Date of Award

5-2011

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

William G. Davids

Second Committee Member

Roberto A. Lopez-Anido

Third Committee Member

Eric N. Landis

Abstract

One of the most important characteristics for military structures utilized in the field is ease of deployment/construction. The use of inflatable fabric structures directly satisfies that need due to their light weight and ease of construction. The focus of this research is inflatable, braided beams and arches with external reinforcing straps, which are used as main load-carrying members in rapidly deployable military tents. Of primary interest is determining the properties of the constituent fabrics and beams and arches, and relating these properties to the structural response of beams and arches under load. The pressurization of the member pre-tensions the braided fabric in the hoop direction and the straps in the axial direction giving the fabric shear stiffness and the straps bending stiffness. With the straps taking most of the axial stress from pressurization, the braided material bias angle is stabilized at one angle. To accurately model the structural response of the inflatable, braided, strapped structures with different braid angles the strap stiffness and fabric shear stiffness at different bias angles must be known. The straps were tested in pure tension to obtain an accurate tensile modulus. Braided material with different bias angles was tested in pure torsion to obtain shear moduli as a function of bias angle. These basic material properties were then used in finite-element computer simulations to predict the load-deformation response of full-scale arches and beams. Parallel static load-deformation tests of arches and beams were performed to provide data for model validation. Overall, this research provided input parameters for the finite element model along with bend test results to validate the model predictions. Using these results the finite element model predictions of the braided, externally strapped, inflatable beams and arches were deemed acceptable. Continual research on these types of inflatable members is important in order to extend the current understanding and predictions to the third dimension.

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