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Title: Study of the time-dependent behaviour and its prediction in concrete and concrete structures
Author: Howells, Richard
ISNI:       0000 0004 2750 4233
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2004
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The main objective of this study was to bring together two areas of research the first being a laboratory study of the time-dependant properties of concrete while the second is a study of the time-dependant behaviour of two prestressed concrete structures - the Grangetown and Cogan Viaducts. A study of the influence of shrinkage and creep on a range of normal to high strength concretes in the laboratory found that as concrete strength increased, drying and total shrinkage also increased while the rate at which creep developed decreased. It was shown that autogenous shrinkage is more prevalent in high strength concrete, and the inclusion of pfa in concrete reduces the amount of total shrinkage. The benefits and limitations of using current shrinkage and creep prediction models were determined through a sensitivity study of their input parameters and through comparisons with shrinkage and creep strains determined in the laboratory. It was found that certain models are more sensitive to specific parameters than others. All models predicted strains which gave good to adequate agreement with the measured strains when the material parameters were within the ranges specified by the models, but the prediction was less reliable when the parameters used in the models exceeded the recommended values. It was shown that the prediction of the time-dependant behaviour of the Grangetown and Cogan Viaducts using these models is inadequate due to influences not considered by the models such as prestressing forces and the construction sequence. The influence of the construction sequence and prestressing data was investigated using a complex computer code in conjunction with these models, and while it was not possible to improve the efficiency of predicting reliable strain behaviour over time, an appreciation of the level of detail necessary to do this was gained. Finally, the influence of environmental conditions on the strain behaviour of these two structures was shown to be greater than anticipated.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available