Linear Logarithmic Model for Concrete Creep
| Autor: | Mårten Larson, Jan-Erik Jonasson |
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| Rok vydání: | 2003 |
| Předmět: | |
| Zdroj: | Journal of Advanced Concrete Technology. 1:172-187 |
| ISSN: | 1347-3913 1346-8014 |
| Popis: | Control of thermal cracking in young concrete is of great importance to ensure a desired service lifetime and function of a structure. Young concrete is here defined as the period up to approximately 100 days after casting. Making reliable predictions about thermal stresses, and thereby cracking risks, the creep behaviour forms an important part of the material modelling. Up until now few studies have been made to investigate how different creep modelling influences calculated thermal stresses. Existing creep models for young concrete are often pure mathematical expressions with no direct relation to the material behaviour and thereby complicated to understand and use in a more practical context. In this paper a new basic creep model primarily aimed for early age purposes is outlined. The formulation with its model parameters, which have an easy to understand meaning in the material behaviour, is based on piece-wise linear curves in logarithm of time and therefore denoted the Linear Logarithmic Model (LLM). Comparison with experimental creep data and other more commonly used creep formulations for young concrete is made to achieve an opinion about the accuracy of the new model. The new model is a flexible and robust formulation that can model the behaviour of both young and mature concrete. The robustness enables it to make reliable creep modelling with very few test data. Another advantage with the LLM formulation is that the appearance of negative relaxation in linear viscoelastic modelling is very small and negligible with respect to thermal stresses. This means that the original formulation may be used directly in a thermal stress analysis for young concrete without any adjustment for negative relaxation. The LLM formulation shows very good agreement directly with experimental creep data and indirectly with measured thermal stresses, whereby the formulation has been used to model the viscoelastic behaviour of the concrete. The formulation also has the best correlation with experimental data compared to other commonly used creep models that have been analysed in this paper. Validerad; 2003; 20080523 (ysko) |
| Databáze: | OpenAIRE |
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