Warwick Research into Humans
and Structures
Contents
1.
2.
3.
4.
Humans and Structures Laboratory
Experimental facilities: structures
Experimental facilities: humans
Experimental facilities: human-structure
interaction
5. Current projects
6. Summary
Dr Stana Zivanovic (structural engineering)
Dr Neil Evans (biomechanics & biomedicine)
School of Engineering
University of Warwick
United Kingdom
Contents
1.
2.
3.
4.
Humans and Structures Laboratory
Experimental facilities: structures
Experimental facilities: humans
Experimental facilities: human-structure
interaction
5. Current projects
6. Summary
1
1
Humans & Structures Lab
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Remit is in experimental and numerical work on:
• Dynamic properties of civil structures
• Dynamic loading by humans
• Human-structure interaction (kinematics, kinetics,
vibration perception, synchronisation)
Established in 2010
Acquired experimental facilities in excess of £130k
+ Gait Lab
1
Humans & Structures Lab remit
Structures of interest:
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Humans & Structures Lab remit
Examples of excessive vibrations:
Millennium Bridge, London, UK
(max observed crowd ~2,000)
Contents
1.
2.
3.
4.
Humans and Structures Laboratory
Experimental facilities: structures
Experimental facilities: humans
Experimental facilities: human-structure
interaction
5. Current projects
6. Summary
4
Nürnberg stadium, Germany
(capacity ~50,000)
Lab Facilities: structures
5
Modal testing equipment
Dytran 5803A
sledge hammer
Quattro
APS 400
QA750
electrodynamic
shaker
24-bit, 4 inputs
1300mV/g
accelerometers 1 output
Dytran 3166B1
500mV/g accelerometers
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Contents
1.
2.
3.
4.
Humans and Structures Laboratory
Experimental facilities: structures
Experimental facilities: humans
Experimental facilities: human-structure
interaction
5. Current projects
6. Summary
Lab Facilities: humans
6
Human loading characterisation
AMTI BP400600
force plate
Gait Lab
Vicon motion
capture system
F-scan VersaTek
in-shoe pressure
Treadmill (not instrumented)
Contents
1.
2.
3.
4.
Humans and Structures Laboratory
Experimental facilities: structures
Experimental facilities: humans
Experimental facilities: human-structure
interaction
5. Current projects
6. Summary
Lab Facilities: human-structure
interaction
7
Warwick Bridge, lively under pedestrian excitation
3
Why a lively laboratory bridge?
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2
Modal acceleration [m/s ]
Current vibration guidelines are not readily applicable on slender
structures
Design
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Design brief:
2.5
predicted
2.0
1.5
1.0 measured
0.5
0.0
-0.5
-1.0
-1.5
-2.0
DLF=0.17
-2.5
0 10 20 30 40 50 60 70 80 90
Time [s]
•
•
•
•
•
•
Lively (vertical direction) under walking excitation
Natural frequency 1.5-2.5Hz
Maximum length 21m
Tunable natural frequency and damping ratio
Obey H&S requirements (construction in the Lab)
(Low damping ratio preferred)
Response overestimate due to pedestrian-structure interaction?
What level of vibration disturbs human gait?
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Design
Simple beam structure:
Design
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Cross section:
• Low natural frequency means: - long span and/or
- large mass and/or
- low stiffness
• Span length most influential factor
2
 1 
fn1    2
 2  L
EI
m
m, EI
L
• Long span => high slenderness (span to depth ratio)
• Ensure structural integrity
• Decision: composite steel-concrete structure
• Reinforced concrete C40/50, 2x mesh 8@200mm
• Fibermesh FM650s (polypropylene fibres)
• 2xUC203x203x52, S355
• 83 studs per beam, 19mm
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Design
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Design
Plan view:
Elevation view:
• Cross beams to form steel frames
• Delivered in three pieces (length restriction in the Lab)
• Butt-welded in the Lab
• Camber 250mm (to flatten under creep and shrinkage)
Construction
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Construction
Steelwork:
Concrete deck:
• Three frames: 5.82m + 8.26m + 5.82m
• Placed on six props
• Full penetration butt welds, ultrasound check
• Formwork construction (supports on steel beams and floor)
• Ready mix concrete (6m3)
• Casting on 14 Jan 2012 (a very cold day!)
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15
5
Construction
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Removing props (bridge lifting):
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Static behaviour
Concrete properties:
• Formwork removed at 46 days
• Curing stopped after 60 days
• Placement on two supports after 60 days
• Achieved concrete class at least C50/60 (designed
C40/50)
• Average density: 2.4 t/m3
Modal testing: setup
3
4
5
6
60
61
62
63
7
8
9
10
11
12
13
64
65
66
67
68
69
70
71
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15
16
17
18
19
20
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11.95m
9.95m
10.95m
7.95m
7x1.0=7.0m
8.95m
5.95m
6.95m
7x1.0=7.0m
3.95m
1.85m
0.00m
0.05m
0.95m
1.1m
59
1.1m
0.9m 0.9m
0.05m
19.85m
19.90m
2
58
18.95m
1
57
18.05m
56
15.95m
55
16.95m
54
13.95m
53
14.95m
52
12.95m
51
0.05m 0.9m 0.9m
• Shrinkage estimate (Eurocode) is reasonable
• Measured/calculated deflection ratio = 1.11 (likely due to
uncertainties related to creep and shrinkage effects)
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Dynamic behaviour
4.95m
Shrinkage and deflection:
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2.95m
Static behaviour
• Shaker at TP7
• Random excitation up to 25Hz
• QA-750 accelerometers
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Dynamic behaviour
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Modal testing: identified vibration modes
Dynamic behaviour
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Walking tests
• Uncontrolled pacing rate
• V1: 2.5Hz, 0.5%
• Natural frequency can be reduced by increasing the
span length
Dynamic behaviour
Walking tests
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Dynamic behaviour
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V1: amplitude dependent behaviour
• Pacing rate matching resonance
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Contents
Measuring dynamic force
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Study walking locomotion on lively bridge
1.
2.
3.
4.
Humans and Structures Laboratory
Experimental facilities: structures
Experimental facilities: humans
Experimental facilities: human-structure
interaction
5. Current projects
6. Summary
• Using VICON motion capture system
Infra-red camera
S – total number of body segments
mi – mass of i-th body segment
ai – acceleration of i-th segment
g – gravity
S
Drillis et al. (1964)
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Trajectories of segment centers
1.6
Body centre of mass
Head
Left upper arm
Left lower arm
Trunk
Left thigh
Left shank
Left foot
1.4
1.2
CoM
1.0
Test subject instrumented by reflective
markers
FVGRF   mi (ai  g)
i 1
Measuring human kinematics
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Experiments on rigid surface
0.8
0.6
0.4
0.2
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Peak-to-peak CoM displacement: ~6cm
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Walking on lively bridge
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Dynamic force amplitude
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First harmonic only, 3 test subjects
Experiments on lively surface
Parameters
monitored:
-Step frequency
-Step length
-Step width
-Leg orientations
-Trunk rotation
-Force
• Experiments involving multi-person traffic
Pedestrian perception of vibration
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• Vibration limit = f(pacing rate)
• Not pedestrian data
• Unique data for 3 test subjects
• Interaction trigger
Summary
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• A lively composite steel-concrete bridge was
successfully built in the lab
• Unique experimental facilities developed
• Experimental testing on rigid surface and lively
bridge performed
• Statistical description of monitored parameters is
in progress
• Data to be used for calibrating pedestrian models
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Acknowledgements
•
•
• Hiep Vu Dang (PhD student at Warwick)
• Colin Caprani and his team for hosting us
THANK YOU
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