Wind tunnel test device and test method for multi-vertical-degree-of-freedom segment model

Abstract

The invention discloses a wind tunnel test device and test method for a multi-vertical-degree-of-freedom segment model, and belongs to the technical field of bridge wind tunnel tests.The test device comprises a bridge segment model and supports symmetrically arranged on the two sides of the bridge segment model, and the supports are provided with two parallel transverse rods; a first supporting rod and a second supporting rod are slidably installed on the support in the longitudinal direction, the first supporting rod is fixedly connected with the bridge segment model through a connecting rod, a first spring is installed between the first supporting rod and a supporting transverse rod located at the top of the support, and a second spring is fixedly installed between the first supporting rod and the second supporting rod. A third spring is installed between the second supporting rod and the supporting cross rod located at the bottom of the support, a threaded rod is fixedly connected to the bottom of the second supporting rod, and a balancing weight is connected to the threaded rod in a threaded mode. The weight of the whole sliding structure is adjusted by adjusting the number of the balancing weights, so that the multi-vertical vibration frequency is adjusted.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge wind tunnel tests, and in particular relates to a multi-vertical degree-of-freedom segment model wind tunnel test device. Background Art

[0002] Wind tunnel test is an important means to study the wind resistance of structures. The wind tunnel facilities in the wind tunnel test can generate a wind field with specific wind speed and direction and other wind characteristics, and apply them to the test model. At present, there are two main types of wind tunnel test models. One is a full-size aeroelastic model. This model is restored by reducing the entire structure to a larger scale. It can simulate the multi-modal vibration characteristics of the structure. However, due to the space limitation of the wind tunnel test, the scale of the aeroelastic model is relatively small, so the wind tunnel test results are more likely to be distorted. The other is a segmental model, which only studies the key parts of the actual structure affected by wind loads, usually a section of a bridge main beam or a section of a cable. It can simulate a certain order of modal vibration characteristics of the actual structure. This model has a larger scale and the test results are more realistic. The test results use sensors and other measuring equipment to record the test data such as the response of the segmental model under the action of the wind field, which can be used for structural optimization design and safety assessment. In order to ensure the validity of the wind tunnel test results, the segmental model needs to ensure similarity with the aerodynamic shape and dynamic characteristics of the actual model. The aerodynamic shape of the structure is mainly related to the appearance of the structure. The appearance of the model is processed according to a certain scale ratio with the actual structure to achieve an aerodynamic shape similar effect. The structural dynamic characteristics mainly refer to the modal frequency, modal mass and modal damping ratio of the structure. The frequency and mass of the model can be adjusted by changing the stiffness of the spring in the segment model and the additional mass of the segment model, and the damping device can be installed on the deformation stroke of the model to simulate the structural damping.

[0003] Vortex-induced vibration is caused by eddies formed by fluid on the surface of non-streamlined objects. Under the action of the fluid, the structure is subjected to a pulsating force orthogonal to the direction of the fluid velocity. When the period of this pulsating force is close to the natural vibration period of the structure, vortex-induced vibration will occur. At present, there are many studies on vortex-induced vibration of structures that are susceptible to wind loads, such as large-span bridges and bridge cables. Vortex-induced vibration is closely related to the vibration frequency of the structure. When the frequency distribution of each modal order of the structure is relatively dense, in order to more accurately evaluate and predict the impact of vortex-induced vibration on the structure, researchers need to consider multiple vibration modes of the structure, because the vortex vibration responses of structures with similar modes will affect each other. The traditional vertical single-degree-of-freedom wind tunnel model cannot simulate this multi-modal situation. Based on the above requirements, the present invention provides a wind tunnel test segment model that can simulate multiple vertical modes. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a wind tunnel test device and test method for a multi-vertical degree of freedom segment model, which are used to simulate the wind tunnel test of the multi-vertical modal free vibration of the bridge segment model.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a wind tunnel test device for a multi-vertical degree-of-freedom segment model, comprising a bridge segment model and a bracket symmetrically arranged on both sides of the bridge segment model, wherein two mutually parallel cross bars are arranged on the bracket, and a vertical adjustment mechanism is arranged between the two support cross bars, and the vertical adjustment mechanism comprises a first support rod and a second support rod installed along the longitudinal sliding direction on the bracket, the first support rod and the bridge segment model are fixedly connected by a connecting rod, and a first spring is installed between the first support rod and the support cross bar located at the top of the bracket, a second spring is fixedly installed between the first support rod and the second support rod, and a third spring is installed between the second support rod and the support cross bar located at the bottom of the bracket, a screw is fixedly connected to the bottom of the second support rod, and a counterweight is threadedly connected to the screw.

[0007] Furthermore, the second support rods on both sides of the bridge segment model are fixedly connected by a long connecting rod.

[0008] Furthermore, the first spring, the second spring and the third spring are always in a stretched state.

[0009] Furthermore, the number of the first springs and the third springs are both two, the two first springs and the two third springs are symmetrically arranged about the axis of the second spring, the second spring is fixedly installed in the middle of the first support rod and the second support rod, and the axes of the first spring and the third spring located on the same side of the second spring are located on the same straight line.

[0010] Furthermore, sliders are slidably installed on the support cross bar, the first support bar and the second support bar, and the first spring and the third spring are respectively fixedly connected between two relatively arranged sliders. Sliding the slider can adjust the distance between the two first springs and the distance between the two third springs.

[0011] Furthermore, a bidirectional screw is installed with a limited rotation inside the support cross bar, and the two sliders on the support cross bar are respectively threadedly connected to the opposite threads of the bidirectional screw. A connecting rod is fixedly connected between the sliders on the two support cross bars on the same side of the second spring, and the connecting rod is fixedly connected to the slider on the same side of the second spring on the first support rod and the second support rod.

[0012] Furthermore, a connecting rod on the same side of the second spring is arranged on the inner circles of the first spring and the third spring.

[0013] Furthermore, a rack is installed on the side wall of the bracket for limited sliding, and the end of the bidirectional screw extending from the supporting cross bar is fixedly connected to a gear meshing with the rack. Sliding the rack can make the two gears slide synchronously. A threaded rod is installed on the side wall of the bracket for limited sliding. The threaded rod is threadedly connected to the rack. Rotating the threaded rod can make the rack slide along the side wall of the bracket for limited sliding.

[0014] Furthermore, the first support rod and the second support rod are fixedly connected with a slide plate on the side away from the bridge segment model, and the bracket is fixedly connected with a vertical rod, and the slide plate is slidably installed on the vertical rod.

[0015] A test method for a wind tunnel test device of a multi-vertical degree of freedom segment model, comprising:

[0016] Compute the modal frequencies of the two-degree-of-freedom model when accounting for the mass of the spring:

[0017]

[0018]

[0019] In the formula, w 1 and w 2 are the first and second order vibration frequencies, 0 1 is the stiffness of the first spring 6, 0 2 is the stiffness of the first spring 7, k 3 is the stiffness of the first spring 8, m 2 is the mass of bridge segment model 1, m 1 is the overall mass of the vertical adjustment mechanism;

[0020] The modal mass M1 and M2 of the two-degree-of-freedom model when calculating the spring mass are:

[0021]

[0022] Where {φ} 1 、{φ} 2 The vibration mode of the two-degree-of-freedom model is: [M] is the mass matrix of the two-degree-of-freedom model, M f is the spring mass, and They refer to the ratio of the amplitude of the first-order mode and the second-order mode additional degree of freedom to the amplitude of the main degree of freedom respectively;

[0023] When calculating n degrees of freedom, that is, n-2 second support rods 4 are arranged between the first support rod 3 and the second support rod 4 and a long connecting rod 11 connecting two opposite second support rods 4, the modal frequency w and modal vector φ of the structure are as follows, where n>2:

[0024]

[0025] In the formula, m 1 Indicates the quality of the segment model, m 2 …m n Denotes each additional mass, k 1 …k n Indicates the stiffness of each spring.

[0026] The beneficial effects of the present invention are:

[0027] When the bridge segment model undergoes vertical vibration, the present invention drives the first support rod to slide vertically through the connecting rod, thereby enabling the first support rod and the second support rod to slide vertically between two supporting cross bars through the first spring, the second spring, and the third spring. By adjusting the number of counterweights and the spring stiffness, the multiple vertical vibration frequencies can be adjusted.

[0028] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0030] Figure 1 It is a schematic diagram of the overall structure of the test device according to an embodiment of the present invention;

[0031] Figure 2 It is a schematic diagram of the installation of the vertical adjustment mechanism of an embodiment of the present invention;

[0032] Figure 3 This is a mechanical model of the two vertical degree devices according to an embodiment of the present invention.

[0033] The markings in the attached drawings are as follows: bridge segment model 1, bracket 2, supporting cross bar 201, vertical bar 202, first supporting rod 3, second supporting rod 4, connecting rod 5, first spring 6, second spring 7, third spring 8, screw 9, counterweight 10, long connecting rod 11, slide plate 12, slider 13, bidirectional screw 14, connecting rod 15, rack 16, gear 17, threaded rod 18. DETAILED DESCRIPTION

[0034] like Figures 1 to 3As shown, the present invention provides a wind tunnel test device for a multi-vertical degree of freedom segment model, comprising: a bridge segment model 1 and a bracket 2 symmetrically arranged on both sides of the bridge segment model 1, wherein two mutually parallel supporting cross bars 201 are arranged on the bracket 2, and a vertical adjustment mechanism is arranged between the two supporting cross bars 201, and the vertical adjustment mechanism comprises a first support rod 3 and a second support rod 4 installed along the longitudinal sliding direction on the bracket 2, the first support rod 3 and the second support rod 4 are arranged between the two supporting cross bars 201, the first support rod 3 and the bridge segment model 1 are fixedly connected by a connecting rod 5, and a first spring 6 is installed between the first support rod 3 and the supporting cross bar 201 located at the top of the bracket 2, a second spring 7 is fixedly installed between the first support rod 3 and the second support rod 4, a third spring 8 is installed between the second support rod 4 and the supporting cross bar 201 located at the bottom of the bracket 2, and a screw rod 9 is fixedly connected to the bottom of the second support rod 4, and a counterweight block 10 is threadedly connected to the screw 9.

[0035] In the present scheme, the bridge segment model 1 is a blunt-body section segment model. The blunt-body section segment model can be various irregular bridge section models, or it can be a regular cable cylinder or a building rectangular section model. The bridge segment model 1 serves as the object of wind load action. When the bridge segment model 1 vibrates vertically, the first support rod 3 is driven to slide vertically through the connecting rod 5, so that the first support rod 3 and the second support rod 4 are vertically slid between the two supporting cross bars 201 through the first spring 6, the second spring 7, and the third spring 8. By adjusting the number of counterweights 10 and adjusting the spring stiffness, the multiple vertical vibration frequencies can be adjusted.

[0036] In one embodiment of the present invention, the second support rods 4 on both sides of the bridge segment model 1 are fixedly connected by a long connecting rod 11 to ensure the synchronization of the sliding of the second support rods 4 on both sides of the bridge segment model 1 .

[0037] In one embodiment of the present invention, the first spring 6, the second spring 7 and the third spring 8 are always in a stretched state to ensure that the springs will not bend or deform when stretched or shortened.

[0038] In one embodiment of the present invention, the number of the first spring 6 and the third spring 8 are both two, the two first springs 6 and the two third springs 8 are symmetrically arranged about the axis of the second spring 7, the second spring 7 is fixedly mounted in the middle of the first support rod 3 and the second support rod 4, and the axes of the first spring 6 and the third spring 8 on the same side of the second spring 7 are located on the same straight line, so as to ensure the stability of the structure and facilitate the judgment of the vibration frequency.

[0039] In one embodiment of the present invention, a slider 13 is slidably mounted on the support crossbar 201, the first support bar 3 and the second support bar 4, the first spring 6 and the third spring 8 are respectively fixedly connected between two oppositely arranged sliders 13, and sliding the slider 13 can adjust the distance between the two first springs 6 and the distance between the two third springs 8, so as to facilitate model assembly.

[0040] In one embodiment of the present invention, a bidirectional screw 14 is installed in the support cross bar 201 for limited rotation, and the two sliders 13 on the support cross bar 201 are respectively threadedly connected to the opposite threads of the bidirectional screw 14, and a connecting rod 15 is fixedly connected between the sliders 13 on the two support cross bars 201 on the same side of the second spring 7, and the connecting rod 15 is fixedly connected to the sliders 13 on the first support rod 3 and the second support rod 4 on the same side of the second spring 7.

[0041] In this solution, by rotating the bidirectional screw 14, the two sliders 13 on the same level can slide relative to each other, thereby driving the two connecting rods 15 to slide relative to each other, thereby ensuring the stability of the spacing adjustment of the two first springs 6 and the two third springs 8.

[0042] In one embodiment of the present invention, the connecting rod 15 on the same side of the second spring 7 is arranged on the inner circle of the first spring 6 and the third spring 8 to enhance the structural stability and prevent the first spring 6 and the third spring 8 from bending and deformation.

[0043] In one embodiment of the present invention, a rack 16 is installed on the side wall of the bracket 2 for limited sliding, and a gear 17 meshing with the rack 16 is fixedly connected to the end of the bidirectional screw 14 extending out of the supporting cross bar 201, and sliding the rack 16 can make the two gears 17 slide synchronously; a threaded rod 18 is installed on the side wall of the bracket 2 for limited sliding, and the threaded rod 18 is threadedly connected to the rack 16, and rotating the threaded rod 18 can make the rack 16 limited sliding. This allows the operator to adjust the spacing between the two first springs 6 and the spacing between the two third springs 8 as a whole.

[0044] In one embodiment of the present invention, the first support rod 3 and the second support rod 4 are fixedly connected with a slide plate 12 on the side away from the bridge segment model 1, and the bracket 2 is fixedly connected with a vertical rod 202. The slide plate 12 is slidably installed on the vertical rod 202 to ensure the stability of the vertical sliding of the first support rod 3 and the second support rod 4.

[0045] A test method for a wind tunnel test device of a multi-vertical degree of freedom segment model, comprising:

[0046] Compute the modal frequencies of the two-degree-of-freedom model when accounting for the mass of the spring:

[0047]

[0048] In the formula, w 1 and w 2 are the first and second order vibration frequencies, k 1 is the stiffness of the first spring 6, k 2 is the stiffness of the second spring 7, k 3 is the stiffness of the third spring 8, m 2 is the mass of bridge segment model 1, m 1 It is the overall mass of the vertical adjustment mechanism.

[0049] The modal mass M1 and M2 of the two-degree-of-freedom model when calculating the spring mass are:

[0050]

[0051] Where {φ} 1 、{φ} 2 The vibration mode of the two-degree-of-freedom model is: [M] is the mass matrix of the two-degree-of-freedom model, M f is the spring mass; and They refer to the ratio of the amplitude of the first-order mode and the second-order mode additional degree of freedom to the amplitude of the main degree of freedom respectively;

[0052] If it is extended to n (n>2) degrees of freedom, when calculating n degrees of freedom, that is, n-2 second support rods 4 are set between the first support rod 3 and the second support rod 4 and a long connecting rod 11 connecting two opposite second support rods 4, the modal frequency w and modal vector φ of the structure are as follows, where n>2:

[0053]

[0054] Where m 1 Indicates the quality of the segment model, m 2 …m n Denotes each additional mass, k 1 …k n Represents the stiffness of each spring. The modal frequency and modal mass of the model can be obtained through the above equations.

[0055] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A wind tunnel test device for a multi-vertical degree of freedom segment model, comprising a bridge segment model and brackets symmetrically arranged on both sides of the bridge segment model, characterized in that: The bracket is provided with two cross bars parallel to each other, and a vertical adjustment mechanism is provided between the two support cross bars. The vertical adjustment mechanism includes a first support bar and a second support bar installed on the bracket along the longitudinal sliding direction, the first support bar is fixedly connected to the bridge segment model by a connecting rod, and a first spring is installed between the first support bar and the support cross bar located at the top of the bracket, a second spring is fixedly installed between the first support bar and the second support bar, and a third spring is installed between the second support bar and the support cross bar located at the bottom of the bracket, a screw is fixedly connected to the bottom of the second support bar, and a counterweight is threadedly connected to the screw.

2. The wind tunnel test device for a multi-vertical degree of freedom segment model according to claim 1, characterized in that: The second support rods on both sides of the bridge segment model are fixedly connected by a long connecting rod.

3. The wind tunnel test device for a multi-vertical degree of freedom segment model according to claim 2, characterized in that: The first spring, the second spring and the third spring are always in a stretched state.

4. The wind tunnel test device for a multi-vertical degree of freedom segment model according to claim 3, characterized in that: The number of the first springs and the third springs are both two, the two first springs and the two third springs are symmetrically arranged about the axis of the second spring, the second spring is fixedly installed in the middle of the first support rod and the second support rod, and the axes of the first spring and the third spring located on the same side of the second spring are located on the same straight line.

5. The wind tunnel test device for a multi-vertical degree of freedom segment model according to claim 4, characterized in that: The support cross bar, the first support bar and the second support bar are all slidably mounted with sliders, the first spring and the third spring are respectively fixedly connected between two relatively arranged sliders, and sliding the sliders can adjust the distance between the two first springs and the distance between the two third springs.

6. The wind tunnel test device for a multi-vertical degree of freedom segment model according to claim 5, characterized in that: A bidirectional screw is installed in the supporting cross bar for limited rotation, and the two sliders on the supporting cross bar are respectively threadedly connected to the opposite threads of the bidirectional screw. A connecting rod is fixedly connected between the sliders on the two supporting cross bars on the same side of the second spring, and the connecting rod is fixedly connected to the slider on the same side of the second spring on the first supporting rod and the second supporting rod.

7. The wind tunnel test device for a multi-vertical degree of freedom segment model according to claim 6, characterized in that: The connecting rod on the same side of the second spring is arranged on the inner circles of the first spring and the third spring.

8. The wind tunnel test device for a multi-vertical degree of freedom segment model according to claim 7, characterized in that: The side wall of the bracket is installed with a rack for limited sliding. The end of the bidirectional screw extending from the supporting cross bar is fixedly connected to a gear meshing with the rack. Sliding the rack can make the two gears slide synchronously. The side wall of the bracket is rotatably installed with a threaded rod, which is threadedly connected to the rack. Rotating the threaded rod can make the rack slide along the side wall of the bracket.

9. The wind tunnel test device for a multi-vertical degree of freedom segment model according to claim 8, characterized in that: The first support rod and the second support rod are both fixedly connected with a slide plate on the side away from the bridge segment model. The bracket is fixedly connected with a vertical rod, and the slide plate is slidably installed on the vertical rod.

10. The test method of the wind tunnel test device of the multi-vertical degree of freedom segment model according to any one of claims 1 to 9, characterized in that: include: Compute the modal frequencies of the two-degree-of-freedom model when accounting for the mass of the spring: Wherein, w1 and w2 are the first and second order vibration frequencies respectively, k1 is the stiffness of the first spring, k2 is the stiffness of the second spring, k3 is the stiffness of the third spring, m2 is the mass of the bridge segment model 1, and m1 is the overall mass of the vertical adjustment mechanism; The modal mass M1 and M2 of the two-degree-of-freedom model when calculating the spring mass are: Where {φ}1 and {φ}2 are the vibration modes of the two-degree-of-freedom model: [M] is the mass matrix of the two-degree-of-freedom model, M f is the spring mass, and They refer to the ratio of the amplitude of the first-order mode and the second-order mode additional degree of freedom to the amplitude of the main degree of freedom respectively; When calculating n degrees of freedom, the modal frequency w and modal vector φ of the structure are as follows, where n>2: Where m1 represents the quality of the segment model, m2…m n Denotes the individual additional masses, k1…k n Indicates the stiffness of each spring.

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