Thermo-mechanical analysis of mass concrete foundation slabs at early age - essential aspects and experiences from the FE modelling

In this paper, the focus is placed on essential aspects of finite element modelling of thermo-mechanical behaviour of massive foundation slabs at early ages. Basic decision-making issues are discussed in this work: the potential need to explicitly consider the casting process in the modelling, the necessary size of the underlying soil to be modelled and the size of the FE mesh, and the need of considering daily changes of the environmental temperature and the temperature distribution over the depth of the soil. Next, the contribution of shrinkage to early age stresses, the role of the reinforcement, and the type of mechanical model are investigated. Comparative analyses aiming to investigate the most important aspects of the FE model and some possible simplifications with negligible effect on the results are made on the example of a massive foundation slab. Finally, the results are summarized with recommendations for creating the FE models of massive slabs at early ages.This research was funded by: Silesian University of Technology [project 03/060/RGJ22/1029] and the Portuguese Foundation for Science and Technology (FCT) to the Research Project IntegraCrete PTDC/ECM-EST/1056/2014 [POCI-01-0145-FEDER-016841], the Research Unit ISISE [POCI-01-0145- FEDER-007633]. The support of COST Action TU1404 in the networking actions (particularly the Short Term Scientific Mission of the 1st author) necessary for this work is also acknowledged

Extended Round Robin Testing program of COST Action TU1404 – lessons learned from the initial experimental phase

The extended round robin testing program (RRT + ) is used in the Working Group 1 of the COST Action TU1404 as a fundamental mechanism: i) to validate advanced, non- standardised experimental techniques for testing cement-based materials and structures, ii) to benchmark different sustainable variations of concrete mixes prepared with mineral admixtures, recycled materials and/or by-products, and iii) to obtain input data for a range of concrete properties which could serve designers and engineers to better predict lifespan, durability, and serviceability of concrete struct ures. With a total of 45 laboratories from Europe, Japan and Canada, performing over 50 test methods on the same concrete mix, it presents one of the most extensive initiatives for joint testing of cement-based materials. The RRT + is divided into two phases: the initial and main experimental phases. During the initial phase, an ordinary concrete mix is prepared using the same constituting materials and following identical preconditioning, preparation, conditioning and test procedures. Even though the framework is identical and potential external causes of deviations are limited, concrete is prepared in different laboratories and some scatter in results can be expected. This paper describes the observations during the initial experimental phase and discusses methods including statistical analysis performed to understand the scatter and results obtainedEDF, France, CEVA Logistics, Austria and Germany, OeBB Infra, Austria, Staten Vegvesen, Norway and Schleibinger Gerate, German

Consideration of soil temperature in the modelling of early-age mass concrete slab

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.The publication is financed by BKM-547/RB6/2018 resources. Funding provided by the Portuguese Foundation for Science and Technology (FCT) to the Research Project IntegraCrete PTDC/ECM EST/1056/2014 (POCI-01-0145-FEDER-016841), as well to the Research Unit ISISE (POCI-01- 0145-FEDER-007633) is also gratefully acknowledged

3D Thermo-hygro-mechanical approach for simulation of the cracking behaviour of a RC slab under the combined effects of applied loads and restrained shrinkage

The design of reinforced concrete (RC) structures that meet safety, functionality and aesthetic requirements during their lifespan, without unforeseen maintenance costs, depends on adequate design practices that allow engineers to properly control and predict crack widths on concrete. Even though there is a wide body of design codes and recommendations providing methodologies for reinforcement design on elements subjected to applied loads or imposed deformations, they do not provide unambiguous rules for RC structures under the combined effect of these actions, which is a typical situation in RC slabs applied in buildings. This is motivated by the lack of knowledge about the complex interactions that take place between self-imposed deformations, viscoelasticity and the effect of applied loads. This work intends to contribute for deepening the knowledge on this subject by performing a 3D thermo-hygro-mechanical analysis on a highly restrained slab in service load conditions, in which the temperature and moisture fields of the slab are determined in order to take into account the non-uniform distribution of stresses (in space and time) due to hydration and drying shrinkage. This analysis shows that the real restraint forces applied to the slab are in fact just a mere fraction of the those that would be expected in a hypothetical tie subjected to total restraint due to the loss of rigidity caused by crack development induced by a combination of flexural and self-induced stressesPortuguese Foundation for Science and Technology (FCT) to the Research Project IntegraCrete (PTDC/ECM-EST/1056/2014 -POCI-01-0145-FEDER-016841) as well to the Research Units ISISE (POCI-01-0145-FEDER-007633) and CONSTRUCT (POCI-01-0145-FEDER-0074

Proposal of a test set up for simultaneous application of axial restraint and vertical loads to slab-like specimens: sizing principles and application

Cracking control in reinforced concrete (RC) is a key factor to ensure proper service life behaviour. However, current design recommendations are unable to provide straightforward methodologies for crack width prediction in RC structures subjected to the combined effects of applied loads and restrained deformations, which is a common situation in civil engineering. This is motivated by the lack of knowledge about the complex interactions that take place between self-imposed deformations, viscoelasticity and the effects of applied loads in the process of crack development. A major challenge in studying these combined effects is the validation of numerical simulations with real scale experimental data. For that purpose, an experimental system for testing real scale RC slabs subjected to the above-mentioned conditions was developed. This system is capable of inducing a prescribed axial restraint to the slab, in correspondence to a high restraint degree that induces cracking in view of expectable shrinkage. At the same time, the setup enables the application of vertical loads. The experimental results obtained in this work allowed for the validation of the test setup, as well as the suitability of the slab geometry and reinforcement.This work was financially supported by: Project POCI-01-0145-FEDER-007457 (CONSTRUCT - Institute of R&D in Structures and Construction) and by project POCI-01- 0145-FEDER-007633 (ISISE), funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI), and by national funds through FCT - Fundação para a Ciência e a Tecnologia. FCT and FEDER (COMPETE2020) are also acknowledged for the funding of the research project IntegraCrete PTDC/ECMEST/1056/2014 (POCI-01-0145-FEDER-016841). The financial support of COST Action TU1404 through its several networking instruments is also gratefully acknowledged.info:eu-repo/semantics/publishedVersio