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Abstract
The long-term structural behaviour and buckling of a concrete-filled steel tubular (CFST) arch under sustained loading are very much related to creep and shrinkage of its concrete core. The creep and shrinkage of the concrete core will produce time-dependent structural deformations and change equilibrium configuration of the CFST arch under sustained loading, which may even lead to the long-term failure of the arch. A CFST arch that is stable in the short term may buckle under sustained loading in the long term and fail in a limit point instability mode or a bifurcation instability mode. Hence, it is vital and essential to understand the long-term behaviour and stability of CFST arches by accounting for time-variant viscoelastic features and different working conditions and develop an applicable strategy of estimating the long-term structural behaviour and buckling for ensuring the safety and serviceability of CFST arches.
This dissertation aims to develop linear and nonlinear analytical frameworks for predicting the long-term structural behaviour and buckling of CFST arches under various circumstances. Virtual work methods are used to establish the differential equations of equilibrium and the age-adjusted effective modulus method is employed to address the creep issue of the concrete core. Different types of boundary conditions and loading cases are systematically addressed in this dissertation. Closed-form solutions for the linear and nonlinear long-term behaviour and buckling of CFST arches under various circumstances have been obtained. It is found that geometric nonlinearity plays a significant role in correctly predicting the long-term structural behaviour and stability of CFST arches.
A finite element model is also developed for the long-term analysis of CFST arches and can be used to validate the analytical solutions and to perform the long-term analysis of CFST arches with general load and boundary conditions. By comparing with finite element analysis, the analytical models and solutions are validated to be reliable and capable of predicting the long-term structural behaviour and assessing the long-term stability of CFST arches. Long-term structural analysis and stability assessment conducted in this dissertation could provide useful references and benchmarks for structural designers and researchers in the area of CFST arches.