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Bridge-related research at the University of Bristol
John H.G. Macdonald Outline of presentation
• BLADE
• Performance based engineering
• Site monitoring
• Dynamics of long-span bridges
• Other bridge-related research at Bristol
• Future direction of research
Bristol Laboratories forAdvanced Dynamics Engineering (BLADE)
• Due for completion Spring 2004
• £15m grant from Joint Infrastructure Fund
• Integration across Engineering Faculty
BLADE Facilities (1)
• Earthquake and Large Structures Laboratory– Earthquake shaking table– Strong floor– 5m and 15m high strong walls
BLADE Facilities (2)
• Dynamics Laboratory
• Advanced Control and Testing Laboratory
• Environmental Laboratory– Soil mechanics, Composites, High temperature metals
• Heavy Test and Concrete Laboratory
• Light Structures Laboratory– Fatigue, Aircraft structures
• Modelling and Simulation Laboratory
• Workshops and support areas
BLADE Goals
• Develop a viable performance-based engineering framework
• Develop dynamic sub-structuring and other enabling technologies
• Build new knowledge and understanding of systems, non-linear dynamics, materials, control, and risk
• Apply the above to real problems and disseminate
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BLADE strategic framework
Acquire underpinning knowledge
(e.g. dynamics, materials, fatigue)
Develop enabling technologies
(e.g. FE analysis, monitoring systems)
Create and manage system solution(e.g. specific bridge)
Identify stakeholder requirements
(e.g. transport link)Societalinfluences
Underpinningscience
Key Performance Indicatortrajectory and envelope
Time
KPI
Acceptable
Unacceptable
Unacceptable
Measured Now Forecast
Simulated(physical, computation)
KPI
Increasinguncertainty
• Uncertainty => Risk-based decisions
Process models of structure asset management
N.B. Dummy model to demonstrate structure of process model only
Site monitoring of bridges- Second Severn Crossing
Instrumentation on Second Severn Crossing
Supported by EPSRC, Severn River Crossing PLCand the Highways Agency
Benefits of site monitoring (of SSC)
• Performance measurement and design of specific solutions– Cable vibrations– Vortex-induced deck vibrations
• Improved methods of analysis and parameters– Values of damping and wind turbulence– Methods of wind buffeting analysis– Finite Element analysis (static and dynamic)
• Developing tools for long-term management– Model updating– Structural Health Monitoring
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Damping ratios of cable vibrationsin relation to wind velocity
0 1 2 3 4 50
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Equivale nt normal wind s pe e d (m/s )
Dam
ping
ratio
(%)
Me as ure dBe s t fit s traight line
• Theoretical aerodynamic damping matches measured data
• Structural damping determined (intercept)
• No significant effect of corrosion protection wax
Addition of secondary cables
System identification fromambient vibration measurements
0 0.2 0.4 0.6 0.8 1 1.2 1.410
-6
10-5
10-4
10-3
10-2
10-1
Frequency (Hz)
PSD
of a
ccel
erat
ion
((m
/s2 )2 /H
z
measuredfitted
• New method allows for multiple vibration modes, loading spectrum and signal processing distortion
• Modal parameters identified, including damping
• Statistical analysis of accuracy
Comparison of FE and measured mode shapes- first mode of SSC half bridge
South elevation
Plan
West elevation
Lines from FE model, crosses from site measurements
Cables omitted for clarity
• Measured modes used to assess methods of Finite Element modelling (static and dynamic)
• Possible extension to model updating and Structural Health Monitoring
Second Severn Crossing vortex-induced vibrations- full-scale and final model measurements
• Model corrected for full-scale damping, wind turbulence and vibration mode shape
0 5 10 15 20 25 300
50
100
150
200
Wind ve locity (m/s )
RM
S v
ertic
al d
eck
disp
lace
men
t (m
m)
Full s caleMode l
SSC deck cross-section showing baffles added to inhibit vortex-induced vibrations
Longitudinal girders Baffles
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Effect of baffles on vortex-induced response of Second Severn Crossing
0 5 10 15 20 25 300
20
40
60
80
100
120
140
160
180
200
Normal component of the wind (m/s )
RMS vertical displacement (mm)
Second Severn Crossing RMS deck buffeting response near midspan – vertical bending
0 5 10 15 200
5
10
15
Normal compone nt of the wind (m/s )
RM
S d
ispl
acem
ent (
mm
)
Me as ure dDe s ign - me an e xpe cte d re s pons e
Spectra of deck vertical displacement
0.3 0.4 0.5 0.610
-8
10-6
10-4
10-2
Frequency (Hz)
Spe
ctru
m o
f dec
k di
spla
cem
ent (
m2 /H
z)
MeasuredDes ign
Spectra of deck vertical displacement
0.3 0.4 0.5 0.610
-8
10-6
10-4
10-2
Frequency (Hz)
Spe
ctru
m o
f dec
k di
spla
cem
ent (
m2 /H
z)
MeasuredDes ignReca lc. us ing measured da ta
Cable-deck interaction - modelling
Prototype
Scaled FE / mathematical model
Physical scale model
Simplified FE / mathematical model
Dynamic sub-structuring
Physical
Numerical
Interaction
Other bridge-related research at Bristol
• Vulnerability analysis, systems and risk
• Bridge strengthening with Fibre Reinforced Polymers
• Punching shear failure of concrete slabs
• Active load control of bridges
• Fatigue of structural materials
• Local non-intrusive corrosion detection
• Multi-support earthquake excitation of long-span bridges
• Pedestrian-induced vibrations
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Future research directions
• Performance-based engineering• Integrating behaviour of system
components– Technical / societal– Loading / structural performance
(e.g. aerodynamics / non-linear dynamics)– Different structural components
(e.g. cable-deck, soil-structure, concrete-FRP)
• Dynamic sub-structuring• Structural Health Monitoring