Measuring method of basic natural frequency of cable by combining sinusoidal exciter and video instrument

Abstract

The invention relates to a stay cable fundamental natural frequency of vibration measurement method in combination with a sine vibration exciter and a video instrument and belongs to the technical field of civil engineering in order to solve a problem that a conventional measurement means cannot meet a technical requirement for a short stay cable. The method comprises a step a of estimating the range [fD, fU] of the fundamental natural frequency of vibration f1 of a measured stay cable by using a theoretical formula; a step b of installing an exciter at the one-half length of the measured staycable, and installing the video instrument on a fixed floor to observe the vibration displacement at the one-half length a of the measured stay cable and at the quarter length b of the measured staycable; a step c of observing the vibration displacement at the one-half length a of the measured stay cable and at the quarter length b of the measured stay cable by using the video instrument; and astep d of determining the excitation frequency at the moment as the fundamental natural frequency of vibration of the stay cable according to a ratio of the displacements at the two positions. The stay cable fundamental natural frequency of vibration measurement method in combination with the sine vibration exciter and the video instrument can improve the measurement accuracy of the fundamental natural frequency of vibration of the stay cable.

Description

technical field [0001] The invention relates to a method for measuring the basic natural frequency of a cable, in particular to a method for measuring the basic natural frequency of a cable combined with a sinusoidal vibrator and a video instrument, and belongs to the technical field of civil engineering. Background technique [0002] Cable system bridges mainly transmit and distribute force through cables, and cables are the main force-bearing components of cable system bridges. The basic natural frequency of the cable (hereinafter referred to as the fundamental frequency) is an important index for the construction control of the cable system bridge and the evaluation of the normal service state of the bridge, and it is also an important parameter for identifying the force of the cable. [0003] The accuracy of cable fundamental frequency measurement is affected by many factors, such as test methods, tools, observation instruments and so on. At present, the common measurem...

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Problems solved by technology

[0004] There are problems in the actual engineering application of the above measurement methods: when environmental excitation is used, it is difficult to excite the first-order vibration of the cable for the short cable environmental excitation, so it is impossible to measure the fundamental frequency of the cable; , it is difficult to accurately judge whether the cable has resonated through naked eye observation, and the signal measured by the acceleration sensor contains a lot of noise, and it is difficult to judge the resonance

Therefore, for shorter cables, the existing measurement methods cannot meet the technical requirements

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