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Shock and Vibration
Volume 1 (1994), Issue 4, Pages 375-384

Response of Launch Pad Structures to Random Acoustic Excitation

Ravi N. Margasahayam1 and Raoul E. Caimi2

1I-NET Space Services, I-NET Inc., Mail Stop INI-5, John F. Kennedy Space Center, FL 32899, USA
2NASA Engineering Development, Mail Stop DM-MED-11, John F. Kennedy Space Center, FL 32899, USA

Received 23 October 1993; Revised 24 January 1994

Copyright © 1994 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The design of launch pad structures, particularly those having a large area-to-mass ratio, is governed by launch-induced acoustics, a relatively short transient with random pressure amplitudes having a non-Gaussian distribution. The factors influencing the acoustic excitation and resulting structural responses are numerous and cannot be predicted precisely. Two solutions (probabilistic and deterministic) for the random vibration problem are presented in this article from the standpoint of their applicability to predict the response of ground structures exposed to rocket noise. Deficiencies of the probabilistic method, especially to predict response in the low-frequency range of launch transients (below 20 Hz), prompted the development of the deterministic analysis. The relationship between the two solutions is clarified for future implementation in a finite element method (FEM) code.