Keywords: hydro-thermo-mechanical analysis, hydration, heat transport, multiscale model, concrete, affinity model.

This paper presents the hydro-thermo-mechanical model for analysis of reinforced concrete structures applicable in engineering practice. The analysis consists of two steps. Firstly, moisture and heat transport analysis is carried out [1]. This yields moisture and temperature fields at all material point. Secondly, these results are imported and used in a mechanical problem in the form of a staggered solution. The whole model has been implemented in the ATENA software [2], which is used in the validation stage.

The heat and moisture transport analysis is based on the models by Kuenzel and Cervera [3,4]. Its objective is an accurate prediction of the hydration heat generated during concrete hydration. It employs an affinity hydration model with four parameters. They can be calibrated either experimentally using isothermal calorimetry or by using microscale hydration models, such as CEMHYD3D [5], accounting for the particle size distribution of cement, the chemical composition of the cement, as well as temperature and moisture history in concrete.

The mechanical part encompasses nonlinear analysis that includes thermal dilatancy and optionally material creep and shrinkage [2]. The previously computed temperature and moisture histories are used to improve the accuracy of the creep prediction models, calculate thermal related element load, and include the effect of temperature on material behaviour in the fire analyses etc.

The model for transport and mechanical analysis need not be the same. Different finite element meshes and element types can be used. A special mapping procedure is used to reduce the number of temperature and moisture histories in the material points and thereby speed up the execution.

The second part of the paper validates the multi-scale model presented using a series of examples. It shows that the model provides good results for reasonable computing cost. It can be used widely in engineering practice.

1

L. Jendele, V. Šmilauer, J. Cervenka, "Multi-scale Analysis of Heat Transport in Hydrating Concrete Structures", in B.H.V. Topping, Y. Tsompanakis, (Editors), "Proceedings of the Thirteenth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 124, 2011. doi:10.4203/ccp.96.124

2

V. Cervenka, J. Cervenka, L. Jendele, "Atena Program Documentation, Part 1 Theory", Cervenka Consl., Prague, 2000-2007.

3

M. Cervera, J. Oliver, T. Prato, "Thermo-chemo-mechanical Model for Concrete. I: Hydration and Aging", Jour. Eng. Mech. ASCE, 125(9), 1018-1027, 1999. doi:10.1061/(ASCE)0733-9399(1999)125:9(1018)

4

H.M. Kuenzel, "Simultaneous Heat and Moisture Transport in Building Components. 1D and 2D calculation using simple parameters", Fraunhofer Inst. of Building Physics, Stuttgart, 1995.

5

D.P. Bentz, "CEMHYD3D: A Three-Dimensional Cement Hydration and Microstructure Development Modeling Package. Version 3.0", NIST Building and Fire Research Laboratory, 2005.

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