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- Dahlblom, Ola
(author)
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Constitutive Modelling and Finite Element Analysis of Concrete Structures with Regard to Environmental Influence
- 1987. - 1
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Doctoral thesis (other academic/artistic)abstract
- A constitutive model for concrete is formulated. Tensile fracture is described using a smeared crack approach where the fracrure energy is considered and the shear stiffneess in the cracked region is gradually reduced as crackling develops. Environmentally induced strain due to variation of moisture and temperature is taken into account and may be made dependent on the stress state. Creep is modelled by a rate type formulation.In order to clarify whether the fracture description is accurate in reflecting the input value of fracture energy per unit area a concrete tension specimen is simulated, and good results are achieved.The behaviour of a non-loaded drying concrete specimen is simulated by a theoretical analysis, in order to find to what extent the overall specimen behaviour is influenced by the non-uniform stress state caused by drying. According to the analysis the deformation after a long time differs only slightly from the material contraction due to drying.According to several experimental observations the deformation of a loaded drying specimen is significantly larger than the sum of the deformation of a non-loaded drying specimen and the deformation of a loaded non-drying specimen. The excess deformation is often referred to as stress induced shrinkage or as drying induced creep. A theoretical simulation af a specimen results in the conclusion that the effect is largely a result of stress dependence of the moisture induced strain.
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