Basic Creep of Young Concrete - Sensitivity in the Evaluation Method

• Main Authors: Ekmat, Benar, Hermes, Natalea
• Format: Bachelor Thesis
• Language: English
• Published: KTH, Betongbyggnad 2019
• Subjects: thermal cracking; young concrete; creep; Linear Logarithmic Model; temperature development; average strain; sensitivity; Temperatursprickor; ung betong; krypning; Linjär Logaritmisk Modell; temperaturutveckling; töjning; känslighet; Architectural Engineering; Arkitekturteknik; Luleå
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259760

Creep is defined as deformation that takes place under constant load after an initial elastic response. This thesis focuses on a material property problem area that concerns stress analysis. Focus is on stress development considering creep deformations occurring when a concrete structure is under load, i.e. stress analysis with viscoelastic properties of the material.From laboratory tests, both elastic modulus and deformations over time are estimated in an evaluation process. Usually, deformations of moist sealed samples are denoted basic creep. At Luleå Technical University creep measurements are evaluated according to the theory and methodology in Larson and Jonasson (2003a, 2003b). The model is denoted Linear Logarithmic Model, used for moist sealed concrete samples. This thesis involves an investigation of the evaluation procedure for basic creep performed in Thysell laboratory at LTU, to examine how sensitive the evaluation process is for the outcome from stress calculations. The calculations are performed in the Finite Element Method software ConTeSt Pro.The aim of the thesis is to analyze the sensitivity of evaluation of basic creep and of the Linear Logarithmic Model (LLM) by making changes in the evaluation process to see how different parameters sets effect calculated stresses/strains during through crack analysis. The changes are solely done in the relaxation spectra.The purpose is also to analyze how sensitive the changes made in the evaluation process are when typical cases are studied. The typical cases are defined with a structure of a newly cast wall on a mature slab, where various thickness of the wall during different temperature conditions are analyzed. The temperature conditions are named standard, winter and summer. With this, concrete is tested and evaluated to yield two material parameter sets useful for temperature - and stress calculations for young concrete.The material parameter sets were analyzed and their creep values were converted into relaxation values, i.e. relaxation spectra, ...