Three solution models of lateral frequencies of stiffening cylindrical shell

The equivalence methods of area and moment of inertia were studied for the stringers in stiffening cylindrical shell, and the accuracy of moment of inertia when the area was equivalent, and the accuracy of area when the moment of inertia is equivalent were investigated respectively. The concept of critical thickness of thin cylindrical shell was revealed in the calculation of lateral inherent frequencies and the deficiency of the equivalence thickness method was pointed out. The equivalence beam model, the three dimensional (3-D) shell-beam model and the 3-D varied thickness shell models were presented for the lateral free vibration analysis of stiffening cylindrical shell, although these models can be utilized to analyze the dynamic characteristics of rocket, the lateral effects of the stringers predicted by different models differ greatly. Moreover, one dimensional analytical solutions corresponding to both 3-D models with simply supports were given, from which the effects of stringers on the lateral frequencies were straight forward.