Strength and Ductility of Non-Embedded Steel Reinforced Concrete Column Base

The non-embedded column bases of steel reinforced concrete buildings were severely damaged by the 1995 Hyougoken Nanbu Earthquake. Many anchor bolts and longitudinal reinforcing bars were fractured, mainly due to the lack of consideration of the tensile force caused by the overturning moment during earthquakes. This report examines the strength and deformation capacity of non-embedded column bases. The strength of a column base can be estimated from the summation of the strengths of the components unless the bond between the concrete and reinforcing bars has deteriorated. A high tensile force reduces the ductility of the column base. A formula is proposed for predicting the deformation capacity of column bases using the parameter “effective tensile force ratio” considering bond strength as well as tensile strength.