Strength Deterioration of Steel Structures considering the Strain Concentration caused by the Dynamic Localization of Buckling Patterns

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A computer program is developed in order to analyze the dynamic localization of buckling patterns for thin-walled steel structures. in this program, the three-surface cyclic plasticity constitutive model is implemented. This constitutive model can accurately express the cyclic behavior of structural steel with less parameters and internal variables. First, we examine the applicability of our program to the analysis of the localization of buckling patterns in thin-walled steel piers. As a result, the program can accurately predict the dynamic as well as the static localization behavior observed in the experiment. Then, we proceed to extensively investigate the dynamic localization of steel piers with circular cross section, by using the computer program. As dynamic loads, sine acceleration waves are applied to the pier base. From this investigation, it is observed that the response displacement and the response strain of the steel piers take their maximum when the period of the sine wave becomes approximately 1.5 times as large as the natural period of the elastic pier. This is probably due to the resonance of the damaged pier whose natural period is increased, compared with the elastic pier. Regarding the localization mode, the steel piers exhibit elephant foot buckling mode when the period of the acceleration wave exceeds the natural period of the steel pier. If the period of the acceleration wave is less than the natural period, a local buckling appears at either side of the pier surface perpendicular to the direction of the input acceleration wave.