Prediction of dynamic response of stiffened rectangular plates using hybrid formulation

A developed method,based on the varitional principles in combination with the finite difference technique,is applied to determine the dynamic characteristics of rectangular panels having stiffeners in both directions. the strain and kinetic energy for the plate and stiffener are expressed in terms of discrete displacement components using the finite difference method. harmonic motion is assumed in order to eliminate the time dependency and exclude the transient response. the functional is minimized with respect to the discretised displacement components and the natural frequencies; and corresponding mode shapes are obtained from the solution of a linear eigenvalue problem. the natural frequencies and mode shapes of stiffened panels are determined for various boundary conditions. the results are included for a number of stiffened plates where the dimensions of the plate and stiffener cross section are chosen so that the mass of the plate-stiffener combination remains constant. the energy approach using the variational procedure yields acceptable results for the type of stiffened plates considered in this study. the results show that the natural frequencies can be increased by increasing the flexural rigidity of the stiffeners,and also the frequencies of two modes can be close or even be equal to the exact solution for a given size of stiffener. © school of engineering,taylor's university college.