Modal analysis of a box-shape girder by numerical method

Abstract

Modal analysis of structures is carried-out to calculate natural frequencies and mode shapes. These parameters are the essential technical information required in the analysis and design of any structures. In addition, this information is needed for understanding and simulating dynamic behavior of structures. For simple structures, theoretical approach can be used to predict these parameters, however for complex structures, numerical method should be used. It is claimed that for complex structures, closed form solution can be used to predict natural frequency of first mode by idealization of complex structures to simple one. In this paper, the modal analysis of a box-shape girder is studied numerically and results are compared with simple beam model which has the same cross sectional properties. It is found that simple beam model can predict first mode of vibration, if adequate boundary conditions are considered.