Consideration of Soil Temperature in the Modeling of Early-Age Mass Concrete Slab

Abstract

Modeling the structural behavior of concrete at early ages is one of the most challenging, yet fundamental, tasks for civil engineers working on mass concrete. To obtain a reasonably accurate model, a number of factors should be taken into account. Considerations should include both external influences as well as the changes occurring in the complex structure itself. The modeling of an early-age concrete massive slab requires the proper assignment of initial conditions, including the initial temperature of the analyzed element and the adjacent structures. The temperature distribution in the subsoil is the factor analyzed in this paper. The aim of the study is the determination of the temperature distribution in the ground, which is useful in the process related to the acquisition of the most accurate model of the analyzed structure and reflects the actual conditions in the numerical model. For this purpose, the analytical method described in the literature was applied and subsequently evaluated on the basis of the numerical calculation. The performed calculations allow the estimation of the depth representing the range of the influence of the temperature in the ground and the values of the temperatures corresponding to the successive layers of the subsoil. Moreover, aiming the optimization of the numerical analysis of the massive foundation slab, the legitimacy of such detailed consideration of the temperature development in the underlying subsoil was evaluated by the comparison with the temperature distribution in the slab obtained with simplified consideration of the constant soil temperature.

Thermo-Mechanical Analysis of Mass Concrete Foundation Slabs at Early Age—Essential Aspects and Experiences from the FE Modelling

“…The initial temperature of each layer of the slab as well as the ambient temperature were taken based on the measurements ( Figure 2 ). The initial temperature profile in the subsoil, presented in ( Figure 5 , was determined based on the preliminary FE analysis [ 33 , 45 ]. The total time of the performed analysis was 28 days.…”

“…Therefore, it has been examined how the vertical and horizontal sizes of the subsoil interfere with the obtained thermal and stress results. The vertical dimension of the subsoil was evaluated in the preliminary FE study [ 33 , 45 ]. The results showed that a depth of 10 m is sufficient and does not affect the temperature and stress distributions in the slab.…”

“…In the first approach, an additional calculation step in which the FEA is performed only for the soil using the actual ambient temperature. The second approach is based on the analytical calculations of the temperature distribution in the soil [ 45 , 50 , 51 ]. Then, the obtained temperature distribution over the soil depth is set as the initial soil temperature in the FE model of the whole structure.…”