VIBRA--An Interactive Computer Program for Steady-State Vibration Response Analysis of Linear Damped Structures.

Abstract : Steady-state vibration response analyses are commonly used in evaluating the dynamic behavior of structures subjected to cyclic external forces. An undocumented vibration response analysis based on modal superposition was developed about 10 years ago. The analysis calculates the acceleration response at any selected point on a structure for specified vibratory loading; the program provides tabular output of modal accelerations and acceleration response with optional paper plots. In using the program, it became obvious that several improvements were desirable; thus, an effort was undertaken to expand the program's capability, to decrease turnaround time, and to make the program easier to use. The mathematical equations used in the original program were retained, but a new program logic that would use less memory storage was developed. The new program operates interactively for rapid evaluation and plotting of structural response to vibratory loads. Options are also provided to control both the printed and the interactive graphic output. The purpose of this report is to document the improved version of VIBRA (Vibration Response Analysis) computer program. The theoretical background, program description, and application are presented along with user instructions and a sample interactive computer session.