Study On The Identification Of The Cable Force By The Sine Excitation Frequency Method

Because of its shape, function and expensive large-span prestressed spatial structurebecomes an important landmark or public facilities. Heavy casualties will come true if thestructure has collapsed, it is the key that the health monitoring of the cable after the completionof structure which is to ensure the structural safety and durability. As a lightweight, high strengthmain force component, the stress of the cable will corrosion and miss with the stress relaxation,this will adversely affect the safety and durability of the structural. Present with the rapiddevelopment of the theory of the cable force identification method and practical applications, themost widely used method for in-service cable structure force measurement is the frequencymethod. Frequency method can be used not only in the construction phase of the large-spanstructures but also be applied to online real-time measurement of the cable tension. So, thelearning of the research and application of frequency method attract more and more attention,but because of the diversity and complexity the stress state of the cable in the actual project, thefurther study of the structure of the cable tension cable in service identification appears isparticularly important.General frequency method relies on the environment or human hammer. For the averageguy in the long this method can get more precise fundamental frequency, but with short and longcable cord, for the effects of the stiffness and mass it is difficult to obtain a better mode ofvibration, which impacts of the cable force measurement accuracy. In this paper, the method bysinusoidal excitation is proposed, according to the sweep range to find the fundamentalfrequency cable. With some engineering data, the results calculated by numerical calculationprove the accuracy of this method. And through the use of reduced scale experimentalverification of the measuring cable tension by sinusoidal excitation prove the viability of the newmethod. The method is based on frequency measurement principle, relative to the generalfrequency method has obvious advantages.First summarizes the frequency of measurement based on the principle of the cableforce, describes the linear cable vibration theory, the stiffness is derived considering theimpact and influence of cable sag formula for calculating the force, and to design theappropriate study to be calculated. Without taking into account non-linear cable linedensity in the case of the establishment of cable vibration under external force equation and the analytical solution is derived; investigated the bending stiffness, boundaryconditions, and other factors on the cable sag test force the results. Followed practicalformula is derived in the case of a short cable and cable long, and based on the actualapplication of finite element software engineering model for the establishment of cable,obtained the cable force by the simulation analysis of the fundamental frequency ofvibration, and compare the cable forces between the actual value comparison andpractical formula validated sinusoidal excitation method to prove of the accuracy of thenew method. Finally, according to the vibration test the theory, the basic properties ofthe tested cable could be obtained when the respond and the inspirer is known. Based onthis experiment by a reduced scale, when it comes to different cases such as differentforce, different points and different excitation conditions the length of the cable, thesinusoidal excitation method of determination the cable tension is verify as well asseveral law of the sinusoidal excitation method frequency is investigated..