| Summary: | Structures are highly vulnerable to extreme hydrodynamic events such as tsunamis and floods. Besides water flow forces, waterborne debris impacts can also cause extensive structural damage. In this context, ASCE/SEI 7 prescribes mandatory debris impact design in flood- and tsunami-prone areas. Debris impacts generate high-magnitude impulsive forces. Therefore, low-tensile strength materials like masonry are particularly vulnerable to them, as documented in various post-disaster surveys. However research on masonry structures under waterborne debris impacts is limited. Critical knowledge gaps exist in the understanding of masonry structural behaviour in these scenarios and the development of advanced analysis methodologies. These gaps have significant practical implications given that masonry is among the most common building materials in the UK and worldwide, coupled with the recently updated tsunami risk worldwide and the increasing flood risks in climate change scenarios.
This thesis aims to achieve improved knowledge into the structural behaviour of masonry structures under waterborne debris impacts and to propose new methodologies to assess the structural performance of masonry structures in such scenarios. This work revises common assumptions in related numerical modelling and impact force calculations, i.e. the neglection of high strain rate effects in masonry material models, structural mass and structural nonlinearities. Using newly proposed high-fidelity numerical methods, this study demonstrated the limitations of all of them. Maximum strain rates exceed the critical thresholds to activate high strain rate effects in a broad range of impact scenarios. The structural mass proportionally increases the impact force for structure-to-debris mass and stiffness ratios higher and lower than critical values. Finally, the structural nonlinear behaviour of masonry structures decreases the impact force proportionally to the occurring damage. Using the data collected on the effects of the structural mass and structural nonlinearities, analytical models are proposed, for the first time, to integrate their effects in calculating the impact force-time (F-t) time diagrams of waterborne debris impacts on masonry walls. The research outputs provide new knowledge and numerical methods to assess the structural safety of masonry structures under waterborne debris impacts. Limitations remain in the absence of the fluid phase in the modelling environments and the missing coupled effects of debris and structural nonlinearities. These are critical research areas for future developments. Advanced investigations of local failure modes under debris actions are also future potential developments to identify critical impact locations at the micro-scale.
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