Numerical validation of a simplified inverse analysis method to characterize the tensile properties in strain-softening UHPFRC

Abstract

In previous research a simplified closed-form non-linear hinge model based on the Third Point Bending Test (TPBT) developed by the authors to derive the tensile material properties of Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) was numerically validated. This simplified non-linear hinge model was calibrated for UHPFRC that exhibits strain-hardening constitutive behavior. The aim of this work is the numerical validation of the simplified inverse analysis method to characterize the tensile properties of UHPFRC even with those UHPFRCs which exhibit strain-softening behavior. To get this objective a Finite Element Model (FEM) is carried out. The parameters to characterize the concrete properties from the simplified inverse analysis method by means of TPBT are used in the numerical modelling. The constitutive model for UHPFRC is modelled using a discrete crack approach for the macrocrack position. Different parameters are analysed to quantify the accuracy of the FEM. As a result, the model shows conservative load-deflection response when it is compared to the experimental curves.

Tensile behaviour identification in Ultra-High Performance Fibre Reinforced Cementitious Composites: indirect tension tests and back analysis of flexural test results

“…The identification of the stress-strain law in direct tension is of primary importance to generalize the results coming from experimental testing, and several approaches can be found in the literature [13][14][15][16][17][18]. In this regards, direct tensile test is generally considered the most reliable test, but it is rather complex to be implemented and very sensitive to possible defects and eccentricity in loading [16].…”

“…It is worth remarking that the COD-strain conversion is performed with reference to the LVDT gauge length, this translating in the assumption of non-linear hinge in the multiple-cracking region [16][17][18]. This numerical procedure is called in the following as 1D approach (1) and it is represented in the plots of Figs.…”

Inverse Analysis of R-UHPFRC Beams to Determine the Flexural Response under Service Loading and at Ultimate Resistance

“…In this way, the inherent variation of UHPFRC properties in different elements (Oesterlee et al 2009) can be quantified. Several inverse analysis methods are available, using simplified closed-form solutions (AFGC 2013;López et al 2015López et al , 2016Qian and Li 2008) as well as numerical (Baby et al 2013; de Oliveira e Sousa and Gettu 2006; Denarié et al 2017), analytical (Baril et al 2016), and finite-element methods (Mezquida-Alcaraz et al 2019;Tailhan et al 2004), taking into account scatter of material properties in members (Rossi et al 2015). Inverse analysis also can be done for larger members (Pan et al 2016;.…”

Numerical Modelling of UHPFRC: from the Material to the Structural Element

“…For this purpose, it is chosen an inverse analysis method that was properly developed by the research group for UHPFRC which exhibits strain-hardening behaviour: a simplified Four-Point Inverse Analysis method (4P-IA) that is developed in (López 2017;López et al 2017) and summarised in chapter 3 of this doctoral thesis. This method has also been calibrated and adapted for UHPFRC exhibiting strain-softening in chapter 5 of this work and in (Mezquida-Alcaraz et al 2019b establishing a softening correction for f tu (f tuc ). According to 4P-IA, to define the tensile behaviour, it is necessary to select four specific key points from the experimental 4PBT equivalent bending stress-displacement at the mid-span curve.…”

“…). These models start from a NLFEM defined in this work in chapter 3, chapter 4 and chapter 5 and in (Mezquida-Alcaraz et al 2018b, 2021).…”