The Research And Practical Application Of Frequency Method Of Cable Force Measurement

Frequency measurement of cable force is widely used for construction controlling and health monitoring in cable structure. Though a great deal of work have been done in home and abroad, theory research of frequency measurement still lag behind engineering practice due to the multiplicity and complexity of cable structure application, so it is meaningful and urgent to make further study on it.In most cases, the differences of stiffness and weight of unit length of stay cable anchor from that of flexible cable have not been considered on the research of force measure using frequency method so far, and satisfied results can be obtained when it is applied to force measure in cable bridge. However, when it is applied to the short suspenders of suspension bridge, such ignorance will come into unacceptable error or even wrong result. What is more, the shockreducer will influence the frequency of the cable, but the formula used generally do not consider this effect, and will result in unwanted error when it comes to the cable in this case.Based on cable force measure of suspender in self-anchored cable supported-bridge which is used in PING SHENG GREAT BRIDGE located at Foshan city, frequency measurement of cable force is studied in this thesis, including:(1) the frequency character of cable without capable of anti-flex has been analyzed and the frequency equation has been deduced.(2) the differential equation of uniform cable has been developed and resolved, Error analysis of frequency measurement is carried out, and the influences of anti-flex stiffness, additive weight, elastic restriction to cable force are analyzed through analytical method.(3) Considering the difference between anti-flex stiffness of anchor section, weight of unit length and that of flexible cable, three-segmental uniform cable vibration model has been established, and the frequency equation has been deduced based on Hamilton principle. In order to calculate conveniently, the model can be simplified as that of an elastic bearing simply beam which is tense, the frequency equation has been deduced, and the iterative algorithm was given.(4) Cable with shock mount is simplified as two-span continuous long cable of elastic bearing, and with singular function and Laplace transformation applied, the frequency equation has been deduced and resolved. (5) The method of frequency measurement of cable force put forward in this thesis has been applied to cable force measure in PING SHENG GREAT BRIDGE, and the results are satisfied. It indicates that the method can be promoted in engineering practice.