1. INTRODUCTION
The remarkable damages of RC buildings due to the recent earthquakes are the story failure of the middle floor, and the crushed columns of the 1st story of the pilot's type RC buildings.
It is thought that the cause of crashing the columns is due to the combination of high axial force and high shear force subjected at the same time under the earthquake motion.
If the RC column is failed by shear force, the axial strength is rapidly lost, and brittle failure occurs by expanding shear cracks to the whole section obliquely.
To prevent such crushing, it is important to secure the axial and lateral strength of column and to improve its deformability.
Since 1983, we developed a method to prevent the decline of the axial strength caused by the shear failure, and to improve the strength and deformability.
In 1994, we proposed new system of RC column that consists of concrete core strengthened by the thin steel spiral tube (of the following T.S.S tube)
The research results were used in design actual buildings in Ashiya City, Hyogo Prefecture. Those buildings did pass the 1995 Hyogoken-nanbu earthquake, while many RC buildings in the neighborhood suffered huge damages.
Therefore, it was proved that the proposed RC column with core concrete has certain merits over the normal RC columns in resisting the column crushing. But, the reduction of the section of columns by the exfoliation of cover concrete outside shear reinforcements cannot be prevented.
In this paper, a new system is proposed that restrains the whole section of circular RC column confined by T.S.S tube, and no spiral hoop is used by the expectation of the hoop tension of T.S.S tube itself.

TOPICS: 　FIB 2002 Osaka　　　鋼板柱　　学祭