Method for identifying variable boundary cable force of medium or long cable

Abstract

The invention discloses a method for identifying a variable boundary cable force of a medium or long cable. The method comprises the following steps of: performing unit discreteness on the cable, dividing the cable into n units (n is in a range of 40 to 400), and calculating a unit rigidity matrix [K]e and a mass matrix [M]e of each unit according to formulas (1) to (2); then arranging rubber cushion blocks on the cable to form external restraint, wherein the number of the rubber cushion blocks is 2 to 6 and the mounting number of the rubber cushion blocks is determined according to the length of the tested cable; and after the total rigidity matrix [K] and the total mass matrix [M] are determined, solving a characteristic value equation l[K]-omega2[M]l=0 of natural vibration frequency ofa cable structure by adopting an iteration method to obtain the cable force T. Under the condition that the cable force is not changed, if the boundary condition of the cable is changed, the frequency of the cable is changed, and the equation of the frequency of the cable and the cable force is changed along with the change of the boundary condition of the cable, so the condition that the frequency of the cable cannot be tested under complex environments is solved, and meanwhile the frequency of the cable is in an interval capable of being tested by the conventional instrument by regulating the boundary condition.

Description

technical field [0001] The invention relates to a cable force identification method of a stressed medium-length cable, more specifically, a cable force identification method for cable-stayed cables of cable-stayed bridges, arch bridge suspenders, arch bridge tie rods, and main cables of suspension bridges in engineering applications. force recognition method. technical background [0002] With the vigorous and rapid development of engineering construction, cables are widely used in engineering construction due to their simple structure, beautiful appearance, and economic advantages, especially in bridge construction, such as cable-stayed bridge cable, arch bridge crane, etc. Cable rods, arch bridge tie rods, and suspension bridge anchors are all cable rods. The cable force of the cable is related to the safety of the structure. In the application of the cable, the cable force is generally very large. For example, in a cable-stayed bridge, the cable can even withstand hundre...

AI Technical Summary

Problems solved by technology

The identification of the frequency adopts the refined FFT technology, and the frequency resolution of the cable is increased to above 0.001HZ after the refinement. It can be said that the test accuracy of the natural frequency fully meets the engineering requirements. This method is widely used and has great application value. However, the current frequency The method has the following deficiencies: 1) only simple boundaries can be considered; 2) due to the influence of other structural frequencies, it is not easy to test the frequency of some ultra-low frequency or ultra-high frequency cables, that is, it is not easy to separate the tested frequencies; 3 ) is difficult to remove the specific influence value of each influencing factor (other structural vibration, environment, own parameters) in the cable

However, if the relationship between frequency and boundary conditions is taken into account: if the relationship equation between cable force and frequency changes, the frequency will inevitably change when the cable force remains unchanged. It can be known from field tests on long cables that when in the middle of the cable When constraints are applied, the frequency of the cable increases

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