Wind and structures and motion… Is there something we miss on how the three connect? London

16 May, 2017 | 18:00 - 20:00

Wind and structures and motion… Is there something we miss on how the three connect? London

About this event

Starting from the engineering benchmark failure of fluttering bridges (see the infamous Tacoma Narrow Bridge collapse), this presentation will attempt to give a holistic overview of large wind-induced vibrations and engineering explanations that seem to not fully work in our design practices. Based on full-scale tests, within a laboratory setting or outside in the "real wind", a number of critical observations are highlighted.

Particular focus is given on aerodynamic self-excited forces or else the interaction part of the loading that is not fully understood and at times, and not only in aerodynamics, it is emerging beyond expectation to source the large structural vibrations all engineers want to avoid.

An ideal exemplar are the dry-galloping vibrations of inclined stay cables, a real controversial phenomenon that although concerted international efforts still hides its mechanistic insights. Namely, recent findings indicate that the quasi-steady aerodynamic theory does not fully capture the details of this unstable condition, and neither does the axial flow propagating on the lee side of inclined cables, and nor does the critical Reynolds number range transition.

So what is the way forward? Some answers and even more questions are what this presentation sets to put forward.

Event materials

The following materials are available for download:

Speaker

Nikolaos Nikitas

Nikolaos is a Lecturer (B) in Structural Dynamics in the School of Civil Engineering of the University of Leeds and an ex-Lecturer of the University of Bristol working particularly on complex, multibody dynamic interaction problems spanning from wind to earthquake to human loading and bridging scales from the nano of material dislocations (i.e. avalanche-like deformation) to the macro of large infrastructural assets (i.e. structural monitoring in full-scale).

Having studied for a PhD on theoretical mechanics at the University of Edinburgh and a second one on bridge aeroelasticity at the University of Bristol, he became a specialist on experimental dynamics and identification analysis for a wide range of applications. More recently, he led and managed the proposal for the EPSRC Strategic Equipment Grant that funded the Leeds Multi-Axis Shaking Table facility (see EP/L022648/1; goo.gl/6WUOd6).

His multidisciplinary and multiscale work includes among others full-scale monitoring and inverse analysis of landmark/major bridges (the Clifton Suspension Bridge, UK; the Ting Kau Bridge, HK), wind tunnel testing in state-of-the-art unique facilities (National Research Council, CN), shaking table tests and physical modelling for novel structural systems (e.g. offshore wind turbines, dynamic facades).

He is the structural dynamics expert in the recent Newton-Picarte Award (EP/N03435X/1; goo.gl/Qf3YAJ) that attempts to apply aerodynamic concepts in soil-structure interaction and link UK and Chile through a unique impact case study. Finally, he is an Associate Editor for the "Wind Engineering" section of "frontiers in Built Environment", member of the editorial board in "Resilient and Sustainable Infrastructure" and in "Advances in Mechanical Engineering" and serves EPSRC as a dynamics-expert reviewer through his participation in the Associate Peer Review College.

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