Earthquake and CivilEngineering Dynamics Research

John Macdonald et al.

John Macdonald et al.

Earthquake and CivilEngineering Dynamics Research

• Scope of research• Seismic hazard, soil, structure, elements, interactions, …

• Ill-defined boundaries• Structures, statics, materials, fatigue, seismology, systems,

aerodynamics, biomechanics, …

• Opportunities• Nuclear & renewable energy

• Methods• Experiments – shaking table, element, bespoke rigs, full-scale• Analysis - Non-linear dynamics, FEM, DEM

Research themes

• Seismic risk and loss estimation• Non-linear dynamics• Soil dynamics and soil-structure interaction• Wind and pedestrian-induced vibrations• Composite materials and fatigue• Systems view of performance

Seismic loss estimation(Katsu Goda)

Micro Meso Macro

Seismic Structure-Soil-Structure Interaction (Nick Alexander, Erdin Ibraim, Hisham Aldaikh)

• Understand the critical emergent behaviour of the system• Linear and non-linear domains• Analytical/Numerical/Experimental (shaking table)

Long term objectiveCity seismic vulnerability

Non-linear Dynamics of Masonry Panels(Colin Taylor, Adam Crewe)

• Out-of-plane behaviour• Unreinforced masonry panels

Forcing frequency / rad.s-1

Forc

ing

ampl

itud

e / m

.s-2

Non-linear Cable Dynamics(John Macdonald, Matt Dietz, Simon Neild, David Wagg, Adam Crewe)

Excitation frequency

Responseamplitude

Input amplitude

Responseamplitude

Stability boundaries

Non-linear Tuned Mass Dampers(Nick Alexander, Colin Taylor)

0 5 10 15-5

0

5

a) Primary structure without coupling

accele

ratio

n (in

g)

0 5 10 15-5

0

5b) Primary structure with coupling

accele

ratio

n (in

g)

0 5 10 15-6

-4

-2

0

2

4

6c) Attached structure with coupling

t (s)

accele

ratio

n (in

g)

)(2 gx

)(1 gx

)(1 gx

t(s)

Friuly earthquake

)(txg

Cubic nonlinear stiffness

Non-linear Dynamics of Damage-Resilient Buildings (Ollie Oddbjornsson, Nick Alexander, Colin Taylor, Adam Crewe)

Quarter Scale Physical Model

Stiffness and response frequency characteristics

Beam-Column Joint

Nonlinear resonance response curve of the physical model

Theoretical response

UK NEES – Distributed Testing(Matt Dietz, Adam Crewe)

• Synchronous distributed testing of self centring frame with shear dampers

Soil-structure interaction of soil foundations for offshore wind turbines(Daniella Escribano, James Cox, David Nash, Suby Bhattacharya, Andrea Diambra, Domenico Lombardi, Sam Hayhurst)

changing soil stiffness may result in cumulative long term deformations and altered dynamic response

long term cyclic loading due to wind and waves

subject soil elements to simplified cyclic stress history in laboratory and observe changes of dynamic stiffness and deformation

Soil sample subjected to cyclic deviatoric stress changes.Instrumentation includes boundary stresses, local strain measurement, pore pressure and bender elements.

time

thousands of cycles

Soil element testing in the Geomechanics laboratory

Physical testing of soil-structure interaction

Clay (Different forcing amplitudes)

Sand (Different sand densities)

Changes in measured natural frequencies

Dynamic behaviour of soils reinforced with long inclusions (piles)

(Erdin Ibraim, Colin Taylor, Matt Dietz, Luiza Dihoru)

• Modelling: homogenisation (ENTPE Lyon)• Testing: analogue material reinforced with periodic inclusions

Cubical Cell Apparatus (CCA)

Micro-scale DEM at Imperial College

Macro-scale

CCA at University of Bristol

Dynamic measurements: Bender/Extender elements

Static stress probing:

High resolution non-contact sensors (in progress)

Micromechanics of seismic wave propagation in granular materials

(Erdin Ibraim, Martin Lings, Ignacio Cavaretta, Simon Hamlin)

v

h belt

h 90

Vs(hv)

Vs(hh)

Vs(vh)b Vs(vh)

Wave propagation measurements

Wind-induced vibrations of slender structures - cable galloping(John Macdonald, Nick Nikitas, Joe Symes)

Passive dynamic cable model in 3m x 6m wind tunnel in Canada

Forced dynamic cable model in wind tunnel in Bristol

• Amplitude limited by aerodynamic non-linearity

10 11 12 13 14 15 1660

65

70

75

80

85

90

Win

d d

irect

ion

( )

Wind speed (m/s)

1 1

23

4

5

Vibration amplitude (m)from galloping analysis

(c.f. site observations 5.4m)

Pedestrian-structure interaction(John Macdonald, Jeremy Burn, Mateusz Bocian)

xx

L

mg

y

u

θ

H

L

mg

y

u

θ

H

xm xm

Pedestrian model

Motion of bridge and pedestrians

Bridge responses from simulations

180pedestrians

270pedestrians

400pedestrians

• Unique 100T test frame• 8m span, 3.7m wide bridge• Cellular orthotropic decking• 60 million cycles of loading from

tyres of heavy lorries• Understand response local

to simulated tyre loads• Supported by Highways Agency,

Institution of Civil Engineers, Mouchel.

Fatigue of composite bridge decks(Wendel Sebastian, Joel Ross)

Summary - Research themes

• Seismic risk and loss estimation• Non-linear dynamics• Soil dynamics and soil-structure interaction• Wind and pedestrian-induced vibrations• Composite materials and fatigue• Systems view of performance