• Circular plate on a non-linear elastic foundation with moderately large deflections

      DaDeppo, Donald A.; Elliott, Dwayne, 1961- (The University of Arizona., 1991)
      Typically, the problem of a plate on an elastic foundation has been approached by assuming that the foundation modulus (or modulus of subgrade reaction for a soil) remains constant as the plate deforms the foundation. If one were dealing with soil as the foundation material, it can be seen from a load-deformation plot for a particular soil, that this modulus would not be constant but would decrease as the deformations increase. The purpose of this thesis is to obtain an accurate solution that uses a more realistic model for the effect of the foundation behavior in the problem. When larger deflections of the plate are encountered, the results of the analysis using a non-linear model for the foundation differ substantially when compared to results using a linear model.
    • Straw bales and straw bale wall systems

      DaDeppo, Donald A.; Bou-Ali, Ghailene, 1968- (The University of Arizona., 1993)
      Hay and straw bales can be stacked up like giant insulating bricks to form load-bearing walls for a wide variety of structures. The technique could provide home builders with inexpensive, energy efficient, long-lasting, fire-resistant, easily built, comfortable houses from a natural resource yearly renewable and locally available. Unfortunately, the lack of knowledge regarding the structural properties of the bales and the wall systems incorporating them presents a major barrier to straw-bale construction. Without the quantitative information that standard engineering testing would provide, the wider use of bale construction will continue to be severely inhibited. This thesis examines the basic mechanical properties of individual straw bales (stress-strain behavior, ultimate strength, Poisson's ratio, etc ...), and prototype wall systems (vertical strength, in-plane lateral strength, out-of-plane lateral strength, deflection, creep, etc ...). The results of the tests on the individual bales as well as the wall systems are used to develop guidelines and equations for the design of straw-bale structures.
    • Torsional properties of an ovaline cross section

      DaDeppo, Donald A.; Gottlieb, James Harold, 1954- (The University of Arizona., 1991)
      Torsional properties of a solid, linearly elastic, and isotropic bar with the cross section in the shape of an ovaline were investigated. An ovaline is a variant of an ellipse defined by the parametric equations: x = a(1 + αcos²λ)cosλ, and y = b(1 + βsin²λ)sinλ. Only ovalines with a smooth, aerodynamic type of cross section under St. Venant torsion were considered. The torsional properties of interest included the maximum shear stress component, the maximum shear stress magnitude and the torsional stiffness. The results from twenty-eight finite element models were correlated to several candidate solutions for each of the torsional properties based on variances of the classical elliptical solution. Correction factors are provided where appropriate. The recommended methods of solution provide highly accurate results for the class of ovalines considered in a fraction of the time required to obtain results via the finite element method.