A wind tunnel test device for simulating nonlinear vibration of bridge structures

Abstract

The present application belongs to the technical field of bridge wind tunnel test device, and provides a kind of wind tunnel test device simulating nonlinear vibration of bridge structure, including rigid model, rigid rod, rigid circular arc suspension arm, linear tensile spring, nonlinear elastic element and light high-strength fine rope.Nonlinear elastic element can adopt cable structure, membrane structure, nonlinear tensile spring, mechanical super material or superstructure.By designing the nonlinear stiffness characteristics of nonlinear elastic element, the layout mode and the combination mode of linear tensile spring, various target nonlinear stiffness modes can be realized to carry out large amplitude vertical torsional coupled flutter test of bridge structure under nonlinear stiffness.In the process of large amplitude vibration of model, the center hanging point of nonlinear elastic element and linear tensile spring can always maintain vertical displacement and deformation, and the device can ensure stable stiffness, damping, mass and mass moment characteristics.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge wind tunnel test devices, and in particular relates to a wind tunnel test device for simulating nonlinear vibration of bridge structures. Background Art

[0002] Long-span bridges experience nonlinear structural stiffness effects during wind-induced large-amplitude flutter. However, existing large-amplitude nonlinear flutter tests on bridge girder segment models primarily assume constant structural stiffness, failing to accurately reflect the nonlinear flutter response of the structure under realistic conditions. This, in turn, affects the accuracy of wind resistance assessments. Sébastien Maheux et al. developed a free-vibration wind tunnel test apparatus that accounts for geometrically nonlinear structural stiffness by deploying initially tilted springs (Nonlinear Wind Tunnel Tests of Cable-Supported Bridges. Journal of Structural Engineering, 2023, 14910: 04023137). However, tilted springs are inevitably affected by sag, causing localized vibrations during model vibration. This results in uncontrollable nonlinear stiffness and unstable damping. Furthermore, the system's mass and mass moment cannot be guaranteed to be constant, leading to experimental errors. Therefore, there is an urgent need to develop a wind tunnel test apparatus that can simulate the nonlinear vibration of bridge structures. Summary of the Invention

[0003] The technical problem addressed by this invention is to provide a wind tunnel testing apparatus capable of achieving coupled vertical and torsional nonlinear stiffness and ensuring large-amplitude, stable, low-damping free vibration, in order to meet the requirements for large-amplitude nonlinear stiffness free vibration of bridge girder segment models during wind tunnel testing. The apparatus comprises a rigid model, a rigid rod, a rigid circular-arc boom, a lightweight, high-strength string, a linear tension spring, and a nonlinear elastic element.

[0004] The technical solution of the present invention:

[0005] A wind tunnel test apparatus for simulating nonlinear vibration of a bridge structure includes a rigid model 1, a rigid rod 2, a rigid circular arc boom 3, a first linear tension spring 4, a first nonlinear elastic element 5, a first lightweight high-strength string 6, a second linear tension spring 7, a second nonlinear elastic element 8, a second lightweight high-strength string 9, and a third lightweight high-strength string 10.

[0006] The rigid rods 2 are fixed at both ends of the rigid model 1, and the torsion center line of the rigid model 1 is ensured to be collinear with the axis of the rigid rod 2. The free end of the rigid rod 2 vertically passes through the center of the rigid circular arc boom 3 and is fixed thereto. The rigid circular arc boom 3 is a symmetrical structure, which is mainly composed of circular arc rods connected at both ends of a straight rod, and the outer wall of the circular arc rod is provided with a groove. According to the actual test conditions, the first linear tension spring 4 and the first nonlinear elastic element 5 are combined in series or in parallel, the second linear tension spring 7 and the second nonlinear elastic element 8 are combined in series or in parallel, or only the first nonlinear elastic element 5 and the second nonlinear elastic element 8 are arranged. The first linear tension spring 4 and the second linear tension spring 7 are eliminated. When a series combination is adopted, two groups of the first linear tension spring 4, the first nonlinear elastic element 5, and the first lightweight high-strength string 6 are provided on one side of the rigid model 1 and are symmetrically arranged on both sides of the rigid circular arc boom 3. The upper end of the first linear tension spring 4 is connected to the central suspension point of the first nonlinear elastic element 5, and the lower end of the first linear tension spring 4 is connected to the upper end of the first lightweight high-strength string 6. The first lightweight high-strength string 6 extends vertically downward, is tangent to the outer wall of the rigid circular arc boom 3, and is wound in its groove. The lower end of the first lightweight high-strength string 6 is fixed to the bottom of the rigid circular arc boom 3. There are two groups of second linear tension springs 7, second nonlinear elastic elements 8 and second lightweight high-strength thin ropes 9 on one side of the rigid model 1, which are symmetrically arranged on both sides of the rigid circular arc boom 3; the lower end of the second linear tension spring 7 is connected to the central hanging point of the second nonlinear elastic element 8, and the upper end of the second linear tension spring 7 is connected to the lower end of the second lightweight high-strength thin rope 9. The second lightweight high-strength thin rope 9 is vertically tangent to the outer wall of the rigid circular arc boom 3 and wound in its groove, and the upper end of the second lightweight high-strength thin rope 9 is fixed to the top of the rigid circular arc boom 3; in this way, it is ensured that the rigid model 1 and the rigid circular arc boom 3 are in the process of vertical and torsional coupled free vibration. The linear tension spring 4, the first nonlinear elastic element 5, the second linear tension spring 7 and the second nonlinear elastic element 8 only undergo vertical deformation and do not vibrate laterally; the third lightweight and high-strength string 10 is connected to the free end of the rigid rod 2, and both ends of the third lightweight and high-strength string 10 are fixed to the wind tunnel wall, thereby limiting the lateral vibration of the rigid model 1 during the wind-induced large-scale coupled free vibration process; the nonlinear stiffness of the wind tunnel test device mainly depends on the nonlinear stiffness characteristics and layout of the first nonlinear elastic element 5 and the second nonlinear elastic element 8, and their corresponding combination with the first linear tension spring 4 and the second linear tension spring 7.

[0007] The diameter of the rigid circular arc boom 3 is determined according to several parameters such as the mass, mass moment of inertia, and ratio of torsional frequency to vertical frequency of the rigid model 1 , and the arc radian of the rigid circular arc boom 3 is determined according to the torsional amplitude of the rigid model 1 .

[0008] The first linear tensile spring 4 and the first nonlinear elastic element 5, and the second linear tensile spring 7 and the second nonlinear elastic element 8 are combined in parallel, connecting the rigid rod 2 to two different diameter and concentric rigid circular arc hangers, then connecting the first rigid circular arc hanger 3-1 to the first linear tensile spring 4 and the second linear tensile spring 7 through the first light and high strength rope 6 and the second light and high strength rope 9 respectively, and connecting the second rigid circular arc hanger 3-2 to the first nonlinear elastic element 5 and the second nonlinear elastic element 8 through another first light and high strength rope 6 and another second light and high strength rope 9 respectively; when only the first nonlinear elastic element 5 and the second nonlinear elastic element 8 are used to provide the stiffness of the wind tunnel test device, only the first light and high strength rope 6 and the second light and high strength rope 9 are used to connect the rigid circular arc hanger 3 to the first nonlinear elastic element 5 and the second nonlinear elastic element 8 respectively.

[0009] The first nonlinear elastic element 5 and the second nonlinear elastic element 8 adopt a cable structure, a membrane structure, a nonlinear tensile spring, a mechanical metamaterial or a superstructure; when a cable structure or a membrane structure is used, the shape of the cable structure and the membrane structure is centrally symmetric, and the central hanging point is at the center of the cable structure and the membrane structure. The vertical nonlinear stiffness of the cable structure or the membrane structure is related to the material composition, shape, thickness and prestress thereof; when a nonlinear tensile spring is used, the vertical nonlinear stiffness thereof is related to the shape of the nonlinear tensile spring, as well as the cross-sectional shape, pitch and number of turns of the nonlinear tensile spring wire; when a mechanical metamaterial or a superstructure is used, the vertical nonlinear stiffness thereof is related to the properties of the unit materials, the unit structure and the unit arrangement combination method inside; the central hanging points of the first nonlinear elastic element 5 and the second nonlinear elastic element 8 only have vertical displacement under the action of vertical concentrated force, and do not have lateral displacement, and should not bear eccentric vertical force.

[0010] When the first nonlinear elastic element 5 and the second nonlinear elastic element 8 adopt a cable structure or a membrane structure, the first-order derivative of the vertical stiffness of the first nonlinear elastic element 5 with respect to the vertical downward displacement of the hanging point is positive, and the first-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the hanging point is positive; at this time, for the working condition that the target vertical stiffness of the wind tunnel test device increases with the increase of the vertical downward displacement of the rigid model 1 and decreases with the increase of the vertical upward displacement, only the first nonlinear elastic element 5 needs to be arranged; for the working condition that the target vertical stiffness of the wind tunnel test device increases with the increase of the vertical downward displacement of the rigid model 1 and decreases with the increase of the vertical upward displacement, 1 decreases with the increase of the vertical downward displacement and increases with the increase of the vertical upward displacement, only the second nonlinear elastic element 8 needs to be arranged; for the working condition that the target vertical stiffness of the wind tunnel test device increases with the increase of the absolute value of the vertical displacement of the rigid model 1, the first nonlinear elastic element 5 and the second nonlinear elastic element 8 need to be arranged, and the second-order derivative of the vertical stiffness of the first nonlinear elastic element 5 with respect to the vertical downward displacement of the hanging point is positive, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the hanging point is positive; for the target vertical stiffness of the wind tunnel test device For the working condition that the target torsional stiffness of the wind tunnel test device increases with the increase of the absolute value of the torsional displacement of the rigid model 1, the first nonlinear elastic element 5 and the second nonlinear elastic element 8 need to be arranged, and the second-order derivative of the vertical stiffness of the first nonlinear elastic element 5 with respect to the vertical downward displacement of the hanging point is negative, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the hanging point is negative; for the working condition that the target torsional stiffness of the wind tunnel test device increases with the increase of the absolute value of the torsional displacement of the rigid model 1, the first nonlinear elastic element 5 and / or the second nonlinear elastic element 8 need to be arranged, and the first nonlinear elastic element The second-order derivative of the vertical stiffness of component 5 with respect to the vertical downward displacement of the hanging point is positive, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the hanging point is positive; for the working condition where the target torsional stiffness of the wind tunnel test device decreases with the increase of the absolute value of the torsional displacement of the rigid model 1, the first nonlinear elastic element 5 and / or the second nonlinear elastic element 8 needs to be arranged, and the second-order derivative of the vertical stiffness of the first nonlinear elastic element 5 with respect to the vertical downward displacement of the hanging point is negative, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the hanging point is negative.

[0011] When the first nonlinear elastic element 5 and the second nonlinear elastic element 8 are nonlinear tension springs, mechanical metamaterials or metastructures, the first-order derivative of the vertical stiffness of the first nonlinear elastic element 5 with respect to the vertical downward displacement of the suspension point can be positive or negative, and its second-order derivative can also be positive or negative. The first-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the suspension point can be positive or negative, and its second-order derivative can also be positive or negative. Therefore, the layout scheme of the first nonlinear elastic element 5 and the second nonlinear elastic element 8 can be more flexible.

[0012] The first nonlinear elastic element 5 and the second nonlinear elastic element 8 can be combined with different nonlinear elastic elements to achieve more types of nonlinear stiffness modes.

[0013] The first lightweight high-strength string 6, the second lightweight high-strength string 9 and the third lightweight high-strength string 10 have the characteristics of light weight, high strength, tensile strength, no bending and torsion resistance, and the material is not limited; the length of the first lightweight high-strength string 6 and the second lightweight high-strength string 9 should be determined according to parameters such as the vertical and torsional amplitude of the rigid model 1 and the diameter of the rigid circular arc boom 3; the third lightweight high-strength string 10 should be long enough so that its influence on the vertical and torsional stiffness of the device can be ignored.

[0014] The beneficial effects of the present invention are as follows: (1) various forms of vertical and torsional coupled nonlinear stiffness can be achieved through the series and parallel combination of the nonlinear elastic element and the linear tension spring, so as to carry out large-amplitude vertical torsional coupled flutter tests under the nonlinear stiffness of the bridge structure; (2) during the large-amplitude vibration of the model, the central suspension point of the nonlinear elastic element and the linear tension spring can always maintain vertical displacement and deformation, and the device can ensure stable stiffness, damping, mass and mass moment characteristics; (3) the device is low-cost, easy to process, efficient and feasible. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the structural diagram of the test device when the nonlinear elastic element and the linear tension spring are connected in series.

[0016] Figure 2 This is the structural diagram of the test device when the nonlinear elastic element and the linear tension spring are connected in parallel.

[0017] Figure 3 This is the structural diagram of the test device when only nonlinear elastic elements are arranged.

[0018] Figure 4 This is a structural diagram of the test device when only the first nonlinear elastic element is deployed.

[0019] Figure 5 This is a diagram of the test device structure when only the second nonlinear elastic element is deployed.

[0020] In the figure: 1 rigid model; 2 rigid rod; 3, 3-1, 3-2 rigid arc boom; 4 first linear tension spring; 5 first nonlinear elastic element; 6 first lightweight high-strength thin rope; 7 second linear tension spring; 8 second nonlinear elastic element; 9 second lightweight high-strength thin rope; 10 third lightweight high-strength thin rope. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is described in detail below in conjunction with the technical solutions and drawings.

[0022] like Figure 1 As shown, a wind tunnel test device for simulating nonlinear vibration of a bridge structure includes a rigid model 1, a rigid rod 2, a rigid circular arc boom 3, a first linear tension spring 4, a first nonlinear elastic element 5, a first lightweight high-strength string 6, a second linear tension spring 7, a second nonlinear elastic element 8, a second lightweight high-strength string 9, and a third lightweight high-strength string 10;

[0023] The rigid rods 2 are fixed at both ends of the rigid model 1, and the torsion center line of the rigid model 1 is ensured to be collinear with the axis of the rigid rod 2. The free end of the rigid rod 2 vertically passes through the center of the rigid circular arc boom 3 and is fixed thereto. The rigid circular arc boom 3 is a symmetrical structure, which is mainly composed of circular arc rods connected at both ends of a straight rod, and the outer wall of the circular arc rod is provided with a groove. According to the actual test conditions, the first linear tension spring 4 and the first nonlinear elastic element 5 are combined in series or in parallel, the second linear tension spring 7 and the second nonlinear elastic element 8 are combined in series or in parallel, or only the first nonlinear elastic element 5 and the second nonlinear elastic element 8 are arranged. The first linear tension spring 4 and the second linear tension spring 7 are eliminated. When a series combination is adopted, two groups of the first linear tension spring 4, the first nonlinear elastic element 5, and the first lightweight high-strength string 6 are provided on one side of the rigid model 1 and are symmetrically arranged on both sides of the rigid circular arc boom 3. The upper end of the first linear tension spring 4 is connected to the central suspension point of the first nonlinear elastic element 5, and the lower end of the first linear tension spring 4 is connected to the upper end of the first lightweight high-strength string 6. The first lightweight high-strength string 6 extends vertically downward, is tangent to the outer wall of the rigid circular arc boom 3, and is wound in its groove. The lower end of the first lightweight high-strength string 6 is fixed to the bottom of the rigid circular arc boom 3. There are two groups of second linear tension springs 7, second nonlinear elastic elements 8 and second lightweight high-strength thin ropes 9 on one side of the rigid model 1, which are symmetrically arranged on both sides of the rigid circular arc boom 3; the lower end of the second linear tension spring 7 is connected to the central hanging point of the second nonlinear elastic element 8, and the upper end of the second linear tension spring 7 is connected to the lower end of the second lightweight high-strength thin rope 9. The second lightweight high-strength thin rope 9 is vertically tangent to the outer wall of the rigid circular arc boom 3 and wound in its groove, and the upper end of the second lightweight high-strength thin rope 9 is fixed to the top of the rigid circular arc boom 3; in this way, it is ensured that the rigid model 1 and the rigid circular arc boom 3 are in the process of vertical and torsional coupled free vibration. The linear tension spring 4, the first nonlinear elastic element 5, the second linear tension spring 7 and the second nonlinear elastic element 8 only undergo vertical deformation and do not vibrate laterally; the third lightweight and high-strength string 10 is connected to the free end of the rigid rod 2, and both ends of the third lightweight and high-strength string 10 are fixed to the wind tunnel wall, thereby limiting the lateral vibration of the rigid model 1 during the wind-induced large-scale coupled free vibration process; the nonlinear stiffness of the wind tunnel test device mainly depends on the nonlinear stiffness characteristics and layout of the first nonlinear elastic element 5 and the second nonlinear elastic element 8, and their corresponding combination with the first linear tension spring 4 and the second linear tension spring 7.

[0024] The diameter of the rigid circular arc boom 3 is determined according to several parameters such as the mass, mass moment of inertia and ratio of torsional frequency to vertical frequency of the rigid model 1 , and the arc radian of the rigid circular arc boom 3 is determined according to the torsional amplitude of the rigid model 1 .

[0025] like Figure 2 and Figure 3 As shown, when the first linear tension spring 4 and the first nonlinear elastic element 5, as well as the second linear tension spring 7 and the second nonlinear elastic element 8 are combined in parallel, the rigid rod 2 is connected to two concentric rigid circular arc suspension arms of different diameters, and then the first rigid circular arc suspension arm 3-1 is directly connected to the first linear tension spring 4 and the second linear tension spring 7 respectively through the first lightweight high-strength string 6 and the second lightweight high-strength string 9, and then the second rigid circular arc suspension arm 3-2 is directly connected to the first nonlinear elastic element 5 and the second nonlinear elastic element 8 respectively through another first lightweight high-strength string 6 and another second lightweight high-strength string 9; when only the first nonlinear elastic element 5 and the second nonlinear elastic element 8 are used to provide the stiffness of the wind tunnel test device, it is only necessary to directly connect the rigid circular arc suspension arm 3 to the first nonlinear elastic element 5 and the second nonlinear elastic element 8 through the first lightweight high-strength string 6 and the second lightweight high-strength string 9 respectively.

[0026] The first nonlinear elastic element 5 and the second nonlinear elastic element 8 are constructed using cable structures, membrane structures, nonlinear tension springs, mechanical metamaterials, or superstructures. When using a cable or membrane structure, the shape of the cable or membrane structure is centrally symmetrical, with the central suspension point located at the center of the cable or membrane structure. The vertical nonlinear stiffness of the cable or membrane structure is related to its material composition, shape, thickness, and prestress. When using a nonlinear tension spring, its vertical nonlinear stiffness is related to the nonlinear tension spring's external shape, as well as the cross-sectional shape, internode spacing, and number of turns of the nonlinear tension spring wire. When using a mechanical metamaterial or superstructure, its vertical nonlinear stiffness is related to the internal unit material properties, unit structure, and unit arrangement and combination. The central suspension points of the first nonlinear elastic element 5 and the second nonlinear elastic element 8 only undergo vertical displacement under the action of a vertical concentrated force, not lateral displacement, and should not be subjected to eccentric vertical forces.

[0027] like Figure 1 、 Figure 4 and Figure 5As shown, when the first nonlinear elastic element 5 and the second nonlinear elastic element 8 adopt a cable structure or a membrane structure, the first-order derivative of the vertical stiffness of the first nonlinear elastic element 5 with respect to the vertical downward displacement of the hanging point is positive, and the first-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the hanging point is positive; at this time, for the working condition that the target vertical stiffness of the wind tunnel test device increases with the increase of the vertical downward displacement of the rigid model 1 and decreases with the increase of the vertical upward displacement, only the first nonlinear elastic element 5 needs to be arranged; for the working condition that the target vertical stiffness of the wind tunnel test device increases with the increase of the vertical downward displacement of the rigid model 1 and decreases with the increase of the vertical upward displacement, 1 decreases with the increase of the vertical downward displacement and increases with the increase of the vertical upward displacement, only the second nonlinear elastic element 8 needs to be arranged; for the working condition that the target vertical stiffness of the wind tunnel test device increases with the increase of the absolute value of the vertical displacement of the rigid model 1, the first nonlinear elastic element 5 and the second nonlinear elastic element 8 need to be arranged, and the second-order derivative of the vertical stiffness of the first nonlinear elastic element 5 with respect to the vertical downward displacement of the hanging point is positive, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the hanging point is positive; for the target vertical stiffness of the wind tunnel test device For the working condition that the target torsional stiffness of the wind tunnel test device increases with the increase of the absolute value of the torsional displacement of the rigid model 1, the first nonlinear elastic element 5 and the second nonlinear elastic element 8 need to be arranged, and the second-order derivative of the vertical stiffness of the first nonlinear elastic element 5 with respect to the vertical downward displacement of the hanging point is negative, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the hanging point is negative; for the working condition that the target torsional stiffness of the wind tunnel test device increases with the increase of the absolute value of the torsional displacement of the rigid model 1, the first nonlinear elastic element 5 and / or the second nonlinear elastic element 8 need to be arranged, and the first nonlinear elastic element The second-order derivative of the vertical stiffness of component 5 with respect to the vertical downward displacement of the hanging point is positive, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the hanging point is positive; for the working condition where the target torsional stiffness of the wind tunnel test device decreases with the increase of the absolute value of the torsional displacement of the rigid model 1, the first nonlinear elastic element 5 and / or the second nonlinear elastic element 8 needs to be arranged, and the second-order derivative of the vertical stiffness of the first nonlinear elastic element 5 with respect to the vertical downward displacement of the hanging point is negative, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the hanging point is negative.

[0028] When the first nonlinear elastic element 5 and the second nonlinear elastic element 8 adopt nonlinear tension springs, mechanical metamaterials or metastructures, the first-order derivative of the vertical stiffness of the first nonlinear elastic element 5 with respect to the vertical downward displacement of the suspension point can be positive or negative, and its second-order derivative can also be positive or negative. The first-order derivative of the vertical stiffness of the second nonlinear elastic element 8 with respect to the vertical upward displacement of the suspension point can be positive or negative, and its second-order derivative can also be positive or negative; therefore, the layout scheme of the first nonlinear elastic element 5 and the second nonlinear elastic element 8 can be more flexible.

[0029] The first nonlinear elastic element 5 and the second nonlinear elastic element 8 can be combined with different nonlinear elastic elements to achieve more types of nonlinear stiffness modes.

[0030] The first lightweight high-strength string 6, the second lightweight high-strength string 9 and the third lightweight high-strength string 10 have the characteristics of light weight, high strength, tensile strength, no bending and torsion resistance, and the material is not limited; the length of the first lightweight high-strength string 6 and the second lightweight high-strength string 9 should be determined according to parameters such as the vertical and torsional amplitude of the rigid model 1 and the diameter of the rigid circular arc boom 3; the third lightweight high-strength string 10 should be long enough so that its influence on the vertical and torsional stiffness of the device can be ignored.

[0031] The above description is merely an example of a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any equivalent changes, modifications, or variations made by a person skilled in the art using the technical solution of the present invention to the above examples shall still fall within the scope of the technical solution of the present invention.

Claims

1. A wind tunnel test device for simulating nonlinear vibration of a bridge structure, characterized in that: The wind tunnel test device comprises a rigid model (1), a rigid rod (2), a rigid circular arc boom (3), a first linear tension spring (4), a first nonlinear elastic element (5), a first lightweight high-strength string (6), a second linear tension spring (7), a second nonlinear elastic element (8), a second lightweight high-strength string (9) and a third lightweight high-strength string (10); The rigid model (1) is fixed with rigid rods (2) at both ends, and the torsion center line of the rigid model (1) is ensured to be colinear with the axis of the rigid rod (2). The free end of the rigid rod (2) vertically passes through the center of the rigid circular arc boom (3) and is fixed thereto. The rigid circular arc boom (3) is a symmetrical structure, which is mainly composed of circular arc rods connected at both ends of a straight rod, and the outer wall surface of the circular arc rod is provided with a groove. According to the actual test working condition requirements, the first linear tension spring (4) and the first nonlinear elastic element (5) are combined in series or in parallel, the second linear tension spring (7) and the second nonlinear elastic element (8) are combined in series or in parallel, or only the first nonlinear elastic element (5) and the second nonlinear elastic element (8) are arranged. The first linear tension spring (4) and the second linear tension spring (7) are eliminated; when a series combination is adopted, the first linear tension spring (4), the first nonlinear elastic element (5) and the first light high-strength thin rope (6) on one side of the rigid model (1) are in total two groups, and are symmetrically arranged on both sides of the rigid circular arc suspension arm (3); the upper end of the first linear tension spring (4) is connected to the central suspension point of the first nonlinear elastic element (5), the lower end of the first linear tension spring (4) is connected to the upper end of the first light high-strength thin rope (6), the first light high-strength thin rope (6) is vertically downward and tangential to the outer wall surface of the rigid circular arc suspension arm (3) and is wound in its groove, and the lower end of the first light high-strength thin rope (6) is fixed to the bottom of the rigid circular arc suspension arm (3). The second linear tension spring (7), the second nonlinear elastic element (8) and the second light high-strength string (9) on one side of the rigid model (1) are provided in two groups, which are symmetrically arranged on both sides of the rigid circular arc suspension arm (3); the lower end of the second linear tension spring (7) is connected to the central suspension point of the second nonlinear elastic element (8), the upper end of the second linear tension spring (7) is connected to the lower end of the second light high-strength string (9), the second light high-strength string (9) is vertically upward and tangential to the outer wall of the rigid circular arc suspension arm (3) and is wound in its groove, and the upper end of the second light high-strength string (9) is fixed to the top of the rigid circular arc suspension arm (3); thereby ensuring that the rigid model (1) and the rigid circular arc suspension arm (3) are in the process of vertical and torsional coupled free vibration. The first linear tension spring (4), the first nonlinear elastic element (5), the second linear tension spring (7) and the second nonlinear elastic element (8) only undergo vertical deformation and do not vibrate laterally; the third lightweight high-strength string (10) is connected to the free end of the rigid rod (2), and both ends of the third lightweight high-strength string (10) are fixed to the wind tunnel wall, thereby limiting the lateral vibration of the rigid model (1) during the wind-induced large-scale coupled free vibration process; the nonlinear stiffness of the wind tunnel test device mainly depends on the nonlinear stiffness characteristics, layout method and corresponding combination method of the first nonlinear elastic element (5) and the second nonlinear elastic element (8) with the first linear tension spring (4) and the second linear tension spring (7).

2. The wind tunnel test device according to claim 1, characterized in that: When the first linear tension spring (4) and the first nonlinear elastic element (5) are combined in parallel, and when the second linear tension spring (7) and the second nonlinear elastic element (8) are combined in parallel, the rigid rod (2) is connected to two concentric rigid circular arc suspension arms of different diameters: a first rigid circular arc suspension arm (3-1) and a second rigid circular arc suspension arm (3-2). The first rigid circular arc suspension arm (3-1) is directly connected to the first linear tension spring (4) and the second linear tension spring (7) respectively through a first lightweight high-strength thin rope (6) and a second lightweight high-strength thin rope (9). The second rigid circular arc suspension arm (3-2) is directly connected to the first nonlinear elastic element (5) and the second nonlinear elastic element (8) respectively through another first lightweight high-strength thin rope (6) and another second lightweight high-strength thin rope (9).

3. The wind tunnel test device according to claim 1, characterized in that: When only the first nonlinear elastic element (5) and the second nonlinear elastic element (8) are used to provide the stiffness of the wind tunnel test device, it is only necessary to directly connect the rigid circular arc boom (3) with the first nonlinear elastic element (5) and the second nonlinear elastic element (8) via the first lightweight high-strength thin rope (6) and the second lightweight high-strength thin rope (9), respectively.

4. The wind tunnel test device according to claim 1, characterized in that: The first nonlinear elastic element (5) and the second nonlinear elastic element (8) adopt a cable structure, a membrane structure, a nonlinear tensile spring, a mechanical metamaterial or a superstructure; when a cable structure or a membrane structure is adopted, the shape of the cable structure and the membrane structure is centrally symmetrical, and the central suspension point is located at the center of the cable structure and the membrane structure; the vertical nonlinear stiffness of the cable structure or the membrane structure is related to its material composition, shape, thickness, and prestress; when a nonlinear tensile spring is adopted, its vertical nonlinear stiffness is related to the shape of the nonlinear tensile spring, and is also related to the cross-sectional shape, internode spacing, and number of turns of the nonlinear tensile spring wire; when a mechanical metamaterial or a superstructure is adopted, its vertical nonlinear stiffness is related to the unit material properties, unit structure, and unit arrangement and combination mode inside the nonlinear elastic element (5) and the central suspension point of the second nonlinear elastic element (8) only undergoes vertical displacement under the action of a vertical concentrated force, but does not undergo lateral displacement, and should not be subjected to eccentric vertical force.

5. The wind tunnel test device according to claim 1, characterized in that: When the first nonlinear elastic element (5) and the second nonlinear elastic element (8) adopt a cable structure or a membrane structure, the first-order derivative of the vertical stiffness of the first nonlinear elastic element (5) with respect to the vertical downward displacement of the hanging point is positive, and the first-order derivative of the vertical stiffness of the second nonlinear elastic element (8) with respect to the vertical upward displacement of the hanging point is positive; at this time, for the working condition that the target vertical stiffness of the wind tunnel test device increases with the increase of the vertical downward displacement of the rigid model (1) and decreases with the increase of the vertical upward displacement, only the first nonlinear elastic element (5) needs to be arranged; for the working condition that the target vertical stiffness of the wind tunnel test device increases with the increase of the vertical downward displacement of the rigid model (1) and decreases with the increase of the vertical upward displacement, ) decreases with the increase of the vertical downward displacement and increases with the increase of the vertical upward displacement, it is only necessary to arrange the second nonlinear elastic element (8); for the working condition that the target vertical stiffness of the wind tunnel test device increases with the increase of the absolute value of the vertical displacement of the rigid model (1), it is necessary to arrange the first nonlinear elastic element (5) and the second nonlinear elastic element (8), and the second derivative of the vertical stiffness of the first nonlinear elastic element (5) with respect to the vertical downward displacement of the hanging point is positive, and the second derivative of the vertical stiffness of the second nonlinear elastic element (8) with respect to the vertical upward displacement of the hanging point is positive; for the working condition that the target vertical stiffness of the wind tunnel test device increases with the increase of the absolute value of the vertical displacement of the rigid model (1), it is necessary to arrange the first nonlinear elastic element (5) and the second nonlinear elastic element (8), and the second derivative of the vertical stiffness of the first nonlinear elastic element (5) with respect to the vertical downward displacement of the hanging point is positive, and the second derivative of the vertical stiffness of the second nonlinear elastic element (8) with respect to the vertical upward displacement of the hanging point is positive; For the working condition that the vertical displacement of the rigid model (1) decreases with the increase of the absolute value of the vertical displacement, the first nonlinear elastic element (5) and the second nonlinear elastic element (8) need to be arranged, and the second-order derivative of the vertical stiffness of the first nonlinear elastic element (5) with respect to the vertical downward displacement of the hanging point is negative, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element (8) with respect to the vertical upward displacement of the hanging point is negative; for the working condition that the target torsional stiffness of the wind tunnel test device increases with the increase of the absolute value of the torsional displacement of the rigid model (1), the first nonlinear elastic element (5) and / or the second nonlinear elastic element (8) need to be arranged, and the first nonlinear elastic element The second-order derivative of the vertical stiffness of the component (5) with respect to the vertical downward displacement of the hanging point is positive, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element (8) with respect to the vertical upward displacement of the hanging point is positive; for the working condition in which the target torsional stiffness of the wind tunnel test device decreases with the increase of the absolute value of the torsional displacement of the rigid model (1), the first nonlinear elastic element (5) and / or the second nonlinear elastic element (8) need to be arranged, and the second-order derivative of the vertical stiffness of the first nonlinear elastic element (5) with respect to the vertical downward displacement of the hanging point is negative, and the second-order derivative of the vertical stiffness of the second nonlinear elastic element (8) with respect to the vertical upward displacement of the hanging point is negative.

6. The wind tunnel test device according to claim 1, characterized in that: When the first nonlinear elastic element (5) and the second nonlinear elastic element (8) are nonlinear extension springs, mechanical metamaterials or metastructures, the first-order derivative of the vertical stiffness of the first nonlinear elastic element (5) with respect to the vertical downward displacement of the suspension point is positive or negative, and the second-order derivative thereof is also positive or negative; the first-order derivative of the vertical stiffness of the second nonlinear elastic element (8) with respect to the vertical upward displacement of the suspension point is positive or negative, and the second-order derivative thereof is also positive or negative.

7. The wind tunnel test device according to claim 1, characterized in that: The first nonlinear elastic element (5) and the second nonlinear elastic element (8) are combined using different nonlinear elastic elements, thereby realizing more types of nonlinear stiffness modes.

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