Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Model for calculation of creep and shrinkage of fiber reinforced concrete
Fiber reinforced concretes (FRC) can be used for the design of load carrying structures as simple FRCs, as FRCs with classical concrete reinforcement and as prestressed FRCs. The basic condition is that the properties of FRCs bring to the structure economic advantages. As a rule among the properties that positively contribute to the effectivity of the designed structure are higher cracking tensile strength, ability of elements to carry loads also after the formation of cracks (FRC ductility) and mainly the increased resistance to the repeated load. But application of fiber reinforced concrete (FRC) to real structures, structural elements and members (not only floors) brings many specific problems to designers. The latest prediction models (that means B3, EC2 ...) determine only volume changes of plain concrete. It is possible to expect that the models for determining creep and shrinkage of plain concrete should be supplemented with the influence of another component of composite, that means, fibers. Probably, necessary time to design such a model will take more time considering that above mentioned models were reached during many years of research work. A prediction model of volume changes of FRC based on a hypothesis in which creep proceeded linearly in dependence on ratio of compression strength of FRC to compression strength of plain concrete with the same composition (shrinkage is based on the dependence of tensile strength ratio of FRC) is presented. This hypothesis is based on results of volume changes measurements of FRC (especially specimens with steel fibers), measured since 1988 (main results since 1995). The results were measured in co-operation of Warsaw University of Technology (PW), Klokner Institute (KU) and Faculty of Civil Engineering CTU in Prague. The results of all illustrated examples show that the declared hypothesis which consists in a simple idea, can be accepted by designers. The presented model, although it has a simple expression, could be compiled only on the basis of large database of results of volume change measurements that require long time and significant costs. It offers a possibility to determine the magnitude of volume changes for structure made of FRC. It is obvious that the practical use will force further improvements of accuracy of the calculation models and that time will bring new models.
Model for calculation of creep and shrinkage of fiber reinforced concrete
Fiber reinforced concretes (FRC) can be used for the design of load carrying structures as simple FRCs, as FRCs with classical concrete reinforcement and as prestressed FRCs. The basic condition is that the properties of FRCs bring to the structure economic advantages. As a rule among the properties that positively contribute to the effectivity of the designed structure are higher cracking tensile strength, ability of elements to carry loads also after the formation of cracks (FRC ductility) and mainly the increased resistance to the repeated load. But application of fiber reinforced concrete (FRC) to real structures, structural elements and members (not only floors) brings many specific problems to designers. The latest prediction models (that means B3, EC2 ...) determine only volume changes of plain concrete. It is possible to expect that the models for determining creep and shrinkage of plain concrete should be supplemented with the influence of another component of composite, that means, fibers. Probably, necessary time to design such a model will take more time considering that above mentioned models were reached during many years of research work. A prediction model of volume changes of FRC based on a hypothesis in which creep proceeded linearly in dependence on ratio of compression strength of FRC to compression strength of plain concrete with the same composition (shrinkage is based on the dependence of tensile strength ratio of FRC) is presented. This hypothesis is based on results of volume changes measurements of FRC (especially specimens with steel fibers), measured since 1988 (main results since 1995). The results were measured in co-operation of Warsaw University of Technology (PW), Klokner Institute (KU) and Faculty of Civil Engineering CTU in Prague. The results of all illustrated examples show that the declared hypothesis which consists in a simple idea, can be accepted by designers. The presented model, although it has a simple expression, could be compiled only on the basis of large database of results of volume change measurements that require long time and significant costs. It offers a possibility to determine the magnitude of volume changes for structure made of FRC. It is obvious that the practical use will force further improvements of accuracy of the calculation models and that time will bring new models.
Model for calculation of creep and shrinkage of fiber reinforced concrete
Spura, Dusan (Autor:in) / Vodicka, Jan (Autor:in) / Kratky, Jiri (Autor:in)
2004
8 Seiten, 3 Bilder, 2 Tabellen, 6 Quellen
Aufsatz (Konferenz)
Englisch
Model for calculation of creep and shrinkage of fiber reinforced concrete
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