A STUDY ON DESIGN METHOD OF ENCASED STEEL COLUMN BASES

A theoretical study is carried out on the current design approach of encased steel column bases.The load transfer within encased bases must be analyzed.Because of the studs,part of the axial load is transferred from steel to exterior concrete.An analytical solution is presented for the axial load in the concrete.Through calculated examples it is found that the axial force in the concrete is 20%～30% of the total axial force of the column at the bottommost base.The design of the encased steel column bases requires the bending moment being transferred to exterior reinforced concrete fully at the bottom,In this situation it is found that the shear force in the cross-section of steel is reverse to the external shear force of the column,therefore the shear force carried by the exterior concrete is even greater that the external shear force.According to this phenomenon,a new design against the shear force is proposed.Finally a detailed design procedure is proposed.