Testing and Analysis of Inflatable Fabric Beams and Arches
Location:258 Fitzpatrick Hall
Inflatable arches and beams constructed from fabric tubes with internal, impermeable bladders are lightweight, easily shipped, and capable of carrying significant loads. As a result, they are used in the main load-carrying systems of tent-type structures employed for military facilities, disaster-relief housing, emergency medical facilities, and equipment maintenance. However, their structural analysis and design must account for several important behavioral aspects: pressure-dependent fabric constitutive properties; local compressive buckling (“wrinkling”) of the fabric that occurs well before the member’s ultimate capacity is reached; significant stiffening and strengthening due to internal pressurization; and large shear deformations. This presentation will focus on experimental and numerical research into the response of inflated fabric beams and arches conducted over a 7-year period at the University of Maine. Material-level constitutive tests designed to replicate the multi-axial fabric stress state present in inflated beams and arches will be overviewed, as will results of full-scale structural testing of beams and arches. In addition, the development of a pressurized fabric beam finite-element that accounts for effective material nonlinearities due to fabric wrinkling, the work done by internal pressure, and the in-plane large deflection and post-buckling response of fabric arches will be presented. Application of the research results to the development of specialized analysis software will also be discussed.
John C. Bridge, Professor and Chair/Dept. Civil and Environmental Eng.,University of Maine
Dr. Bill Davids is the John C. Bridge Professor and Department Chair of Civil and Environmental Engineering at the University of Maine, where he has been a faculty member since 1998. He holds a Ph.D. in Civil Engineering from the University of Washington (1998), and B.S. and M.S. degrees in Civil Engineering from the University of Maine (1989, 1991). He gained 4 years of bridge design experience with Sverdrup Corporation in Seattle, WA prior to entering academia, and is a registered professional engineer in the State of Maine. Dr. Davids has directed numerous federally- and state-funded research projects on topics in bridge engineering, inflatable structures, the finite-element analysis of concrete and asphalt pavements, and the mechanics of solid and engineered wood. These research projects have encompassed both experimental work and the development of problem-specific numerical analysis techniques. To date, he has authored or co-authored over 100 publications, including 40 articles in peer-reviewed journals, and he co-holds two patents. He has received two best paper awards for a recent journal article, and was voted the State of Maine Civil Engineer of the Year in 2010. Professor Davids has developed three publically available finite-element software packages, which include EverFE for the linear and nonlinear 3D finite-element analysis of jointed plain concrete pavements (www.civil.umaine.edu/everfe), EverStressFE for the 3D finite-element analysis of asphalt pavements (www.civil.umaine.edu/everstressfe), and PressArchAnalysis for the geometrically and materially nonlinear analysis of pressurized fabric arches and beams (www.civil.umaine.edu/pressarchanalysis). Professor Davids teaches undergraduate and graduate courses in structural design, analysis, and numerical methods. In addition to teaching and research, Dr. Davids has consulted for a range of private companies on projects including the seismic analysis of large dams, the development of specialized engineering analysis software, and the review and generation of novel design concepts for advanced structures. Working with industry partners, Dr. Davids co-developed the AASHTO LRFD Guide Specification for the Design of Concrete-Filled FRP Tubes for Flexural and Axial Members, which was approved by AASHTO in 2012.