Device and construction method for self-prestress shear-resistant reinforcement of concrete beam based on Fe-SMA battens

Abstract

The invention provides a device and a construction method for self-prestress shear-resistant reinforcement of a concrete beam based on Fe-SMA battens. The method comprises the following steps: S1, determining the type of the concrete beam; s2, a to-be-reinforced area is pretreated; s3, reinforcing parts are installed; s4, the Fe-SMA batten is excited for the first time; and S5, carrying out secondary excitation on the Fe-SMA batten. The reinforcing device and the construction mode can be suitable for different types of concrete beams, the device is convenient to install, prestress application is convenient and efficient, rapid active prestress reinforcing is achieved by optimizing the temperature rising means of energization excitation, the tedious tensioning process is omitted, and the temperature rising time and the excitation temperature are optimized to achieve controllable damage of the adhesive layer. The invention provides a complete set of method for secondary excitation of the Fe-SMA batten, so that the service life of the reinforced concrete beam is further prolonged; reinforcing members do not need to be replaced, and maintenance cost is reduced; and the method is suitable for long-term service performance recovery and improvement of engineering structures.

Description

Technical Field

[0001] The present invention relates to the technical field of structural reinforcement, in particular to a device and a construction method for reinforcing concrete beams based on Fe-SMA strips for self-prestressed shear resistance. Background Art

[0002] As service life continues to increase, many concrete structures are experiencing varying degrees of accumulated damage and durability degradation, necessitating urgent reinforcement and repair. my country is transitioning from a "primary focus on new construction" approach to a "combined construction and maintenance" approach. Concrete beams are one of the most commonly used structural forms, and their primary defects are persistent deflection at mid-span and cracks in the beam body. The widespread presence of diagonal cracks at beam ends weakens the shear bearing capacity of the diagonal sections. Unchecked, these cracks will severely impact the structural service life and driving safety.

[0003] Shear reinforcement of concrete beams aims to enhance their crack resistance and bearing capacity, enabling them to withstand greater loads and external forces, thereby ensuring structural safety. Currently, non-prestressed shear reinforcement methods are the most widely used, such as increasing the cross-section, embedding reinforcement materials, bonding steel, and bonding fiber-reinforced plastic (FRP). However, these non-prestressed reinforcement methods suffer from the prominent challenge of stress hysteresis, meaning the reinforcement material must undergo further structural deformation before it can begin to function. In recent years, prestressed shear reinforcement methods, such as prestressed FRP sheets and prestressed steel wire ropes, have garnered extensive attention and research. However, existing prestressed shear reinforcement technologies suffer from three drawbacks. First, the application of prestress often requires on-site mechanical equipment and limited working space, making the overall construction process relatively time-consuming and labor-intensive. Second, when using a U-shaped wrapping method (one of the most widely used methods), prestress friction losses at corners are significant. Finally, the short length and large quantity of reinforcement materials used in shear reinforcement lead to high anchor costs, impacting their economic viability.

[0004] In recent years, researchers at home and abroad have been continuously experimenting with integrating iron-based shape memory alloys (Fe-SMAs) with new or existing concrete structures to improve their load-bearing capacity and ductility. The shape memory effect, which enables Fe-SMAs to return to their predetermined shape after heating and cooling, is essentially the result of a reversible phase transformation within Fe-SMA, namely a martensitic phase transformation. If the Fe-SMA is constrained while experiencing the shape memory effect, it can generate its own restorative stress. These properties of SMAs offer the potential for introducing convenient and efficient prestressing in the shear reinforcement of concrete structural components. Because this prestressing does not require mechanical tensioning, it is referred to as self-prestressing technology. Fe-SMA-based self-prestressing technology offers the advantages of external prestressing reinforcement, including high material utilization, excellent reinforcement effectiveness, and the ability to effectively increase the cracking load and stiffness of the structure without the need for large-scale tensioning equipment, making it a promising application prospect.

[0005] Currently, Fe-SMA-based self-prestressed concrete beams are prone to prestress loss due to material relaxation over time. A comprehensive method for secondary excitation has not yet been developed, limiting their application in multi-stage post-disaster recovery. Existing technologies lack a comprehensive method for secondary excitation. Summary of the Invention

[0006] In response to the limitations of the above-mentioned prior art, the present invention provides a device and construction method for self-prestressed shear reinforcement of concrete beams based on Fe-SMA slats, which realizes temperature-controlled welding and multiple excitation methods in civil engineering, and is suitable for improving and restoring the long-term service performance of engineering structures; according to changes in the structural state, multiple excitations can be achieved without replacing materials, thereby improving its adaptability and economy.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: A construction method for self-prestressed shear-resistant reinforced concrete beams based on Fe-SMA slats comprises the following steps: S1. Determine the type of concrete beam: Observe the cross-sectional shape of the concrete beam, select the appropriate Fe-SMA strips according to its cross-sectional shape, and design an effective reinforcement method; S2. Pre-treat the area to be reinforced: Grind the surface of the concrete beam to be reinforced to remove dust; roughen the area where the Fe-SMA strips are to be attached, and further open at least two sets of positioning holes on the concrete beam; clean the surface of the concrete beam before proceeding to the next step; S3. Install reinforcements: Assemble the Fe-SMA slats and anchor end plates, fix the water-cooling circulation system near the Fe-SMA slat welding area, weld multiple Fe-SMA slats between two adjacent anchor end plates, apply adhesive to the roughened area on the concrete beam surface, apply adhesive to the inside of the welded Fe-SMA slats and anchor end plates, and before the adhesive solidifies, adhere the Fe-SMA slats and anchor end plates to the concrete beam surface, squeeze them tightly, and scrape off excess adhesive from both sides of the Fe-SMA slats; align the through holes of the anchor end plates with the positioning holes, and secure the anchor end plates to the concrete beam using anchor bolts and nuts. S4. Initial excitation of the Fe-SMA strips: After the steel adhesive reaches the final setting time, the Fe-SMA excitation system is used to excite the Fe-SMA strips with a large current. At the same time, an infrared thermal imaging camera is used to record the real-time temperature of the Fe-SMA strips. The power is immediately turned off when the Fe-SMA strips reach the required excitation temperature. S5. Secondary excitation of Fe-SMA strips: Regularly inspect the appearance and cracks of concrete beams, focusing on observing the concrete surface cracks in the area where the Fe-SMA strips are attached. During inspection, use crack comparison cards for rapid on-site assessment, and use ultrasonic or infrared thermal imagers to assist in detecting hidden cracks. Then, use a crack width meter or optical microscope to perform multi-point measurements at the widest point of the crack. The starting conditions for secondary excitation are as follows: For ordinary concrete beams, the crack width exceeds 0.3 mm in dry indoor conditions, 0.2 mm in humid and freeze-thaw conditions, and 0.1 mm in corrosive conditions. For prestressed concrete beams, the first and second level crack control requirements are when cracks appear on the concrete surface; the third level crack control requirement is when the crack width exceeds 0.2mm in a Class I environment and exceeds 0.1mm in a Class II or higher corrosion environment; When the measured value exceeds the limit, the Fe-SMA secondary excitation is started, and the process is as follows: A high current is applied to the Fe-SMA strips for secondary excitation. The secondary excitation temperature is 20-50°C higher than the initial activation temperature. After a certain period of heat preservation, the strips are naturally cooled. After the Fe-SMA strips have completely cooled to room temperature, the crack width is re-measured. If the crack still has not closed within the limit, the excitation temperature is appropriately increased by 50°C and the secondary excitation operation is repeated until the crack width meets the limit. The entire process requires real-time temperature monitoring to avoid overheating and ensure that the performance of the Fe-SMA material is not damaged. If cracks still exceed the limit after multiple excitations, further evaluation of the structural safety is required.

[0008] Preferably, the types of the concrete beams include T-beams and I-beams, and the Fe-SMA strips applicable to the T-beams and I-beams are respectively configured to be U-shaped and straight strips.

[0009] Preferably, when the surface of the T-beam is polished in S2, the bottom surface thereof is polished into a rounded corner at a right angle, and the curvature radius of the U-shaped Fe-SMA strip at the bend is the same as the radius of the bottom corner of the concrete beam.

[0010] Preferably, the anchoring end plate is made of austenitic stainless steel having the same or similar alloy element composition as that of the Fe-SMA strip.

[0011] Preferably, the Fe-SMA strips are welded to the anchoring end plates by argon gas shielded welding, and the ends of the Fe-SMA strips are welded on three sides.

[0012] Preferably, the length of the anchoring end plate is adapted to the length of the required shear reinforcement section.

[0013] Preferably, the number of through holes on the anchoring end plate is set to be multiple, and the diameter of the through hole is slightly larger than the diameter of the anchor bolt; The position and quantity of each group of positioning holes are distributed in a one-to-one correspondence with the through holes on the anchor end plate; before applying steel adhesive to the anchor end plate and Fe-SMA plate, the applied surface is first polished.

[0014] Preferably, the water-cooling circulation system includes two copper heat exchange patches, each of which is provided with a serpentine channel, and the two ends of the serpentine channel are respectively connected to the water inlet and the water outlet, the water inlet and the water outlet are connected through a circulation pipe, and the circulation pipe is provided with a pressurized circulation pump and a refrigeration and cooling element. The two heat exchange patches are distributed near the welding area of ​​the Fe-SMA slats, and the space between the two heat exchange patches and the Fe-SMA slats is filled with thermal conductive silicone grease, so that the coolant can fully flow through the interior of the heat exchange patch to transfer the heat of the Fe-SMA slats.

[0015] Preferably, the Fe-SMA excitation system includes two excitation connectors and a high-current, low-voltage excitation device. The two excitation connectors are arranged on the Fe-SMA strip near the welding area, and the two excitation connectors are respectively connected to the high-current, low-voltage excitation device through wires, one of the excitation connectors is connected to the positive pole, and the other excitation connector is connected to the negative pole.

[0016] The present invention also provides a reinforcement device applied to the above-mentioned construction method of self-prestressed shear reinforcement of concrete beams based on Fe-SMA strips. The device for reinforcing concrete beams includes a reinforcement piece, and when reinforcing the T-beam, the reinforcement piece uses a U-shaped Fe-SMA strip perpendicular to the length direction of the T-beam.

[0017] The Fe-SMA self-prestressed reinforcement method adopted in the present invention has the following advantages: The reinforcement device and construction method of the present invention can be applied to different types of concrete beams. The device is easy to install, and prestressing is convenient and efficient. The heating means of the power-on excitation is optimized to achieve rapid active prestressing reinforcement, eliminating the tedious tensioning process, optimizing the heating time and the excitation temperature to achieve controllable damage to the adhesive layer. The complete method of secondary excitation of the Fe-SMA component provided by the present invention is used to extend the protection period of the concrete beam and improve the toughness; there is no need to replace the reinforcement parts, which reduces maintenance costs; and it is suitable for long-term service performance improvement and restoration of engineering structures.

[0018] By designing effective reinforcement methods based on the type of concrete beam and pre-treating the area to be reinforced, there is no friction loss at the corners after reinforcement; three-sided argon arc welding can greatly save the cost of prestressed anchors and significantly reduce the dependence on the bonding effect of the adhesive layer. Combined with circulating water cooling temperature control measures, it ensures that heat does not diffuse and does not affect the overall shape memory effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 Schematic diagram of the distribution of the reinforcement device for the I-beam provided in Example 1 of the present invention.

[0021] Figure 2 For the present invention Figure 1 A partial cross-sectional view of the device shown.

[0022] Figure 3 This is a three-dimensional diagram of the reinforcement device unit used in Example 1 of the present invention.

[0023] Figure 4 Schematic diagram of the distribution of the reinforcement device for the T-beam provided in Example 2 of the present invention.

[0024] Figure 5 For the present invention Figure 4 A partial cross-sectional view of the device shown.

[0025] Figure 6 This is a three-dimensional diagram of the reinforcement device unit used in Example 2 of the present invention.

[0026] Figure 7 This is the distribution diagram of the water cooling circulation system before excitation of the Fe-SMA slab in the present invention.

[0027] Figure 8It is a cross-sectional view of the heat exchange patch in the present invention.

[0028] In the figure: 1. Concrete beam; 2. Fe-SMA strip; 3. Anchor end plate; 4. Nut; 5. Anchor bolt; 6. Argon arc weld; 7. Steel glue; 8. Heat exchange patch; 9. Water inlet; 10. Water outlet; 11. Excitation joint; 12. Wire. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] like Figure 1-8 As shown, a construction method for self-prestressed shear-resistant reinforced concrete beams based on Fe-SMA slats includes the following steps: S1. Determine the type of concrete beam 1: Observe the cross-sectional shape of the concrete beam 1, select the appropriate Fe-SMA slats 2 based on the cross-sectional shape, and design an effective reinforcement method. Concrete beams 1 include T-beams and I-beams, and the Fe-SMA slats 2 suitable for T-beams and I-beams are set to U-shaped and straight strips, respectively.

[0031] S2. Pre-treat the area to be reinforced: Grind the surface of the concrete beam 1 to be reinforced to remove dust; roughen the area where the Fe-SMA strips 2 are to be attached, and further open at least two sets of positioning holes on the concrete beam 1; clean the surface of the concrete beam 1, such as by using a blower to blow strong air; then proceed to the next step; During surface grinding, the T-beam's bottom right angles are rounded, and the radius of curvature at the bend of the U-shaped Fe-SMA strip 2 is the same as the radius of the bottom corner of the concrete beam 1. The U-shaped Fe-SMA strip 2 tightly wraps around the concrete beam 1, evenly distributing the stress and generating restoring stress on the concrete beam 1, eliminating friction losses at the bottom corner of the beam.

[0032] S3. Install the reinforcement: fix the water-cooling circulation system near the welding area of ​​the Fe-SMA slat 2, cool it while welding, and combine the Fe-SMA slat 2 with the anchoring end plate 3. As an embodiment of the water-cooling circulation system provided in this application, it includes two copper heat exchange patches 8, which are provided with serpentine channels inside, and the two ends of the serpentine channels are respectively connected to the water inlet 9 and the water outlet 10. The water inlet 9 and the water outlet 10 are connected through a circulation pipe, and a pressurized circulation pump and a refrigeration and cooling element are provided on the circulation pipe. The two heat exchange patches 8 are distributed near the welding area of ​​the Fe-SMA slat 2, and the space between the Fe-SMA slat 2 is filled with thermal conductive silicone grease, so that the coolant can fully flow through the interior of the heat exchange patch 8 to transfer the heat of the Fe-SMA slat 2. The coolant is water or ethylene glycol solution, and the water inlet 9 and the water outlet 10 are connected to an external pressurized circulation device. The coolant at the water inlet 9 is cooled in the refrigeration and cooling element, and is re-pressurized and transported from the water inlet 9 to the heat exchange patch 8 to complete the circulation cooling and utilization of the coolant.

[0033] Specifically, a plurality of Fe-SMA strips 2 are welded between two adjacent anchor end plates 3, and steel adhesive 7 is applied to the roughened area on the surface of the concrete beam 1 (i.e., the location where the Fe-SMA strips 2 need to be pasted), and steel adhesive 7 is applied to the inner side of the welded Fe-SMA strips 2 and the anchor end plates 3. The steel adhesive 7 is a type with a higher glass transition temperature.

[0034] The anchoring end plate 3 is made of austenitic stainless steel having the same or similar alloy element composition as the Fe-SMA strip 2, which can avoid micro cracks occurring during welding of dissimilar steels and causing the welding area to become a weak link.

[0035] Argon gas shielded welding is adopted when welding the Fe-SMA strip 2 and the anchoring end plate 3, and welding is performed around three sides of the ends of the Fe-SMA strip 2.

[0036] Before the adhesive 7 solidifies, the Fe-SMA slats 2 and the anchoring end plates 3 are pasted on the surface of the concrete beam 1 and squeezed tightly. The excess adhesive 7 is scraped off from both sides of the Fe-SMA slats 2. The through holes of the anchoring end plates 3 are aligned with the positioning holes, and the anchoring end plates 3 are fixed to the concrete beam 1 with anchor bolts 5 and nuts 4. The length of the anchoring end plates 3 is adapted to the length of the required shear reinforcement section.

[0037] The number of through holes on the anchoring end plate 3 is set to be multiple, and the diameter of the through hole is slightly larger than the diameter of the anchor bolt; The location and number of each set of locating holes correspond one-to-one with the through holes on the anchor end plate 3. Before drilling the locating holes, determine the drill points and depths for each set of locating holes. The locating holes correspond to the mounting locations at both ends of the Fe-SMA strip 2. The drilling depth must be no less than the minimum embedment depth of the anchor bolts 5. The locating holes must thread properly with the anchor bolts 5, and the diameter of the anchor bolts 5 must be no less than M10.

[0038] During installation, the U-shaped Fe-SMA strips 2 are perpendicular to the length of the concrete beam 1. Straight Fe-SMA strips 2 can be arranged perpendicular to the length of the concrete beam 1 or tilted, meaning not completely perpendicular to the length of the concrete beam 1. The specific adjustment depends on the angle of the diagonal crack in the concrete beam 1. Straight Fe-SMA strips 2 are suitable not only for I-beams but also for other applications where the Fe-SMA strips 2 cannot be bent (such as inside a box beam). For I-beams, the upper edge of the anchor plate 3 is aligned with the lower flange of the concrete beam 1. Before applying adhesive to the anchor plate and Fe-SMA strips, the applied surface should be polished.

[0039] S4. Initial excitation of the Fe-SMA strips 2: After the adhesive 7 reaches the final setting time, the Fe-SMA excitation system is used to excite the Fe-SMA strips 2 with a large current. At the same time, an infrared thermal imaging camera is used to record the real-time temperature of the Fe-SMA strips 2. The power is immediately turned off when the Fe-SMA strips 2 reach the required excitation temperature. S5. Secondary excitation of Fe-SMA strips: After several years of reinforcement of concrete beams or after being subjected to extreme loads, if the width of concrete surface cracks in the area where Fe-SMA strips are bonded exceeds the national standard limit (such as the crack control standard for the normal serviceability limit state of flexural members in the "Code for Design of Concrete Structures" GB 50010-2010), the Fe-SMA secondary excitation process needs to be initiated. Regularly inspect the appearance and cracks of concrete beams, focusing on observing the concrete surface cracks in the area where Fe-SMA strips are bonded. During inspection, crack comparison cards are used for rapid on-site assessment, and ultrasonic or infrared thermal imagers are used to assist in the detection of hidden cracks. Then, a crack width meter or optical microscope is used to conduct multi-point measurements at the widest point of the crack. The initiation conditions of secondary excitation are as follows: For ordinary concrete beams, the crack width exceeds 0.3 mm in dry indoor conditions, 0.2 mm in humid and freeze-thaw conditions, and 0.1 mm in corrosive conditions. For prestressed concrete beams, the first and second level crack control requirements are when cracks appear on the concrete surface; the third level crack control requirement is when the crack width exceeds 0.2mm in a Class I environment and exceeds 0.1mm in a Class II or higher corrosion environment; When the measured value exceeds the limit, the Fe-SMA secondary excitation is initiated. If the crack width has returned to the threshold set by the national standard or below, the excitation is considered effective and the reinforcement process ends. If the crack width still exceeds the standard limit, the excitation temperature level needs to be increased and the power heating excitation operation is performed again. The "excitation-cooling-observation" process is repeated until the crack width is controlled within the target range. The process is as follows: A high current is applied to the Fe-SMA strip 2 for secondary excitation. The secondary excitation temperature is 20-50°C higher than the initial activation temperature. After a certain period of heat preservation, the strip is naturally cooled. After the Fe-SMA strip 2 has completely cooled to room temperature, the crack width is re-measured. If the crack still has not closed within the limit, the excitation temperature is appropriately increased by 50°C and the secondary excitation operation is repeated until the crack width meets the limit. The entire process requires real-time temperature monitoring to avoid overheating and ensure that the performance of the Fe-SMA material is not damaged. If cracks still exceed the limit after multiple excitations, further evaluation of the structural safety is required.

[0040] As an embodiment of the Fe-SMA excitation system provided in this application, it includes two excitation connectors 11 and a high-current, low-voltage excitation device. The two excitation connectors 11 are arranged on the Fe-SMA slats 2 near the welding area, and the two excitation connectors 11 are respectively connected to the high-current, low-voltage excitation device via wires 12, one of which is connected to the positive electrode, and the other is connected to the negative electrode. The self-prestressing force generated by the temperature-induced phase change in the present invention is essentially different from the traditional technical path of applying external force for overall tensioning. The power-on excitation uniformly heats the Fe-SMA by resistance heating. The shape recovery caused by the austenite phase transformation is constrained. The U-shaped Fe-SMA plate generates a recovery stress applied to the concrete beam, and there is no friction loss at the bottom corner of the beam.

[0041] The present invention also provides a reinforcement device for use in the above-mentioned construction method for self-prestressed shear reinforcement of concrete beams using Fe-SMA slats. The device for reinforcing concrete beams includes a reinforcement member, and when reinforcing a T-beam, the reinforcement member uses a U-shaped Fe-SMA slat perpendicular to the length direction of the T-beam. During installation, referring to the specific process of a construction method for self-prestressed shear reinforcement of concrete beams using Fe-SMA slats, the Fe-SMA slats 2 are easy to install and are basically the same as the non-prestressed bonded steel reinforcement process. However, the heating method of electrical excitation can achieve rapid active prestressing reinforcement, eliminating the tedious tensioning process. The short heating time (≤60s) and low excitation temperature (≤160°C) can ensure that damage to the adhesive layer is controllable.

[0042] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations to these embodiments may be made without departing from the principles and spirit of the present invention, and these changes and modifications still fall within the scope of protection of the present invention.

Claims

1. A construction method for self-prestressed shear-resistant reinforced concrete beams based on Fe-SMA slats, characterized in that: The following steps are involved: S1. Determine the type of concrete beam: Observe the cross-sectional shape of the concrete beam, select the appropriate Fe-SMA strips according to its cross-sectional shape, and design an effective reinforcement method; S2. Pre-treat the area to be reinforced: Grind the surface of the concrete beam to be reinforced to remove dust; roughen the area where the Fe-SMA strips are to be attached, and then open at least two sets of positioning holes on the concrete beam; clean the dust on the surface of the concrete beam, and then proceed to the next step; S3. Install reinforcements: Assemble the Fe-SMA slats and anchor end plates, fix the water-cooling circulation system near the Fe-SMA slat welding area, weld multiple Fe-SMA slats between two adjacent anchor end plates, apply adhesive to the roughened area on the concrete beam surface, apply adhesive to the inside of the welded Fe-SMA slats and anchor end plates, and before the adhesive solidifies, adhere the Fe-SMA slats and anchor end plates to the concrete beam surface, squeeze them tightly, and scrape off excess adhesive from both sides of the Fe-SMA slats; align the through holes of the anchor end plates with the positioning holes, and secure the anchor end plates to the concrete beam using anchor bolts and nuts. S4. Initial excitation of the Fe-SMA strips: After the steel adhesive reaches the final setting time, the Fe-SMA excitation system is used to excite the Fe-SMA strips with a large current. At the same time, an infrared thermal imaging camera is used to record the real-time temperature of the Fe-SMA strips. The power is immediately turned off when the Fe-SMA strips reach the required excitation temperature. S5. Secondary excitation of Fe-SMA strips: Regularly inspect the appearance and cracks of concrete beams, focusing on observing the concrete surface cracks in the area where the Fe-SMA strips are attached. During inspection, use crack comparison cards for rapid on-site assessment, and use ultrasonic or infrared thermal imagers to assist in detecting hidden cracks. Then, use a crack width meter or optical microscope to perform multi-point measurements at the widest point of the crack. The starting conditions for secondary excitation are as follows: For ordinary concrete beams, the crack width exceeds 0.3 mm in dry indoor conditions, 0.2 mm in humid and freeze-thaw conditions, and 0.1 mm in corrosive conditions. For prestressed concrete beams, the first and second level crack control requirements are when cracks appear on the concrete surface; the third level crack control requirement is when the crack width exceeds 0.2mm in a Class I environment and exceeds 0.1mm in a Class II or higher corrosion environment; When the measured value exceeds the limit, the Fe-SMA secondary excitation is started, and the process is as follows: A high current is applied to the Fe-SMA strips for secondary excitation. The secondary excitation temperature is 20-50°C higher than the initial activation temperature. After a certain period of heat preservation, the strips are naturally cooled. After the Fe-SMA strips have completely cooled to room temperature, the crack width is re-measured. If the crack still has not closed within the limit, the excitation temperature is appropriately increased by 50°C and the secondary excitation operation is repeated until the crack width meets the limit. The entire process requires real-time temperature monitoring to avoid overheating and ensure that the performance of the Fe-SMA material is not damaged. If cracks still exceed the limit after multiple excitations, further evaluation of the structural safety is required.

2. The construction method of Fe-SMA slat self-prestressed shear reinforcement concrete beam according to claim 1, characterized in that: The concrete beams include T-beams and I-beams, and the Fe-SMA strips suitable for the T-beams and I-beams are respectively configured to be U-shaped and straight strips.

3. The construction method of Fe-SMA slat self-prestressed shear reinforcement concrete beam according to claim 2, characterized in that: When the T-beam is surface-grinded in S2, its bottom surface is ground into a rounded corner at a right angle, and the curvature radius of the U-shaped Fe-SMA strip at the bend is the same as the radius of the bottom corner of the concrete beam.

4. The construction method of Fe-SMA slat self-prestressed shear reinforcement concrete beam according to claim 1, characterized in that: The anchoring end plate is made of austenitic stainless steel having the same or similar alloy element composition as that of the Fe-SMA strip.

5. The construction method of Fe-SMA slat self-prestressed shear reinforcement concrete beam according to claim 1, characterized in that: Argon gas shielded welding is adopted when the Fe-SMA strip is welded to the anchoring end plate, and three sides of the ends of the Fe-SMA strip are welded around the ends.

6. The construction method of Fe-SMA slat self-prestressed shear-resistant reinforced concrete beam according to claim 5, characterized in that: The length of the anchoring end plate is adapted to the length of the required shear reinforcement section.

7. The construction method of Fe-SMA slat self-prestressed shear-resistant reinforced concrete beam according to claim 1, characterized in that: The number of through holes on the anchoring end plate is set to be multiple, and the diameter of the through hole is slightly larger than the diameter of the anchor bolt; The position and quantity of each group of positioning holes are distributed in a one-to-one correspondence with the through holes on the anchor end plate; before applying steel adhesive to the anchor end plate and Fe-SMA plate, the applied surface is first polished.

8. The construction method of Fe-SMA slat self-prestressed shear-resistant reinforced concrete beam according to claim 1, characterized in that: The water-cooling circulation system includes two copper heat exchange patches, each of which has a serpentine channel inside, and the two ends of the serpentine channel are respectively connected to the water inlet and the water outlet. The water inlet and the water outlet are connected through a circulation pipe, and the circulation pipe is provided with a pressurized circulation pump and a refrigeration and cooling element. The two heat exchange patches are distributed near the welding area of ​​the Fe-SMA strips, and the space between the two heat exchange patches and the Fe-SMA strips is filled with thermal conductive silicone grease, so that the coolant can fully flow through the interior of the heat exchange patch to transfer the heat of the Fe-SMA strips.

9. The construction method of Fe-SMA slat self-prestressed shear-resistant reinforced concrete beam according to claim 1, characterized in that: The Fe-SMA excitation system includes two excitation connectors and a high-current, low-voltage excitation device. The two excitation connectors are arranged on the Fe-SMA strip near the welding area, and the two excitation connectors are respectively connected to the high-current, low-voltage excitation device through wires, one of the excitation connectors is connected to the positive pole, and the other excitation connector is connected to the negative pole.

10. A device for self-prestressed shear reinforcement of concrete beams based on Fe-SMA strips, applied to the construction method according to any one of claims 1 to 9, characterized in that: The device for reinforcing a concrete beam comprises a reinforcing member, and when reinforcing a T-beam, the reinforcing member uses a U-shaped Fe-SMA plate perpendicular to the length direction of the T-beam.

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