Four-degree-of-freedom nonlinear energy sink vibration reduction system with stiffness and damping anisotropy

Abstract

The application discloses a four-degree-of-freedom non-linear energy sink damping system with rigidity and damping anisotropy, which comprises a supporting surface, a supporting column, a mass block, a support, and at least three groups of springs and dampers, the support is arranged on the supporting surface, the support supports the mass block, one end of each group of springs and dampers is connected with the mass block, and the other end is connected with the supporting column, the extension line of the axis of each group of springs and dampers does not pass through the center of mass of the mass block, so that the elastic restoring force of each group of springs forms a force arm away from the center of mass of the mass block, and then a moment opposite to the torque direction of the mass block is generated, each group of springs and dampers is arranged in a cyclone shape, the change of the deflection angle of the mass block can be inhibited, different horizontal and vertical spring stiffness and damping are configured, three-direction translation and torsional frequency optimal tuning are realized, and in the movement process, the spring system changes with the increase of the stroke, the change of the included angle leads to the nonlinear change of the rigidity, and multi-modal transient resonance capture is realized.

Description

Technical Field

[0001] This invention relates to a four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping. Background Technology

[0002] Natural disasters such as wind and earthquakes can affect the structural safety of public buildings, thereby threatening property and personal safety. In recent years, tuned vibration control technology has been widely used in high-rise buildings and tall structures due to its advantages of not requiring traditional structural reinforcement measures and having a significant vibration reduction effect.

[0003] A common tuned mass damper (TMD) technology is used for building vibration reduction. When applied to buildings, it typically involves adding an inertial mass at the top or upper part of the structure, connected to the main building structure via slings or springs and dampers to form a damping system. TMDs utilize the principle of resonance to control the dynamic response of certain vibration modes (usually the first mode) of the building structure. When TMDs are used to reduce vertical vibrations such as those caused by walking, springs are often used to provide stiffness; when TMDs are used to reduce lateral vibrations such as those caused by wind or earthquakes, a suspension system or a combination of springs and tracks is often employed.

[0004] Traditional tuned vibration control technology, taking tuned mass dampers (TMDs) as an example, is only applicable to the linear elastic range of the structure, where the period and stiffness remain constant throughout the entire stroke. With low damping, TMDs are extremely sensitive to the structural period and excitation frequency. With high damping, the sensitivity to these factors decreases, but the vibration reduction efficiency also decreases. When encountering non-stationary random excitations, such as earthquakes, the overall vibration reduction efficiency (evaluated by the root mean square value of the response) decreases but still shows good results. However, the vibration reduction effect of the peak response varies significantly, and under very rare seismic waves, TMDs may even have the opposite effect.

[0005] Existing tuned vibration control devices often employ either suspension-type or a combination of springs and tracks. The period of a suspension-type tuned mass damper is determined by the suspension height (i.e., pendulum length), often reaching several stories and requiring a significant amount of building space. Furthermore, its period is uniform in all directions, making it difficult to adapt to the varying periods of different building structures. The spring-track combination, to achieve free vibration of the mass in all directions, requires a precision mechanical system consisting of double-layered unidirectional slide rails and return springs, still occupying considerable space. Its complex mechanism, high cost, and difficult maintenance hinder its widespread adoption.

[0006] like Figure 1 , 2As shown, there are two existing energy trap spring arrangements, both of which are orthogonal centripetal arrangements. Spring 1 is connected between mass block M and support column 2, and spring 1 is aligned with the center of mass of mass block M. Because the anti-torsional lever arm is 0 in the initial state (represented by solid lines, and the position offset state of mass block is represented by dashed lines), it cannot provide the initial reset torque, so a double-layer slide rail is still required. Summary of the Invention

[0007] The purpose of this invention is to provide a four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping that can achieve multimodal transient resonance capture, improve vibration reduction frequency band, enhance the stability of vibration reduction device, significantly reduce space occupation, reduce cost, and facilitate maintenance.

[0008] The objective of this invention is achieved through the following technical measures: a four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping, comprising a support surface, at least three support columns arranged around the periphery of the support surface, a mass block, supports, and at least three sets of springs and dampers, each set of springs and dampers connected vertically in parallel, the supports being disposed on the support surface and supporting the mass block, one end of each set of springs and dampers being connected to the mass block, and the other end being connected to a support column, characterized in that the extension line of the central axis of each set of springs and dampers does not pass through the center of mass of the mass block, such that the elasticity of each set of springs... The restoring force, far from the center of mass of the mass block, forms a lever arm, thereby generating a torque opposite to the torque direction of the mass block. Furthermore, the various sets of tension and compression springs and dampers are arranged in a clockwise or counterclockwise direction based on their inclined arrangement around the periphery of the mass block. That is, the arrangement of each set of springs and dampers is cyclone-like, which can suppress the change of the deflection angle of the mass block. By configuring different horizontal and vertical spring stiffness and damping, the optimal tuning of the three-dimensional translational and torsional frequencies can be achieved. Moreover, due to the increase of the stroke during the motion, the angle of the spring system changes, resulting in a nonlinear change in stiffness, thereby achieving multimodal transient resonance capture.

[0009] This invention can achieve optimal tuning of three-dimensional translational and torsional frequencies (i.e., anisotropic multi-degree-of-freedom tuning) by configuring different horizontal and vertical spring stiffness and damping, to meet the actual needs of different natural frequencies in different directions of building structures. In addition, due to the nonlinear change in stiffness caused by the increase in the included angle of the spring system during the movement, multimodal transient resonance capture (i.e., nonlinear energy trap) can be achieved, which can improve the vibration reduction frequency band and enhance the stability of the vibration reduction device. The arrangement of the springs and dampers in this invention is approximately "cyclone-like", which can suppress the change in the deflection angle of the mass block. Torsional control of the mass block can be achieved without a complex slide rail system, which can significantly reduce the space occupied, reduce the cost, and facilitate maintenance.

[0010] The support described in this invention is a rubber pad support or a sliding support. When it is a rubber pad support with isotropic and shear-type elastic unit properties, the support can provide partial lateral stiffness and torsional stiffness.

[0011] Each spring in this invention consists of multiple springs connected in series. By controlling the stiffness and stroke of each spring, some springs can reach their limit stroke and stop working first. This allows the spring system to provide different stiffnesses in different stroke ranges, thereby achieving a wider range of modal transient resonance capture, further broadening the vibration reduction frequency band, and enhancing the stability of the vibration reduction device.

[0012] The four-degree-of-freedom nonlinear energy trap vibration reduction system described in this invention is placed above the floor slab or suspended below the floor slab.

[0013] The mass block described in this invention uses existing building mass such as fire water tanks or is made of steel cages with internal concrete pouring, which can flexibly adapt to the mass ratio requirements of buildings of different sizes, and is inexpensive.

[0014] As a preferred embodiment of the present invention, the "basic configuration - bidirectional translational type" of the present invention is a configuration with only bidirectional translational stiffness and damping. The mass block is a single block and is located in a nonlinear energy trap formed by support columns on a support surface.

[0015] As another preferred embodiment of the present invention, the "configuration of triaxial translational stiffness and damping" of the present invention is wherein the mass block is located in a nonlinear energy trap formed by a support column on a support surface, the mass block is composed of a groove-shaped outer mass block and an inner mass block built into the outer mass block, the side wall of the inner mass block is connected to the side wall of the outer mass block by a sliding structure, and the bottom surface of the inner mass block and the inner bottom surface of the outer mass block are connected by a spring and a damper in parallel.

[0016] As another preferred embodiment of the present invention, which is the "configuration for mainly resisting torsional vibration mode", the mass block is U-shaped and the support column is located inside the opening of the mass block.

[0017] The sliding structure described in this invention is a ball bearing, roller, or sliding plate, etc.

[0018] In each group described in this invention, there are two or more springs and dampers.

[0019] Compared with the prior art, the present invention has the following significant effects:

[0020] (1) This invention achieves multi-directional vibration control of a structure by configuring different spring stiffnesses and damping in multiple directions using a nonlinear energy trap system. It can achieve up to four-directional (four degrees of freedom) control, while conventional TMDs can only achieve a maximum of two-directional (two degrees of freedom) control. If conventional TMDs are used to adjust the horizontal, torsional, and vertical vibration modes separately, three sets of TMDs must be installed, each requiring a mass block equal to 1-3% of the main structure's mass, resulting in a total increase of 3-9% in the main structure load and requiring a significant amount of building space, thus significantly increasing costs. With the nonlinear energy trap system of this invention, only one set is needed.

[0021] (2) The present invention has the advantage that the contribution ratio of strong and weak springs in each direction is smoothly transitioned, and will not cause abrupt changes in stiffness at different angles, which is similar to the stiffness changes in each direction of the structure itself.

[0022] (3) The spring system of the present invention can provide nonlinear stiffness, thereby realizing modal transient resonance capture, improving the vibration reduction frequency band, stabilizing the transfer of energy to the damping element, and enhancing the stability of the vibration reduction device.

[0023] (4) This invention is non-suspended, which can save more space and has the advantage of not needing to be arranged through layers. It can be placed on or under the floor slab, and the arrangement position and method are flexible.

[0024] (5) The springs and dampers of the present invention adopt a “cyclone-like” arrangement, which has the ability to prevent the mass block from twisting and to return to its original position. Compared with the existing orthogonal arrangement, it has the advantage of not needing to arrange double-layer tracks, which can significantly reduce the space occupied, reduce the cost, and facilitate maintenance.

[0025] (6) The mass block of the present invention can be provided by existing mass such as fire water tank or by steel box + cast-in-place concrete, which can flexibly adapt to the mass ratio requirements of buildings of different sizes and is inexpensive. Attached Figure Description

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0027] Figure 1 It is one of the existing energy trap spring arrangement methods (shown as the initial state and the mass block position offset state);

[0028] Figure 2 This is the second existing energy trap spring arrangement method (showing the initial state and the mass block position offset state);

[0029] Figure 3 This is a top view of Embodiment 1 of the present invention;

[0030] Figure 4 This is a three-dimensional structural schematic diagram of Embodiment 1 of the present invention;

[0031] Figure 5 This is one of the schematic diagrams of Embodiment 1 of the present invention;

[0032] Figure 6 This is the second schematic diagram of the principle of Embodiment 1 of the present invention;

[0033] Figure 7 This is a schematic diagram of the anti-torsion principle of Embodiment 1 of the present invention (showing the initial state and the position offset state of the mass block);

[0034] Figure 8 This is a nonlinear stiffness chart of Embodiment 1 of the present invention;

[0035] Figure 9 It is a linear stiffness chart of an existing TMD;

[0036] Figure 10 This is one of the schematic diagrams of Embodiment 2 of the present invention;

[0037] Figure 11 This is the second schematic diagram of the principle of Embodiment 2 of the present invention;

[0038] Figure 12 This is one of the schematic diagrams of Embodiment 3 of the present invention;

[0039] Figure 13 This is the second schematic diagram of the principle of Embodiment 3 of the present invention;

[0040] Figure 14 This is one of the schematic diagrams of the principle of Embodiment 4 of the present invention;

[0041] Figure 15 This is the second schematic diagram of the principle of Embodiment 4 of the present invention. Detailed Implementation

[0042] Example 1

[0043] like Figures 3-9As shown, this invention provides a four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping. It includes a support surface 3, four support columns 4 arranged around the periphery of the support surface 3, a rectangular mass block M, a support 6, four sets of springs 7, and a damper 8. The mass block M can be an existing building mass such as a fire water tank or a steel cage with cast-in-concrete. Each group has one spring 7 and one damper 8 connected in parallel, one above the other. The support 6 is a rubber pad support, set on the support surface 3. The support 6 supports the mass block. One end of each group of spring 7 and damper 8 is connected to one of the corners of the mass block, and the other end is connected to the support column 4. The extension line of the central axis of each group of spring 7 and damper 8 does not pass through the center of mass of the mass block, so that the elastic restoring force of each group of spring 7 is far away from the center of mass of the mass block to form a lever arm, thereby generating a torque opposite to the torque direction of the mass block. Furthermore, each group of spring 7 and damper 8 is arranged in a clockwise or counterclockwise direction based on its inclined arrangement along the periphery of the mass block, that is, the arrangement of each group of spring 7 and damper 8 is similar to a "whirlwind".

[0044] By configuring different spring stiffnesses and damping in two directions, the main lateral and torsional stiffness are provided. The bottom of the mass block M is supported by a rubber pad bearing with isotropic, shear-type elastic element properties, providing partial lateral and torsional stiffness. This constitutes the basic configuration of the invention, as shown below. Figure 5 , 6 As shown, K1 and K2 are the stiffnesses of the two sets of cyclone springs, C1 and C2 are the damping of the two sets of dampers, K3 and C3 are the horizontal stiffness and damping of the rubber pad support, Kz is the vertical stiffness and damping of the lower support, and angles a1, a1', a2, and a2' are the included angles between each spring / damper and the straight edge of the mass block.

[0045] The expressions for the stiffness in all directions in the global coordinate system are as follows:

[0046] X-axis horizontal stiffness: K x =K2cosα2+K2cosα2'+K1sinα1+K1sinα1'+K3

[0047] Y-direction horizontal stiffness: K y =K1cosα1+K1cosα1'+K2sinα2+K2sinα2'+K3

[0048] Z-axis horizontal stiffness: K z =2K z

[0049] As the amplitude of the mass block's motion increases, the size of angles a1 to a2' changes, causing K to... x K y As it shrinks, it exhibits non-linear characteristics, such as... Figure 8As shown, this enables multimodal transient resonance capture, improves the vibration reduction bandwidth, and realizes the function of a "nonlinear energy trap." The stiffness of a typical TMD is fixed, i.e., linear, as... Figure 9 As shown.

[0050] Large motion of the mass block means that the building structure is subjected to a large horizontal load, which often leads to structural damage and a decrease in the building's natural frequency. The stiffness of this invention decreases as the stroke increases, which can adapt well to this change, thereby achieving high-efficiency vibration reduction throughout the entire process from minor to major earthquakes.

[0051] The springs in the nonlinear energy trap are composed of multiple springs connected in series. By controlling the stiffness and stroke of each spring, some springs can reach their limit stroke and stop working first, allowing the spring system to provide different stiffnesses in different stroke ranges. Figure 8 As shown, this enables the capture of modal transient resonances over a wider range, further broadens the vibration reduction frequency band, and enhances the stability of the vibration reduction device.

[0052] Conventional track-type TMDs, when faced with random vibrations, exhibit uncontrolled torsional vibrations of the mass block, resulting in a chaotic state that can lead to TMD system failure. Therefore, a complex mechanism with double-layered unidirectional guide rails is necessary to prevent torsion. This invention, the "nonlinear energy trap," achieves stable vibration without a guide rail system through a unique "cyclone-like" arrangement of the spring-damped system. Figure 7 As shown, the spring generates an elastic force K*Δ due to deformation Δ. The direction of this force is away from the center of mass of the mass block, forming a lever arm L and generating a torque K*Δ*L. Its direction of action is opposite to the torsional direction of the mass block, so it is a "resetting torque", which fundamentally prevents the torsional vibration of the mass block.

[0053] Example 2

[0054] By adjusting the basic configuration of this invention, various configurations can be derived to meet complex requirements.

[0055] like Figure 10 , 11 As shown, the difference between this embodiment and embodiment 1 is that the support 6 is a sliding support, and the spring K z When the stiffness is very high, this embodiment has only two-way translational stiffness and damping. Therefore, this embodiment is a two-way translational type.

[0056] Example 3

[0057] like Figure 12 , 13As shown, the difference between this embodiment and Embodiment 2 is that the mass block is split into a configuration with triaxial translational stiffness and damping. In this embodiment, the mass block consists of a groove-shaped outer mass block M2 and an inner mass block M1 built into the outer mass block M2. The sidewalls of the inner mass block M1 and the sidewalls of the outer mass block M2 are connected by a sliding structure 9, which can be a ball bearing, roller, or sliding plate, etc. The bottom surface of the inner mass block M1 and the inner bottom surface of the outer mass block M2 are connected by a spring and a damper.

[0058] Example 4

[0059] like Figure 14 , 15 As shown, the difference between this embodiment and embodiment 2 is that the mass block M is U-shaped, and the support column 4 is located inside the opening of the mass block M, forming a configuration that mainly resists torsional vibration modes.

[0060] In a specific application, a certain command tower, due to its unique shape, has its mass primarily concentrated at the top and is horizontally offset. Under seismic loads, the top of the tower experiences simultaneous triaxial translational and torsional displacements, whereas typical command towers generally only experience biaxial horizontal translational displacement. Conventional tuned mass dampers can only adjust for biaxial horizontal seismic loads and are largely ineffective against torsional and vertical vibration modes. However, the nonlinear energy trap vibration reduction control system of this invention can simultaneously achieve optimal tuning of triaxial translational and torsional frequencies using a single system, making it suitable for vibration control of complex structures.

Claims

1. A four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping, comprising a support surface, at least three support columns arranged around the periphery of the support surface, a mass block, supports, and at least three sets of springs and dampers, wherein the springs and dampers in each set are connected in parallel vertically, the supports are arranged on the support surface, the supports support the mass block, and one end of each set of springs and dampers is connected to the mass block, and the other end is connected to a support column, characterized in that: The extension of the central axis of each set of springs and dampers does not pass through the center of mass of the mass block, so that the elastic restoring force of each set of springs is far away from the center of mass of the mass block, forming a lever arm, thereby generating a torque opposite to the torque direction of the mass block. Furthermore, each set of springs and dampers is arranged in a clockwise or counterclockwise direction based on its inclined arrangement along the periphery of the mass block, that is, each set of springs and dampers is arranged in a whirlwind shape, which can suppress the change of the deflection angle of the mass block. By configuring different horizontal and vertical spring stiffness and damping, the optimal tuning of the three-dimensional translational and torsional frequencies can be achieved. Moreover, as the spring system moves with the increase of stroke during the motion, the angle changes, resulting in a nonlinear change in stiffness, thereby achieving multimodal transient resonance capture.

2. The four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping according to claim 1, characterized in that: Each set of springs consists of multiple springs connected in series. By controlling the stiffness and stroke of each spring, some springs can reach their limit stroke first and then stop working, thus providing different stiffness in different stroke ranges.

3. The four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping according to claim 2, characterized in that: The four-degree-of-freedom nonlinear energy trap vibration reduction system is placed above the floor slab or suspended below the floor slab.

4. The four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping according to claim 3, characterized in that: The mass block is made from existing building mass or from a steel cage with cast-in-place concrete.

5. The four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping according to claim 4, characterized in that: The mass block is a single piece located within the space formed by the support columns set on the support surface.

6. The four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping according to claim 4, characterized in that: The mass block is located in the space formed by the support column on the support surface. The mass block consists of a groove-shaped outer mass block and an inner mass block built into the outer mass block. The sidewall of the inner mass block is connected to the sidewall of the outer mass block by a sliding structure. The bottom surface of the inner mass block and the inner bottom surface of the outer mass block are connected by a spring and a damper.

7. The four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping according to claim 6, characterized in that: The sliding structure is a ball bearing, roller, or slide plate.

8. The four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping according to claim 4, characterized in that: The mass block is U-shaped, and the support column is located inside the opening of the mass block.

9. The four-degree-of-freedom nonlinear energy trap vibration reduction system with anisotropic stiffness and damping according to any one of claims 5 to 8, characterized in that: Each group contains two or more springs and dampers.

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