Bridge Dynamic Characteristics Of Test Methods Study

The dynamic analysis is a very important subject in the bridge engineering study field. Firstly through it, the dynamic nature of the bridge structure under the traffic loads could be uncovered. On the other hand, the systematic effects of the earthquake could be discovered. However it is difficult to satisfy such demands just through the theory analysis or finite element model. Thus the dynamic testing is required to calibrate the finite element model and so far is the best method to know the bridge dynamic nature. The dynamic testing is to acquire the acceleration data, and the signal process is to identify the vibration mode through analyzing the acquired original data. Both of them are essential parts of the bridge dynamic testing method.In this paper, the general equipments applied in the bridge dynamic test, and the test contents were discussed, consequently, the fundamental knowledge and the essential measurement were presented. Also most of the bridge dynamic testing methods was introduced, the specific bridge types for each kind of method was given, the advantages and disadvantages was concluded for each of them. Moreover the structural vibration mode analysis method which is the basic theory for the bridge dynamic test was systematically introduced. Standard testing procedure and frequency analysis in the forced vibration test was described as well. In this paper, the forced dynamic bridge testing techniques used at the YINGU expressway FUDAO major bridge(continuous rigid frame bridge)was presented clearly, and the data-processing techniques in this project was described in detail. Dynamic properties of the bridge(the mode frequency and shape) and comparisions with finite-element eigenvalue analyses results were given for this bridge. Also the reliable dynamic amplification factor for this bridge was obtained. In this paper , both the beam 189 finite element model and the solid 95 finite element model for this bridge was set up, among which the beam 189 model was proposed as the better dynamic model after the analysis of the respective first 10 vibration modes by both methods. The vibration frequencies and mode shapes were calculated from a frequency analysis of the measured data, upon which the calibration of the finite-element model for this bridgewas processed, meanwhile the sensitivity analysis was conducted for this bridge either. As to the torsional mode which is usually difficult to identify, the corresponding method was put forward.Some special methods which will be helpful in increasing the estimation accuracy of the bridge structural damping factors was proposed.The problems required to be solved in the present bridge dynamic testing study were pointed out, and some corresponding advices were given.