Methodology to estimate the minimum number of experiments and key microstructural parameters in macroscopic strength properties evaluation

A novel methodology, based on the theory of fuzzy sets, to obtain materials with pre‐defined sets of strength properties has been analysed from the position of identifying the necessary and sufficient number of experiments needed to predict these macro characteristics and establishing which micro parameters significantly influence the macroscale results. The procedure to estimate, with a user‐defined degree of accuracy, the minimum number of experiments and significant micro parameters has been tested and verified using experimental data, obtained from digital images of material microsections under different heat treatment conditions while analysing strength properties of reinforcing steel. The results confirm the possibility of using the developed methodologies for the performance properties evaluation of materials based on the minimum number of experiments and identification of the key grain‐phase parameters

A thermo-mechanical interface model for simulating the bond behaviour of FRP strips glued to concrete substrates exposed to elevated temperature

This paper proposes a model aimed at simulating the bond behaviour of Fiber Reinforced Polymer (FRP) laminates glued to concrete substrates and exposed to high temperature. Based on a previous model already formulated by one of the authors and available in the scientific literature, the present paper proposes a theoretical model formulated within the general framework of Fracture Mechanics and Plasticity-based concepts. Particularly, the aforementioned model is extended herein to consider the thermal effects, through a temperature-based scaling function affecting the strength parameters and softening rules which define the failure surface and the post-cracking response of FRP-concrete joints. The mechanical soundness of the proposed model is demonstrated by the very good agreement between some experimental results taken from the scientific literature on FRP-to-concrete systems tested in pull-out loading at normal and elevated temperature and the corresponding theoretical simulations.Fil: Caggiano, Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires; ArgentinaFil: Said Schicchi, Diego. Stiftung Institut fur Werkstofftechnik; Alemani

A porous-based discontinuous model for ductile fracture in metals

A discontinuous model aimed at modeling ductile fracture for metals is presented. The effect of microvoid nucleation, growth and coalescence on the inelastic response of structural metals is modeled through a suitable interface proposal for cracking analysis. The discontinuos proposal is completely conceived within the general framework of fracture mechanics and porous plasticity concepts. The porosity affects the strength parameters and softening rules defining the failure initiation and post-cracking response of the interface. To demonstrate the soundness and capability of the proposed formulation, a comparative study against numerical simulations obtainable from a classical well-known continuous approach for capturing ductile fracture, based on finite element analysis, is presented.Fil: Said Schicchi, Diego. Stiftung Institut für Werkstofftechnik; AlemaniaFil: Caggiano, Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Meso-scale modeling of hybrid industrial/recycled steel fiber-reinforced concrete

This paper investigates the mechanical behavior of fiber-reinforced concrete (FRC) and focusses on the quantifying the effect of replacing Industrial Steel Fibers (ISFs), commonly adopted as spread reinforcement in FRC, with Recycled Steel Fibers (RSFs) recovered from waste tires. More specifically, it analyses the bending behavior of FRC beams reinforced with a constant volume fraction of steel fibers and variable proportions of ISFs and RSFs. First, a numerical model is formulated by assuming that FRC behaves as a multi-phase medium, where the nonlinear material behavior of the concrete matrix is simulated by following a discrete-crack approach for meso-scale analysis. Then, steel fibers are modeled as short cables, randomly distributed and embedded within the concrete matrix. The internal forces in the steel fibers are obtained by considering both bond-slip behavior and dowel effect. Comparisons between experimental results, obtained by the authors in a previous study, and numerical simulations, performed by means of the proposed numerical model, are discussed: the significant predictive capability of the latter confirms the soundness of the mechanical assumptions on which the model is based. Moreover, the possibility of predicting the behavior of FRC with Hybrid Recycled/Industrial Fibers paves the way toward the actual application of this sustainable material in real applications

Meso-scale modeling of hybrid industrial/recycled steel fiber-reinforced concrete

This paper investigates the mechanical behavior of fiber-reinforced concrete (FRC) and focusses on the quantifying the effect of replacing Industrial Steel Fibers (ISFs), commonly adopted as spread reinforcement in FRC, with Recycled Steel Fibers (RSFs) recovered from waste tires. More specifically, it analyses the bending behavior of FRC beams reinforced with a constant volume fraction of steel fibers and variable proportions of ISFs and RSFs. First, a numerical model is formulated by assuming that FRC behaves as a multi-phase medium, where the nonlinear material behavior of the concrete matrix is simulated by following a discrete-crack approach for meso-scale analysis. Then, steel fibers are modeled as short cables, randomly distributed and embedded within the concrete matrix. The internal forces in the steel fibers are obtained by considering both bond-slip behavior and dowel effect. Comparisons between experimental results, obtained by the authors in a previous study, and numerical simulations, performed by means of the proposed numerical model, are discussed: the significant predictive capability of the latter confirms the soundness of the mechanical assumptions on which the model is based. Moreover, the possibility of predicting the behavior of FRC with Hybrid Recycled/Industrial Fibers paves the way toward the actual application of this sustainable material in real applications

Strength and durability of concrete subjected to high temperature: continuous and discrete constitutive approaches

none4The action of high temperature in concrete is a field of much interest and attention due to its strong influence in strength, durability and serviceability conditions. Long-term exposures to high temperature fields strongly affect the most relevant mechanical properties of concrete materials such as cohesion, friction, stiffness and strength. In this work, two alternatives approaches for the analysis of failure behavior of concrete subjected to high temperatures are discussed and their predictions analyzed. Specifically, a thermodynamic gradient poroplastic model based on the continuous or smeared-crack approach and an interface model based on the discrete crack approach are developed. After describing the main aspects of both models, this work focuses on the analysis of their results in terms of the degradation of concrete durability and strength capacities when subjected to severe thermal fields. The results demonstrate the comparative advantages of the discrete approach to analyze at both the macroscopic and mesoscopic scale the complex degradation processes of concrete constituents at high temperature, thanks to the robustness, stability and overall simplicity of the discrete model approach. Furthermore, the results show the capabilities of the continuous model to analyze the durability degradation of concrete at material level.mixedEtse G.; Ripani M.; Caggiano A.; Schicchi D.S.Etse, G.; Ripani, M.; Caggiano, A.; Schicchi, D. S