THE GRADUATE SCHOOL
of
THE UNIVERSITY OF COLORADO
AT BOULDER
-----------------------------------
DISSERTATION DEFENSE
of
Hiraku Sakamoto
FOR THE DEGREE
DOCTOR OF PHILOSOPHY
-----------------------------------
Date/Time: November 22, 2004   10 am.-     
Bldg./Rm:: Engineering Center, Onizuka Conference Room (ECAE199)

Complete title of thesis:
Dynamic Wrinkle Reduction Strategies
for Membrane Structures
Faculty Advisor: Professor K. C. Park

Thesis committee:
Professor Mark Balas, University of Colorado
Dr. W. Keith Belvin, NASA Langley Research Center
Professor Kurt Maute, University of Colorado
Professor M. C. Natori, Japan Aerospace Exploration Agency
Professor Lee Peterson, University of Colorado
K. C. Park, University of Colorado
Abstract

The present study addresses vibration suppression, as well as wrinkle mitigation, of membrane structures whose boundaries are surrounded by web-like perimeter cables. This proposed membrane design realizes significant structural mass reduction when compared to the conventional catenary design. A key dynamic characteristic of the proposed structure is that support perturbations that propagated into the outer perimeter cables have a minor effect on the vibration frequencies of the membrane. This property has been exploited in the development of vibration suppression strategies using both passive and active control. These strategies are corroborated by carrying out nonlinear transient analyses, which account for the effect of wrinkles in the membrane. The results confirm that disturbances emanating from the support structures can be isolated by the outer perimeter cables, while maintaining the interior membrane in a wrinkle-free taut condition. A simple active control law has been developed and applied to only the outer perimeter cables. The proposed controllers consist of two kinds: linear theory based controllers and autonomous distributed cable tension controllers. Additionally, passive vibration suppression effects in the web-cables are enhanced by tailoring the topology and thickness of the cable networks. Numerical simulations show that the combination of the web-cable girded membranes and the proposed vibration suppression strategies can provide sufficient damping for both in-plane and out-of-plane vibrations.