Shelley Jules-Plag

1
Are Building Codes Consistent with our Knowledge
of Geohazards?

• Shelley Jules-Plag
• Hans - Peter Plag

2
Potential (Geo)hazards
Storm
(Wind)
(Storm Surge)
Tsunami
Inundation (coastal)
(Surge)
Flooding (inland)
Earthquakes
Subsidence
Inundation (coastal)
Volcanoes
Flooding (inland)
Landslides
3
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.

4
How do building codes relate to disaster
reduction?
5
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.

6
How do building codes relate to disaster
reduction?
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 .

• 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.).

7
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).
MIN to MAX Design/Load Factor
translates
BUILDING CODES
Forces are not evaluated comprehensively.
What if MAX is underestimated?
What happens when there is a DOMINO EFFECT?
8
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.
9
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.
10
How do we assess the risk?
Risk Hazard x Vulnerability x Assets
Hazard
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).
Vulnerability
the degree of damage an entity will suffer under
specific adverse conditions Depends on the
intensity of the adverse condition (certain
intensity/certain probability).
Assets
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).
In walks CLIMATE CHANGE .. . .
11
How do we assess the risk?
Risk Hazard x Vulnerability x Assets
Risk (R) Probability of Hazard (P) x
Vulnerability of Asset (V) x Asset (A)
We have a choice in how we build.
We can determine where we build.
We have little control over Hazards
12
How do we control the risk?
We have little control over Hazards
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.
We have a choice in how we build.
We can determine where we build.
To what extent are these choices impacted by our
knowledge of the hazards?
These choices determine the risk we take.
13
What risks are we willing to take?
Imperial Beach, CA
Hawaii
14
How do we approach the risk assessment?
HAZARDS
VULNERABILITY

• Deterministic approach
• Rare earthquake selected
• Median or 84th percentile ground motion
• Probabilistic approach
• Probability of ground motion selected
• Return period defines rare

• Performance approach
• Probability of damage states of structure
• Structural fragility needed

TOTAL RISK
ASSETS

• Exposure
• Land use planning zonation

• Risk approach
• Probability of consequence
• Loss of life
• Dollars

15
How does hazard knowledge inform building codes?

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

• 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.

Understanding vulnerability is the key to being
able to exercise control over the built
environment.
16
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.

17
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.