Flexural and shear capacities of semi-precast RC beams with embedded steel connections

This paper proposes two types of semi-precast reinforced-concrete (RC) beams with steel connections embedded at each end. The proposed beams are designed to address the problems of complex detailing and construction difficulties between concrete-filled steel tubular columns and conventional RC beams. The proposed beams are composed of two steel I-beams partially embedded into the end sections of the RC beams. Full-scale experiments were carried out on the two proposed beams and a reference conventional RC beam to study the failure mode, crack propagation and flexural and shear strengths. Results indicated that the flexural strength of the proposed beams was well predicted by the current design codes on concrete structures including GB 50010, ACI 318-11 and BS EN 1992-1-1 (Eurocode 2). To further examine the shear behaviour of proposed beams, six experiments with two different shear span-to-depth ratios were conducted. The influence of the embedded steel connections on the shear behaviour was investigated and a correction coefficient for the shear span-to-depth ratio was proposed. Based on the current design codes on concrete structures, modified equations for calculating the shear strength were proposed. Finite-element methodology was also adopted to simulate the structural behaviour of the embedded steel connections under combined bending and shear force. Based on numerical findings, design methods for the embedded steel connections were recommended.