Study on Ultimate Behavior of Building with Imbalance Strength due to Yielding or Buckling Subjected to Severe Earthquake

当建筑物在强烈地震中倒塌时，往往是建筑物最终产生变形并伴有扭转。在当前的结构设计中，考虑了质量偏心率和刚度引起的扭转行为的可能性。另一方面，屈服或屈曲引起的强度不平衡可能引起扭转行为。本文首先对支撑屈曲的空间钢框架在强震作用下的动力性能进行了数值研究。即使结构某一平面的支撑屈曲，其他平面的支撑屈曲是依次发生的，因此几乎没有观察到扭转行为。其次，对无支撑空间钢框架的静动力性能进行了数值分析。静力侧倾分析表明，在某一结构平面上形成的倒塌机制引起了整体框架的扭转行为。但如果能充分保证楼板水平面的刚度，就不会出现这种困难的情况。在动力分析中，除非空间框架本来就是不平衡的，否则惯性的作用会产生很好的效果。因此，对于原本质量与刚度平衡良好的建筑结构，不必担心屈服或屈曲导致的强度不平衡会诱发严重的扭转行为。

When a building reaches collapse with a severe earthquake, it is often that the building finally produces deformation accompanied with torsion. In a current structural design, the possibility of torsion behavior to be occurred by eccentricity of mass and stiffness is considered. On the other hand, torsion behavior may be induced by imbalance of strength caused by yielding or buckling. At first, dynamic behavior of spatial steel frame whose braces are buckled subjected to severe earthquake is numerically investigated in this study. Even if brace of a certain plane of structure buckled, that of other plane did sequentially and immediately, and therefore the torsion behavior was hardly observed.Next static and dynamic behaviors of spatial steel frame without brace are analyzed numerically. In static push-over analysis, it is shown that a formation of collapse mechanism in a certain plane of structure induce a twisting behavior of overall frame. However, if the stiffness of horizontal plane of floor is ensured sufficiently, such a difficult situation is not caused. In dynamic analysis, it is illustrated that the effect of inertia produces good results, unless spatial frame is originally imbalance.Therefore it is not necessary to be concerned that severe torsion behavior may be induced by imbalance of strength caused by yielding or buckling in the building structure with good balance of mass and stiffness originally.