2. Key Terms
Mitigation
Risk Mitigation Alternatives
Risk Transfer
Develop the Program
Benefit-cost ratio
Acceptable risk
Implement the Program
Funding
Seismic retrofit
Emergency planning
Maintain the Program
5. Structural (using buildings as an example)
Bracing
Types
“K”
“V”
Chevron
eccentric
“X”
(a) moment
frame
(b) braced
frame
diagonal
(c) shear wall
CPU
(e) damped
frame
(f) active control system: ground
motion sensor, processor, and
controlled mass
(d) base
isolation
7. NON-STRUCTURAL MITIGATION
• involves retrofitting a building’s non-structural elements
(exterior elements, interior elements, building electrical,
mechanical and plumbing systems, and contents).
• A breakdown of common non-structural mitigation techniques
is presented below:
•
1. Brace Exterior Elements
•
2. Anchor Interior Elements
•
3. Protect Building Electrical, Mechanical, and Plumbing
Systems
•
4. Secure Building Contents
10. Risk Mitigation Alternatives
EARTHQUAKE OCCURS
EARTHQUAKE OCCURS
Mitigation of
damage and
loss is possible
at each step of
earthquake loss
process;
earthquake
occurs, primary
hazards,
primary
damage,
secondary
hazard/damage,
primary loss,
and secondary
loss.
RESULT
MITIGATION
Hazard mapping; ground
remediation; tsunami walls…
Bracing and strengthening,
reduction of mass, base
isolation, structural control…
Improved storage/infrastructure,
better emergency response…
PRIMARY HAZARDS:
PRIMARY HAZARDS:
Faulting, Shaking, Liquefaction,
Faulting, Shaking, Liquefaction,
Landsliding, Tsunami…
Landsliding, Tsunami…
PRIMARY DAMAGE:
PRIMARY DAMAGE:
Building / Structural
Building / Structural
Nonstructural / Equipment
Nonstructural / Equipment
SECONDARY HAZARD / DAMAGE:
SECONDARY HAZARD / DAMAGE:
Fire, Hazmat, Flooding…
Fire, Hazmat, Flooding…
Demand (hazard)
Demand reduced
eliminated or(hazard)
eliminated or reduced
Capacity
Capacity
(strength…)
(strength…)
increased
increased
Secondary demands
Secondary reduced
eliminated or demands
eliminated or reduced
PRIMARY LOSS:
PRIMARY LOSS:
Life / Injury, Repair Costs, Function,
Improved emergency
Improved emergency
planning and response;
planning and response;
insurance…
insurance…
Life / Injury, Repair Costs,
Communications/Control… Function,
Communications/Control…
SECONDARY LOSS:
SECONDARY LOSS:
Business / Operations Interruption
Business / Operations Interruption
Market Share, Reputation…
Market Share, Reputation…
Loss
avoidedLoss
or shared
avoided or shared
11. Outline of Risk Reduction Program
Pre-program
Pre-program
Earthquakes are a
problem, in the most
Assess the Risk
Assess the Risk
general sense, solving a
problem has three basic
phases.
YAcceptable?
Stop
Stop YAcceptable?
Phase 1:
N
N
Understanding the
Develop the
Develop the
problem
Program
Program
Phase 2:
Finding the solution
Acceptable?
Acceptable?
Phase 3:
N
N
Y
Y
Putting the solution
Implement the Program
Implement the Program
into effect
Maintain the Program
Maintain the Program
Factors
Factors
-- Seismic environment?
Seismic environment?
-- Organization // decisionOrganization decisionmaking
making
-- Responsibility // liability
Responsibility liability
Data
Data
-- Seismic hazard
Seismic hazard
-- Exposure
Exposure
-- life
life
-- property
property
-- business // function
business function
-- revenue
revenue
-- data
data
-- market share
market share
-- reputation // image
reputation image
-- Vulnerability
Vulnerability
-- Assessment
Assessment
Mitigation Options
Mitigation Options
-- Locational
Locational
-- Redundancy // backup
Redundancy backup
-- Move
Move
-- Structural
Structural
-- Strengthen structures
Strengthen structures
-- Brace equpment //
Brace equpment
furnishings
furnishings
-- Operational
Operational
-- Emerency Plan
Emerency Plan
-- Backup data
Backup data
-- Transfer
Transfer
-- Insurance
Insurance
-- Contracts
Contracts
12. Measuring
Benefits
$
Constr.
Cost
Tot Cost
Cost
Damage
Design
Level
Benefit Cost Ratio BCR = PV (allfuturebenefits )
PV (allfuture cos ts )
Life Cycle Cost
LCC = PV (allfuturebenefits ) − PV (allfuture cos ts )
Internal Rate of Return is the discount rate that
“sets the net present value of the stream of net benefits
[and costs] equal to zero”- effectively a measure of the return on investment
13. Assess the Risk
Identify the assets (people, property, function) at risk.
Establishing (i.e. quantifying) the seismic hazard
It is a representation of how strongly the ground will shake
and how often it is likely to do so.
Developing performance objectives
The corresponding losses for people, property and function
are death and injury, financial loss, and business interruption,
revenue, market share.
No loss of life (no significant collapse hazard), limited
property loss, no loss of essential equipment, and restoration
of operation onsite or backup site within the time appropriate
for the organization.
Performing first a risk screening and then, for selected
structures, a more detailed review
14. Develop the Program
Developing the program, which consists of determining the
acceptable risk, the opinions that exist for reducing the
current risk to an acceptable level, the costs of doing that,
and how it should be accomplished.
Having performed risk screening, facilities may be usefully
grouped into several categories, such as
I.
II.
III.
Probable high risk
Possible high risk
Probable low risk
The category I and category II facilities should be subjected to
a more detailed analysis.
All the category I and II facilities can be ranked according to
their risk, mitigation costs, or other criteria. The ranking is
based on a benefit-cost ratio.
The final decision as to what facilities to mitigate will depend
on available budget and is the final expression of the
organization’s acceptable risk.
15. Implement the Program
Retaining seismic retrofit design professionals:
Initial investigation and screening
Detailed investigation and conceptual retrofit design
Construction documents and construction support
Funding the program; the following sources should generally
considered when planning programs of seismic mitigation .
General operating and maintenance funds
Bond issues
Special use fee
Hazard mitigation grants
Tax preferences and credits
Coordinating with other parts of the organization; it is very
important to include earthquake risk mitigation measures with
other facets of an organization’s asset management program.
16. Maintain the Program
Organizations are dynamic and facilities, operations, and
personnel are constantly changing. Thus documentation of
the step taken, including the process and criteria, is an
important step to complete.
As new facilities or operations are developed, the same or
enhanced criteria can be applied to them, thus retaining the
overall balance of earthquake mitigation program.
As new personnel join the organization, they can review the
earthquake mitigation program documentation and maintain
the overall goals.
17. DETERMINE THE LEVEL OF
SEISMIC HAZARD
Figure 3-1: USGS Earthquake Hazard
Map
18. Suggested Community Seismic Hazard Programs Based on Seismic
Hazard Levels
Map Colour
Suggested Community
Comments on Cost-
Hazard
Red
Seismic
Seismic Hazard
Effectiveness
Level
Mitigation Program
Moderately
High
Extensive program
Many, but not all mitigation
Mitigation of these facilities first priority
Red Orange
High
projects.
Substantial program
Some, but not all mitigation
Mitigation of these
projects
facilities a high priority.
Light Orange
Moderate
Mitigation of highly
Few mitigation projects
critical and highly
Vulnerable facilities should be considered.
Yellow
Moderately
Mitigation of very critical
Low
Very few projects
and very vulnerable
facilities should be
Gray
Negligible
except in unique
be considered
Seismic risk probably not
circumstances
Mitigation projects are most
likely not required or not
these facilities a low
Very Low
rarely be cost-effective
significant. Mitigation of
Blue
Mitigation projects will
vulnerable facilities should
Low
considered.
Mitigation of exceptionally
critical and exceptionally
Green
cost-effective
priority.
Seismic risk negligible.
Mitigation not required
Mitigation not required.
19. Summary
An Earthquake Risk Reduction Program involves the following
steps:
1.
ASSETS: Identify and map the assets at risk – the people, property,
business and cultural treasures. Where are they, how many are they,
what is their value?
2.
HAZARDS: Map the earthquake hazards that threaten these assets.
Hazards include faulting, shaking, liquefaction, tsunami, landslide, fire.
3.
VULNERABILITY: Assess the vulnerability of each asset to the hazards –
is an highly vulnerable, moderately, or just low?
4.
ANALYZE: Combine the information on Assets, Hazards and
Vulnerability into a Risk Analysis. Map the areas of High Risk.
5.
MITIGATION: Based on the assets, hazards and vulnerabilities, identify
various ways in which the risk can be lowered. Select the mitigation
method that makes the most sense – ie, is most effective for the least
cost.
6.
DEVELOP THE PROGRAM: Having a mitigation package, gather
community support and find ways to pay for the mitigation. Develop a
Plan for doing the mitigation over a several year timeframe.
Editor's Notes
This is the third and last of our presentations, and provides detail on Mitigation and how to develop an Earthquake Risk Reduction Program.
These are some of the key terms used in this presentation.
There are four basic methods for reducing earthquake risk, termed Structural, Locational, Operational, and Risk Transfer. Structural might also be termed ‘hardware’, and refers to structures resisting earthquake forces, or avoiding them (via for example base isolation). Locational is generally a planning approach, while operational generally refers to training and emergency response. All three of these tend to reduce the risk. Risk Transfer most typically involves insurance, and does not reduce the risk in absolute terms, but shares it, so that it is reduced in relative terms for each party. Besides insurance, there are other types of risk transfer.
The most traditional and common for reducing earthquake risk is to resist the risk via structural techniques. (a) Shows a basic building, whose structural type is called a ‘moment frame’. In order to strengthen this building against earthquakes, there are a number of methods available: (b) various types of bracing, such as K, V etc, can be added; (c ) a reinforced concrete shear wall can be added; (d) rubber pads can be placed under the building, to absorb the earthquake shock (this is termed base isolation); (e) damping devices can be added to the building, similar to shock absorbers in an auto; and/or (f) a mechanical device can be added to the building, to actively control it when an earthquake occurs. Of these various structural mitigation techniques, bracing and/or adding shear walls are the most traditional, and common. This discussion is only for buildings, and similar measures are also applicable to bridges and most other kinds of structures.
Here are a few examples of seismic retrofits – in this case, all are bracing added to buildings. In many other cases, the structural retrofit may be a RC shear wall, or other types of enhanced lateral force resistance.
Locational risk reduction simply means avoiding the risk. This can be accomplished for example by not building in areas of high shaking intensity, or on an earthquake fault, or in an area of liquefaction. While structural techniques are typically employed by engineers, locational techniques are usually employed by planners. Planning a city’s development is ways to avoid tsunami zones, landslides, liquefaction and other earthquake hazards is very effective. Hazard maps are needed for this kind of planning.
Risk Transfer traditionally refers to insurance, and is the method for reducing that risk that cannot otherwise be economically reduced by structural, locational or operational methods. Note that Risk Transfer doesn’t actually reduce the risk, but shifts it from the risk owner, to someone else (like the insurance company). Risk transfer typically doesn’t protect lives- if a building collapses, people are still killed. Insurance can be a mechanism for change however, if people see that its cheaper in the long run to reduce the risk via strengthening etc, rather than paying insurance premiums.
The four methods of risk reduction can be used to break the chain of loss causation. Structural, Locational, Operational and Risk Transfer methods should each be examined, and the capability to reduce the risk and their corresponding cost, determined.
The risk reduction program therefore consists of first determining the current level (or cost) of the risk, and the cost of reducing it. If the cost of reducing the risk is less than the reduction in the risk cost, the program is worth doing. If the cost or reducing the risk is less than the reduction in the risk cost, the program results in a net benefit, and is worth doing.
There are several ways to decide the best alternative – these include (1) total cost minimization, (2) benefit cost, (3) life cycle cost, and (4) internal rate of return. These are all ways to compare the cost of various alternatives. Of these, benefit cost ratio is the most popular. The graph shows the total cost, which is the sum of the present value of the capital expenditures, and the expected cost of damage, for varying levels of earthquake design. The optimum design level is the least total cost (the gold star).
In the second presentation, the basic method for calculating the loss was discussed and illustrated, although only property loss was considered in the simplified example. All assets at risk – people, property, function etc should be considered in a full risk analysis.
Having determined the current risk, and the potential for reducing the risk by various alternatives, the next step is to decide which alternatives are most appropriate – that is Develop the Program. A key step is deciding what is a “High Risk”, and what is a low risk. Typically, this is decided on a case-by-case basis, although some standards exist in some countries. Structural collapse or other life-threatening likely outcomes given a large earthquake, are typically High Risks, and not acceptable. Collapse of vital infrastructure, such as the main water supply, while it may not kill anyone, is typically found to be a High Risk, because clean drinking water is so important. Who makes these decisions, and who develops the program also varies case-by-case. Local authorities and citizens should cooperate in making the decisions, and the program is typically developed by the engineers, planners and managers who are usually responsible for the buildings and infrastructure.
Once the Earthquake Risk Reduction Program has been developed, the next step is to actually DO the Program – that is, implement it. This involves bringing in the appropriate planners, engineers and other specialists, and finding the funding. There are many sources of funding, which vary depending on the jurisdiction.
Lastly, once current risk has been reduced, it is important not to forget all about earthquake risk. An important thing is to maintain the program – population growth and other factors will continue to increase earthquake risk, and managing it is an on-going task. Earthquake risk reduction should be institutionalized within local government and the organizational culture.
This slide summarizes the key steps in managing earthquake risk, which consist in first identifying the Assets – that is, what do you have to lose? Important assets are people’s lives (eg, students in a school, or people’s homes and workplaces), critical facilities (hospitals, water and power supply), and the economy (ie, the key industrial and commercial buildings). Identifying these involves deciding who is responsible for each of these assets. For example the director of a school district is responsible for providing schools that will not collapse in an earthquake. That director should have an engineer study the schools to see if they could collapse in an earthquake that might occur in the region. That engineer will work with planners and geologists to study the Hazards in the region, and then study the Vulnerability of the school buildings. Based on this analysis, the engineer and his team will determine if the school buildings could collapse in an earthquake that might occur in the region. If they decide this could happen, the risk is too high, and something must be done. There are several ways to reduce or mitigate the risk – the school buildings can be strengthened (ie, structural approach) or moved to a safer site (ie, locational approach – this might be the best solution if for example the major threat to the school buildings was a landslide). If the highest hazard to the school buildings is not collapse, but perhaps a release of a dangerous substance in a nearby factory, then perhaps a plan for emergency evacuation (ie, an operational approach) is the most feasible solution. In every situation, the solutions must be decided case-by-case.
This concludes our presentation on Earthquake Risk Reduction. The next step is to check your knowledge of this material, via the Knowledge Check.