Seismic mitigation final


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  • 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.
  • Seismic mitigation final

    1. 1. 1. Concepts and Terminology By,
    2. 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
    4. 4. Mitigation Four basic methods for Mitigation: Structural Non-Structural Locational Risk Transfer
    5. 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
    6. 6. Seismic Retrofits
    7. 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
    8. 8. Locational AP Zone Fault Shaking intensity map California Alquist-Priolo fault map, showing location of fault, and zone within which geologic investigation is required Actual fault
    9. 9. Risk Transfer Insurance company Reinsurance company Single buildings Insurance company Insurance company Single buildings Single buildings
    10. 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. 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. 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. 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. 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. 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. 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. 17. DETERMINE THE LEVEL OF SEISMIC HAZARD Figure 3-1: USGS Earthquake Hazard Map
    18. 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. 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.