Flexural behavior of U-shaped steel-concrete composite beams with combined connector based on steel-bars truss

Abstract

This paper discusses a new type of U-shaped steel-concrete composite beam (USCCB) with steel-bars truss connector to investigate its flexural behavior through experimental and theoretical analysis. Four-point bending tests were conducted on six specimens that were distinguished according to shear connectors: steel-bars truss, inverted U-shaped rebar, stud, and their combination. The test results show that USCCBs with inverted U-shaped rebar and the combined connector of steel-bars truss and inverted U-shaped rebar exhibit typical bending failure mode (ductile failure, μ > 10), while that with studs and the combined connector of steel-bars truss and studs show certain brittle failure mode (μ < 5). Specimen using only steel-bars truss connector has good ductility (μ >10), but shows a marked insufficiency of shear interaction (η < 1) due to the lowest bearing capacity, 510 kN. The adequate transverse reinforcement ratio (0.63 %) of the steel-bars truss and the triangular three-dimensional structure could effectively strengthen the anti-splitting ability of the concrete deck. USCCB with only steel-bars truss connector should be designed as partially composite beams, but some inverted U-shaped rebars can be arranged to enhance the shear resistance of the interface accordingly. Additionally, the failure of the stud connector is not conducive to the ductility of USCCB (μ < 5). For structural safety, it is not recommended to use studs in whole or in part as the shear connectors of USCCB with full shear connection. The design methods according to full-section plasticity theory have a good prediction for the ultimate flexural capacity of USCCB.