Natural Vibration Characteristics of Ribbed Ring Stiffened Shallow Spherical Shell

With reference to the top cover of gasholder with diameter of 45 m, the reduced-scale model of the ribbed ring stiffened shallow spherical shell was designed. The natural frequency and mode shape of the ribbed ring stiffened shallow spherical shell were obtained by modal test and the analysis of finite element. The influences of parameters such as the ratio of rise to span, the thickness of the shell, and the form of constraint on the natural vibration characteristics of the structure were analyzed. The results show that the ribbed ring stiffened shallow spherical shell has a high fundamental frequency, good rigidity, and is a rigid structure. The vertical mode shape indicates that the vertical stiffness of the structure is weak. The deviation of the first 5 order natural frequencies is within 10% between the mode experlmental results and the finite element analysis results, and the first 2 order of mode shapes are in good agreement, which is shown that the finit element analysis method can be used to analyze the low order dynamic characteristics of ribbed ring siffened shallow spherical shell. The fundamental frequency of the structure decreases with the decrease of the ratio of rise to span, and the influence of the restraint form of the support on the frequency of structure is negligible. The fundamental frequency of the structure increases with the increase of thickness of the topshell,but the increasing speed gradually decreases.