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

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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