Coupled thermomechanical analysis of concrete hardening

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2015

Öğrenci: HALİL İBRAHİM ANDİÇ

Eş Danışman: SERDAR GÖKTEPE, İSMAİL ÖZGÜR YAMAN

Özet:

Thermomechanically coupled modeling of fresh concrete allows us to predict the interaction between thermal and mechanical mechanisms throughout the setting and hardening process. Because of cement hydration, an excessive temperature increase may occur in the interior regions of mass concrete structures. This temperature increase along with the thermal boundary conditions may result in thermal gradients within concrete structures. Owing to the thermal gradients and mechanical constraints, thermally induced stress concentrations may occur. These often manifest themselves in the form of undesired cracks. These cracks eventually deteriorate the concrete unity and shorten the service life of such structures. Although there are several conventional techniques devised to avoid thermal gradients and cracking, they do not always provide an efficient and thorough protection. In this thesis, we propose a thermomechanically coupled finite element model to predict the potential regions of cracking. To this end, we develop a thermomechanical constitutive model to account for the strong couplings in early-age concrete. The local temperature field in concrete is solved through the transient heat conduction equation where the heat generation due to hydration enters as an internal heat source. The stress concentrations, however, are calculated by solving the balance of linear momentum with a constitutive model that takes into account the dependency of the material parameters on the degree of hydration and other time-dependent phenomena. We anticipate that the proposed approach can be used to conduct thermomechanically coupled analyses of important mass concrete structures including dams, mass foundations and viaducts to quantify the risk of thermal cracking.