Identification of the hygro-thermo-chemical-mechanical model parameters of concrete through inverse analysis

A wide range of parameters is required in input when applying hygro-thermo-chemical-mechanical models to concrete components with the aim of determining the variations over time of temperature, relative humidity and shrinkage induced deformations. While a sub-set of these material parameters can be evaluated on the basis of the concrete mix specifications or from literature data, this paper presents a robust inverse analysis procedure for the identification of the remaining sub-set of parameters that are characterised by a large variability and, in some cases, do not have a precise physical meaning and are not amenable to a direct measurement. The particularity of this paper is to propose different strategies for the characterisation of these material parameters that account for the presence of different exposure conditions, as these affect the outcomes and requirements of the parameter identification procedure. After introducing the adopted hygro-thermo-chemical-mechanical model, representative results of an extensive sensitivity analysis are presented in the first part of the paper to give insight into most effective number, location and duration of measurements to be used in input of the inverse analysis. The inverse analysis procedure is then presented and applied to a number of selected scenarios to highlight its robustness considering different boundary conditions in terms of external temperature and relative humidity surrounding the concrete. The ability to characterise these parameters will support a wider use of these hygro-thermo-chemical-mechanical models, especially for those applications in which humidity and temperature profiles significantly influence the structural response, for example when predicting curling in industrial pavements and non-uniform shrinkage profiles in composite steel-concrete slabs.