Thick cylindrical shells under transverse loading exhibit an elephant foot buckling mode, whereas moderately thick cylindrical shells show a diamond buckling mode. There exists some intermediate ...geometry at which the transition between buckling modes can take place. This behavior is significantly influenced by the radius-to-thickness ratio and the material yield strength, rather than the length-to-radius ratio and the axial force. This paper presents a critical value at which the transition of buckling modes occurs as a function of the radius-to-thickness ratio and the material yield strength. The result shows that the circumferential wave number of the diamond buckling mode increases with decreasing wall thickness. The strain concentration is also intensified for the diamond buckling modes compared with the elephant foot buckling modes.
Maximum stress obtained by compression test of circular steel stub-columns were compared with deformation theory and incremental stress-strain theory. Each buckling analysis has a term of tangent ...modulus Et in its solution. Therefore these solutions are commonly considered that all specimens lose stability in the plastic-flow region. This paper shows that specimens with small diameter-to-thickness ratio can be compressed beyond plastic flow region by reconsidering past plastic theories.
Moderately thick perfect cylindrical shells under axial compression first exhibit axisymmetric deformation patterns, where a localization of buckling patterns, i. e. an elephant foot bulge, occurs at ...the first plastic bifurcation. However, the transition from the axisymmetric buckling mode to a diamond buckling mode may occur due to the next bifurcation if we continue the loading under displacement control. Herein, this phenomenon is examined based on a rigorous plastic bifurcation analysis. As a result, it is observed that the circumferential wave number of the diamond buckling mode increases with the decrease of the wall thickness. It is also found that the strain concentration is intensified for the diamond buckling mode, compared with the axisymmetric buckling mode.
The present study is discussed about the seismic risk assessment of steel tanks when a strong earthquake excitation develops a plastic deformation of base plate by a rocking motion of the tank. ...Current seismic design guidelines underestimate the seismic safety of buckling failure at the side wall, because the stiffness degradation of the tank is overestimated with the structural characteristic factor Ds. The present study proposes the exact estimation approach of the seismic safety of elephant foot buckling failure at the side wall as well as the crack failure of the base plate. The seismic performance of the tank is also developed on the limit state design method to provide the fragility curves for the damage modes of the side wall and base plates.
The present study is discussed about the seismic risk assessment of steel tanks when a strong earthquake excitation develops a plastic deformation of base plate by a rocking motion of the tank. ...Current seismic design guidelines underestimate the seismic safety of buckling failure at the side wall, because the stiffness degradation of the tank is overestimated with the structural characteristic factor Ds. The present study proposes the exact estimation approach of the seismic safety of elephant foot buckling failure at the side wall as well as the crack failure of the base plate. The seismic performance of the tank is also developed on the limit state design method to provide the fragility curves for the damage modes of the side wall and base plates
Maximum stress obtained by compression test of circular steel stub-columns were compared with deformation theory and incremental stress-strain theory. Each buckling analysis has a term of tangent ...modules Et in its solution. Therefore these solutions mean that all specimens buckle in the plastic-flow range before strain-hardening regionregardless of its diameter-to-thickness ratio. In spite of these theories, it is shown that specimens with small diameter-to-thickness ratio can be compressed into the strain-hardening range. Furthermore the efficiency of endurance of compressive force is referred between box-section and circular section steel stub-columns.
Thin metal cylindrical shell structures such as silos and tanks are susceptible to an elastic–plastic instability failure at the base boundary known as elephant's foot buckling, due to its ...characteristic deformed shape. This form of buckling occurs under high internal pressure accompanied by axial compression in the shell structure. This is a common failure mode for tanks under earthquake loading. Another common situation is in a silo where the silo wall is subjected to both normal pressures from the stored granular solid and vertical compressive forces developed from the friction between the stored solid and the silo wall. This paper presents a novel method of strengthening cylindrical shells against elephant's foot buckling in which a small amount of fibre-reinforced polymer (FRP) composite, used at a critical location, can effectively eliminate the problem and increase the buckling strength. The strengthened shell is analysed using linear elastic bending theory in this preliminary study. Within the scope of this research, the strengthening effect is shown to be sensitive to the thickness, height and location of the FRP sheet. The issue of optimal FRP strengthening to allow the shell to attain pure membrane-state deformation is examined in detail as strengthening with too much and too little FRP are both undesirable. Both pinned-based and fixed-based shells are examined and their responses are compared.
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