We derive the two-dimensional shell equations for a circular cylindrical sh
ell by means of an asymptotic expansion of the three-dimensional elastic st
ate. The assumptions involved are of mathematical character only and concer
n the continuity, differentiability and convergence of the series used. A n
umerical comparison between the frequencies obtained by the two-dimensional
shell equations and the three-dimensional state in the case of free vibrat
ions is presented in a few examples. (C) 2000 Elsevier Science Ltd. All rig
hts reserved.