Risk Management Series 
Design Guide for Improving School Safety in Earthquakes,  
Floods, and High Winds 
 
January 2004 

 
 
 

MAKING SCHOOLS SAFE AGAINST EARTHQUAKES     4 
 
 
 
4.1 INTRODUCTION 
 
This chapter outlines the earthquake risk to schools and the processes and  
methods that can be used to reduce it. An explanation of the nature and probability of earthquakes is provided, together with procedures for determining the earthquake threat to specific locations. An assessment of the scope and effectiveness of seismic building codes is followed by an explanation of how to evaluate the vulnerability of a school building. Current methods of designing for seismic resistance in new buildings and upgrading existing buildings lead to a discussion on determining acceptable risk and the use of performance-based design to achieve community objectives in providing for seismic safety.  

4.2 THE NATURE AND PROBABILITY OF EARTHQUAKES   
Although earthquakes cannot be prevented, modern science and engineering  
provide tools that can be used to reduce their effects. Science can now identify, with considerable accuracy, where earthquakes are likely to occur and what forces they will generate. This information is readily available and can be obtained for local geographic regions (see Section 4.2.3).   
 
 
4.2.1Earthquakes and Other Geologic Hazards 
 
Earthquakes have long been feared as one of nature's most terrifying phenomena.  
Early in human history, the sudden shaking of the earth and the death and  
destruction that resulted were seen as mysterious and uncontrollable. We now  
understand the origin of earthquakes and know that they must be accepted as a  
natural environmental process. Scientific explanations, however, have not lessened the terrifying nature of the earthquake experience. Earthquakes continue to remind us that nature can, without warning, in a few seconds create a level of death and destruction that can only be equaled by the most extreme weapons of war. This uncertainty, together with the terrifying sensation of earth movement, creates our fundamental fear of earthquakes. Beyond the threat to life is the possibility of the destruction of public and private property. Jobs, services, and business revenues can disappear instantly and, for many, homelessness can suddenly be very real. The after-math of a great earthquake can endure for years or even decades. Other types of phenomena sometimes accompany earthquake-caused ground shaking and are generally identified as geologic hazards: 
 
- Liquefaction occurs when loose granular soils and sand in the presence of 
water change temporarily from a solid to a liquid state when subjected to ground  
shaking. This condition occurs mainly at sites located near rivers, lakes, and bays.  
- Landslides, which involve the slipping of soil and rock on sloping ground, can be triggered by earthquake ground motion (see Figure 4-1). 
- Tsunamis are earthquake-caused wave movements in the ocean that travel at high speed and may result in large coastal waves of 30 feet or more. They are sometimes, and incorrectly, called tidal waves. 
- Seiches are similar to tsunamis, but take the form of sloshing in closed lakes or bays; they have the potential to cause serious damage, although such occurrences have been very rare. For all of the above geologic hazards, the only truly effective defense is the application of good land-use practices that limit development in hazard-prone locations. Seismic design and construction is aimed at reducing the consequences of earthquake-caused ground shaking, which is by far the main cause of damage and casualties.  
 
 
 
4.2.2Earthquakes: A National Problem 
 
Earthquakes in the United States are a national problem. This was recognized by 
the U.S. Congress in 1977 when it passed legislation authorizing the National  
Earthquake Hazards Reduction Program (NEHRP), which has supported considerable research and hazard mitigation implementation since that time. Most people now know that earthquakes are not restricted to just a few areas in the  United States, most notably California and Alaska, and that two of the greatest  earthquakes known occurred not in California, but near New Madrid, Missouri, in  1811 and 1812. As shown on a map of earthquake probability in the U.S., more than 40 of the 50 states are at risk from earthquake-caused damage, life loss, injuries, and economic impacts (see Figure 4-2). Certainly the likelihood of a damaging earthquake occurring west of the Rocky Mountains, and particularly in 
California, the states of Oregon and Washington, and Salt Lake City, is much greater than it is in the East, Midwest, or South. However, the New Madrid, Missouri, and Charleston, South Carolina, regions are subject to the possibility of severe earthquakes, although with a lesser probability than the western U.S. 
 
There are several common measures of earthquakes. Perhaps the most familiar is 
the Richter Magnitude, devised by Professor Charles Richter of the California 
Institute of Technology in 1935. Richter's scale is based on the maximum amplitude of certain seismic waves recorded on a standard seismograph at a distance of 100 kilometers (km) from the earthquake epicenter. Because the instruments are unlikely to be exactly 100 km from the source, Richter devised a method to allow for the diminishing of wave amplitude with increased distance. The Richter scale is logarithmic, and each unit of magnitude indicates a ten-fold increase in wave amplitude. The energy increase represented by each unit of scale is approximately 31 times. The scale is open-ended, but a magnitude of about 9.5 represents the largest possible earthquake.  
 
Table 4-1 shows significant earthquakes (Magnitude 6 or over) that occurred in 
47 of the 50 U.S. states between 1568 and 1989. Records show that some seismic zones in the United States experience moderate to major earthquakes approximately every 50 to 70 years, while other areas have "recurrence intervals" for the same size earthquake of about 200 to 400 years. 
These frequencies of occurrence are simply statistical probabilities and one or several earthquakes could occur in a much shorter than average period. With current knowledge, there is no practical alternative for those responsible for schools located in earthquake-prone regions but for them to assume that a large earthquake is likely to occur at any time and that appropriate action should be taken. Moderate and even very large earthquakes are inevitable, although very 
infrequent, in  areas of normally low seismicity. Consequently, in these regions, buildings are very seldom designed to deal with an earthquake threat; therefore, they are extremely vulnerable. In other places, however, the earthquake threat is quite familiar. Schools in many areas of California and Alaska will be shaken by an earthquake perhaps two or three times a year and some level of "earthquake-resistant" design has been accepted as a way of life since the early 20th century. Although, on a national basis, the areas where earthquakes are likely to occur and the potential size or "magnitude" of these earthquakes are well identified and scientists  have a broad statistical knowledge of the likelihood of their occurrence, it is not yet possible to predict the near-term occurrence of a damaging earthquake. Therefore, lacking useful predictions, it makes sense in any seismic region to take at least the minimum affordable prudent actions directed at saving lives. Because most lives are lost in earthquakes when buildings collapse, U.S. seismic building code 
provisions focus on requiring that the minimum measures necessary to prevent building collapse are taken. In California, schools are further protected by the Field Act of 1933, which mandated additional requirements relating to design qualifications, plan checking, and site inspection. (The Field Act is discussed in more detail in Section 4.3.2.) The following graphics explain some earthquake terminology and characteristics of  ground motion. 
 

4.2.3 Determination of Local Earthquake Hazards  
 
Until quite recently, the United States was divided into a number of seismic 
zones,  which were shown on the maps in the model codes. Zones ranged from Zone 0 (indicating no seismicity) to Zones 1, 2A, 2B, 3, and 4. Zone 4 indicates the 
highest level of seismicity (see Figure 4-3; only Zones 0, 1, 2A, and 3 are shown). Each zone was allocated a factor, or coefficient, from 0.075 to 0.40; this value was a multiplier representing the acceleration value for which the building was to be designed. These values indicate a four-fold range in acceleration values between Zones 1 and 4. Within a zone, all buildings must be designed to the same acceleration value (or greater); contour lines show the boundaries between zones. Current codes, such as the International Building Code, define site seismicity in a different way. The United States is still divided into zones by contour lines, but their areas are much smaller. Numerical values are also shown on the maps and also represent the acceleration value to be used for design, but they are calculated in a different way, and many more values are shown that reflect greater precision of knowledge. Also, acceleration values for both long and short period buildings are shown in a separate series of maps. Figure 4-4 shows a portion of the earthquake ground motion map in the International Building Code 2003 corresponding to the region shown in Figure 4-3. The simplicity of the old seismic zones is lost, but the design information is much more detailed.
 
If the school district or community desires to obtain more detailed information on  the seismic hazard than is shown on the code maps, or if the location does not enforce a seismic code, but there is concern about seismicity, the U.S. 
Geological Survey (USGS) web page at www.USGS.gov, Earthquake Hazards Program, is an excellent resource. The USGS provides more detailed earthquake hazard maps for general regions such as the Western, Central, and Eastern U.S.  
Figure 4-5 shows a comparison between the Southeast U.S. and California. The larger acceleration values for the latter are symbolized by the darker colors. These maps are used as the basis for the maps shown in the IBC. Figure 4-6 shows a comparison, for the Southeast U.S., between acceleration values for a 1.0-second period building and a 0.2- second building. Note the larger acceleration values for the shorter period building.  
 
Figures 4-5 and 4-6 show values for a hypothetical earthquake with a 2-percent  
probability of exceedance in 50 years. This can be visualized as the odds of  
occurrence. The seismic code section of the IBC also shows values for earthquakes with a 10-percent probability of occurrence in 50 years (i.e., much shorter odds). For even more localized information, the USGS provides seismicity information for any location in the United States on the basis of latitude and longitude, or Zip Code.  
 
This information can be obtained by opening the Seismic Hazard listings on the  
USGS web page, and opening Hazards by Latitude and Longitude, or Hazards by Zip  
Code. These listings show information on the expected maximum shaking that is 
estimated for the location. The information and terminology are quite technical 
and  may need to be interpreted by qualified staff at the responsible local code 
office, a  structural engineer, or perhaps a knowledgeable seismic professional.  
 
 
 
4.3 VULNERABILITY: WHAT EARTHQUAKES CAN DO TO SCHOOLS 
 
This section reviews the experience of schools in earthquakes. Much of the  information presented comes from California, because of the prevalence of  earthquakes in that state. In general, the seismic performance of newer buildings has been good, although considerable costly and dangerous nonstructural damage still occurs. California public school design and construction has been subject to strict regulation since 1933 which undoubtedly contributes to good performance. Many of the damage examples shown in this section are of older buildings: this is relevant because schools are long-lived buildings and many schools constructed in the early decades of the 20th century are still in use. 


4.3.1 Vulnerability of Schools   
Older unreinforced masonry school buildings present a very high risk, and this type of structure has been prohibited by law in California since the mid-1930s, following severe damage to schools of this type in the 1933 Long Beach earthquake. A structural type that poses perhaps an even greater risk than unreinforced masonry is that of the mid-rise nonductile reinforced concrete frame. "Nonductile" refers to the frame's lack of ductility (flexibility), or ability to deform considerably before breaking (see Figure 4-7).  
 
Reinforced concrete frames are made ductile by introducing an appropriate, code- specified amount of specifically designed steel reinforcing; unfortunately, the need for this was not recognized in seismic codes until the mid-1970s and so a large inventory of these types of structure exists (see Figure 4-8). 
Wood frame structures perform effectively, provided that they are well constructed, particularly with respect to correct nailing of shear walls as specified in the code and properly detailed roof-to-wall connections. Good maintenance, ensuring continued protection against moisture and wood attacking insects, is also critical for wood frames. Newer structures, employing frames and fewer walls, also perform effectively if well designed and constructed; however, their response differs from that of shear wall structures, which are stiff and resistant to lateral forces. Frame structures are more flexible, which reduces the forces on the structural members and enables a light and safe structure to be designed.  
 
Modular classrooms are liable to topple off their foundations unless securely attached and braced. This damage is not life-threatening, but makes the building unusable; fractured power, gas, and waste lines may be a hazard (see Figure 4-9). 

If long-span roof and floor members are employed, however, there may be excessive drift, or sway, which causes damage to nonstructural components such as hung ceilings, light fixtures, light partitions, and contents. Piping, ductwork, electrical conduits, and communication pathways (cable trays) may also be damaged. Storage units, filing cabinets, and library shelving in any type of structure may be hazardous if not properly braced (see Figure 4-10). Broken pipes can create an additional hazard in the form of flooding, lack of fire protection water, and, with heating piping or domestic hot water piping, this could result in a flood of hot water. School occupants are particularly vulnerable to nonstructural damage. Although students and staff may duck under desks and be safe from falling objects such as lighting fixtures and ceiling tiles, ceiling components that fall in hallways and stairs can make movement difficult, particularly if combined with power failure and loss of lights. Additional falling hazards that are common in schools are large wall-mounted televisions (TVs) or ceiling mounted liquid crystal display (LCD) projectors. Heavy equipment can be hazardous and falling debris can also cause panic (see Figure 4-11). Pendant light fixtures have sometimes fallen if they are insecurely attached and not designed to swing freely (see Figure 4-12). Sudden breakage of large glass areas is a specific hazard because of the dense occupancy in many school rooms; design of glazing to resist wind-borne debris and physical attack may also assist in protecting it from earthquake motion. This kind of damage has been significant in California schools that have suffered recent earthquakes. Heavy hung lath and plaster ceilings in older auditoriums (and assembly buildings) can be dangerous and need careful inspection of their attachment and materials. If  deficient in safety, replacement is the only acceptable solution (see Figure 4-13). 
 
 
4.3.2 Earthquake Damage to Schools  
 
Most information on earthquake damage to schools comes from California. Its high incidence of earthquake activity has also resulted in sophisticated seismic building codes for all buildings and special plan checking and inspection requirements, enforced by the state, for school buildings.  Considering the number of significant earthquakes in California since the early years  
of the 20th century, there has been remarkably little severe structural damage 
to schools, except in the Long Beach earthquake of 1933, and there have been very few casualties. In California, no school child has been killed or seriously injured since 1933. This good fortune has been primarily because all major California earthquakes since 1925 have occurred outside school hours (see Figure 4-14). In the Long Beach earthquake that occurred at 5:55 p.m. on March 10,1933, damage to unreinforced masonry school buildings was so severe that there would have been many casualties had they been occupied. As a result, the state passed the Field Act within a month of the earthquake (see Figures 4-15 and 4-16). 
The Field Act required that all public school buildings be designed by a 
California licensed architect or structural engineer; all plans were to be checked by the then Department of General Services and construction was to be continuously inspected by qualified independent inspectors retained by the local school board. The Department of General Services set up a special division, staffed by structural engineers, to administer the provisions of the Act. The Field Act, which is still enforced today, has greatly reduced structural damage to California schools. 
The earthquake also resulted in the passage of the Riley Act, which governed all  buildings, with a few exceptions. The Riley Act required all buildings in the 
state to be designed to a specified lateral force, and effectively outlawed unreinforced masonry construction. 
In 1952, a series of earthquakes occurred in Kern County, in the Bakersfield region, some 70 miles north of Los Angeles. Two groups of earthquakes occurred; the first, in the last week of July, included one with a magnitude of 7.6 on the Richter scale. The second group occurred in late August, and one earthquake, near the city of Bakersfield, had a magnitude of 5.9 on the Richter scale. There were 10 deaths in the July earthquake and 2 in the August earthquake. 
 
This earthquake was of particular interest because the incidence of school damage might represent that of comparable earthquakes striking in regions today where seismic codes have not been adopted and enforced due to the rarity of seismic events (see Figures 4-17, 4-18, and 4-19). There were no casualties in schools in 1952, because these earthquakes also occurred outside school hours. At that time, the Field Act had been in force for nearly 20 years, and the newer schools had been constructed to conform to its requirements. Of the  
58 masonry schools in the region, 18 had been constructed after the Field Act. Of  these, one suffered moderate damage; this school was constructed of grouted  reinforced brick masonry and incurred approximately 1 percent damage. Of the 40 non-Field Act schools, 1 collapsed, 15 suffered severe damage, and 14 suffered moderate damage. In the Bakersfield City School District, 175 classrooms and 
6,500 students were displaced and only about 10 classrooms could quickly be put back in service. There was considerable nonstructural damage to ceilings and light fixtures. In other states, similar damage to unreinforced masonry (URM) and early reinforced concrete structures occurred. Considerable damage to schools occurred in Helena, Montana, in 1935 (see Figure 4-20). In 1949, severe damage was inflicted on several URM schools, resulting in one fatality, in Seattle (see Figures 4-21 and 4-22). At Puyallup High School, three boys on the stage just managed to escape when the roof collapsed (see Figure 4-23). Widespread damage to furniture and contents also occurred (see Figure 4-24).  
 
 
4.3.3 Significant School Damage in Recent U.S. Earthquakes 
 
In the Anchorage, Alaska, earthquake of 1964, which registered 8.4 on the 
Richter scale, a number of public schools were damaged, but there were no collapses. The earthquake occurred on Good Friday at 5:36 p.m., when the schools were unoccupied. The most seriously damaged school was that shown previously in Figure 4-1; the school was subsequently demolished. At the West Anchorage High School (see Figures 4-25 and 4-26), a two-story nonductile concrete frame and shear wall classroom wing suffered severe structural damage and near total failure in a number of columns. Structural distortion also created a number of severe glass breakages. The second floor was removed during reconstruction and the first floor was repaired and retained. 
 
In the San Fernando, CA, earthquake of 1971, there were no injuries and no schools collapsed; however, the earthquake caused $13.2 million in damages (in 1971 dollars), and 100 pre-Field Act schools were demolished within 112 years after the earthquake.  A survey of 1,544 public school buildings showed that only three schools sustained severe damage as a result of the Loma Prieta (San Francisco Bay area) earthquake of 1989. A portable classroom near Santa Cruz was rocked off its unbraced and unanchored supports. An elementary school in Los Gatos was subjected to severe shaking, but damage was limited to nonstructural and contents shifting, except in one classroom wing, where ground heaving raised and cracked the floor slab, jamming a door and window shut.  
A San Francisco High School suffered severe structural cracking. This school was constructed in 1920 as an automobile manufacturing building and was structurally  upgraded in 1947. Restoration costs were estimated at $10 million. Total restorations for the San Francisco school district were estimated to be $30 million; for Oakland, the district losses were $1.5 million. Though undamaged, an elementary school in San Francisco was closed because of the potential collapse of a nearby elevated freeway structure, which was considered a hazard to the building and its occupants. Hazards from unbraced and unanchored nonstructural items were evident in many buildings, including pendant-mounted light fixtures, suspended acoustical ceilings, and unanchored furniture and contents such as filing cabinets and shelving. In the Northridge, California, earthquake of 1994, state inspectors red-tagged 24 school buildings and yellow-tagged 82 school buildings, although this was later considered over-conservative. No structural elements collapsed. There was, however, considerable nonstructural damage that was costly to repair, resulting in the closure of a number of schools and, if the schools had been in session, would have caused  casualties. The Field Act focused on structural design and construction, and only recently were nonstructural elements included in the scope of the Act (see Figures 4- 27, 4-28, and 4-29). 
 
 
4.3.4 Consequences: Casualties, Financial Loss, and Operational Disruption 
 
Casualties in California schools have been few and minor, primarily due to 
regulation by the Field Act and by chance. Significant Alaskan and California earthquakes, from Santa Barbara (1925) to Northridge (1984) have all occurred outside of school hours: therefore, the effects of a major earthquake when schools are fully occupied have not been experienced. In other regions, casualties have been few; in the Seattle earthquake of 1949, two school children died in Tacoma when bricks cascaded onto  exit ways. The closure of Seattle schools for spring vacation had averted fatalities and  
serious injuries in similar building failures at a number of sites in the city. The impact of school closure as a result of damage is the loss of public service and severe disruption for students, faculty, and staff. Ultimately, the taxpayer will pay the costs, but this is spread over the whole community, the state, and the Federal Government. Typically, schools are self-insured and do not purchase insurance on the private market. For a private school, closure means a serious loss of revenue; in addition to the costs of repair, the students may not return if the school is closed for a long period of time. Therefore, obtaining insurance may be a prudent measure. As with any of the natural hazards reviewed in this manual, an earthquake can close a school, keeping the school district from doing its main job (i.e., teaching students). The length of the closure will depend on the severity and types of damage. It may also depend on whether the building was fully insured or whether disaster assistance will be available quickly enough to allow speedy repairs and reconstruction. Sometimes repairs are put on hold, pending a decision on whether the building should be repaired or condemned. There are also social and psychological factors, such as difficulties imposed on students, parents, faculty, staff, and the administration during the time the school is not usable. This is illustrated by the following quotation that, although it refers directly to hurricanes, also applies to earthquakes and other disasters.   
 
 
 
4.4 SCOPE, EFFECTIVENESS, AND LIMITATIONS OF CODES 
 
Building design in the United States has typically been regulated by the provisions of one of three model building codes: the National Building Code (NBC), published by Building Officials and Code Administrators International (BOCA); the Standard  Building Code (SBC), published by Southern Building Code Congress International (SBCCI); and the Uniform Building Code (UBC), published by International Conference of Building Officials (ICBO). The UBC tended to be most commonly adopted in the Western U.S., the NBC was used predominantly in the Northeast and Midwest, and the SBC was most commonly used in the South and Southeast.  
 
 
4.4.1 The Background of Seismic Codes 
 
Seismic codes currently in use in the United States have been very highly developed since the initial regulations for the protection of buildings against earthquakes first appeared in the UBC in California in 1927. Beginning in the 1950s, the earthquake-resistant design provisions of the three model codes used as the basis for building regulation in the U.S. were based on recommendations developed by the seismology committee of the Structural Engineers Association of California (SEAOC) and contained in their publication known as the "Blue Book."    
FEMA, one of the lead agencies in NEHRP, provided support for updating and  continued development of a seminal document, ATC-3-06, produced by the Applied  Technology Council (ATC), a non-profit research foundation set up after the San  Fernando earthquake of 1978 to work on recommended improvements in the seismic  building code. The ATC-3-06 document, now titled the NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, has been updated every 3 years since 1985. These provisions were adopted by the SBC in 1992 and, in 1997, the seismic provisions of the UBC and NEHRP were combined.  
Depending on which code regulated the structural design, seismic design was  conducted in accordance with one of two significantly different sets of provisions. Seismic design of structures under the UBC is governed by provisions developed by the SEAOC and structures designed under the NBC and the SBC are governed by somewhat different provisions developed by the Building Seismic Safety Council (BSSC) of the National Institute of Building Sciences (NIBS). 

Following a major effort by both groups, the 1997 editions of both the UBC and NEHRP Provisions resulted in a unification of these design approaches. 
 
Meanwhile, after years of negotiation, all three model code entities have now  
consolidated their services, products, and operations into one member service  
operation, the International Code Council. The ICC first published a unified model building code, the International Building Code (IBC) in 2000, with revisions planned  on a 3-year basis. The seismic provisions of the IBC are based primarily on the unified  UBC/NEHRP provisions. Subsequently, however, the National Fire Protection Association has also developed a model building code, the NFPA 5000, Building Construction and Safety Code, first issued in 2002. The American Society of Civil Engineers (ASCE) published ASCE 7 Minimum Design Loads for Buildings and Other Structures, which gives requirements for dead, live, soil, flood, wind, snow, rain, ice, and earthquake loads. ASCE 7 is referenced in the UBC, IBC, and NFPA model codes. Thus the seismic codes are in a state of transition, and the intent of developing a single, nationally applicable model code has not yet been realized. Currently, jurisdictions are faced with continuing with one of the three original model codes, which will become increasingly out of date because they will no longer be revised and published, or adopting the IBC or NFPA 5000 model codes. Some large municipal  jurisdictions will continue to produce their own codes, which will be derived from some combination of the model codes. 

As noted above, seismic codes have the primary purpose of establishing the minimum lateral forces for which buildings must be designed. To do this, the code provides an  
equation, in which the vibrating seismic forces are represented by a single static force, called the "base shear," applied at the base of a building. Variables in the equation enable the designer to adjust the design force for varying site seismicity, alternative soil conditions, different structural and nonstructural systems and materials, different building heights, and occupancies of varying importance. In addition, the codes have a number of provisions that deal with the detailed design of some building components, such as reinforcing steel in concrete structures and welding in steel structures. Because the actual forces on the building are estimated in a very simplified manner, a large safety factor is introduced, so that the design forces tend to be over-estimated. 
 
 
4.4.2 Seismic Codes and Schools 
 
Seismic codes are concerned primarily with types of structures and there are a 
few  provisions that relate to specific occupancies. The IBC categorizes school 
buildings  
as Type II:  "...buildings and other structures that represent a substantial 
hazard to  
human life in the event of failure..."  Type II buildings are assigned an 
Importance  
Factor of 1.25. This means that the seismic force calculated by use of the 
Equivalent  
Lateral Force procedure would be multiplied by 1.25 so that schools are designed 
to a  
higher standard than ordinary buildings.  
As previously mentioned, in California, K-12 schools are regulated by the Field 
Act,  
which is the only significant legislation that singles out the design and 
construction  
of schools to resist earthquakes and is an important model. However, the Field 
Act is  
not a code; it requires that schools be designed by a licensed architect or 
structural  
engineer, that plans and specifications be checked by a special office of the  
Department of the State Architect, and that independent testing and inspection 
be  
conducted during construction. The Greene/Garrison Act of 1976 made the Field 
Act  
provisions retroactive and required that all nonconforming schools be brought up 
to  
the current code level.  
 
Implementing the nonstructural provisions of the seismic code will significantly  
reduce damage to the nonstructural components and reduce the possibility of  
closing the school because of ceiling and lighting damage, partition failures, 
and  
loss of essential utilities. In this instance, the code goes somewhat beyond the  
structural objective of only reducing the risk of casualties. However, this is 
an  
important issue for schools, for recent experience in earthquakes has shown that  
nonstructural damage to schools is dangerous to the occupants, costly to repair, 
and  
operationally disruptive. 
 
 
4.4.3 The Effectiveness of Seismic Codes  
 
Building codes originated in the effort to reduce risk to health and safety, 
rather than  
reducing property loss, but, as they evolved, they indirectly and directly 
assisted in  
reducing building damage. They establish the minimum standards for safety  
commensurate with affordability and other impacts such as measures that might  
create extreme inconvenience to occupants or seriously reduce the building's  
functional efficiency. 
Among engineers, there is general agreement that, based on California's 
earthquake  
experience, regulation through a properly enforced seismic code has largely 
fulfilled  
the intent of ensuring an acceptable level of safety against death and injury. 
The  
performance of school buildings in recent California earthquakes substantiates 
this;  
structural damage has been minimal in the more recently designed schools.  
Application of the Field Act ensures that schools are designed and constructed 
to  
more rigorous standards than most other buildings.  
Some qualifications, however, follow: 
 
 Even in California, the standards of code enforcement vary considerably, and  
smaller jurisdictions may not have trained engineering staff to conduct 
effective  
plan checks and inspections.  
 The nonstructural provisions of the seismic codes are often not adopted at the 
local  
level. Even in California, nonstructural components have not been regulated to  
the same level of care as structural components, and have been the cause of  
considerable economic loss and disruption of operation.  
 In regions of moderate earthquake risk that have recently introduced seismic  
design regulation, the code may be misinterpreted and design errors made due to  
inexperience of both designers and building officials. 
 
 
 
4.5 EVALUATING EXISTING SCHOOLS FOR SEISMIC RISK AND  
SPECIFIC RISK REDUCTION METHODS 
 
A set of well developed procedures exists for the seismic evaluation of 
buildings, and a  
number of FEMA-sponsored publications are available to assist in the evaluation  
process. These guides have been developed since the 1980s and have been used  
extensively. However, this section also provides a simple seismic evaluation 
checklist  
that focuses specifically on schools. 
 
The procedures are listed below in the order in which they would be used, 
starting  
with a simple screening process.  
 
 
4.5.1 Rapid Visual Screening 
 
The Rapid Screening Procedure (RSP) was published in FEMA 154, Rapid Visual  
Screening of Buildings for Potential Seismic Hazards: a Handbook. The procedure 
is intended  
as an initial step in identifying hazardous buildings and their deficiencies. 
Buildings  
identified by this procedure to be potentially hazardous must be examined in 
more  
detail by a professional engineer experienced in seismic design. Because this  
screening is aimed at providing a low cost method of identifying large 
inventories of  
potentially hazardous buildings for public and private owners, and thus reducing 
the  
number of buildings that should be subject to a more detailed evaluation, it is  
designed to be performed from the street without benefit of entry into a 
building.  
The screening process can be completed in 20-30 minutes for each building. In 
some  
cases, hazardous details may not be visible, and seismically hazardous 
structures will  
not be identified as such. Nonstructural interior components are not evaluated.  
Conversely, buildings identified as potentially hazardous may prove to be 
adequate. 
Typically, a school district will not be faced with the problem of lack of 
building  
access and the RSP procedure is most useful for large school districts, 
municipalities,  
or even states that wish to get an economical preliminary evaluation of the 
seismic  
risks faced by their school inventory. The procedure is not intended to provide 
a  
definitive evaluation of the individual buildings.  
 
The methodology is based on a visual survey of the building and a data 
collection  
form used to provide critical information. The collection form includes space 
for  
sketches and a photo of the building as well as pertinent earthquake-safety 
related  
data. The FEMA handbook for the procedure provides the inspector with background  
information and data required to complete the form (see Figure 4-30). The 
procedure  
is designed to be usable by people with some knowledge of buildings who are not  
necessarily professional architects or engineers or familiar with seismic 
design. It has  
been successfully applied by architectural and engineering students. The  
methodology enables the inspector to identify significant seismic-related 
defects and  
to arrive at a numerical score, with a hazard ranking of 1-6 (see Figure 4-30). 
The ranking of surveyed buildings can be divided into two categories: those  
acceptable as to risk to life safety or those that may be seismically hazardous 
and  
should be studied further. A score of 2 is suggested as a "cut-off" based on 
current  
seismic knowledge (i.e., if a building has a structural "score" of 2 or less, it 
should be  
investigated by a structural engineer experienced in seismic design). 
 
 
4.5.2 Systems Checklist for School Seismic  Safety Evaluation 
 
Table 4-2 represents a simplified version of the FEMA 178/310 Evaluation 
Procedure;  
also see Section 4.5.3. This version focuses on structural and nonstructural 
systems  
and components that will be found in schools. The data are organized on a 
systems  
basis and are designed to establish whether the building is a potential seismic 
hazard  
and, if so, what its specific vulnerabilities are. Use of the checklist requires 
some  
seismic engineering knowledge, but the information can be obtained by inspection  
and no engineering calculations are necessary. The checklist can be used in  
conjunction with the RSP procedure, and will augment the RSP analysis because it  
assumes that the building will be accessible and design drawings are available. 
Both  
of these conditions are likely to be met in evaluating a public school building. 
The checklist can also be useful in interdisciplinary discussions between 
consultants  
and school district personnel, and can assist in fee negotiation with the 
client.  
 
 
4.5.3 The NEHRP Handbook for the Seismic Evaluation of Existing Buildings (FEMA  
178/310)  
 
For those buildings that, as the result of a preliminary screening, are 
candidates for a  
more detailed investigation, the BSSC developed a procedure for the systematic  
evaluation of any type of building (FEMA 178 and 310, The NEHRP Handbook for the  
Seismic Evaluation of Existing Buildings). This procedure can be used to 
evaluate the  
structural and nonstructural systems and components for any type or size of  
individual school building. However, the procedure focuses on evaluating whether  
the building is a potential earthquake-related risk to human life posed by the  
building or a building component. The procedure does not address code  
compliance, damage control, or other aspects of seismic performance not related 
to  
life safety. 
 
The handbook methodology involves the use of two sets of questions: one set  
addresses the characteristics of 15 common structural types and the other, 
instead of  
addressing complete structural systems, deals with structural elements, 
foundations,  
geologic site hazards, and nonstructural components and systems. These questions  
are designed to uncover the flaws and weaknesses of a building, and are in the 
form  
of positive evaluation statements describing building characteristics that are 
essential  
if the failures observed in past earthquakes are to be avoided. The evaluating 
architect  
or engineer should address each statement and determine whether it is true or 
false.  
True statements identify conditions that are acceptable and false statements 
identify  
conditions in need of further investigation. The handbook also specifies a 
process  
for dealing with statements that are found to be false.  
The evaluation requires some basic structural calculations and a site visit and 
follow- 
up field work will be necessary. The primary product of the evaluation is the  
identification of weak links in the building that could precipitate structural 
or  
component failure. Although the procedure will provide guidance on structural  
deficiencies, it is not intended to identify appropriate seismic retrofit 
options. The  
design engineer needs to understand the overall deficiencies of the building 
before  
attempting to identify retrofit design approaches. The overall deficiencies may 
be due  
to a combination of component deficiencies, inherent adverse design, 
construction  
failures, deterioration, or a serious weak link. 
 
 
  
4.6 EARTHQUAKE RISK REDUCTION METHODS 
 
Although the general principles of design are similar for new or existing 
schools,  
there are differences in code requirements and overall project delivery 
processes that  
reflect the design freedoms of new buildings and the constraints of existing 
ones.  
Engineering of structural and nonstructural risk reduction methods is similar 
for  
new and existing schools. New school design offers the possibility of 
construction on  
a site subject to less ground motion because of better soil conditions or 
further  
proximity to a fault. It can be designed with the most appropriate structural 
system,  
using known and tested materials and a good building configuration. These  
possibilities are not available when retrofitting an existing school; the 
building may  
have been designed to an obsolete seismic code or no code at all, its materials 
may be  
questionable, and the building configuration and structural system may be  
inappropriate. Therefore, the protection of an existing school must start with a  
careful evaluation of its vulnerability. Seismic retrofitting is expensive and 
time- 
consuming; however, the adoption of an incremental retrofit procedure, as 
described  
in Section 4.6.2, can help to keep time and cost within reasonable limits.  
 
 
4.6.1 Risk Reduction for New Schools 
 
Methods of design for earthquake protection involve three main aspects of the  
school: its site, its structure, and its nonstructural components.  
 
In terms of risk reduction, the first priority is the implementation of measures 
that  
will reduce the risk of casualties to students, staff, and visitors.  The second 
priority is  
the reduction of damage that leads to downtime and disruption. The third 
priority is  
the reduction of damage and repair costs. 
Alternative measures to achieve these objectives are as follows, in ascending 
order of  
cost: 
 
 New Schools Regulated by Seismic Codes 
 Provide personal protection training. 
 Evaluate code provisions against risk priorities. Evaluate whether design to  
current code will meet acceptable risk objectives for damage costs and  
reduction of downtime. 
 Consider adopting California's Field Act model for quality control of design  
and construction; can be administered by a single district with specification  
provisions for inspection in contract documents.  
 Use performance-based design procedures if code-based design does not meet  
acceptable risk objectives. 
 New Schools Not Regulated by Seismic Codes 
 Provide personal protection training. 
 Design to appropriate code standards on a voluntary basis. 
 Use performance-based design procedures to meet acceptable risk objectives. 
 Consider adoption of seismic code; requires community-wide cooperation. 
Damage reduction is common to all the objectives. The following sections give an  
overview of the design strategies that are used to achieve acceptable levels of  
protection in new schools. 
 
School Sites. Protection of schools and their occupants from earthquakes depends 
on  
correct seismic design and construction to resist the estimated earthquake 
forces that  
the building could encounter at its site. Because ground motion from a single 
earth- 
quake may vary considerably, depending on the nature of the soil and the 
distance of  
the building from known earthquake faults, careful site selection is a critical 
first step  
in reducing the forces on the building, although a single school site or a small  
district will rarely have this option. School sites are generally selected based 
on  
factors such as availability, served student population, cost, convenience of 
access for  
the school students and staff, and general demographic concerns rather than  
seismicity. However, a large district that is developing a multi-school plan of 
new  
facilities should include recognition of any natural hazard vulnerabilities as a 
factor  
in the evaluation of alternative sites. A school district can reduce its seismic  
vulnerability by reducing the intensity of earthquake shaking to be expected at 
a site  
over the life of the building. There are several ways in which this can be  
accomplished: 
 
 Locate the building in an area of lower seismicity, where earthquakes occur 
less  
frequently or with typically smaller intensities. Although it would be very rare 
for a  
school district to make a site selection decision based solely on seismic risk,  
moving a school even a few miles in some cases can make a big difference to its  
seismic hazard, such as locating a school within 1 mile of a major fault versus  
being 5 to 10 miles away from it 
 Locate the building on a soil type that reduces the hazard. Local soil 
profiles can be  
highly variable, especially near water, on sloped surfaces, or close to faults. 
In an  
extreme case, siting on poor soils can lead to liquefaction, land sliding, or 
lateral  
spreading of the soil. Frequently, similar buildings located less than 1 mile 
apart  
have performed in dramatically different ways because of differing soil 
conditions  
in earthquakes. Even when soil-related geologic hazards are not present,  
earthquake motions that have to travel through softer soils will be amplified 
more  
than those traveling through firm soils or rock. If general knowledge of site  
conditions is a concern, the effects of soil hazard on risk should be determined 
by  
the use of geotechnical and structural engineers to assess the potential  
vulnerabilities associated with differing site conditions. Variables in  
vulnerabilities should be weighed against the costs, both direct and indirect, 
of  
locating the facility on soils that will result in better performance. 
 
 Engineer the building site to increase building performance and reduce  
vulnerability. If building relocation to an area of lower seismicity or to an 
area  
with a better natural soil profile is not a cost-effective option, the soil at 
the  
designated site can sometimes be treated to reduce the hazard. For example, on a  
liquefiable site, the soil can be grouted or otherwise treated to reduce the  
likelihood of liquefaction occurring. Soft soils can be excavated and replaced, 
or  
combined with foreign materials to make them stiffer. Alternatively, the 
building  
foundation itself can be modified to account for the potential effects of the 
soil,  
reducing the building's susceptibility to damage even if liquefaction or limited  
land sliding does occur. The school board should weigh the additional costs of  
modifying the soil characteristics or the building foundation with the expected  
reduction in damage and loss. However, because most schools are one or two  
stories in height, site area usage is considerable, and site treatment is likely 
to be  
costly. 
 
In most cases, it is probable that a designated school site will be accepted. 
Proposed  
construction directly over a fault is probably the only location characteristic 
that  
would lead to rejection of an otherwise suitable site. The forces for which the 
school  
must be designed are also increased if it is in close proximity of a fault, 
which will  
increase the structural cost.  Sites are assigned to one of six categories, from 
A, which  
represents hard rock, to F, which represents soils vulnerable to potential 
failure or  
collapse such as liquefiable soils, sensitive clays, and weak soils and clays. 
Variations  
in soil type are covered by increasing or decreasing the design forces by 
application  
of a coefficient within the calculation of the Equivalent Lateral Force (ELF)  
equation, which is used to establish the design lateral forces on the building.  
The ELF procedure assumes a soil type B. For categories A through E, design 
forces  
must be modified by application of a coefficient, or multiplier. For Category A 
soils,  
the multiplier is 0.8  (i.e., the values are reduced). For Category E soils, the 
multiplier  
can be as high as 2.5 for short-period buildings such as schools. For buildings 
located  
on type F soils, a site-specific geotechnical investigation must be performed to  
establish design values. 
Reducing Damage to School Structures. Minimum standards and criteria for  
structural design are defined in the seismic codes. The codes provide maps that 
show  
whether the location is subject to earthquakes and, if so, the probability of  
occurrence, expressed by varying levels of seismic forces for which a building 
must be  
designed. Seismic codes are adopted by state or local authorities, so it is 
possible for a  
seismically-prone region to be exempt from seismic code regulations if the local  
community feels that the adoption of a seismic building code is not desired. 
Based on  
historic and scientific data, although the seismic hazard exists, some 
communities  
may choose to ignore the risk, because no one has experienced an earthquake in  
their lifetime. Such a policy should be of serious concern to school district 
officials,  
the local school board, and parents.   
This is a difficult issue because, although the risk may appear to be minimal, 
the  
effects could be catastrophic if a significant event were to occur. The very 
fact that  
such an event is rare means that the community may have no history of design for  
earthquakes and the building stock will be especially vulnerable. School 
buildings  
are an important community resource (along with other essential buildings such 
as  
hospitals, and fire and police stations) that should not gamble on the avoidance 
of a  
rare event.  
Because of systematic observation of earthquake damage to buildings and 
extensive  
analytical and experimental research, seismic design in the 20th century has 
become  
a highly developed technology.  
 
Reducing structural damage in earthquakes depends on: 
 
 The correct application of code criteria and analytical methods. Seismic codes 
have  
become increasingly complex and a high standard of care and engineering  
judgment is necessary to ensure correct application.  
 The correct selection and application of structural systems and materials. 
Different  
structural systems have varied characteristics that must be matched to the 
nature  
and purpose of the school. Flexible planning, for example, implies the use of a  
frame structure rather than relying on shear walls that may impact planning  
freedom.  
 The following two graphics show the basic types of structural lateral force 
resisting  
systems. 
 The correct design of critical elements such as frames, shear walls, and 
diaphragms  
and their connections to one another: earthquake forces search out the weak  
links between structural members.  Serious damage and collapse is often 
initiated  
by connection failure. These are the critical elements that provide seismic  
resistance; they must be correctly sized, located, and detailed.   
 Careful attention to key structural design principles such as provision of a 
direct  
load path and structural redundancy.  
 The correct design of the connections between structural elements and  
nonstructural components.  
 Configuration of the building (its size and shape) to be as simple and regular 
as  
planning and aesthetic requirements permit. Experience has shown that certain  
building shapes and architectural design elements contribute to bad seismic  
performance and need expensive structural design methods to make them  
achievable.  
 A high level of quality control to ensure that the building is properly 
constructed.  
Careful seismic design is valueless if not properly executed. 
 A high level of maintenance to ensure that the building retains its integrity 
over  
time. Corrosion of steel and termite infestation or dry rot in wood can 
seriously  
affect structural integrity. 
 
The following graphics show some problems caused by irregular building  
configurations. 
 
Reducing Damage to Nonstructural Components and Systems. Nonstructural  
components and systems are defined as those elements that do not contribute to 
the  
seismic resistance of the building (see Figure 4-31). They typically comprise 
from 75  
to 80 percent of the total school building by value, and they transform the 
structure  
into a working environment that provides weather protection, heating, cooling,  
lighting, and acoustic control. Damage to these components can be costly and  
render the building functionally useless even if the building structure performs 
in  
accordance with the intent of the seismic code. Nonstructural components are  
generally broadly classified as: 
 
 Architectural 
 Exterior envelope - opaque or glazed, roof and wall coverings 
 Veneers 
 Interior partitions 
 Ceilings 
 Parapets and appendages (e.g., signs and decorative elements)  
 Canopies and marquees 
 Chimneys and stacks 
 Mechanical  
 Boilers and furnaces  
 HVAC source equipment and distribution components 
 Electrical and Electronic 
 Source power equipment and distribution components 
 Source communications equipment and distribution components 
 Light fixtures  
 Plumbing 
 Storage vessels and tanks 
 Piping systems  
 Hazardous materials distribution 
 Furnishings and Interior Equipment  
 Bookcases, filing cabinets, and other storage  
 Shop and art equipment  
 Hazardous materials (HazMat) storage 
 
Reduction of damage to nonstructural components depends on using methods of  
supporting and bracing the components to prevent failure (see examples in 
Figures  
4-32, 4-33, 4-34, and 4-35). Seismic codes provide the design force for which 
the above  
components must be designed, together with a number of specific design  
requirements that must be followed.  
 
4.6.2 Risk Reduction for Existing Schools 
 
Procedures and Design Strategies. Additions to an existing school must meet all 
of the  
code requirements for a new building. There is currently no seismic code that 
applies  
to the retrofit of existing schools. Typically, the standards to be applied are 
derived  
from the code for new buildings and negotiated with the applicable building  
department. It is generally recognized that it is difficult or almost impossible 
to bring  
an existing structure up to full compliance with a current code and so some  
compromises have to be made; there is, however, no general agreement as to how 
the  
code for new buildings is applied to the retrofit design of existing ones.  
Reducing the seismic risk for an existing building requires the same general 
design  
principles as those necessary for a new building, but the architect and engineer 
are  
faced with existing structural and nonstructural systems and materials that may 
be far  
from ideal and, as previously stated, to bring them up to the standard of a new  
building could be difficult or almost impossible.  
 
The process should begin with an evaluation procedure similar to those outlined 
in  
Section 4.5. If the result of these evaluations is the need to retrofit an 
existing school  
or schools, the NEHRP Guidelines for the Seismic Rehabilitation of Buildings 
(FEMA 273) is  
the authoritative source document and can be used to help a school district 
select  
seismic protection criteria. The architect and engineer can also use the 
document for  
the design and analysis of seismic retrofit projects.  
 
FEMA 273 adopted the approach of providing methods and design criteria to 
achieve  
several different levels and ranges of seismic performance (unlike a 
conventional  
code that implies, but does not define, a single performance level). In doing 
this, the  
document shows that there is always the possibility of damage in a seismic event 
and  
the term "seismic performance" refers to the nature and extent of damage that 
the  
building exhibits. FEMA 273 provides a thorough and systematic procedure for  
performance-based seismic design, intended to result in the development of a 
design  
that targets achieving the owner's level of acceptable risk within the owner's 
available  
resources.  
 
The performance-based design approach outlined in FEMA 273 provides uniform  
criteria by which existing buildings may be retrofitted to attain a wide range 
of  
performance levels, when subjected to earthquakes of varying severities and  
probabilities of occurrence. The process starts by requiring that the user 
select  
specific performance goals as a basis for design. In this way, users can 
directly  
determine the effect of different performance goals on the design requirements,  
including their complexity and cost.  
 
Typical design strategies for improving the protection of an existing school 
include  
(see Figure 4-36): 
 
 Modifying and improving local components or materials, such as beam/column  
connections. This involves retrofitting connections and strengthening structural  
members by such methods as adding reinforcing or replacing them with new  
components. 
 Removing or reducing configuration irregularities. This involves providing 
seismic  
separations in irregular configurations or adding shear walls or bracing to 
reduce  
torsional effects, thereby strengthening and/or stiffening the entire structural  
system. This is a major retrofit that involves adding bracing or shear walls,  
replacing many structural members.  
 Reducing the mass of the building (to reduce forces). This involves changing 
the  
location of heavy items (e.g., bookcases) within the building, but would not 
apply  
to a one-story building, except where a tile or slate roof covering might be  
replaced with a lightweight material.  
 
Retrofit Methods. Seismic (base) isolation (to reduce force on the building  
superstructure) is a new technique that has been successfully used in the 
retrofit of  
large buildings, but it is not appropriate to the scale and nature of school 
buildings  
unless the school building is considered a historical building. A newer 
technique is  
passive energy dissipation, the insertion of supplemental energy devices (to 
reduce  
movement), which might be applicable to certain types of school structures 
(e.g.,  
large gymnasiums, multiuse buildings, or auditoriums).  
Seismic retrofit at any large scale is expensive, both in design and 
construction,  
because of the more complex analyses that must be conducted and the construction  
constraints that must be overcome. In addition, closure of a school for an 
extended  
period (beyond that of the normal summer break) is usually unacceptable. Major  
seismic retrofit is rare, although some successful projects have been done, 
primarily  
with the goal of saving a building that is not only a place of learning, but a 
historic  
community resource as well. The retrofitting of the B.F. Day School in Seattle 
was one  
such project (see Figures 4-37 and 4-38).        
 
Incremental Seismic Rehabilitation. An approach that greatly improves the 
feasibility  
of retrofitting a school is that of "Incremental Seismic Rehabilitation." A full  
description of this procedure is presented in Incremental Seismic Rehabilitation 
of School  
Buildings (K-12) (FEMA 395). The principles of this process follow. 
Whereas extensive single-stage seismic retrofitting of an existing school 
represents a  
significant cost, retrofit actions can be divided into increments and integrated 
into  
normal repairs and capital improvement projects. Implementation of incremental  
seismic retrofit requires assessing the buildings, establishing retrofit 
priorities, and  
planning integration with other projects. Integration will reduce the cost of 
the  
seismic work by sharing engineering design costs and some aspects of 
construction  
costs. An "integration opportunity" occurs when a seismic retrofit measure can 
be  
paired with other repair or replacement tasks or categories. Integration 
opportunities  
are a key consideration in determining the sequence of operations that will be  
conducted. 
School districts often categorize maintenance and capital improvement projects 
in  
the following eight categories; 
 
 Re-roofing 
 Exterior wall and window replacement 
 Fire and life safety improvements 
 Modernization/remodeling/new technology accommodation 
 Under floor and basement maintenance and repair 
 Energy conservation/weatherizing/air conditioning 
 Hazardous materials abatement 
 Accessibility improvements  
 
 
FEMA 395 provides five matrices that show possible combinations of seismic  
improvement measures with typical work categories. A typical matrix from FEMA 
395,  
showing possible seismic improvements relating to roof maintenance and repair is  
shown in Table 4-3. 
Incremental seismic retrofit is an effective, affordable, and non-disruptive 
strategy to  
achieve responsible seismic risk mitigation. 
At the lower levels of protection, some effective construction measures (e.g., 
bracing  
nonstructural bookcases and filing cabinets, and anchoring key desktop equipment  
such as computers) can be implemented by school district maintenance personnel.  
As a last resort in cases of extreme risk and badly antiquated school buildings,  
demolition is the only solution.  
 
 
 
4.7 THE SCHOOL AS A POST-EARTHQUAKE SHELTER 
 
In the aftermath of any damaging earthquake, there is an immediate need of 
shelter  
for people who have been displaced from their homes. There are three kinds of  
shelters: 
 
 First is the immediate need for shelter on the day or night of the earthquake. 
The  
American Red Cross has a congressional mandate to provide this after any  
disaster, with the intent that this will be available only for a few weeks. 
 Following the immediate need, there is a need for longer-term housing, while  
homes and apartments are being repaired. This is generally accomplished by  
governmental subsidies that enable people to move into vacant hotel rooms or  
apartments. This kind of shelter depends, to some extent, on the availability of  
these forms of housing on the market in the local area. This is sometimes  
augmented by temporary housing; where the season and climate allow, this can be  
provided by tents and FEMA has, in the past, maintained a stock of modular  
housing that can be moved to a local site within a month or two, depending on  
the availability of land. This housing may be occupied for a year or so, 
depending  
on the scale of the disaster.  
 Finally, there is permanent replacement housing that is typically provided by 
the  
home building industry and non-profit housing organizations, with possible  
financial aid programs from the Federal Government.  
 
It is common in earthquake-prone regions for school sites to provide the first 
kind of  
immediate shelter. There are several good reasons for this. First, schools are  
conveniently located in every community, with easy and known access to the local  
population that they serve. Second, schools have suitable space (e.g., 
gymnasiums or  
multiuse rooms) where large numbers of people can be accommodated for a few 
days.  
Food services are often available and there is ample space for assembly, 
processing,  
and delivery of goods and equipment. Third, because schools are public property, 
the  
financial costs of making use of the facilities for a few weeks are minimal, and  
arrangements can be worked out in advance. Finally, particularly in California, 
where  
schools are subject to the Field Act, schools are well constructed and probably 
among  
the most likely of all the community's buildings to survive intact and in a 
usable  
condition. 
The only problem that has been encountered is that of ensuring that the time of 
use  
is limited; no school district wishes for its schools to be used as shelters for 
weeks,  
unless it is during the summer break. However, improvisation can generally 
ensure  
that some semblance of a normal school teaching program can be reinstated within  
a day or so of a moderate event.  
No specific design decisions are necessary for this use, nor is it necessary to 
stockpile  
emergency supplies, because they could use up valuable storage space for years 
and  
then be useless if needed. The exact circumstances of the event and the number 
and  
types of people to be accommodated will determine the supplies that are 
necessary.  
Experience has shown that local and even regional manufacturers and suppliers 
are  
very effective in providing services after an event. Following the Coalinga 1983  
earthquake, temporary shelter was provided in the high school gymnasium. A  
regional beer canning plant substituted drinking water for beer for a few shifts 
and  
rapidly delivered the chilled cans to the site. 
However, pre-event planning should be undertaken between the school district and  
the local emergency services agency to anticipate key issues that will need 
quick  
solutions if an event occurs. This includes determining what spaces will be 
available  
and how many people can be accommodated, signing a pre-contract with a local  
engineer or architect for immediate post-earthquake inspection to determine 
safety,  
looking at strategies for continued operation in the event some spaces are 
occupied  
by refugees, and the possible provision of food and sanitary supplies by the 
district.  
Possible use of school buildings as a safe haven for the community in the event 
of  
chemical, biological, radiological, or explosive attack involves complex design 
and  
construction issues. This use of school property is discussed in FEMA 428, 
Chapter 6,  
and FEMA 453.  
 
 
 
4.8 REFERENCES AND SOURCES OF ADDITIONAL INFORMATION 
 
ASCE, 2000, Prestandard and Commentary for the Seismic Rehabilitation of 
Buildings, American  
 
Society of Civil Engineers, FEMA Publication 356, Washington, DC (FEMA 273  
published as a standard).  
 
Building Construction and Safety Code NFPA 5000, National Fire Protection 
Association,  
 
Quincy, MA, 2002 . 
Incremental Seismic Rehabilitation of School Buildings (K-12) (FEMA 395), 
Virginia  
Polytechnic Institute/Building Technology Incorporated, Silver Spring, MD/Melvyn  
Green & Associates, Inc., Torrance, CA, Federal Emergency Management Agency,  
Washington, DC, 2002. 
 
International Building Code 2003, International Code Council, Birmingham, AL, 
2003. 
 
Minimum Design Loads for Buildings and Other Structures, ASCE 7-02,  American 
Society of  
Civil Engineers, Reston, VA, 2002. 
 
NEHRP Commentary on the Guidelines for the Seismic Rehabilitation of Buildings 
(FEMA 274),  
Building Seismic Safety Council, Washington, DC, 1997. 
 
NEHRP Guidelines for the Seismic Rehabilitation of Buildings (FEMA 273), 
Building Seismic  
Safety Council, Washington, DC, 1997.  
 
NEHRP Handbook for the Seismic Evaluation of Existing Buildings (FEMA 178), 
Building  
Seismic Safety Council, Washington, DC, 1992. 
 
The NEHRP Recommended Provisions for Seismic Regulation for New Buildings, 2000 
Edition, 2  
volumes and maps (FEMA 368) and Commentary (FEMA 369). 
 
Primer to Design Safe School Projects in Case of Terrorist Attacks (FEMA 428), 
Federal  
Emergency Management Agency, U.S Department of Homeland Security,  
Washington, DC, 2003. 
 
Rapid Visual Screening of Buildings for Potential Seismic Hazards (FEMA 154), 
Applied  
Technology Council, FEMA, Washington, DC, 1988. 
 
Reducing the Risks of Nonstructural Earthquake Damage: a Practical Guide (FEMA 
74), Wiss,  
Janney, Elstner Associates, Inc., Washington, DC, 1994. 
 
Seismic Design Criteria of Nonstructural Systems for New School Facilities, EQE  
International/Salt Lake City School District, Salt Lake City, UT, 2001. 
 
 
 
 
4.9 GLOSSARY OF EARTHQUAKE TERMS 
 
Acceleration. Rate of change of velocity with time. 
 
Amplification. A relative increase in ground motion between one type of soil and  
another or an increase in building response as a result of resonance.  
 
Amplitude. Maximum deviation from mean of the center line of a wave. 
 
Architectural Components. Components such as exterior cladding, ceilings,  
partitions, and finishes. 
 
Building. Any structure whose use could include shelter of human occupants. 
Component (also Element). Part of an architectural, structural, electrical, or  
mechanical system. 
 
Configuration. The size, shape, and geometrical proportions of a building. 
 
Connection. A method by which different materials or components are joined to 
each  
other. 
 
Damage. Any physical destruction caused by earthquakes. 
 
Deflection. The state of being turned aside from a straight line, generally used 
in the  
horizontal sense; see also "Drift." 
 
Design Earthquake. In the IBC, the earthquake that produces ground motions at 
the  
site under consideratio 
n that are two/thirds those of the "Maximum Considered  
Earthquake." 
 
Design Ground Motion. See "Design Earthquake." 
 
Diaphragm. A horizontal or nearly horizontal structural element designed to 
transmit  
lateral forces to the vertical elements of the seismic force resisting system. 
Drift. Vertical deflection of a building or structure caused by lateral forces; 
see also  
"Story Drift." 
 
Ductility. Property of some materials, such as steel, to distort when subjected 
to forces  
while still retaining considerable strength. 
 
Earthquake. A sudden motion or vibration in the earth caused by the abrupt 
release of  
energy in the earth's lithosphere.   
 
Effective Peak Acceleration and Effective Peak Velocity-Related Acceleration.  
Coefficients shown on maps in the IBC for determining prescribed seismic forces. 
Elastic. Capable of recovering size and shape after deformation. 
Epicenter. A point on the earth's surface that is directly above the focus of an  
earthquake. 
 
Exceedance Probability. The probability that a specified level of ground motion 
or  
specified social or economic consequences of earthquakes will be exceeded at a 
site  
or in a region during a specified exposure time. 
 
Exposure. The potential economic loss to all or certain subsets of the built  
environment as a result of one or more earthquakes in an area; this term usually  
refers to the insured value of structures carried by one or more insurers. 
 
Fault. A fracture in the earth's crust accompanied by displacement of one side 
of the  
fracture with respect to the other in a direction parallel to the fracture. 
Focus. The location of a fault break where an earthquake originates; also termed  
"Hypocenter."  
 
Force. Agency or influence that tries to deform an object or overcome its 
resistance to  
motion. 
 
Frame, Braced. Diagonal members connecting together components of a structural  
frame in such a way as to resist lateral forces. 
 
Frame, Space. A structural system composed of interconnected members, other than  
bearing walls, that is capable of supporting vertical loads and that also may 
provide  
resistance to seismic forces. 
 
 
Frame System, Building. A structural system with an essentially complete space 
frame  
providing support for vertical loads; seismic forces are resisted by shear walls 
or  
braced frames.  
 
Frame System, Moment. A space frame in which members and joints are capable of  
resisting lateral forces by bending as well as along the axis of the members; 
varying  
levels of resistance are provided by ordinary, intermediate, and special moment  
frames as defined in the IBC with special frames providing the most resistance. 
"g". The acceleration due to gravity or 32 feet per second. 
 
Ground Failure. Physical changes to the ground surface produced by an earthquake  
such as lateral spreading, landslides, or liquefaction.  
 
Hypocenter. See "Focus." 
 
Intensity. The apparent effect that an earthquake produces at a given location; 
in the  
United States, intensity generally is measured by the modified Mercalli 
intensity  
(MMI) scale. 
 
Irregular. Deviation of a building configuration from a simple symmetrical 
shape. 
Joint. Location of connections between structural or nonstructural members and  
components. 
 
Liquefaction. The conversion of a solid into a liquid by heat, pressure, or 
violent  
motion; sometimes occurs to the ground in earthquakes. 
Load, Dead. The gravity load created by the weight of all permanent structural 
and  
nonstructural building components such as walls, floors, roofs, and fixed 
service  
equipment. 
 
Load, Live. Moving or movable external loading on a structure; it includes the 
weight  
of people, furnishings, equipment, and other items not permanently attached to 
the  
structure. 
 
Loss. Any adverse economic or social consequences caused by earthquakes. 
 
Mass. A constant quantity or aggregate of matter; the inertia or sluggishness 
that an  
object, when frictionlessly mounted, exhibits in response to any effort made to 
start it  
or stop it or to change in any way its state of motion. 
 
Maximum Considered Earthquake Ground Motion. The most severe earthquakes  
effects considered in the IBC.  These are represented by the mapped spectral 
response  
accelerations at short and long periods, obtained from maps reproduced in the 
IBC,  
adjusted for Site Class effects using site coefficients. 
 
Mercalli Scale (or Index). A measure of earthquake intensity named after 
Giuseppe  
Mercalli, an Italian priest and geologist. 
 
Nonbuilding Structure. A structure, other than a building, constructed of a type  
included in Chapter 14 of the IBC. 
 
Occupancy Importance Factor. A factor, between 1.0 - 1.5, assigned to each 
structure  
according to its Seismic Use Group (SUG). 
 
Partition. See "Wall, Nonbearing." 
 
Period. The elapsed time (generally in seconds) of a single cycle of a vibratory 
motion  
or oscillation; the inverse of frequency. 
 
P-Wave. The primary or fastest waves traveling away from a fault rupture through 
the  
earth's crust and consisting of a series of compressions and dilations of the 
ground  
material. 
 
Quality Assurance Plan. A detailed written procedure that establishes the 
systems and  
components subject to special inspection and testing. 
 
Recurrence Interval. See "Return Period." 
 
Resonance. The amplification of a vibratory motion occurring when the period of 
an  
impulse or periodic stimulus coincides with the period of the oscillating body. 
Return Period. The time period in years in which the probability is 63 percent 
that an  
earthquake of a certain magnitude will recur. 
 
Richter Magnitude (or Scale). A logarithmic scale expressing the magnitude of a  
seismic (earthquake) disturbance in terms of the maximum amplitude of the 
seismic  
waves at a standard distance from their focus named after its creator, the 
American  
seismologist Charles R. Richter. 
 
Rigidity. Relative stiffness of a structure or element; in numerical terms, 
equal to the  
reciprocal of displacement caused by unit force. 
 
Seismic. Of, subject to, or caused by an earthquake or an earth vibration. 
 
Seismic Event. The abrupt release of energy in the earth's lithosphere causing 
an  
earth vibration; an earthquake. 
 
Seismic Force Resisting System. The part of the structural system that is 
designed to  
provide required resistance to prescribed seismic forces.  
 
Seismic Forces. The actual forces created by earthquake motion; assumed forces  
prescribed in the IBC that are used in the seismic design of a building and its  
components.  
 
Seismic Hazard. Any physical phenomenon such as ground shaking or ground failure  
associated with an earthquake that may produce adverse effects on the built  
environment and human activities; also the probability of earthquakes of defined  
magnitude or intensity affecting a given location. 
 
Seismic Risk. The probability that the social or economic consequences of an  
earthquake will equal or exceed specified values at a site during a specified 
exposure  
time; in general, seismic risk is vulnerability multiplied by the seismic 
hazard. 
Seismic Use Group. A classification assigned in the Provisions to a structure 
based on  
its occupancy and use as defined in the IBC. 
 
Seismic Waves. See "Waves, Seismic." 
 
Seismic Zone. Generally, areas defined on a map within which seismic design  
requirements are constant; in the IBC, seismic zones are defined both by contour  
lines and county boundaries. 
 
Shear. A force that acts by attempting to cause the fibers or planes of an 
object to slide  
over one another. 
 
Shear Panel. See "Wall, Shear." 
 
Shear Wall. See "Wall, Shear." 
 
Speed. Rate of change of distance traveled with time irrespective of direction. 
Stiffness. Resistance to deflection or drift of a structural component or 
system. 
Story Drift. Vertical deflection of a single story of a building caused by 
lateral forces. 
 
Strain. Deformation of a material per unit of the original dimension. 
 
Strength. The capability of a material or structural member to resist or 
withstand  
applied forces. 
 
Stress. Applied load per unit area or internal resistance within a material that  
opposes a force's attempts to deform it. 
 
S-Wave. Shear or secondary wave produced essentially by the shearing or tearing  
motions of earthquakes at right angles to the direction of wave propagation. 
System. An assembly of components or elements designed to perform a specific  
function such as a structural system. 
 
Torque. The action of force that tends to produce torsion; the product of a 
force and  
lever arm as in the action of using a wrench to tighten a nut. 
 
Torsion. The twisting of a structural member about its longitudinal axis.  
 
Velocity. Rate of change of distance traveled with time in a given direction; in  
earthquakes, it usually refers to seismic waves and is expressed in inches or  
centimeters per second. 
 
Vulnerability. The degree of loss to a given element at risk, or set of such 
elements, resulting from an earthquake of a given intensity or magnitude; expressed in a scale  
ranging from no damage to total loss; a measure of the probability of damage to 
a structure or a number of structures. 
 
Wall, Bearing. An interior or exterior wall providing support for vertical loads. 
 
Wall, Cripple. A framed stud wall, less than 8 feet in height, extending from 
the top of the foundation to the underside of the lowest floor framing. 
 
Wall, Nonbearing. An interior or exterior wall that does not provide support for  
vertical loads other than its own weight as permitted by the building code; see 
also "Partition." 
 
Wall, Shear. A wall, bearing or nonbearing, designed to resist lateral forces 
parallel to the plane of the wall.   
 
Wall System, Bearing. A structural system with bearing walls providing support 
for all  
or major portions of the vertical loads; seismic resistance may be provided by 
shear  
walls or braced frames. 
 
Waves, Seismic. Vibrations in the form of waves created in the earth by an 
earthquake. 
 
Weight. Name given to the mutual gravitational force between the earth and an 
object  
under consideration; varies depending on location of the object at the surface 
of the  
earth