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Dr Nicholas Alexander

Dr Nicholas Alexander

Dr Nicholas Alexander
BSc(Eng) Lond, PhD(UCLond), CMath MIMA, CSci

Senior Lecturer in Structural Engineering

Office 2.33
Queen's Building,
University Walk, Clifton BS8 1TR
(See a map)

+44 (0) 117 331 5732

Summary

Google Scholar Citations,

http://www.researchgate.net/profile/Nicholas_Alexander/?ev=prf_highl

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The current projects that I am working on are

  • Behaviour of nonlinear moment resisting frames under seismic excitation - how do you develop robust low order models for complex nonlinear dynamical systems that are subjected to uncertain loading histories? Are nonlinear response spectra and performance based approaches the way forwards?
  • Pre-stressed frames with opening joints that allow structures to soften but remain undamaged after earthquakes. - can we design structures with morphing geometry that remains undamaged after earthquakes?
  • Nonlinear tuned mass dampers - can we improve on a linear tuned mass damper? What advantages are gained by the nonlinearity? Are smart semi-active devices the way forwards?
  • All analysis in earthquake engineering is predicated on the accurate processing of ground motion timehistories. We use state of the art signal processing ideas such as wavelet decomposition and denoising, Wigner-ville methods, Bispectra, Volterra Kernels, adaptive total least squares etc. - can we determine robust and accurate measure of displacement timehistories from recorded accelerations? (thought to be impossible because of influence of low frequency noise)
  • Analysis of long structures that are subjected to differential seismic excitation both in acceleration and displacement; i.e. the multi-support excitation of bridges - How should be analyse these structures to take into account all the true complexity of spatial-temporal variation in ground motion?
  • Human-Structure interaction - dynamic feedback between structures and people that can produce complex and unexpected resonances - can we model human beings responses to moving structures and hence the feedback into structures?
  • Understanding the dynamics of piled structures, using a nonlinear dynamics perspective - can we model these systems to understand both short terms and long term behaviour?
  • Vulnerability of cities; structure-soil-structure interaction - do buildings near to one another interact dynamically? Does the assessment of vulnerability of such systems require a detail knowledge of such dynamic, nonlinear interactions?
 

Biography

My main areas of interest are Earthquake Engineering, Structural Dynamics and Nonlinear dynamics. I did my undergraduate and post-graduate studies at University College London (UCL). I graduated with a 1st Class Honours degree in Civil Engineering and was awarded the Institution of Civil Engineers prize

My Ph.D. was in the field of nonlinear dynamics; were I worked on bifurcation following, computational algorithms for the investigation of nonlinear systems. The main part of this thesis was the development of algorithms for identifying and continuing invariant manifold tangencies.

After leaving UCL I worked for a Structural Engineering design consultancy before returning to academia; taking up a post at the University of East London (UEL). While at UEL I became interested in the whole area of the application of structural dynamics to the field of Earthquake Engineering. I supervised two Ph.Ds (completed) there; one in the behaviour of buildings that are subject to torsion and lateral swaying, and another in the field of nonlinear reinforced concrete frameworks with extensive experimental testing of such frames in the Laboratories at UEL. After a number of years in this field I was asked to give course of lectures in Dynamics and Earthquake Engineering at UCL on their MSc as an external lecturer. In 2003 I came to Bristol and took up a post here.

I have supervised one Ph.D (completed) here at Bristol and I am currently supervising four Ph.D. students. I have published over 50 international conference and Journal papers.

I am a member of the institute of mathematics and its applications, a Chartered Mathematician and a Chartered Scientist (Uk). I am a graduate member of the Institution of Civil Engineers.

I have reviewed papers for Journal of Sound and Vibration, ICE Buildings and Structures, Engineering Computations, Civil Engineering and Environmental Systems, Shock and Vibration, Journal of Zhejiang University Science A, Computers and Structures, Engineering Structures and Physica D

At Bristol I have developed been interested in the following areas (i) applications of nonlinear dynamics in the field of earthquake engineering (ii) development of algorithms in the accurate processing of ground motion data in order to determine robust measures of ground motion displacements  (iii) human-structure dynamic interaction problems, (iv) nonlinear soil-structure and structure-soil-structure interaction problems.

Keywords

  • Pre-stressed frames
  • non-linear moment resisting frames
  • mass dampers
  • signal processing
  • differential seismic excitation

Memberships

Organisations

Department of Civil Engineering

Other sites

Research Groups

Selected publications

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View complete publications list in the University of Bristol publications system

Courses

Dr Alexander currently teaches 2 courses:

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