Finite Element Model Updating And Modal Parameter Estimation Of Roof Truss Of Shenzhen Citizen Center

With the tendency for the structures becoming larger and more complex than before, many new structures spring up in modern time. At the same time, there are various damage in many existing structures as they have been used for several decades needing to be surveyed and strengthened. Therefore, the structural damage diagnosis which makes use of structural dynamic response to identify the physical parameter, sequentially to assess the performance of the structure and to realize the finite element model updating has become the advancing front of civil engineering researches.To forecast structural dynamic response, realize vibration control state evaluation and health monitor, the first thing is to know the structural dynamic characteristic in detail. Structural dynamic characteristic is related to structural physical parameter, and its theoretical value can be gained by finite element model (FEM) analysis, while its practical value can be achieved by experimental modal analysis. Since the structural dynamic characteristic will be changed with its damage, the great difference of structural frequency exists between the theoretical value and the practical value. The problem we are confronted with is how to correct structural FEM to make the theoretical value equal to the practical value. Neural network technique is adapted well to the FEM correction for its strong non-linear mapping ability rapid computation and anti-interference capability. But there are still some problems being open such as selection of neural network, determination of structural damage indicator and incompletion of measurement.As the steel structural model error mainly relied on the control to the member bar's link stiff and its physical dimension, this paper take the roof structure of Shenzhen citizen center as subject, through its fixity factor, to select the joint link stiff as the damage indicator. The FEM correction of truss structure based neural network can be established with the change of the structural modal and the joint link stiff, thus the FEM for the roof structure of Shenzhen citizen center are corrected by the theoretical modal analysis.In this paper, the wind loading time history of the truss structure is simulated according to the data of wind tunnel experiment and pulsating windspectrum, and the transient dynamic analysis is used on the FEM. Secondly, the space FEM of truss structure that based fixity factor is determined, and the relation between fixity factor and structural dynamic characteristic is established with the change of fixity factor. The fixity factor is identified by BP neural network The FEM correction method of truss structure based neural network technique is developed in this paper, and transient dynamic analysis is used on the FEM. Thirdly, the optimizational layout for acceleration transducer and the actual measured method for the modal parameter of the truss structure are also discussed in this paper and the accuracy of the FEM correction is verified by the finite element transient dynamic temporal analysis,According to the research of this paper, BP neural net can be well adapted to structural FEM correction. The combination of modal analysis and the transient dynamic analysis can guarantee the reliability of the FEM well.