Due to the extensive use of reinforced concrete as building materials in the last century, even in severe and aggressive environment, the demand for designing durable structure has increased together with the need for developing reliable and appropriate models which allow the prediction of concrete behaviour on time. One of the most severe types of deterioration in r.c. structures is associated to the volume expansion of concrete caused by frost attack. Actually in cold environments, freezing and thawing can be detrimental for a brittle material such as concrete, especially related to its porosity characteristics. The causes and mechanisms of frost damaging process have been dealt with by several research papers, but very little attention has been given to the effect of frost attack on the material characteristics and on the bond properties of concrete, see e.g. [1] where it has been shown that the relations between compressive and tensile strength for undamaged concrete cannot be used directly for frost-damaged concrete. In this paper the environmental-mechanical coupled damage model, based on the works of Saetta et al [2] – [3] and Tesser et al. [4] was developed accounting for the deterioration of concrete during the freeze-thawing (F/T) process. A 4-node finite element based on Reissner-Mindlin thick plate formulation with Mixed Interpolation of Tensorial Components is used. Stress resultants are evaluated via numerical integration of the concrete plastic damage model over the thickness. Moreover an enhanced formulation [5] of the environmental damage is presented, which takes into account the effect of the number of F/T cycles on the value of concrete strength and ductility. In particular both uniaxial and biaxial experimental tests of concrete subjected to frost damage were considered and an optimization technique was adopted to calibrate the coupled damage model. Test results showed a significant influence of freeze–thaw cycles on the compressive strength and on biaxial behaviour. Finally the paper presents a case study able to evaluate the model capabilities.
A coupled damage model for the structural analysis of r.c. structures exposed to freeze–thaw cycles
BERTO, LUISA;TALLEDO, DIEGO ALEJANDRO
2013-01-01
Abstract
Due to the extensive use of reinforced concrete as building materials in the last century, even in severe and aggressive environment, the demand for designing durable structure has increased together with the need for developing reliable and appropriate models which allow the prediction of concrete behaviour on time. One of the most severe types of deterioration in r.c. structures is associated to the volume expansion of concrete caused by frost attack. Actually in cold environments, freezing and thawing can be detrimental for a brittle material such as concrete, especially related to its porosity characteristics. The causes and mechanisms of frost damaging process have been dealt with by several research papers, but very little attention has been given to the effect of frost attack on the material characteristics and on the bond properties of concrete, see e.g. [1] where it has been shown that the relations between compressive and tensile strength for undamaged concrete cannot be used directly for frost-damaged concrete. In this paper the environmental-mechanical coupled damage model, based on the works of Saetta et al [2] – [3] and Tesser et al. [4] was developed accounting for the deterioration of concrete during the freeze-thawing (F/T) process. A 4-node finite element based on Reissner-Mindlin thick plate formulation with Mixed Interpolation of Tensorial Components is used. Stress resultants are evaluated via numerical integration of the concrete plastic damage model over the thickness. Moreover an enhanced formulation [5] of the environmental damage is presented, which takes into account the effect of the number of F/T cycles on the value of concrete strength and ductility. In particular both uniaxial and biaxial experimental tests of concrete subjected to frost damage were considered and an optimization technique was adopted to calibrate the coupled damage model. Test results showed a significant influence of freeze–thaw cycles on the compressive strength and on biaxial behaviour. Finally the paper presents a case study able to evaluate the model capabilities.
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