parametric study of the modal behavior of concrete gravity dam by using the finite element method

parametric study of the modal behavior of concrete gravity dam by using the finite element method

considering the period of the first mode of dams is an essential part of its seismic behavior analysis. therefore, it is crucial to calculate the natural frequencies. this paper aim is simulating and analysis of the finite element (fe) model of the koyna concrete gravity as a case study. in order to investigate the suitable mesh size to achieve the grid independency, the element size is considered as a variable parameter and its optimized value is determined by using the response surface optimization (rso) method. in the independent grid, to controlling mesh quality, the error contour is utilized, which indicates fast variations of the energy in the adjacent elements and can recognize parts of the model that has a high error in calculating responses. the modal response of the dam with a rigid and flexible foundation with and without mass is appraised.

the results indicated that modal frequencies in the condition of with and without pre-stress are different in all cases. moreover, the frequencies of the first four modes by increasing the mass and decreasing the stiffness of foundation, frequencies in the case without initial condition (without pre-stress) have a slight increase and in the case with initial condition (pre-stress) have considerable decrease.