Abstract:

ESDU 80040 provides computer programs to calculate the lower natural frequencies and mode shapes for axial and circumferential vibration of circular-cylindrical, uniform shells with either uniform stringer stiffeners or uniform ring stiffeners, or a combination of both types of stiffener, which can be modelled as homogeneous orthotropic shells. Such modelling is usually applicable when the stringers are uniformly and closely pitched around the shell circumference and the rings are uniformly and closely pitched along the shell longitudinal axis. The results obtained should be used as guidelines to practical shell behaviour. Two programs, ESDUpac A8040 and ESDUpac B8040, are given: ESDUpac A8040 applies to initially unstressed shells or to shells having initial stress due to static axial and/or pressure loading with all combinations of clamped, shear diaphragm and free shell end conditions while ESDUpac B8040 applies to an initially unstressed shell using either the discrete stiffener or smeared stiffener model but only with shear diaphragm end conditions. The format of the input to and output from the programs is illustrated by worked examples. In addition, equations are given for estimating the torsional natural frequencies and mode shapes for all combinations of end conditions except clamped/shear diaphragm.