Numerical Modelling Approach for UHPFRC Members Including Crack Spacing Formulations

Ultra-high performance fiber-reinforced concrete (UHPFRC) possesses excellent mechanical properties and durability. The steel fibers in the concrete result in significant post-cracking tensile resistance and enhanced crack control. However, while UHPFRC is a promising material for the construction of new (and repair of existing) infrastructure, its application is still limited—in part due to the lack of numerical models with the capacity to simulate its complex behavior. To help overcome this challenge, this study proposes a numerical material modeling approach for the nonlinear finite element analysis of UHPFRC. The approach aims to provide a general applicability to model both shear- and flexure-critical members made from strain-softening or -hardening UHPFRC, while still using simple equations. This objective can be achieved by establishing a comprehensive set of crack spacing formulations and modeling recommendations to capture the unique behavior of UHPFRC. The crack spacing estimates are used together with the Diverse Embedment Model for FRC, which is extended here for the modeling of UHPFRC. When applied to 29 flexure- and shear-critical specimens, the proposed modeling approach accurately simulates the experimental responses with an average of 1.04 and a coefficient of variation of 10.2% for the experimental-to-predicted strength ratios.