The Sensitivity Analysis Of A Bottom-through Concrete-filled Steel Tube Truss Arch Bridge’s Modal Parameter

As the means of human beings across the barriers and major method to solve the increasingly congested city traffic, bridges play an increasingly important role in the development of Chinese economy. But along with the accidents of bridges occur frequently, the status of the existing bridge has aroused widespread concern. Therefore the research for estimating the condition of bridges validly has became a hotspot. As one of the methods to evaluate the condition of bridge, the finite element model updating is a process correcting the finite element model by the tested dynamic signal, the ultimate aim of it is make the amended parameter of finite element can be consistent with the experimental values. Obtaining a baseline model, which can well reflect the realities of the structure, can be used to a basic form to identify damage, evaluate safety and compile reinforcement program. However, in the finite element model updating process, the parameter selection is blond fold, the parameter modification is repeating, the number of calculations is very heavy, so calculate the sensitivity of modal parameter and identify which element combination and amend parameter own high sensitivity before it can answer above questions very well. So the sensitivity analysis of modal parameters is widespread used in the process of finite element model updating.In this paper, research work is mainly about the sensitivity analysis of a bottom-through concrete-filled steel tube truss arch bridge’s modal parameter are as follows:(1). Based on the introduction of bridge accidents and safety hazards at home and abroad, gives a brief description in the concept and classification of modal analysis, makes a brief presentation about the modal experiment under ambient excitation. Introduces the model updating, in particular, speaks in recommendation of the current development situation of model updating in home and abroad.(2) Gives a brief description in the frequency-domain method in the process of modal parameter identification, discusses the advantages and disadvantages of it. introduces the concept of operational modal parameters identification, describes the orthogonal polynomial curve fitting, gives a derive to the theories of curve fitting, talk out its advantages and disadvantages, points out the matters of attention in the practical application.(3) Takes a operational modal experiment on one span of a bottom-through concrete-filled steel tube truss arch bridge by Locomotive Measure Point Method, identifies the modal parameters on the basis of tested signal. Establishes a finite element model according to the engineering datum and national standard by using large-scale finite element analysis software ANSYS, then calculates the theoretical modal parameters. Finally, compares experimental modal parameters with modal parameters, verify the reliability of experimental modal data, point out the existing error.(4). Take the material modulus of elasticity as a correction parameter, changes the design parameter of the selected modal parameters, obtain the modal parameter (frequency, mode shapes), calculates mode shapes MAC and frequency sensitivity, compares each condition find the finite element combination of form, which own the more high sensitivity then others, in order to reduce the amount of computation and improve the regression accuracy and stability in the process of model updating bases on the response surface.(5). Summarizes the main work and conclusions of this paper, discusses the follow-up problem of model updating need to be solved.