Method for determining basic frequency of stay cable when testing cable tension of cable stayed bridge by using vibration method

A cable-stayed bridge cable and fundamental frequency technology, applied in the field of bridge structure, can solve the problems of difficulty in directly obtaining the first natural vibration frequency of the cable, difficult to arrange the acceleration sensor, limited first-order vibration energy, etc., so as to save data analysis and processing time. , the effect of reducing the influence of human experience and improving the accuracy of results

Active Publication Date: 2013-09-04
TSINGHUA UNIV
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Problems solved by technology

[0003] Due to the limitations of on-site measurement conditions and the arrangement of measuring points, when the vibration frequency method is used to measure the strength of cables in cable-stayed bridges, it is generally difficult to arrange the acceleration sensor at the midpoint of the cable length, usually near the bridge deck. The distance between the cable anchorage ends is usually about 1 / 10 to 1 / 30 of the cable length. The measured dynamic response of the cable is mainly based on the high-order mode shape of the cable, and the first-order vibration energy is limited. It is difficult to directly obtain the first natural frequency of the cable ( fundamental frequency), and the size of the sampling frequency of the acceleration signal and the change of the filter range during signal analysis and processing will affect the dynamic analysis results, resulting in the frequency corresponding to the most prominent peak on the spectrum curve in the measured acceleration data processing results may not be correct. fundamental frequency, but multiple higher order frequencies and even some imaginary part reflection frequencies due to filtering
[0004] In addition, due to the influence of various factors in practice, the frequency difference corresponding to adjacent peaks on the spectrum curve is not completely equal, and often not necessarily equal to the fundamental frequency. Due to the influence of the stagnation point, there will be a jump phenomenon in the power spectrum in the frequency spectrum of this point. The frequency corresponding to the peak in the power spectrum density diagram may not be in multiples. At this time, the measured data will be directly processed by the frequency difference method. lead to wrong results
The new fundamental frequency method also has the problem of large amount of calculation

Method used

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  • Method for determining basic frequency of stay cable when testing cable tension of cable stayed bridge by using vibration method
  • Method for determining basic frequency of stay cable when testing cable tension of cable stayed bridge by using vibration method
  • Method for determining basic frequency of stay cable when testing cable tension of cable stayed bridge by using vibration method

Examples

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Embodiment 1

[0041] A cable-stayed bridge in Wuxi is a prestressed cable-stayed bridge with single tower and single cable plane, and the span composition is: 75m+145m. The width of the bridge deck is 33m, and the height of the main girder is 2.8m. The main girder of the main span is made of steel box girder, and the main girder of the side span is made of prestressed concrete girder. The stay cables are arranged in a fan shape and are assembled by cold cast anchors and stay cables. The stay cables are made of plastic-coated parallel steel wire bundles, the steel wires are φ7 galvanized high-strength steel wires, and the sheath is double-layered. Black HDPE with colored HDPE outer layer.

[0042] In order to ensure the safety of the bridge during the operation phase, a health monitoring system based on wireless sensor technology was deployed on the bridge to monitor signals such as the acceleration response of box girders and cables.

[0043]The acceleration sensor of the cable is installe...

example example 2

[0054] Using the new fundamental frequency method, frequency difference method and the comprehensive frequency difference method proposed in this paper, Zhao Xingkui et al. , 2011, (02)] analyzed and calculated the test results of No. 16 cable in the upstream of Zhaobaoshan Bridge in Ningbo City.

[0055] The cable fundamental frequency values ​​obtained by the new fundamental frequency method and the frequency difference method are 0.88Hz and 0.89Hz respectively, and the errors of the cable design fundamental frequency 0.86Hz are 2.3% and 3.5%, respectively. Process the measured frequency according to the calculation process of the comprehensive frequency difference method: first obtain f i = 4.4Hz, f j = 2.5Hz, f k = 5.2Hz. Secondly, calculate the initial value of fundamental frequency, N=2, f=0.89Hz. Then judge the order f i / f=4.94≈5, f j / f=2.81≈3, f k / f=5.84≈6. Finally, the cable fundamental frequency (f i / i+f j / j+f k / k) / 3=0.86Hz, which is consistent with ...

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Abstract

The invention provides an integrated frequency difference method of a cable stayed bridge cable tension test. The method comprises the following steps: firstly, reading three frequency values fi, fj and fk which are corresponding to a first peak, a second peak and a third peak in an auto-power frequency spectrum graph of a tested cable actual measurement acceleration time history; secondly, obtaining a fundamental frequency initial value f by utilizing the three frequency values corresponding to the three peaks; thirdly, determining a possible order corresponding to each frequency; finally, determining basic frequency fv and cable tension T. According to the invention, calculation is simple, operation is carried out according to a process, other complex determination and processing processes are not needed, result accuracy is raised, technology difficulty in a cable tension test is substantially reduced, by employing the method, high efficiency is realized, data analysis processing time can be saved, test cost is reduced, and economy is good.

Description

technical field [0001] The invention belongs to the field of bridge structures, and relates to a method for determining the fundamental frequency of a cable when measuring the cable force of a cable-stayed bridge by a vibration method, in particular to a method for determining the fundamental frequency of a cable when measuring the cable force of a cable-stayed bridge by a vibration method. Background technique [0002] Cables are important stress-bearing components of cable-stayed bridges, and the magnitude of the cable force controls the distribution of internal forces and the change of bridge shape of the cable-stayed bridge. The cable has the characteristics of small rigidity, light weight, low damping, and easy vibration. The measurement of the cable force of the cable-stayed bridge is very important for the cable-stayed bridge in the construction period and in the completed state. The Frequency Vibration Method (Frequency Vibration Method) is a general method in cable...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01L5/04G01R23/16
Inventor 赵作周孙江波
Owner TSINGHUA UNIV
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