Both the space structure and the loads are very complex in practical while reinforced concrete is not at all ideal elastic material as crack and yielding occur at times.

• 建筑结构往往是一个很复杂的空间体系,实际荷载也是很复杂的,且钢筋混凝土结构又有开裂、屈服等现象,并不是理想的弹性匀质材料。