Method for reinforcing steel structure through prestress fatigue of local additive and subtractive Fe-SMA component

Abstract

The invention discloses a method for pre-stress fatigue reinforcement of a steel structure through a local additive and subtractive Fe-SMA component, firstly, the position, needing to be reinforced, of the steel structure is subjected to surface treatment, then the Fe-SMA component is installed, and the Fe-SMA component comprises a Fe-SMA component and additive parts which are arranged at the two ends of the component and used for being connected with the surface of the steel structure or an anchoring assembly in a matched mode. The Fe-SMA components can be pre-stretched to reach preset strain, and active prestress is applied to the to-be-reinforced structure in a thermal excitation mode by utilizing the shape memory effect of the Fe-SMA materials. And the novel intelligent material Fe-SMA is used, so that the fatigue performance of the structure is improved. And meanwhile, the shape memory effect of Fe-SMA can be utilized, prestress can be applied to the to-be-reinforced structure in a thermal excitation mode, and the safety of the to-be-reinforced structure is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building structure fatigue reinforcement, in particular to a method for locally increasing and decreasing Fe-SMA component prestressed fatigue reinforcement of a steel structure. BACKGROUND

[0002] In recent years, with the technical iteration of various industrial and civil buildings, structures and other engineering structures, the fatigue failure problem of steel structures under cyclic dynamic loads (such as wind load, wave load, etc.) has attracted more and more attention from domestic and foreign experts and scholars. Steel structures cannot meet the normal use requirements after fatigue failure, and there is a great safety hazard.

[0003] In view of the fatigue failure problem of existing steel structures, domestic and foreign experts and scholars have proposed various reinforcement technologies, the commonly used ones mainly include steel plate bonding reinforcement method, fiber belt bonding reinforcement method, prestressed reinforcement method, etc., each method has its own advantages and disadvantages and applicable occasions.

[0004] Iron-based shape memory alloy (Fe-SMA) is an intelligent material with stable mechanical properties, excellent recovery performance, high efficiency and high cost performance. Its high fatigue resistance and shape memory effect make it have significant advantages in structure reinforcement and maintenance. SUMMARY

[0005] The purpose of the present application is to provide a method for locally increasing and decreasing Fe-SMA component prestressed fatigue reinforcement of a steel structure in view of the fatigue failure problem of steel structures under long-term cyclic dynamic loads, such as wind load, wave load, etc.

[0006] To achieve the above purpose, the technical solution adopted by the present application is:

[0007] The method for locally increasing and decreasing Fe-SMA component prestressed fatigue reinforcement of a steel structure performs surface treatment on the position of the steel structure that needs to be reinforced, and then installs the Fe-SMA component. The Fe-SMA component includes Fe-SMA elements and additive parts at both ends of the elements for adaptive connection with the surface of the steel structure or the anchoring assembly. The Fe-SMA component is pre-stretched to achieve a predetermined strain. The shape memory effect of Fe-SMA material is used to apply active prestress to the structure to be reinforced by means of thermal excitation.

[0008] The Fe-SMA component is a Fe-SMA plate component. The Fe-SMA plate component comprises a Fe-SMA plate as the Fe-SMA element, and the Fe-SMA plate has additive parts at both ends as additive filling plates; the surfaces of the additive filling plates can be attached to the geometric feature surfaces of the actual structure to be reinforced. The additive filling plates are directly printed on the Fe-SMA by additive manufacturing. In this embodiment, the Fe-SMA plate component is attached to the structure to be reinforced in the form of adhesion.

[0009] The Fe-SMA component is a Fe-SMA bar component. The Fe-SMA bar component comprises a Fe-SMA bar as the Fe-SMA element, and the Fe-SMA bar has additive parts at both ends as additive expansion sections for adapting to the connection of the anchoring assembly. The additive expansion sections are printed on the Fe-SMA by additive manufacturing, so that their diameters are larger than those of the original Fe-SMA bars, so that the Fe-SMA bar component is anchored to the steel structure to be reinforced.

[0010] The anchoring assembly comprises an anchor and a threaded anchoring sleeve, and the additive expansion section has external threads that are adapted to the internal threads of the threaded anchoring sleeve.

[0011] The method for locally adding and subtracting Fe-SMA components to prestress and fatigue-reinforce a steel structure according to the present application specifically comprises the following steps:

[0012] S1, preparing a Fe-SMA component: printing additive parts on both ends of a Fe-SMA element as a base material to form additive parts;

[0013] S2, surface treatment of the additive parts and the positions of the steel structure to be reinforced;

[0014] S3, fixing the Fe-SMA component to the positions of the steel structure to be reinforced;

[0015] S4, thermal excitation of the excitation area of the Fe-SMA element to generate shrinkage stress (i.e., recovery stress) inside the Fe-SMA element, thereby achieving prestress reinforcement;

[0016] S5, covering the surface of the positions of the steel structure to be reinforced with a corrosion-resistant layer.

[0017] When the Fe-SMA component is a Fe-SMA plate component:

[0018] After printing the additive filling plates on the Fe-SMA plate in step S1, the Fe-SMA base material is pre-stretched to a set strain, and then unloaded to allow the Fe-SMA to freely shrink to a residual strain.

[0019] In step S2, the surface near the fatigue damage of the steel structure to be reinforced is polished to form a bonding area, and the surface of the additive filling plate is polished for bonding with the bonding area.

[0020] In step S3, the structural adhesive is evenly applied to the bonding area to form a bonding layer, and then the Fe-SMA component is bonded to the steel structure to be reinforced.

[0021] In step S4, after the bonding layer is completely cured, the set Fe-SMA part without additive printing (activation area) is thermally activated, at which time the shrinkage stress (i.e. recovery stress) is generated inside the Fe-SMA, thereby achieving prestressed reinforcement. Moreover, only the set activation area of the Fe-SMA is thermally activated, which is beneficial to reduce the attenuation of the recovery stress of the Fe-SMA caused by the melting phenomenon of the bonding layer outside the activation area.

[0022] In step S5, the anticorrosion layer is formed by evenly applying anticorrosive paint to the entire reinforced area.

[0023] Preferably, in step S2, the additive manufacturing process should be placed before the pre-tensioning step of the Fe-SMA component, otherwise the additive manufacturing process is equivalent to thermal activation of the pre-tensioned Fe-SMA in advance, which seriously affects the prestress application to the reinforced area.

[0024] Preferably, in step S1, the Fe-SMA used as the additive manufacturing substrate should be fixed to ensure that the Fe-SMA does not deform due to heat input during the printing process. After the additive manufacturing is completed, the steel plate should be cooled to room temperature before the fixing measures are removed.

[0025] Preferably, in step S1, before printing, the space for applying the fixing measures should be considered, and at the same time, an oil-based pen is used to mark the actual design size of the reinforced component on the plate to control the printing range within the design range. After the fixing measures are removed at the end of printing, the excess part on the device should be cut according to the design.

[0026] Preferably, in step S1, when printing the additive filling plate, a layered stacking printing method should be used, that is, after each layer is printed, the next layer is printed after natural cooling for a period of time. This printing method is particularly suitable for the case where the Fe-SMA substrate is too thin, so as to avoid large deformation of the substrate due to heat input during the printing process.

[0027] Preferably, in step S1, the Fe-SMA in the printed Fe-SMA component should be pre-tensioned, and a specific assembly part should be designed to fit the surface of the additive filling plate, which facilitates the clamping and loading of the Fe-SMA component by the testing machine.

[0028] Preferably, in step S2, before the surface treatment anti-corrosion layer, use an oil pen to mark the range of the polishing area on the structure to be reinforced, which facilitates the purposeful and targeted polishing process.

[0029] Preferably, in step S2, after determining the polishing area, use an angle grinder and install a polishing disc to polish the adhesive surface of the additive filling plate and the steel structure to be reinforced until the surfaces of the two are polished to a metallic luster. Then, use 220 grit sandpaper to polish the adhesive surfaces of the two for one minute each to increase the roughness of the adhesive surface, which facilitates the adhesion of the adhesive layer.

[0030] Preferably, in step S2, after polishing is completed, use compressed air to blow off the powder and particles generated on the surface of the structure to be reinforced during the polishing process to ensure that the adhesive area is clean and clean, which facilitates the adhesion of the adhesive layer.

[0031] Preferably, in step S2, after polishing is completed, use an oil pen to accurately mark the specific adhesive area of the reinforcing member again.

[0032] Preferably, in step S3, control the temperature of the prepared structural adhesive to be between 10°C and 35°C. When the temperature is lower than 10°C, uniformly heat the structural adhesive, and when the temperature is higher than 35°C, physically cool the structural adhesive, which is beneficial to maintain the chemical activity of the structural adhesive, improve its flowability and adhesion performance, and improve the construction efficiency.

[0033] Preferably, in step S3, use a spatula to evenly apply the structural adhesive to the adhesive surface of the steel structure to be reinforced and the Fe-SMA member, and place a steel ball with a diameter of 1-2 mm at the edge of the adhesive layer of the steel structure to be reinforced to control the thickness of the adhesive layer, and then control the performance of the adhesive layer. During the bonding process, the Fe-SMA member should be continuously pressed until the adhesive layer cannot be further compressed. Clean the excess structural adhesive that is squeezed out. This is beneficial to the uniform distribution of the adhesive layer and ensures the adhesion effect of the adhesive layer and improves the adhesion quality.

[0034] Preferably, in step S3, the structural adhesive should be cured for at least 7 days, which is beneficial to the complete strength of the adhesive layer.

[0035] When the Fe-SMA member is an Fe-SMA bar member:

[0036] In step S1, the additive is printed on the Fe-SMA bar by additive manufacturing, and the additive expansion section is formed at both ends of the Fe-SMA bar. Further, the Fe-SMA base material is pre-stretched to a set strain, and then unloaded, allowing the Fe-SMA to freely shrink to a residual strain. Then, the surface of the additive expansion section is machined to form an external thread section, which is adapted to the internal threaded hole of the anchor.

[0037] In step S2, the surface treatment refers to determining the anchoring area on both sides of the fatigue crack on the steel structure, and polishing the anchoring area on the steel structure to form a to-be-pasted area, and then polishing the bottom plate of the machined anchor for pasting with the to-be-pasted area.

[0038] In step S3, the to-be-pasted area of the anchor bottom plate is uniformly coated with structural adhesive, and then the to-be-pasted area corresponding to the anchoring area of the steel structure is uniformly pressed against the anchor to fix the anchor in the specified area. Then, the Fe-SMA bar member is inserted through the anchor hole, and the threaded anchoring sleeve is screwed with the additive diameter expansion section.

[0039] In step S4, the pre-stress is applied. After the Fe-SMA bar member is assembled with the anchor, the Fe-SMA member is heated to the designed excitation temperature by using power supply or flame gun to heat excite the Fe-SMA member in the specified area, so that the shrinkage stress (i.e. recovery stress) is generated in the Fe-SMA member, thereby realizing pre-stress reinforcement.

[0040] In step S5, the corrosion protection layer is uniformly coated on the entire reinforcement area.

[0041] Preferably, in step S1, the additive manufacturing process must be placed before the Fe-SMA member pre-tensioning step, so as to avoid the Fe-SMA member from failing to reach the specified pre-tightening force after heat excitation.

[0042] Preferably, in step S2, according to the width, position and direction of the crack, the reinforcement area and the pasting area of the entire Fe-SMA member on both sides of the steel structure to be reinforced are selected and marked with an oily pen.

[0043] Preferably, in step S2, the line connecting the center points of the two hole drilling areas should be approximately perpendicular to the crack, and the width should be as close to the length of the crack as possible.

[0044] Preferably, in step S2, the to-be-pasted areas of the structure to be reinforced and the anchor are polished. After polishing, compressed air is used to blow off the powder generated on the surface during the polishing process.

[0045] Preferably, in step S3, the anchor is fixed to the steel structure to be reinforced by pasting, and the two ends of the Fe-SMA bar member are inserted through the holes of the two anchors. At this time, the threaded section of the outer surface of the additive diameter expansion section at both ends should be exposed to the outside of the two anchors. Then, the threaded anchoring sleeve is screwed with the threaded section of the outer surface of the additive diameter expansion section. After screwing, the sleeve is just pressed against the outer side of the anchoring plate, so that the pre-stress can be applied subsequently.

[0046] Preferably, in step S4, the Fe-SMA bar member excitation area is heat excited by using power supply or flame gun.

[0047] The beneficial effects of this invention are:

[0048] The Fe-SMA plate component described in this invention makes the fatigue strengthening technology of bonded steel plates no longer limited to planar surfaces, but applicable to fatigue strengthening of various complex surfaces, thus expanding the scope of application of this technology.

[0049] The Fe-SMA plate component described in this invention can be customized with geometric feature surfaces according to different crack directions, thereby achieving adaptive bonding of different crack directions under complex surfaces.

[0050] The Fe-SMA reinforcing member described in this invention utilizes the shape memory effect of Fe-SMA material, eliminating the need for traditional jack tensioning methods. Instead, prestress is applied through thermal activation, making the operation convenient and improving construction efficiency.

[0051] The method described in this invention, which involves machining threads in the additive expansion section of the Fe-SMA reinforcing member and anchoring them with threaded anchors, avoids the significant reduction in material fatigue performance caused by machining threads on the original reinforcing material, thus improving the safety of the threaded anchoring method.

[0052] The use of Fe-SMA, a novel smart material, has improved the fatigue performance of structures. Furthermore, the shape memory effect of Fe-SMA allows for the application of prestress to the structure to be strengthened through thermal excitation, significantly enhancing the safety of the structure. Attached Figure Description

[0053] The accompanying drawings provided herein are used to further explain the invention. The drawings, embodiments, and descriptions of the invention are for illustrative purposes only and are not exhaustive examples of the invention's application, nor do they constitute an undue limitation of the invention. In the drawings:

[0054] Figure 1 This is a construction process flow diagram of a prestressed fatigue-strengthened steel structure with Fe-SMA plate / reinforcement members, as described in this invention.

[0055] Figure 2 This is a schematic diagram of the Fe-SMA plate component described in this invention.

[0056] Figure 3 This is a schematic diagram of the Fe-SMA reinforcing member described in this invention.

[0057] Figure 4 This is a schematic diagram of the orthogonal irregular bridge deck to be reinforced according to the present invention.

[0058] Figure 5 This is a schematic diagram of the Fe-SMA plate in the additive manufacturing process described in this invention.

[0059] Figure 6 An assembly part capable of adhering to the surface of the additive filling plate according to the present application.

[0060] Figure 7 A schematic view of an anchorage device according to the present application.

[0061] Figure 8 A schematic view of the reinforcing mode of the Fe-SMA plate member and Fe-SMA bar member according to the present application.

[0062] In the figure, 1—Fe-SMA plate; 2—additive filling plate; 3—unprinted section; 4—Fe-SMA bar; 5—additive expansion section; 6—threaded anchoring sleeve; 7—threaded section; 8—orthotropic steel bridge deck; 9—fatigue failure crack; 10—butt weld crack; 11—additive manufacturing machine tool; 12—pad plate; 13—welding point; 14—Fe-SMA expansion area; 15—cutting line; 16—assembly part; 17—bottom plate; 18—rib plate; 19—anchoring plate. DETAILED DESCRIPTION

[0063] The following description is in connection with the illustrative Figures 1-7 The principles and features of the present application are described, the examples are used only to explain the present application, and are not used to limit the scope of the present application, but only represent some embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0064] The present application is described in more detail in the following paragraphs with reference to the accompanying drawings, so that the advantages and features of the present application are more apparent. It should be noted that the drawings are very simplified and use non-precise proportions to clearly show the structure of the components of the embodiments of the present application, only for the purpose of facilitating and clearly assisting the description of the embodiments of the present application. The same reference signs are used to represent the same parts.

[0065] Example 1

[0066] The specific embodiment of the Fe-SMA plate member is explained taking the cracking of the butt weld 9 of the longitudinal rib in the orthotropic steel bridge deck 8 (hereinafter referred to as steel bridge deck 8) as an example.

[0067] As shown in the figure, the method comprises the following steps: Figure 1

[0068] S1, surface treatment;

[0069] S2, preparing reinforcing member;

[0070] S3, member fixation;

[0071] ​S4, prestress is applied;

[0072] S5, anticorrosion layer is covered.

[0073] As shown in Figure 2 Fe-SMA plate member is composed of two parts, additive filling plate 2 and Fe-SMA plate 1. Additive filling plate 2 is attached to the two end surfaces of Fe-SMA plate 1 by additive manufacturing, and the unprinted section 3 in the middle of Fe-SMA plate 1 corresponds to the actual fatigue failure area that needs to be prestressed and fatigue reinforced.

[0074] In step S1:

[0075] Before polishing the surface decoration layer, anticorrosion layer and the like near the fatigue damage crack 9 of the steel bridge deck plate 8, an oil pen should be used to mark the range of the polishing area on the steel bridge deck plate 8. The polishing area should include the main area of fatigue damage on the steel bridge deck plate 8, and the polishing area should be polished in a targeted range according to the size information of the designed reinforcing member, so as to form the area to be pasted. After determining the polishing area, the polishing surface of the additive filling plate 2 and the steel bridge deck plate 8 is polished using an angle grinder and a polishing disc until the surfaces of the two are polished to a metallic luster. It should be noted that the polishing disc should not be used for polishing to avoid damaging the original structure and forming new fatigue damage sources. Then, the 220 mesh sandpaper is used to polish the two areas to be pasted for one minute to increase the roughness of the polishing surface and ensure the adhesion effect of the adhesive layer.

[0076] After polishing, the powder particles generated on the surface of the steel bridge deck plate 8 during the polishing process are blown off using compressed air, and the cleanliness of the area to be pasted is ensured by observation. Then, the oil pen is used again to accurately mark the area to be pasted of the specific reinforcing member. At this point, the surface treatment is completed.

[0077] In step S2:

[0078] The additive manufacturing process must be placed before the pre-tensioning step of the Fe-SMA plate 1, otherwise the heat input during the additive manufacturing process will cause the pre-tensioned Fe-SMA plate member to recover, and the residual deformation will be greatly reduced. At this time, the excitation area of the Fe-SMA plate member is heated again after pasting, and the prestress generated will be greatly reduced.

[0079] The additive filling plate is printed on the Fe-SMA plate 1 by additive manufacturing. As shown in Figure 5As shown, based on the space requirement of the fixing of the plate, the Fe-SMA plate 1 should consider reserving space for applying fixing measures before printing, and at the same time, using an oil pen to mark the planar size of the actual designed Fe-SMA component on the plate, so as to control the printing range to fall within the design range. After removing the fixing measures, the excess part on the device should be cut according to the design.

[0080] Specifically, the Fe-SMA sheet is fixed on the base plate 12, and then placed on the additive manufacturing machine tool 11 to print the additive filling plate through additive manufacturing technology. The Fe-SMA sheet has a cutting line 15, and the area outside the cutting line 15 is an Fe-SMA expansion area 14, which is used to fix the periphery of the Fe-SMA piece by taking fixing measures, such as spot welding, bolt anchoring, etc., as shown. Figure 5 After printing, cutting along the cutting line 15 obtains the Fe-SMA plate component.

[0081] At the same time, if necessary, the Fe-SMA plate 1 can be printed layer by layer, and after each layer is printed, the Fe-SMA plate 1 is cooled for a period of time before printing the next layer, so as to fully ensure that the heat input in the additive manufacturing process will not cause the Fe-SMA plate 1 to produce out-of-plane deformation. After the additive manufacturing is completed, the steel plate should be cooled to room temperature, and then the fixing measures should be removed.

[0082] As shown, Figure 6 A special assembly part 16 is used to enable the testing machine to clamp and load the Fe-SMA component, pre-stretch the Fe-SMA plate component until a set strain is reached, and then unload the load to allow the Fe-SMA plate component to freely shrink. At this point, the preparation of the Fe-SMA plate component is completed.

[0083] In step S3:

[0084] The structural adhesive can improve the activity of chemical reaction, improve its flowability and bonding performance, and be easy to apply and operate, so as to improve the construction efficiency, when the temperature of the structural adhesive is kept in the range of 10-35℃. Therefore, the structural adhesive is proportioned, and the temperature of the structural adhesive is measured by using a temperature gun before gluing, to monitor whether the temperature of the structural adhesive is in the suitable construction temperature range. If the temperature of the structural adhesive is lower than 10℃, the structural adhesive should be uniformly heated by using an infrared heater, and the temperature of the structural adhesive should be measured by using a temperature gun at regular intervals during the heating process to avoid overheating; if the temperature of the structural adhesive is higher than 35℃, the temperature of the structural adhesive should be reduced by using compressed air blowing, and the temperature of the structural adhesive should be continuously monitored until it is reduced to the suitable construction temperature.

[0085] The structural adhesive is applied to the bonding surfaces of both the steel bridge deck 8 and the Fe-SMA component using a spatula, and the adhesive layer is as uniform and full as possible. At the same time, a steel ball with a diameter of 1-2 mm is placed at the edge of the adhesive layer of the steel bridge deck 8 to control the thickness of the adhesive layer and thus the performance of the adhesive layer. When the two are bonded, a roller or rubber hammer or other tool should be used to continuously press the Fe-SMA component, and the pressure should be gradually and uniformly applied from the center of the Fe-SMA component outward to ensure that the bonding surfaces are in full contact and that the structural adhesive is uniformly distributed in the bonding area. After the glue oozes out of the gap, clean the excess structural adhesive. At this point, the component is fixed.

[0086] In step S4:

[0087] After the adhesive layer is completely cured, the set Fe-SMA plate component is heated and excited using a hot air gun at the designed thermal excitation temperature. At this time, the Fe-SMA plate component generates a shrinkage stress (i.e., a recovery stress), thereby achieving the prestressed reinforcement of the steel bridge deck 8. It should be noted that during the thermal excitation process, due to the heat transfer phenomenon of the plate, the adhesive layer will melt, and the melting of the adhesive layer will cause the loss of the constraint of the Fe-SMA, thereby causing the attenuation of the recovery stress of the Fe-SMA due to thermal excitation. Therefore, in order to minimize the attenuation of the recovery stress of the Fe-SMA caused by the melting of the adhesive layer outside the excitation area, the heat source should be as close to the set excitation area as possible. After thermal excitation is complete, the system is naturally cooled to room temperature. At this point, the prestress application is complete.

[0088] In step S5, the corrosion protection layer is uniformly applied to the entire reinforcement area. At this point, the corrosion protection layer is applied.

[0089] At this point, the Fe-SMA plate component is fixed, as shown in Figure 8 .

[0090] Example 2

[0091] The specific implementation of the Fe-SMA bar component is explained by taking the cracking of the longitudinal rib butt weld crack 10 in the common orthotropic steel bridge deck 8 as an example.

[0092] As shown in Figure 3 , the Fe-SMA bar component is composed of three parts, namely the Fe-SMA bar 4, the additive expansion section 5, and the threaded anchoring sleeve 6. The additive expansion section 5 is attached to the Fe-SMA bar 4 by additive manufacturing, and then the outer surface of the additive expansion section 5 is machined to form a threaded section 7. The inner surface of the threaded anchoring sleeve 6 is also threaded and can be screwed with the additive expansion section 5.

[0093] The anchoring assembly includes an anchor and a threaded anchoring sleeve 6. The anchor style is as shown in Figure 7As shown, the anchor includes an anchor plate 19, two bottom plates 17 and two rib plates 18. Two rib plates 18 are arranged in parallel on the anchor plate 19, and the anchor plate 19 is provided with a circular hole with the same diameter as the additive diameter expansion section of the Fe-SMA bar member. One bottom plate 17 is connected perpendicularly to the two rib plates 18 and the anchor plate 19. The other bottom plate 17 is connected to the anchor plate 19 at an angle, which is determined according to the specific conditions of the actual steel bridge deck 8, and mainly to ensure that the other bottom plate 17 can be attached to the steel bridge deck 8. According to the actual working conditions and load capacity requirements, the anchor fixed to the steel bridge deck is machined.

[0094] In step S1:

[0095] According to the pre-designed reinforcement scheme, the reinforcement area of the entire Fe-SMA member is preliminarily selected on both sides of the steel bridge deck according to the width, position and direction of the crack, and the reinforcement area is marked with an oil pen.

[0096] In the reinforcement area, select the area to be pasted, and the line connecting the center points of the two areas to be pasted should be approximately perpendicular to the crack, and the width should be as close to the length of the crack as possible. After selecting the area to be pasted, it should be marked with an oil pen.

[0097] After determining the area to be pasted, polish the marked position. After polishing, use compressed air to blow off the powder particles generated during the polishing process, and ensure that the reinforcement area is clean and clean through observation. At this point, the surface treatment is completed.

[0098] In step S2:

[0099] Like the Fe-SMA plate member of Example 1, the additive manufacturing process must be placed before the pre-tensioning step of the Fe-SMA member to avoid the Fe-SMA being unable to reach the set pre-tightening force after being heated.

[0100] Clamp the Fe-SMA bar 4 on the numerical control rotary table, and print while rotating the Fe-SMA bar 4 by additive manufacturing to expand the diameter of the Fe-SMA bar and form the additive diameter expansion section 5.

[0101] After additive manufacturing, use the bar clamp of the universal testing machine to clamp the additive diameter expansion section of the Fe-SMA bar member 14, and pre-tension it until the set strain is reached, and then remove the load to allow the Fe-SMA to freely shrink.

[0102] In step S3:

[0103] First, fix the anchor, align the anchor bottom plate 17 with the area to be pasted on the surface of the steel bridge, and fully attach the two, and then uniformly apply pressure to paste and fix.

[0104] Fe-SMA tendon member without threaded anchorage sleeve 6 is passed through the holes of two anchors, at this time the threaded section 7 on the outer surface of the additive diameter expansion section 5 should be just exposed to the outside of the two anchoring plates 19, then the threaded anchorage sleeve 6 is screwed with the threaded section 7 on the outer surface of the additive diameter expansion section 5, after screwing, the threaded anchorage sleeve 6 is good against the outside of the anchoring plate 19. At this point, the Fe-SMA tendon member is fixed, as shown in Figure 8 .

[0105] Steps S4 and S5 are the same as in Embodiment 1.

[0106] According to the above, those skilled in the art can easily implement the present application according to the drawings and the above description.

[0107] The above description is not intended to limit the present application in any form, and any equivalent changes, modifications and evolutions made by those skilled in the art within the scope of the technical solutions of the present application using the technical content disclosed above are equivalent embodiments of the present application; at the same time, any equivalent changes, modifications and evolutions made according to the essential technology of the present application to the above embodiments are still within the protection scope of the technical solutions of the present application.

Claims

1. A method of prestressed fatigue reinforcement of steel structures by local additive and subtractive Fe-SMA components, characterized by, The surface of the position to be reinforced of the steel structure to be reinforced is treated, and then the Fe-SMA component is installed, the Fe-SMA component comprising a Fe-SMA element and additive parts at both ends of the Fe-SMA element for adapting and connecting with the surface of the steel structure or an anchoring assembly.

2. The method of prestressing and fatigue strengthening of steel structures with local additive and subtractive Fe-SMA components according to claim 1, characterized by the fact that, The Fe-SMA component is a Fe-SMA plate component, the Fe-SMA element of the Fe-SMA plate component is a Fe-SMA plate, and the additive parts at both ends of the Fe-SMA plate are additive filling plates; the surface of the additive filling plates can be attached to the geometric feature surface of the actual structure to be reinforced.

3. The method of prestressing and fatigue strengthening of steel structures with local additive and subtractive Fe-SMA components according to claim 1, characterized by the fact that, The Fe-SMA component is a Fe-SMA bar component, the Fe-SMA element of the Fe-SMA bar component is a Fe-SMA bar, and the additive parts at both ends of the Fe-SMA bar are additive expansion sections for adapting and connecting with the anchoring assembly.

4. The method of prestressing and fatigue strengthening a steel structure with a local additive-subtractive Fe-SMA member according to claim 3, characterized in that, The anchoring assembly comprises an anchor and a threaded anchoring sleeve, and correspondingly, the additive expansion sections have external threads that adapt to the internal threads of the threaded anchoring sleeve.

5. The method of locally pre-stressing a fatigue-strengthened steel structure with a Fe-SMA component according to any one of claims 1 to 4, characterized in that The method comprises the following steps: S1, preparing a Fe-SMA component: taking a Fe-SMA piece as a base material, and printing additive parts at both ends of the Fe-SMA piece to form additive parts; S2, treating the surfaces of the additive parts and the position to be reinforced of the steel structure to be reinforced; S3, fixing the Fe-SMA component at the position to be reinforced of the steel structure to be reinforced; S4, thermally exciting the exciting area of the Fe-SMA piece to generate shrinkage stress inside the Fe-SMA piece; S5, covering the surface of the position to be reinforced of the steel structure to be reinforced with a corrosion-resistant layer.

6. The method of locally pre-stressing a fatigue-strengthened steel structure with a Fe-SMA component according to claim 5, characterized in that When the Fe-SMA component is a Fe-SMA plate component: In the step S1, after the additive filling plates are printed on the Fe-SMA piece, the Fe-SMA piece is pre-stretched to a set strain, and then unloaded to allow the Fe-SMA piece to freely shrink to a residual strain; In the step S2, the surface near the fatigue damage of the steel structure to be reinforced is polished to form a to-be-pasted area, and the surface of the additive filling plate is polished for pasting with the to-be-pasted area; In the step S3, structural glue is uniformly applied to the to-be-pasted area to form a cementation layer, and then the Fe-SMA component is pasted to the steel structure to be reinforced; In the step S4, after the cementation layer is completely cured, the exciting area of the Fe-SMA piece is thermally excited to generate shrinkage stress inside the Fe-SMA piece; In the step S5, corrosion-resistant paint is applied to the reinforced position to form a corrosion-resistant layer.

7. The method of locally pre-stressing a fatigue-stiffening steel structure with a Fe-SMA component according to claim 6, characterized in that In the step S3, the temperature range of the structural glue is controlled to be between 10℃ and 35℃, the structural glue is heated when the temperature is lower than 10℃, and the structural glue is physically cooled when the temperature is higher than 35℃.

8. The method of locally pre-stressing a fatigue-strengthened steel structure with a Fe-SMA component according to claim 5, characterized in that When the Fe-SMA component is a Fe-SMA bar component: In the step S1, additive parts are printed on the Fe-SMA bar to form additive expansion sections at both ends of the Fe-SMA bar, and then the Fe-SMA bar is pre-stretched to a set strain, and then unloaded to allow the Fe-SMA bar to freely shrink to a residual strain; In step S2, anchorage zones are determined on both sides of the fatigue crack on the steel structure to be reinforced, and the anchorage zones of the steel structure to be reinforced are ground to form a bonding area. Then, the bonding surface of the machined anchor is ground for bonding with the bonding area. In step S3, firstly, the two anchors are placed in the anchorage area of ​​the steel structure to be reinforced, and structural adhesive is used to attach and fix the anchors in the designated area; then, the Fe-SMA reinforcement member with the expanded diameter is passed through the holes of the two anchors, and then two threaded anchor sleeves are screwed and fixed to the expanded diameter sections at both ends of the Fe-SMA reinforcement member. In step S4, after the Fe-SMA reinforcement member and the anchoring assembly are assembled, the activation area of ​​the Fe-SMA member is thermally activated to generate shrinkage stress inside the Fe-SMA. In step S5, an anti-corrosion coating is applied to the reinforced location to form an anti-corrosion layer.

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