Risk Management Series Incremental Seismic Rehabilitation of Office Buildings Providing Protection to People and Buildings FEMA 397 December 2003 FEMA Part A: Critical Decisions for Earthquake Safety in Office Buildings A.1 Is There an Earthquake Hazard for Your Office Buildings? Earthquakes are one of the most serious natural hazards to which office building owners may be exposed. Although owners face a variety of risks to their investment and to tenant safety and operations that may appear more immediate, the consequences of earthquakes can be catastrophic. Therefore, despite the fact that earthquake occurrences are rare, earthquake safety should be given full consideration in design and investment for risk management and safety. The first step to understanding earthquake risk: RISK = HAZARD x VULNERABILITY is to learn the likelihood and severity of an earthquake affecting your buildings. The Earthquake Hazard: Where, When, and How Big The surface of the earth consists of solid masses, called tectonic plates, that float on a liquid core. The areas where separate plates meet each other are called faults. Most earthquakes result from the movement of tectonic plates, and seismic hazard is strongly correlated to known faults. A map of zones of seismic hazard for the United States, based on maps provided by the U.S. In Brief Geographic location is the most significant factor of seismic hazard. Soil conditions at a particular site also influence the seismic hazard. Geological Survey (USGS), shows three zones from the lowest, green, to the highest, red. The white areas have negligible seismic hazard. The USGS earthquake hazard map is based on a complex assessment of expected seismic activity associated with recognized faults. The scientific understanding of earthquakes continues to improve and has resulted in increased estimates of seismic hazard in various parts of the country over the last decade. Office building owners and managers responsible for the safety of tenants, visitors, and staff need to know whether to be concerned about earthquakes. Some guidelines for determining earthquake risk in your location are: If your office building is located in a red zone on the map Earthquakes are one of the most significant risks facing your facilities. Take immediate action to undertake comprehensive vulnerability assessment. Professional structural engineers should perform this assessment. Identify and either replace or rehabilitate vulnerable existing buildings as soon as possible. If your office building is located in a yellow zone The probability of severe earthquake occurrence is sufficiently high to demand systematic investigation of your buildings. Assign responsibility for investigation to the risk managers and facility managers within the organization. If they are not available, seek professional engineering assistance from outside. Identify vulnerable buildings and schedule them for replacement, rehabilitation, or change of use. Also consider mitigation of nonstructural hazards, such as securing equipment and suspended lighting that could injure building occupants in an earthquake. If your office building is located in a green zone Consider low-cost mitigation strategies that protect building occupants and the ownerÕs investment in facilities and systems, even though the probability of an earthquake is low. Beyond this broad seismic zone designation, expected earthquake ground motion at a particular location is further influenced by local geology and soil conditions. Geotechnical engineering studies should be done to understand fully the earthquake hazard at a particular site in red and yellow zones. A.2 Are Your Office Buildings Safe? The second step to understanding earthquake risk: RISK = HAZARD x VULNERABILITY is to learn the expected damage and losses that could result from an earthquake. What Happens to Office Buildings in Earthquakes Earthquake fault rupture causes ground motion over a wide area. This ground motion acts as a powerful force on buildings. Buildings are principally designed to resist the force of gravity, but resistance to earthquake forces requires specialized earthquake engineering. Horizontal earthquake forces cause rapid movement of the foundation and displacement of upper levels of the structure. When inadequately designed to resist or accommodate these earthquake forces, structures fail, leading to serious structural damage and, in the worst case, total building collapse. In addition to ground motion, buildings may suffer earthquake damage from the following effects: Fault rupture under or near the building, often occurring in buildings located close to faults. Earthquake-induced landslides near the building. Reduction of the soil bearing capacity under or near the building. Earthquake-induced waves in bodies of water near the building (tsunami, on the ocean and seismic seiche on lakes). In Brief Seismic vulnerability depends on structural type, age, condition, contents, and use of office buildings. Hazard exposure and building vulnerability may result in substantial death, injury, building and content damage, and serious disruption of building use and loss of rentals and leases. Building Age and Earthquake Vulnerability The first earthquake design legislation was enacted in 1933 for schools in California (the Field Act). Since that time, awareness of earthquake risk has expanded across the country, and building codes have been improved because of research and experience. Since the early 1990s, most new office buildings in the United States have been constructed in accordance with modern codes and meet societal standards for safety. However, older buildings should be reexamined in light of current knowledge. Some seismically active parts of the country (the Midwest) have only recently adopted appropriate seismic design standards, and in other parts of the country (the Northwest) estimates of seismic risk have been revised upward. The serious problem resides in existing vulnerable office buildings constructed without seismic requirements or designed to obsolete standards. The building code is not retroactive; there is no automatic requirement to bring existing buildings up to current standards. Safety in existing buildings is the responsibility of the owner/operator. That means you! Estimating Building Vulnerability It is possible to estimate roughly the vulnerability of an ownerÕs portfolio of buildings and to identify problem buildings with a technique called "rapid visual screening." An office building owner can produce generalized estimates of expected damage in the initial seismic risk assessment of its buildings. Engineers have defined levels of the damage that can be expected in particular types of buildings due to varying intensities of earthquake motion. These levels of damage range from minor damage, such as cracks in walls, to total building collapse. In addition to building type, expected damage is also a function of building age and the state of maintenance. Office buildings suffering from deferred maintenance will experience greater damage than well-maintained buildings will. For example, failure to maintain masonry parapets significantly increases the possibility of life-threatening failure in even a moderate earthquake. After initial rapid screening, specific seismic risk assessment for individual office buildings requires detailed engineering analysis. Other Earthquake Losses While a serious concern in its own right, building failure is the direct cause of even more important earthquake losses: Death and injury of tenants, visitors, and staff Destruction of contents and equipment belonging to tenants and owner Disruption of occupancy and rentals The expected extent of these losses can also be estimated based on hazard and vulnerability assessments. A.3 What Can Be Done to Reduce Earthquake Riskin Existing Vulnerable Office Buildings? Failure to address earthquake risk leaves the officebuilding owner exposed to potential losses, disruption,and liability for deaths and injuries. While purchasing insurance may protect owners from financial losses andliability, it still leaves them exposed to disruption as well as deaths and injuries.Only building rehabilitation can reduce losses, deaths, and injuries andcontrol liability and disruption. The implementation of seismic risk reduction through building rehabilitationwill primarily involve the facility manager. However, to be effective it willrequire coordination among the facility managers, risk managers, and financialmanagers. This is further discussed in Part B (for Facility Managers, RiskManagers, and Financial Managers). In addition, it is the responsibility of theoffice building ownerÕs top administrators to make sure that hazards are assessedand risk reduction measures implemented. Options for Seismic Risk Reduction The most important consideration for earthquake safety in office buildings isto reduce the risk of catastrophic structural collapse. Most likely in existingvulnerable buildings, structural collapse poses the greatest threat to life in amajor earthquake. Choosing the method of protection from structural collapsein a deficient building requires two criticaldecisions: Replace or Rehabilitate: If you decide toreplace a building, new construction iscarried out according to modern codesand can be assumed to meet current safetystandards. However, financial constraints,historic preservation concerns, and othercommunity interests may make the replacementoption infeasible. In that case, rehabilitation should beconsidered. Single-Stage Rehabilitation2 or Incremental Rehabilitation: Ifthe rehabilitation option is chosen, there are still issues of cost anddisruption associated with the rehabilitation work. The cost of singlestageseismic rehabilitation has proved to be a serious impedimentto its implementation by many office building owners. Incrementalseismic rehabilitation is specifically designed to address and reducethe problems of cost and disruption. Estimating the Costs and Benefits of Seismic Rehabilitation ofExisting Office BuildingsThe direct and indirect costs of seismic rehabilitation of a building are: Engineering and design services Construction Disruption of building occupancy and rentals during construction The benefits of seismic rehabilitation of a building are: Reduced risk of death and injury of tenants, visitors, and staff Reduced building damage Reduced damage of tenantsÕ or ownersÕ contents and equipment Reduced disruption of the delivery of occupancy and rental services Engineers have developed estimates of the reduction of earthquake damage that can be achieved with seismic rehabilitation following the Federal Emergency Management AgencyÕs (FEMAÕs) current rehabilitation standards. This type of estimate, however, may significantly undervalue the benefit of seismic rehabilitation. In considering the return on seismic rehabilitation investments, it is appropriate to consider the value of damages avoided as well as the difficult-to-quantify values of deaths, injuries, and disruption of occupancy and rental functions avoided. The primary obstacles to single-stage rehabilitation of vulnerable existing office buildings are the cost of rehabilitation construction work and related disruption of office rentals. Incremental seismic rehabilitation offers opportunities to better manage the costs and reduce disruption of rehabilitation. The following section introduces and explains incremental seismic rehabilitation in more detail. In Brief Whereas single-stage seismic rehabilitation of an existing office building represents a significant cost, rehabilitation actions can be divided into increments and integrated into normal maintenance and capital improvement projects. The implementation of incremental seismic rehabilitation requires assessing the buildings, establishing rehabilitation priorities, and planning integration with other projects. A.4 Incremental Seismic Rehabilitation of Existing Office Buildings Approach Incremental rehabilitation phases seismic rehabilitation into an ordered series of discrete actions implemented over a period of several years, and whenever feasible, these actions are timed to coincide with regularly scheduled repairs, maintenance, or capital improvements. Such an approach, if carefully planned, engineered, and implemented, will ultimately achieve the full damage reduction benefits of a more costly and disruptive single-stage rehabilitation. In fact, for office buildings, a key distinction between the incremental and single-stage rehabilitation approaches is that the incremental approach can effectively eliminate or drastically reduce disruption costs if the incremental approach can be organized so that most rehabilitation increments occur during the period of tenant turnover, or are carefully coordinated with tenant work. Incremental seismic rehabilitation can be initiated in the near-term as a component of planned maintenance and capital improvement with only marginal added cost. Getting started as soon as possible on a program of earthquake safety demonstrates recognition of responsibility for office building safety and can provide protection from liability. Assessment of Deficiencies A necessary activity that must precede a seismic rehabilitation program, be it single-stage or incremental, is an assessment of the seismic vulnerability of the ownerÕs building inventory. Facility managers can implement such an assessment using owner staff or outside engineering consultants as appropriate. The assessment should rank the building inventory in terms of seismic vulnerability and identify specific deficiencies. FEMA publishes a number of documents that can guide you through the assessment process. Portions of the assessment activities can be integrated with other ongoing facility management activities such as periodic building inspections. Facility assessments in more detail in Part B. Rehabilitation Strategy The incremental seismic rehabilitation program will correct the deficiencies identified by the assessment. The order in which seismic rehabilitation increments are undertaken can be important to their ultimate effectiveness. There are three aspects to prioritizing seismic rehabilitation increments: Structural Priority: An initial prioritization of seismic rehabilitation increments should be established primarily in terms of their respective impact on the overall earthquake resistance of the structure. Facility managers will begin with these priorities when determining the order of seismic rehabilitation increments to be undertaken. However, the final order of increments may deviate from this priority order depending on other planning parameters. Additional engineering analysis may be required for certain building types when deviating from the structural priority order. This subject is discussed in more detail in Part B, Section B.2, and Part C. Use Priority: Office building owners should consider planning alternative future uses of their existing buildings. Some vulnerable buildings may be scheduled for demolition or converted to other uses (for example, storage). Others may be scheduled for expansion and intensification of use. These considerations, among others, will influence the prioritization of seismic rehabilitation increments. Integration: A major advantage of the incremental seismic rehabilitation approach is that specific work items can be integrated with other building maintenance or capital improvement projects undertaken routinely. Such integration will reduce the cost of the seismic rehabilitation action by sharing engineering costs, design costs, and some aspects of construction costs. Integration opportunities are a key consideration in adapting the sequence of actions suggested by the foregoing discussions of rehabilitation priorities. Integration opportunities are discussed in more detail in Part C, Section C.2. Incremental Seismic Rehabilitation Plan An essential feature of implementing incremental seismic rehabilitation in specific office buildings is the development and documentation of a seismic rehabilitation plan. The seismic rehabilitation plan will include all the anticipated rehabilitation increments and their prioritization as previously discussed. The documentation will guide the implementation of the incremental seismic rehabilitation program and should ensure that the office building owner does not lose sight of overall rehabilitation goals during implementation of individual increments. Recommended Actions 1. Communicate the importance of assessing your building inventoryÕs risks and pass this manual on to the staff members responsible for facility management, risk management, and financial planning. Specify that they develop an analysis of the current seismic risk of your buildings and a strategy for risk reduction. 2. Promptly initiate a program of earthquake risk reduction in your buildings located in an earthquake-prone zone that were not designed and constructed to meet modern building codes. 3. Consider incremental seismic rehabilitation as a cost-effective means to protect the buildings and, most importantly, the safety of tenants, visitors, and staff, because it is a technically and financially manageable strategy that minimizes disruption of office building operations.