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The subject of this paper is the buckling behavior of thin bar stiffeners attached to plates which are subjected to normal pressure loadings. The stiffeners are mathematically modeled by a nonlinear beam theory recently derived. An analytical solution is obtained to the beam buckling equations. The curvature of the centerline along the beam's base at the buckling load is expressed in terms of the beam's thickness, height, and rotational stiffness. Analytical results are compared with an experiment recently performed.
Computerized buckling analysis of shells
Abstract : The purpose of the many examples of buckling presented here is to give the reader a physical feel for shell buckling. Section 1 contains a brief description of two kinds of buckling, collapse and bifrucation. Section 2 concerns shell structures in which the cause of failure is nonlinear collapse due to either large deflections or to both large deflections and nonlinear material behavior. Section 3 gives examples of axisymmetric shells in which failure is due to bifurcation buckling. Section 4 provides examples that illustrate the effects of boundary conditions and eccentric loading on bifurcation buckling of shells of revolution. Section 5 is devoted to combined loading of cylindrical shells and nonsymmetric loading of shells of revolution. Section 6 is on bifurcation buckling and collapse of ring-stiffened shells with emphasis given to cylindrical shells. Section 7 contains several illustrations of buckling of prismatic shells and panels, that is, structures that have a cross section that is constant in one of the coordinate directions. Section 8 focuses on the sensitivity of predicted buckling loads to initial geometrical imperfections. Section 9 demonstrates axisymmetric collapse and bifurcation buckling of bodies of revolution that consist of combinations of thin shell segments and solid segments to which shell theory cannot be applied with sufficient accuracy.
Denitrification of PVA-immobilized denitrifying photosynthetic bacterium, Rhodobacter sphaeroides
Abstract A newly isolated denitrifying strain, Rhodobacter sphaeroides NII2 was immobilized in polyvinyl alcohol (PVA) gel, and the properties of the cells in the gel were examined. The immobilized cells had low or almost no denitrification activity, but the cells were activated by incubation in light with culture medium for denitrification containing 0.5% nitrate and no other nitrogen source. Cells grown in the dark were activated by incubation at an earlier stage and to a higher rate than the light-grown cells. The activation was markedly enhanced in the PVA gel with a low cell concentration. The immobilized cells consumed nitrate with a temporary accumulation of NO 2 and evolved nitrogen gas. The immobilized cells could use various organic compounds as electron donors for denitrification. Thus, the immobilized cells were applied to a continuous treatment of synthetic wastewater using an aparatus devised by this laboratory. The results showed an efficient removal of NO 3 -N from the test water.