Wendy Gough Network Rail David Kendall Optima

Dawlish FRP Footbridge
Wendy Gough
Network Rail
David Kendall
Optima Projects Ltd T +44 (0)7774 887037
[email protected]
Ian Smith
Tony Gee & Partners
[email protected]
Optima Projects
Scope of presentation
Wendy;
• Introduction & Background to project.
Ian;
• Design Criteria & Approval Process.
David;
• Design & Analysis of new bridge.
Questions & Discussion…
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INTRODUCTION
& BACKGROUND
Wendy Gough
Network Rail
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Existing Bridge
• Poor condition
• Seaside location
(south coast)
• Grade II Listed
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Existing Bridge
• Holiday location
• Highly visible
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Existing Bridge
• Prone to storms
& airborne
material
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Existing Bridge
• The original bridge was reconstructed in 1 937 using
serviceable girders from Park Royal Station.
• The station dates from 1 846 rebuilt 1 873.
• Span is 1 7. 5m, width 1 . 78m
• The structure is now in poor condition and under- strength
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Existing Bridge
Like- for- like repairs were
considered as this is a listed
station, but the costs were
approx £600k.
New steel FB considered but
added expense due to listing and
ongoing maintenance required.
FRP was considered to reduce
maintenance costs greatly in a
hostile environment but initially
more expensive than steel
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New FRP Bridge
• Optima Projects Ltd and Tony Gee & Partners have
worked together to produce the design to meet
Network Rail’s criteria and planning requirements.
• This will be installed on site late 201 2 by BAM
Nuttall.
• This is the first FRP footbridge to be installed in
a Network Rail Station and will be a huge
achievement in a listed station.
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DESIGN CRITERIA &
APPROVAL PROCESS
Ian Smith
Tony Gee & Partners
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Approvals Process
High profile, relatively high traffic FRP footbridge
Network Rail
Client
Tony Gee and
Partners
Optima
Projects
Designer
Parsons
Brinckerhoff
Cat 3 Checker
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Loading
• Eurocode footbridge loading
• 5 kN/m2
• 1 0 kN patch load
• No service vehicle (stairs at deck ends)
• Eurocode wind loading
• Parapet loading … no eurocode … TD1 9/06
• 1 400 N/m transversely
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Aerodynamic
• Wind covered by BS EN 1 991 - 1 - 4
• ‘normal’ construction?
• Category b to NA. 2. 49. 3
• Passing trains
• Eurocode loading curve
• Bradkirk footbridge results
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Listed Consent
• Grade II listing – whole station
• Network Rail drove process
• technical input (existing structure) Tony Gee
• Maintain / Repair / Replace
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Maintain
• Under strength – condition beyond maintain
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Repair
• Repair
• replace full length top and bottom flanges
• replace 8 of 20 web panels
• replace 9 of 22 web stiffeners
• all removed rivets replaced with HSFG bolts
• Grandfather’s axe?
• £600 k
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Replace
• Meet modern standards
• Durability in extreme environment
• Replicate the ‘style’ of existing structure
• cross brace
• rivets
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Samples
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DESIGN & ANALYSIS
David Kendall
Optima Projects Ltd
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Concept Studies
Deep Warren Truss
Deep VierendeelTruss
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Final Design
• Mainly Grade E23 pultrusions
full length to minimise joints.
• Bonded & bolted joints.
• Girder web moulded sandwich
panel, epoxy film infusion.
• Stairs cut into deck area
creating structural
complications.
• Stairs are moulded FRP
units.
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Final Design
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Section Through Bridge
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Structural Analysis – FEA model
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Structural Analysis
Live load deflection = 23mm, allowable 1 7400/300 = 58mm
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Structural Analysis
Live load Buckling Factor = 6. 9
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Structural Analysis
Wind load horizontal deflection= 26mm @ deck, 40mm on roof
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Eigen- Value Analysis
Summary of Natural Frequencies
Loaded 1.5 people / m2
Unloaded bridge
Mode
Frequency
Hz
Shape
Minimum
Allowable
Frequency Hz
Shape
Minimum
Allowable
1
4.06
Lateral
1.5
3.44
Lateral
1.5
2
6.37
Torsion
1.5
5.20
Vertical
5.0
3
6.51
Vertical
5.0
5.42
Torsion
1.5
4
8.73
Roof
N/A
8.73
Roof
N/A
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Aerodynamic Stability
• Assessed to Eurocode 1 , UK National Annex
and PD6688.
• Initial analysis did predict possible
aerodynamic instability.
• Modifications to end frames
increased torsion mode of
vibration from 3. 3 to 6. 4 Hz
and resolved these concerns.
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Train Aerodynamic Buffeting
• 60mph line speed
• Loads derived from previous
work on Bradkirk bridge with NR
• Loading curve derived from
Eurocode 1 .
• Dynamic response very low.
Deflection
curves
• Max acceleration at deck =
0. 0262g = 0. 257m/s2
• Max deflection at deck =
0. 29mm
• Better understanding of loads
required for future bridges
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Acceleration
curves
Time = 1.0s
Conclusions
• 1 st FRP bridge at UK mainline station.
• 1 st Grade II Listed FRP Bridge.
• Aesthetically pleasing traditional appearance.
• An economic & durable solution.
• Only achieved thanks to teamwork between
Designers and Client.
• To be installed late 201 2.
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Dawlish FRP Footbridge
thank you – questions / discussion
Wendy Gough
Network Rail
David Kendall
Optima Projects Ltd T +44 (0)7774 887037
[email protected]
Ian Smith
Tony Gee & Partners
[email protected]
Optima Projects

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