Evaluation Method for Crack Propagation Behaviors at Shell-Annular Joint in Petroleum Storage Tank under Repeated Large Deformation. Paper 3. Evaluation of Ultra Low Cycle Fatigue Life by using Two Dimensional Finite Element Analysis.:Evaluation of Ultra

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In recent years, the importance of safety management for steel structures subjected to severe earthquakes has much been recognized. Especially in oil storage tanks, the shell-annular joints are supposed to suffer from large cyclic Plastic strains caused by bending moments due to uplifting of wall plates. It is required to establish an estimation procedure of the ultra low cycle fatigue life and the criteria of maintenance of these joints so as to prevent fatal accidents.Several papers have reported about the relationships between crack initiation life and cyclic displacements, including the effects of joint geometry in low cycle fatigue. However, the crack growth behaviors have not been much studied in these welded joints under low cycle bending loadings.In the present study, a series of two-dimensional finite element analysis was conducted for a fillet joint model subjected to bending. J integral values were calculated in steps for different crack depths and bending displacements. Crack growth rates was estimated by a power-law of J integral and integrated to obtain the failure lives. A good agreement was confirmed with experimental results obtained in previous reports.
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