A modified space truss analogy model for ultimate torsional capacity of ultra-high-performance concrete solid and box beams

This paper presents an analytical model using a modified space truss analogy for predicting the ultimate torsional capacity of reinforced ultra-high-performance concrete (R-UHPC) beams. Both solid and box beams are considered. The credibility of the proposed model is evaluated by comparing the theoretical predictions of the ultimate torsional capacity and its corresponding twist (T_u-α_u) to experimental results of several R-UHPC beams (solid and box beams) available in the literature. The results are also compared with the calculation of the existing models. The comparisons show that the proposed model gives acceptable predictions of the ultimate limit torsional capacity of R-UHPC beams and the corresponding twist angle and offers better accuracy than the existing analytical models. Additionally, a parametric study was carried out to determine factors that influence the ultimate torsional capacity. The result shows that the ultimate torsional capacity is not just improved by the increase of the tensile strength of UHPC but also increased by the increase of the reinforcements (transversal and longitudinal).