Analysis and design of axially loaded ring-beam joints connecting steel tubed-RC column and RC beams

Abstract

This work proposes a reinforced concrete (RC) ring-beam joint system for connecting circular tubed-reinforced concrete (TRC) columns and RC beams. In the joint zone, a thin-walled core steel tube is embedded to reduce the size of the RC ring beam, which is beneficial to construction convenience and architectural layout. A simplified model is established to allow for both the confinement effect of the core steel tube and the load-carrying capacity contribution of the ring beam. This simplified model enables the analysis of the load-resisting mechanism underlying the proposed joint, along with the derivation of an equation for its axial compression capacity. Furthermore, a high-fidelity finite element model is established and validated through test results. Parameter analysis was then conducted to assess the effects of concrete strength, yield strength of the steel tube, thickness of the steel tube, and height of the core steel tube on both the core steel tube stresses and the axial load-capacity of the joints. Formulas for calculating circumferential stresses and longitudinal stresses of the core steel tube are also proposed. The predictions agree well with the results obtained from test and parameter analysis. Lastly, design recommendations and procedures for the joint are proposed, and a design example is given with three types of joints details. The results demonstrate the advantages of the proposed joint in terms of convenient construction and favorable cost-effectiveness.