| Summary: | <p>This thesis is centred around the development of a family of computationally efficient design methods called ‘oxCaisson’, that can predict the behaviour of suction caisson foundations under six degrees-of-freedom loading. These design methods were developed for applications where timeliness or speed is a crucial factor; hence the term ‘time-critical design methods’.</p>
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<p>oxCaisson is based on the Winkler framework, in which the soil response is represented by Winkler-type soil reactions that are either distributed along the caisson skirt length or concentrated at the caisson base. These soil reactions were calibrated against the results of rigorous, three-dimensional finite element (3DFE) analyses, making ox- Caisson effectively a surrogate model for the 3DFE method.</p>
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<p>The design methods developed are hierarchical in nature, where each subsequent design method builds upon previous ones. First, a design method called ‘oxCaisson-LE’ was developed for a ‘toy problem’, in which the soil was idealised as a homogeneous, linear elastic material. Then, the assumption of soil stiffness homogeneity is relaxed as an energy-based design method was developed for non-homogeneous stiffness profiles. Following that, the assumption of a fully rigid caisson is relaxed as the caisson skirt is modelled using deformable frame elements, which allows the prediction of flexible caisson behaviour (i.e. caissons with deformable skirts).</p>
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<p>Next, a design method called ‘oxCaisson-NLE’ was developed to predict the caisson behaviour in small-strain, non-linear elastic soil. Then, a new elasto-plastic design method called ‘oxCaisson-LEPP’ was developed to predict the caisson behaviour in linear elastic, perfectly plastic soil. oxCaisson-LEPP combines the previously developed linear elastic soil reactions with plastic yield surfaces. To model cohesive soil, the plastic yield surfaces were calibrated against 3DFE analyses using linear elastic, perfectly plastic soil with a von Mises yield criterion.</p>
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<p>Altogether, these design methods allow a rapid turnover of ‘3DFE-approximate’ design evaluations, which is crucial for time-critical applications such as large scale foundation design optimisation.</p>
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