Application of thermo-hydro-chemo-mechanical model for early age behaviour of concrete to experimental massive reinforced structures with strain–restraining system

Abstract

This paper presents the application of a thermo-hydro-chemo-mechanical (THCM) model to the design of actual massive structures with a system to restrain the strain at early age (thermal strains and autogenous shrinkage). The experimental campaign was performed in the French national project CEOS.fr. The modelling of early-age behaviour of reinforced concrete is first based on a hydration model, which is able to reproduce the variations of temperature, water content and mechanical properties according to hydration. Then a non-linear mechanical model is used (combining creep and damage models, both adapted to hardening concrete). The comparison between numerical results (obtained with a calculation time of around 12 h on an ordinary computer) shows that the models are able to reproduce the early-age behaviour of restrained reinforcement concrete structures (in terms of strains, global forces and crack patterns). Using steel-concrete interface elements (adapted to early age), the models are also able to reproduce the influence of reinforcement on cracking. IntroductionThe work presented here was performed in the context of the French national project CEOS (see introductory editorial of this special issue). The study is part of the second key component of the project dealing with the concrete behaviour under thermo-hydrochemo-mechanical (THCM) loads. One of the objectives of this component was to construct some massive structures with strain restraint in order to test and validate the THCM models available in the French scientific community for predicting the early-age cracking of concrete structures. Once validated, these THCM models were used in the last part of the project to perform some numerical parametric studies and a more precise analysis of the effect of the reinforcement on the crack pattern of massive structures at early age.In the international literature, several recent studies have focused on the finite element modelling of this early-age behaviour of massive concrete structures. However, many of them are more concerned with validating a thermal model and propose a purely numerical analysis of mechanical aspects, used to identify some characteristic features of early-age behaviour aspects (Azenha, Faria, & Ferreira, 2011;Lackner & Mang,

Concrete creep modelling for structural applications: non-linearity, multi-axiality, hydration, temperature and drying effects

“…This method allows to compute finite elements models with several thousand nodes in a reasonable time as illustrated in [37] or [38]. More accurate criteria to choose the optimal time step could certainly be derived from equations set (25), but the proposed one has been used with success by the authors.…”

Three-dimensional simulations of ageing concrete structures using a multiphase model formulation

“…6, whereas the single crack observed in the test program appears already after 3 days. For reference, it can be mentioned that two or more crack planes was observed for the other two beams of the CEOS.fr project [43]. However, these have different reinforcement content and were cast under different ambient conditions, so the results are not directly comparable.…”

“…6 was performed. In this simulation, a weak-zone is introduced in the mid-section as suggested by Buffo-Lacarriére et al [43] motivated by the high concentration of instrumentation at this location. The weakzone is introduced by reducing f þ 1 with 5 % over a length corresponding to a single mesh element.…”

“…Buffo-Lacarriére et al [21] summarizes the entire experimental set-up, procedure and results from the research project. Furthermore, the experiment has been investigated theoretically to validate different models for early-age concrete, both as part of the CEOS.fr project and presented in the literature, see for example [43][44][45][46]…”

Numerical requirements for the use of a THCM material model to the prediction of early age cracking risk of massive reinforced concrete structures

“…However, many of them are more concerned with validating a thermal model and propose a purely numerical analysis of mechanical aspects [4]- [6]. Only a few studies focused on early-age cracking and crack patterns are also compared [7]- [9] but as instrumentation of real case massive structures is difficult to perform, mechanical results at early age (strains) are not usually compared (only a few reference is available in the literature [2], [10]).…”