A method for constructing a large-span steel plate composite beam to solve bridge deck cracking in the negative bending moment zone.

Abstract

This invention discloses a large-span steel plate composite beam and its construction method for solving the problem of bridge deck cracking in the negative bending moment zone. The beam includes a steel main girder assembly, at least one bridge deck assembly in the negative bending moment zone, at least one bridge deck assembly in the positive bending moment zone, and at least one elastic bridge deck assembly. The bridge deck assembly in the negative bending moment zone includes a first concrete bridge deck, at least two symmetrically distributed first upper flanges, at least two symmetrically distributed first webs, and at least two symmetrically distributed first connectors. The first upper flanges are fixedly mounted on the first webs, and the first concrete bridge deck and the first upper flanges are connected by the first connectors. This invention uses iron-based shape memory alloy components to partially replace the supporting components in traditional large-span steel plate composite beams, which not only provides good support for the first concrete bridge deck but also applies prestress to it, thus conveniently solving the problem of bridge deck cracking in the negative bending moment zone of large-span steel plate composite beam bridges.

Description

Technical Field

[0001] This invention relates to the field of steel plate composite beam bridge technology, specifically to a large-span steel plate composite beam and its construction method for solving bridge deck cracking in the negative bending moment zone. Background Technology

[0002] Steel plate composite beam bridges are a traditional steel-concrete composite structure. Their main load-bearing components are made of steel, while the bridge deck is made of concrete slabs, cleverly combining the two materials. In the negative bending moment zone of continuous beams, the tensile stress on the concrete bridge deck, leading to cracking, is one of the main factors restricting the application of composite beams. Cracks in the concrete bridge deck in the negative bending moment zone reduce the stiffness of the composite beam; furthermore, cracking leads to corrosion of the reinforcing bars, studs, and steel beams, reducing the bridge's durability and affecting its service life.

[0003] To control bridge deck cracks in the negative bending moment zone, current methods include tensioning prestressed tendons, preloading, support displacement, and adjusting the concrete pouring sequence. When using the tensioning prestressing method, most of the applied prestress is borne by the steel beam, resulting in low prestressing efficiency. Furthermore, concrete bridge decks suffer from creep and shrinkage, while the prestressed steel strands experience relaxation, leading to significant prestress loss. When using the preloading method, counterweights are added in the positive bending moment zone. After the bridge deck in the negative bending moment zone is poured, the counterweights are removed, causing the beam to rebound and form prestress in the negative bending moment zone. This method is complex, as the amount and location of the counterweights cannot be precisely quantified, making it inconvenient to operate. When using the support displacement method, the bridge deck is poured by jacking up the central support, and the support then falls back to form prestress in the negative bending moment zone. This method requires jacking up the steel beam, is complex, and may result in uneven settlement of the supports later, requiring unloading of the prestress. These problems urgently need to be addressed. Therefore, a large-span steel plate composite beam and its construction method for solving the problem of bridge deck cracking in the negative bending moment zone are proposed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: how to solve the problem that existing large-span steel plate composite beams are inconvenient to control cracks on bridge decks in the negative bending moment zone, and to provide a large-span steel plate composite beam that solves the problem of bridge deck cracking in the negative bending moment zone, including a steel main beam assembly, at least one bridge deck assembly in the negative bending moment zone, at least one bridge deck assembly in the positive bending moment zone, and at least one elastic bridge deck assembly.

[0005] The negative bending moment zone bridge deck assembly includes a first concrete bridge deck, at least two symmetrically distributed first upper flanges, at least two symmetrically distributed first webs, and at least two symmetrically distributed first connectors. The first upper flanges are fixedly disposed on the first webs. The first concrete bridge deck and the first upper flanges are connected by the first connectors. The first upper flanges, the first webs, and the first connectors are all made of iron-based shape memory alloys.

[0006] The positive bending moment zone bridge deck assembly includes a second concrete bridge deck, and the elastic bridge deck assembly includes an elastic bridge deck, which is disposed between the first concrete bridge deck and the second concrete bridge deck. The elastic bridge deck is made of high-ductility concrete.

[0007] The steel main girder assembly includes at least two symmetrically distributed second upper flanges and at least two symmetrically distributed second webs. The elastic bridge deck and the second concrete bridge deck are both disposed on the second upper flanges. The second webs are connected to the second upper flanges. The first webs and the second webs are connected by a first fastener. The elastic bridge deck and the second upper flange are connected by a second fastener.

[0008] Preferably, the steel main beam assembly has multiple mounting holes inside for adjusting and installing the first fastener.

[0009] Preferably, the mounting hole is elliptical in shape.

[0010] Preferably, the first connector has multiple non-communicating grooves, and the top of each groove has an inward protrusion.

[0011] Preferably, the positive bending moment zone bridge deck assembly further includes at least two second connectors, and the second concrete bridge deck and the second upper flange are connected by the second connectors.

[0012] Preferably, the resilient bridge panel assembly further includes at least two third connectors, and the resilient bridge panel and the second upper flange are connected by the third connectors.

[0013] Preferably, the steel main beam assembly further includes at least two symmetrically distributed lower flanges, which are connected to the second web.

[0014] Preferably, the steel plate composite beam bridge further includes a supporting stiffening rib, which is disposed on the surface of the second web plate.

[0015] Preferably, the contact surfaces of the first web plate, the second web plate, the supporting stiffening rib, and the first fastener are all coated with an insulating coating.

[0016] This invention also provides a construction method for large-span steel plate composite beams that solves the problem of bridge deck cracking in the negative bending moment zone, comprising the following steps:

[0017] S1. Before construction, the steel main beam assembly, the bridge deck assembly in the positive bending moment zone, and the bridge deck assembly in the negative bending moment zone are prefabricated in sequence. When prefabricating the bridge deck assembly in the negative bending moment zone, the first upper flange, the first web, and the first connector are prefabricated and then welded to form an iron-based shape memory alloy component. The original length of the iron-based shape memory alloy component is L0. The iron-based shape memory alloy component is stretched to a length of L1 and fixed. After fixing, the first concrete bridge deck is poured. When the concrete strength of the first concrete bridge deck reaches 90%, the iron-based shape memory alloy component is released. At this time, the length of the iron-based shape memory alloy component is reduced to L2. The length of the iron-based shape memory alloy component L1 is greater than the length of the iron-based shape memory alloy component L2, which is greater than the length of the iron-based shape memory alloy component L0.

[0018] S2. During construction, steel main beam components are erected at the bridge site. After erection, bridge deck components in the positive bending moment zone are installed. After installation, bridge deck components in the negative bending moment zone are installed. During installation, the first web and the second web are connected by the first fastener, and the elastic bridge deck and the second upper flange are connected by the second fastener. After connection, the elastic bridge deck is poured.

[0019] S3. After construction, when cracks appear at the first concrete bridge deck during the operation of the large-span steel plate composite beam that addresses bridge deck cracking in the negative bending moment zone, and the crack width is greater than 2mm, loosen the first and second fasteners, connect the power supply to both ends of the first web to heat the iron-based shape memory alloy component, and cool it after the power supply is completed; after cooling, the length of the iron-based shape memory alloy component is shortened to L3, and the length of the iron-based shape memory alloy component L1 > the length of the iron-based shape memory alloy component L2 > the length of the iron-based shape memory alloy component L3 > the length of the iron-based shape memory alloy component L0.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. This invention uses iron-based shape memory alloy components to partially replace the support components in traditional large-span steel plate composite beams. This not only provides good support for the first concrete bridge deck but also applies prestress to the first concrete bridge deck, thereby conveniently solving the problem of bridge deck cracking in the negative bending moment zone of large-span steel plate composite beam bridges.

[0022] 2. By using specific construction steps, the present invention can apply prestress to the first concrete bridge deck in two stages, thereby facilitating the user to apply prestress to the first concrete bridge deck during the prefabrication of the steel main beam assembly, the bridge deck assembly in the positive bending moment zone, and the bridge deck assembly in the negative bending moment zone, or after the bridge is completed, according to the user's needs.

[0023] 3. By setting an elastic bridge deck, the present invention facilitates the reduction of stress transmission between the first concrete bridge deck and the second concrete bridge deck, thereby helping to reduce the tensile stress on the first concrete bridge deck.

[0024] 4. The present invention facilitates the stable connection of the first concrete bridge deck and the first upper flange through the shape of the first connector. After the two are connected, the first connector can also be used as a carrier for applying prestress. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the large-span steel plate composite beam provided by the present invention to solve the problem of bridge deck cracking in the negative bending moment zone.

[0026] Figure 2 for Figure 1 A structural schematic diagram of the bridge deck assembly in the negative bending moment zone is provided.

[0027] Figure 3 for Figure 2 Provided is a magnified view of part A.

[0028] Figure 4 for Figure 1 Provided partial structural diagram;

[0029] Figure 5 for Figure 4 Provided is a magnified view of section B.

[0030] Figure 6 for Figure 1 A structural schematic diagram of the provided steel main beam assembly;

[0031] Figure 7 for Figure 1 A structural schematic diagram showing the connection between the bridge deck assembly and the steel main beam assembly in the positive bending moment zone;

[0032] Figure 8 for Figure 1 A structural diagram showing the connection between the provided flexible bridge deck assembly and the steel main beam assembly;

[0033] Figure 9 for Figure 2 A side view of the first connector provided;

[0034] Figure 10 The flowchart illustrates the construction steps of a large-span steel plate composite beam construction method for solving bridge deck cracking in the negative bending moment zone, as provided by this invention.

[0035] The numbers in the image represent:

[0036] 1. Bridge deck assembly in negative bending moment zone; 11. First concrete bridge deck; 12. First upper flange; 13. Web; 14. First connector; 15. Insulating coating;

[0037] 2. Bridge deck assembly in the positive bending moment zone; 21. Second concrete bridge deck; 22. Second connector;

[0038] 3. Flexible bridge panel assembly; 31. Flexible bridge panel; 32. Third connector;

[0039] 4. Steel main beam assembly; 41. Second upper flange; 42. Second web; 43. Lower flange;

[0040] 5. Supporting stiffening ribs;

[0041] 6. Mounting holes;

[0042] 7. First fastener;

[0043] 8. Second fastener;

[0044] 9. Support. Detailed Implementation

[0045] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.

[0046] like Figure 1-9 As shown, the large-span steel plate composite beam for solving bridge deck cracking in the negative bending moment zone described in this embodiment includes a steel main beam assembly 4, at least one bridge deck assembly 1 in the negative bending moment zone, at least one bridge deck assembly 2 in the positive bending moment zone, and at least one elastic bridge deck assembly 3.

[0047] The negative bending moment zone bridge deck assembly 1 includes a first concrete bridge deck 11, at least two symmetrically distributed first upper flanges 12, at least two symmetrically distributed first webs 13, and at least two symmetrically distributed first connectors 14. The first upper flanges 12 are fixedly disposed on the first webs 13. The cross-sectional shape of the first upper flanges 12 and the first webs 13 after welding is T-shaped. The first concrete bridge deck 11 and the first upper flanges 12 are connected by the first connectors 14. The first upper flanges 12, the first webs 13, and the first connectors 14 are all made of iron-based shape memory alloy. The first upper flanges 12, the first webs 13, and the first connectors 14 are welded to form an iron-based shape memory alloy component. In this embodiment, by using iron-based shape memory alloy components to replace the support components in traditional large-span steel plate composite beams, not only can the first concrete bridge deck 11 be well supported, but also prestress can be applied to the first concrete bridge deck 11 through the iron-based shape memory alloy components.

[0048] The working process of using iron-based shape memory alloy components is mainly divided into three stages: First, the first upper flange 12, the first web plate 13 and the first connector 14 are welded to form an iron-based shape memory alloy component, and the original length of the iron-based shape memory alloy component is L0.

[0049] The iron-based shape memory alloy component is then stretched to length L1 and fixed. After fixing, the first concrete bridge deck 11 is poured.

[0050] Finally, when the concrete strength of the first concrete bridge deck 11 reaches 90%, the iron-based shape memory alloy component is released and its length is reduced to L2, wherein the length of the iron-based shape memory alloy component L1 is greater than the length of the iron-based shape memory alloy component L2 and the length of the iron-based shape memory alloy component L0.

[0051] The positive bending moment zone bridge deck assembly 2 includes a second concrete bridge deck 21, and the elastic bridge deck assembly 3 includes an elastic bridge deck 31. The elastic bridge deck 31 is disposed between the first concrete bridge deck 11 and the second concrete bridge deck 21. The elastic bridge deck 31 is made of high-ductility concrete. In this embodiment, the high-ductility concrete is a fiber-reinforced composite material with cement, quartz sand, etc. as the matrix, which has good deformation capacity. The strength grade of the high-ductility concrete is C50, and the equivalent bending toughness is ≥160kJ / m. 3 .

[0052] The steel main girder assembly 4 includes at least two symmetrically distributed second upper flanges 41 and at least two symmetrically distributed second webs 42. The elastic bridge deck 31 and the second concrete bridge deck 21 are both disposed on the second upper flanges 41. The second webs 42 are connected to the second upper flanges 41. The second concrete bridge deck 21, the elastic bridge deck 31, and the second upper flanges 41 are connected in pairs by shear studs. The first webs 13 and the second webs 42 are connected by first fasteners 7, and the elastic bridge deck 31 and the second upper flanges 41 are connected by second fasteners 8. (This embodiment...) When cracks appear at the first concrete bridge deck 11 during the operation of the long-span steel plate composite beam, the first fastener 7 and the second fastener 8 are loosened, and power is connected to both ends of the first web 13 to heat the iron-based shape memory alloy component. After the power is turned on, it is cooled. After cooling, the length of the iron-based shape memory alloy component is shortened to L3. This embodiment uses the iron-based shape memory alloy component to facilitate timely treatment of cracks at the first concrete bridge deck 11, thereby improving the overall practicality of the equipment and making it easier to use (in this embodiment, the first fastener 7 and the second fastener 8 are both fastening bolts used for connection).

[0053] More specifically, in this embodiment, both ends of the lower flange 43 of the steel main beam assembly 4 are provided with bases, and multiple equally spaced supports 9 are provided at the bottom of the bases. The span between the bases and supports 9 is M1; the span between supports 9 is M2; 0.15M1 and 0.15M2 are reserved on both sides of the supports 9 respectively (0.15M1 and 0.15M2 are the areas where the bridge deck of the large-span steel plate composite beam bridge is prone to cracking in the negative bending moment zone), and iron-based shape memory alloy components are installed at these locations. In this embodiment, by utilizing the characteristics of iron-based shape memory alloy components to partially replace the support components in the traditional large-span steel plate composite beam, it can not only provide good support for the first concrete bridge deck 11, but also apply prestress to the first concrete bridge deck 11, thereby conveniently solving the problem of bridge deck cracking in the negative bending moment zone of the large-span steel plate composite beam bridge.

[0054] After installation, the length of the iron-based shape memory alloy component is L2 = 0.15M1 + 0.15M2.

[0055] In this embodiment, the steel main beam assembly 4 has multiple mounting holes 6 inside for adjusting and installing the first fastener 7.

[0056] In this embodiment, the mounting hole 6 is elliptical in shape. By setting the elliptical mounting hole 6, movement space is provided for the deformation of the iron-based shape memory alloy component after it is energized.

[0057] In this embodiment, the first connector 14 has multiple non-communicating grooves, and the top of the grooves has an inward protrusion. Through the arrangement of the first connector 14, when the first concrete bridge deck 11 is poured, the concrete enters the interior of the grooves, thereby achieving a tight connection between the two different materials, the first connector 14 and the first concrete bridge deck 11, which is beneficial to extending the service life of the first concrete bridge deck 11 (in this embodiment, the depth of each groove is 10 cm, and the distance between the grooves is 15 cm).

[0058] In this embodiment, the positive bending moment zone bridge deck assembly 2 further includes at least two second connectors 22, and the second concrete bridge deck 21 and the second upper flange 41 are connected by the second connectors 22. The structure of the second connector 22 is the same as that of the first connector 14.

[0059] In this embodiment, the elastic bridge panel assembly 3 further includes at least two third connectors 32, and the elastic bridge panel 31 and the second upper flange 41 are connected by the third connectors 32. The structure of the third connectors 32 is the same as that of the first connectors 14.

[0060] In this embodiment, the steel main beam assembly 4 further includes at least two symmetrically distributed lower flanges 43, which are connected to the second web 42. The difference between the steel main beam assembly 4 and the normal steel-concrete composite beam is that the steel main beam assembly 4 removes a portion of the web originally attached to the second upper flange 41. By removing the attached web, it is not only convenient to reduce the overall weight of the equipment, but also convenient to install the negative bending moment bridge deck assembly 1 and subsequently apply prestress to it.

[0061] In this embodiment, the steel plate composite beam bridge also includes supporting stiffening ribs 5, which are disposed on the surface of the second web 42. The number of supporting stiffening ribs 5 is the same as the number of the second web 42. By providing supporting stiffening ribs 5, it is convenient to support the bridge deck assembly 1 in the negative bending moment zone.

[0062] In this embodiment, an insulating coating 15 is applied to the contact surfaces of the first web plate 13, the second web plate 42, the supporting stiffening rib 5, and the first fastener 7. The insulating coating 15 in this embodiment is a nano-level coating, and the coefficient of friction between the insulating coating 15 and the steel plates on the steel main beam assembly 4, the supporting stiffening rib 5, and the first fastener 7 is greater than 0.4. In this embodiment, the application of the insulating coating 15 prevents the iron-based shape memory alloy component from being affected by electricity, thus ensuring the normal use of the first web plate 13, the second web plate 42, the supporting stiffening rib 5, and the first fastener 7.

[0063] like Figure 10 As shown in the figure, this embodiment also provides a construction method for large-span steel plate composite beams that solves the problem of bridge deck cracking in the negative bending moment zone, including the following steps:

[0064] S1. Before construction, the steel main beam assembly 4, the positive bending moment zone bridge deck assembly 2, and the negative bending moment zone bridge deck assembly 1 are prefabricated in sequence. When prefabricating the negative bending moment zone bridge deck assembly 1, the first upper flange 12, the first web 13, and the first connector 14 are prefabricated and then welded to form an iron-based shape memory alloy component. The original length of the iron-based shape memory alloy component is L0. The iron-based shape memory alloy component is stretched to the length L1 and fixed. After fixing, the first concrete bridge deck 11 is poured. When the concrete strength of the first concrete bridge deck 11 reaches 90%, the iron-based shape memory alloy component is released. At this time, the length of the iron-based shape memory alloy component is reduced to L2. The length of the iron-based shape memory alloy component L1 is greater than the length of the iron-based shape memory alloy component L2, which is greater than the length of the iron-based shape memory alloy component L0.

[0065] S2. During construction, steel main beam assembly 4 is erected at the bridge site. After erection, bridge deck assembly 2 in the positive bending moment zone is installed. After installation, bridge deck assembly 1 in the negative bending moment zone is installed. During installation, the first web 13 and the second web 42 are connected by the first fastener 7, and the elastic bridge deck 31 and the second upper flange 41 are connected by the second fastener 8. After connection, the elastic bridge deck 31 is poured.

[0066] S3. After construction, when cracks appear at the first concrete bridge deck 11 and the crack width is greater than 2mm during the operation of the large-span steel plate composite beam that solves the problem of bridge deck cracking in the negative bending moment zone, loosen the first fastener 7 and the second fastener 8, connect the power supply to both ends of the first web 13 to heat the iron-based shape memory alloy component, and cool it after the power supply is completed; after cooling, the length of the iron-based shape memory alloy component is shortened to L3, and the length of the iron-based shape memory alloy component L1 is greater than the length of the iron-based shape memory alloy component L2, which is greater than the length of the iron-based shape memory alloy component L3, which is greater than the length of the iron-based shape memory alloy component L0.

[0067] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A large-span steel plate composite beam for solving bridge deck cracking in the negative bending moment zone, characterized in that, It includes a steel main girder assembly, at least one bridge deck assembly in the negative bending moment zone, at least one bridge deck assembly in the positive bending moment zone, and at least one elastic bridge deck assembly; The negative bending moment zone bridge deck assembly includes a first concrete bridge deck, at least two symmetrically distributed first upper flanges, at least two symmetrically distributed first webs, and at least two symmetrically distributed first connectors. The first upper flanges are fixedly disposed on the first webs. The first concrete bridge deck and the first upper flanges are connected by the first connectors. The first upper flanges, the first webs, and the first connectors are all made of iron-based shape memory alloys. The positive bending moment zone bridge deck assembly includes a second concrete bridge deck, and the elastic bridge deck assembly includes an elastic bridge deck, which is disposed between the first concrete bridge deck and the second concrete bridge deck. The elastic bridge deck is made of high-ductility concrete. The steel main girder assembly includes at least two symmetrically distributed second upper flanges and at least two symmetrically distributed second webs. The elastic bridge deck and the second concrete bridge deck are both disposed on the second upper flanges. The second webs are connected to the second upper flanges. The first webs and the second webs are connected by a first fastener. The elastic bridge deck and the second upper flange are connected by a second fastener.

2. The large-span steel plate composite beam for solving bridge deck cracking in the negative bending moment zone as described in claim 1, characterized in that, The steel main beam assembly has multiple mounting holes inside for adjusting and installing the first fastener.

3. The large-span steel plate composite beam for solving bridge deck cracking in the negative bending moment zone as described in claim 2, characterized in that, The mounting hole is elliptical in shape.

4. The large-span steel plate composite beam for solving bridge deck cracking in the negative bending moment zone as described in claim 1, characterized in that, The first connector has multiple non-communicating grooves, and the top of each groove has an inward protrusion.

5. The large-span steel plate composite beam for solving bridge deck cracking in the negative bending moment zone as described in claim 1, characterized in that, The positive bending moment zone bridge deck assembly also includes at least two second connectors, and the second concrete bridge deck and the second upper flange are connected by the second connectors.

6. The large-span steel plate composite beam for solving bridge deck cracking in the negative bending moment zone as described in claim 1, characterized in that, The resilient bridge panel assembly also includes at least two third connectors, which connect the resilient bridge panel and the second upper flange.

7. The large-span steel plate composite beam for solving bridge deck cracking in the negative bending moment zone as described in claim 1, characterized in that, The steel main beam assembly also includes at least two symmetrically distributed lower flanges, which are connected to the second web.

8. The large-span steel plate composite beam for solving bridge deck cracking in the negative bending moment zone as described in claim 7, characterized in that, The steel plate composite beam also includes supporting stiffening ribs, which are disposed on the surface of the second web plate.

9. The large-span steel plate composite beam for solving bridge deck cracking in the negative bending moment zone as described in claim 8, characterized in that, An insulating coating is applied to the contact surfaces of the first web plate, the second web plate, the supporting stiffening rib, and the first fastener.

10. A construction method for a large-span steel plate composite beam used to solve bridge deck cracking in the negative bending moment zone as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Before construction, the steel main beam assembly, the bridge deck assembly in the positive bending moment zone, and the bridge deck assembly in the negative bending moment zone are prefabricated in sequence. When prefabricating the bridge deck assembly in the negative bending moment zone, the first upper flange, the first web, and the first connector are prefabricated and then welded to form an iron-based shape memory alloy component. The original length of the iron-based shape memory alloy component is L0. The iron-based shape memory alloy component is stretched to a length of L1 and fixed. After fixing, the first concrete bridge deck is poured. When the concrete strength of the first concrete bridge deck reaches 90%, the iron-based shape memory alloy component is released. At this time, the length of the iron-based shape memory alloy component is reduced to L2. The length of the iron-based shape memory alloy component L1 is greater than the length of the iron-based shape memory alloy component L2, which is greater than the length of the iron-based shape memory alloy component L0. S2. During construction, steel main beam components are erected at the bridge site. After erection, bridge deck components in the positive bending moment zone are installed. After installation, bridge deck components in the negative bending moment zone are installed. During installation, the first web and the second web are connected by the first fastener, and the elastic bridge deck and the second upper flange are connected by the second fastener. After connection, the elastic bridge deck is poured. S3. After construction, when cracks appear at the first concrete bridge deck during the operation of the large-span steel plate composite beam that addresses bridge deck cracking in the negative bending moment zone, and the crack width is greater than 2mm, loosen the first and second fasteners, connect the power supply to both ends of the first web to heat the iron-based shape memory alloy component, and cool it after the power supply is completed; after cooling, the length of the iron-based shape memory alloy component is shortened to L3, and the length of the iron-based shape memory alloy component L1 > the length of the iron-based shape memory alloy component L2 > the length of the iron-based shape memory alloy component L3 > the length of the iron-based shape memory alloy component L0.

Images