Abstract
This paper discuss the natural frequencies and modes shapes of oblate shells by finite element method via ANSYS12 package with and without longitudinal and lateral stiffeners. Different types of elements are considered using three dimensional analysis with APDL program to take the variables of shell’s thickness, number of stiffeners and size of stiffeners. The obtained results reported the tenth structural natural frequencies and mode shapes which are based upon the behavior of the shell, it can be shown that the natural frequency of the oblate shell increased with increasing the mode number and the amplitude decreasing as increasing the thickness of shell.
