Structural behaviors of the connections between concrete filled square tubular high strength (780N/mm^2) steel column and wide flange high strength (590N/mm^2) steel beam have been studied by cruciform tensile tests and beam-and-column subassemblage tests. Stable hysteretic loops of rich energy absorption capacity have been obtained showing good structural behaviors for seismic loading by beam-and column subassemblage tests. Yield and ultimate strengths of the connections have been analysed based on the yield line theory taking the strain behaviors of the connections into consideration. The analytical results agree well with test results.
