Stress and buckling analysis of grain silos under snow or wind loads
Khazra, Afshin
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https://hdl.handle.net/2142/19557
Description
Title
Stress and buckling analysis of grain silos under snow or wind loads
Author(s)
Khazra, Afshin
Issue Date
1989
Doctoral Committee Chair(s)
Pecknold, David A.
Gurfinkel, German
Department of Study
Civil and Environmental Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Language
eng
Abstract
The objective is to devise a simple yet reliable method of analyzing stiffened shells of revolution. As an example a grain silo with a conical roof is studied under the action of snow or wind load. First the silo is analyzed by the current simplified conventional method. Simplifications include ignoring the presence of the shell skin, the ring and intermediate ring, the cross braces and the eccentricities and transverse shear deformations of all stiffeners. Next, to arrive at more accurate solution the same problem is solved by the finite element method. A finite element computer program, PHOENIX, developed by the writer is tailor-made to model stiffened shells of revolution of any meridional geometry as closely as possible to the actual condition of the structure, excluding all of the simplifications mentioned above. This analysis proved that the conventional analysis overestimates the generalized stresses by 200 to 300 percent. As an alternative a simple improved model is proposed, which takes into account the presence of the shell skin, the ring and the intermediate ring by replacing them with equivalent axial and rotational springs. This improved method has the simplicity comparable to the conventional design method and accuracy confirmed by the results from PHOENIX. The silo or its conical roof was analyzed under four separate types of loading (uniform and nonuniform snow, uniform and nonuniform wind) by the three methods and comparisons were made. Also the same comparisons were carried out when the shell skin is corrugated and the loading is uniformly distributed snow. The comparisons indicate that the proposed modified method provides one with satisfactory analysis of the conical roof. Finally a buckling analysis of the conical roof and the cylindrical base of the silo was made.
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