Dynamic Buckling Strength of Columns and Cylindrical Shells with Initial Deflections

Abstract

This paper deals with the dynamic buckling strength of columns and cylindrical shells used in marine space structures, which are subjected to axial impact forces due to water waves or seaquakes. The dynamic buckling strength of initially curved columns subjected to axial impact forces is investigated through a parametric analysis which has brought out the dynamic relationship between the reduced slenderness ratio and the buckling strength. Similar analyses are made for the axi-symmetrical and local buckling strength of cylindrical shells with initial local deflections. From these results the effects of shape factor, degree of impact velocity, and initial deflections on the buckling strength of columns and cylindrical shells are evaluated. Results obtained in this study are summarized as follows: (1)The dynamic buckling strength of columns and cylindrical shells with initial deflections subjected to slowly varying loads such as water wave or seaquake induced impact loads is nearly equal to the static strength. On the other hand, the dynamic buckling strength under rapidly varying loads is larger than their static strengths. (2)The axi-symmetrical buckling strength of locally deflected shells decreases with increasing initial deflections. The degree of decrease of dynamic buckling strength is more remarkable than that of static strength due to the inertia effect. (3)The possibility of axi-symmetrical and local buckling failure of steel columns supporting the elevated structures which have undergone extensive damage during the Great Hanshin-Awaji Earth-quake of 1995 is also discussed using the above results.