Small-size large-displacement variable-stiffness self-resetting SMA cable bridge shock-absorbing damper and method
By using a combination structure of small-sized SMA cables and inner steel tubes within an outer steel tube in bridge vibration dampers, and utilizing pulley and chute mechanisms to achieve variable stiffness and limiting, the problems of excessive length and insufficient variable stiffness of SMA cable dampers are solved, thereby improving the safety and ease of construction of the structure.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- FUZHOU UNIV
- Filing Date
- 2026-03-19
- Publication Date
- 2026-05-19
AI Technical Summary
Existing SMA cable dampers are too long and lack sufficient variable stiffness capacity in bridge seismic isolation design, resulting in difficult construction and installation and poor economic efficiency.
The structure adopts a small-sized SMA cable combined with an outer steel tube and an inner steel tube. The SMA cable is arranged in an S-shape, and the variable stiffness and limiting function are achieved by using pulleys and grooves. The relative movement between the inner and outer steel tubes enhances the constraint force.
This achievement enables a reduction in the size of the damper under large displacement, fully utilizes the properties of SMA material, improves structural safety and engineering applicability, and prevents the risk of beam collapse.
Smart Images
Figure CN122061401A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of bridge vibration reduction technology, and in particular to a small-size, large-displacement, variable stiffness, self-resetting SMA cable bridge vibration damper and method. Background Technology
[0002] Shape memory alloys (SMAs) possess excellent self-centering capabilities, leading to widespread interest in their application in civil engineering. SMA cables can be used for vibration damping and energy dissipation in bridges, and their self-centering ability has made them popular among academics and engineering designers.
[0003] Although SMA cables have excellent strain capacity, in bridge engineering seismic isolation design, achieving a large displacement capacity usually requires longer SMA cables. For example, to achieve a displacement capacity of 40 cm, even with an SMA cable design based on 8% strain capacity, a 5 m long SMA cable is required. Excessively long SMA cables pose significant challenges in structural layout, construction, installation, and maintenance.
[0004] On the other hand, in bridge seismic isolation design, the main girder is typically isolated by reducing the bearing stiffness, thereby reducing the stress on the piers. However, seismic isolation design significantly increases the relative displacement between the piers and the girder, which can easily lead to the risk of girder collapse under strong earthquakes. To address this, researchers have proposed installing variable stiffness dampers between the piers and the girder: under minor earthquakes, the damper stiffness is relatively low, which is beneficial for seismic isolation; while under major earthquakes, when the displacement reaches a certain threshold, the damper stiffness increases significantly to limit the relative displacement between the piers and the girder, thereby effectively preventing girder collapse.
[0005] Existing SMA cable dampers typically lack variable stiffness characteristics, or achieve the effect by gradually activating multiple sets of SMA cables at different displacement stages. However, due to the high cost of SMA materials, these methods struggle to fully utilize the mechanical properties of SMA materials and are also economically unsound. Summary of the Invention
[0006] The purpose of this invention is to provide a small-sized, large-displacement, variable-stiffness self-resetting SMA cable-stayed bridge damper and method, which can solve the problems of excessive length and insufficient variable stiffness capacity of existing SMA cable dampers under large displacement requirements.
[0007] The technical solution of this invention: Small-size, large-displacement, variable stiffness, self-resetting SMA cable bridge vibration damper and method, including SMA cable, outer steel pipe and inner steel pipe slidably connected in the outer steel pipe; The outer steel pipe has a first slot and a second slot on both its front and rear sides, and the first slot and the second slot are located at different heights; the inner steel pipe has a third slot and a fourth slot on both its front and rear sides, the third slot is located at the same position as the first slot, and the length of the third slot is greater than the length of the first slot; the fourth slot is located at the same position as the second slot, and the length of the fourth slot is greater than the length of the second slot. The inner steel tube is provided with a first pulley and a second pulley. The first pulley is rotatably connected to a first pulley shaft, and the second pulley is rotatably connected to a second pulley shaft. The two ends of the first pulley shaft pass through a third slot and a first slot, and are slidably connected with the third slot and the first slot. The two ends of the second pulley shaft pass through a fourth slot and a second slot, and are slidably connected with the fourth slot and the second slot. The SMA cable is coiled around the first pulley and the second pulley in an S-shape. The left end of the SMA cable is fixedly connected to the first end plate, and the right end is fixedly connected to the second end plate. The cross-sectional area of the first end plate and the second end plate is larger than the hollow cross-sectional area of the outer steel pipe, so that the first end plate and the second end plate can block the outer steel pipe and the inner steel pipe. The left end of the SMA cable is fixed to the first end plate via a first anchoring end. The left end of the first anchoring end penetrates the first end plate and is screwed with a first anchoring nut. A first disc spring is provided on the first anchoring end between the first anchoring nut and the first end plate. The right end of the SMA cable is fixed to the second end plate via a second anchoring end. The right end of the second anchoring end penetrates the second end plate and is screwed with a second anchoring nut. A second disc spring is provided on the second anchoring end between the second anchoring nut and the second end plate. The left end of the outer steel pipe has a first U-shaped plate, and both the front and rear ends of the first end plate have a first opening for two horizontal plates of the first U-shaped plate to pass through; the right end of the inner steel pipe has a second U-shaped plate, and both the front and rear ends of the second end plate have a second opening for the second U-shaped plate to pass through. The first U-shaped plate is hinged to the first connecting frame, and the first connecting frame is hinged to the first fixed plate; the second U-shaped plate is hinged to the second connecting frame, and the second connecting frame is hinged to the second fixed plate.
[0008] Furthermore, elastic blocks are fixed at both ends of the third slot and the fourth slot of the inner steel pipe.
[0009] Furthermore, polytetrafluoroethylene plates are fixed to both the top and bottom surfaces of the inner steel pipe.
[0010] The method of small-size, large-displacement, variable stiffness, self-resetting SMA cable bridge vibration damping device is to take the elongation of the SMA cable as δ and the cable force when the elongation is δ as F(δ), where δ is a variable and F(δ) is a function. Before the stiffness is adjusted, the inner steel tube is subjected to a force F(δ) by the SMA cable applied to the second end plate. At this time, the direction of the force F(δ) is to the left. Since the inner steel tube wants to move to the right, it will push the second end plate to the right, which will then pull the SMA cable through the second disc spring and the second anchor nut. The SMA cable forms a tension force to prevent the inner steel tube from moving to the right, thus forming a force to the left. When the stiffness changes, the fourth slot of the inner steel tube moves to the right relative to the second slot of the outer steel tube, which will eventually push the second pulley shaft to move to the right; the force exerted by the SMA cable on the second pulley is 2F(δ), which will be applied to the left wall of the fourth slot through the second pulley shaft and thus transmitted to the inner steel tube; at this time, the total force on the inner steel tube is 3F(δ), realizing the multiplication of the constraint force; When the limit is reached, the first pulley shaft remains stable due to the obstruction of the first slot of the outer steel pipe, while the third slot of the inner steel pipe moves to the right relative to the first slot. Eventually, the left wall of the third slot will be obstructed by the first pulley shaft and will no longer move to the right, thus achieving the limit function.
[0011] The beneficial effects of this invention are: (1) Under large displacement requirements, the damper can avoid the problem of difficult arrangement caused by the straight arrangement of SMA cables by arranging the SMA cables in an S-shape.
[0012] (2) When the inner steel pipe moves to the left relative to the outer steel pipe, it pushes the first end plate to move to the left, thereby pulling the SMA cable and forming a constraint force. When the inner steel pipe moves to the right relative to the outer steel pipe, it pushes the second end plate 42 to move to the right, thereby pulling the SMA cable and forming a constraint force. Therefore, whether it moves to the left or the right, the SMA cable can be subjected to tension, giving full play to the performance of the SMA material.
[0013] In summary, this invention proposes a small-size, large-displacement, variable-stiffness, self-resetting, and limit-positioning SMA cable damper and method, aiming to improve structural safety and engineering applicability while ensuring seismic isolation and vibration reduction performance. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is an exploded view of the present invention; Figure 3 This is a schematic diagram of the outer steel pipe structure; Figure 4 This is a schematic diagram of the inner steel pipe structure; Figure 5 This is a CC cross-section of the time-varying stiffness state under rightward stretching; Figure 6 This is a DD cross-sectional view of the variable stiffness state under rightward stretching; Figure 7This is a cross-sectional view of the EE in the limit state when stretched to the right; Figure 8 This is a cross-sectional view of the FF in the limit state when stretched to the right; Figure 9 This is a BB cross-section view in its initial state; Figure 10 This is a schematic diagram of the installation of dampers on a bridge; Figure 11 This is a schematic diagram of the relationship between force and displacement; Figure 12 This is a schematic diagram of an inner steel tube structure with elastic blocks and polytetrafluoroethylene plates.
[0015] In the diagram: First fixing plate 11, first connecting frame 12, second fixing plate 13, second connecting frame 14, outer steel pipe 2, first slot 21, second slot 22, first U-shaped plate 23, inner steel pipe 3, third slot 31, fourth slot 32, second U-shaped plate 33, first end plate 41, first opening 411, second end plate 42, second opening 421, first pulley shaft 51, first pulley 52, second pulley shaft 54, second pulley 55, SMA cable 61, first anchoring end 62, first disc spring 63, first anchoring nut 64, second anchoring end 65, second disc spring 66, second anchoring nut 67, pier 71, cap beam 72, main beam 73, damper 74, elastic block 8, polytetrafluoroethylene plate 9. Detailed Implementation
[0016] The invention will now be further described with reference to the accompanying drawings.
[0017] Please see Figures 1-12 The present invention provides a first embodiment of a small-size, large-displacement, variable stiffness, self-resetting SMA cable bridge damper and method, including an SMA cable 61, an outer steel pipe 2, and an inner steel pipe 3 slidably connected inside the outer steel pipe 2. The outer steel pipe 2 has a first slot 21 and a second slot 22 on both its front and rear sides, and the first slot 21 and the second slot 22 are located at different heights; the inner steel pipe 3 has a third slot 31 and a fourth slot 32 on both its front and rear sides, the third slot 31 is located at the same position as the first slot 21, and the length of the third slot 31 is greater than the length of the first slot 21; the fourth slot 32 is located at the same position as the second slot 22, and the length of the fourth slot 32 is greater than the length of the second slot 22; The inner steel tube 3 is provided with a first pulley 52 and a second pulley 55, both of which are movable pulleys; the first pulley 52 is rotatably connected to the first pulley 52 shaft 51, and the second pulley 55 is rotatably connected to the second pulley 55 shaft 54; both ends of the first pulley 52 shaft 51 pass through the third slot 31 and the first slot 21, and are slidably connected with the third slot 31 and the first slot, and both ends of the second pulley 55 shaft 54 pass through the fourth slot 32 and the second slot 22, and are slidably connected with the fourth slot 32 and the second slot 22. The SMA cable 61 is coiled around the first pulley 52 and the second pulley 55 in an S-shape. This arrangement allows the damper 74 to operate under large displacement requirements without the long SMA cable 61 being laid in a straight line, thus greatly shortening the size of the damper 74 and preventing the difficulties in laying out the SMA cable 61 in a straight line. The left end of the SMA cable 61 is fixedly connected to the first end plate 41, and the right end is fixedly connected to the second end plate 42. The cross-sectional areas of both the first end plate 41 and the second end plate 42 are larger than the hollow cross-sectional area of the outer steel pipe 2, so that the first end plate 41 and the second end plate 42 can effectively block the outer steel pipe 2 and the inner steel pipe 3.
[0018] When the inner steel pipe 3 moves to the left relative to the outer steel pipe 2, it pushes the first end plate 41 to move to the left, thereby pulling the SMA cable 61 and forming a constraint force. When the inner steel pipe 3 moves to the right relative to the outer steel pipe 2, it pushes the second end plate 4242 to move to the right, thereby pulling the SMA cable 61 and forming a constraint force. Therefore, whether moving to the left or to the right, the SMA cable 61 can be subjected to tension, fully utilizing the performance of the SMA material.
[0019] The left end of the SMA cable 61 is fixed to the first end plate 41 via a first anchoring end 62. The left end of the first anchoring end 62 penetrates the first end plate 41 and is screwed with a first anchoring nut 64. A first disc spring 63 is provided on the first anchoring end 62 between the first anchoring nut 64 and the first end plate 41. The right end of the SMA cable 61 is fixed to the second end plate 42 via a second anchoring end 65. The right end of the second anchoring end 65 penetrates the second end plate 42 and is screwed with a second anchoring nut 67. A second disc spring 66 is provided on the second anchoring end 65 between the second anchoring nut 67 and the second end plate 42. The first disc spring 63 and the second disc spring 66 are used to apply preload to the SMA cable 61 to prevent it from loosening.
[0020] In the initial state, the first pulley 52, shaft 51, is located to the right of the first slot 21 of the outer steel pipe 2, and the second pulley 55, shaft 54, is located to the left of the second slot 22 of the outer steel pipe 2. Figure 9The BB cross-sectional view shows that the second pulley 55 shaft 54 is blocked by the second hole slot 22 of the outer steel pipe 2 and remains stable (in the initial state, the SMA cable 61 has a small initial tension under the tension of the first disc spring 63 and the second disc spring 66, and the SMA cable 61 will exert a force to the left on the second pulley 55 shaft 54).
[0021] Let the elongation of SMA cable 61 be δ, and the cable force when the elongation is δ be F(δ), where δ is a variable and F(δ) is a function.
[0022] Taking the stretching of the inner steel tube 3 to the right as an example. Before the stiffness change, the inner steel tube 3 is subjected to a force F(δ) applied to the second end plate 42 by the SMA cable 61. At this time, the direction of the force F(δ) is to the left. Since the inner steel tube 3 wants to move to the right, it will push the second end plate 42 to the right, which in turn pulls the SMA cable 61 through the second disc spring 66 and the second anchor nut 67. The SMA cable 61 generates a tensile force to prevent the inner steel tube 3 from moving to the right, thus generating a force to the left.
[0023] When the stiffness varies, Figure 6 In the DD cross-sectional view, the fourth slot 32 of the inner steel pipe 3 moves to the right relative to the second slot 22 of the outer steel pipe 2, ultimately pushing the shaft 54 of the second pulley 55 to move to the right. Since the second pulley 55 is a movable pulley, the force exerted by the SMA cable 61 on the second pulley 55 is 2F(δ), which is then applied to the left wall of the fourth slot 32 through the shaft 54 of the second pulley 55, thus being transmitted to the inner steel pipe 3. At this time, the total force on the inner steel pipe 3 is 3F(δ), achieving a multiplication of the constraint force.
[0024] When the limit is reached, Figure 8 In the FF cross-sectional view, the first pulley 52 shaft 51 is kept stable by the first slot 21 of the outer steel pipe 2, while the third slot 31 of the inner steel pipe 3 moves to the right relative to the first slot 21. Eventually, the left wall of the third slot 31 will be blocked by the first pulley 52 shaft 51 and will no longer move to the right, thus playing a limiting role.
[0025] The force and displacement relationship of the traditional SMA cable 61 is as follows: Figure 11 As shown by the dashed line, it presents a flag shape. The force and displacement relationship of the variable stiffness damper 74 of this invention is as follows: Figure 11 As shown by the solid line, variable stiffness is achieved at position Δ1, and limiting is achieved at position Δ2.
[0026] The left end of the outer steel pipe 2 has a first U-shaped plate 23, and both the front and rear ends of the first end plate 41 have a first opening 411 for the two horizontal plates of the first U-shaped plate 23 to pass through; the right end of the inner steel pipe 3 has a second U-shaped plate 33, and both the front and rear ends of the second end plate 42 have a second opening 421 for the second U-shaped plate 33 to pass through. The first U-shaped plate is hinged to the first connecting frame 12, and the first connecting frame 12 is hinged to the first fixed plate 11; the second U-shaped plate is hinged to the second connecting frame 14, and the second connecting frame 14 is hinged to the second fixed plate 13. During installation and operation under vibration, the damper 74 may experience slight torsion. To avoid additional internal forces on the structure of the damper 74 due to torsion, the aforementioned hinged connection method is adopted. This ensures that the damper 74 is subjected to axial force while releasing torsional deformation.
[0027] During installation, the first fixing plate 11 of the damper 74 is installed on the cap beam 72 of the pier 71, and the second fixing plate 13 is installed on the main beam 73.
[0028] Based on the previous embodiment, the present invention provides a second embodiment of a small-size, large-displacement, variable stiffness, self-resetting SMA cable bridge damper. Elastic blocks 8 are fixed at both ends of the third slot 31 and the fourth slot 32 of the inner steel tube 3 to provide a certain buffering capacity for the variable stiffness and limiting process.
[0029] Based on any of the above embodiments, the present invention provides a third embodiment of a small-size, large-displacement, variable-stiffness, self-resetting SMA cable bridge damper, wherein the top and bottom surfaces of the inner steel pipe 3 are fixed with polytetrafluoroethylene plates 9, which can reduce friction and facilitate mutual sliding between the inner steel pipe 3 and the outer steel pipe 2.
[0030] Based on any of the above embodiments, the present invention provides a fourth embodiment of a small-size, large-displacement, variable-stiffness, self-resetting SMA cable bridge damper, which can be provided with multiple sets of SMA cables 61 and their corresponding first pulleys 52 and second pulleys 55, arranged in a centrally symmetrical manner with the axes of the inner steel pipe 3 and the outer steel pipe 2 as the center, so that the damper 74 is subjected to more uniform force.
[0031] Based on any of the above embodiments, the present invention provides a first embodiment of a method for a small-size, large-displacement, variable-stiffness, self-resetting SMA cable bridge damper, wherein the elongation of the SMA cable is δ, and the cable force when the elongation is δ is F(δ), where δ is a variable and F(δ) is a function. Before the stiffness is adjusted, the inner steel tube is subjected to a force F(δ) by the SMA cable applied to the second end plate. At this time, the direction of the force F(δ) is to the left. Since the inner steel tube wants to move to the right, it will push the second end plate to the right, which will then pull the SMA cable through the second disc spring and the second anchor nut. The SMA cable forms a tension force to prevent the inner steel tube from moving to the right, thus forming a force to the left. When the stiffness changes, the fourth slot of the inner steel tube moves to the right relative to the second slot of the outer steel tube, which will eventually push the second pulley shaft to move to the right; the force exerted by the SMA cable on the second pulley is 2F(δ), which will be applied to the left wall of the fourth slot through the second pulley shaft and thus transmitted to the inner steel tube; at this time, the total force on the inner steel tube is 3F(δ), realizing the multiplication of the constraint force; When the limit is reached, the first pulley shaft remains stable due to the obstruction of the first slot of the outer steel pipe, while the third slot of the inner steel pipe moves to the right relative to the first slot. Eventually, the left wall of the third slot will be obstructed by the first pulley shaft and will no longer move to the right, thus achieving the limit function.
[0032] The above description is only a preferred embodiment of the present invention and should not be construed as a limitation of this application. All equivalent changes and modifications made in accordance with the scope of the patent application of the present invention should be covered by the present invention.
Claims
1. A small-size, large-displacement, variable-stiffness, self-resetting SMA cable-stayed bridge damper, characterized in that, Includes SMA cable, outer steel pipe, and inner steel pipe that is slidably connected inside the outer steel pipe; The outer steel pipe has a first slot and a second slot on both its front and rear sides, and the first slot and the second slot are located at different heights; the inner steel pipe has a third slot and a fourth slot on both its front and rear sides, the third slot is located at the same position as the first slot, and the length of the third slot is greater than the length of the first slot; the fourth slot is located at the same position as the second slot, and the length of the fourth slot is greater than the length of the second slot. The inner steel tube is provided with a first pulley and a second pulley. The first pulley is rotatably connected to a first pulley shaft, and the second pulley is rotatably connected to a second pulley shaft. The two ends of the first pulley shaft pass through a third slot and a first slot, and are slidably connected with the third slot and the first slot. The two ends of the second pulley shaft pass through a fourth slot and a second slot, and are slidably connected with the fourth slot and the second slot. The SMA cable is coiled around the first pulley and the second pulley in an S-shape. The left end of the SMA cable is fixedly connected to the first end plate, and the right end is fixedly connected to the second end plate. The cross-sectional area of the first end plate and the second end plate is larger than the hollow cross-sectional area of the outer steel pipe, so that the first end plate and the second end plate can block the outer steel pipe and the inner steel pipe. The left end of the SMA cable is fixed to the first end plate via a first anchoring end. The left end of the first anchoring end penetrates the first end plate and is screwed with a first anchoring nut. A first disc spring is provided on the first anchoring end between the first anchoring nut and the first end plate. The right end of the SMA cable is fixed to the second end plate via a second anchoring end. The right end of the second anchoring end penetrates the second end plate and is screwed with a second anchoring nut. A second disc spring is provided on the second anchoring end between the second anchoring nut and the second end plate. The left end of the outer steel pipe has a first U-shaped plate, and both the front and rear ends of the first end plate have a first opening for two horizontal plates of the first U-shaped plate to pass through; the right end of the inner steel pipe has a second U-shaped plate, and both the front and rear ends of the second end plate have a second opening for the second U-shaped plate to pass through. The first U-shaped plate is hinged to the first connecting frame, and the first connecting frame is hinged to the first fixed plate; the second U-shaped plate is hinged to the second connecting frame, and the second connecting frame is hinged to the second fixed plate.
2. The small-size, large-displacement, variable-stiffness, self-resetting SMA cable-stayed bridge damper according to claim 1, characterized in that, Elastic blocks are fixed at both ends of the third slot and the fourth slot of the inner steel pipe.
3. The small-size, large-displacement, variable-stiffness, self-resetting SMA cable-stayed bridge damper according to claim 1, characterized in that, Polytetrafluoroethylene (PTFE) plates are fixed to both the top and bottom surfaces of the inner steel pipe.
4. A method for using a small-size, large-displacement, variable-stiffness, self-resetting SMA cable-stayed bridge damper, characterized in that... Using the small-size, large-displacement, variable-stiffness, self-resetting SMA cable bridge damper as described in any one of claims 1-3, the elongation of the SMA cable is δ, and the cable force when the elongation is δ is F(δ), where δ is a variable and F(δ) is a function. Before the stiffness is adjusted, the inner steel tube is subjected to a force F(δ) by the SMA cable applied to the second end plate. At this time, the direction of the force F(δ) is to the left. Since the inner steel tube wants to move to the right, it will push the second end plate to the right, which will then pull the SMA cable through the second disc spring and the second anchor nut. The SMA cable forms a tension force to prevent the inner steel tube from moving to the right, thus forming a force to the left. When the stiffness changes, the fourth slot of the inner steel tube moves to the right relative to the second slot of the outer steel tube, which will eventually push the second pulley shaft to move to the right; the force exerted by the SMA cable on the second pulley is 2F(δ), which will be applied to the left wall of the fourth slot through the second pulley shaft and thus transmitted to the inner steel tube; at this time, the total force on the inner steel tube is 3F(δ), realizing the multiplication of the constraint force; When the limit is reached, the first pulley shaft remains stable due to the obstruction of the first slot of the outer steel pipe, while the third slot of the inner steel pipe moves to the right relative to the first slot. Eventually, the left wall of the third slot will be obstructed by the first pulley shaft and will no longer move to the right, thus achieving the limit function.