vertical stiffening rib 6 and the horizontal node plate 7 of the steel plate girder web. Before reinforcement, a static load test was conducted on the specimen with pre-existing cracks to measure the displacement and stress at each measuring point before reinforcement, for comparison with the post-reinforcement state. The specimen was then reinforced with a composite structure of carbon fiber reinforced resin matrix 4 and angle steel 3, and cured. After the epoxy resin adhesive cured, another static load test was conducted to measure the displacement and stress at each measuring point after reinforcement. Finally, cyclic loading was performed to verify the effectiveness of the reinforcement method.

[0061] 3. Experimental Results and Analysis

[0062] (1) Composite reinforcement structure of bonded carbon fiber cloth and angle steel

[0063] The distortion deformation amplitudes of the specimens before and after reinforcement are shown in Table 1. Distortion deformation amplitude ① in Table 1 is the distortion deformation value at the web gap obtained by static testing before fatigue cyclic loading of the web gap, at which point the number of cycles N=0. Distortion deformation amplitude ② is the distortion deformation amplitude at the web gap obtained by static testing when the fatigue crack at the web gap has expanded to a certain extent and the fatigue test has stopped (i.e., the number of fatigue loading cycles before reinforcement is 1.4 million). Distortion deformation amplitude ③ is the distortion deformation amplitude at the web gap obtained by static testing after repair and reinforcement of the web gap. Distortion deformation amplitude ④ is the data obtained by the final static test at the end of the fatigue test on the reinforced specimen (the number of fatigue loading cycles after reinforcement is 2 million). In Table 1, measuring points WS and WN are the web gap distortion deformation measuring points on the west side of the specimen in the north-south direction, respectively, and measuring points EN and ES are the web gap distortion deformation measuring points on the east side of the specimen in the north-south direction, respectively.

[0064] Table 1 Comparison of distortion and deformation amplitudes at measuring points of specimens before and after reinforcement

[0065]

[0066] As shown in Table 1, after the repair and reinforcement using the composite structure of bonded carbon fiber reinforced resin matrix 4 and angle steel 3, the distortion and deformation amplitude of each measuring point under the same load amplitude is significantly reduced, and the distortion and deformation values ​​after reinforcement are very small, indicating that the reinforcement effect is good.

[0067] Table 2 compares the stress amplitudes of the web plate beam with web gap 5 – vertical stiffener 6 weld toe details before and after reinforcement. The stress amplitudes ①, ②, ③, and ④ in Table 2 have the same number of test cycles as the distortion deformation amplitudes ①, ②, ③, and ④ in Table 1. Measurement points WN and WS in Table 2 are the measurement points at the web plate beam with web gap 5 – vertical stiffener 6 weld toe on the west side of the specimen in the north-south direction, while measurement points EN and ES are the measurement points at the web plate beam with web gap 5 – vertical stiffener 6 weld toe on the west side of the specimen in the north-south direction.

[0068] Table 2 Comparison of stress amplitude at the weld toe before and after reinforcement

[0069]

[0070] As shown in Table 2, after adopting the repair scheme of bonding carbon fiber reinforced resin matrix 4 and angle steel 3 composite structure, the stress amplitude of each measuring point of the test beam under the same load amplitude is significantly reduced, and the stress of the measuring points after reinforcement is very small, indicating that the reinforcement effect is good.

[0071] Table 3 shows the variation of distortion deformation amplitude at the web gap with load. Time 1, time 2, time 3, and time 4 correspond to the completion time of the number of cycles during the testing of distortion deformation amplitude ①, distortion deformation amplitude ②, distortion deformation amplitude ③, and distortion deformation amplitude ④ in Table 1, respectively. In Table 3, measuring points D-WN and D-WS are the measuring points for distortion deformation of the web gap between the web 5 and the horizontal node plate 7 of the specimen steel plate beam, respectively. Measuring points EN and ES are the measuring points for distortion deformation of the web 5 and the web gap between the web 5 and the lower horizontal node plate 7 of the specimen steel plate beam, respectively.

[0072] Table 3 Comparison of distortion amplitude at the weld toe before and after reinforcement.

[0073]

[0074] As shown in Table 3, the distortion value of the web gap was significantly reduced after reinforcement. Moreover, at the end of the test, the distortion value obtained after cyclic loading was almost unchanged compared with the distortion value obtained after reinforcement without cyclic loading, indicating that the reinforcement effect was good.

[0075] Comparative Example 1

[0076] Angle steel reinforcement

[0077] Similar in size to the test beam reinforced with the composite structure of bonded carbon fiber cloth and multi-limb angle steel, multi-limb angle steel of the same size was individually bonded to the gap area between the web plates of the horizontal node plates for reinforcement. A total of 1 million fatigue tests were conducted after reinforcement. At 400,000 cycles of loading, some of the bonded multi-limb angle steel reinforcement components showed adhesive failure. At 800,000 cycles of fatigue loading, all the bonded multi-limb angle steel reinforcement components failed. Table 4 shows the variation of the distortion deformation amplitude at the peak load at the gap between the web plates of the horizontal node plates of the test beam after bonding the multi-limb angle steel reinforcement components with the number of fatigue loading cycles. The symbols for the distortion deformation measurement points in Table 4 are the same as those representing the measurement points in Table 1. Due to the continuous peeling of the adhesive layer at the interface of the bonded angle steel reinforcement components during fatigue loading, the distortion deformation amplitude at the measurement points in the gap between the web plates of the horizontal node plates continuously increased, indicating a continuous decrease in the reinforcement effect of the reinforcement components.

[0078] Table 4. Comparison of distortion and deformation amplitude at the weld toe after reinforcement with bonded multi-limb angle steel components.

[0079]

[0080] Comparative Example 2

[0081] Carbon fiber cloth reinforcement

[0082] Similar in size to the test beam reinforced with the composite structure of carbon fiber cloth and multi-limb angle steel, carbon fiber reinforced resin matrix of the same size and thickness was separately bonded in the web gap area of ​​the horizontal node plate. A total of 2.5 million fatigue tests were conducted after reinforcement. No peeling of the bond interface between the carbon fiber reinforced resin matrix and the test beam was observed during these 2.5 million fatigue tests, and no fatigue damage was found in the carbon fiber reinforced resin matrix. Table 5 shows the change in distortion deformation amplitude under peak load at the web gap of the horizontal node plate of the test beam reinforced with carbon fiber reinforced resin matrix as a function of the number of fatigue loading cycles. The symbols for the distortion deformation measurement points in Table 5 are the same as those representing the measurement points in Table 1. Therefore, it can be seen that bonding carbon fiber reinforced resin matrix has limited effect on improving the stress distribution in the web gap and reducing distortion deformation at the details.

[0083] Table 5. Comparison of distortion and deformation amplitude at the weld toe after reinforcement with carbon fiber cloth.

[0084]

[0085] In summary, the fatigue resistance of the multi-limb angle steel reinforcement component bonded alone is poor, and it fails after 400,000 fatigue loading cycles. The effect of bonding carbon fiber cloth reinforcement on improving the stress at the web gap and reducing the distortion amplitude under peak load at the gap is limited. The fatigue reinforcement scheme using a composite structure of bonded carbon fiber reinforced resin matrix 4 and angle steel 3 to reinforce the web gap distortion deformation shows a significant reduction in both distortion amplitude and stress amplitude after reinforcement. Moreover, the composite structure of bonded carbon fiber reinforced resin matrix 4 and angle steel 3 did not fail after 2 million cycles of loading, indicating that the fatigue reinforcement structure is safe and reliable.

Claims

1. A composite reinforcement structure of carbon fiber cloth and multi-limb angle steel for steel bridge distortion fatigue, wherein a steel plate beam web (5) is vertically arranged between the upper flange (2) and the lower flange (8), and a vertical stiffening rib (6) is vertically arranged between the steel plate beam web (5) and the flange, and a horizontal node plate (7) is vertically arranged in the height direction of the steel plate beam web (5), and the vertical stiffening rib (6) passes vertically through the horizontal node plate (7), and a concrete bridge deck (1) is cast on the upper part of the upper flange (2), the gap between the vertical stiffening rib web is formed by the upper flange (2), the steel plate beam web (5) and the vertical stiffening rib (6), and the gap between the horizontal node plate web is formed by the steel plate beam web (5), the vertical stiffening rib (6) and the horizontal node plate (7), characterized in that: The area between the web of the horizontal node plate and the web of the vertical stiffening rib is reinforced with a composite structure of carbon fiber reinforced resin matrix (4) and angle steel (3); The composite structure is temporarily fixed by a slat reinforcement device (9). The slat reinforcement device (9) consists of: a screw assembly welded to the upper part of the base (9-1), a through hole machined on the slat (9-2), the screw assembly set in the through hole, and a limit device (9-3) set between the slat (9-2) and the base (9-1). The carbon fiber reinforced resin matrix (4) is formed by coating several layers of carbon fiber cloth (4-1) with epoxy resin adhesive (4-2) and impregnating and bonding them together. The composite structure is composed of several layers of carbon fiber cloth (4-1) - angle steel (3) - several layers of carbon fiber cloth (4-1); The carbon fiber reinforced resin matrix (4) is bonded to the web (5), vertical stiffening rib (6), and horizontal node plate (7) of the steel plate beam with structural adhesive. The angle steel (3) is bonded to the carbon fiber reinforced resin matrix (4) with structural adhesive. The carbon fiber reinforced resin matrix (4) is bonded to the angle steel (3) with structural adhesive to form a composite structure.

2. The composite reinforcement structure of carbon fiber cloth and multi-limb angle steel for steel bridge distortion fatigue according to claim 1, characterized in that: The structural adhesive is epoxy resin adhesive. The thickness of the epoxy resin adhesive between the web plate (5), vertical stiffening rib (6), horizontal node plate (7) and carbon fiber reinforced resin matrix (4) is 0.3-0.5 mm, and the thickness of the epoxy resin adhesive between the carbon fiber reinforced resin matrix (4) and angle steel (3) is 1.0-1.5 mm.

3. The composite reinforcement structure of carbon fiber cloth and multi-limb angle steel for steel bridge distortion fatigue according to claim 1, characterized in that: The angle steel (3) has a width of not less than 80mm, a length of not less than 100mm, and a thickness of 6-12mm for each leg; the angle steel (3) is made by cold rolling or by processing steel plate.

4. The reinforcement process of the composite reinforcement structure of carbon fiber cloth and multi-limb angle steel for steel bridge distortion fatigue according to any one of claims 2 and 3, characterized in that... Includes the following steps: S1. Clean and roughen the bonding surfaces of the vertical stiffening ribs (6), the web of the steel plate beam (5), the upper flange (2) and the carbon fiber reinforced resin matrix (4). The surface of the angle steel (3) needs to be ground and sandblasted. S2. Apply epoxy resin primer with a thickness of 0.3 to 0.5 mm evenly to the bonding surface of the treated vertical stiffening rib (6) and the web of the steel plate beam (5), then bond the first layer of carbon fiber cloth (4-1), and use a debubbling roller to roll the carbon fiber cloth (4-1) multiple times along the fiber direction so that the epoxy resin adhesive and the carbon fiber cloth (4-1) are fully impregnated. S3. After the surface of the first layer of carbon fiber cloth (4-1) is dry to the touch, apply 0.3-0.5mm of epoxy resin adhesive (4-2) evenly to the surface of the first layer of carbon fiber cloth (4-1) and roll it 2-3 times along the fiber direction with a debubbling roller. Then, attach the second layer of carbon fiber cloth (4-1) and repeat several times until the predetermined thickness is reached to form a carbon fiber reinforced resin matrix (4). S4. Apply a 1.0-1.5 mm thick structural adhesive layer to a predetermined position on the carbon fiber reinforced resin matrix (4), and attach the angle steel (3) to the carbon fiber reinforced resin matrix (4); S5. Attach an even number of auxiliary reinforcement device bases (9-1) at a distance of 10-20mm from the edge of the angle steel (3), and install a limiting device (9-3) on the lower base (9-1). Then, insert the opening on the strip (9-2) into the screw of the fixed base (9-1) and tighten it with a nut. S6. After the bottom carbon fiber reinforced resin matrix (4) and the angle steel (3) have reached the required strength, remove the slatted auxiliary reinforcement device (9), and then repeat steps S2 to S3 to attach 2 to 4 layers of carbon fiber cloth (4-1) to the surface of the angle steel (3) as a protective layer for the reinforcement structure.

5. The reinforcement process of the composite reinforcement structure of carbon fiber cloth and multi-limb angle steel for steel bridge distortion fatigue according to claim 4, characterized in that: The carbon fiber reinforced resin matrix (4) is formed by bonding 4 to 6 layers of carbon fiber cloth (4-1) with epoxy resin adhesive (4-2), and each layer of carbon fiber cloth (4-1) is bonded together by orthogonal or oblique bonding.

6. The reinforcement process of the composite reinforcement structure of carbon fiber cloth and multi-limb angle steel for steel bridge distortion fatigue according to claim 4, characterized in that: The carbon fiber cloth (4-1) is pasted over a range of 50-150 mm more than the angle steel (3) around its perimeter.

Images