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.

Automated summary

This study investigated the shear behavior of UHPC beams and found that the shear span to depth ratio is inversely proportional to the shear bearing capacity. A comparative study was conducted to evaluate the existing shear capacity prediction formulas and a new modified formula was proposed.