21882940770231984

Numerical representation of lining the tunnels with concrete ejected using sandwich elements

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Numerical representation of lining the tunnels with concrete ejected using sandwich elements

Abstract:
The finite element method has provided a powerful tool to nonlinear numerical analysis of engineering structures. However, the inadequacy of the mathematical constitutive material law turns out to be a big problem in concrete structural analysis. Although a significant progress on the constitutive modelling of concrete and shotcrete behaviour has been made, very little from these models deal with the effect of the high temperature on concrete or shotcrete. Consequently, no unified treatment of the existing models has been attempted, from which a comprehensive three-dimensional constitutive relation can be formulated. Therefore, the objective of this research work is to develop a relatively comprehensive and sophisticated model to describe concrete as well as shotcrete deformational and strength behaviour under normal and high temperatures. The proposed model is an elastic-plastic-hardening constitutive model based on the plasticity theory. In this model, the strain-hardening behaviour as well as the temperature effects modelled and formulated by stress-space plasticity taking into account the heat and the kinematic energies. The model adopted the most sophisticated Willam-Warnke five-parameter model as failure criterion. The present work deals with concrete or shotcrete shell structures and adopted the Isoparametric Sandwich Shell Element in finite element formulations. The main features of the model include the yield surface with closed shape and a non-uniform work-hardening with mixed hardening rule. By the proposed model, an application on a tunnel for the case of fire loading was made. This helps to answer many questions about the safety of the tunnels in case of fires. The results showed that, taking fire loading into consideration has a great importance for designing concrete tunnel lining. This is because very high temperatures cause a total failure in some parts of the tunnel lining.
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