Shelley Jules-Plag

&

Hans - Peter Plag

Are Building Codes Consistent with our Knowledge of Geohazards?

Potential (Geo)hazards

Tsunami

Inundation(coastal)

Earthquakes

Flooding(inland)

Flooding(inland)

Inundation(coastal)

Storm(Wind)

(Surge)

(Storm Surge)

Landslides

Subsidence

Volcanoes

How do building codes relate to disaster reduction?

• Port-au-Prince, Haiti (Jan 12th, 2010)

• 7.0 magnitude earthquake

• Approx. 230,000 deaths

• Inter-American Development Bank estimates 14 Billion in damage.

• Most devastating natural disaster for any country since World War II.

• Combined effect based on magnitude of the quake; shallow depth under an urban center with high population density; poor building codes and enforcement.

How do building codes relate to disaster reduction?

How do building codes relate to disaster reduction?

• Santiago, Chile (Feb 27th, 2010)

• 8.8 magnitude earthquake

• Approx. 800 deaths

• Inter-American Development Bank estimates 15 - 30 Billion in damage.

• 6th highest magnitude earth quake in recorded history.

• Reduced effect due to 35 km depth; 335 km from Santiago and 105 km from Concepcion; enforced building codes.

How do building codes relate to disaster reduction?

• Dead Loads (considered constant all the time e.g. weight of structure) (low variance lows therefore easy to design for)

• Live (non-environmental) Loads (considered to be imposed temporary/dynamic loads e.g. vehicles on a bridge etc.) (probabilistic loads usually variable within the objects normal operating cycle; currently very well modeled)

• Environmental Loads (considered dynamic loads e.g. wind, snow, seismic, temperature, lateral pressure from soil, hydrostatic) (While these loads have been modeled successfully in many regions the increased threat of climate change may indicate that contemporary modeling is inadequate.)

• Other Loads (support settlement or displacement loads e.g. fire, corrosion, creep, explosion etc.) .

Building Codes (BC) are designed to promote the health and safety of the public.- the construction of structures that will safely resist all actions that they are exposed to during their lifetime (Standardization, 2002).

Building Codes are based on the forces that impact infrastructure and these are classified as structural loads .

How do building codes relate to disaster reduction?

Min and Max values for the loads are mostly based on probabilistic studies taking into account the loads originating cause; recurrence; distribution and static or dynamic nature (Rao, 1992).

BUILDING CODES

MIN to MAX Design/Load Factor

translates

Forces are not evaluated comprehensively.

What if MAX is underestimated?

What happens when there is a DOMINO EFFECT?

How do building codes relate to disaster reduction?

Min/Max and the Design/Load Factors are choices we make based on our understanding of risk and our value system.

How do we assess the risk?

Min/Max and the Design/Load Factors are choices we make based on our understanding of risk and our value system.

How do we assess the risk?

Hazard

In walks CLIMATE CHANGE .. . .

“a natural or man-made process that can cause harm to an entity (infrastructure, natural resources, human) if the entity is exposed to the process”.

Probability density function of the Hazard (certain intensity/certain probability).

“the degree of damage an entity will suffer under specific adverse conditions”

Depends on the intensity of the adverse condition (certain intensity/certain probability).

Vulnerability

“the replacement value of entities exposed to environmental conditions expressed in currency”

Depends on costs prescribed in each country and the value placed on human life (density x entity x currency value).

Assets

Risk = Hazard x Vulnerability x Assets

Risk (R) = Probability of Hazard (P) x Vulnerability of Asset (V) x Asset (A)

How do we assess the risk?

Risk = Hazard x Vulnerability x Assets

We have little control over Hazards

We can determine where we build.

We have a choice in how we build.

How do we control the risk?

We have little control over Hazards

We can determine where we build.

We have a choice in how we build.

These choices determine the risk we take.

Vulnerability and assets are directly within our sphere of control. Vulnerability depends on the characteristics of the entity and the potential impact that can result from the level of intensity of the adverse condition.

To what extent are these choices impacted by our knowledge of the hazards?

What risks are we willing to take?

Imperial Beach, CAHawaii

How do we approach the risk assessment?

• Deterministic approach– Rare earthquake selected

– Median or 84th percentile ground motion

• Probabilistic approach– Probability of ground motion selected

Return period defines rare

• Risk approach– Probability of consequence

Loss of life

Dollars

• Performance approach– Probability of damage states of structure

Structural fragility needed

HAZARDS VULNERABILITY

TOTAL RISKASSETS

• Exposure– Land use planning; zonation

How does hazard knowledge inform building codes?

• We have considerable knowledge of the probability density functions for most geohazards.

Understanding vulnerability is the key to being able to exercise control over the built environment.

• Uncertainties are largest at the upper end: impacts our choice of MAX.

• For some geohazards frequency and intensity is impacted by climate change (e.g. landslides): time variable probability.

• Damage can vary enormously due to type of construction and losses are related to use of the building: design/load factor.

How does hazard knowledge inform building codes?

• In a proactive approach science feeds into the development of the building codes.

• A more holistic approach promotes future adaptation to limit the effect of time variable natural hazards.

• The goal is to reduce the burden on society.

How do we reduce the burden on society?

• By making the right risk assessment

• Knowing the risk explicitly: educating the public and decision makers

What about perceptions????

• Acceptability of risk relies upon the presumption that there is a probability that an event might not occur.

• Population accepts the existence of these risks if they are below a certain threshold and if the benefits related to their existence exceed the perceived risks (Leiss 1994).

• Population seems effectively ready to accept a certain level of risk if they perceive it as being justified or if the risk allows them to reach some goal or provide certain advantages (e.g. generate jobs).

• More difficult for a risk to be accepted if it seems to be imposed or if it is in opposition with certain values.