[PDF] Creep Theory For A Floating Ice Sheet eBook

Author : D. E. Nevel
Publisher :
Page : 122 pages
File Size : 15,67 MB
Release : 1976
Category : Ice
ISBN :

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The problem investigated in this thesis is the prediction of the deflection and stresses in a floating ice sheet under loads which act over a long period of time. This problem is currently important for oil exploration offshore in the Arctic. A review of analytical methods for predicting the bearing capacity of an ice sheet is given. The problem is formulated by assuming the ice is isotropic with a constant Poisson's ratio. The shear modulus is assumed to obey a linear viscoelastic model. The specific model selected is a series of one Maxwell model and two Voigt models. One of the Voigt models has a negative spring constant which produces tertiary creep. The ice model exhibits a primary, secondary, and tertiary creep response, similar to that observed in uniaxial creep tests of ice. The material properties in the viscoelastic model may be a function of the vertical position in the ice sheet, but all these material properties must be proportional to the same function of position. Using the thin-plate theory for the floating ice sheet, the solution is obtained for the deflection and stresses in the ice sheet for primary, secondary, and tertiary creep regions. It is then shown that for a load that is not distributed over a large area, the time-dependent part of the deflection and stresses is relatively independent of the load's distribution. For the elastic case, the stress significantly depends upon the load's distribution. Results are given for the deflection and stresses as a function of time and distance from the load. The maximum deflection and stresses occur at the center of the load. At this point the deflection increases with time, while the stresses decrease; i.e., the stresses relax. (Author).

Author : Donald H. Garbaccio
Publisher :
Page : 56 pages
File Size : 23,87 MB
Release : 1967
Category :
ISBN :

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Theory was developed for a finite length line load on an elastic plate on elastic foundation. When the solution for a finite thickness plate failed to give convergent expressions for the bending moments under the load, the solution was reduced to the case of a thin plate for which a convergent solution was obtained. The correspondence principle was applied to obtain the linear viscoelastic problem. An approximate method of Laplace transform inversion was used to obtain the time dependent behavior of the creeping plate. Numerical results are presented. Theory was developed using the Hankel and Laplace transforms for a plate of finite thickness with circular symmetrical loading which was later reduced to a uniform load over a circular area. The solution is presented in a form where numerical calculations can easily be made with a digital computer. Owing to the complexity of the problem the nonlinear creep behavior of floating ice sheets was limited to a thin plate with circular symmmetry deforming with a power creep law. No numerical results were obtained but a suggested method of solution is outlined. (Author).

Author : D. H. Garbaccio
Publisher :
Page : 100 pages
File Size : 35,89 MB
Release : 1968
Category :
ISBN :

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Using a digital computer calculations were made of the deformations and bending moments in a floating ice sheet. The ice behavior was described by a linear viscoelastic model consisting of a Maxwell and a Voigt element in series. Loading with circular symmetry uniformly distributed was applied to a plate of finite thickness described by Reissner theory. The effect of superposed loads describing aircraft landing gear was considered. Calculations were also made for a linearized approximation to the problem of a thin sheet described by a power creep law. The method was only partially successful because the time span of applicability was short. (Author).