柱SC梁S構造における内部柱梁接合部の構造性能

抄録

 As a new structural system with the structural characteristic same as steel reinforced concrete (SRC) and concrete filled steel tubular (CFT) structures, we are working on the development of steel concrete column-steel beam composite structures which filled concrete only in cross type steel. Over the past few years, we confirmed the mechanical behavior of column members and exposed type column bases in this new structural system, and by appropriate design it is possible to provide good seismic performance. Moreover, we proposed the simulation model of the restoring force characteristics of a column and an exposed type column base. Next, for practical application of this new structural system, it is necessary to examine the structural performance for beam-column connections, and propose the design method.

 In this paper, we confirmed the mechanical behavior of interior beam-column connections for steel concrete column-steel beam structures through the structural tests under the constant axial compression force and the cyclic horizontal load. The experimental parameters were selected reinforcement method of beam-column connection, the following reinforcement type were selected: (a) external diaphragms type, (b) inside stiffener type and (c) combination type which used external diaphragms together with inside stiffener. All test specimens were designed so that the failure of panel zone happened earlier than the failure of column and beam. Main discussion is concentrated on the failure state, ultimate strength and hysteresis characteristics.

 The test results indicated that the partial frame including beam-column connection had the stable hysteresis behavior until story drift angle of 3.0-4.0% radian, and the failure was concentrated in panel zone. Moreover, it was found that ultimate strength and ductility of the beam-column connection with large size external diaphragm were excellent, in comparison with the inside stiffener type beam-column connection. In the external diaphragms type, the tensile stress to transmit from the flange of beam to the orthogonal flange of panel zone increase. Moreover, the concrete of panel zone surrounded by external diaphragm, vertical stiffeners and steel flange can sustain large strain because of the confining action. This is the reason why the beam-column connection with external diaphragm showed advantageous structural characteristics.

 According to the AIJ design standard for SRC structures, the calculation value of ultimate strength of beam-column connection is calculated to the sum of the strength of the steel web plus the strength of the concrete in the panel zone. It was shown that the ultimate strength of beam-column connection could be evaluated on the safety side by a method based on the AIJ design standard. In addition, we confirmed that it was reasonably evaluate by added the strength of the orthogonal flange to the method based on the AIJ design standard.

 Three-dimensional nonlinear finite element analysis were conducted using ‘‘FINAL’’. The analytical values well predicts the experimental results until the attainment of the ultimate strength of the beam-column connection, and the maximum principal stress of steel was examined. It was confirmed that the tensile stress was transmitted to the orthogonal flange through the vertical stiffener.