A modeling strategy for the flexural performance prediction of UHPC beams accounting for variability of properties

The Reinforcing Ratio (RR) is a major factor governing the ductility of UHPC beams. Previous works have demonstrated that beams with low RR (less than2.0 %) exhibit a sudden drop in load after the peak. The first part of the present paper reports the results of an experimental program comparing the responses of beams made with conventional concrete and UHPC for two different RR (0.44 % and 1.78 %). The results confirm that UHPC increases the load-carrying capacity by up to 135 %, allowing for multiple cracking with finer cracks. Using the post-peak drift method, it is shown that the ductility of the UHPC beams with RR = 1.78 % was about 2.6 times greater than that for RR = 0.44 %. In the second part of the work, a numerical finite element modeling strategy accounting for the inhomogeneous fiber distribution is developed and validated against the experiments. It is shown that the homogenous models cannot simulate the crack localization associated with weak regions in UHPC and, therefore, overpredict member ductility. Finally, the numerical model is used to design optimized UHPC beams with the same strength as the tested reinforced concrete beams. It is shown that half of the cross-section width is necessary, resulting in greater RR values that ultimately increase the ductility by 275 % and 167 %, respectively, for beams reinforced with RR = 0.44 % and 1.78 %.

Automated summary

This study investigates the influence of the reinforcing ratio on the ductility of UHPC beams through experiments and numerical simulations. The results demonstrate that UHPC beams can increase the load-carrying capacity by up to 135% and generate finer cracks. The numerical simulations validate that homogeneous models cannot accurately simulate crack localization in weak regions of UHPC, leading to overestimated ductility. Additionally, optimized UHPC beams with the same strength as reinforced concrete beams are designed using the numerical model, resulting in a ductility increase of 275% and 167% for beams reinforced with RR = 0.44% and 1.78%, respectively.