Method for measuring bridge structure dynamic displacement and vibration frequency

Abstract

A method for measuring bridge structure dynamic displacement and vibration frequency is provided. The method includes the following steps of: (1) establishing a bridge structure vibration field monitoring system so as to synchronously acquire vibration displacement and global navigation satellite system (GNSS) time; (2) performing coordinate system projection conversion which comprises the steps of calculating projection parameters between a local coordinate system and a bridge independent coordinate system and transforming measured structure vibration coordinate projection into the bridge independent coordinate system; (3) filtering bridge structure vibration displacement gross errors; (4) re-sampling vibration displacement through using a linear interpolation method; (5) separating quasi-static parts from dynamic parts in displacement by using a Chebyshev filter; and (6) analyzing vibration signal frequency spectrums through using a fast Fourier method. The method of the invention has the advantages of non-contact property, high precision, high reliability, high automation and the like.

Description

technical field [0001] The invention mainly relates to the technical field of bridge structure health monitoring, in particular to a method for measuring dynamic displacement and vibration frequency of bridge structures. Background technique [0002] Monitoring and diagnosing the dynamic performance of bridge structures, as well as timely damage assessment and safety warning are of great significance to improving bridge operation efficiency and avoiding heavy casualties and property losses. Among them, quasi-static displacement, dynamic displacement and vibration frequency are important parameters to reflect the dynamic performance of bridge structures. Moreover, monitoring the long-period quasi-static displacement and short-period dynamic displacement in bridge structural vibration is the difficulty of bridge structural health monitoring at present. [0003] Conventional instruments for measuring dynamic parameters of bridge structures are mainly accelerometers, but they h...

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Problems solved by technology

[0004] (1) The accelerometer can only measure the vibration signal of the bridge structure through a contact method. For difficult-to-reach parts such as bridge towers, the operation is very inconvenient and the measurement is difficult

[0005] (2) Use the accelerometer to directly measure the acceleration of the structural vibration. After integration, only the relative displacement of the structural vibration can be obtained, and the absolute displacement cannot be obtained, which makes it difficult for the accelerometer to perform continuous monitoring for a long time

[0006] (3) During the monitoring process, a high-pass filter needs to be used to eliminate the trend item generated in the two integration processes. The accelerometer can only measure the short-period dynamic displacement in the structural vibration, and cannot measure the long-period quasi-static displacement.

[0007] In the prior art, there is another automatic total station, which has the advantages of automatic target recognition, automatic target tracking, automatic measurement, automatic recording, and high measurement accuracy, and its measurement accuracy reaches millimeter level, even submillimeter Level accuracy, so it is often used for high-precision deformation monitoring of engineering structures such as slopes, dams, bridges, and tunnels, but it cannot be used for dynamic deformation and vibration frequency measurement of bridge structures. The main reasons are:

[0008] (1) Due to low time resolution, omission of measurement data, noise interference and other reasons, with the current measurement method, the automatic total station can only measure the quasi-static displacement of the engineering structure, and cannot measure the short-period dynamic displacement and vibration frequency

[0009] (2) Since the automatic total station uses the electrical signal generated by the quartz crystal oscillating circuit to time the time, its time accuracy is difficult to meet the requirements of structural vibration measurement

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