Experimental Studies on the Design Method to Prevent the Shear Failure of Reinforced Concrete Short Columns by Using Steel Tube

本研究项目的目的是开发一种横向超强增强(T.S.R.)在钢筋混凝土结构中，钢管部分用作横向配筋，以防止短柱等薄弱部位的脆性破坏。通过对短柱的受力性能以及方钢管混凝土与变形钢筋的粘结性能的研究，得出以下结论。1.采用T.S.R.方法可以完全防止钢筋混凝土柱中纵向钢筋的剪切破坏和屈曲，使钢筋混凝土柱具有脆性。钢管混凝土的约束提高了填充混凝土的抗压强度和变形能力，从而提高了柱的极限弯矩。2.即使用T.S.R.方法也不能防止粘结劈裂的发生。用T.S.R.法可以提高纵向钢筋与混凝土之间的粘结强度…尤其是放在角落里的栅栏。为了验证T.S.R.方法在结构中应用的有效性，进行了T.S.R.方法加固的墙梁和短柱组合以及部分边缘柱加固的框架剪力墙的试验。在这些试验的基础上得出了以下结论。1.对配重纵筋和钢管的短柱进行加固，可以将墙梁框架的倒塌机理由柱的局部倒塌机理转变为梁的倒塌机理。即使在短柱的顶部和底部形成塑性铰，由于存在非常坚固的墙梁，框架也能够具有很大的横向承载能力，并且表现出很好的延性。2.T.S.R.方法可以防止剪力墙边缘柱的剪力破坏，这是最不理想的破坏机制，即使剪力墙具有较厚的墙板和较少的边缘柱纵筋，也不能通过配箍来防止。因此，在适当确定墙板厚度和边柱纵向配筋量的情况下，采用T.S.R.法可以较好地提高剪力墙的变形能力。较少

The objective of this research project is to develop a transversely-super-reinforcing (T.S.R.) method in which steel tubes are partly used as transverse reinforcement to prevent a brittle failure of weak parts such as short columns in reinforced concrete structures. The following conclusions are reached on bases of the study on the behavior of short columns and on the bond behavior between deformed bars and concrete confined in square steel tube. 1. Shear failure and buckling of longitudinal bars which bring brittle nature into reinforced concrete columns can be completely prevented by the T.S.R. method. The confinement of the concrete in the steel tube increases the compressive strength and deformation capacity of the infilled concrete, which results the augumentation of ultimate moment of columns. 2. The occurrence of bond splitting cracks cannot be prevented even by the T.S.R. method. By the T.S.R. method the bond strength between logitudinal bars and concrete, however, can be incre … More ased especially ofr the bars placed in corners. Moreover deterioration fo bond behavior observed in hooped columns can greately be improved by the T.S.R. method.In order to examine the validity of the T.S.R. method used in structures, tests on subassemblages composed of wall girders and short columns reinforced by the T.S.R. method and on framed shear walls with edge columns partly reinforced by the T.S.R. method were conducted. The following conclusions are reached on bases of those tests. 1. The collapse mechanism of the frame with wall girders can be changed from column mechanism which is a partial collapse mechanism into beam mechanism by strengthning the short column with heavy longitudinal bars and steel tube. Even if the plastic hinges are formed in top and bottom of the short column due to the existence of very strong wall girders, the frame is able to have large lateral load carrying capacity and behaves in very ductile manner. 2. The T.S.R. method can prevent edge columns of shear wall from shear failure which is most undesirable collapse mechanism and cannot be prevented by hoop reinforcement, even if the shear wall is designed to have thicker wall panel and smaller amount of longitudinal bars in edge columns. Therefore, the deformation capacity of shear walls can greately be improved by the T.S.R. method on condition that thickness of wall panel and amount of longitudinal bars in edge columns are appropriately determined. Less