Experimental tests and numerical analyses on the shear performance of UHPC encased steel beams: Evaluation of shear strength formula

To develop a design method for the shear capacity of ultra-high-performance concrete (UHPC) encased steel beams, shear tests were conducted on nine beam specimens. The key parameters investigated were the shear span ratio, stirrup ratio, and the thickness of the steel web. Based on the experimental results, a finite element (FE) model of the beam was established to further analyze failure modes and shear mechanisms. Using both experimental data and extensive FE simulations, two predictive formulae for the shear capacity of UHPC encased steel beams was proposed. The tests showed that the shear-compressive failure occurred in all the beam specimens. The vertical peak load dropped by 15.5% when the shear span ratio increased from 1.04 to 2.46. Conversely, the vertical peak load of the beam specimens increased with the increase of the stirrup ratio and the steel web thickness. The average ratios of the two prediction formulas to the experimental values are 0.89 and 0.92 respectively, and the average ratios of the two prediction formulas to the finite element calculation values are also 0.96 and 0.95 respectively, indicating that the proposed prediction formulae for the shear capacity of the UHPC encased steel beam are reasonable and slightly conservative. The findings of this investigation provide experimental and theoretical support for the shear design of the UHPC encased steel beams.