Risk Management Series
Design Guide for Improving Hospital Safety in Earthquakes, Floods, and High 
Winds
FEMA 577 / June 2007 


CHAPTER 2 MAKING HOSPITALS SAFE FROM EARTHQUAKES

2.1 INTRODUCTION

This chapter examines potential earthquake damage to hospitals and how these 
facilities can most efficiently improve their expected performance. An 
explanation of the nature and probability of earthquakes is provided, together 
with procedures for determining the approximate earthquake threat to specific 
locations. Typical seismic damages and the possible resulting effects on 
building function or risk to occupants are described and related to standard 
damage states currently used in performance-based earthquake engineering design.

The enhanced performance normally expected from hospitals is discussed, 
specifically as it relates to protection of inpatients and provision of care for 
the injured and other outpatients. Since many older buildings may not have been 
designed for seismic forces, particularly for enhanced performance, estimation 
of the actual expected performance is critical for adequate emergency planning.

The case studies in this chapter illustrate the performance of hospital 
buildings in earthquakes, and look at the enhancements made in the existing 
seismic protection of the structural and nonstructural systems to improve 
performance. The chapter ends with a review of best practices in seismic design 
and seismic retrofit of hospital facilities.

2.1.1 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. Firstly, science can now 
identify where earthquakes are likely to occur, at what magnitude, and determine 
the relative likelihood of a range of ground shaking levels. This information is 
readily available to architects, engineers, code writers, planners, and to the 
general public. Secondly, seismic researchers and structural engineers with 
experience in seismic design have sufficient understanding of the effects of 
earthquake shaking on buildings to create designs that will be safe for various 
intensities of shaking. Modern building codes incorporate all of this 
information and require buildings to have seismic designs appropriate for each 
region.

However, earthquakes are complex phenomena, and the exact nature of ground 
shaking, and a buildings response to that shaking, are still shrouded in 
considerable uncertainty. The primary intent of the seismic provisions of 
building codes is to provide buildings that will be safe in the expected 
earthquake. Current buildings designed to modern codes are extremely unlikely to 
sustain serious structural damage or partial collapse in a design earthquake. 
However, subtle changes in shaking from site to site, the wide range of building 
types and configurations, and the variation in skill and thoroughness with which 
any one building is designed and constructed can result in a wide range of 
damage levels in any given earthquake. Perhaps more importantly, many older 
hospital buildings were designed and built without seismic design features, or 
at best outdated ones. These buildings cannot be expected to perform well enough 
to serve their intended roles after an earthquake event. Lastly, it is now well 
known that the nonstructural systems of essential buildings are extremely 
important in maintaining post-earthquake functionality. Until very recently 
these systems, in general, have not been designed and installed with adequate 
seismic protection.

2.1.2 Earthquake Effects

Fractures and movements within the earths crust generate earthquake ground 
motion by sending waves through the rocks and soil outward from the source. Most 
commonly, these sources are known faults, defined as cracks or weakened planes 
in the earths crust most likely to break as a result of global tectonic 
movements. The propagation of the waves through the crust produces movement of 
the earths surface. Any one location on the surface will move in every 
direction simultaneously, back and forth, side to side, and up and down, 
creating the shaking effect that is both strange and frightening. The shaking 
effect, or seismic ground motion, is felt in all directions from the epicenter
the location where the fracture startedand diminishes with distance from the 
epicenter. Buildings, bridges, transmission towers, and other structures 
supported by, and attached to, the ground will also be shaken. If the intensity 
of shaking is high, most structures will sustain some damage. The criteria used 
to determine the capacity of the ground motion to inflict damage on the built 
environment are somewhat intuitive: large displacements of the ground (3 feet 
versus 3 inches), rapid changes in the movement (measured in units of 
acceleration), or the duration of shaking.

Although seismic ground motion is most often identified with earthquakes, it is 
not the only phenomenon that causes damage. Earthquakes involve movements of 
large portions of the earths crust, and the resulting shaking can produce other 
geologic hazards:

Surface Fault Rupture affects a small strip at the ground when the movement on a 
fault deep within the earth breaks through to the surface. The relative 
displacement of the ground on each side of the rupture may be several feet or 
more, and structures straddling this zone are likely to be severely damaged. 

Liquefaction occurs when the behavior of loose granular soils and sand in the 
presence of water changes temporarily from that of a solid to that of a liquid 
material when subjected to ground shaking. This condition occurs mainly at sites 
located near rivers, lakes, and bays.

Landslides occur when the top layers of soil and rock slip on sloping ground, 
triggered by earthquake ground motion.

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 waves similar to tsunamis. They can be triggered by earthquakes and 
generated by sloshing in closed lakes or bays; they have the potential to cause 
serious damage, although such occurrences are very rare.

2.1.3 Measuring Earthquake Effects

Earthquakes vary in many respects, but the resulting shaking depends mainly on 
the magnitude of the earthquake and the distance from the epicenter. The 
potential risk to manmade structures is determined on the basis of frequency of 
occurrence of earthquakes at a given site, and measurements of a number of 
physical characteristics of ground shaking. The following section discusses the 
measurements used for this purpose, and their role as damage parameters.

Perhaps the most familiar measure of earthquakes is the Richter Magnitude, 
devised by Professor Charles Richter of the California Institute of Technology 
in 1935. Richters 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 level is multiplied approximately by 31 for a unit 
increase in Ritcher magnitude scale. The scale is open-ended, but a magnitude of 
about 9.5 represents the largest earthquake scientists now expect within the 
current understanding of movement in the earths crust.

Among scientists, Richter Magnitude has been replaced by Moment Magnitude, a 
similar measure of energy that is based on the physical characteristics of the 
fault rupture, which is a more useful measure for large events. The Moment 
Magnitude scale has been set to produce values similar to the Richter scale, and 
for damaging earthquakes, values are normally in the 5.5 to 8.0 range, although 
magnitudes over 9.0 also occur.

The level of damage is often measured by intensity scales, and the most common 
scale used in the United States is the Modified Mercalli Intensity (MMI) scale, 
reported in Roman Numerals from I to XII. MMI is often incorrectly used to 
measure the size of an earthquake. In fact, the MMI is assigned to small areas, 
like zip codes, based on the local damage to structures or movements of soil. 
Many MMIs can be associated with a single earthquake because the shaking, and 
therefore the damage, diminishes as the distance to the epicenter increases. 
Although the MMI is useful for the purpose of comparing damage from one event to 
another (particularly events for which little or no instrumental measurements 
are available), it is very subjective, and scientists and engineers prefer 
instrumental measurements of the ground shaking to measure intensity.

[Begin text box]
It is important to understand that magnitude is not a measure of damage, but a 
physical characteristic of an earthquake. An earthquake with magnitude 6.7 that 
occurs in a remote area may cause no damage to manmade structures, but one with 
the same magnitude can cause considerable damage if it occurs close to an urban 
area.
[End text box]

Scientists and engineers need measures of the damaging characteristics of 
earthquakes to compare the inherent risk at different locations, and to develop 
design solutions to limit damage to acceptable levels. The universal 
characteristic of earthquakes, and the one that can be measured most precisely, 
is the ground motion. Extensive networks of instruments are now employed on the 
ground and in manmade structures to record continuously the motions during an 
earthquake. The ever-growing database of earthquake recordings can be analyzed 
in various ways to develop appropriate measures of intensity that best predict 
potential damage to buildings and other structures, and the possibility of 
liquefaction and landslides. Tsunamis and seiches are normally not caused by the 
traveling seismic waves, but by large, single movements of land under water as 
part of the fault movement or resulting large landslides.

2.1.3.1 Measuring Seismic Ground Motion

Acceleration is a measure of velocity changes over time, and is commonly 
experienced when our heads snap back when a car starts off rapidly. Similarly, 
acceleration causes a building to snap back as a result of sudden large ground 
movement. This movement within the building or other structure, which becomes 
very complex when caused by 20 seconds or more of ongoing, rapidly changing 
accelerations, is what causes direct shaking damage. Consequently, it is common 
to describe earthquake motion using the largest acceleration that occurred 
during the event, or peak ground acceleration (PGA).

Although PGA is useful as a simple way to measure and compare ground motions, it 
is not the most comprehensive one. From studies of ground motions and structural 
responses to ground motions, engineers and researchers have developed parameters 
that consider the characteristics of the entire motion, rather than the one 
instant when the PGA occurs. This characterization of the ground motion is 
called a response spectrum and measures the extent of shaking different 
structures will experience, based on their natural period of vibration, when 
subjected to a given ground motion (see section 2.2.2.1). The maximum response 
to a specific ground motion of a structure with a given period is called the 
spectral ordinate. The full response spectrum simply represents the suite of 
spectral ordinates for a wide range of structuresfrom periods of about 0.2 
seconds (short, very stiff buildings) to periods of about 4.0 seconds (tall, 
very flexible buildings).

Response spectra can be calculated for the entire database of recorded ground 
motions, and trends analyzed. For example, it has been determined that the 
response spectrum for most earthquake shaking has a similar shape, and that this 
shape has subtle changes based on the soil on which it was recorded. Figure 2-1 
shows the typical shape of earthquake ground motion spectra and the variations 
that will be caused, on average, by different site soils. Like PGA, higher 
spectral ordinates typically mean more intense and potentially damaging motions. 
By studying the location of potential earthquake sources and the probability of 
them generating an earthquake in any given time period, scientists can develop a 
response spectrum for earthquake shaking likely to occur at that site. This has 
been done by the U.S. Geological Survey (USGS) for the entire United States, and 
is the basis for seismic design requirements in building codes. This information 
is presented on maps. For simplicity, only two spectral ordinates are mapped, 
for periods of 0.2 second and 1.0 second. Examples of these maps are shown in 
Figure 2-2. Rules in the building codes allow engineers to calculate the 
appropriate spectral ordinate for all periods, as shown in Figure 2-1, based on 
the mapped values. Site classes in the figure are also defined in the building 
codes, Class A being hard rock, and Class E being a very soft site with 
potential soil failure.

[Begin Figures]
Figure 2-1: Graph showing representative shapes of building code (or 
design)response spectra for different soils. 

Figure 2-2: Two examples of national seismic hazard maps. One shows 1.0 spectral 
acceleration (%g) with 2% probability of exceedance in 50 years, and the second 
shows 0.2% spectral acceleration (%g) with 2% probability of exceedance in 50 
years. [end figures]

2.1.3.2 Measuring Potential for Liquefaction

Soils that are loose, not well graded, and saturated with water are prone to 
liquefaction. These conditions often occur near waterways, but not always. In 
addition to the soil type, the probability of liquefaction also depends on the 
depth from the surface to the layer, and the intensity of ground motion. 
Further, the results of liquefaction can vary from a small, uniform settlement 
across a site, to loss of foundation bearing, resulting in extreme settlement 
and horizontal movement of tens of feet (called lateral spreading). Lastly, the 
risk of liquefaction is directly dependent on the earthquake risk. Due to this 
complex set of conditions, damage potential from liquefaction is difficult to 
map. For all but the smallest projects, many building jurisdictions in seismic 
areas require identification of liquefaction potential in the geotechnical 
report, particularly in areas of known potential vulnerability. On sites where 
liquefaction is more than a remote possibility, the likely results of 
liquefaction at the ground surface or at the building foundations will also be 
estimated. Small settlements may be tolerated without mitigation. Larger 
potential settlements can be prevented by site remediation measures, if 
economically justified. In some cases of potential massive liquefaction and 
lateral spreading, using the site for structures may not be cost effective. 
Officials in some regions of high seismicity have developed maps of local areas 
that are potentially susceptible to liquefaction and require site-specific 
investigation.

2.1.3.3 Measuring Potential for Landslide

The shaking from earthquakes can also cause landslides, depending on the slope, 
type, and configuration of soil stratum. Landslides can cause damage to 
improvements built within the slide area or near the top of the slide, ranging 
from complete destruction to distortion from relatively small vertical or 
lateral movements. Sites can also be threatened by landslides occurring uphill, 
sometimes completely offsite and quite a distance away. Similar to liquefaction, 
accurate probability of land sliding is difficult to map on a regional or 
national scale, and this threat is normally identified in site-specific geologic 
hazard studies. Also similar to liquefaction, the largest portion of the risk 
may be a triggering event. In some cases, it is possible and cost effective to 
stabilize small areas at risk of potential landslides. Stabilizing larger areas 
at risk of landslides may not be feasible. Some regions of high seismicity have 
developed maps of the areas susceptible to landslides based on average slopes, 
geologic soil types, and the past history of sliding. Sites within these 
susceptible zones require site-specific investigation.

2.1.3.4 Measuring Potential for Tsunami and Seiche

Researchers have studied tsunamis and seiches for many years, but the tragic 
tsunami in the Indian Ocean in December 2004 highlighted the need for better 
measurement of the threat in terms of magnitude and location. Obviously, only 
sites near large bodies of water are susceptible, and normally at elevations 50 
feet or less above the water surface, although bays and narrow canyons can 
amplify the wave height. Although similar to storm surge, the height and the 
potential velocity of a tsunami wave represent a separate risk and must be 
mapped separately. In addition to dependence on local conditions, quantification 
of the risk from tsunamis and seiches is made more difficult because not every 
earthquake generates such a wave. Studies are required that consider the 
individual characteristics of the site and the facility, to establish the risk 
and identify possible mitigating measures.

2.1.4 Earthquakes: A National Problem

Most people now know that although most frequent in California and Alaska, 
earthquakes are not restricted to just a few areas in the United States. In 
fact, two of the greatest earthquakes in U.S. history occurred not in 
California, but near New Madrid, MO, in 1811 and 1812. In the International 
Building Code (IBC), the most common model building code in use in the United 
States and its territories, buildings on sites with a low enough seismic risk 
that specific design for seismic forces is not required are classified as 
Seismic Design Category (SDC) A. As shown in Figure 2-3, 37 of 50 States have 
regions with sufficient seismic risk to require designs more stringent than SDC 
A. The likelihood of a damaging earthquake occurring west of the Rocky 
Mountainsand particularly in California, Alaska, Oregon, Washington, and Utah
is much greater than it is in the East, Midwest, or South. However, the New 
Madrid and Charleston, SC, regions are subject to potentially more severe 
earthquakes, although with a lower probability, than most regions of the western 
United States. According to the IBC design maps and the USGS hazard maps upon 
which they are based, other locations should also plan for intermediate ground 
motions.

[Begin figure]
Figure 2-3: Map showing states with seismic risk. [End figure]

[Begin text box]
The U.S. Congress recognized earthquakes as a national problem by passing 
legislation authorizing the National Earthquake Hazards Reduction Program 
(NEHRP) in 1977. NEHRP has since supported numerous research and hazard 
mitigation efforts. 
[End text box]

Records show that some seismic zones in the United States experience potentially 
damaging 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 
healthcare facilities located in earthquake-prone regions but to assume that the 
design earthquake, specified in the building code for the local area, could 
occur at any time, and that appropriate planning for that event should be 
undertaken.

Moderate and even very large earthquakes are inevitable, although very 
infrequent, in some areas of normally low seismicity. Consequently, in these 
regions, most buildings in the past were not designed to deal with an earthquake 
threat; they are extremely vulnerable. In other places, however, the earthquake 
threat is quite familiar. Medical facilities 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.

Nationally, the areas where earthquakes are likely to occur have been 
identified, and scientists have a broad statistical knowledge of the potential 
magnitude of these earthquakes and the likelihood of their occurrence. However, 
it is not yet possible to predict the near-term occurrence of a damaging 
earthquake. Therefore, it makes sense to take the minimum precautionary measures 
and conform to local seismic building code requirements for new buildings. U.S. 
seismic building code provisions focus on requiring the minimum measures 
necessary to prevent building collapse, because most lives are lost in 
earthquakes as a result of building collapse. The code provisions for essential 
buildings intended to remain functional after a major earthquake have not yet 
been thoroughly tested.

[Begin text box]
If a healthcare facility 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 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 United States. Local building 
or planning departments, fire departments, or other local emergency management 
agencies should be consulted for the availability of mapping for liquefaction, 
landslide, tsunami, and seiche. 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 
referring to 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 other knowledgeable seismic professional.
[End text box]

2.2 SEISMIC BUILDING DESIGN

Seismic design is highly developed, complex, and strictly regulated by codes and 
standards. Seismic codes present criteria for the design and construction of new 
structures subject to earthquake ground motions in order to minimize the hazard 
to life and to improve the capability of essential facilities to function after 
an earthquake. To these ends, current building codes provide the minimum 
requirements necessary for reasonable and prudent life safety. 

More basic information about seismic design of buildings can be found in FEMA 
454, Designing for Earthquakes (FEMA, 2007)

[Begin text box]
Building design codes for cities, States, or other jurisdictions throughout the 
United States are typically based on the adoption, sometimes with more 
restrictive local modification, of a model building code. Up until the mid-
1990s, there were three primary model building code organizations: Building 
Officials and Code Administrators International, Inc. (BOCA), International 
Conference of Building Officials (ICBO), and Southern Building Code Congress 
International, Inc. (SBCCI). In 1994, these three organizations united to found 
the International Code Council (ICC), a nonprofit organization dedicated to 
developing a single set of comprehensive and coordinated national model 
construction codes. The first code published by ICC was the 2000 International 
Building Code (IBC; ICC, 2000) and was based on the NERHP Provisions. The IBC 
now references ASCE 7, Minimum Design Loads for Buildings and Other Structures 
(ASCE, 2005) for its seismic provisions. Some jurisdictions in the country may 
still be using the Uniform Building Code (UBC) seismic provisions (its final 
update was in 1997), while most have adopted or are preparing to adopt the IBC. 
In this document, code references are to the IBC Code and to its seismic 
standard, ASCE 7.
[End text box]

Seismic code requirements cover:
- A methodology for establishing the design ground motion at any site based on 
seismicity and soil type
- Procedures for the seismic analysis of the building structure and key 
nonstructural components and systems
- Some detailed design requirements for materials, systems, and components
- Definitions of irregular building configurations and limitations on their use
- Building height limitations related to structural type and level of seismicity

2.2.1 The Equivalent Lateral Force (ELF) analysis Methodology

Of the 96 equations in the IBC, the Equivalent Lateral Force (ELF) equation is 
the key element in the most-used code methodology for determining seismic 
forces. This force is termed the equivalent force because it represents, in 
greatly simplified and reduced form, the complex to-and-fro, multidirectional 
earthquake forces with a single static force applied at the base of the 
building. Once this force is determined, all the structural components of the 
building (walls, beams, columns, etc.) can be analyzed through other code-
prescribed procedures to determine what proportion of this force must be 
assigned to each of them. This general methodology is characteristic of all 
seismic codes throughout the world. 

The ELF equation is derived from Newtons Second Law of Motion, which defines 
inertial force as the product of mass and acceleration. The ELF equation 
replaces Newtons acceleration with an acceleration coefficient that 
incorporates some of the other factors necessary to represent more accurately 
the acceleration of the mass of the building, which is generally higher than the 
ground acceleration. To determine this coefficient, the code provides another 
equation and additional coefficients that encompass most of the characteristics 
that affect the buildings seismic performance. The ELF procedure is used for 
the great majority of buildings. Buildings of unusual form, or with other 
special features or site conditions, may be required to use more complex 
analytical methods.

Hospitals are classified in the building code as Occupancy Category IV  
essential for post-earthquake response and recovery  and therefore have 
special design requirements intended to improve performance. Designers should 
use 50 percent greater earthquake forces for design of Category IV buildings 
than for normal buildings, which will provide an additional safety factor and 
reduce potential structural damage. In addition, design rules for Category IV 
buildings allow less movement between floors during earthquake shaking, reducing 
nonstructural damage to windows, walls, stairways, and elevators. Lastly, these 
buildings are required to incorporate more complete and stronger anchorage and 
bracing of nonstructural components and systems than normal buildings.

2.2.1.1 Acceleration

The most common and widespread cause of earthquake damage is ground shaking 
caused by the seismic waves that radiate out from the focus of the earthquake. 
The waves begin like ripples in a still pond when a pebble is thrown into it, 
but rapidly become more complex. There are four main wave types, of which body 
waves, within the earth, are most important for seismic design purposes. First 
to arrive at a given site is the P or Primary wave: this wave successively 
pushes and pulls the ground along the wave front as it moves forward. The effect 
is felt as a sharp punchit feels as if a truck has hit the building. The P wave 
is followed by S, the secondary or shear wave, which is a lateral motion, back 
and forth, but perpendicular to the wave front.

The nature of the waves and their interactions are such that actual movement of 
the ground will be random: predominantly horizontal, often with considerable 
directional emphasis and sometimes with a considerable vertical component. 
Because of the random nature of the shaking, structures must be designed on the 
assumption that earthquake forces will come from all directions in very rapid 
succession, often fractions of a second apart.

The inertial forces inside the building, generated by ground shaking, depend on 
the buildings mass and acceleration [footnote 1]. The seismic code provides 22 
maps that provide values for spectral acceleration (the acceleration to be 
experienced by structures of different periods). These values, with some 
additional operations, are inserted into the ELF equation and provide the 
acceleration value and eventually the base shear value for the structure. 

[Begin footnote 1]
1. Acceleration is the change of velocity (or speed) in a certain direction over 
time, and is a function of the earthquake characteristics: acceleration is 
measured in g, which is the acceleration of a falling body due to gravity. 
[End footnote] 

[Begin figures]
Figure 2-4 shows an example of a portion of map from the IBC, showing contour 
lines of spectral acceleration. The numbers are the acceleration values to be 
used in the equation, based on the project location.

Figure 2-4 is a portion of an earthquake ground motion map used in the seismic 
code. [End figures]

2.2.1.2 Amplification and Soil Type

As seismic vibrations propagate towards the earths surface, they may be 
amplified depending on the intensity of the shaking, the nature of the rock and, 
above all, by the surface soil type and depth. Earthquake shaking tends to be 
more severe on soft ground than in stiff soil or rock, which produces greater 
building damage in areas of soft soils. This amplification is most pronounced 
for shaking at longer periods and may not be significant at short periods. 
Studies after the 1989 Loma Prieta Earthquake showed that shaking in the soft 
ground was 2.5 to 3.5 times that of shaking in rock.

The ELF equation deals with soil amplification by introducing a soil type 
coefficient in the process of determining the acceleration coefficient. The code 
defines six soil types, ranging from hard rock to very soft soil, and provides 
varying coefficients that relate soil type to building period, because the 
amplification is also modified by building period.

2.2.1.3 Building Period

All objects have a natural or fundamental period. This is the rate at which they 
will vibrate if they are given a horizontal push. When a building begins to 
vibrate as a result of ground motion, it will tend to sway back and forth at its 
natural period (Figure 2-5).

[Begin figure]
Figure 2-5 is an illustration showing that each object has its own fundamental 
period at which it will vibrate. [End figure]

More complex structures will oscillate at several different periods, the longest 
one (greatest amount of time to complete one cycle) often being called the 
fundamental period. The fundamental periods of structures vary from about 0.05 
second for a piece of equipment anchored to the ground to about 0.10 second for 
a one-story building. Taller buildings between 10 to 20 stories will oscillate 
in the fundamental mode at periods of between 1 and 2 seconds. The building 
height is normally the main determinant of building period (Figure 2-6), 
although more technically, the period is based on the mass and stiffness 
characteristics of the structure.

[Begin figure] Figure 2-6 is an illustration showing the period (in seconds) and 
building height. Height is the main building determinant. [End figure]

Acceleration within the building is influenced by its period, and diminishes as 
the period increases (the motion changes from abrupt shocks to a gentler 
swaying) as explained in Section 2.1.3.1.

2.2.2 Critical Building Characteristics 

2.2.2.1 Period and Resonance

As described in Section 2.1.3.1, the natural period of a building measures the 
time it takes to vibrate one full cycle. This basic characteristic of the 
structure will determine to a large degree how a building responds to earthquake 
ground shaking. Short, stiff buildings will have a short period and will shake 
with sharp, jerky movements (high accelerations), which will tend to cause 
contents such as equipment or furniture to slide around and possibly overturn. 
Taller, more flexible buildings will have longer periods and shake slower and 
smoother, but with larger to and fro movement than short buildings. The larger 
movements may create more relative displacement between floors and cause damage 
to walls, stairs, and elevators connected to multiple floors. In rare cases, 
buildings with periods over about 1.5 seconds on soft sites may match the 
vibration patterns of the site and resonate, causing large amplifications of the 
motions within the buildings.

2.2.2.2 Damping

A pendulum  or a childs swing  is a very effective oscillator, and will 
continue to swing for many minutes after a push, although the extent of the 
swinging, or amplitude, will gradually diminish. Buildings and other objects do 
not oscillate as effectively because the vibration is damped, or reduced. The 
extent of damping in a building depends on the structural system, materials of 
construction; how the structural components are connected; and on the type and 
quantity of architectural elements such as partitions, ceilings, and exterior 
walls. A high level of damping, in which the vibration of the building will 
rapidly diminish, is a desirable feature.

2.2.2.3 Nonlinear Behavior

It is generally not cost-effective to design buildings to be completely 
undamaged in strong earthquake motion. Building codes require designers to base 
their designs on forces that are not as great as the shaking can generate, on 
the assumption that the buildings structure will deform and absorb part of the 
energy, thus limiting the forces that can be generated. These severe 
deformations represent nonlinear behavior and structural damage, ranging from 
minor (that can be left alone) to more serious (that will require repair). The 
building code has been tuned over the last 5 or 6 decades by adjusting code 
requirements according to the results of detailed observations of the behavior 
of buildings. Nonlinear deformations are expected in hospitals and other 
critical buildings, but to a lesser extent than normal buildings. The intent is 
to minimize structural damage to enable the buildings to remain occupied after 
the shaking.

Some materials and structural systems can accept nonlinear behavior better than 
others and are thus considered superior seismic systems.

2.2.2.4 Ductility

Ductility is the characteristic of certain materials  steel in particular  
that fail only after considerable distortion or deformation has occurred. This 
is why it is more difficult to break a metal spoon by bending it than one made 
of plastic. The metal object will remain whole, though distorted, while the 
plastic spoon will break suddenly without warning (Figure 2-7). This property of 
materials is used to ensure that a building may adequately resist more than its 
design ground motion.

[Begin figure] 
Figure 2-7 is an illustration showing ductility. Ductility is the characteristic 
of materials such as steel that fail only after considerable deformation has 
occurred. Nonductile materials (like poorly reinforced concrete) fail without 
warning in a brittle manner. [End figure]

The deformation of metal, even in the spoon, absorbs energy and defers absolute 
failure of the structure. Brittle materials, such as unreinforced masonry or 
ceramic tile, fail suddenly with a minimum of distortion. Ductility is an 
important characteristic of the structural system. Thus, buildings with 
appropriate seismic designs are either designed so that the materials and 
connections will distort but not break, in case they are subjected to forces 
higher than those required by the code, or they are designed for very large 
forces. Some structural materials, like masonry and concrete, are brittle on 
their own, but when properly combined with steel reinforcing bars, can exhibit 
high ductility. This characteristic of the structural system is also considered 
in the ELF methodology.

2.2.2.5 Strength and Stiffness

Strength and stiffness are the two of most important seismic characteristics of 
any structure. Two structural beams may be equally strong (or safe) in 
supporting a load, but may vary in their stiffness  the extent to which they 
bend or deflect in doing so. Stiffness is a material property but is also 
dependent on shape. For vertical forces this is usually the only aspect of 
stiffness that is of concern. When floor joists are designed for a house, for 
instance, their deflection rather than strength is what often dictates their 
size. Typically, an unacceptable amount of deflection will occur well before the 
members are stressed to the point at which they break. 

In seismic design, there is another very important aspect to stiffness. The 
problem of determining the overall lateral force on the building by multiplying 
its weight by its acceleration has already been discussed. But how is this force 
distributed among the various structural members so that the engineer can design 
each one appropriately? Relative stiffness enters into this issue because the 
applied forces are attracted to and concentrated at the stiffer elements of 
the structurein engineering terms, the forces are distributed in proportion to 
the stiffness of the resisting elements. Mathematically, the stiffness of a 
structural member varies approximately as the cube of its length: thus one 
column that is half the length of another will be eight times stiffer (23) and 
will be subject to eight times the horizontal load of the long column. This 
concept has serious implications for structures with lateral members of varying 
lengths, and in designing such a structure the engineer tries to equalize the 
stiffness of the resisting elements so that no one member or small group of 
members takes a disproportionate amount of the overall load (Figure 2-8).

[Begin figure] 
Figure 2-8 is an illustration showing the short column problem. The stiffness of 
a column varies approximately as a cube of its length. The short column is half 
the height but takes 8 times the load of the long column. [End figure]

Short columns represent a problem that emphasizes the need for good structural 
seismic design. Columns in this category may not even be part of the lateral 
force resisting system. Nevertheless, if the structural and nonstructural 
components create such a condition, these columns are likely to be severely 
damaged during strong ground shaking. 

2.2.2.6 Drift

Drift is the term used in seismic design to describe the horizontal deflection 
of structural members in response to seismic forces. In the seismic code, limits 
are set on the amount of drift permitted. This is done to ensure that the 
structure will not be designed to be so flexible, even if structurally sound, 
that its nonstructural components will be unacceptably damaged. Drift is limited 
on a story basis. The allowable story drift is limited to floor-to-floor height 
times 0.010 (1 percent of the floor height) for essential buildings and 0.015 
(1.5 percent of the floor height) if the nonstructural components have been 
designed to accommodate drift. A story drift of 0.010 is equivalent to a 
deflection of 1-1/2 inches for a floor-to-floor height of 12 feet 6 inches 
(Figure 2-9).

[Begin figure] 
Figure 2-9 is an illustration showing allowable story drift. For most buildings, 
drift is limited to: floor-to floor height x 0.010 to 0.020. A story drift of 
0.010 = deflection of one and a half inches for a height of 12 feet 6 inches. 
[End figure]

2.2.2.7 Configuration: Size and Shape

Experience has shown that the architectural form of a building has a major 
influence on its performance during ground motion. This influence is the result 
of the three-dimensional interaction of all the structural systems and all 
architectural components when subjected to earthquake forces. For certain 
architectural forms, the response of the building can become very complex and 
the earthquake forces can become concentrated and distributed in undesirable 
ways. The term building configuration is used in seismic design to determine the 
architectural form of the building.

The kinds of unusual conditions that warrant concern are a result of early 
architectural decisions that determine the configuration of the building. In 
making these decisions, the architect plays a major role in determining the 
seismic performance of the building and can make it easy or difficult for an 
engineer to develop an efficient and cost-effective structural design. For 
seismic design purposes, configuration can be defined as building size and 
shape; the size and location of the structural elements; and the nature, size, 
and location of nonstructural elements that may affect structural performance. 
The latter include such elements as heavy and/or stiff nonstructural walls, 
staircases and elevator shafts, exterior wall panels, and heavy equipment items.

The seismic significance of the building configuration is that it determines 
both the way forces are distributed throughout the structure and the relative 
magnitude of those forces. Seismic codes distinguish between regular and 
irregular configurations, and it is the latter that may have a detrimental 
influence on the effectiveness of the seismic engineering and on building 
seismic performance. Configuration irregularity results in two main undesirable 
conditions  stress concentrations and torsional forces.

2.2.2.8 Stress Concentrations

Irregularities tend to create abrupt changes in strength or stiffness that may 
concentrate forces in an undesirable way. Stress concentration means that an 
undue proportion of the overall forces is concentrated at one or a few points of 
the structure, such as a particular set of beams, columns, or walls. Those few 
members may fail, and by chain reaction bring down the whole building. Stress 
concentration can also be created by vertical irregularity. The most serious 
condition of vertical irregularity occurs when a building has a soft or weak 
story, usually the ground floor, which is significantly weaker or more flexible 
than those above. This design creates a major stress concentration at the points 
of discontinuity, and in extreme cases may lead to collapse unless adequate 
design is provided for such points. Figure 2-10 shows some types of soft story 
design, and Figure 2-11 shows the collapse mechanism that is created.

The severe damage to Olive View Hospital in 1971, described in Section 2.3.1.1, 
was largely the result of a soft first story design. Such soft or weak stories 
are not permitted in current seismic designs. 

[Begin figure] Figure 2-10 is an illustration showing types of soft and weak 
story structures. Stress concentrations: the most serious conditions of vertical 
irregularity is the soft or weak story, in which one story, usually the first 
with taller, fewer columns, is significantly weaker or more flexible than the 
stories above. [End figure]

2.2.2.9 Torsional Forces

Irregularities in building configuration may produce torsional forces, which 
complicates the analysis of building resistance. Torsion is created by a lack of 
balance between the location of the resisting elements and the arrangement of 
the building mass. Engineers refer to this as eccentricity between the center of 
mass and the center of resistance, which tends to make the building rotate 
around the latter and create torsion within the resisting elements.

[Begin text box]
The IBC lists a dozen conditions of irregularity (six horizontal and six 
vertical) for which special design requirements apply. These special 
requirements either restrict the level of irregularity, amplify forces to 
account for it, or require more sophisticated analysis. A severe soft first 
story is specifically prohibited, although it is often encountered in existing 
buildings.
[End text box]

As explained in Section 2.2.1.1, the weight of the floors, walls, and roof 
contributes to the main lateral forces exerted on the structure through the 
center of mass, usually the geometric center of the floor plan. If the 
resistance provided by the building components is exerted through this same 
point (the center of resistance), then there is no torsion and balance is 
maintained. As shown in Figure 2-12, conditions of eccentricity  when the 
centers of mass and resistance are offset  produce torsional forces.

[Begin figure] 
Figure 2-12 is an illustration showing torsion. [End figure]

One building configuration that is most likely to produce torsion features re-
entrant corners (buildings shaped in plan like an L or a T, for example). 
The wings of such buildings tend to twist and result in torsion and stress 
concentration at the notch where the wings meet, also called a re-entrant 
corner (Figure 2-13).

[Begin figure] 
Figure 2-13 is an illustration showing the re-entrant corner building. [End 
figure]

Buildings that have large variations in their perimeter resistance on different 
facades of the building also tend to produce torsion. Such variations often 
occur when some facades have large areas of glazing while the others have solid 
walls.

Irregular configurations generally arise because of functional planning and 
programming requirements, or sometimes because of the architects or owners 
desire to create an original or striking architectural form.

Hospitals often have irregular and complicated configurations as a result of 
their functional complexity. Broadly speaking, smaller hospitals are usually 
planned in one or two stories with horizontal-planned layouts; large hospitals 
often have a vertical tower for patient rooms elevated above horizontally 
planned floors for the diagnostic, treatment, and administrative services. 
Emergency services are generally placed at the ground floor level, with direct 
access for emergency vehicles. However, new developments in hospital design (see 
Section 1.2.4) represent a radical departure from this traditional hospital 
morphology. The new designs are based on decentralization of functions, and the 
introduction of natural environment into hospital buildings. New hospital 
buildings have even more complex configurations consisting of fragmented blocks 
interspersed with courtyards and gardens, where different blocks frequently have 
not only different shapes, but different structural systems as well.

The structural design for a hospital, however, should still focus on reducing 
configuration irregularities to the greatest extent possible and ensuring direct 
load paths. Framing systems need careful design to provide the great variety of 
spatial types necessary without introducing localized irregularities (Figure 2-
14). 

[Begin 2-14] 
Figure 2-14is an illustration showing the complex footprint of a large community 
hospital. There are 2 shaded areas which represent open courtyards. [End figure]

2.2.3 Specifications for Performance-Based Seismic Design

Beginning with the 1989 Loma Prieta earthquake in the San Francisco Bay Area, 
the importance of the consequences of damage, other than endangering life 
safety, has been increasingly recognized, not only in hospitals and other 
critical facilities, but in all buildings. A major effort to develop guidelines 
for seismic rehabilitation of buildings was funded by FEMA in 1992, and 
published as FEMA 273 (1997). Subsequently, this guideline was improved and 
republished as FEMA 356 (2000), and in 2007 was made a standard by the American 
Society of Civil Engineers (ASCE 41).

2.2.3.1 Performance Levels

As a result of the high cost of retrofit and the growing interest in 
understanding the various performance levels of buildings in earthquakes, FEMA 
273 described a variety of seismic performances for both structural and 
nonstructural systems that could be targeted in design. These performances were 
summarized in a matrix (see Table 2-1) that allowed specification of a given 
performance level by combining the desired structural performance with a desired 
nonstructural performance. Four overall performances levels from that table were 
highlighted as discussed below. These performance levels were developed to be 
applicable to any building with any occupancy, as appropriate.

[Begin table] 
Table 2-1: Combinations of Structural and Nonstructural Seismic Performance

Nonstructural Performance Levels: N-A Operational
Structural Performance Levels and Ranges:
S-1 Immediate Occupancy: Operational 1A
S-2 Damage Control Range: 2-A
S-3 Life Safety: Not recommended
S-4 Limited Safety Range: Not recommended
S-5 Collapse Prevention: Not recommended
S-6 Not Considered: Not recommended

Nonstructural Performance Levels: N-B Immediate Occupancy
Structural Performance Levels and Ranges:
S-1 Immediate Occupancy: Immediate Occupancy 1B
S-2 Damage Control Range: 2-B
S-3 Life Safety: 3-B
S-4 Limited Safety Range: Not recommended
S-5 Collapse Prevention: Not recommended
S-6 Not Considered: Not recommended

Nonstructural Performance Levels: N-C Life Safety
Structural Performance Levels and Ranges:
S-1 Immediate Occupancy: 1-C
S-2 Damage Control Range: 2-C
S-3 Life Safety: Life Safety 3C
S-4 Limited Safety Range: 4-C
S-5 Collapse Prevention: 5-C
S-6 Not Considered: 6-C

Nonstructural Performance Levels: N-D Hazards Reduced
Structural Performance Levels and Ranges:
S-1 Immediate Occupancy: Not recommended
S-2 Damage Control Range: 2-D
S-3 Life Safety: 3-D
S-4 Limited Safety Range: 4-D
S-5 Collapse Prevention: 5-D
S-6 Not Considered: 6-D

Nonstructural Performance Levels: N-E Not Considered
Structural Performance Levels and Ranges:
S-1 Immediate Occupancy: Not recommended
S-2 Damage Control Range: Not recommended
S-3 Life Safety: Not recommended
S-4 Limited Safety Range: 4-E	
S-5 Collapse Prevention: Collapse Prevention 5E
S-6 Not Considered: No rehabilitation
[End table]

Operational Building Performance Level (1-A)
Buildings meeting this target building performance level are expected to sustain 
minimal or no damage to their structural and nonstructural components. The 
building would be able to continue its normal operations, possibly with only 
slight adjustments, mainly with respect to power, water, and other utilities 
that may need to be provided from emergency sources. 

Under low levels of earthquake ground motion, most hospitals should be able to 
meet or exceed this target building performance level. However, it would not be 
cost-effective to design buildings for this target building performance level 
under very rare, intense ground shaking, except for buildings that offer unique 
services or that contain exceptionally hazardous material.

Full functionality is normally considered difficult to achieve in the immediate 
aftermath of strong earthquake shaking. Offsite issues, such as staff 
availability and potential loss of utilities that are not under the control of 
the facility, may impair operations. In addition, relatively minor onsite damage 
to key components can significantly affect overall functionality. A single 
anchorage failure of the emergency generator, or a leak in one of the many 
pressurized water systems, can significantly disrupt hospital operations. 

Immediate Occupancy Building Performance Level (1-B)
Buildings meeting this target building performance level are expected to sustain 
minimal damage to their structural elements and only minor damage to their 
nonstructural components. While it would be safe to reoccupy a building meeting 
this target building performance level immediately following a major earthquake, 
nonstructural systems may not function, either because of the lack of electrical 
power or damage to fragile equipment. Therefore, although immediate occupancy is 
possible, it may be necessary to perform some cleanup and repair and await the 
restoration of utility services before the building can function in a normal 
mode. The risk of casualties at this target building performance level is very 
low.

Many building owners may wish to achieve this level of performance when the 
building is subjected to moderate earthquake ground motion. In addition, some 
owners may desire such performance for very important buildings under severe 
earthquake ground shaking. This level provides most of the protection obtained 
under the Operational Building Performance Level, without the cost of providing 
full standby utilities and performing rigorous seismic qualification of 
equipment performance.

Immediate Occupancy is more realistic than the Operational performance level for 
most buildings, and at a minimum, should be the goal of all new hospital 
buildings. However, since even the smallest disruption of non-structural systems 
may be too detrimental for continued operation of a hospital, the owners and 
designers should consider a higher level of protection for critical hospital 
functions. For instance, it is recommended that provisions be made for 
independent operation of critical utilities for a minimum of 4 days. Critical 
utilities usually include electric power; water; the sanitary sewer; and, 
depending on the local weather conditions, fuel for heating and cooling.

Life Safety Building Performance Level (3-C)

Buildings meeting this performance level may experience extensive damage to 
structural and nonstructural components. Repairs may be required before re-
occupancy of the building is allowed, although in some cases the repair may not 
be deemed cost-effective. The risk of casualties in buildings meeting this 
target building performance level is low.

This target building performance level entails somewhat more extensive damage 
than anticipated for new buildings that have been properly designed and 
constructed for seismic resistance. 

The Life Safety level should prevent significant casualties among able-bodied 
hospital occupants, but may not protect bed-ridden patients. In these 
circumstances, life safety level of protection is not appropriate for new 
hospitals.

Collapse Prevention Building Performance Level (5-E)
Although buildings meeting this target building performance level may pose a 
significant hazard to life safety resulting from failure of nonstructural 
components, significant loss of life may be avoided by preventing collapse of 
the entire building. Many buildings meeting this performance level may, however, 
be complete economic losses.

This level has been sometimes selected as the basis for mandatory seismic 
rehabilitation ordinances enacted by municipalities, as it results in mitigation 
of the most severe life-safety hazards at the lowest cost. Collapse Prevention 
is intended to prevent only the most egregious structural failures, and includes 
no consideration for continued occupancy and functionality of a hospital, the 
economics of damage repair, or damage to nonstructural components. 

2.2.3.2 New Developments in Performance-Based Design

Although developed for use in the process of seismic rehabilitation of older 
buildings, the aforementioned damage descriptions have filled a void and have 
become an interim standard for describing seismic performance of both new and 
existing buildings.

The goal of performance-based earthquake engineering has thus become the 
development of methods to predict the expected losses adequately, measured by 
the risk of casualties, the cost of damage repair, and the length of building 
downtime. These losses are to be calculated on a cumulative and probabilistic 
basis, allowing communication with stakeholders based on losses in a given 
scenario earthquake, the losses due to a probabilistically determined event, or 
the average annual losses over a given time period.

Since the publication of FEMA 273, performance-based earthquake engineering has 
continued to develop, particularly through research performed at the Pacific 
Earthquake Engineering Research Center, one of three major earthquake research 
centers funded by the National Science Foundation, and through the FEMA funded 
project, Next Generation Performance-Based Seismic Design Guidelines, FEMA 445 
(2006). When this work is completed, the global performance states used by FEMA 
356 will be redefined better to reflect current knowledge and to communicate the 
potential losses to stakeholders more effectively.

[Begin text box]
The example of California shows how earthquake damage affects legislation. The 
1971 San Fernando earthquake was particularly damaging to hospital buildings, 
most notably the Olive View Medical Center, a brand new facility that was 
damaged so badly that it was eventually demolished. Based on similar experiences 
with schools, the legislature passed the Hospital Seismic Safety Act (HSSA) in 
1972. The intent of the law was both to protect acute care patients and to 
provide post-earthquake medical care. The law was patterned after the Field Act 
covering schools in California, specifying the same State review agency, and 
stipulating design by specially experienced and approved Structural Engineers. 
It covered new buildings only and provided for a Building Safety Board of 
industry design professionals and facility experts, appointed by the Director of 
Health Services, to advise the State on implementation of requirements.

The law and regulations included four main considerations:
- Geologic hazard studies for sites

- Structural design forces in excess of those used for normal buildings 
(initially a K-factor of 3.0; later, an importance factor, I, of 1.5)

- Specific design requirements for nonstructural elements

- Strict review of design and inspection of construction

Surprisingly, only 23 years after the San Fernando earthquake, another damaging 
event occurred in almost the same spot. In January of 1994, the Northridge 
earthquake produced very large ground motions in the San Fernando Valley just 
north of Los Angeles. Just as the San Fernando event, the Northridge earthquake 
had a profound effect on hospital design in California. Although there were no 
failures in hospitals comparable to the Olive View disaster, several hospitals 
required evacuation as a result of failures of both structural and nonstructural 
systems. These high-profile evacuations once again put the hospital building 
inventory in the spotlight. Analysis and comparison of the performance of 
buildings in Northridge built before and after the HSSA clearly indicated its 
effectiveness. This analysis also indicated that further improvements were 
needed in the performance of nonstructural systems.

Senate Bill 1953, which introduced a plan to bring all pre-Act hospital 
buildings into compliance with the HSSA by the year 2030, was signed into law by 
the governor of California in September, 1994. Standards and regulations needed 
to implement the law included:

- Definition of structural vulnerabilities and evaluation standards

- Definition of nonstructural vulnerabilities and evaluation standards

- Standards for retrofit

- Building evaluations and facility compliance plans shall be submitted to the 
Office of Statewide Health Planning and Development (OSHPD) by January 1, 2001; 
Facility owners, 60 days after approval by OSHPD, shall submit building 
performance categories to local emergency service agencies and use the 
performance information to improve emergency training, response, and recovery 
plans
- Hospital buildings with a high risk of collapse cannot be used for acute care 
purposes after January 1, 2008. These buildings must be retrofit (to a life 
safe performance), demolished, or abandoned for acute care use by that date
- High-risk nonstructural systems (pre- and post-Act) shall be mitigated in 
accordance with priorities and timelines to be set in regulation by OSHPD, in 
consultation with the Hospital Building Safety Board
- All facilities shall be in substantial compliance with the intent of the HSSA 
by January 1, 2030
[End text box]




2.3 EARTHQUAKE DAMAGE TO HOSPITALS

Although earthquakes damage most manmade structures in similar ways, to 
understand the true consequences of damage to buildings with special occupancies 
and functions requires a much more detailed and accurate damage description than 
may be needed for other buildings. The effects of earthquake damage on hospital 
operations and the safety of occupants have been described below based on the 
experiences of hospitals in the United States and around the world.

Historically, buildings have been engineered to provide adequate life safety to 
occupants and passers-by from earthquake hazards. For most buildings, life 
safety is primarily threatened by building collapse or the debris falling into 
the street and neighboring buildings. A higher level of performance is required 
to address the life safety issues of hospitals, since patients often have 
limited mobility and are dependant on caregivers or specialized medical 
equipment. 

Figure 2-15 shows typical building components and systems present in hospital 
facilities. The structural elements consist of the foundations, columns, beams 
and slabs, walls, and braces that hold the building up against vertical gravity 
forces and horizontal wind and earthquake forces. The nonstructural elements 
include building service systems, such as electricity and lighting, heating and 
cooling, plumbing, and interior architectural systems, such as ceilings, floors, 
partitions, and other interior components. The building envelope includes the 
systems that separate the interior spaces from the exterior, both structural and 
nonstructural. It includes exterior walls and cladding, roof systems, doors and 
windows, and floors or slabs that separate the building interior from the 
ground. Contents and equipment are completely dependent on the type of occupancy 
and the function of the space, and range from items such as furniture 
encountered in a lobby or a waiting room, to highly technical equipment commonly 
present in treatment rooms. In addition, laboratories, pharmacies, bulk storage 
areas, and large central energy plants have highly specialized and frequently 
very sensitive equipment.

[Begin figure]
Figure 2-15A is an illustration showing the structural and nonstructural 
elements of a buildings structure. [End figure]

[Begin figure]
Figure 2-15B is an illustration showing the structural and nonstructural 
elements of a buildings nonstructural components. These include roofing and 
insulation, air conditioning units, ducts, lighting, windows partitions, 
exterior wall panels, ceiling furniture, and sprinkler piping. [End figure]

In general, both the building service systems and the contents of hospitals rank 
among the most complex and expensive of any building type. Furthermore, both the 
structural system and most of the nonstructural systems are required to perform 
without interruption after an earthquake to enable adequate functionality. 

2.3.1 Types of Structural Damage

When the ground shakes in an earthquake, the shaking is transferred to the 
building, potentially causing structural damage. The damage can consist of 
cracks in structural walls, bent or broken braces, or damage to columns and 
beams. Damage can range from minor (a few cracks), to major (parts of the 
structure rendered ineffective and potentially unsafe), to complete collapse. 
See Figures 2-16, 2-17, 2-18, and 2-19 for examples of structural damage.

[Begin figures]
Figure 2-16 is a photo showing how this concrete building suffered severe damage 
to the columns at the second floor level. It was deemed unsafe by the local 
jurisdiction and later demolished.

Figure 2-17 is a photo showing a steel frame building with a post-earthquake 
lean to the right, seen particularly at the first floor. Severe damage was 
found in its beam column joints and it was later demolished.

Figure 2-18 is a photo showing severe damage to a poorly reinforced masonry wall 
on a steam plant.

Figure 2-19 is a photo showing damage to an exterior concrete wall. This 
hospital building was evacuated. 
[End figures]

2.3.1.1 The Case of the Olive View Medical Center

The Olive View Hospital in the northern San Fernando Valley, owned by Los 
Angeles County in Southern California, was severely damaged on February 9, 1971, 
when the San Fernando earthquake damaged the almost-new facility so severely 
that it was later demolished. Over 500 patients were evacuated immediately after 
this event. 

The 850-bed Olive View Hospital campus comprised of over 30 buildings of 
various ages, but most notably featured a complex of buildings completed in 
1970, only months before the 1971 San Fernando earthquake. These new buildings 
included the five-story Medical Care Facility, the two-story Psychiatric Unit, 
the Heat and Refrigeration Plant, and several other smaller ancillary buildings 
such as a warehouse, assembly building, walkway canopy, and ambulance canopy. 
The 1970 buildings were all made of reinforced concrete and designed under the 
1965 Los Angeles Building Code, which included seismic provisions. However, 
neither of these buildings had any special seismic protection features. In fact, 
the poor performance of this facility was one of the prime reasons for passage 
of Californias Hospital Seismic Safety Act (HSSA). The shaking experienced in 
the 1971 San Fernando earthquake was extreme; however, structural performance of 
these buildings was worse than the engineering community had expected. 
Subsequent investigations indicated that the buildings technically met the 
requirements of the code, but included features that made them particularly 
vulnerable to earthquake damage. Seismic codes were subsequently refined to 
prevent this type of vulnerability in future buildings.

The damage to Olive View Hospital buildings was nearly catastrophic. The first 
story of the medical treatment and care unit was over 15 inches out of plumb and 
near collapse (Figure 2-20). Three of the four exterior stair towers pulled away 
from the main building or collapsed completely, rendering them useless for 
egress (Figure 2-21). The Ambulance Canopy collapsed onto the parked ambulances 
and destroyed them. The first story of the Psychiatric Unit collapsed, but all 
the occupants were on the second floor at the time.

Almost immediately after the event, the patients in the Psychiatric Unit began 
assembling in a parking lot adjacent to their facility. The need to evacuate was 
obvious, and the second floor wards were only feet from the ground after the 
first floor collapse (see Figure 2-22). Controlling and tracking these patients 
was nearly impossible, particularly in the first few hours. Within 5 hours, 
evacuation was underway in the main building using interior stairwells. The 
building had no power and therefore no elevators or lights. The nurses evacuated 
their own units, ambulatory patients first, and, when sufficient assistance was 
available, non-ambulatory patients. By that time, a network of ambulances and 
helicopters had been set up for transfer to other facilities (Arnold, 1983; 
Lew, 1971; NOAA, 1973).

Subsequent analysis of the effects of this earthquake on the hospital noted, as 
particularly troublesome, the lack of functioning communications, either 
internal or external, the lack of an effective evacuation plan or identified 
assembly area, and the lack of any control or tracking of medical records. 

[Begin figures] 
Figure 2-20 is an aerial photo of the 1971 Olive View Hospital. Source NOAA 
1973.

Figure 2-21 is a photo showing the collapsed stair tower in main building of 
Olive View Hospital.

Figure 2-22 is a photo showing the completely collapsed first level (not 
visible) of Psychiatric Unit. 
[End figures]

2.3.2 Nonstructural Damage

When the ground shakes the structure, the structure shakes everything that is in 
it or on it, including the building envelope and components of the interior 
nonstructural systems. This shaking can damage most components directly. 
Indirect damage, resulting from structural deformation between floors, can cause 
damage to all the systems connected to these structural components.

Damage to architectural systems consists of broken windows and cracked exterior 
walls and interior partitions. In extreme cases, exterior walls and partitions 
topple completely. Ceilings are also vulnerable to damage and can break into 
small pieces or fall to the floor (see Figure 2-23).

Damage to the building service systems can consist of sliding or overturning of 
equipment like boilers, generators, and fans, or swaying and possible fracture 
of mechanical ducts, pipes, and electrical conduit (see Figures 2-24, 2-25, and 
2-26).

[Begin figures] 
Figure 2-23 is a photo showing a damaged exit corridor  dark and barely 
passable 

Figure 2-24 is a photo showing vibration isolation bearing assemblies on 
mechanical equipment collapsed due to seismic shaking  such movement breaks 
pipe or electrical connections to the equipment

Figure 2-25 is a photo showing a heavy transformer that moved several feet, 
breaking all connections

Figure 2-26 is a photo showing a large chiller almost tipped over.

Figure 2-27 is a photo showing damaged radiology equipment that not only will 
not function, but has become a life-safety risk. 
[end figures]

Because of the wide variation of contents and equipment in a typical hospital, 
the type of damage experienced by these systems varies widely. For example, 
medical equipment, such as operating tables and lights, radiation and x-ray 
units, sterilizers, and patient monitors, is often heavy and not well anchored 
to the structure (see Figure 2-27). Offices and storage rooms, such as the areas 
used to store critical supplies, medicine, medical records, chemicals, and fuel, 
can also be severely damaged by shaking (see Figures 2-28, 2-29, and 2-30).

[Begin figures]
Figure 2-28 is a photo showing chaos in a storage area similar to central 
storage or medical records.

Figure 2-29 is a photo showing jumbled contents of a typical office

Figure 2-30 is a photo showing overturned tank similar to medical gas storage
[End figures]

2.3.2.1 The Case of New Olive View Medical Center

Nearly 15 years after the 1971 earthquake event that destroyed the Olive View 
Medical Center (see Section 2.3.1.1), a new hospital was opened on the same site 
in 1986 (see Figure 2-31). Built even stronger than required under the HSSA of 
1972, the building has no basement and features a seismic system of concrete 
shear walls and steel plate shear panels. The building was also equipped with 
instruments to record its response in future earthquakes. 

[Begin figure]
Figure 2-31 is an Aerial view of new Olive View Hospital (1986) [end figure] 

Early in the morning of February 17, 1994, a Magnitude 6.7 earthquake occurred 
on a little known fault not generally considered dangerous, located near 
Northridge, about 10 miles from the hospital. The recorders captured 
exceptionally high accelerations of 0.82 g at the first floor and 1.7 g at the 
roof. The structure suffered little or no structural damage, but its stiffness 
and strength contributed to the transfer of unprecedented accelerations through 
the building, in some cases overwhelming the seismic anchorage and bracing 
provided for the buildings nonstructural systems. Some of these components and 
systems were not considered sufficiently vulnerable to require special bracing.

Damage included the following (see Figures 2-25, 2-26, and 2-27):

- Shifting, and in some cases, failure, of anchorages of equipment at the roof 
level, where accelerations were the highest. This movement broke one or more 
chiller water lines, causing flooding in the top floors (see Figure 2-32).

[Begin figure]
Figure 2-32 is a photo showing anchor bolts stretched by large seismic 
accelerations at roof level [end figure] 

- Excessive movement and failure of wall-mounted television brackets, causing 
some television units to fall.

- Extensive damage to suspended panelized ceilings, some exacerbated by leaks 
from water pipes from above.

- Excessive movement and interaction between gypsum board and other fire-rated 
ceilings and sprinkler lines, causing additional leaks.

- Movement at the copper tube reheat coils in the ceiling spaces, almost 
universally at the third through the sixth floor, causing leaks (see Figures 2-
33 and 2-34).

[Begin figures] 
Figure 2-33 is a photo showing damage to ceiling and fixtures from sprinkler 
breaks
Figure 2-34 is a photo showing detail of water damage to ceiling 
[end figures]

- Damage to some equipment anchorage in the Central Plant and at the bulk oxygen 
tank.

- Damage to elevators, seven of which were temporarily out of service. Four had 
sustained severe damage as a result of derailed and bent counterweight frames. 

Right after the earthquake event, administrators planned a partial evacuation of 
79 patients, but by the afternoon, they decided to transfer all 377 patients to 
other facilities, despite the dangers associated with such a move. The 
evacuation was prompted primarily by water damage and lasted 41 hours (EERI, 
1995; LACDHS, 1994; URS, 1996).

Despite vastly improved structural performance and compliance with the 
requirements for anchorage and bracing of nonstructural components and systems 
compared to the conditions in 1971, the hospitals operations were severely 
compromised. It was not ready to accept local casualties, but actually increased 
the load of neighboring facilities by requiring evacuation. The unexpectedly 
poor performance was caused by extraordinary ground motions, probably made more 
damaging to nonstructural systems and contents by the very stiff and strong 
structure of the hospital.

2.3.2.2 The Case of Kona Community Hospital, Hawaii 

The Kona Community Hospital (KCH) is located in Kealakekua, Kona, on the central 
west coast of the Big Island of Hawaii. It was originally a county hospital but 
became part of the State-owned Hawaii Health Systems Corporation in 1996. KCH is 
a full service medical center and is the primary health care facility serving 
West Hawaii. The facility has 33 acute medical-surgical beds, a 9-bed intensive 
care unit, 7 obstetric beds, an 11-bed behavioral health unit, and a 34-bed 
skilled nursing/long term care wing.

The KCH campus includes several buildings, but the primary medical facility 
occupies a three-story L-shaped building that consists of the original 60,500-
square-foot block built in 1972, and an 18,300-square foot addition built in 
1989. Both structures are concrete, rectangular in plan, and each forms one leg 
of the L shape. The site slopes east to west creating two stories above grade 
and one basement floor on the east, and three stories above grade on the west 
face. The lateral force (wind and earthquake) resisting system of the original 
building consists of concrete pier shear walls that are part of the exterior 
wall and concrete walls around the elevators and stairs. The lateral force 
resisting system of the addition is a ductile concrete frame, which consists of 
the beams and columns rigidly tied together in a manner that resists lateral 
motion. The addition is notable in that the two bays of the western end are open 
at the ground floor and serve as a drive-through to the back of the campus and 
as an ambulance entrance. 

Seismic Characteristics of the Facility

A technical evaluation of the facility, performed in 1993 by the Hawaii State 
Earthquake Advisory Board, identified several seismic deficiencies. It was found 
that the layout of the lateral-force-resisting shear walls in the original 1972 
building and the outdated pattern of column reinforcement were of the type that 
previously contributed to unacceptable levels of damage in similar buildings. 
Conditions that presented potential seismic deficiencies were also found in the 
1989 addition, including:

- The eccentric location of the stair and elevator core, which could potentially 
create torsional response 
- Inadequate connection of the floor slabs to the core, which could cause 
moderate damage 
- The potential for nonstructural plaster cracks in the upper floors,
- The potential for local damage at the connection between new and original 
wings during shaking 

As part of the evaluation, the torsion issue (related to the stair and elevator) 
was checked and found not to represent a significant problem. No specific 
recommendations related to the other problems were included in the evaluation. 
The structural evaluation concluded with a recommendation to retain a local 
structural engineer to review the seismic adequacy of KCH in more detail. The 
evaluation also covered the seismic protection of nonstructural systems and 
equipment, but included no specific recommendations for KCH.

The evaluation categorized nonstructural components and systems as:

- Systems and elements which are essential to hospital operations and without 
which the hospital cannot function (Essential) 

- Nonessential elements whose failure could compromise hospital operations 
(Nonessential) 

In fact, when considering seismic preparedness of hospital facilities, there is 
little consensus about the types of nonstructural systems that should be 
considered essential. These classifications vary from facility to facility and 
are closely tied to elements of the emergency response plan. For example, 
unbraced, suspended panelized ceiling systems typically used in hospitals on the 
island were noted as a deficiency, but consistent with standard seismic 
evaluation procedures for hospitals, these systems were classified as 
nonessential. However, as described below, damage to these ceilings proved 
critical when a real event struck.

Most of the larger equipment categorized as essential in the evaluation, 
including the emergency generator, the bulk oxygen tank, the chiller, and the 
rooftop cooling tower were seismically anchored and continued to function during 
the earthquake.

Damage

The Hawaii Earthquake of October 15, 2006, had a magnitude 6.7 and was centered 
about 35 miles north of the KCH. It was followed by a second shock of magnitude 
6.0. The shaking caused moderate damage over much of the Big Island and was felt 
as far away as Oahu. Shaking on the island of Hawaii, as recorded on several 
instruments installed by the USGS, featured relatively high accelerations, but 
the energy was restricted to very high frequency (short period), which proved 
damaging to stiff, brittle structures. Several unreinforced masonry buildings 
suffered severe damage, many ungrouted stone masonry fences and walls partially 
collapsed, and landslides and rockslides were common, which is consistent with 
this kind of motion. 

The Special Services Building at KCH (seen in Figure 2-35 behind the small 
single-story building on the left) contained such an instrument. The response 
spectrum for one component of motion is shown in Figure 2-36 in blue. Note the 
rapid decline of spectral acceleration values for very short periods, much less 
than 0.5 seconds. The orange curve shows a spectral shape that might be expected 
in association with such high ground accelerations, and is included in building 
codes. High values of spectral acceleration between the periods of 0.5 seconds 
and 2.0 seconds, as shown in this standard curve, are usually associated with 
much greater building damage. 

[Begin figures]
Figure 2-35 is a photo showing Kona Community Hospital. Addition (1989) 
supported on isolated columns in the foreground. The original building (1972) is 
in the left background. 

Figure 2-36 is a graph showing response spectra for one of the orthogonal 
components recorded at the site of the KCH. The blue line is for the recorded 
motion. The orange line represents the spectral shape more commonly expected and 
contained in building codes.(Graph courtesy of www.Cosmos-eg.org) 
[end figures]

The high acceleration motion caused the unbraced, suspended panelized ceilings 
(see Figure 2-37), found almost everywhere at KCH, to strike partitions that 
demarcated rooms and corridors. The partitions were constructed of steel studs 
and gypsum board, and the studs run from the structural floor to the underside 
of the structure above, making them very strong and stiff. The impact of the 
panelized ceilings caused the lightweight support tees either to buckle or pull 
off of a typical perimeter trim angle (Figure 2-38). In the absence of vertical 
support wire, the tees collapsed, allowing the ceiling tiles to fall. Many of 
the florescent light fixtures, also supported on the tees, became dangerously 
unstable, though few fell to the floor. This type of damage was concentrated at 
the perimeter of rooms, adjacent to the partition walls, but it was not 
completely limited to these locations (see Figures 2-39). When ceiling tiles 
became dislodged, decades of accumulated dust on the top of the tiles came down, 
adding to the general disarray and threatening the health of patients and other 
occupants. 

[Begin figures]
Figure 2-37 is an illustration showing a typical suspended panelized ceiling 
system showing seismic bracing (according to the 1993 seismic evaluation report, 
this system was not used in the hospitals reviewed at that time

Figure 2-38 is a photo showing typical damage at the perimeter of a room from 
loss of support from the partition-mounted perimeter angles to the ceiling 
system tees or from contact with the ceiling system and the partitions.

Figure 2-39 is a photo showing ceiling damage in the operating room. The round 
operating lights on the right were not damaged. 
[end figures]

Almost simultaneously with the first shock, the power went out. The emergency 
generator was seismically protected and provided power for the emergency 
circuits. Eight minutes after the main shock, about the time some semblance of 
order was being restored, the second shock hit. With equipment and contents as 
well as ceiling tiles and metal tees littering the floor or hanging precariously 
over patients beds, a decision was made to evacuate the most disrupted areas.

At the time of the earthquake KCH had 69 patients, including 31 in the long-term 
care unit. These 31 long-term care patients were taken to a local hotel; 27 
patients were discharged; 5 were airlifted to an acute care facility in Hilo, 
and one was transported to a local long-term care facility. The remaining five 
patients were more difficult to move and were placed in usable rooms in the 
obstetrics or the intensive care unit (ICU) on site.

The potential torsional response of the building addition, identified in the 
1993 evaluation, proved prophetic, as the column-supported west end attempted to 
rotate around the stiffly supported east end. As shown in Figure 2-40, the two 
beam connections tending to restrain the motion spalled. Similarly, in the 
partially enclosed penthouse, the embedded connection of a steel beam spanning 
between two exterior concrete walls pulled out due to a stiffness 
incompatibility. This damage was not considered serious enough for the structure 
and did not affect the occupancy status.

[Begin figure]
Figure 2-40 is two photos showing spalling at beam connections. [end figure]

Exterior and interior nonstructural plaster or stucco walls had many cracks, 
especially around some door frames. This damage was costly, but did not affect 
operations.

Emergency generators and medical gas storage were seismically anchored and 
survived the tremor undamaged. The communications were disrupted for the first 
hour or so, because the telephone main switching equipment, which was not 
anchored, failed. The radio-repeater mast on the roof fell over and dislodged 
the coaxial cable, limiting the use of that system. The hospital has 
subsequently decided that their radio system does not have sufficient channels 
for emergency use and intends to upgrade the system. Ham radio was also 
available on the site but was not used. 

The hydraulic elevators, which are not as susceptible to damage as the traction 
elevators used in taller buildings, sustained no major damage but were not 
functional as a result of power outage. Elevators can be very valuable after 
earthquakes for moving bed-ridden patients, provided special seismic anchorage 
and controls are installed and emergency power is available. The pressurized 
water systems (including sprinklers, domestic, and chilled water), considered by 
many the most likely to break or leak and disrupt operations, suffered no 
damage.

The experience of KCH highlighted the vulnerability of unbraced suspended 
panelized ceilings, which are often given a low retrofit priority because they 
are not considered a serious life safety hazard. It was also thought that the 
benefits of bracing do not warrant the extreme disruption that such a retrofit 
usually causes for hospital operations. It is very likely that lessons from Kona 
Community Hospitals experience will help change this view.

2.3.3 Consequences of Building Damage 

The uninterrupted operation of hospitals is crucial in the aftermath of an 
earthquake, because of a potentially large number of casualties. Damage to these 
facilities and a possible need for an evacuation not only hampers the emergency 
response but can also compound the disaster by adding casualties. The most 
obvious risk to life safety is serious structural failure of a hospital, similar 
to the experience of the original Olive View hospital. In the aftermath of an 
earthquake the local building authority typically determines which buildings are 
unsafe for use based on the level of damage. For this purpose, a simple 
tagging procedure has been developed in California that uses colored placards 
or tags affixed to buildings that show that the building has been inspected 
and indicate the level of safety. The evacuation is inevitable when the hospital 
buildings are red tagged, i.e. when the building is in imminent danger of 
collapse in an aftershock. In such circumstances, a hospital becomes unavailable 
for emergency services and the staff can only provide medical care in parking 
lots or other ancillary facilities, as has happened in the past.

[Begin text box]
TAGGING
A red tag indicates UNSAFE: Extreme hazard, may collapse. Imminent danger of 
collapse from an aftershock. Unsafe for occupancy or entry, except by 
authorities.
A yellow tag indicates LIMITED ENTRY: Dangerous condition believed to be 
present. Entry by owner permitted only for emergency purposes and only at own 
risk. No usage on a continuous basis. Entry by public not permitted. Possible 
major aftershock hazard.
A green tag indicates INSPECTED: No apparent hazard found, although repairs may 
be required. Original lateral load capacity not significantly decreased. No 
restriction on use or occupancy.
[End text box]

Even in cases where hospitals have avoided major damage, their operations may be 
sufficiently disrupted to require complete evacuation, which can be very 
dangerous for many patients. Failures in nonstructural systems, such as broken 
pipes that cause extensive flooding, failed emergency generators, lack of water, 
or general chaos created by contents that have been thrown about have all 
created conditions that have forced hospital administrators or local 
jurisdictions to order an evacuation. Minor nonstructural damage, especially if 
essential equipment or other contents are affected, can still cause considerable 
disruption in hospital operation, even if global evacuation is not deemed 
necessary.

Finally, almost all hospitals have financial constraints. The cost of repairs 
and/or the partial loss of capacity will affect the financial well-being of any 
facility and must be considered as a significant potential consequence of 
earthquake damage.

2.3.4 Seismic Vulnerability of Hospitals 

Seismic vulnerability of a hospital facility is a measure of the damage a 
building is likely to experience when subjected to ground shaking of a specified 
intensity. The response of a structure to ground shaking is very complex and 
depends on a number of interrelated parameters that are often very difficult, if 
not impossible, to predict precisely. These include: the exact character of the 
ground shaking the building will experience; the extent to which the structure 
will respond to the ground shaking; the strength of the materials in the 
building; the quality of construction, the condition of individual structural 
elements and of the whole structure; the interaction between structural and 
nonstructural elements; and the live load in the building at the time of the 
earthquake.

Frequently, seismic activity causes insignificant damage to the structure of a 
hospital, yet its operations are impaired or disrupted because of damage to 
nonstructural elements. Even a low-magnitude seismic event can affect vital 
functions of a hospital and cause its evacuation and closure. This was evident 
in some recent earthquakes, whereby structures designed in accordance with 
modern seismic resistance criteria performed well, while the poor performance of 
the nonstructural elements caused serious disruption of hospital operations. 

A variety of methods for assessing seismic vulnerability of buildings exist that 
differ in cost and precision. The type of method to be used depends on the 
objective of the assessment and the availability of data and appropriate 
technology. Typically, quicker and less sophisticated methods, like the commonly 
used rapid visual screening, are used for larger areas and large number of 
buildings. They often form the first phase of a multiphase procedure for 
identifying hazardous buildings, which must then be analyzed in more detail to 
determine upgrading strategies. Detailed assessment procedures use computer 
models and various forms of engineering analysis that are time consuming and 
expensive and require a high degree of analytical expertise to obtain reliable 
results. Consequently, they are used for detailed verification of the safety of 
structural and nonstructural elements, including proposals for specific 
mitigation measures.

A simple preliminary vulnerability assessment of existing hospitals can be 
performed using the results of the historical study of hospital performance in a 
variety of seismic events. This method is described below in greater detail.

2.3.4.1 Seismic Vulnerability of Hospitals Based on Historical Performance in 
California

A recently completed study on Seismic Vulnerability of Hospitals Based on 
Historical Performance in California, (Holmes and Burkett, 2006) analyzed the 
historical record of losses to hospitals damaged in major California earthquakes 
since 1971. The data base contained two hundred eighteen cases, each 
representing a hospital (potentially one or more buildings) that experienced 
earthquake ground shaking in the earthquakes of San Fernando (1971), Imperial 
Valley (1979), Coalinga (1983), Whittier (1987), Loma Prieta (1989), Sierra 
Madre (1991), and Northridge (1994). Damage reports varied from brief, one-
paragraph summaries to elaborate narratives of the damage patterns and the 
consequences. Evacuations or shut-downs of facilities were always noted. These 
descriptions were used to categorize hospital damage into one of the structural 
and nonstructural performance categories shown in Table 2-2.

[Begin table]
Table 2-2: The description of performance categories in terms of structural and 
nonstructural building damage

Performance category (damage level): None

Performance category (damage level): Minor
Type of Structural Damage: Minor structural damage (light concrete cracking, 
etc.)
Type of Nonstructural damage: Minor damage to nonstructural components or 
systems (plaster cracking, ceiling damage, some equipment shaken off supports)

Performance category (damage level): Affecting hospital operations
Type of Structural Damage: Damage requiring immediate evacuation due to 
dangerous conditions or concern for collapse in an aftershock
Type of Nonstructural damage: Nonstructural damage that prevents full 
functioning of the hospital (loss of emergency generator, local pipe breaks and 
causes flooding, computer system down)

Performance category (damage level): At least temporary closure
Type of Structural Damage: Closure could be temporary or permanent
Type of Nonstructural damage: Temporary Closure based on major nonstructural 
damage (long-term power or water outage, extensive ceiling and light fixture 
damage, major flooding)
[End table]

The study related the recorded levels of damage experienced by hospitals and 
ground motion data for each seismic event, determined on the basis of recorded 
ground motion at the site during the earthquake and USGS data. The intensity of 
ground motion was represented by spectral acceleration at short periods (SDS), 
measured in units of the acceleration of gravity g in order to match building 
code information that can be obtained locally (see Section 2.2.2.1). In this 
study, the spectral acceleration at short periods for each case in the 
historical record was labeled SHS, which stands for historical short period 
spectral acceleration. By matching spectral acceleration data with performance 
categories, a relationship was established between the damage (and the 
consequences of damage) and the ground motion intensity that caused it. All 
buildings were divided into two groups according to the level and quality of 
seismic design and construction. The adoption of the HSSA in 1972 was used as a 
divide between pre-Act buildings and post-Act buildings. The results of this 
study presented the differences in performance of hospital buildings in 
California in graphic form on Figures 2-41 for pre-Act buildings and in Figure 
2-42 for post-Act buildings. 

The measure of ground motion intensity is different in the two figures. For pre-
Act buildings, SHS represents accelerations recorded at the time, while post-Act 
building performance was categorized according to ground motion expressed as the 
percentage of SDS typically used in California for seismic design in the post-
Act period. Post-Act buildings in the database were designed for the higher 
seismic zones of California, typically with an SDS of about 1.0. To use this 
data to estimate potential damage to newer buildings in other parts of the 
country that have incorporated thorough seismic design with other values of SDS, 
it is necessary to normalize the data to an SDS of 1.0. The ground motion in 
Figure 2-42 is thus represented as a percentage of the SDS used to design the 
building. SHS = 0.250.50 of SDS shows expected damage to a relatively new 
building when it is shaken with an intensity of 25 to 50 percent of its code 
design, as measured by SDS. Since damage occurs even at levels considerably 
below the code earthquake, the data is still very useful for planning purposes. 
The probability of occurrence of shaking different from the code level can be 
estimated by local seismologists or engineers.

This study, based on past damages, provided a clearer picture of the 
vulnerability of hospitals and established a benchmark for vulnerability 
assessments of all the existing hospitals. Among other things, the analysis 
indicated that the threshold for potentially significant seismic damage 
coincided with the current, lower-bound ground motion intensity requiring 
seismic design for new buildings (SDS greater than 0.167 g). The pre-Act charts 
indicated a slight possibility of significant structural damage, but a strong 
possibility of nonstructural damage at low shaking levels. It should be noted 
however, that structural damage requiring building closure has been recorded 
even at the SDS level just above 0.4 g. The analysis of the post-Act data 
indicated that hospital buildings built in accordance with the 2000 IBC (or 
later edition) are unlikely to suffer serious structural damage for events up 
to, and including, the intensity of the code earthquake. However, as previously 
discussed, new hospital buildings may not perform as well as indicated on the 
post-Act charts, since most regions of the country do not have as strict design 
and construction codes and code enforcement as California. Nonstructural damage, 
which can reduce hospital effectiveness or even cause evacuation, remains a 
significant vulnerability, even in new buildings.

2.3.4.2 Vulnerability Assessment of Hospital Buildings

Although the above-mentioned study was based on data from California, where the 
ground motions have slightly different characteristics than in other parts of 
the country, the vulnerability to damage for certain building types at given 
levels of ground motion is comparable to any location. Prior to obtaining the 
detailed site-specific seismic evaluations, the expected damage from a given 
ground motion can be estimated on the basis of historical data. The results of 
the study, therefore, can be used effectively to make preliminary assessments of 
the vulnerability of hospitals in any seismic region of the country. While this 
type of analysis will not take the place of a formal seismic building evaluation 
performed by experienced design professionals, it can be very helpful in raising 
the awareness of potential earthquake risks, in determining whether a more 
detailed study of vulnerability is justified, and whether to incorporate more 
realistic damage projections in a disaster plan or emergency exercise.

For example, a hypothetical hospital near Charleston, SC, may determine from the 
local building code that the seismic spectral acceleration value for short 
periods at the site is 0.8 g. If one or more of their buildings are 20 or more 
years old and were designed without seismic provisions or with out-of-date 
seismic provisions, the pre-Act columns of Figure 2-41 should be consulted. The 
chart on Figure 2-41 for the range of SDS between 0.6-0.8 g shows that, unless 
building-specific studies are done to prove otherwise, it should be assumed that 
a code earthquake will cause sufficient damage to hinder the full operations 
(about a 33 percent chance) or require closure of a building (about a 13 percent 
chance). Perhaps more importantly, the right column of Figure 2-41 indicates a 
high probability that hospital operations will be interrupted by nonstructural 
damage. In fact, for such a facility, even very low shaking levels of SDS 0.2 g 
to 0.4 g could be expected to cause nonstructural damage resulting in 
significant disruption of hospital operations.

In contrast, a brand new hospital in northern Utah, on a site with SDS of about 
0.7 g, is unlikely to suffer significant structural damage (as shown on the 
post-Act charts, left column of Figure 2-42). However, if such a hospital was 
not constructed according to the best design and construction standards, it can 
be expected to suffer a more significant nonstructural damage than the post-Act 
data shown in Figure 2-42. A prudent disaster plan would in such a case consider 
the possibility that nonstructural damage could cause a temporary closure.

2.3.4.3 Comparability of Hospital Buildings

The structural performance of hospital buildings built anywhere in the country 
without any seismic design provisions is most likely comparable to the 
performance of pre-Act buildings as shown on Figure 2-41. All buildings in the 
pre-Act group were either constructed with no seismic design, or with the 
archaic seismic design rules of the 1960s or earlier. Most of these buildings 
were constructed with concrete, steel, reinforced masonry, or wood construction. 
Unreinforced masonry buildings are rare in California because most of these 
buildings have either been abandoned or retrofitted. However, it should be 
assumed that older buildings of unreinforced masonry bearing wall construction, 
that are still common in other parts of the country, would perform at the low 
end of the ranges recorded for pre-Act buildings. 

Buildings with seismic designs completed in the 1970s and 1980s can be expected 
to perform somewhere between pre- and post-Act levels, but probably closer to 
the pre-Act data. Buildings classified as post-Act are exceptionally strong, 
because the designs were thoroughly checked and the construction monitored in 
detail. Due to the State-of-California-mandated scrutiny given design and 
construction, there are few hospital buildings outside of that area that would 
be equivalent to the post-Act category. However, the structural performance of 
hospitals built since the early 1990s that incorporated full seismic design, 
including an importance factor of 1.5, can be compared to the post-Act category. 

The vulnerability assessment of existing hospitals with respect to nonstructural 
building components is different from the assessment of potential structural 
damage. Unless a significant emphasis was placed on the design and installation 
of nonstructural anchorage and bracing, and unless the construction was 
monitored and inspected regularly, the potential for damage to ceilings, 
partitions, pipes, ducts, equipment, and other nonstructural systems should be 
estimated using the pre-Act column and charts. Since it is unlikely that 
nonstructural systems have been adequately protected in areas outside of 
California, it is recommended to assume that substantial damage to these systems 
would be a certainty in moderate to high levels of shaking. Even with the 
extraordinary measures taken in California to assure thorough seismic protection 
of nonstructural systems, the level of nonstructural damage recorded indicates 
that the potential disruption of hospital operations can happen at shaking of 
about 50 percent SDS. The shaking above 80 percent SDS would most likely result 
in nonstructural damage that would require immediate closure and total 
evacuation of the hospital.

This type of vulnerability analysis should be used for preliminary assessments 
or for the purpose of awareness training or emergency planning. It cannot 
replace a formal seismic building evaluation performed by experienced design 
professionals. The type and the extent of seismic risk exposure for hospitals 
can only be identified by expert analysis.

[Begin figures] 
Figure 2-41: Charts showing performance categories for pre-Act buildings for 
various ground motions 

Figure 2-42: Charts showing performance categories for post-Act buildings for 
various ground motions
[end figure]



2.4 RISK REDUCTION MEASURES

This section outlines some of the basic approaches and techniques of mitigating 
earthquake hazards. Since the theory and practice of seismic design are well 
established and have largely been incorporated into the current model building 
codes, this section starts with the review of basic steps in the process of 
planning and design of hospitals. It also highlights some of the well-
established seismic design and construction techniques and specialized building 
systems designed specifically to address the seismic forces. Although the 
general principles of design are similar for new and existing hospitals, this 
section highlights the differences in code requirements and overall project 
delivery processes that reflect the opportunities and constraints of seismic 
design for new and existing buildings. 

2.4.1 Site Selection Basics

The first priority for owners of existing hospitals and planners and designers 
of new facilities is to understand the seismic hazard risk. The location and the 
physical characteristics of the site determine the extent of seismic hazards, 
which include the potential intensity of ground shaking, the possibility of 
liquefaction, earthquake induced landslide, or more rarely, the potential of a 
tsunami or seiche. If ground motion is the only or predominant hazard, site 
seismicity can be determined from the local building code by a local structural 
engineer or a building department official. More detailed information can be 
obtained from the USGS Web site, which provides seismological information for 
any zip code in the nation. When hazards in addition to ground motion exist, 
seismic experts are needed to determine the probability and extent of these 
risks and possible mitigation techniques.

The selection of hospital sites is generally based more on factors associated 
with availability of land, proximity to service area, cost, convenience of 
access for patients, visitors, and staff, or general demographic concerns than 
on the exposure of these sites to natural hazards, particularly earthquakes. 
Careful site selection, however, is a critical first step in risk reduction, 
because the potential ground motion from a single earthquake may vary 
considerably depending on the nature of the soil and the distance of the site 
from known earthquake faults. A large medical center that is developing a plan 
for new multi-building facility should include comprehensive analysis of the 
site characteristics and its exposure to natural hazard as an important factor 
in evaluating alternative sites. 

- Consider seismic constraints in site selection. Although it would be very rare 
for a hospital district to make a site selection decision based solely on 
seismic risk, moving a hospital even a few miles in some cases can make a big 
difference to its exposure to seismic hazard. An example is locating a hospital 
5 to 10 miles away from a major earthquake fault, rather than locating it within 
1 mile of the fault.

- Locate the building on a soil type that reduces the risk. 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 damage from 
liquefaction, land sliding, or lateral spreading of the soil. 

- Since hospitals should be designed to performance-based criteria that include 
minimum disruption and continued operation, the location of the site within the 
region may play a critical role in achieving the required performance. The 
definition of site becomes the region within which the facility is located, 
and assessments should be made with respect to its access to materials, 
personnel, and utilities, as well as its position in the regional transportation 
grid. 

In most cases, however, it is probable that a site with optimal characteristics 
(other than seismic considerations) will be selected and that seismic issues 
will be mitigated as part of planning and design of the facility. A proposed 
construction site located directly over a fault is probably the only location 
characteristic that would lead to rejection of an otherwise suitable site. 

2.4.2 Seismic Design Basics

Minimum standards and criteria for seismic design are defined in the seismic 
section of building 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. The 
seismic provisions in building codes are adopted by State or local authorities, 
so it is possible for a seismically-prone region to be exempt from seismic 
building code regulations if the local community decides that the adoption of 
such provisions is not required. Hospital board officials and designers should 
not ignore seismic design requirements irrespective of whether local communities 
have adopted seismic code regulations or not.

Budgeting extra costs for seismic design 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 designing for earthquakes, and the 
building stock in general would be especially vulnerable. Hospital buildings are 
an important community resource (along with other essential buildings, such as 
schools and fire and police stations) that must be protected as much as 
possible.

2.4.3 Structural Systems

Health care facilities occupy buildings of different sizes, configurations, and 
structural systems. Additionally, hospitals differ in the level of services they 
provide. Some hospitals are distinguished by high occupancies, while others 
emphasize outpatient services. The mixture of functions and services is such 
that hospitals frequently require building systems that can accommodate very 
diverse functions. These can vary from acute care with many diagnostic, 
laboratory, and treatment areas requiring high-tech facilities and services to 
support functions such as laundry, food service, receiving, storage, and 
distribution. 

Smaller healthcare facilities may encompass one or more of these functions, such 
as predominantly longer residential care, or specialized treatment such as 
physical rehabilitation or dialysis. This functional variety may influence some 
structural choices, but the structure, as in all buildings, plays a primary role 
in providing a safe and secure support for the facility activities. Since 
continued operation is the preferred performance objective, structural design 
that goes beyond life safety standards is necessary, which requires special 
attention.

2.4.3.1 Basic Types of Lateral Force Resisting Systems

Figure 2-43 shows the basic types of structural lateral force resisting systems. 
These systems compose the three basic alternatives for providing lateral 
resistance: shear walls, braced frames, and moment-resistant frames. Each of 
these has specific characteristics, such as stiffness, relationship to spatial 
requirements, and cost-effectiveness that must be evaluated for each project. 
Diaphragms connect horizontal and vertical elements and transfer the seismic 
loads to the lateral force resisting system. This concept is shown in Figure 2-
43. Structural material alternativessteel, reinforced concrete, reinforced 
concrete masonry, and wood, provide further options that must be evaluated. 
Figures 2-44, 2-45, and 2-46 show the three systems and materials that can be 
used to resist seismic forces in more detail. 

[Begin figures]
Figure 2-43 is an illustration showing basic types of lateral force resisting 
systems. Source: BSSC: Presentations to the Architectural Community, 2001, Chris 
Arnold and Tony Alexander

Figure 2-44 is an illustration showing a reinforced concrete shear wall 
structure

Figure 2-45 is an illustration showing a steel braced frame structure

Figure 2-46 is an illustration showing a steel moment resistant frame
[End figures]

Many variations of these types are possible, together with other structural 
types such as wood frame, light steel, reinforced masonry, and tilt-up 
reinforced concrete. The seismic codes expand these three basic systems into six 
categories by the addition of two categories of dual systems (composite steel 
and reinforced concrete) and inverted pendulum systems (such as cantilevered 
water tanks). 

For each of the three basic systems, four coefficients and factors are provided, 
of which the most unique is the response modification, or R factor. This is a 
coefficient related to the overall behavior and ductility of the structural 
system. R has values from 1.25 to 8, and is a divisor that modifies the base 
shear value obtained in the ELF procedure by reducing the design forces. The 
higher the number assigned to R, the greater the reduction. Thus, the highly 
ductile and better-understood moment resisting frame has a value of 8, while an 
unreinforced masonry structure has a value of 1.5. Using the R reduction is 
justified because experience and research confirm the expected performance of 
these systems and their ability to accept overloads.

2.4.3.2 Innovative Structural Systems

In recent years, a number of new approaches to the seismic protection of 
buildings have been developed that are now seeing increased use. These systems 
depend on modifying either the seismic loads that are transmitted from the 
ground to the building, or the building response. In both instances, the 
strategy is to let the building ride with the punch, rather than relying on 
resistance alone to protect the building.

Seismic isolation, generally referred to as base isolation, is a design concept 
that reduces the earthquake motions in the building superstructure by isolating 
the building from ground motions. This is accomplished by supporting the 
building on bearings that greatly reduce the transmission of ground motion (see 
Figure 2-47). Both the structure and the nonstructural systems are subjected to 
reduced shaking levels, so the system is well suited for essential facilities, 
like hospitals that need to remain functional following an earthquake. Many 
emergency management centers and a few hospitals in the United States have 
employed this technique. It has also been used by private industry on buildings 
of high importance, and as a retrofit technique, mostly for significant historic 
buildings.

[Begin figure]
Figure 2-24 is an illustration showing seismic isolation. [End figure]

Passive energy dissipation is another concept in which the earthquake forces in 
the building are reduced by the introduction of devices that are designed to 
dissipate the earthquake energy in a controlled manner using friction, 
hydraulics, or deformation of material specially placed for this purpose (see 
Figure 2-52). These devices usually take the form of a bracing system that 
connects the vertical structural members together. These devices also increase 
the damping of the structure and reduce the drift. The Bremerton Naval Hospital 
provides an example of successful rehabilitation that used these devices (see 
Section 2.4.6.2).

2.4.3.3 Structural Systems Selection

The seismic code prescribes the analysis procedures for a number of different 
types of structural systems. The engineer, however, must choose the system that 
is appropriate for the type of building and its use. Structural systems vary 
greatly in their performance attributes, even though they may all meet the 
requirements of the seismic code if correctly designed and constructed. 

The critical initial step in selecting a structural system is to establish 
performance goals for the project. Because hospitals are classified as essential 
buildings, the seismic code requirements imply a requirement for a certain level 
of performance. An informed performance-based design procedure is necessary. 
This procedure should involve the owner, the full design team, and any other 
stakeholders. The process should cover all steps, from determining performance 
goals to the detailed design and construction of the project. 

On the technical side, the most important measure of good earthquake-resistant 
design is the effect on the structure after the earth has stopped shaking. With 
little building damage, there is a good chance that the building will be 
functional and repair costs will be low. With significant damage, it is unlikely 
that the building would be functional and repair or replacement costs would be 
high. The measure of success in seismic design of a hospital is the extent to 
which a building can avoid significant damage and retain a reasonable level of 
functionality without the need to evacuate patients. The behavior of each 
structural system and building configuration differs with earthquake ground 
motions, soil types, duration of strong shaking, etc., but past observations of 
damage can inform the decisions about the most appropriate systems.

The best performing structural systems will do the following:

- Possess stable cyclic behavior. Will not be prone to sudden structural failure 
or collapse

- Control lateral drift. Will keep drift (lateral distortion between floors) to 
reasonable dimensions to reduce damage to nonstructural components, such as 
glazing, partitions, and cladding

- Dissipate seismic energy without failing. Absorb the earthquake energy in a 
controlled manner without causing structural members to fail 

- Create a good chance of functionality and a low post-earthquake repair cost

2.4.4 Nonstructural Components and Systems

For a long time, seismic building codes focused exclusively on the structural 
components of building. Although this focus still remains dominant, experience 
in recent earthquakes has shown that damage to nonstructural components and 
systems is also of great concern. Continued hospital operation is increasingly 
dependent on nonstructural components and systems, including medical and 
building equipment. Hospital operations also depend on specialized services, 
some of which involve storing of hazardous substances, such as pharmaceuticals, 
toxic chemicals, oxygen, and other gases, that must be protected against 
spilling. Distribution systems for hazardous gases must be well supported and 
braced. Unlike most buildings, hospitals require a very extensive plumbing 
network to supply water throughout the building, and an adequate piping network 
to supply water for fire sprinklers, which increases the risk of secondary water 
damage in case of failure of these systems during earthquakes.

In a typical hospital, not only do the nonstructural components play a major 
role in operations, they also account for large share of the cost. Typically, 
for a medium-size hospital, the structure accounts for around 15 percent of the 
total cost, and the nonstructural components for the remaining 85 percent. Of 
the latter, the mechanical, electrical, and plumbing systems alone account for 
approximately 35 percent of the total building cost.

Even though the building structure may be relatively undamaged after an 
earthquake, excessive structural motion and drift may cause damage to ceilings, 
partitions, light fixtures, service piping, and exterior walls and glazing. In 
addition, storage units, medical equipment, and filing cabinets may topple and 
cause injuries if not properly anchored or braced. Excessive drift and motion 
may also lead to damage to rooftop equipment, and localized damage to water 
systems and fire suppression piping and sprinklers. Heavy equipment, such as 
shop machinery, kilns, and heavy mechanical and electrical equipment, may also 
be displaced and become non-functional. 

2.4.4.1 Code Regulated Nonstructural Systems

The seismic code categorizes nonstructural components as architectural 
components or mechanical and electrical components. Many of the hospital 
contents, such as furnishings and specialized equipment, which may be critical 
to hospital function, are not subject to regulation.

Table 2-3 shows the list of nonstructural components and systems that are 
subject to code regulation. 

[Begin table]
Table 2-3: Code Regulated Architectural, Mechanical, and Electrical Components 

Architectural Components: 
Interior Nonstructural Partitions 
 Plain unreinforced masonry 
 Other walls and partitions 
Cantilever Elements, Unbraced
 Parapets 
 Chimneys and stacks 
Cantilever Elements, Braced 
 Parapets 
 Chimneys and stacks
Exterior Nonstructural Wall Elements 
 Wall elements 
 Body of panel connections 
 Fasteners of connecting systems 
Veneer 
 Limited deformability 
 Low deformability 
Penthouses, Not Part of Main Structure 
Ceilings 
Cabinets 
 Storage cabinets and lab equipment 
Access Floors
 Special access floors 
 All others 
Appendages and Ornamentation
Signs and Billboards
Other Rigid Components
 High deformability elements
 Limited deformability elements
 Low deformability elements
Other Flexible Components
 High deformability elements
 Limited deformability elements
 Low deformability elements

Mechanical and Electrical Components: 
General Mechanical
 Boilers and furnaces
 Pressure vessels
 Stacks
 Cantilevered chimneys
 Other
Manufacturing and Process Machinery
 General
 Conveyors (non-personnel)
Piping Systems 
 High deformability
 Limited deformability
 Low deformability
HVAC System Equipment
 Vibration isolated
 Non-vibration isolated
 Mounted in-line with ductwork
 Other
Elevator Components 
Escalator Components
Trussed Towers (Free-standing or Guyed)
 Special access floors
All others
Lighting Fixtures
[End table]

Figure 2-48 is an example of a cable tray with a braced support system designed 
in conformance with the seismic code.

[Begin figure]
Figure 2-48 is an illustration showing seismically braced cable tray support 
[end figure]

2.4.4.2 Interstitial Space for Utility Installations

Developments in medical technology frequently require hospitals to add or re-
route utility and medical services infrastructure and add electrical capacity to 
various parts of the building, often with consequent disruption of the 
operations and difficulties caused by limited available space above the ceiling. 
In response to these problems, a number of hospitals have been designed with 
interstitial service space. In some designs, the interstitial floor is a 
nonstructural floor hung from the structural floor above (Figure 2-49).

[Begin figure] 
Figure 2-29 is an illustration showing an interstitial floor system hung from 
the floor above. [End figure]

The interstitial space concept provided a full floor above the functional space 
where service personnel can work to add or modify installations without 
disturbing the space below, or disrupting hospital operations. The main 
structural effect of an interstitial floor is to increase the floor-to-floor 
height of the occupied floors and the building as a whole, with some increase in 
the amount of structural material. Any of the common steel and concrete frame 
systems can be used to provide the interstitial floor arrangement. The 
interstitial space concept was used in the Loma Linda Veterans Hospital (see 
Section 2.4.5.1)

2.4.5 Mitigation Measures for New Buildings

If mitigation measures are instituted in the planning stage, a high level of 
seismic protection can be achieved in a new building with the following steps:

- Assure that the latest model building code is used, using the appropriate 
importance factor.

- Include provisions in the design to allow the facility to function on its own 
for 4 days. This would require storage of sufficient fuel for emergency standby 
power supply system, reserve water supply, and provisions for waste water 
storage. Assure that access to the site will not be impaired by earthquake 
damage.

- Although seismic isolation should be considered for all buildings that are 
intended to be functional after an earthquake, this measure should be considered 
as a realistic alternative only for sites with SDS over 0.8 g.

- Consider a peer review of the structural design, particularly in jurisdictions 
that do not require a thorough plan check to obtain a building permit. A peer 
review is essential if innovative structural systems, such as isolation or 
structural dampers, are used.

- Assure that the seismic design for nonstructural elements and systems 
regulated by the building code are the responsibility of the design team. A list 
of such responsibilities is given in FEMA 356. One method of gaining such 
assurance is to create the position of a Nonstructural Seismic Coordinator 
(NSC), whose responsibility is to review the specifications, drawings, or other 
methods proposed to attain adequate seismic anchoring and bracing of all 
systems. Further, the NSC will follow the submittals and construction processes 
to assure appropriate implementation.

- Put in place a comprehensive system to monitor construction quality and to 
track significant change orders that might imply subtle reductions in structural 
or nonstructural seismic performance.

2.4.5.1 The Case of Loma Linda Veterans Hospital

The 500-bed Veterans Administration Hospital in Loma Linda, CA, opened in 
September 1977. Designed as a replacement facility for the Veterans 
Administration Hospital lost in the 1971 San Fernando earthquake, it was built 
in the area of extremely high seismicity, and represents an interesting case of 
careful seismic design.

The project was remarkable because of the extent to which the configuration of a 
large and complex building was influenced by seismic design concerns. At the 
same time, the project provides a lesson in showing that early recognition of 
seismic design determinants by the whole design team, and a serious 
interdisciplinary approach from the inception of design, can enable requirements 
of both seismic design and hospital planning and economy to be achieved with 
equal effectiveness.

The San Bernardino Valley is seismically very active, and the final site 
selected for the new hospital had 11 known active faults within a 65-mile 
radius, including the San Jacinto fault and two segments of the San Andreas 
fault. The potentially active Loma Linda fault was also believed to be located 
near the site, and after intensive studies, it was concluded that the most 
likely location of the fault was 200 to 400 feet southwest of the site, but that 
surface rupture at the site was not likely. The risk of soil amplification was 
significant.

The consultants recommended that design earthquakes of magnitude 8+ and duration 
of 3540 seconds on the San Andreas fault, and magnitude 6.57.25 and duration 
of 20 seconds on the San Jacinto fault, should be considered. The building 
structure was to be designed for a peak acceleration of 0.5 g, while the 
essential and potentially damaging nonstructural components were to be designed 
for an acceleration of 2.0 g. 

Some of the design force determinants evaluated were dependent on a building 
configuration concept. 

1. Site geometry: The large 40-acre site enabled the designers to consider a 
freestanding building unconstrained by site geometry. The site area was 
sufficiently large to allow consideration of a relatively low, horizontally 
planned building.

2. Design Program: Research studies on hospital organization and planning had 
established some general benefits of horizontal planningdefined as plans in 
which clinical and diagnostic areas are placed on the same floor as nursing 
areas, rather than being concentrated into a base structure with a vertical 
connection to the bed-related functions. Experience in vertically planned 
hospitals had indicated some problems in ensuring adequate circulation, since 
the concentration of vertical circulation into a single tower tended to result 
in over- or under-capacity, depending on the time of the day. There were also 
indications of a general preference by staff for horizontal movement over 
vertical, and an indication that a reduction of vertical circulation for 
severely ill patients would be desirable.

3. Aesthetics: The design of hospitals tends to be dominated by the solution of 
very complex planning, service, and equipment problems, and appearance tends to 
be a secondary concern. The city of Loma Linda was anxious that the setting of 
the hospital should be park-like. In response to this desire, and to the 
generally small scale of the immediate site surroundings, the image of a low, 
nonassertive building, placed toward the center of the site, seemed appropriate. 
Although very large in size, the buildings relatively low height and the 
considerable size of the site was to help reduce the visual effect of the 
building on the neighboring community

4. Building system: The Loma Linda Hospital was intended as a demonstration of 
the Veterans Administration Hospital Building System, which had been developed 
over a period of several years by the same team that was responsible for the 
hospital design. The building system consisted of a carefully conceived set of 
design concepts intended to rationalize and organize the preliminary hospital 
design.

The structural design comprised moderate-span simple post and beam shallow floor 
framing system, large floor-to-floor heights, and lateral force resistance 
elements concentrated in the service tower at the end of each of the service 
modules. The planning and aesthetic requirements of a low, deep plan building 
coincided well with a stiff seismic design that would minimize story drift; 
consequent architectural, mechanical, electrical, and contents damage; and loss 
of operational capability. In addition, the low, stiff building would have a 
shorter period and possibly a lower response than the projected response spectra 
peaks of 0.3 and 0.8 seconds from the two nearby faults. The only way of moving 
the building response well away from the ground response would be to develop a 
flexible high-rise structure that would be undesirable from all the other 
viewpoints considered.

The chosen configuration was the simplest of all those studied: a simple block, 
almost square in plan, with no basement and with a symmetrical pattern of four 
courtyards within the block. The courtyards were relatively small. The plan had 
an even distribution of shear walls throughout, running uninterrupted from roof 
to foundation and having direct continuity in plan with the structural framing 
members.

The planning and circulation of the building were carefully related to shear 
wall layout to achieve minimum shear wall penetration with clearly defined, 
highly accessible public and departmental planning. The eight service towers 
(four at each end) provided a location for major shear walls. Each tower 
provided two shear walls in the east-west direction and one in the north-south 
direction. 

The general lateral resisting system used concrete shear walls and a ductile 
moment-resistant backup frame. The stiff primary shear wall system was 
designed for a high force level, so that the structure will tend to have low 
lateral deflections for the design earthquakes described earlier. The calculated 
maximum story-to-story drift was well within presently accepted desirable ranges 
for hospitals.

The backup frame was intended to form a stable and reliable backup system for 
lateral force resistance and redistribution of forces should one or more of the 
shear walls become seriously damaged. The chances of the backup frame being 
forced to work to its full capacity were considered small, but considering the 
size and importance of the facility, and the uncertainties of estimating the 
nature of ground motion, the possibility could not be ignored.

Shear walls were always placed at the perimeter of service modules to minimize 
interference. Interior girders were dropped below the beams to minimize 
interference with plumbing service and to allow beam continuity across the 
module. As a result of the service organization, all beams and girders are free 
of penetrations. These framing characteristics were the product of the research 
study that determined the systems design.

The shear walls are collocated with frame lines. The advantages of this 
arrangement were:

- Beams or girders were always parallel and lined up with the walls, to serve as 
lateral force collectors.

- The continuation of these members through the wall allowed direct transfer of 
forces from the diaphragm to the wall.

- The columns at the end of walls formed the required ductile flange members.

- Frame members were in the correct position to provide vertical support for 
shear wall dead loads.

Complete calculations and designs were completed for all nonstructural 
components and systems. The bracing of utility distribution systems, ceilings, 
partitions, and lights was made easier and less expensive by the presence of the 
interstitial floor system shown in Figure 2-49.

2.4.6 Mitigation Measures for Existing Buildings

Engineering of structural and nonstructural risk reduction measures is similar 
for new and existing hospitals. New hospital design offers the possibility to 
minimize the risk by selecting a site subject to less ground motion, with better 
soil conditions, or located farther from 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 hospital. The existing building may have been designed to an 
obsolete seismic code or no code at all, its materials may be questionable, or 
the building configuration and structural system may be inappropriate. 
Therefore, protecting an existing hospital must start with a detailed evaluation 
of its vulnerability, because seismic retrofitting is both disruptive and 
expensive, and should not be implemented without careful study.

2.4.6.1 Procedures and Design Strategies for Rehabilitation of Structural 
Systems

Additions to an existing hospital must meet all the code requirements for a new 
building. With the exception of California, there are currently no seismic codes 
that apply to the retrofit of existing hospitals. 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 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 should be applied to the 
retrofit design of existing ones.

FEMA has developed many such documents and several have been adopted by ASCE as 
standards suitable for adoption by building codes (see ASCE 31 and ASCE 41). The 
planning process for retrofits should begin with an evaluation procedure, such 
as Tier 1 of the ASCE 31 Seismic Evaluation of Existing Buildings (ASCE, 2003). 
If the evaluation results require a retrofit of an existing building, ASCE 41, 
Seismic Rehabilitation of Buildings (ASCE, 2007) is the authoritative source 
document and can be used to help a hospital design team select seismic 
protection criteria. The architect and engineer can also use the document for 
the design and analysis of the seismic rehabilitation project. 

ASCE 41 provides methods and design criteria for several different levels of 
seismic performance. The document also recommends a thorough and systematic 
procedure for performance-based seismic design, intended to produce a design 
responsive to the owners level of acceptable risk and available resources. This 
process starts with a requirement to select specific performance goals 
(Rehabilitation Objectives) 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. See Section 2.2.3 for a 
further description of performance-based seismic design.

Typical basic design concepts for improving the structural seismic performance 
of an existing hospital include:

- 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.

- Adding new lateral force resisting elements, such as shear walls or braced 
frames. 

- Removing or reducing configuration irregularities. This involves providing 
seismic separations in irregular configurations, or adding shear walls or 
bracing to reduce torsional effects. Mass can also be removed by removing 
stories.

- Modifying the basic seismic response of a structure by adding dampers or 
installing seismic isolation systems.

2.4.6.2 The Case of Naval Hospital Bremerton

Naval Hospital Bremerton, located in Bremerton, WA, not only serves military 
personnel and their families in the areaup to 60,000 peoplebut could also be 
called on to serve more than 250,000 people on Washingtons Kitsap Peninsula 
after a major earthquake. The facility is spread over 40 acres, and includes 20 
buildings, some of which are 70 years old. Being one of only two major hospitals 
in the region, the Navy was concerned about its response capability to moderate-
to-strong seismic ground shaking expected at the site (Wilson, 2005).

To obtain a broad understanding of the vulnerability of the facility and the 
relative risk among the many buildings, a rapid visual screening was completed 
by the Navys consultant, Reid Middleton, using FEMA 154 (FEMA, 2002), which 
considers structural type, basic seismic characteristics, building use, and 
occupancy load. This relatively modest effort provided an overview of the 
seismic risk at the campus, as well as a preliminary relative ranking among 
buildings. It made it obvious that the main hospital building, a nine-story, 
250,000-square-foot building that housed most of the essential medical 
functions, should be a priority (see Figure 2-50).

[Begin figure]
Figure 2-50 is a photo of the main building at Naval Hospital Bremerton. Source: 
Reid Middleton, Inc. [End figure]

The building is a steel moment frame, constructed in the 1960s, that employed 
welded beam-to-column connections, now known to be prone to cracking when 
subjected to large seismic deformations. A more detailed structural analysis and 
evaluation was performed using FEMA 356 (FEMA, 2000). It was found that although 
the frame does not pose a significant threat of collapse, the buildings ability 
to function after an earthquake could be severely limited by damage to 
structural joints, and by nonstructural damage. 

In February 2001, while the Navy and the design team were considering their 
options, the Magnitude 6.8 Nisqually earthquake struck the area. The earthquake 
occurred deep below the surface and approximately 30 miles from the site. The 
ground motions at the site were below the design shaking for the site, but 
nevertheless caused significant nonstructural damage  particularly in the upper 
floors (see Figure 2-51). Such nonstructural damage always causes concern about 
the integrity of the structureand often requires destructive exploration to 
verify. Based on preliminary structural inspections, aided by recordings of the 
response from instruments in the building, the Navy decided to stay in the 
building while more extensive exploration and analysis were performed. It took 
several months before nonstructural repairs were completed and the building 
returned to full use. Subsequent structural review indicated no structural 
damage.

[Begin figure]
Figure 2-51 is photo of the disruption in the upper floors at Naval Hospital 
Bremerton from the Nisqually earthquake. Source: Reid Middleton, Inc. [End 
figure]

The data on the response of the building to the Nisqually earthquake provided an 
opportunity to simulate, by computer analysis, a design event. This simulation 
revealed that shaking at the design level could cause unacceptable damage, both 
to the beam-column joints and to nonstructural systems. The team found that 
traditional, code-based retrofits, such as local modification of the 1,550 beam-
column connections, or introduction of braced frames to meet current standards, 
were too costly and disruptive. Solutions were investigated using the more 
finely tuned, performance-based design methodologies of FEMA 356, and a more 
innovative scheme, based on the introduction of supplemental seismic dampers, 
appeared feasible.

Several styles of dampers are available for use in buildings, including those 
employing controlled yielding of steel elements, those based on friction 
(similar to a brake shoe), and more sophisticated hydraulic dampers (similar to 
a shock absorber). Dampers are normally placed in a building in a configuration 
similar to diagonal braces, and work against the movement between floors (see 
Figure 2-52). This action reduces inter-story drift and, to a lesser extent, 
reduces floor accelerations that cause sliding and overturning of equipment and 
contents. Although dampers should be evenly distributed throughout the building, 
they allow greater flexibility in placement than braced frames or other standard 
lateral force resisting systems. The flexibility in placement of the dampers 
means that critical locations, those that would reduce usefulness of the 
intended space or cause operational shutdowns during installation, can be 
avoided. Using performance-based design concepts, the team set the target 
structural performance levels for Immediate Occupancy (see Section 2.2.3.1) for 
the design earthquake shaking, and Collapse Prevention for a reasonable estimate 
of the worst shaking expected at the site. Structural analysis indicated that 
adding a total of 88 fluid viscous dampers, spread through the facility, would 
deliver the desired performance within the bounds of the current analysis and 
prediction capability. The cost of the structural retrofit was projected to be 
less than 10 percent of the replacement cost, a value that would yield a 
favorable life cycle cost (from damage avoided) on most sites in the country.

[Begin figure]
Figure 2-52 is a photo of the installation of dampers at the Naval Hospital 
Bremerton. The configuration is similar to steel braced frames. [End figure]

In parallel with the retrofit design, the team developed an inexpensive and 
innovative program (called REACHRapid Evaluation and Assessment Checklist) to 
improve the speed and effectiveness of future building safety evaluation 
following a seismic event. For many structural types, the seismic structural 
damage is covered and not obvious; concern about the extent of structural damage 
can sometimes delay decisions about building safety, or even cause an unneeded 
evacuation. The building-specific REACH program incorporates real-time data from 
the buildings seismograph network. Threshold values for acceleration and 
displacement are pre-determined by the design team, and actual building motion 
is then compared with these threshold values to allow more accurate and informed 
decision making regarding the ability of the building to sustain the safe 
delivery of medical services after earthquakes. The REACH checklist contains 
additional information, such as a description of the structural system, 
structural drawings, recommended structural inspection sites, and other 
information of use to the facility engineer and building inspectors. The REACH 
documents are stored in the facility departments disaster response locker, and 
are reviewed by facility staff during routine emergency drills.

Recognizing the significant effect that damage to nonstructural systems can have 
on post earthquake functionality, the facility has begun retrofit of 
nonstructural elements, including bracing of acoustic tile ceiling and light 
grids, mechanical system piping, as well as cabinetry and furniture. Future 
analysis and reinforcement of bracing for critical equipment (such as radiology 
and laboratory) is planned.

2.4.6.3 Procedures and Design Strategies for Rehabilitation of Nonstructural 
Systems

Complete, nonstructural seismic rehabilitation of an existing hospital in 
operation is disruptive and very expensive. However, it is relatively easy to 
incorporate seismic bracing and anchoring during ongoing renovation or 
rehabilitation work. A more active and aggressive program requires developing 
databases of components and systems, and developing a process for prioritizing. 
Priorities can be set by considering importance to life safety, importance to 
overall functionality, associated cost and disruption, component vulnerability, 
or by cost-benefit considerations (see FEMA 274 for more information). 

Components commonly found to be of high priority because of their importance, 
high level of vulnerability, and relatively low cost include anchorage of 
standby generators, medical gas storage, pressurized piping, and communications 
systems. Although not normally considered a dangerous or high-priority system, 
damage to lightweight suspended panelized ceiling and light systems can disrupt 
hospital operations, as happened in Hawaii where such damage forced the KCH to 
evacuate (see Section 2.3.2.2). It is important that the key vulnerabilities of 
each facility be identified and considered in emergency planning and mitigation 
programs.

2.4.6.4 Summary of Risk Reduction Measures for Existing Buildings

Achieving cost-effective improvements in seismic performance of existing 
facilities is far more complex than improving expected performance for proposed 
new buildings in the planning and design stage. First, and most obvious, it is 
always far less expensive to include relatively small changes in a new design to 
create seismically resistant structural and nonstructural systems than it is to 
retrofit  or sometimes replace  existing systems. The complexity and expense 
of retrofitting is exacerbated when such work is not done in conjunction with 
complete renovation  that is, if the building has to remain mostly occupied and 
operational. 

Following the recommended seismic evaluations, careful analysis is needed to 
identify significant life safety risks from potential structural collapse; to 
identify and achieve short-term, high benefit-cost mitigation measures; and to 
plan for longer-term overall mitigation. The following steps are recommended:

- Engage a structural engineer experienced in seismic evaluation and design to 
perform a seismic structural evaluation of existing buildings on the campus that 
contribute to the hospital function. The primary purpose of such an analysis is 
to quickly identify buildings that may be seriously damaged or even collapse in 
a code-level earthquake. A secondary purpose is to gain an understanding of the 
probable performance of the structural and nonstructural systems of each 
building by using the data charted in Figures 2-41 and 2-42.

- Engage an architect, mechanical and electrical engineer, and structural 
engineer, as needed, to evaluate the probable seismic performance of 
nonstructural components and systems.

- Update the emergency response plan, considering the results of the seismic 
evaluations.

- If significant life safety risks are identified from review of either 
structural or nonstructural systems, make plans to minimize occupancy of the 
building, replace the building, or retrofit to an acceptable level of 
performance.

- In most cases, shaking of less than code intensity, which may cause minor or 
no structural damage, can cause serious nonstructural damage. The most 
vulnerable elements that can affect the functions of the hospital have been 
identified from past earthquakes. They are the emergency generator, the bulk 
oxygen storage tank, the internal and external emergency communication systems, 
and the patient elevators. These elements, other than the elevators, normally 
can be anchored and braced against seismic damage rather inexpensively and 
quickly. The elevators may require extensive retrofit to assure operation after 
strong shaking. However, to assure safe patient relocation immediately after an 
event, it is recommended that one patient elevator serving each floor be 
retrofitted to at least the capacity of the structural system and to current 
standards for essential facilities. Automatic seismic switches that demobilize 
elevators at low shaking levels should be used with caution, as the switch may 
defeat the purpose of the strengthened elevator.

- Mechanical equipment on vibration isolators that are not designed for seismic 
forces are extremely vulnerable to seismic damage. This equipment should be 
identified and fitted with appropriate anti-seismic isolators, or seismic 
snubbers, as soon as possible.

- Nonstructural elements affected by or exposed by normal renovation should be 
upgraded to current standards.

- The expected seismic structural performance of all buildings on the campus 
should be considered as part of master planning. Planning should also consider 
opportunities to provide 4 days of self reliance, (See Section 2.4.5).

- Vulnerable medical buildings that can lose full functionality after a code 
earthquake should be studied for retrofit or replacement. Improvements in 
seismic structural performance can often be combined with major renovations. 
Adjacent additions can sometimes be made sufficiently strong to buttress an 
existing building.

- Incremental seismic rehabilitation, as described in FEMA 396 (2003), should 
also be considered for applicability. 

- An emergency plan that considers the care of the patients and staff of the 
facility, as well as the surrounding community, should be kept up to date and 
should include a realistic estimation of the seismic performance of the 
structural and nonstructural systems in each building, and on the site in 
general.

- The Hospital Seismic Safety Evaluation Checklist (Table 2.4) should be 
applied.




2.5 CHECKLIST FOR SEISMIC VULNERABILITY OF HOSPITALS

The Checklist for Seismic Vulnerability of Hospitals (Table 2-4) is a tool that 
can be used to help assess site-specific seismic hazards and building 
vulnerability. The checklist is useful during site selection, preliminary design 
of a new building, or when considering rehabilitation of an existing facility. 
In addition to examining building design issues that affect vulnerability, the 
checklist also helps users to examine the functionality of the critical and 
emergency systems upon which most hospitals depend. The checklist is organized 
into separate sections, so that each section can be assigned to a subject expert 
for greater accuracy of the examination. The results should be integrated into 
a master vulnerability assessment to guide the design process and the choice of 
appropriate mitigation measures.

[Begin table]
Table 2-4: Hospital Seismic Safety Evaluation Checklist

Site Condition
Vulnerability Sections: Is there an active fault on or adjacent to the site?
Guidance: If suspected, site-specific geologic investigations should be 
performed. Consult local building department, State geologist, local university, 
or local geotechnical expert.

Vulnerability Sections: Does the site consist of soft, stiff, or dense soil or 
rock?
Guidance: If the presence of softer soil that can lead to force amplification or 
liquefaction is suspected, site-specific geologic investigations should be 
performed

Vulnerability Sections: Are post-earthquake site egress and access secured?
Guidance: Alternative routesunlikely to be blocked by falling buildings, power 
lines, etc. are desirable.

Vulnerability Sections: Are utility and communications lifelines vulnerable to 
disruption and failure?
Guidance: Security of the entire utility and communications network is the 
issue: the facility may be affected by offsite failures.

Vulnerability Sections: Are there alternate or backup sources for vital 
utilities such as water and power?
Guidance: Redundant systems increase the probability of the hospital remaining 
functional after an event.

Architectural

Vulnerability Sections: Is the architectural/structural configuration irregular?
Guidance: Irregular vertical and horizontal configurations, such as set backs, 
open first stories, or L- or T-shaped plans, may lead to significant stress 
concentrations.

Vulnerability Sections: Is the building cladding attached to structural frames 
so that it can accommodate drift?
Guidance: Frames are flexible, and cladding must be detailed to accommodate 
calculated drifts and deformations. If waterproofing of these systems is 
compromised, rain following an earthquake could cause parts of the building to 
be closed.

Vulnerability Sections: Are heavy veneers, such as brick or stone, securely 
attached to the structural walls?
Guidance: Shear wall structures are very stiff and carry large earthquake 
forces; heavy attachments must be securely attached.

Vulnerability Sections: Are glazing and other panels attached so that they can 
accommodate drift?
Guidance: Glazing must be installed with sufficient bite and adequate space 
between glass and metal to accommodate drift

Vulnerability Sections: Are light, suspended grid ceilings and lights braced and 
correctly attached at walls?
Guidance: Suspended ceilings, if not braced, easily distort (particularly in 
light and flexible frame structures), thus causing ceiling panels to fall out.

Vulnerability Sections: Are heavy plaster suspended ceilings securely supported 
and braced?
Guidance: Heavy lath and plaster ceilings in older facilities are very dangerous 
if poorly supported.

Vulnerability Sections: Are partitions that terminate at a hung ceiling braced 
to the structure above?
Guidance: Partitions need support for out-of-plane forces, and attachment to a 
suspended ceiling grid only is inadequate.

Vulnerability Sections: Are masonry or hollow tile partitions reinforced, 
particularly those surrounding exit stairs?
Guidance: Heavy partitions attract strong earthquake forces because of their 
stiffness and mass, and are prone to damage. They are particularly dangerous 
around stairs and exit ways.

Vulnerability Sections: Are parapets and other appendages securely braced and 
attached to the building structure?
Unreinforced masonry parapets are especially vulnerable. Brace items such as 
cornices, signs, and large antennas.

Structural System
Vulnerability Sections: When was the existing structure designed?
Guidance: Buildings with no, or outdated, seismic design are unlikely to perform 
adequately in strong shaking. Verify that the Importance Factor was used in 
design.

Vulnerability Sections: Has the local seismic zoning changed significantly since 
the building was designed?
Guidance: Local expectation of shaking intensity can change as scientific 
knowledge increases

Vulnerability Sections: Is there a continuous load path from all components of 
the building to the foundation?
Guidance: A continuous load path assures that the structure will act together as 
a whole when shaken. Connections from walls to floors and roofs should also form 
part of this load path.

Vulnerability Sections: Is all load-bearing structural masonry reinforced 
according to code?
Guidance: Older unreinforced masonry has proven very vulnerable in strong 
shaking.

Vulnerability Sections: Are horizontal diaphragms correctly designed and 
constructed with necessary chords and collectors?
Guidance: Large diaphragm openings and the edges of diaphragms need careful 
design to ensure forces are properly transmitted to walls and frames.

Nonstructural Systems
Vulnerability Sections: Are there backups for critical municipal utilities?
Guidance: Municipal utilities such as water, power, and gas, are often disrupted 
in strong shaking. Onsite backups should provide 48 hours of use.

Vulnerability Sections: Are ducts, piping, conduit, fire alarm wiring, and 
communication systems that pass through seismic joints provided with flexible 
connections?
Guidance: Differential movement between sections of the building can cause 
breakage and leaks in pipes and ducts if no provision is made for movement. If 
walls at joint are firewalls, penetrations should be fireproofed.

Vulnerability Sections: Is heavy mechanical equipment adequately secured?
Guidance: Heavy equipment may slide and break utility connections.

Vulnerability Sections: Are vibration isolators for vibrating equipment designed 
for seismic forces?
Guidance: Equipment may jump off very loose isolators and may break restraints 
designed for wind only.

Vulnerability Sections: Is the piping properly braced and provided with 
expansion joints?
Guidance: See Section 2.4.4.

Vulnerability Sections: Is ductwork properly supported and braced?
Guidance: See Section 2.4.4.

Vulnerability Sections: Are boilers and other tanks securely braced?
Guidance: Gas heaters or tanks with flammable or hazardous materials must be 
secured against toppling or sliding.

Vulnerability Sections: Are plumbing lines adequately supported and braced?
Guidance: Leaks in pressure pipes can cause damage over a large area. Protection 
of joints is especially important. See Section 2.4.4.

Vulnerability Sections: Is fire protection piping correctly installed and 
braced?
Guidance: See Section 2.4.4.


Vulnerability Sections: Is heavy electrical equipment adequately secured?
Guidance: Switch gear and transformers are heavy and sliding or movement failure 
can shut down the electrical system. See Section 2.4.4.

Vulnerability Sections: Is emergency generator and associated equipment secured 
against movement?
Guidance: The generator, muffler, batteries, day tank, and other electrical 
equipment may be necessary for emergency operation. See Section 2.4.4.

Vulnerability Sections: Are suspended lighting fixtures securely attached, 
braced, or designed to sway safely?
Guidance: Older suspended lighting fixtures have performed badly in earthquakes, 
and are an injury hazard. See Section 2.4.4.

Vulnerability Sections: Are light fixtures supported in an integrated ceiling, 
braced, and provided with safety wires?
Guidance: Light fixtures within a grid often fall when the grid is distorted, 
unless the fixtures are secured with safety wires. See Section 2.4.4.

Vulnerability Sections: Are the elevator cars, counterweights, and equipment 
anchored for seismic forces?
Guidance: Elevators are important for patient movement, particularly in an 
emergency. After strong shaking, elevators and shafts should be checked for 
safety before use. See Section 2.4.4.

Vulnerability Sections: Is at least one elevator in each wing connected to the 
emergency power system?
Guidance: Even if properly anchored and undamaged, the elevator needs power to 
enable vertical patient movement. See 2.4.4.

Vulnerability Sections: Is the bulk oxygen tank and associated equipment 
secured?
Guidance: The legs, anchorage, and foundations of large tanks need to be checked 
for adequacy.

Vulnerability Sections: Is nitrogen storage secured?
Guidance: Loose tanks may fall and break connections.

Vulnerability Sections: Are small natural gas lines to laboratories or small 
equipment vulnerable?
Guidance: Incompatibility of large and small lines and equipment movement can 
cause dangerous leaks.

Vulnerability Sections: Is the fire alarm system connected to a secondary power 
supply?
Guidance: This is also necessary to support daily operational needs, including 
lighting, heating, communications, etc.

Vulnerability Sections: Is significant fire alarm equipment secured against 
movement?
Guidance: Equipment can slide or topple, breaking connections. See FEMA 74.

Communications and IT Systems
Vulnerability Sections: Are communications components, including antennas, 
adequately braced and supported?
Guidance: Post-event communications are vital for post-earthquake operations. 
See FEMA 74.

Vulnerability Sections: Are plans in place for emergency communication systems, 
both within the facility and to outside facilities?
Guidance: Planning must consider likely post-earthquake conditions at the site 
and offsite.
[End table]




2.6 REFERENCES AND SOURCES OF ADDITIONAL INFORMATION

Note: FEMA publications may be obtained at no cost by calling (800) 480-2520, 
faxing a request to (301) 497-6378, or downloading from the library/publications 
section online at http://www.fema.gov. 

ASCE, 2003, Seismic Evaluation of Existing Buildings, ASCE Standard ASCE-31, 
American Society of Civil Engineers, Reston, VA.

ASCE, 2005, Minimum Design Loads for Buildings and Other Structures, ASCE 
Standard ASCE-7-05, American Society of Civil Engineers, Reston, VA.

ASCE, 2007, Seismic Rehabilitation of Buildings, ASCE Standard ASCE-41, Reston, 
VA.

Arnold, Christopher, and Michael Durkin, 1983, Hospitals and the San Fernando 
Earthquake, August 1983, Building Systems Development, Inc., Palo Alto, CA.

Behr, R.A., 2004, Design of Architectural Glazing to Resist Earthquakes, 
Proceeding, 13th World Conference on Earthquake Engineering, Vancouver, BC, 
August 2004.

Earthquake Engineering Research Institute (EERI), John F. Hall, Technical 
Editor, 1995, Chapter 11, Nonstructural Damage, Northridge Earthquake of 
January 17, 1994 Reconnaissance Report, Volume 1, Earthquake Spectra, 
Supplement C to Volume 11, April 1995, Earthquake Engineering Research 
Institute, Oakland, CA.

Federal Emergency Management Agency (FEMA), 1997a, NEHRP Guidelines for the 
Seismic Rehabilitation of Buildings, FEMA 273, Federal Emergency Management 
Agency, Washington, DC. 

FEMA, 1997b, NEHRP Commentary on the Guidelines for the Seismic Rehabilitation 
of Buildings, FEMA 274, Federal Emergency Management Agency, Washington, DC. 

FEMA, 2000, Prestandard and Commentary for the Seismic Rehabilitation of 
Buildings, FEMA 356, Federal Emergency Management Agency, Washington, DC. 

FEMA, 2002, Rapid Visual Screening of Buildings for Potential Seismic Hazards, A 
Handbook, FEMA 154, Federal Emergency Management Agency, Washington, DC. 

FEMA, 2003, Incremental Seismic Rehabilitation of Hospital Buildings, FEMA 396, 
Federal Emergency Management Agency, Washington, DC. 

FEMA, 2007, Designing for Earthquakes, A Manual for Architects, FEMA 454, 
Federal Emergency Management Agency, Washington, DC. 

Holmes, William T., 2002, Background and History of the Seismic Hospital 
Program in California, Proceedings, 7th U.S. National Conference on Earthquake 
Engineering, July 21-25, 2005, Boston, MA, Earthquake Engineering Research 
Institute, Oakland, CA.

Holmes, William T. and Lawrence Burkett, 2006, Seismic Vulnerability of 
Hospitals Based on Historical Performance in California, Proceedings, 8th U. S. 
National Conference on Earthquake Engineering, April 18-22, 2006, San Francisco, 
CA, Earthquake Engineering Research Institute, Oakland, CA.

Lew, H. S., E. V. Leyendecker, and R. D. Dikkers, 1971, Engineering Aspects of 
the 1971 San Fernando Earthquake, Building Science Series 40, U. S. Department 
of Commerce, National Bureau of Standards, Washington, DC.

Los Angeles County, Department of Health Services (LACDHS), 1994, Report to the 
California Hospital Building Safety Boards Special Forum on Damage to Health 
Facilities in the January 17, 1994 Northridge Earthquake, Minutes of the 
California State Hospital Building Safety Board, April 12, 1994, Office of 
Statewide Health Planning and Development, Sacramento, CA.

National Oceanic and Atmospheric Administration (NOAA), Leonard Murphy, 
Scientific Coordinator, 1973, San Fernando, California Earthquake of February 9, 
Volume 1, Part A, U.S. Department of Commerce, NOAA, Washington, DC.

Precast/Prestressed Concrete Institute (PCI), 1989, Architectural Precast 
Concrete, 2nd. Edition, PCI, Chicago, IL.

URS Consultants (URS), 1996, Northridge Earthquake Study of Seismic Design 
Factors for Hospital Non-Structural Components, Office of Statewide Health 
Planning and Development, Sacramento, CA.

Wang, M.L., 1987, Cladding Performance on a Full-Scale Test Frame, Earthquake 
Spectra, EERI, Vol. 3, No. 1, pp. 119-173, February 1987.

Wilson, Douglas, Kent Russell, Stephen Stanek, and David Swanson, 2005, Strong 
Medicine pp 26-29, Modern Steel Construction, Volume 45, Number 2, American 
Institute of Steel Construction, Chicago, IL.

Whole Building Design Guide, Seismic Design of the Building Envelope, National 
Institute of Building Sciences, Washington, DC, 2006.