Structural elliptical hollow sections represent a recent addition to the range of cross-sections available to structural engineers. However, despite widespread interest in their application on the basis of both architectural appeal and structural efficiency, a lack of verified design guidance is inhibiting uptake. The proposed project aims to overcome this through the generation of statistically validated design rules, developed on the basis of a sound theoretical understanding, carefully conducted laboratory tests and sophisticated numerical modelling. Laboratory testing will be the key instrument for the generation of the fundamental data required, and once calibrated, numerical modelling will be used to investigate the importance of the individual parameters and to extend the range of available data. Design rules will be developed with structural engineers in mind, with careful consideration given to finding the right balance between accuracy of result and ease of calculation method. All new design guidance will be developed in line with the Eurocode framework, with the aim that the work may be considered for incorporation into future revisions of the Code. Dissemination of the findings to the academic community will be made through journal publications and by presentation at International conferences.This is a joint application between Imperial College London and the University of Leeds, making use of the combined experience and facilities of the applicants - Dr Gardner from Imperial College with expertise of the instability of tubular steel and stainless steel elements, and Dr Lam from the University of Leeds with expertise of connections and concrete filled composite tubes.

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The main motivator for the proposed research is performance improvement of energy capture or hydrodynamic efficiency of propulsion systems. In particular, the application requirements of passively adaptive underwater tidal turbine blades and marine propellers. However, the investigators believe that application of passively adaptive composites structures could extend to include passively adaptive race car aerodynamics, aircraft control surfaces, surface ship and underwater vehicle control surfaces, and wind turbines. In order to achieve this goal it is proposed to employ composite materials with their inherent ability to create a coupled response to in-service loads. Design of such a structure which is tuned to a dynamic load environment will result in improved efficiency of the two main applications of this research, energy capture devices and marine propulsors.The aim of the proposed research is to challenge the existing design philosophy from one whereby a tailored passively adaptive composites is designed to mimic a conventional isotropic structure into a paradigm that allows the ability to tune a geometry and it's internal architecture to deform in a known and controlled manner as the load regime changes. Such an approach requires fundamental research into the modelling of interwoven, 3D fibre structures and novel approaches to design of the internal architecture that can identify fibre stacking/weaving strategies that give tuned deformations across multiple loading/operational conditions. To develop this paradigm shift in structural performance we will explore how lifting surfaces, be they control surfaces, propulsors or turbines are designed using such smart materials. The main focus will be the maritime sector where there has been a much slower take-up in such technology but where the potential benefits are large (see impact plan). To the authors knowledge this has not been conducted anywhere before and is therefore a challenging and exciting programme.