A Study On Cable Parameters Identification Based On Vibration Method And Development Of Wireless Sensor

For cable with small sag, consider cable flexural rigidity, boundary rotational and spring restraint stiffness, the method to identify cable parameters by various modes of frequencies, and the method to calculate cable modal frequency by given cable parameters, are studied in this paper. Based on the acceleration time history curve collected by Imote2 remote sensor, a software is developed to identify peak frequency and its mode automatically, and then identify cable tension and other parameters, to increase efficiency in cable tension test.(1)Aimed at cable that are clamped at both ends, clamped at one end simply supported at other end, only consider rotational restraint stiffness, only consider spring restraint stiffness, consider both rotational and spring restraint stiffness, these 5 conditions, frequency equation of free vibration on each boundary condition is derived. After the analysis of the boundary condition of the bulk cable strands derived from main cable of suspension bridge, conclusion is made that this case is included in the last boundary condition case mentioned above. After mathematical manipulation of the frequency equation, the objective function suitable for iteration according to dichotomy method is derived, by searching the root of objective function, all modes of mode frequency or cable tension can be calculated, if cable parameters are known;(2) According to the known frequencies of various modes, two methods are presented to perform cable parameter identification. Taking cable tension of all modes are equal as the objective, if boundary condition is given, then cable tension and flexural rigidity can be identified by dichotomy method. If boundary condition is not given, then boundary stiffness can also be identifified, according to the shape of mode-tension curve. Taking minimizing the difference between all modes of calculated frequency and measured frequency as the objective, the combination of sensitivity updating method and dichotomy method is presented to identify cable tension, flexural rigidity, boundary rotational and spring stiffness, simultaneously. Sensitivity updating method is used to identify only cable tension and flexural rigidity, dichotomy method is used to identify boundary restraint stiffness.(3)nη-ξ relationship curve in different boundary condition is calculated by the dichotomy method. For cables clamped at both ends, clamped at one end simply supported at other end, only consider rotational restraint stiffness, practical formulas to calculate cable tension by high mode of measured frequencies are derived, which are convenient for engineering applications.(4) Test case of numerical cable model is built in ANSYS, to verify the precision of frequency and cable tension calculated by dichotomy method, and the precision of cable parameter identification by the combination method. The way rotational and spring retraint stiffness affect the nη-ξ curve of cable is studied, and conclusions are made. The relationship between cable frequency and cable parameters is studied, by locking some of the parameters, the sensitivity between frequency and other parameters is analysed. The identification precision of parameters in different cases in which some cable parameters are locked in different values, are also analysed.(5) Based on the Imote2 remote sensor, software is developed herein to read measured frequencies and their modes automatically, and then identify cable parameters. The above methods and program developed are used to identify parameters of stay cable in construction monitoring of Fan He Gang cable stayed bridge. The parameter identification result validates the correctness and convenience of the presented method.