Thermal repair method for fatigue crack of fillet weld of steel bridge

Abstract

The invention relates to a thermal repair method for a fatigue crack of a fillet weld of a steel bridge. The method comprises the following steps: detecting a fatigue crack at the fillet weld of the steel bridge, and determining the extension trend of the fatigue crack; applying pretension to two sides of the fatigue crack, wherein the pretension is used for enabling an opening gap of the fatigue crack to reach a preset size; under the operation condition of keeping pretension, the fatigue crack is planed along the extension direction of the fatigue crack, and a planed steel bridge fillet weld is obtained; and under the operation condition that pretension is kept, a welding material is adopted for conducting thermal repair on the dug steel bridge fillet weld, and the steel strength grade and the quality grade of the welding material are matched with the steel bridge fillet weld. By adopting the method, the fatigue stress amplitude of the repaired fillet weld of the steel bridge in the service state can be greatly reduced, the possibility that fatigue cracks appear again at the original fatigue cracks on the fillet weld of the diaphragm plate and near the original fatigue cracks is fundamentally eliminated, and the purpose of repairing the fatigue cracks is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of steel bridge maintenance and reinforcement, and in particular to a thermal repair method for fatigue cracks in corner welds of steel bridges. Background Art

[0002] my country introduced steel bridge deck technology in the early 1970s, and began to build steel bridges with steel bridge decks on a large scale in the 1990s. So far, a large number of steel bridges with steel bridge decks have been built in China. However, due to the overall level of cognition and design of steel bridge decks at that time, some steel bridges had a large number of fatigue cracks soon after they were put into use. The probability of fatigue cracks occurring at the fillet welds where the fillet welds are welded to the U-ribs and the fillet welds where the fillet welds are welded to the bridge deck is relatively high, which directly affects the safety of the bridge structure and driving safety.

[0003] At present, due to the structural characteristics of the fillet weld, fatigue cracks in the fillet weld can only be repaired by welding. However, after the welding heat repair, tensile stress is often introduced on or near the weld where the original crack is repaired, which will cause fatigue cracks to re-occur. Summary of the invention

[0004] Based on this, it is necessary to provide a thermal repair method for fatigue cracks in steel bridge corner welds that is less likely to produce fatigue cracks again in response to the above technical problems.

[0005] In a first aspect, the present application provides a method for thermally repairing fatigue cracks in fillet welds of steel bridges, comprising:

[0006] Detect fatigue cracks at fillet welds of steel bridges and determine the propagation direction of the fatigue cracks;

[0007] Applying pre-tension on both sides of the fatigue crack, wherein the pre-tension is used to make the opening gap of the fatigue crack reach a preset size;

[0008] Under the operating condition of maintaining the pre-tension, planing the fatigue crack along the extension direction of the fatigue crack to obtain the planed steel bridge fillet weld;

[0009] Under the operating condition of maintaining the pre-tension, the planed steel bridge fillet weld is thermally repaired using welding materials, and the steel strength grade and quality grade of the welding materials match the steel bridge fillet weld.

[0010] In one of the embodiments, the pre-tension is used to make the opening gap of the fatigue crack heel greater than 2 mm, and the pre-tension does not exceed the metal yield strength of the steel bridge.

[0011] In one embodiment, the process of thermally repairing the planed steel bridge fillet weld using welding materials while maintaining the pre-tensioning force comprises:

[0012] Under the operating condition of maintaining the pre-tension, the welding material is welded at the fillet weld of the planed steel bridge using a preset linear energy.

[0013] In one embodiment, the energy threshold of the preset line energy does not exceed 15 kJ / cm.

[0014] In one embodiment, after the hot repair of the planed steel bridge fillet weld using welding materials under the operating condition of maintaining the pre-tension, the method further comprises:

[0015] Under the operating condition of maintaining the pre-tension, the fillet weld of the steel bridge after thermal repair is polished to be smooth.

[0016] In one embodiment, before the hot-repaired steel bridge fillet weld is polished smooth under the operating condition of maintaining the pre-tension, the method further comprises:

[0017] Performing ultrasonic flaw detection on the thermally repaired steel bridge fillet weld to obtain defect detection results of the thermally repaired steel bridge fillet weld;

[0018] Determine that the defect detection result is no defect.

[0019] In one embodiment, after detecting fatigue cracks at fillet welds of steel bridges and determining the extension direction of the fatigue cracks, the method further includes:

[0020] A temporary crack arrest hole is drilled at the tip position of the fatigue crack, and the temporary crack arrest hole covers the tip position.

[0021] In one embodiment, the temporary crack-stop hole has a diameter of 10 mm.

[0022] In one embodiment, under the operating condition of maintaining the pre-tension, planing the fatigue crack along the extension direction of the fatigue crack to obtain the planed steel bridge fillet weld includes:

[0023] Under the operating condition of maintaining the pre-tension, the fatigue crack is air-planed along the expansion direction of the fatigue crack to form an air-planing groove with a width of 4-8 mm at the steel bridge fillet weld, thereby obtaining the planed steel bridge fillet weld.

[0024] In one embodiment, after the hot repair of the planed steel bridge fillet weld using the welding material under the operating condition of maintaining the pre-tension, the method further comprises:

[0025] The pre-tensioning force is released.

[0026] The above-mentioned thermal repair method for fatigue cracks in steel bridge corner welds determines the expansion direction of fatigue cracks by detecting fatigue cracks at steel bridge corner welds; applies pre-tension on both sides of the fatigue crack, and the pre-tension is used to make the opening gap of the fatigue crack reach a preset size; under the operating condition of maintaining the pre-tension, the fatigue crack is planed along the expansion direction of the fatigue crack to obtain the planed steel bridge corner weld; the corresponding welding material is matched according to the steel strength grade and quality grade of the steel bridge corner weld; under the operating condition of maintaining the pre-tension, the planed steel bridge corner weld is thermally repaired with welding materials, which can greatly reduce the fatigue stress amplitude of the service state of the repaired steel bridge corner weld, and fundamentally eliminate the possibility of fatigue cracking again at the original fatigue crack and its vicinity on the diaphragm corner weld, thereby achieving the purpose of repairing fatigue cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the drawings required for use in the embodiments of the present application or related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0028] FIG1 is an application environment diagram of a method for thermally repairing fatigue cracks in a steel bridge fillet weld according to an embodiment;

[0029] Figure 2 A schematic diagram of a process for thermally repairing fatigue cracks in a steel bridge fillet weld in one embodiment;

[0030] Figure 3 A schematic diagram of a temporary crack stop hole drilling step in one embodiment;

[0031] Figure 4 A schematic diagram of a pre-tensioning step in one embodiment;

[0032] Figure 5 A schematic diagram of a fatigue crack removal step in one embodiment;

[0033] Figure 6 A schematic flow chart of a method for thermally repairing fatigue cracks in a steel bridge fillet weld in another embodiment;

[0034] Figure 7 It is a schematic diagram of a steel bridge fillet weld after thermal repair in one embodiment. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0037] It should be understood that spatial relationship terms such as "on both sides", "on both sides", "at the heel", "at the tip", "under", "below", "below", "below", "above", "above", etc., can be used here to describe the relationship between an element or feature shown in the figures and other elements or features. It should be understood that in addition to the orientations shown in the figures, the spatial relationship terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, the elements or features described as "below other elements" or "below" or "below" will be oriented as "above" other elements or features. Therefore, the exemplary terms "below" and "below" can include both upper and lower orientations. In addition, the device can also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0038] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, in this specification, the term "and / or" includes any and all combinations of the relevant listed items.

[0039] The thermal repair method for fatigue cracks in fillet welds of steel bridges provided in the embodiment of the present application can be applied to the application environment shown in FIG. 1, including a bridge deck 102, a U-shaped rib 104, and a diaphragm 106. There is a crack 110 at the fillet weld at the welding position of the bridge deck 102 and the diaphragm 106. There is a crack 120 at the fillet weld at the welding position of the U-shaped rib 104 and the diaphragm 106.

[0040] The bridge deck 102 may be used to represent a load-bearing structure that directly bears vehicle wheel pressure, and is usually made of reinforced concrete.

[0041] The U-rib 104 may be used to characterize a steel reinforcement skeleton used to strengthen the stability of a plate-beam structure in bridge construction. It is a component composed of steel bars and steel plates, usually in a "U" shaped cross section, hence the name "U-rib".

[0042] The diaphragm 106 may be used to represent a member disposed between beams to maintain a cross-sectional shape and enhance lateral stiffness.

[0043] Since there is alternating tension and compression cyclic stress at the welding parts of the bridge deck 102 and the diaphragm 106 and the welding parts of the U-shaped rib 104 and the diaphragm 106, the difference between the maximum positive stress and the minimum negative stress (positive stress and negative stress are determined according to the direction of the force, for example, when the tensile stress is positive stress, the compressive stress opposite to the tensile stress is negative stress, and vice versa) will constitute the fatigue stress amplitude at the fillet weld. Fatigue stress amplitude is an important parameter in material fatigue analysis and can be used to evaluate the fatigue limit of materials or structures. In material fatigue life testing, fatigue stress amplitude can be used to evaluate the fatigue resistance of materials.

[0044] When the fatigue stress amplitude at the fillet weld exceeds the material fatigue strength of the steel bridge, cracks 110 and 120 will appear. Cracks 110 and 120 will gradually expand and become fatigue cracks at the fillet weld.

[0045] In an exemplary embodiment, Figure 2 As shown, a method for thermal repair of fatigue cracks in fillet welds of steel bridges is provided, and the method is applied to cracks 110 and 120 (hereinafter referred to as fatigue cracks) in FIG. 1 as an example for description, including the following steps S202 to S208. Among them:

[0046] Step S202, detecting fatigue cracks at the fillet welds of the steel bridge and determining the propagation direction of the fatigue cracks.

[0047] Optionally, in some embodiments, image information of the fillet weld of a steel bridge may be collected and an image detection algorithm may be used to identify fatigue cracks in the fillet weld of a steel bridge and their propagation directions.

[0048] Alternatively, in some other embodiments, the penetrant may be applied or sprayed on the surface of the steel bridge fillet weld. The penetrant is allowed to penetrate into the open defects on the surface of the steel bridge fillet weld by utilizing the wetting ability and capillary phenomenon of the liquid. Then, the steel bridge fillet weld is applied with a developer, and an image of the steel bridge fillet weld after the developer is applied is collected. Image recognition processing is performed based on the collected image of the steel bridge fillet weld to determine the fatigue cracks in the steel bridge fillet weld and their extension direction. Thus, penetration testing for fatigue cracks is achieved.

[0049] Alternatively, in other embodiments, ultrasonic waves may be emitted to the fillet weld of the steel bridge, and the fatigue crack position and its propagation direction in the fillet weld of the steel bridge may be calculated based on the ultrasonic data received and returned from the fillet weld of the steel bridge.

[0050] Step S204: applying pre-tension on both sides of the fatigue crack, wherein the pre-tension is used to make the gap opened by the fatigue crack reach a preset size.

[0051] Among them, pre-tension can be used to characterize the external force applied to open the crack before crack repair.

[0052] For example, the working parameters of the special force-applying tool can be initialized and configured in advance according to the preset size required by the user. According to the location of the fatigue crack and its extension direction, the area on both sides of the fatigue crack that can be used to apply pre-tension is determined. The special force-applying tool after initialization is used to apply pre-tension on both sides of the fatigue crack so that the gap opened at the fatigue crack reaches a preset size. Since the pre-tension can change the stress state of the steel bridge structure, the tensile stress amplitude at the fatigue crack can be reduced or even eliminated.

[0053] Step S206, under the operating condition of maintaining the pre-tension, the fatigue crack is planed along the extension direction of the fatigue crack to obtain the planed steel bridge fillet weld.

[0054] For example, under the operating condition of maintaining pre-tension, carbon arc gouging, mechanical gouging, flame cutting, chemical treatment, laser cutting and the like can be used to gouge the fatigue cracks at the fillet weld along the extension direction of the fatigue cracks, thereby facilitating better flow and filling of the welding material into the weld during subsequent welding.

[0055] Step S208, under the operating condition of maintaining the pre-tension, the planed steel bridge fillet weld is thermally repaired using welding materials.

[0056] Among them, the steel strength grade and quality grade of the welding material match those of the steel bridge fillet weld.

[0057] Steel strength grades can be used to reflect the tensile strength and bearing capacity of steel bridges.

[0058] The quality grade can be used to reflect the impact toughness and cold bending performance of steel bridges at different temperatures, which is an important indicator to measure the performance of steel bridges in harsh environments or stress conditions.

[0059] For example, the steel strength grade and quality grade of the steel bridge and the metal material that can be used for welding can be queried from the material data stored in the local database or the Internet. When the steel strength grade and quality grade of the metal material and the steel strength grade and quality grade of the steel bridge meet the following conditions: the steel strength grade and quality grade of the two are equal or the difference between the steel strength grade and quality grade of the two does not exceed the preset threshold, the currently compared metal material can be used as the welding material matching the steel bridge. Under the operating condition of maintaining the pre-tension, the welding material is welded to the planed groove in the planed steel bridge fillet weld according to the thermal repair methods such as heating repair method, stretching repair method, repair agent repair method and welding repair method, so as to achieve thermal repair of fatigue cracks in the fillet weld.

[0060] The above-mentioned thermal repair method for fatigue cracks in steel bridge corner welds determines the expansion direction of fatigue cracks by detecting fatigue cracks at steel bridge corner welds; applies pre-tension on both sides of the fatigue crack, and the pre-tension is used to make the opening gap of the fatigue crack reach a preset size; under the operating condition of maintaining the pre-tension, the fatigue crack is planed along the expansion direction of the fatigue crack to obtain the planed steel bridge corner weld; the corresponding welding material is matched according to the steel strength grade and quality grade of the steel bridge corner weld; under the operating condition of maintaining the pre-tension, the planed steel bridge corner weld is thermally repaired with welding materials, which can greatly reduce the fatigue stress amplitude of the service state of the repaired steel bridge corner weld, and fundamentally eliminate the possibility of fatigue cracking again at the original fatigue crack and its vicinity on the diaphragm corner weld, thereby achieving the purpose of repairing fatigue cracks.

[0061] In an exemplary embodiment, the preset size may be 2 mm (millimeter).

[0062] Exemplarily, in this embodiment, pre-tension can be applied on both sides of the fatigue crack so that the gap at the heel of the fatigue crack is greater than 2 mm, and the pre-tension applied at this time needs to meet the condition of not exceeding the metal yield strength of the steel bridge.

[0063] In this embodiment, by applying a pre-tension that does not exceed the metal yield strength of the steel bridge, cracking or plastic deformation at the corner weld due to the application of pre-tension can be avoided. By applying pre-tension, the gap at the heel of the fatigue crack is made larger than 2 mm, which is beneficial to improving the welding quality during the subsequent thermal repair of the fatigue crack.

[0064] In an exemplary embodiment, the above step S210 may also be implemented in the following manner:

[0065] Under the operating condition of maintaining pre-tension, the welding materials are welded at the fillet weld of the planed steel bridge using a preset linear energy.

[0066] Among them, line energy can refer to the energy input by the welding heat source to the weld per unit length during the welding process, usually in joules / cm (J / cm) or joules / millimeter (J / mm), also known as heat input. It is an important welding process parameter because it directly affects the quality and mechanical properties of the welded joint.

[0067] The calculation formula for line energy is: Q=IU / V, where Q represents line energy (kJ / cm), I is welding current (A), U is arc voltage (V), and V is welding speed (cm / min).

[0068] In this embodiment, a thermal repair method is used in which the welding material is welded to the planed steel bridge corner weld using a preset linear energy while maintaining the pre-tension. This can take advantage of the fact that the linear energy can precisely control the welding temperature and time, thereby improving the operational safety and welding quality of the thermal repair method.

[0069] In an exemplary embodiment, the energy threshold of the preset linear energy does not exceed 15 kJ / cm.

[0070] For example, in this embodiment, the welding material may be welded at the fatigue crack using a line energy with an energy threshold not exceeding 15 kJ / cm (kilojoules / cm).

[0071] In this embodiment, since the energy threshold of the preset energy does not exceed 15 kJ / cm, the effect of reducing the residual tensile stress generated by welding can be achieved.

[0072] In an exemplary embodiment, after executing step S210, the following steps may also be included:

[0073] Under the operating condition of maintaining pre-tension, the fillet welds of the steel bridge after heat repair are ground smooth.

[0074] For example, after the thermal repair of fatigue cracks in the fillet weld is completed and the pre-tensioning operation condition is maintained, the thermally repaired fillet weld of the steel bridge can be polished smooth to ensure a smooth transition between the welding material and the two ends of the fillet weld, thereby reducing stress concentration.

[0075] In this embodiment, by polishing the heat-repaired steel bridge corner weld smoothly after the fatigue crack of the corner weld is repaired, the stress at the steel bridge corner weld can be reduced and fatigue cracks can be avoided in the subsequent steel bridge corner weld.

[0076] In an exemplary embodiment, before grinding the thermally repaired fillet weld of a steel bridge to be smooth, the following steps may also be included:

[0077] Ultrasonic flaw detection is performed on the corner welds of the steel bridge after thermal repair to obtain defect detection results of the corner welds of the steel bridge after thermal repair; and the defect detection results are determined to be free of defects.

[0078] Among them, the defect detection results can be used to indicate whether there are cracks in the corner welds of steel bridges after thermal repair, whether there are areas where welding materials and steel bridge corner welds are not fused, whether there are slag inclusions and other defects.

[0079] For example, ultrasonic waves can be emitted to the fillet weld of a steel bridge after thermal repair, and ultrasonic echo data reflected from the fillet weld of the steel bridge after thermal repair is received. The ultrasonic echo data is processed using a preset defect detection algorithm to obtain a defect detection result of the fillet weld of the steel bridge after thermal repair. When it is determined that the defect detection result is defect-free, the operation of grinding the fillet weld of the steel bridge after thermal repair to make it smooth is performed.

[0080] Optionally, in other embodiments, when the defect detection result indicates that a defect exists, such as cracks, lack of fusion or slag inclusion, the thermal repair operation steps from step S202 to step S210 may be repeated.

[0081] In this embodiment, by performing ultrasonic flaw detection before grinding the steel bridge fillet weld after thermal repair, the welding quality of the thermal repair can be guaranteed, thereby avoiding the subsequent cracks in the steel bridge fillet weld.

[0082] In an exemplary embodiment, after the above step S202, the following may also be included:

[0083] A temporary crack arrest hole is drilled at the tip of the fatigue crack, and the temporary crack arrest hole covers the tip.

[0084] Among them, the temporary crack arrest hole can be used to characterize a hole temporarily drilled at its tip (i.e., the end) to block the propagation of fatigue cracks. After subsequent thermal repair, the hole will not be retained and needs to be sealed.

[0085] For example, Figure 3 As shown, after the position of the crack 110 in the fillet weld of the steel bridge and its extension direction are determined, the tip position of the end of the crack 110 can be located, and a temporary crack stop hole 310 is drilled at the tip position. The temporary crack stop hole 310 completely covers the tip position of the crack 110. After the position of the crack 120 in the fillet weld of the steel bridge and its extension direction are determined, the tip position of the end of the crack 120 can be located, and a temporary crack stop hole 310 is drilled at the tip position. The temporary crack stop hole 320 completely covers the tip position of the crack 120.

[0086] Alternatively, if Figure 4As shown, after drilling the temporary crack stop hole 310, a pre-tension F1 can be applied on both sides of the crack 110 to make the gap opened by the crack 110 larger than 2 mm. After drilling the temporary crack stop hole 320, a pre-tension F2 can be applied on both sides of the crack 120 to make the gap opened by the crack 120 larger than 2 mm.

[0087] In this embodiment, by drilling a temporary crack-stop hole at the tip of the fatigue crack, the effect of blocking the expansion of the fatigue crack can be achieved.

[0088] In an exemplary embodiment, the temporary crack-stop hole may have a diameter of 10 mm (millimeter).

[0089] In this embodiment, by using a crack stop hole with a hole diameter of 10 mm, the stress concentration at the crack tip can be eliminated, the stress level in the non-crack area of ​​the steel bridge fillet weld is increased, and the overall stress condition of the steel bridge fillet weld is improved.

[0090] In an exemplary embodiment, the above step S206 may further include:

[0091] Under the operating condition of maintaining the pre-tension, the fatigue crack is air-planed along the propagation direction of the fatigue crack to form an air-planing groove with a width of 4-8mm at the steel bridge fillet weld, thereby obtaining the steel bridge fillet weld after planing.

[0092] For example, the width of the gouging groove can be determined based on the width of the fatigue crack at the fillet weld of the steel bridge. Figure 5 As shown, under the operating condition of maintaining pre-tension, along Figure 4 The crack 110 is expanded in the direction of the crack 110, and the crack 110 is gouged to form a gouging groove 510 with a width t1 of 4-8 mm at the fillet weld of the steel bridge, so as to completely gouge the crack 110. The end of the gouging groove 510 is connected to the temporary crack stop hole 310.

[0093] Under the operating condition of maintaining pre-tension, Figure 4 The crack 120 is expanded in the direction of the crack 120, and the crack 120 is gouged to form a gouging groove 520 with a width t2 of 4-8 mm at the fillet weld of the steel bridge, so as to completely gouge the crack 120. The end of the gouging groove 520 is connected to the temporary crack stop hole 320.

[0094] Thus, the fillet weld of the steel bridge is obtained after planing.

[0095] In this embodiment, by completely removing fatigue cracks while maintaining pre-tension, it is possible to facilitate subsequent thermal repair of the planed steel bridge fillet welds, thereby improving the welding quality during the subsequent thermal repair process.

[0096] In an exemplary embodiment, after step S210, the following operations may also be performed:

[0097] Release the pre-tension.

[0098] For example, after the fatigue cracks of the fillet weld are thermally repaired, the pre-tension applied to the fillet weld of a steel bridge may be released.

[0099] Optionally, in some embodiments, after the thermal repair of the fatigue crack of the fillet weld is completed, the thermally repaired fillet weld of the steel bridge can be subjected to ultrasonic testing. When the defect detection result obtained by the ultrasonic testing is defect-free, the thermally repaired fillet weld of the steel bridge is polished to be smooth. After the thermally repaired fillet weld of the steel bridge is polished to be smooth, the pre-tension at the fillet weld of the steel bridge is released.

[0100] In this embodiment, by releasing the pre-tension on both sides of the fillet weld after the fatigue crack is thermally repaired, fatigue cracks can be avoided in subsequent fillet welds of steel bridges.

[0101] In an exemplary embodiment, Figure 6 As shown, a method for thermally repairing fatigue cracks of a steel bridge diaphragm is also provided, comprising the following steps S602 to S616. Among them:

[0102] Step S602, detecting fatigue cracks at the fillet welds of the steel bridge and determining the propagation direction of the fatigue cracks.

[0103] For example, fatigue cracks in the fillet welds of steel bridges and their propagation direction and the position of the propagation tip can be determined by directly capturing images of the fillet welds of steel bridges, or by applying or spraying penetrant and developer on the fillet welds of steel bridges and then capturing images, or by emitting ultrasonic waves to the steel bridge.

[0104] Step S604, drilling a temporary crack-stop hole at the tip position of the fatigue crack, wherein the temporary crack-stop hole covers the tip position.

[0105] For example, a temporary crack arrest hole with a diameter of 25 mm may be drilled at the tip of the fatigue crack, and the temporary crack arrest hole needs to completely cover the propagation tip of the fatigue crack.

[0106] Step S606: applying pre-tension on both sides of the fatigue crack, wherein the pre-tension is used to make the gap opened by the fatigue crack reach a preset size.

[0107] For example, pre-tension can be applied on both sides of the fatigue crack so that the gap between the ends of the fatigue crack is greater than 2 mm. The pre-tension does not exceed the metal yield strength of the steel bridge to avoid plastic deformation of the fillet weld of the steel bridge.

[0108] Step S608, under the operating condition of maintaining the pre-tension, the fatigue crack is air-planed along the expansion direction of the fatigue crack to form an air-planing groove with a width of 4-8 mm at the steel bridge fillet weld, thereby obtaining the planed steel bridge fillet weld.

[0109] Exemplarily, under the operating condition of maintaining the pre-tension applied in step S606, the fatigue cracks at the steel bridge corner weld can be completely removed along the expansion direction of the fatigue crack by air planing, and an air planing groove with a width of 4-8 mm can be formed at the steel bridge corner weld to obtain the planed steel bridge corner weld.

[0110] Step S610, obtaining corresponding welding materials according to the steel strength grade and quality grade of the steel bridge, and welding the welding materials to the fillet weld of the planed steel bridge using a preset linear energy while maintaining the pre-tensioning operation condition.

[0111] For example, a preset line energy of no more than 15 kJ / cm can be used to weld welding materials that match the steel strength grade and quality grade of the steel bridge at the fillet weld of the planed steel bridge, that is, at the gouging groove, to minimize the residual tensile stress generated by welding. At this time, the temporary crack arrest hole is also filled with welding materials.

[0112] Step S612, performing ultrasonic flaw detection on the steel bridge fillet weld after thermal repair to obtain defect detection results of the steel bridge fillet weld after thermal repair.

[0113] Exemplarily, ultrasonic waves can be emitted to the corner welds of the steel bridge after thermal repair, and ultrasonic flaw detection can be performed based on the ultrasonic echo data returned from the corner welds of the steel bridge after thermal repair to detect whether there are defects such as lack of fusion, cracks or slag inclusions in the corner welds of the steel bridge after thermal repair.

[0114] Step S614, when it is determined that the defect detection result is defect-free, the corner weld of the steel bridge after thermal repair is polished to be smooth while maintaining the pre-tensioning operation condition.

[0115] For example, when it is determined that the defect detection result is defect-free, the corner weld of the steel bridge after thermal repair can be polished smooth to ensure a smooth transition between the welding material and the two ends of the gouging groove welding to reduce stress concentration.

[0116] Step S616, releasing the pre-tension.

[0117] Exemplarily, after the above steps S606 to S614 are executed, the pre-tension applied to the corner weld of the steel bridge can be released.

[0118] like Figure 7As shown, by adopting the thermal repair method provided in this embodiment, since the fillet weld of the steel bridge is polished smooth after repair, the structural stress concentration effect at the fillet weld of the steel bridge is equivalent to that before repair, so the fatigue strength at the fillet weld of the steel bridge at this time only depends on the strength grade and quality grade of the steel material, that is, only depends on the strength grade and quality grade of the steel material of the welding material. The strength grade and quality grade of the steel material of the welding material match the steel bridge. Therefore, fatigue cracks can be avoided from occurring again at the fillet weld between the diaphragm 106 and the U-shaped rib 104 and at the fillet weld between the bridge deck 102 and the diaphragm 106.

[0119] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0120] Those skilled in the art will understand that the structures shown in the drawings of the present application specification are merely block diagrams of partial structures related to the present application scheme, and do not constitute a limitation on the computer device to which the present application scheme is applied. The specific computer device may include more or fewer components than those shown in the drawings, or combine certain components, or have a different arrangement of components.

[0121] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, an artificial intelligence (AI) processor, etc., but are not limited to this.

[0122] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0123] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for thermal repair of fatigue cracks in fillet welds of steel bridges, characterized in that: The method comprises: Detect fatigue cracks at fillet welds of steel bridges and determine the propagation direction of the fatigue cracks; Applying pre-tension on both sides of the fatigue crack, wherein the pre-tension is used to make the opening gap of the fatigue crack reach a preset size; Under the operating condition of maintaining the pre-tension, planing the fatigue crack along the extension direction of the fatigue crack to obtain the planed steel bridge fillet weld; Under the operating condition of maintaining the pre-tension, the planed steel bridge fillet weld is thermally repaired using welding materials, and the steel strength grade and quality grade of the welding materials match the steel bridge fillet weld.

2. The method according to claim 1, characterized in that The pre-tensioning force is used to make the opening gap of the fatigue crack heel end larger than 2 mm, and the pre-tensioning force does not exceed the metal yield strength of the steel bridge.

3. The method according to claim 1, characterized in that The method of thermally repairing the planed steel bridge fillet weld using welding materials under the operating condition of maintaining the pre-tensioning force comprises: Under the operating condition of maintaining the pre-tension, the welding material is welded at the fillet weld of the planed steel bridge using a preset linear energy.

4. The method according to claim 3, characterized in that The energy threshold of the preset linear energy does not exceed 15 kJ / cm.

5. The method according to claim 1, characterized in that After the planed steel bridge fillet weld is thermally repaired using welding materials under the operating condition of maintaining the pre-tension, the method further comprises: Under the operating condition of maintaining the pre-tension, the fillet weld of the steel bridge after thermal repair is polished to be smooth.

6. The method according to claim 5, characterized in that Before the hot-repaired steel bridge fillet weld is polished to be smooth under the operating condition of maintaining the pre-tension, the method further comprises: Performing ultrasonic flaw detection on the thermally repaired steel bridge fillet weld to obtain defect detection results of the thermally repaired steel bridge fillet weld; Determine that the defect detection result is no defect.

7. The method according to claim 1, characterized in that After detecting the fatigue cracks at the fillet welds of the steel bridge and determining the extension direction of the fatigue cracks, the method further includes: A temporary crack arrest hole is drilled at the tip position of the fatigue crack, and the temporary crack arrest hole covers the tip position.

8. The method according to claim 7, characterized in that The aperture of the temporary crack-stopping hole is 10 mm.

9. The method according to claim 1, characterized in that: The method of planing the fatigue crack along the extension direction of the fatigue crack under the operating condition of maintaining the pre-tension to obtain the planed steel bridge fillet weld comprises: Under the operating condition of maintaining the pre-tension, the fatigue crack is air-planed along the expansion direction of the fatigue crack to form an air-planing groove with a width of 4-8 mm at the steel bridge fillet weld, thereby obtaining the planed steel bridge fillet weld.

10. The method according to any one of claims 1 to 9, characterized in that After the planed steel bridge fillet weld is thermally repaired using the welding material under the operating condition of maintaining the pre-tension, the method further comprises: The pre-tensioning force is released.

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