Direct procedure to characterize the tensile constitutive behavior of strain-softening and strain-hardening UHPFRC

There is a need to establish a complete process to characterize Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) in both strain-hardening and strain-softening tensile behavior. This process should be simple and easy to apply so that its application is direct. Therefore, this paper presents the development of a complete process to obtain the tensile constitutive parameters of UHPFRC. A simplified inverse analysis based on fourpoint bending tests (4PBT) to derive the tensile material properties of strain-hardening UHPFRC was adapted to be applied in the event of strain softening using a nonlinear finite element model (NLFEM). To fulfill this objective, an extensive experimental program was run with 227 UHPFRC specimens tested in 4PBT that exhibited strain-softening and strain-hardening tensile responses. As a reference, the characteristic UHPFRC tensile constitutive behavior was obtained. Finally, a predictive application capable of predicting tensile behavior using the experimental 4PBT curve as input was developed with the experimental database.