Abstract
Extensive research showed that RC column-steel beam (RCS) joints had sufficient seismic resistance. However, the combination of complicated strengthening details led to more workloads of welding and difficulties in concrete casting. A new RCS joint with whole column-section diaphragm was proposed in this research to address the shortcomings of constructability. The steel web did not pass through the joint, which was convenient for placing the reinforcement and horizontally casting the concrete. Since no additional steel plate was embedded in the joint region, the joint strength was mainly contributed by the concrete and stirrups. This paper aimed to study the effect of concrete strength and joint stirrup ratio on joint behavior. Five interior joint specimens were tested under cyclic loading. Joint shear failure occurred in each specimen. The joint shear strength improved by 88 % when the concrete strength increased from 33 MPa to 63 MPa. Since the joint stirrups had not fully yielded at the peak load point, the joint stirrup had a limited effect on the joint strength, represented by a 10 % increase in joint strength when the joint stirrup ratio changed from 0.5 % to 1.1 %. Nevertheless, the joint stirrups played a crucial role in confining the joint. With the increase of joint stirrup ratio, the growth of joint shear deformation could be restrained and the ductility of the joint would be improved. In addition, the shear strengths of the proposed joints were calculated according to typical methods. The results showed that nearly 90 % of joint strength was contributed by the concrete according to Nishiyama method, while the contribution of concrete represented 60 % to 80 % of total joint strength by using the Chinese specification. Improving the mechanical properties of concrete could effectively enhance the joint behavior. In Chinese specification, the contribution of stirrups may be overestimated since all the stirrups were assumed to reach the yield strength. This research could provide a reference for the future design and application of the proposed joint.
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