Numerical assessment of temperature effects on concrete failure behavior

This work focuses on the evaluation of temperature effects on concrete failure behavior and modes by means of a realistic thermodynamically consistent non-local poroplastic constitutive model, previously developed by the authors, which is modified in this work. In this regard, two original contributions are presented and discussed. Firstly, and based on significant published experimental results related to this very complex aspect such as the effects of temperature in concrete failure, a temperature dependent non-associated flow rule is introduced to the poroplastic constitutive model to more accurately account for the temperature dependent inelastic volumetric behavior of concrete in post-peak regime. This is crucial for improving overall model accuracy, particularly regarding the temperature effects on concrete released energy during degradation processes. Secondly, and more importantly, the explicit solution of the localization condition in terms of the critical hardening modulus is developed regarding the non-local poroplastic constitutive model reformulated in this work, which allows the analysis of localized failure modes in the form of discontinuous bifurcation of quasi-brittle porous materials like concrete under different temperature, hydraulic and stress state scenarios. Also numerical procedures are followed, which also allow the evaluation of temperature effects on the critical directions for localized failure or cracking which is performed in this work for a wide spectrum of stress states and temperatures. Both, undrained and drained hydraulic conditions are evaluated. The results in this work demonstrate the soundness of the proposed constitutive model modifications and of the derived explicit solution for the critical hardening modulus to accurately predict the temperature effects on both, concrete volumetric behavior, and on the failure modes and related critical cracking direction. They also demonstrate that concrete failure mode and critical localization directions are highly sensitive to temperature, particularly in the compressive regime.