Negative stiffness friction damper and output calculation method

Abstract

The present invention relates to the technical field of building shock absorption, and specifically to a negative stiffness friction damper and an output calculation method. By setting a preload spring and a friction component, the damper has a negative stiffness characteristic; during an earthquake, a horizontal displacement difference is generated between the lower structure and the upper structure of the building, and the negative stiffness cylinder is driven to move horizontally through the lower structure of the building, so that the middle plate moves horizontally based on the negative stiffness cylinder and the friction cylinder, driving the preload spring to undergo elastic deformation, releasing its stored deformation potential energy, which is specifically manifested as a trend to promote more slip separation between the negative stiffness cylinder and the middle plate, so that the damper has a negative stiffness characteristic; the negative stiffness characteristic of the damper can be judged by calculating the damper output, so as to adjust the coefficient of the preload spring to make the negative stiffness characteristic of the damper better.

Description

Technical Field

[0001] The invention relates to the technical field of building shock absorption, in particular to a negative stiffness friction damper and an output calculation method. Background Art

[0002] With the rapid development of the construction industry, traditional seismic design concepts can no longer meet the current high requirements for seismic performance. In order to improve the seismic resistance of building structures, the design concept of energy dissipation and shock absorption has gradually been widely used in building seismic design. Energy dissipation and shock absorption technology mainly involves widely arranging shock-absorbing dampers on multiple floors, which greatly reduce the response of the structure in an earthquake. However, the existing shock-absorbing dampers themselves have a certain positive stiffness. When these dampers are arranged for additional damping of the building structure, the positive stiffness of the structure may increase, which may have an adverse effect on the structure.

[0003] At the same time, in some special buildings, such as hospital operating rooms and laboratories storing precision instruments, we are more concerned about the acceleration of the building during an earthquake, rather than just the overall displacement. However, the current design of most dampers focuses on controlling the overall displacement of the building structure, and the control effect on the building acceleration is not ideal. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the existing shock absorbing damper has a certain positive stiffness which affects the structural stability.

[0005] In order to solve the above problems, the present invention provides a damper which can reduce the influence of the damper on the building structure and increase the shock absorption effect;

[0006] The first technical solution of the present invention is:

[0007] A negative stiffness friction damper comprises a negative stiffness cylinder, a friction cylinder and an intermediate plate, wherein the negative stiffness cylinder is used to connect the lower structure of a building, the intermediate plate is horizontally movably arranged in the negative stiffness cylinder and the friction cylinder, prestressed springs are connected between the top and bottom surfaces of the intermediate plate and the negative stiffness cylinder, and the outer end of the intermediate plate passes through the friction cylinder and is connected to the upper structure of the building; a friction assembly is arranged on the friction cylinder, and the inner end of the friction assembly abuts against one end of the intermediate plate away from the negative stiffness cylinder; when the horizontal relative displacement of the upper structure and the lower structure of the building is zero, the prestressed spring is perpendicular to the intermediate plate, and the prestressed spring is in a prestressed state at this time.

[0008] Preferably, a further technical solution of the present invention is:

[0009] There are two groups of friction components, which include friction blocks and screws. The friction blocks of each group of friction components are respectively in contact with the top surface or bottom surface of the middle plate, and the bottom surface of the screw is fixed to the friction block, which is threadedly connected to the friction cylinder. The friction blocks are in contact with the top and bottom surfaces of the middle plate through the screws, and when the middle plate moves, the friction blocks provide damping force for the middle plate.

[0010] A telescopic rod is inserted in the middle of the preload spring, and the two ends of the telescopic rod are respectively clamped on the middle plate and the inner wall of the negative rigidity cylinder. The preload spring is limited to axial deformation by the telescopic rod, and when the middle plate moves, the preload spring provides elastic force for the middle plate.

[0011] The top and bottom surfaces of the middle plate away from one end of the friction cylinder are both provided with a first arc groove, the inner wall of the negative stiffness cylinder is provided with a second arc groove, the two ends of the telescopic rod are respectively connected with arc plates, the two ends of the preload spring are respectively fixed to the arc plates at the two ends, and the arc plates at the two ends are respectively rotated and clamped in the first arc groove and the second arc groove. Through the above structure, the preload spring is easy to be axially deformed under the drive of the middle plate.

[0012] Symmetrical moving grooves are arranged on the inner walls of the negative rigidity cylinder and the friction cylinder, and the two ends of the middle plate are arranged in the moving grooves at the two ends. The above structure facilitates the middle plate to move in the negative rigidity cylinder and the friction cylinder under the limitation of the moving grooves.

[0013] The second technical solution of the present invention is:

[0014] A method for calculating the output of a negative stiffness friction damper is applied to the above-mentioned negative stiffness friction damper and comprises the following steps:

[0015] Step 1: Set the parameters of the preload spring. When the surface of the middle plate is perpendicular to the axis of the preload spring, the preload spring is in an initial state and the middle plate is in an initial position. Calculate the initial preload of a single preload spring in the initial state according to the parameters of the preload spring.

[0016] Step 2: Set the horizontal displacement of the middle plate, and calculate the length of the preload spring after the movement according to the horizontal displacement and the initial length of the telescopic rod; and calculate the elastic force of the preload spring and the angle between the axial direction of the preload spring and the horizontal direction according to the initial preload of the preload spring and the length of the preload spring;

[0017] Step 3: Calculate the negative stiffness force and stiffness of the preload spring according to the elastic force and angle of the preload spring; and generate a change curve of the negative stiffness force and stiffness of the preload spring during horizontal displacement;

[0018] Step 4: Calculate the output force of the damper according to the negative stiffness force of the preload spring and the friction force of the friction assembly;

[0019] Step 5: Set the horizontal displacement of the middle plate again, and repeat the calculation steps from step 2 to step 5 to calculate the damper output at different horizontal displacements to generate the hysteresis curve of the friction damper.

[0020] Preferably, a further technical solution of the present invention is:

[0021] The calculation formula of the initial preload is:

[0022] ;

[0023] in, is the initial preload pressure, is the stiffness of the preload spring, is the initial compression ratio of the preloaded spring, is the free length of the preloaded spring.

[0024] The calculation formula of step 2 is:

[0025] ;

[0026] ;

[0027] ;

[0028] in, is the length of the preloaded spring after movement, is the horizontal displacement of the middle plate, is the initial length of the telescopic rod, is the pressure of the preload spring, The angle between the axial direction of the preload spring and the horizontal direction.

[0029] The calculation formula of the negative stiffness force of the preload spring and the stiffness of the preload spring in step 3 is:

[0030] ;

[0031] ;

[0032] Arranged:

[0033] ;

[0034] .

[0035] The calculation formula of step 4 is:

[0036] ;

[0037] in, is the damper output, is the friction force of the friction component, for Sign function, when the middle plate moves away from the initial position, The first derivative of is less than 0, Take -1; when the middle plate moves closer to the initial position, The first-order derivative of is greater than 0, Take 1.

[0038] Compared with the prior art, the present invention using the above-mentioned technical solution 1 and technical solution 2 has the following beneficial effects:

[0039] By setting a preload spring and a friction component, the damper is endowed with a negative stiffness characteristic. During an earthquake, a horizontal displacement difference is generated between the lower structure and the upper structure of the building, and the negative stiffness cylinder is driven to move horizontally through the lower structure of the building, so that the middle plate moves horizontally based on the negative stiffness cylinder and the friction cylinder, driving the preload spring to undergo elastic deformation, releasing its stored deformation potential energy, which is specifically manifested as a trend that promotes a greater dislocation and separation between the negative stiffness cylinder and the middle plate, thereby giving the damper a negative stiffness characteristic. The negative stiffness characteristic of the damper can be determined by calculating the damper output, thereby adjusting the coefficient of the preload spring to make the negative stiffness characteristic of the damper better. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a three-dimensional diagram of the damper structure of the first embodiment of the present invention;

[0041] Figure 2 A top view of the damper structure of Embodiment 1 of the present invention;

[0042] Figure 3 for Figure 2 Sectional view at AA;

[0043] Figure 4 for Figure 2 Cross-section at the middle BB;

[0044] Figure 5 for Figure 2 Cross-section at CC;

[0045] Figure 6 This is a schematic diagram of the curved plate structure of the first embodiment of the present invention;

[0046] Figure 7 This is a schematic diagram of the structure of the preload spring, telescopic rod and arc plate according to the first embodiment of the present invention;

[0047] Figure 8 is a cross-sectional view of the middle plate in the initial position according to the first embodiment of the present invention;

[0048] Fig. 9is a schematic diagram of a damper in a loading stage according to a second embodiment of the present invention;

[0049] Fig.10 is a negative stiffness hysteresis curve diagram of the negative stiffness friction damper according to the second embodiment of the present invention;

[0050] In the figure: 1. negative stiffness cylinder; 11. ear plate; 12. first side end cover; 13. bolt; 14. arc plate; 141. embedded groove; 15. preload spring; 16. movable groove; 17. telescopic rod; 2. friction cylinder; 21. screw; 22. second side end cover; 23. friction block; 3. middle plate; 4. upper structure; 5. lower structure. DETAILED DESCRIPTION

[0051] The present invention will be further described below in conjunction with embodiments, the purpose of which is only to provide a better understanding of the content of the present invention. Therefore, the examples given do not limit the protection scope of the present invention.

[0052] See attached Figure 1-9 The first embodiment of the present invention discloses a negative stiffness friction damper, comprising a negative stiffness cylinder 1, a friction cylinder 2 and an intermediate plate 3. A negative stiffness inner cavity is provided inside the negative stiffness cylinder 1, a friction cavity is provided inside the friction cylinder 2, the negative stiffness cavity and the friction cavity are connected, the negative stiffness cylinder 1 and the friction cylinder 2 are threadedly connected by bolts 13, a first side end cover 12 is fixed to the end of the negative stiffness cylinder 1 away from the friction cylinder 2, a lug plate 11 is fixed to the first side end cover 12, the negative stiffness cylinder 1 and the lower structure 5 of the building are fixedly connected by the lug plate 11, the intermediate plate 3 is horizontally movably arranged in the negative stiffness cylinder 1 and the friction cylinder 2, and preload springs 15 are connected between the top and bottom surfaces of the intermediate plate 3 and the negative stiffness cylinder 1; a second side end cover 22 is fixed to the end of the friction cylinder 2 away from the negative stiffness cylinder 1, and the intermediate plate The outer end of 3 extends outward through the second side end cover 22, and a mounting hole is provided on the middle plate 3 outside the friction cylinder body 2, and the middle plate 3 is connected to the upper structure 4 of the building through the mounting hole; friction components are provided on the upper and lower sides of the friction cylinder body 2, and the inner end of the friction component abuts against the top surface or bottom surface of the middle plate 3 away from the negative stiffness cylinder body 1; when the horizontal relative displacement of the upper structure 4 and the lower structure 5 of the building is zero, the pre-stressed spring 15 is perpendicular to the middle plate 3, and the pre-stressed spring 15 is in a pre-stressed state at this time, and the middle plate 3 is in an initial position. When the middle plate 3 moves to the left or right side away from the initial position, the pre-stressed spring 15 is in a state of gradually releasing elastic potential energy; when the middle plate 3 moves to the left or right side close to the initial position, the pre-stressed spring 15 is in a state of gradually storing elastic potential energy.

[0053] In this embodiment, the top and bottom surfaces of the middle plate 3 away from one end of the friction cylinder 2 are respectively provided with four first arc grooves, and the upper inner wall and the lower inner wall of the negative stiffness cylinder 1 are respectively provided with four second arc grooves; the top and bottom surfaces of the middle plate 3 are respectively connected with eight preload springs 15, and the preload springs 15 on the same side are grouped in pairs, and the two ends of the two preload springs 15 in the same group are respectively fixedly connected with arc plates 14, and the arc plates 14 connected to the inner ends of the preload springs 15 are rotatably engaged in the first arc grooves on the top or bottom surfaces of the middle plate 3, and the arc plates 14 connected to the outer ends of the preload springs 15 are rotatably engaged in the second arc grooves on the upper inner wall or the lower inner wall of the negative stiffness cylinder 1; a telescopic rod 17 is inserted in the middle of the preload springs 15, The inner sides of the arc-shaped plates 14 at both ends of the two pre-stress springs 15 in the same group are provided with embedding grooves 141, and the two ends of the telescopic rod 17 are embedded in the corresponding embedding grooves 141, and the pre-stress spring 15 is limited by the telescopic rod 17 to axially deform; when the middle plate 3 moves based on the negative stiffness cylinder 1, the arc-shaped plate 14 is driven to move by the middle plate 3. At this time, the arc-shaped plate 14 is limited by the telescopic rod 17 and the pre-stress spring 15, so that the arc-shaped plate 14 rotates in the first arc groove. At this time, the pre-stress spring 15 gradually undergoes axial deformation under the action of the telescopic rod 17, and the arc-shaped plate 14 in the first arc groove also rotates synchronously, and due to the elastic support of the pre-stress spring 15, the arc-shaped plates 14 at both ends will not detach from the first arc groove or the second arc groove.

[0054] In this embodiment, two groups of friction components are provided, and the two groups of friction components are respectively provided on the friction cylinder 2 on the upper side and the lower side of the middle plate 3. The friction components include a friction block 23 and two screws 21. The inner ends of the two screws 21 are fixed to the friction block 23. The two screws 21 are threadedly connected to the friction cylinder 2, and the outer ends of the two screws 21 protrude from the friction cylinder 2 and extend outward. The friction block 23 is used to abut against the top surface or the bottom surface of the middle plate 3. By tightening the screw 21, the friction block 23 abuts against the top surface and the bottom surface of the middle plate 3. When the middle plate 3 moves, the friction block 23 provides damping force for the middle plate 3.

[0055] In this embodiment, symmetrical moving grooves 16 are provided through the inner walls of the negative rigidity cylinder 1 and the friction cylinder 2, and the moving grooves 16 match the shape and size of the two ends of the middle plate 3, and the two ends of the middle plate 3 are moved in the moving grooves 16 at the two ends. Through the above structure, it is convenient for the middle plate 3 to move in the negative rigidity cylinder 1 and the friction cylinder 2 under the limitation of the moving grooves 16.

[0056] The working principle of the damper in this embodiment is:

[0057] During an earthquake, under horizontal earthquake excitation, the movement speeds of the upper structure 4 and the lower structure 5 of the building will be different, and then the upper structure 4 and the lower structure 5 will move displaced from each other. At this time, the dislocation between the floors will cause the middle plate 3 and the negative stiffness cylinder 1 and the friction cylinder 2 to move relative to each other; when the middle plate 3 is in the initial position, the preload spring 15 is in a compressed state, and its stored elastic force is When the negative stiffness cylinder 1 and the middle plate 3 are displaced and moved under the drive of the upper structure 4 and the lower structure 5, that is, when the middle plate 3 moves from the initial position to the position away from the initial position, the elastic force of the preload spring 15 A component along the direction of movement of the damper will be generated, which will cause the preload spring 15 to stretch and release its stored deformation potential energy. The specific manifestation of this potential energy is a tendency to promote the further displacement and separation between the negative stiffness cylinder 1, the friction cylinder 2 and the middle plate 3, which will generate a driving force along the direction of movement, thereby promoting the movement of the middle plate 3; when the middle plate 3 moves from the initial position away from the initial position, the elastic force A component will be generated to prevent the middle plate 3 from returning to its initial position. This process is the embodiment of the negative stiffness characteristic, that is, when the structure is subjected to external force, the stiffness will show characteristics opposite to those of the conventional structure. Therefore, the damper shows negative stiffness characteristics in the working state.

[0058] my country's Technical Code for Energy Dissipation and Shock Absorption of Buildings JGJ 297-2013 uses a restoring force model (i.e., hysteresis curve) to evaluate the performance of building dampers. This model is mainly divided into two categories: one is a curve-type restoring force model with more parameters, higher accuracy, and closer to reality, but due to its relatively complex parameter determination and calculation, it is limited in practical applications; the other is a simplified linear restoring force model, which is widely used in practice due to its simplicity. At present, the commonly used linear restoring force model is a hyperbolic model, which can distinguish the working state of the damper in the loading stage and the unloading stage.

[0059] In order to combine with engineering practice and facilitate later engineering applications, the hysteresis curve of the negative stiffness friction damper proposed in this invention can be described by a typical hyperbolic model. Fig.10, the hysteresis curve can be divided into the following stages: First, the AB1 segment is the stage when the damper enters the forward loading stage, indicating that the middle plate 3 moves forward from the initial position to the position away from the initial position under the action of the external load; point B1 is the point where the damper reaches the ultimate load in the forward movement and the middle plate 3 reaches the forward ultimate displacement. Subsequently, the middle plate 3 begins to move back from the forward maximum displacement position to the initial position. Under the action of friction damping, the curve jumps from point B1 to point B2, and then enters the unloading stage along the B2C segment until it reaches point C, at which time the middle plate 3 returns to the initial position. Afterwards, the CD1 segment is the stage when the damper enters the reverse loading stage, indicating that the middle plate 3 moves in the reverse direction from the initial position to the position away from the initial position under the action of the external load; point D1 is the point where the damper reaches the ultimate load in the reverse movement and the middle plate 3 reaches the reverse ultimate displacement. Then, the damper moves again from the reverse maximum displacement position to the initial position. Under the influence of friction damping, the hysteresis curve jumps from point D1 to point D2, and finally returns to the initial position point A along the D2A segment, completing the entire unloading stage. Therefore, the A-B1-B2-C-D1-D2-A point band constitutes the building damper hysteresis curve recommended by the code, which completely includes the loading and unloading stages. The area enclosed by this hysteresis loop is the seismic energy dissipated by the damper in one vibration cycle.

[0060] In the friction cylinder 2, the normal pressure of the contact between the friction block 23 and the middle plate 3 can be controlled by rotating the screw 21. When the friction block 23 contacts the middle plate 3, the damper exhibits a damping characteristic under the action of the friction force. The friction damping calculation follows the Kullo model, that is, it is assumed that the friction coefficient between the friction block 23 and the middle plate 3 is a constant value; when the middle plate 3 moves from the initial position to the distance from the initial position, the preload spring releases the stored potential energy, and the negative stiffness friction damper enters the loading stage. At this time, the friction block 23 will generate a damping force in the opposite direction to the horizontal component of the preload of the preload spring 15, and the damping force is intended to hinder the relative movement between the middle plate 3 and the negative stiffness cylinder 1 and the friction cylinder 2; on the contrary, when the middle plate 3 moves from the distance from the initial position to the proximity of the initial position, the preload spring is in a state of gradually storing elastic potential energy, that is, the preload spring is passively compressed, and the negative stiffness friction damper enters the unloading stage. At this time, the friction block 23 will generate a damping force in the same direction as the horizontal component of the preload of the preload spring 15, and the damping force is intended to promote the relative movement between the middle plate 3 and the negative stiffness cylinder 1 and the friction cylinder 2.

[0061] Embodiment 2 of the present invention discloses a method for calculating the output of a negative stiffness friction damper, which is applied to the above-mentioned negative stiffness friction damper and includes the following steps:

[0062] Step 1: Set the parameters of the preload spring 15. When the surface of the middle plate 3 is perpendicular to the axial direction of the preload spring 15, the preload spring 15 is in the initial state, the damper is in a balanced state as a whole, and the middle plate 3 is in the initial position. Calculate the initial preload of a single preload spring 15 in the initial state according to the parameters of the preload spring 15. Specifically, assume that the stiffness of the preload spring 15 is , the initial compression ratio is , the free length of the preload spring is , the initial preload provided by a single preload spring for:

[0063] ;

[0064] Step 2: Set the horizontal displacement of the middle plate 3 , according to the horizontal displacement and the initial length of the telescopic rod 17 in the equilibrium state Calculate the length of the preloaded spring 15 after movement :

[0065] ;

[0066] Then, according to the initial preload of the preload spring 15 and preload spring 15 length Calculate the elastic force of the preload spring 15 , and the angle between the axial direction and the horizontal direction of the preload spring 15 :

[0067] ;

[0068] ;

[0069] Step 3: According to the elastic force of the preload spring 15 and angle Calculate the negative stiffness force of the preload spring 15 and preload spring 15 stiffness ; and generate a change curve of the negative stiffness force and stiffness of the preload spring 15 during horizontal displacement;

[0070] ;

[0071] ;

[0072] Arranged:

[0073] ;

[0074] .

[0075] Step 4: According to the negative stiffness force of the preload spring 15 and friction of the friction components Calculate the damper output When the middle plate 3 moves from the initial position to the position away from the initial position, that is, the preload spring 15 is in a state of gradually releasing elastic potential energy, due to the existence of the friction force of the friction assembly, the friction block 23 will generate the preload of the preload spring 15 The horizontal component of the force is opposite to , hindering the movement of the middle plate 3;

[0076] The damper output during the loading phase is:

[0077] ;

[0078] When the middle plate 3 moves from the initial position away from the initial position to the initial position close to the initial position, that is, the preload spring 15 is in a state of gradually storing elastic potential energy, due to the existence of the friction force of the friction assembly, the friction block 23 will generate The horizontal component of the force is in the same direction , promoting the movement of the middle plate 15.

[0079] The damper output in the unloading stage is:

[0080] ;

[0081] Comprehensive formula

[0082] ;

[0083] in, is the damper output, is the friction force of the friction component, for Sign function, when the middle plate 15 moves away from the initial position, The first derivative of is less than 0, Take -1; when the middle plate 15 moves closer to the initial position, The first-order derivative of is greater than 0, Take 1.

[0084] Step 5: Set the horizontal displacement of the middle plate 15 again, and repeat the calculation steps from step 2 to step 5 to calculate the damper output at different horizontal displacements to generate Fig.10 The hysteresis curve of the friction damper is shown.

[0085] In this embodiment, in the negative stiffness design stage, first, various parameters of the preload spring are determined based on the expected negative stiffness output, including but not limited to the stiffness, initial compression ratio, free length and the number of preload springs 15 required of the preload spring; then, the working stroke of the negative stiffness friction damper, that is, the expected relative displacement of the middle plate 3, needs to be clarified; in the friction design stage, first, according to the characteristics of the working environment, the appropriate friction block 23 material and the friction coating on the middle plate 3 are selected. The friction coefficient between the friction block 23 and the middle plate 15 directly affects the effect of friction damping. After the friction coefficient is determined, the positive pressure between the friction block 23 and the middle plate 3 is calculated based on the expected friction force; the calculation formula of the friction force is: ,in, The friction provided to the friction component, is the dynamic friction coefficient between the friction block 23 and the middle plate 3, is the positive pressure between the friction block 23 and the middle plate 3; finally, in the combined design stage, the negative stiffness design is connected in series with the friction design to form a complete straight-tube preloaded spring negative stiffness friction damper. On this basis, a force model is preliminarily constructed. According to the aforementioned design method and combined with the data parameters shown in the table below, the theoretical hysteresis curve of the straight-tube preloaded spring negative stiffness friction damper can be drawn:

[0086]

[0087] The above description is only a preferred feasible embodiment of the present invention, and does not limit the scope of rights of the present invention. All equivalent changes made using the contents of the present invention specification and its drawings are included in the scope of rights of the present invention.

Claims

1. A negative stiffness friction damper, characterized in that: It includes a negative stiffness cylinder, a friction cylinder and an intermediate plate. The negative stiffness cylinder is used to connect the lower structure of the building. The intermediate plate is horizontally movable and arranged in the negative stiffness cylinder and the friction cylinder. Prestressed springs are connected between the top and bottom surfaces of the intermediate plate and the negative stiffness cylinder, and the outer end of the intermediate plate passes through the friction cylinder and is connected to the upper structure of the building. A friction assembly is arranged on the friction cylinder, and the inner end of the friction assembly abuts against one end of the intermediate plate away from the negative stiffness cylinder. When the horizontal relative displacement of the upper structure and the lower structure of the building is zero, the prestressed spring is perpendicular to the intermediate plate, and the prestressed spring is in a prestressed state at this time.

2. The negative stiffness friction damper according to claim 1, characterized in that: There are two groups of friction components, which include friction blocks and screws. The friction blocks of each group of friction components are respectively abutted against the top surface or the bottom surface of the middle plate, the bottom surface of the screw is fixed to the friction block, and the screw is threadedly connected to the friction cylinder.

3. The negative stiffness friction damper according to claim 1, characterized in that: A telescopic rod is inserted in the middle of the preload spring, and two ends of the telescopic rod are respectively clamped on the middle plate and the inner wall of the negative rigidity cylinder.

4. The negative stiffness friction damper according to claim 1, characterized in that: A first arc groove is provided on the top and bottom surfaces of the middle plate away from one end of the friction cylinder body, a second arc groove is provided on the inner wall of the negative stiffness cylinder body, both ends of the telescopic rod are respectively connected with arc plates, both ends of the preload spring are respectively fixed to the arc plates at both ends, and the arc plates at both ends are respectively rotated and clamped in the first arc groove and the second arc groove.

5. The negative stiffness friction damper according to claim 1, characterized in that: Symmetrical moving grooves are arranged on the inner walls of the negative rigidity cylinder body and the friction cylinder body, and the two ends of the middle plate are movably arranged in the moving grooves at the two ends.

6. A method for calculating the output of a negative stiffness friction damper, applied to the negative stiffness friction damper according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Set the parameters of the preload spring. When the surface of the middle plate is perpendicular to the axis of the preload spring, the preload spring is in an initial state and the middle plate is in an initial position. Calculate the initial preload of a single preload spring in the initial state according to the parameters of the preload spring. Step 2: Set the horizontal displacement of the middle plate, and calculate the length of the preload spring after the movement according to the horizontal displacement and the initial length of the telescopic rod; and calculate the elastic force of the preload spring and the angle between the axial direction of the preload spring and the horizontal direction according to the initial preload of the preload spring and the length of the preload spring; Step 3: Calculate the negative stiffness force and stiffness of the preload spring according to the elastic force and angle of the preload spring; and generate a change curve of the negative stiffness force and stiffness of the preload spring during horizontal displacement; Step 4: Calculate the output force of the damper according to the negative stiffness force of the preload spring and the friction force of the friction assembly; Step 5: Set the horizontal displacement of the middle plate again, and repeat the calculation steps from step 2 to step 5 to calculate the damper output at different horizontal displacements to generate the hysteresis curve of the friction damper.

7. The method for calculating the output of a negative stiffness friction damper according to claim 6, characterized in that: The calculation formula of the initial preload is: P in =K s λl; Among them, P in is the initial preload, K s is the stiffness of the preload spring, λ is the initial compression ratio of the preload spring, and l is the free length of the preload spring.

8. The method for calculating the output of a negative stiffness friction damper according to claim 7, characterized in that: The calculation formula of step 2 is: F s =P in -K s (l s -l p ); Among them, l s is the length of the preload spring after movement, u is the horizontal displacement of the middle plate, l p is the initial length of the telescopic rod, F s is the pressure of the preload spring, and cosθ is the angle between the axial direction of the preload spring and the horizontal direction.

9. The method for calculating the output of a negative stiffness friction damper according to claim 8, characterized in that: The calculation formula of the negative stiffness force of the preload spring and the stiffness of the preload spring in step 3 is: F NSD =f s cosθ; Arranged: Among them, F NSD is the negative stiffness force of the preload spring, K NSD is the preload spring stiffness.

10. The method for calculating the output of a negative stiffness friction damper according to claim 9, characterized in that: The calculation formula of step 4 is: Among them, F fic is the output of the damper, f is the friction force of the friction component, for Sign function, when the middle plate moves away from the initial position, the first-order derivative of u is less than 0, Take -1; when the middle plate moves closer to the initial position, the first-order derivative of u is greater than 0, Take 1.

Images