FEMA E-74 Appendix E. Nonstructural Risk Ratings

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Appendix E. Nonstructural Risk Ratings

Explanation of Risk Ratings

The risk ratings that appear in this Appendix are provided as an aid to establishing priorities. Nonstructural components are organized by component type, and estimates of the potential risk posed by the component are given for different ground shaking intensities. Each component is rated for High (H), Moderate (M) or Low (L) potential risk to Life Safety, Property Loss, and Functional Loss. The seismic risk ratings are based on the following definitions and assumptions:

  • Shaking Intensity: For a particular geographic location in the United States, the shaking intensity may be estimated by using the seismic map in Figure 3.2.1-1 that show the areas that are likely to experience minimal, low, moderate, or high ground shaking during future probable maximum considered earthquake events that may affect the areas. The shaking intensity estimates based on the map in Figure 3.2.1-1 should be adequate for items situated at or near the ground in simple, nonessential facilities. For other situations, it may be advisable to choose the next higher shaking intensity or to seek the advice of professional consultants. Note that for areas with light shaking, a full blown upgrade of nonstructural components may not be warranted unless an owner is particularly risk averse; the current code would not require many of the protective measures recommended herein even for new construction.
  • Life Safety (LS) Risk: Risk of death or direct injury requiring hospitalization. This does not include the overall impact on life safety systems in a building, such as loss of emergency power in a hospital or loss of fire detection or suppression capability. These disruptions of service are covered under Functional Loss below.
  • Property Loss (PL) Risk: Risk of incurring a repair or replacement cost because of damage to the item. This property loss, as used here, includes the cost of fixing a broken pipe but not the indirect cost of water leakage damage, and includes the cost of repairing a computer but not the loss of business revenue computer downtime might cause. These indirect effects cannot be estimated here on a generic basis.
  • Functional Loss (FL) Risk: Risk that the item will not function because it has been damaged. This includes some consideration of the impact of this loss of function of the component on the operation of an ordinary occupancy building. Not included are off-site functional impacts, such as the loss of function of a piece of equipment because of a city-wide power outage. Outages of power, water, and other utility company or agency services are real problems to consider but are outside the scope of the item-by-item ratings here.
  • Type of Detail: For components where an illustrated example is provided in Chapter 6, the detail type is indicated as Non-engineered (NE), Prescriptive (PR), or Engineering Required (ER). The example number (e.g. 6.3.1.1 for adhered veneer) is shown at the left.
  • Assumption 1: The risk ratings are based on the assumption that the item has been installed without seismic bracing, seismic anchorage, seismic restraint, or allowance for differential movements. In areas of the U.S. where seismic building code provisions have only recently been enforced, this assumption will be generally true. In areas of the western U.S. where seismic codes have been enforced for some time, this assumption may not always be true. Particularly in buildings constructed in the western states since the mid-1970s, some nonstructural items may be anchored or braced, but the assumption of unanchored and unbraced items will still be true for many items on these lists.
  • Assumption 2: The item is assumed to be located at or near the ground level, or in a low-rise building. The most common case of a relatively stiff low-rise building with structural walls is presumed in the ratings here. Items such as full-height partitions and glazing are more likely to be damaged in flexible buildings that experience large lateral deformations. Damage to items sensitive to imposed deformation will be greater in buildings or portions of buildings that are more flexible, such as mid- and high-rise buildings; flexible frame buildings without significant structural walls; "soft stories" of buildings with structural walls in most stories but with a story, typically the ground story, that is much less laterally stiff because of the absence of walls; and the "soft wall" sides of bearing wall buildings where there is little or no solid wall area, such as the face of a typical commercial storefront building.
  • Assumption 3: For building occupancy, an ordinary occupancy category is assumed. Thus, in the case of essential or specialized facilities, some nonstructural components would be rated differently. For example, in this appendix the risk ratings are given for shelving in an ordinary occupancy building, but the same shelving would be rated quite differently with regard to Life Safety risk in a lab, Property Loss risk in a museum, or risk of Functional Loss in a communications center.
For most of the nonstructural components listed this Appendix, the risk ratings for those components would be reduced significantly if the components were installed or retrofitted in accordance with recommendations of Chapter 6 or were installed within a seismically isolated building.
 

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Last Updated: 
04/15/2015 - 10:34
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