繰返し載荷を受ける構造部材の塑性疲労*-研究の現状分析と展望-

Abstract

Structural plastic failure due to intense repeated action of loads, as in a destructive earth-quake, is discussed with the main attention focused on steel structures of bar members. A litera-ture survey is presented principally on experimental aspects of low-cycle fatigue from the point ofview of overall structural-failure behavior. Cyclic bending of a constant deflection amplitude ischaracterized by hysteresis loops, which may either be steady or deteriorating. The latter isoften associated with local deformation or instability, and leads to fatigue failure with a rate high-er than in the former. The existence of a compressive axial force accelerates the deterioratingbehavior. A seemingly common experimental observation is that the logarithm of the amplitudehas a linear relationship, with a negative factor, with the logarithm of the number of cycles at fai-lure, the state of which is not conclusively defined to date. Various proposals have been made inthe literature for fatigue life and cumulative damage, but not with unanimity. This is an impor-tant practical area which requires further investigation. More fundamentally, it seems necessaryto fully clarify the actual mechanism of fatigue failure.