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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