Large-amplitude free vibration wind tunnel test device with three degrees of freedom

Abstract

The invention provides a large-amplitude free vibration wind tunnel test device with three degrees of freedom, and belongs to the technical field of wind tunnel test devices for bridges. The large-amplitude free vibration wind tunnel test device which is a large-amplitude free vibration wind tunnel test device with three degrees of freedom coupling for bridges comprises a rigid test model, a rigidround bar, a rigid suspension arm, arc blocks with grooves, light high-strength strings, linear extension springs, fixed pulleys and a bearing. The large-amplitude free vibration wind tunnel test device has the advantages that the problem of incapability of guaranteeing the linear vertical rigidity, the linear torsional rigidity and the linear lateral rigidity due to down warping of lateral springs horizontally arranged in the traditional vibration test device with three degrees of freedom and lateral tilting of vertical springs under large-amplitude conditions can be effectively solved by the aid of the large-amplitude free vibration wind tunnel test device; the large-amplitude free vibration wind tunnel test device is simple and is convenient to mount, initial attack angles are easy toadjust, down warping and tilting of the springs are prevented in vibration procedures, accordingly, the linear rigidity and stable vibration frequencies of systems still can be guaranteed even in large-amplitude vibration procedures, and research on the three-dimensional nonlinear pneumatic characteristics of the bridges becomes possible under large-amplitude conditions.

Description

technical field [0001] The invention relates to a three-degree-of-freedom free vibration wind tunnel test device that can realize a large amplitude of bridge rigidity model and can guarantee linear vertical stiffness, linear torsional stiffness and linear lateral stiffness. The vertical and torsional coupled large-amplitude free vibration system composed of light and high-strength string, vertical linear tension spring and fixed pulley, and the lateral vibration system composed of light and high-strength string, bearing, vertical linear tension spring and fixed pulley The free vibration system converts the three-degree-of-freedom coupled large-amplitude free vibration of the bridge rigid model into the vertical free expansion and contraction of the linear spring, and uses the linear tensile stiffness of the spring, rigid arc boom and fixed pulley to realize the vertical and lateral Linear translational stiffness and linear torsional stiffness. Since the system mass and mass m...

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Problems solved by technology

However, the traditional system has the following problems: (1) the lateral tension spring will sag due to its own weight, and the level cannot be guaranteed, so the linear stiffness cannot be guaranteed; (2) when the model vibrates vertically and torsionally, the lateral tension spring also cannot It will produce vertical vibration and increase the damping of the system; (3) when the model is vibrating vertically and torsionally, the influence of the lateral spring on the modal quality of the system is not easy to determine; (4) when the model is vibrating laterally and torsionally, the vertical The tension spring will also vibrate laterally, increasing the damping of the system; (5) When the model undergoes lateral and torsional vibration, the influence of the vertical tension spring on the modal quality of the system is not easy to determine

(6) When the torsional amplitude is large, the vertical tension spring has an obvious lateral inclination, and the geometric stiffness of the spring does not satisfy the linear condition. Therefore, the vertical and torsional stiffness of the coupled vibration system no longer remain constant, but are related to the amplitude. Therefore, it caused unacceptable and obvious error to the follow-up test results.

However, for the study of large-amplitude torsional vibration, such as when the old Tacoma bridge was destroyed by wind, the torsional amplitude reached an astonishing 35°, which cannot be simulated by the traditional free three-degree-of-freedom coupled free vibration test device

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