Climate change impact on existingbridgesA STRUCTURAL ENGINEERS PERSPECTIVE

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

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

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

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

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)]

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)

How can that affect bridges?

• Geotechnical (foundations)

– Increased scour rate

– Slope failures

– Landslides

– Rockfalls

Glenwood canyon rockslide (2010)

How can that affect bridges?

• Load change

– Wave loads

– Wind loads

– Thermal loads

– …

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

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?

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

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

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