Climate change impact on existing...
Transcript of Climate change impact on existing...
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Climate change impact on existingbridgesA STRUCTURAL ENGINEERS PERSPECTIVE
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Climate adaptation of structures
• For all structures throughout history
• Example: wind speed, design value 50 year
return period
• Temperature, snow, rain
• What we do:
– Calculate probability that capacity > load
– Safety classes and proven international
system
– From this the size of the members can be
derived or the safety of an existing structure
be checked
Source: Boverket
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Climate adaptation of structures
• But:
– Current loads are based on EVA, existing
data, stationary processes
– What happens if/when the basis change?
– We can update codes – but how about the
structures we already have?
– Will they be safe enough? How can this be
determined? Which structures are most
affected?
– Difficult to use current design proceedures
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Existing bridges
• Built to stand a long time, 50-100 years design
life
• Built with past climate as basis – no
consideration of climate change
• Could there be situations where the structures
are insufficient?
• What are the risks related to climate change for
bridges? – ongoing research in Lund
• Also research on how the basis may change, i.e.
the climate related loads (snow, wind,
temperature, rain)
• Collaborations with Rossby Centre, Rise,
Skanska, Öresund Bridge
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What can happen?
• Warmer
• Less permafrost/frozen roads
• Dryer/Wetter
• Sea level rise
• More extreme weather?
• Combination effects? E.g. Citytunnel in
Malmö during the storm Sven
Source IPCC
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How can that affect bridges?
• Material:
– Increased degradation
– CO2, temperature,
moisture
– Change in freeze-thaw
cycles – need for de-
icing salt in new
locations
Source Dunker and Rabbat (1993)]
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How can that affect bridges?
• Functionallity:
– Road, rail and structural
expansion, higher temperatures
– leads to damages in joints and
bearings for bridges
Heat induced joint buckling in Minnesota (2016)
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How can that affect bridges?
• Geotechnical (foundations)
– Increased scour rate
– Slope failures
– Landslides
– Rockfalls
Glenwood canyon rockslide (2010)
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How can that affect bridges?
• Load change
– Wave loads
– Wind loads
– Thermal loads
– …
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Royal Gorge bridge, Colorado during the 2013 wildfire
How can that affect bridges?
• Extreme events
– Wildfires
– Storm intensity or
frequency
– Floods
Flooding of the Sorlie bridge during the 1997 Red Riber of the North flood
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How to handle this
• Difficult with current practice and regulations
• Proposal:
– Identify critical risks
– Weighing consequence
– Find suitable measures
» Strengthen?
» Do nothing – no increased risk for damage?
» Accept increased risk?
• The question for us
– How much does climate adaptation cost in relation to the cost of not
adapting?
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Risk prioritization
• Several definitions of risk exist
• Our idea:
• Hazard – related to the probability of the climate event
• Exposure – related to the potential impact to the structure
• Vulnerability – how critical is it, potential damage
• Consequences – what can happen
)()()()( DCHEDPHEPHPR =
Hazard ExposureVulnerability
Consequences
Risk
value
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Risk prioritization
• Challenges:
– How to find the numbers?
» Experts, literature review,
» sometimes even personal opinion of the decision maker
– How can this be a general framework, but usable for individual bridges?
» Vast scope, individual bridge small scale
– How to combine all the knowledge and science needed?
» Large amount of research and information, limitations needed
• Ongoing work, framework will be presented during next year
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Future questions
• Is it worth strengthening a stucture with a low probability of hazard/exposure but
large consequences?
– If something happens it will be devastating, but it is very unlikely
• Can we let some structures/bridges be destroyed during an extreme event?
– How can we ensure safety for the users in such a case
• What are the indirect costs of closing a road or rail as a precaution?
• Combine this framework with decision methods, what are the ”best” decisions
• Holistic approach, not only look at one individual object, but the entire
infrastructure system
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