Browsing by Author "Hoppe, Gert Erhard"

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    Creep, shrinkage and elastic strains in a prestressed concrete bridge : theoretical and actual
    (1981) Hoppe, Gert Erhard
    The object of this thesis is "To investigate the actual creep, shrinkage and elastic strains in a prestressed concrete bridge and to compare these with the results of creep and shrinkage tests carried out in the laboratory in accordance with ASTM C512 Specification on concrete cylinders made using the same aggregates and mix proportions as used for the prestressed concrete bridge and also with the theoretical values calculated using the CEB-FIP recommendations." A literature survey has been carried out to determine the present state of knowledge on the creep, shrinkage and elastic shortening of concrete structures and how this knowledge is used in design. Measurements of actual creep, shrinkage and elastic strain in concrete of the Brakwater South bridge near Windhoek have been recorded since its construction in 1978. At the same time in the laboratory concrete test cylinders and cubes were prepared using the same aggregates and mix proportions as used for the construction of the bridge. Some of the specimens were cured and tested in accordance with BS 1881 to determine the strength of the concrete and the Modulus of Elasticity. Other specimens were cured and stored at controlled temperature and humidity conditions in accordance with ASTM C512-76 to determine the creep and shrinkage characteristics of the concrete under controlled laboratory conditions. Using the latest CEB-FIP and BS 5400 design codes the theoretical design values of creep, shrinkage and elastic shortening are calculated, based on actual temperature, humidity conditions prevailing at the site since the construction of the bridge. The values of creep, shrinkage and elastic shortening actually measured on site are compared with the theoretical design values based on small scale laboratory tests and tentative design recommendations applicable to local conditions are produced.