The stability of arches is a classical mechanics and pragmatic engineering problem
that has been extensively studied by many researchers over the years. Despite the
comprehensive construction and research of arches throughout history, their complex
behaviour still presents a challenge to engineers and ensures they are the subject of
continual investigation. The problem of arch stability is of contemporary relevance
due to the surging popularity of concrete-filled steel tubular (CFST) arch bridges.
Hence, due to the inherent complex structural function of arches when coupled with
the increasing construction of CFST arches, research into the response and stability
of CFST arches under all possible environmental conditions is necessitated. However,
investigations into the effects of extreme temperatures on concrete and CFST arches
have not been conducted.
This thesis presents a comprehensive analytical and numerical investigation into the
stability of circular concrete and CFST arches subjected to combined mechanical and
thermal loading. Original models are derived for the non-linear prebuckling and buckling analysis including closed-form solutions for the in-plane elastic buckling loads of
concrete and CFST arches, and non-discretisation mechanically-based numerical models for their elastic and inelastic analysis prebuckling analysis. Additionally, a numerical
methodology to determine the elastic flexural-torsional buckling loads of CFST arches
is proposed. Furthermore, a novel fractional viscoelastic creep law is developed for
concrete at elevated temperatures in order to analyse the significance of basic creep
strain on thermal response and stability boundaries. The fractional-derivative creep
law proves to be a robust and compact method of modelling basic creep strain under
stress and temperature varying conditions. Finite difference schemes are employed to
numerically approximate the fractional derivative and incorporate basic creep into the prebuckling and stability analyses. Finite Element (FE) models are developed to verify the derived models and to also investigate the inelastic buckling strength and fire
performance of concrete and CFST arches.
The findings of this study provide a detailed understanding of the fundamental thermomechanical behaviour and failure modes of concrete and CFST arches. Consequently,
engineers may utilise the results detailed herein to assess and improve the fire resistance of concrete and CFST arch structures. Additionally, the developed creep law
has widespread application in the analysis of concrete structures under elevated temperatures. The proposed inelastic numerical models also provide efficient tools for the
analysis of other structures such as steel arches and beams.