| As one of the main forced components in cable-supported bridge, the cable force and the stress state is directly related to the security control in the process of bridge construction and the assessment of bridge situation during the operation of the bridge. In the cable force measurement methods, frequency method because of its simple operation, equipment can be reused and can be used to the finished bridge cable force measurement is widely used.The principle of frequency method measure cable force is based on the simple string vibration theory, because the formula from it can conveniently estimate cable force, this method gets the site engineers’favor. However, in the practical application, sometimes the cable force calculation error is large even would get wrong results. Therefore, summarizing the existing research results, the thesis takes into consideration with the bending stiffness, cable sag, inclination and boundary conditions, and concludes cable force calculating formula that consistent with the specific situations. In addition, the cable itself parameters have great influence on the cable force calculation precision, so this thesis also take brief analysis on the cable parameters value.In order to suppress the cable vibration, modern bridges are equipped with various shock absorbers. The installation of the vibration damper can change the cable vibration mode and improve the natural vibration frequency. The thesis adopts two methods to consider the influence of the shock absorbers:one is constructing new modal function of cable with shock absorber, using the energy method to derive calculation formula; the other is given to the installation of the vibration damper can shorten the cable dynamic calculating length, it summed up the shock absorber damping mechanism and the desire control vibration mode, the effective length of cable is reduced to reflect the influence of the shock absorbers.Parallel strand cable is widely used in cable-supported bridge because of its convenient construction, excellent anticorrosion, obvious economic benefit and suitable for single steel strand cable replacement and so on. However, as the steel strand cable force is not uniform and has strand discrete problems, the feasibility of frequency method measure parallel strand cable force is doubted. In the thesis, through the finite element modeling, comparative and analysis, confirmed the feasibility of frequency method measurement steel strand tension.HDPE casing is widely used in current cable protection system because of its light weight, good anticorrosion, low cost, convenient processing and mounting. However, when using the frequency method to measure the cable force, the acceleration sensor is directly fixed on the PE casing. Besides, as the PE casting force is very small, it will contact with the cable body in the middle part. Viewing of the above questions and through modeling the cable-PE casting, the effect that PE casting to cable can not be ignored and through adjusting the cable linear density to consider the influence of the outsourcing PE casting.Due to the project needs, some suspender in the actual bridge is complicate. For the situation that the suspender end with a rigid connection segment, because the stiffness and the linear density of the rigid segment is not the same with the rest of the flexible cable, when using frequency method measure the cable force, it would be difficult. What’s more, the suspender in arch bridge is always short. It’s not desirable to wholly ignore the rigid segment. In this thesis, through the finite element modeling, find that the problem can be solved by reducing the effective length, and get the adjustment factor for a CFST arch bridge. |
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