Comparison of Traditional and Finite Element Solutions to Random Vibration Problems

Despite recent improvements in finite element applications, random vibration problems encountered in practical design situations continue to be tackled by a traditional simplified approach based on a single mode and single degree of freedom response. This paper presents an outline of this approach and examines its accuracy and validity by correlating its results against a finite element program for two specific examples. The correlation indicates that stress predictions using the traditional approach based on equivalent static loads are acceptable for design purposes, but displacement velocity and acceleration response estimates can be dangerously optimistic. The effects of damping and modal interactions on structural response are studied and the difficulties associated with accurate damping selection are also discussed from a practical standpoint.