IMPROVEMENT OF BEARING FAILURE BEHAVIOR OF T-SHAPED S BEAM – RC COLUMN JOINTS USING PERFOBOND PLATE CONNECTORS

For the joints composed of steel beams and reinforced concrete columns, shear failure and bearing failure are the key failure modes. The shear failure indicates stable hysteresis loop without the strength degradation. On the other hand, the bearing failure mode indicates large pinching and strength degration after the attainment of the maximum load.Accordingly, bearing failure in the joints should not be caused in RCS system.To improve the bearing failure behavior of S beam - RC column joint, joint details using perfobond plate connectors were proposed. Perfobond plate connectors were attached on the upper and bottom flanges at right angles to the steel flange. The objective of this study is to clarify the effectiveness of proposed joints details experimentally and theoretically.Six specimens were tested. All specimens were T-shaped planar beam - column joints with 350mm square RC column and S beams with the width of 125mm and the depth of 300mm. The beams were all continuous through the column.Perfobond plate connectors were attached on the bottom flanges at right angles to the steel flange.Three holes were set up in the perfobond plate connectors. The experimental variable was the transverse reinforcement ratio of the joints. The transverse reinforcement ratio of the joints was 0.181% and 0.815%. For each transverse reinforcement ratio of the joints, specimen without the perfobond plate connectors, specimen with the perfobond plate connectors and specimen with the reinforcing bar inserted the hole of perfobond plate connectors were planned.For all specimens, the hysteresis loop showed the reversed S-shape. However, energy dissipation for specimens for specimens with perfobond plate connectors was larger than of specimen without perfobond plate connectors. Bearing strength of specimens with perfobond plate connectors was larger than that of specimen without perfobond plate connectors. From the test results, shear strength of concrete connector a hole was 0.7 times compression strength of concrete.On the other hand, shear strength of inserted reinforcing bar was 1.25 times shear strength of reinforcing bar.Based on the stress transferring mechanism and resistance mechanism of joints proposed by authors, the design formulae of joints with perfobond plate connectors were proposed.The predictions were shown to be in good agreement with the test results.