Shear behavior of thin concrete-encased honeycomb steel composite beam

Traditional steel-concrete composite beams usually require thick concrete cover, which leads to high reinforcement demand, high self-weight, susceptibility to cracking, complex joint detailing, and difficulties in prefabricated construction. The slab is placed above the top flange of the steel beam, resulting in a large beam-slab depth. A novel thin concrete-encased honeycomb steel composite beam (TCEHSB) is proposed. The lower flange and approximately two-thirds of the web of the honeycomb steel beam are encased in factory-prefabricated concrete, which features a low longitudinal reinforcement ratio, unclosed stirrups, and thin concrete cover outside the steel flange. The top surface of concrete can support the profiled steel sheet composite floor. An integrated approach combining experimental investigation, numerical simulation, and theoretical analysis was adopted. Four push-out specimens were designed to investigate the effects of steel beam type and stud number on the failure mode, interfacial bond behavior, and slip response. Compared with the solid-web beam, the honeycombed beam exhibited a 19.96% reduction in shear capacity due to web openings, whereas the peak slip decreased by 50%. Both specimens ultimately exhibited slip failure, and the failure load was approximately 20% of the peak load. After additional studs were arranged on the flange of the honeycombed beam, the cracking shear resistance of the slab increased by 225.64%, and the final failure mode changed to stud shear failure. Based on the load-slip curves and strain distribution of the steel beam and studs, the mechanisms of concrete cracking and stud force transfer were clarified, and the calculation method for stud shear resistance was verified. A steel-concrete bond-slip constitutive model and a corresponding nonlinear spring numerical method were further proposed. The developed method can accurately reproduce the steel-concrete bond behavior and provides a theoretical basis for interface design and engineering application of the proposed TCEHSB.