Abstract
Various fracture modes were observed in the connections with stiffener rings between steel beam flange and concrete -filled circular tube column by the experimental research works carried out previously by other Japanese investigators, The yield line mechanisms are proposed for the observed fracture modes, and estimation formulae of the local plastic and ultimate strengths of the connection are proposed in this paper. The fracture mode of the connection can be predicted properly by this research work, and the estimated local plastic and ultimate strengths agree well with the experimental results regardless of the test series carried out previously.
