Experimental investigation and prediction of shear capacity for UHPC beams

As a novel green material, Ultra-high performance concrete (UHPC) has favourable application prospects. Currently, the ultimate shear capacity design of UHPC beam is carried out using empirical or semi-empirical methods. These methods involve approximations, which are not always reliable, and their scope of application is limited. In the view of this, a shear test was conducted on eight rectangular UHPC beams. The shear span to depth ratio (1.5, 2, 2.5, 3) and longitudinal reinforcement ratio (5.6%,6.2%,7.1%) were designated as the experimental parameters. In addition, the failure mode, shear capacity and crack pattern were observed and analysed. The results indicated that the shear-span to depth ratio is inversely proportional to the shear bearing capacity and is dominant to the shear failure mode. Although a higher longitudinal reinforcement ratio can slightly improve the shear capacity, it has no impact on the shear failure mode. Based on the outcome of this work, a comparative study was performed to evaluate the current shear capacity prediction formulas, and a new modified formula was proposed. The proposed design equation was compared to the results from literatures, confirming that the modified equation is accurate and reliable with mean ratio 1.03 and a better the proportion of the variation of 0.96.