Seismic White Paper SA12501SE
Effective August 2009
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Table of contents
Description
Part I Abstract and general overview. . . . . . . . . 2
Part II Seismic terminology and earthquake
engineering . . . . . . . . . . . . . . . . . . . . . . . 3
Part III Seismic requirements . . . . . . . . . . . . . . . 9
Part IV Test facility and test methodology . . . . . 16
Part V Shared responsibilities . . . . . . . . . . . . . . 18
Part VI Typical Eaton seismic equipment
specifications . . . . . . . . . . . . . . . . . . . . . 18
Part VII References . . . . . . . . . . . . . . . . . . . . . . . 20
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
About the authors
Mr. Eddie Wilkie graduated from North Carolina State University,
earning a Bachelor of Science degree in Mechanical Engineering.
Eddie has been employed with Eaton for 19 years. During that time,
he has held a variety of engineering and management positions.
Eddie has worked as a design engineer, design engineering manager, business operations manager and most recently as the division
engineering manager for Eaton’s Power Distribution Operations–
Americas. Eddie is currently responsible for coordinating Eaton’s
electrical equipment seismic program, which includes annual testing
and equipment certification.
Mr. Frederick M. Paul has spent over 31 years in various aspects of
the electrical industry. The last 11 have been as an application engineer with Eaton, covering the central valley of California, USA. Prior
to Eaton, he was involved in the sales and application of electrical
control and automation equipment. Earlier in his career, he was vice
president of operations for 11 years at an electrical contracting firm
in Southern California, USA.
Dr. Mostafa A. Ahmed has 37 years of extensive experience in
structural and mechanical design and construction of power
generating stations. He is a fellow engineer with the Westinghouse
Electric Company Nuclear Service division. He is skilled in civil and
mechanical engineering practices, dynamic analysis of equipment
and structures, and finite element analyses. Dr. Ahmed is an
expert in equipment seismic qualification and seismic testing.
He earned his bachelor of science degree in civil engineering
from Cairo University in 1971, and received his master of science
and doctorate in structural mechanics from the University of
Pittsburgh in 1981 and 1991. He is currently working in Shanghai,
China, as a technical advisor for the Westinghouse On-Shore
Engineering Organization.
Mr. Nathan M. Glenn, P.E., is a practicing Mechanical Engineer
specializing in equipment qualification. He is experienced in shock
and vibration testing, structural dynamics, electro-mechanical
analysis, and design. Nathan earned his Bachelor of Science degree
in Mechanical Engineering Technology from The Pennsylvania
State University, and received a Master of Science in Engineering
Mechanics specializing in Explosives Engineering from New Mexico
Institute of Mining and Technology. He is a registered Professional
Engineer in the state of Pennsylvania. Nathan is a Senior Engineer
with Westinghouse Electric Company. Currently he is responsible
for the qualification of nuclear power plant components and
systems. In addition to nuclear power plant equipment qualification,
Nathan provides seismic certification for electrical equipment used
in building code applications.
Part I
Abstract
Eaton Corporation is a global diversified industrial manufacturer
consisting of two sectors: Industrial and Electrical. Throughout
this document, all references to Eaton are in regards to Eaton’s
Electrical Sector.
Beginning with qualification testing in 1985, Eaton has led the
industry in seismic certification of electrical equipment for use in
facilities across the continental United States. Eaton was the first
electrical equipment supplier to employ seismic simulation testing
for equipment seismic certification.
2
EATON CORPORATION www.eaton.com
For more than 20 years, Eaton has had a comprehensive program
focused on designing and manufacturing electrical distribution
and control equipment capable of meeting and exceeding the
seismic load requirements of the Uniform Building Code姞 (UBC),
the California Building Code (CBC), and the Building Officials and
Code Administrators姞 (BOCA) International, Inc. The entire program has been updated to demonstrate compliance with the 2006
International Code Council (ICC) and the 2006 International Building
Code (IBC) unified seismic requirements. This also includes
the 2007 CBC.
Eaton recognized that the most direct and proven method of
assuring seismic performance of electrical equipment is through
simulation testing via triaxial or biaxial shake tables. Representative
configurations for each of Eaton’s product lines were designed
and built for seismic testing. Considerable attention was given to
selecting test units that conservatively represented the entire family
of products being certified.
Test units were initially subjected to independent 0.2g resonant
searches in each of the three principal axes prior to being subjected
to a series of seismic simulation tests. The test assemblies were
proven to meet or exceed the seismic performance requirements
and remain operational immediately after the seismic event. This
paper provides a summary of the efforts that were involved in the
achievement of this objective.
Background
Although the need for seismic-capable electrical equipment is
known, there is a lack of understanding of how to comply with
current code requirements. The 2006 International Building Code
(IBC) and the 2007 California Building Code (CBC) both emphasize
building design requirements with limited information for seismic
certifications of equipment. Electrical equipment and distribution
system components are treated as non-structural attachments to
the building.
Since seismic testing contains many special terms and formulations,
this paper begins with the basics of seismic terminology and
earthquake engineering, then proceeds with addressing the specific
factors involved with meeting the requirements of the IBC and CBC.
The 2006 IBC seismic requirements, along with associated codes
derived from the IBC, will be addressed, explaining how they relate
to Eaton’s previous and current test programs. The most stringent
requirements of these codes (IBC and CBC) will be presented as
they apply to electrical distribution and control equipment and
will be combined to formulate a single reference for purposes
of evaluation.
To properly define the acceptability of the equipment to the
specified codes, it is necessary to present the equipment seismic
requirements and the equipment seismic capability data on the
same technical basis. For this purpose, the use of the “response
spectrum” concept will be introduced. To simplify the application for
the user, the seismic capability of all of Eaton’s equipment has been
established to the same basic levels and requirements.
The equipment is considered acceptable, or granted a “seismic
certificate,” if it can withstand the seismic event and perform its
function immediately afterward. Eaton participates in a cooperative
effort with the user, building designer, and installer to ensure
that the equipment is mounted properly to a foundation that can
withstand the effects produced by an earthquake.
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
General overview
Eaton’s electrical distribution and control equipment has undergone
seismic simulation tests and meets or exceeds performance
requirements as identified in the 2006 IBC1 and the 2007 CBC2. It
is important to note that Eaton has tested its equipment using the
most typical mounting methods. All Eaton floor-mounted equipment
has been seismically tested as free-standing units, with no lateral
supports at the top that are affixed to adjacent walls or structures.
This allows users to either secure it from the base alone or in combinations of base and top lateral supports. It must be recognized
that equipment tested with top lateral supports is not certified to the
same levels as free-standing items. Eaton has shown by simulation
testing that equipment seismic capabilities are reduced by more
than a factor of two when mounted at the base only as compared to
securing with lateral supports located at the top of the equipment.
Complete and proper certification of equipment to achieve maximum flexibility for the user must include testing of equipment as
stand-alone items. Eaton equipment that is certified to higher levels
when installed with top lateral supports is specifically indicated on
Eaton’s seismic certificates.
Eaton is highly experienced in the design, manufacture, and seismic
certification of electrical distribution equipment to meet the most
rigorous seismic standards. As new products are developed, or
existing products are modified, Eaton continues to verify the seismic
acceptability of nearly all lines of electrical equipment for applications requiring certification to the IBC and CBC.
Over a period of more than 20 years, over 100 different assemblies,
representing many product lines, have been successfully tested
and verified to seismic levels higher than the maximum seismic
requirements specified in the IBC and CBC. The equipment maintained structural integrity and demonstrated the ability to function
immediately after the seismic simulation tests. This achievement, an
industry first, is consistent with the Eaton commitment to produce
the most reliable equipment that exceeds both present and future
requirements. Testing was performed on simulation tables
at Wyle Test Laboratory in Huntsville, Alabama, along with the
former Westinghouse Advanced Energy Systems Division in
Pittsburgh, Pennsylvania.
The general concepts for seismic test methodology, ANSI/IEEE姞
Standard 344-1987, and the applicable procedures from ANSI/IEEE
C37.81—Guide for Seismic Qualification of Class 1E Metal-Enclosed
Power Switchgear Assemblies—were consulted.
The equipment was subjected to the following vibration excitation
and seismic simulation testing:
1. Initial resonance searches in all three principal directions in
the frequency range of 1 to 50 Hz, using sine sweep motion
at the base of the test units, with a sweep rate of 1.0 octave
per minute. Peak acceleration of the sine wave was designed
around 0.2g. (Some resonance sweep tests have been
conducted up to 100 Hz.)
Seismic White Paper SA12501SE
Effective August 2009
Nearly all of Eaton’s electrical assemblies have been tested and
were found acceptable when evaluated to IBC and CBC seismic
requirements. Eaton continues to lead the industry in using
simulation testing to ensure conformance of electrical distribution
and control equipment to the most current codes. (See Part III.)
Establishing the equipment seismic capability is only the first step.
A seismically qualified mounting base with anchors or welds is
required to hold the equipment safely to the supporting structure.
(See Part V.)
Part II
Seismic terminology and earthquake engineering
Earthquakes occur in most every region around the world.3 (See
Figure 1.) As reported by the U.S. Geological Survey, in 2007 alone,
55 earthquakes greater than 6.0 were recorded around the world.
These resulted in 681 reported deaths and widespread damage to
structures, buildings, and equipment with damage estimates in the
billions of dollars.
The May 12th, 2008 earthquake in Chengdu, China, exceeded 6.9
and caused a major tragedy of more than 69,000 deaths and
resulted in several thousands of people missing. The problems
were further compounded due to the delays in restoring power
and service to the affected areas.
To restore function of emergency management facilities as quickly
as possible, public officials have revised building codes to mandate
improved seismic design. This includes not only buildings, but also
the electrical and mechanical equipment contained therein, as well
as machinery necessary for safe occupancy and normal operation.
Eaton has taken the unique step of performing seismic simulation
tests on various lines of distribution and control products. Users can
be sure that Eaton’s electrical equipment has been designed and
tested to exceed the requirements as identified by the IBC and CBC.
For purposes of understanding, it is important to review a few of the
basic principles of earthquake engineering. From an analytical perspective, it is not easy to quantify the severity of an earthquake.
Most news reports refer to the magnitude of the earthquake in
terms of the open-ended Richter scale. Although most people have
heard of the Richter scale, the understanding is limited. The original
definition is:4
Richter magnitude is M, where M = log10(A)
Where A is equal to the trace amplitude (in microns) of a
Wood-Anderson Seismograph having magnification of 2800,
natural period of 0.8 seconds, a damping coefficient of 80%,
located on firm ground, at a distance of 62.5 miles (100 km)
from the earthquake epicenter.
Since 1000 microns are equal to 1.0 millimeter, and log10 (1000)
is equal to 3, M could then be redefined as:
M = 3 + log10(trace amplitude in mm)
2. Seismic simulation testing using 30-second-long random
multifrequency inputs imposed simultaneously and
measured at the base of the test cabinets in all three
principal directions. The base acceleration levels were
increased further to encompass the combined code
requirements, and additional testing was performed to
demonstrate margin beyond code requirements.
1
2
3
4
International Code Council, International Building Code.
California Building Standards Commission, California Building Code.
Newmark, Fundamentals of Earthquake Engineering, p. 252.
Ibid., p. 217.
EATON CORPORATION www.eaton.com
3
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
To determine the magnitude of an earthquake in terms of Richter
Scale M, one could proceed as follows:
Table 1. Relationship of Earthquake Magnitude to
Other Parameters
Maximum7
Earthquake
Ground
Magnitude M Acceleration
(Richter Scale) (% g)
Duration of 7
Strong
Motion
(Seconds)
Length of8 Equivalent9
Fault Slip Energy
(Miles)
(Tons of TNT)
8.5
50
73
530
8
50
43
190
13 million
7.5
45
30
70
2.2 million
The result is the magnitude (M) of an earthquake on the
Richter scale.
7
37
24
25
400,000
6.5
29
18
9
70,000
Note: It is important to note that for a change of one unit in the Richter scale,
M means a change of 10 in the amplitude of the motion of the earthquake.
6
22
12
5
13,000
5.5
15
6
3
2200
5
9
2
2
400
1. Measure the amplitude of the Wood-Anderson Seismograph
in millimeters at a location 62.5 miles from the earthquake’s
epicenter.
2. Take common logarithm of the amplitude.
3. Add 3 to it.
To relate the magnitude (M) to the energy radiated by the earthquake, Gutenberg and Richter developed the following relationship5:
70 million
log10(Es) = 11.8 + 1.5 M
Where Es is the seismic energy of the earthquake and M is the
Richter magnitude.
A one megaton bomb releases about 5x1022 ergs. If all of the energy
could be converted into seismic energy (typically only about 2%
would be), it would correspond to a magnitude 7.3 earthquake6.
Table 1 relates the earthquake magnitude to other relevant parameters. A change of one unit in the magnitude M means an increase
of 1.5 in the right-hand side of the equation, resulting in a change of
32 in the total energy of the earthquake, Es, since log10 (32) = 1.5.
Although the magnitude of the earthquake is a direct measure of its
severity, there are a number of difficulties in using it for equipment
design. Specifically, they include:
1. Maximum displacement alone does not provide necessary
information about the frequency content of the motion. Due
to the effects of amplification, equipment is most susceptible
to damage when the earthquake motion contains the equipment’s inherent natural frequencies.
2. Maximum displacement is not necessarily a good measure
of the total amount of energy the equipment is subjected to
during the earthquake. Velocity is a better indicator of
the energy.
3. Maximum displacement is not a good measure of the force
the equipment will experience. Acceleration shows a better
correlation to the resultant seismic forces on the equipment
mounted inside buildings or structures.
4. Seismographs are normally tuned to frequencies in the 1
to 2 Hz range. This is adequate for measuring the magnitude
of the earthquake, but does not provide accurate information
about the frequencies typically translated to buildings
and equipment.
Figure 1. Seismicity of the Earth, 1961–1967
4
EATON CORPORATION www.eaton.com
Table 2. Modified Mercalli Intensity Scale (abridged and
Rewritten by C. F. Richter10)
Intensity11 Definition
1
Not felt. Marginal and long period of large earthquakes.
2
Felt by persons at rest, on upper floors, or favorably placed.
3
Felt indoors. Hanging objects swing. Vibration like passing of light trucks.
Duration estimated. May not be recognized as an earthquake.
4
Hanging objects swing. Vibration like passing of heavy trucks; or
sensation of a jolt like a heavy ball striking the walls. Standing motor cars
rock. Windows, dishes, doors rattle. Glasses clink. Crockery clashes. In the
upper range of 4, wooden walls and frames crack.
5
Felt outdoors; direction estimated. Sleepers awakened. Liquids disturbed,
some spilled. Small unstable objects displaced or upset. Doors swing, close,
open. Shutters, pictures move. Pendulum clocks start, stop, change rate.
6
Felt by all. Many frightened and run outdoors. Persons walk unsteadily.
Windows, dishes, glassware broken. Knickknacks, books, and so on, off
shelves. Pictures off walls. Furniture moved or overturned. Weak plaster
and masonry D cracked. Small bells ring (church, school). Trees, bushes
shaken visibly, or heard to rustle.
7
Difficult to stand. Noticed by drivers of motor cars. Hanging objects
quiver. Furniture broken. Damage to masonry D including cracks. Weak
chimneys broken at roof line. Fall of plaster, loose bricks, stones, tiles,
cornices, unbraced parapets, and architectural ornaments. Some cracks
in masonry C. Waves on ponds; water turbid with mud. Small slides and
caving in along sand or gravel banks. Large bells ring. Concrete irrigation
ditches damaged.
8
Steering of motor cars affected. Damage to masonry C; partial collapse.
Some damage to masonry B; none to masonry A. Fall of stucco and some
masonry walls. Twisting, fall of chimneys, factory stacks, monuments,
towers, elevated tanks. Frame houses moved on foundations if not bolted
down; loose panel walls thrown out. Decayed piling broken off. Branches
broken from trees. Changes in flow or temperature of springs and wells.
Cracks in wet ground and on steep slopes.
9
General panic. Masonry D destroyed; masonry C heavily damaged, sometimes with complete collapse; masonry B seriously damaged. General
damage to foundations. Frame structures, if not bolted, shifted off
foundations. Frames cracked. Conspicuous cracks in ground. In alleviated
areas, sand and mud ejected, earthquake fountains, sand craters.
10
Most masonry and frame structures destroyed with their foundations.
Some well-built wooden structures and bridges destroyed. Serious
damage to dams, dikes, embankments. Large landslides. Water thrown
on banks of canals, rivers, lakes, and so forth. Sand and mud shifted
horizontally on beaches and flat land. Rails bent slightly.
11
Rails bent greatly. Underground pipelines completely out of service.
12
Damage nearly total. Large rock masses displaced. Lines of sight and
level distorted. Objects thrown into the air.
5
6
7
8
9
10
11
Wiegel, Earthquake Engineering, p. 31 (Ref. 8).
Newmark, Fundamentals of Earthquake Engineering, p. 252 (Ref. 7).
Wiegel, Earthquake Engineering, p. 79, Table 4.3 (Ref. 8).
Wiegel, Earthquake Engineering, p. 77, Table 4.1 (Ref. 8).
Newmark, Fundamentals of Earthquake Engineering, p. 218 (Ref. 7).
Newmark, Fundamentals of Earthquake Engineering, Appendix 2 (Ref. 7).
Intensity is frequently represented by Roman numerals.
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
To eliminate many verbal repetitions in the original scale, the following convention has been adopted. Each effect is named at that level
of intensity at which it first appears frequently and characteristically.
Each effect may be found less strongly, or in fewer instances, at the
next lower grade of intensity; more strongly or more often at the
next higher grade. A few effects are named at two successive
levels to indicate a more gradual increase.
Masonry A, B, C, and D. To avoid ambiguity of language, the quality
of masonry, brick or otherwise, is specified by the following
lettering (which has no connection with the conventional
Class A, B, C construction).
Masonry A. Good workmanship, mortar, and design; reinforced,
especially laterally, and bound together by using steel, concrete,
and so forth; designed to resist lateral forces.
Seismic White Paper SA12501SE
Effective August 2009
Although accurate and readily available soon after the event, these
records are not ideal for translating requirements to equipment
design and seismic certification. For example, note that the
El Centro, California, earthquake acceleration magnitude reaches
0.3g several times, and is consistently above 0.1g, while the maximum peak-to-peak displacement is about 30 cm. For the Mexico
City earthquake, the acceleration magnitude is generally about
0.01g, with one peak at about 0.02g—only about 10% of the
El Centro acceleration levels.
The maximum peak-to-peak destruction displacement of the Mexico
City earthquake was 60 cm, or about twice the El Centro displacement value. Noting the difference in the time scale, one immediately
realizes that the Mexico City earthquake motions are characterized
by much lower frequencies than the El Centro event.
Masonry B. Good workmanship and mortar; reinforced, but not
designed to resist lateral forces.
0.3 g
0.2 g
0.1 g
0
-0.1 g
-0.2 g
-0.3 g
Masonry C. Ordinary workmanship and mortar; no extreme
weaknesses like failing to tie in at corners, but neither reinforced
nor designed against horizontal forces.
Masonry D. Weak materials, such as adobe; poor mortar;
low standards of workmanship; weak horizontally.
In addition to the magnitude of the earthquake, which measures the
amount of energy released, another parameter, the intensity, is used
to measure the local destructiveness of earthquakes. Therefore,
one earthquake will have a single magnitude, but a number of different intensities, depending on the location of the observers.12 Most
intensity scales are based on personal and subjective observations,
including “scary feeling” and the ability (or inability) to remain
standing, as well as the sorts of property damage that occurred.
Although quantitative and based on actual damage effects, a review
of Table 2, the Modified Mercalli (mm) scale13, reveals that it is too
subjective for use in electrical equipment design and qualification.
Despite its limitations, the intensity can be quite useful in areas
where there are no seismic instruments available to record the
earthquake, and it may provide the only consistent way to interpret
the diaries and other written accounts of historical earthquakes.14
When available, the most accurate descriptions of actual earthquake motions are the time history records. A time history record
is simply a graphical recording of the earthquake motion (it can be
in terms of displacement, velocity, or acceleration) as a function of
time. Figures 2 and 3 illustrate time history records for two different
earthquakes.15
South
t
North
20
cm sec-1
0
South
20
North
40
20
cm
10
South
Acceleration
t
Velocity
t
0
10
North
0
5
10
Displacement
15
20
Time, seconds
25
30
Figure 2. El Centro, California, Earthquake of May 18, 1940,
NS Component16
Because acceleration is a function of displacement times the square
of the natural circular frequency (for sinusoidal motions), the dominant frequencies of the El Centro earthquake are four to five times
those of the Mexico City earthquake. This illustrates that while the
time history is very accurate for any one earthquake, it is difficult to
use as the basis for generalizations about other earthquakes.
12
13
14
15
16
Newmark, Fundamentals of Earthquake Engineering, p. 217 (Ref. 7).
Ibid., Appendix 2.
Ibid., p. 218.
Ibid., p. 227.
Ibid., p. 227.
EATON CORPORATION www.eaton.com
5
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
The question arises related to the adequacy of the time history to
accurately represent the earthquakes shown in Figures 2 and 3.
Because the acceleration record for the test contains several peaks
in the range of 2 to 3g, there are enough peak accelerations and
inertial forces to satisfy the requirements. Similarly, the peak-to-peak
displacements are in the range of 60 to 75 cm for the test, which
would appear to be sufficient to meet even the Mexico City
displacement levels.
On the basis of amplitude alone, it appears that the shake table time
history (Figure 4) meets both actual earthquake events (Figures 2
and 3). However, there are two critical factors not yet addressed: (a)
frequencies present in the required motion versus the frequencies
present in the test motion, and (b) the inherent equipment damping.
It has already been shown that the frequency content represents
a significant difference in contrasting Figures 2 and 3. Similarly,
frequency is also critically important in establishing equipment
certification. The reason is basic: each piece of electrical equipment
has its own natural frequency that produces maximum amplification.
For larger assemblies, 4 to 6 Hz is typically the minimum natural
frequency. If the earthquake has significant 4 to 6 Hz motion, the
equipment will respond accordingly, amplifying or resonating with
the earthquake motion. If the earthquake has substantial 10 to 12
Hz motion, the equipment will be too flexible to keep up with the
higher frequency, thus, it will tend to sit still or attenuate the earthquake motion. If the earthquake has a significant amount of 1 to 2
Hz motion, the equipment will rigidly follow the motion of the floor,
neither amplifying nor attenuating. Figure 5 is a resonance curve
and illustrates the three regions of equipment response as a
function of the ratio of the equipment natural frequency to the
input motion frequency.
Another important factor that time histories do not address is
equipment damping. For simplicity, equipment damping is often
expressed as a ratio (C/Cc) of the actual equipment (C) damping
to that of a critically damped system (Cc). Frequently, the ratio is
expressed as the percent of critical damping. As one can see from
Figure 5, the damping property of the equipment limits the total
amplification that the equipment will experience at resonance. With
no damping, the equipment response amplification at resonance
increases without bound. With a damping coefficient of 12.5%, the
equipment response will not exceed four times the input motion,
as can be seen in Figure 5.
This resonance curve is helpful in understanding the equipment
response to earthquakes. However, these curves, based on continuous sinusoidal input motions, are too conservative for representation
of actual earthquakes, which have not one, but a number of different
frequencies. Additionally, these frequencies are discontinuous,
starting and stopping several times during the course of the
seismic event.
0.02 g
0.01 g
0
-0.01 g
-0.02 g
10
cm sec-1 0
-10
cm 40
30
20
10
0
-10
-20
-30
Acceleration
Velocity
Displacement
(Typically the ground displacements
are incredibly large due to small errors
in the base line for the accelerogram)
0
10
20 30
40 50 60 70
80 90 100 110 120 130 140
Time, seconds
Figure 3. Mexico City Earthquake of July 6, 1964, NS Component17
Displacement
(cm)
CAL
2.5" Peak/
25 Lines
5"/Line
Acceleration
(g)
CAL
1g/1 Line
20 Seconds
Figure 4. Shake Table Time Histories for Equipment Test
5
Equipment Response / Input Motion
Finally, the last concern in using time history can be illustrated as
follows. Figure 4 shows the time history records (both displacement
and acceleration forms) for a shake table test run.
F
FF= 0
4
F = 0.125
FF
3
F = 0.25
FF
2
F = 0.50
FF
1
F
F F= 1.00
0
0
1
2
Equipment
Follows
Equipment
Amplifies
Equipment
Attenuates
Input
Motion
Input
Motion
Input
Motion
3
Frequency Ratio
Equipment Response per Unit Input Motion as a Function of Frequency Ratio:
Equipment Natural Frequency
Input Motion Frequency
Figure 5. Resonance Curves for Continuous Sine Motion
17 Newmark, Fundamentals of Earthquake Engineering, p. 227.
6
EATON CORPORATION www.eaton.com
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
10
9
8
7
6
5
4
Sinusoidal Harmonic Motion
X = A sin wt = Displacement
X = dx = A w cos wt = Velocity
dt
X = dx = – A w 2 sin wt = Acceleration
dt
3
Where W = 2 › x Frequency
Spectrum Dip—Not
Important Because
Frequency Is Not an
Equipment Natural
Frequency
C
M
X
Figure 6. Basic Vibration Equations18
Because of these difficulties in universally applying the time history
form, engineers have developed a method of comparing earthquake
response motions as a function of frequency, rather than time.
This is called the acceleration response spectrum method.
The acceleration response spectrum for any time history is a plot of
the maximum responses of a series of linear, single-degree, freedom oscillators (one spring, one mass, one dashpot that can move
linearly along only one axis) mounted on a surface moving according
to the time history being studied. Figure 6 depicts one such simple
oscillator and its basic equations of motion. Typically, the response
spectra are plotted over the 1 to 35 Hz frequency range in no less
than 16 steps, not exceeding one-third octave. (For example, 1.0,
1.26, 1.6, 2.0, 2.5, 3.2, 4.0, 5.0, 6.3, 8.0, 10.0, 12.7, 16.0, 20.0,
25.4, and 32.0 Hz.)
The responses of these oscillators are easily determined in real
time, with digital computers and fast spectrum analyzers in the
test laboratory. However, the complex and difficult task of communicating earthquake requirements and equipment capabilities has
become a routine matter of showing that the equipment capability
response spectrum, as produced by shake table test, envelops the
ground-level seismic requirements. During this test, the response
spectrum envelops the applicable portion of the location where
the equipment is to be installed. The applicable portion means
that enveloping is required at all equipment frequencies. Figure 7
shows a typical test response spectrum (TRS) enveloping the
applicable portion of the required response spectrum (RRS).
Note that enveloping does not occur at 4.5 Hz, which is acceptable, because this was not a resonant frequency of the equipment.
Enveloping is only necessary at the natural frequencies of the
equipment. This illustrates the value of the simple frequency sweep
test to identify the lowest natural frequencies and damping factors
associated with any equipment seismic test certification program.
Figure 8 illustrates a more useful form for engineers. The peak
magnification (alignment of the equipment natural frequency with
the earthquake frequency), Q, as a function of the damping. Each
curve represents a different type of earthquake motion. The “lowest” curve for “random motion” (all frequencies present to an equal
extent) is generally the most like the ground motion during an actual
earthquake. Because most electrical equipment is mounted on a
rigid surface or inside another structure, the original earthquake
motion is “filtered” by that structure. The equipment, therefore,
experiences so-called “quasi-resonance” effects as the structure to
which it is mounted alternately amplifies and attenuates the earthquake motion according to its inherent characteristics. The result is
the equipment peak amplification lies somewhere between the two
extremes—“lower level random motion” response and “higher level
continuous sine“ response.
18 Beer, Vector Mechanics for Engineers: Statics and Dynamics, p. 771.
1.0
0.9
0.8
0.7
0.6
0.5
Required Response
Spectrum
(RRS)
Zero Period
Acceleration
= Maximum
Floor Motion
0.4
0.3
0.2
0.1
1
2
3
4
5 6 7 8 9 10
20
30 40 50
Frequency Hz
70 90
60 80 100
Figure 7. Equipment Qualification by the Response Spectrum
Method When TRS “Envelopes” the RRS for All Equipment
Natural Frequencies
40
Continuous
Sine Motion
Q=100/(2c/cc)
30
Q Factor, Magnification Number
k
Acceleration (g)
2
Linear SingleDegree-of-Freedom
Oscillator
Zero Period
Acceleration
= Maximum
Table Test
Motion
Test Response Spectrum
(TRS)
10 Cycles/Beat
20
5 Cycles/Beat
Typical
Earthquake
Ground Motion
Random
Vibration
Q=
X10
X6.8
10
100
2c/cc
X5.6
X3.1
0
0
5
10
15
c/cc, Percent of Critical Damping
Figure 8. “Q” Curves—Vibration Magnification vs. Percent of
Critical Damping
EATON CORPORATION www.eaton.com
7
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
 CAUTION!
10
IT IS IMPORTANT TO VERIFY THAT THE RRS AND THE TRS ARE
BASED ON AND PLOTTED AT THE SAME DAMPING FACTOR
BEFORE MAKING THE COMPARISON.
The energy content of an earthquake can best be defined via the
RSC. This curve must be carefully understood and carefully applied.
It is a theoretical curve computed for application to a system or
equipment. Typical curve sets are shown in Figure 9.
The only spectral acceleration magnitude that is directly related to
the earthquake event is the maximum response of rigid systems.
Within earthquake engineering, it is understood that rigid systems
are those with no resonance frequencies below 33 Hz and are
considered to have a zero period of acceleration. Because a rigid
system will not amplify the motion of the earthquake, its maximum
response acceleration is equal to the maximum acceleration of the
earthquake time history. As a result, the part of the RSC at the
higher frequencies, referred to as zero period acceleration (ZPA),
directly defines the maximum acceleration of the earthquake time
history. It does not depend on the damping properties of the equipment. Thus, no matter what the equipment damping, the ZPA is
always the same, and is equal to the maximum acceleration in the
earthquake time history.
All other spectral accelerations are possible only if the equipment
has a dominant resonant frequency that aligns with the frequency
on the response spectrum curve (RSC). Thus, this curve tells the
engineer that it is possible for a piece of equipment to experience
the spectral acceleration defined in the curve, if the equipment has
a dominant resonance frequency matching the frequency on
the RSC.
It is important to understand that the damping properties of a
system are a direct indication of the system’s ability or inability
to dissipate the earthquake energy.
To further explain the effect of damping properties on the seismic
response of systems, assume that two enclosures were similarly
designed and built, but with one exception: One enclosure is a
welded structure, while the other is a bolted structure. Aside from
this difference, the enclosures are identical in design, mounting,
and weight. Should both be subjected to an earthquake motion, the
structural elements in the bolted cabinet will move relative to each
other, producing friction and noise. Ultimately, these effects within
the bolted enclosure result in increased dissipation of the energy
produced by the seismic event as compared to the welded
enclosure. The bolted enclosure will dampen the energy much
quicker than the welded version, resulting in reduced time for
the seismic response to build up.
For this reason, the RSC is usually computed and plotted for different
damping properties—typically 1%, 2%, 3%, 5%, 7%, and so forth. It
must be recognized that all resultant plots on the RSC are produced
as a result of the same earthquake time history input motion
(see Figure 9). It should be apparent that the result and response
will be higher for systems with lower damping properties, and lower
for systems with higher damping. A very useful rule is: The higher
the damping coefficient of the equipment, the lower its response
curve; the lower the damping coefficient of the equipment, the
higher its response curve.
8
EATON CORPORATION www.eaton.com
Acceleration (g)
Although the Richter scale M is of good use in describing earthquake strength, it does not identify the energy content of the
earthquake or its potential to damage structures and equipment.
Basically, the Richter scale M is a displacement indicator rather
than an energy or acceleration indicator.
5% Damping, 1.4g
Peak Acceleration
1.0
7% Damping, 1.25g Peak Acceleration
Zero Period Acceleration (ZPA), Equal to 0.6g
0.1
0.1
1.0
10
100
Frequency Hz
Figure 9. Response Spectrum Curve
Switchgear
Assembly
90"
4 x 36"
86"
Front-to-Back
Base Motion
Side-to-Side
Base Motion
Vertical
Base Motion
Figure 10. Triaxial Shake Table
10
Front-to-Back Seismic Base Input
Side-to-Side Seismic Base Input
Vertical Seismic Base Input
Acceleration (g)
Now that the basics of earthquake engineering have been presented,
several key elements that are very useful in understanding the nature
of earthquakes, time history, the response spectrum curve (RSC), and
the potential effect on electrical enclosures can be discussed further.
2% Damping, 2.4g Peak Acceleration
1.0
0.1
0.1
1.0
10
Frequency Hz
Figure 11. Response Spectrum Curve, 5% Damping Curves
100
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
To further demonstrate the use of the RCS, consider this example:
Multiple switchgear sections are mounted to a triaxial shake table
(Figure 10). The section of equipment is then subjected to the base
seismic response spectrum shown in Figure 11.
The switchgear assembly has a dominant natural frequency of 6 Hz
in the side-to-side direction, 10 Hz in the front-to-back direction, and
55 Hz in the vertical direction. The assembly is a bolted structure
with a 5% damping coefficient.
If the switchgear assembly is subjected to test levels that could
produce the RRS, shown in Figure 11, one can quickly determine
that the enclosure will amplify the base motion and could experience
a 1.5g acceleration in the side-to-side, a 2.0g in the front-to-back, and
a 0.9g in the vertical direction. The resultant forces and moments on
the structural elements and internal components can now be
computed to confirm that the enclosure and components contained
therein will maintain their structural integrity.
To design the enclosure foundation, apply these accelerations at the
cabinet’s center of gravity (C.G.), multiply them by the total mass of
the equipment, and increase them with factors as appropriate
to account for design margin. Thus, cross-coupling effects and closemode contributions are taken into account. Next, determine the
resultant moments, forces, and shear on the mounting bolts or welds.
Only the acceleration associated with the dominant natural
frequencies of the enclosure need to be selected from the spectrum
curves. For example, the front-to-back direction RRS has a peak
spectral acceleration (3.2g) in the frequency range 1.5 to 3 Hz.
This acceleration has little or no effect on the enclosure, because
the front-to-back frequencies of 10 Hz do not coincide with this
frequency range (1.5 to 3 Hz).
A beneficial engineering practice is to design equipment with
natural frequencies that do not align with the frequencies found
in the earthquake time history.
Most earthquakes tend to include low frequencies (1 to 3 Hz).
Eaton understood this phenomenon and designed equipment with
resonance frequencies above those levels. All Eaton equipment is
designed with frequencies above 3.2 Hz, which serves to minimize
the amplification.
This is further discussed in the next section (Part III) where the development of seismic requirements for electrical equipment is considered.
Part III
Seismic requirements
Consistent with Eaton’s commitment to produce equipment that
exceeds present and future code requirements, essentially all
engineered-to-order assemblies and standard assembly products
have been designed, manufactured, and tested to meet rigorous
seismic requirements.
International Building Code (IBC) 2006
On December 9, 1994, the International Code Council (ICC) was
established as a nonprofit organization dedicated to developing a
single set of comprehensive and coordinated construction codes.
The ICC founders—the Building Officials and Code Administrators
(BOCA), the International Conference of Building Officials (ICBO),
and the Southern Building Code Congress International (SBCCI)—
created the ICC in response to technical disparities among the three
recognized model codes in use at the time. The ICC offers a single,
complete set of construction codes without regional limitations—the
International Building Code (IBC).
Since the establishment of the ICC and the issuance of the 2000
IBC (Rev-0), there have been two revisions: the first was published
in 2003; the second in 2006. There were no substantial changes in
the code that affected the validity of the 2003 IBC Eaton seismic
certifications issued prior to the revisions. This paper addresses the
requirements of the 2006 IBC, hereafter referred to as the IBC.
Seismic White Paper SA12501SE
Effective August 2009
According to Chapter 16 of the IBC, “Structure Design,” the seismic
requirements of electrical equipment in buildings may be computed
with two pieces of information: 1) a determination of the maximum
ground motion at the site; 2) an evaluation of the equipment mounting and attachment inside the building or structure. This data can
then be evaluated to develop the appropriate seismic test requirements. The ground motion, the in-structure seismic requirements
of the equipment, and the seismic response spectrum requirements
are discussed below.
A. Ground motion
According to the IBC, the first and most important step in the process
is to determine the maximum considered earthquake spectral response
acceleration at short periods of 0.2 seconds (Ss) and at a period of 1.0
second (S1). These values are determined from a set of 24 spectral
acceleration maps contained in the International Building Code and
include the numerous contour lines indicating the severity of the
earthquake requirements at a particular location. Great care has been
taken in selecting the maximum values for the contour lines.
For example, the maps indicate low to moderate seismic requirements for most of the continental United States of America (USA)
with exceptions being the West Coast (State of California) and the
Midwest (New Madrid area). The seismic levels in the New Madrid
area are approximately 30% higher than the maximum levels of the
West Coast.
The maps also suggest that the high seismic requirements in both
regions, West Coast and Midwest, quickly decrease away from the
high magnitude fault areas. These high requirements are limited to a
relatively local area along the fault lines. Just a few miles away from
this area, only a small percentage of the maximum requirements
are indicated.
To provide a realistic estimate of the seismic requirements for the
continental USA, attention will initially be focused on the West
Coast, where the values noted exceed the rest of the continental
USA, with the exception of the New Madrid area. The New Madrid
area seismic requirements will be addressed separately to prevent
imposing unreasonable requirements on the rest of the USA.
The worst-case conditions are formulated by selecting the mapped
Maximum Considered Earthquake Spectral Response Acceleration at
short periods of 0.2 seconds (Ss), equal to 285% gravity, and at a 1.0
second period (S1), equal to 124% gravity. These accelerations will
be used to calculate the Adjusted Maximum Considered Earthquake
Spectral Response Accelerations. This combination of Ss and S1
is identified using the contour maps in Figures 12 and 13. These
numbers are the maximum values for the entire country, except for
the New Madrid area. These particular sites are on the border of
California and Mexico (S1) and in Northern California (Ss). Figures 12
and 13 are developed for Site Class B, at 5% of critical damping.
To determine the maximum considered earthquake ground motion
for most site classes (A through D), the code introduces site coefficients. When these are applied against the location-specific site
class, this produces the adjusted maximum considered earthquake
spectral response acceleration. The site coefficients are defined as
Fa at 0.2 seconds short period and FV at 1.0 second period. From the
tables in the IBC, the highest adjusting factor for SS (≥ 1.25) is equal
to 1.0 and 1.5 for S1 (> 0.5). It is important to note that the CBC
mandates the use of site class D for California.
Therefore, the adjusted maximum considered earthquake spectral
response for 0.2 second short period (SMS) and 1.0 second period
(SM1), adjusted for site class effects, is determined from the
following equations:
SMS = Fa SS = 1.0 x 2.85g = 2.85g
SM1 = FV S1 = 1.5 x 1.24g = 1.86g
ASCE 7-05 (American Society of Civil Engineers) provides a plot
showing the final shape of the design response spectra of the
ground (Figure 14). ASCE 7-05 is referenced throughout the IBC
as the source for numerous structural design criteria.
EATON CORPORATION www.eaton.com
9
Seismic White Paper SA12501SE
Effective August 2009
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Figure 12. Maximum Considered Earthquake Ground Motion for Region 1 of 0.2 sec. Spectral Response Acceleration
(5% of Critical Damping), Site Class B, SS
10
EATON CORPORATION www.eaton.com
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
Figure 13. Maximum Considered Earthquake Ground Motion for Region 1 of 1.0 sec. Spectral Response Acceleration
(5% of Critical Damping), Site Class B, S1
EATON CORPORATION www.eaton.com
11
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
Spectral Response Acceleration Sg
(SDS)1.90g
1.24g
It is common to over test by factors of two to three times if the
low end of the spectra accommodates this acceleration component.
Through testing experience and data analysis, the seismic acceleration at 1.0 Hz is taken equal to 0.7g, which will ensure that the
seismic levels are achieved well below 3.2 Hz. This yields a more
vigorous test over a wider range of seismic intensities.
In developing the seismic requirements above, it is important to
recognize the following:
SD1
0.76g
0.131
(7.63 Hz)
0.653
(1.53 Hz)
1.0
(1.0 Hz)
Period T (frequency)
Figure 14. Specific Response Spectrum Curve—Ground
The design spectral acceleration curve can now be computed. The
peak spectral acceleration (SDS) and the spectral acceleration at 1.0
second (SD1) may now be computed from the following formulas in
the code:
SDS = 2/3 x SMS = 2/3 x 2.85g = 1.90g
SD1 = 2/3 x SM1 = 2/3 x 1.86g = 1.24g
SDS, the peak spectral acceleration, extends between the values of
TS and T0. TS and T0 are defined in the codes as follows:
TS = SD1/SDS = 1.24/1.90 = 0.653 seconds (1.53 Hz)
T0 = 0.2 SD1/SDS = 0.2 x 1.24/1.90 = 0.131 seconds (7.63 Hz)
According to the IBC and ASCE 7-05, the spectral acceleration (Sa)
at periods less than 0.131 seconds may be computed by using the
following formula:
Sa = SDS (0.6 T/T0 + 0.4)
where T is the period where Sa is being calculated.
For example, the acceleration at 0.0417 seconds (24 Hz) is equal to:
Sa = 1.90 (0.6 [0.0417/0.131] + 0.4) = 1.12g
The acceleration at 0.03 seconds (33 Hz) is equal to:
Sa = 1.90 (0.6 (0.03/0.131) + 0.4) = 1.02g
At zero period (infinite frequency), T = 0, the acceleration (ZPA) is
equal to:
Sa = 1.90 (0.6 [0.0/0.131] + 0.4) = 0.76g (ZPA)
The acceleration to frequency relationship in the range of 1.0 Hz to
TS is stated equal to:
Sa = SD1 /T
where Sa is the acceleration at period T.
At 1.0 Hz (T = 1.0) this equation yields the following acceleration:
Sa = 1.24/1.0 = 1.24g
Testing has demonstrated that the lowest dominant natural
frequency of Eaton’s electrical equipment is above 3.2 Hz. This
indicates that testing at 1.24g at 1 Hz is not necessary. In addition,
having the low end of the spectra higher than realistically required
forces the shake table to move at extremely high displacements to
meet the spectral acceleration at the low frequencies.
12
EATON CORPORATION www.eaton.com
TS and T0 are dependent on SMS and SD1. If SM1 is small relative to SMS
then TS and T0 will be smaller and the associated frequencies will shift
higher. The opposite is also true. This must be realized in developing the complete RRS. Therefore, it is not adequate to stop the peak
spectral acceleration at 7.35 Hz. There are other contour line combinations that will produce different values for TS and T0. In accounting
for this variation in the spread between SMS and SD1 and the resulting
impact on TS and T0, it is almost impossible to consider all combinations. A study of the maps, however, suggests that all variations with
high magnitude of contour lines could very well be enveloped by a
factor of 1.5. Therefore, T0 is recomputed as follows:
T0 = 0.2 SD1/(SDS x 1.5) = (0.2 x 1.24)/(1.90 x 1.5) = 0.09 seconds
(11.0 Hz)
Based on past experience, most electrical equipment exhibits
natural frequencies in the range of 5 to 10 Hz. Therefore, they are
tested to the peak spectral accelerations required by the code. It is
also important to recognize that stopping the peak acceleration
shorter than 11 Hz would produce questionable test results due to
the elimination of a portion of the spectra that may well contain the
natural frequency of the equipment.
Eaton has developed generic seismic requirements that envelop
two criteria:
1. The highest possible spectral peak accelerations and ZPA
2. The maximum frequency range required for many
different sites
This approach results in a comprehensive and ultra conservative methodology in certifying equipment to the IBC and often
exceeds the approach utilized by other manufacturers.
Within the electrical industry, some manufacturers cease the
seismic peak spectral acceleration at 7 or 8 Hz. This substantially
reduces the amount of energy and frequency content included in
the input time history. There are many certifications issued by other
manufacturers that claim qualification to 3 or 4g spectral acceleration. This raises the question: “What is the true acceleration that
was measured at the natural frequencies of the equipment?”
It is very likely that the equipment dominant frequencies were only
tested to a fraction of what is claimed. Therefore, the claimed curve
should be reduced to the actual spectral acceleration at the dominant natural frequencies of the equipment. Eaton accounts for that
by testing to peak spectral accelerations even beyond 11.0 Hz.
This completes the ground motion design response spectrum. The
spectral accelerations are equal to 0.76g at zero period (ZPA) and
increases linearly to a peak acceleration of 1.90g at 0.09 seconds
(or 11 Hz) and stays constant to 0.313 seconds (or 3.2 Hz), then
gradually decreases to 0.7g at 1 second (or 1.0 Hz). This final
curve is shown in Figure 15.
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
Where:
Spectral Response Acceleration Sg
Fp: seismic design force imposed at the component’s C.G. and
distributed relative to component mass distribution
(SDS)1.90g
0.7g
ap: component amplification factor that varies from 1 to 2.50
SDS: spectral acceleration, short period, as determined in the
previous section
Wp: component operating weight
Rp: component response modification factor that varies
from 1.5 to 6.0 (ASCE 7-05 Table 13.6-1)
SD1
Ip: component importance factor of either 1.0 or 1.5
Z: highest point of equipment in a structure relative to
grade elevation
0.76g
h: average roof height of structure relative to grade elevation
15, 0.09
(11 Hz) (T0)
0.313
(3.2 Hz) (TS)
1.0
(1.0 Hz)
Period T (frequency)
Figure 15. Specific Response Spectrum Curve—Ground
To produce the maximum required force, the following parameters
were chosen:
Z is taken equal to h (equipment on roof)
Ip is taken as a maximum equal to 1.5
ap is taken equal to 2.5 (maximum value allowed by the ASCE code)
This curve indicates the ratio of peak spectral acceleration to
maximum input acceleration (ZPA) is 1.90/0.76 and approximately
equal to 2.5. This ratio is maintained throughout this document.
The code does not provide formulation for the seismic spectral
requirements inside buildings or above grade. Instead, the code
provides formulation of the equivalent loads at the center of gravity
(C.G.) of the equipment internal to structures or buildings. The
purpose is to ensure the structural and mounting integrity of the
equipment during and immediately after a seismic event. These
requirements will be discussed to determine realistic seismic
requirements for equipment mounted anywhere from the ground
level to the roof of a particular building.
B. Seismic requirements of equipment installed internal or
on top of structures (buildings)
The code provides a formula for computing the seismic requirements of electrical and mechanical equipment on ground level of a
structure or a building. This formula is designed for evaluating the
attachment of the equipment to the foundation directly supporting it.
The seismic loads are defined in ASCE 7-05 Section 13.3 as:
Fp = 0.4 ap SDS Wp (1+2 Z/h) / (Rp/Ip)
Rp is taken equal to 2.5 (lowest value allowed by the ASCE code
for electrical distribution and control equipment).
This combination of ap and Rp provides the most conservative
seismic loading requirements.
SDS has been computed in the previous section equal to 1.90.
The acceleration at the equipment C.G. when roof mounted is then
calculated as:
Acceleration = 0.4 x 2.5 x 1.90g (1+2) / (2.5/1.5) = 3.42g
For equipment on grade, the acceleration at the C.G. is then
calculated as:
Acceleration = 0.4 x 2.5 x 1.90g (1+0) / (2.5/1.5) = 1.14g
Based on this criterion, in order to establish the seismic acceptability of equipment inside a structure or a building, one must impose
an equivalent static load at the equipment C.G. and record the
results. This approach is very difficult and perhaps impossible
to apply.
The C.G. would first have to be located and then physically coupled
to a forcing mechanism supported by some type of a fixture and a
reaction mass. This approach would provide incomplete data or analysis. Applying a static load will push the entire system as one unit in
the force direction without revealing sufficient data about the equipment flexibility, the relative motion of internal components to the
cabinet structure, or the dynamics and resonance of the equipment.
A more realistic approach with enhanced test results is to expose
the equipment to floor motion, causing the inertia forces to occur
in the opposite direction when the mass is suddenly accelerated.
Bolting the base of a piece of equipment to a shake table, then
quickly accelerating it, results in exposing the equipment to inertia
loads higher than the source input.
EATON CORPORATION www.eaton.com
13
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
As explained previously, many seismic test programs clearly indicate
that electrical equipment, which is supported at the base, tends to
vibrate in the equipment’s natural dominant frequency, much like a
free cantilever beam that is supported at the bottom and free at the
top. The seismic response at the middle of the equipment’s C.G.
is at least 50% higher than the floor input of the equipment’s
natural frequency.
California Building Code (CBC) 2007
Therefore, the base forces associated with the static loads at the
C.G. of the equipment could be computed as 3.42/1.5 = 2.28g. The
ZPA associated with this spectral acceleration may be computed
per the previous relationships established.
Again, as in the IBC, the RSC starts at 1.24g (Sa) at 1.0 Hz, and
increases to 1.90g (SDS) at 1.53 Hz (Ts). The peak spectral accelerations then cover a wide band of frequencies up to 7.63 Hz (To) then
linearly decrease to 0.76g at the ZPA.
In the context of this discussion, Eaton’s seismic requirements to
meet the IBC (Reference 1) are:
Combined Seismic Requirements for Eaton’s Distribution
and Control Equipment
•
For equipment on grade, the base seismic requirements are
shown in Figure 15.
•
For equipment on the roof of a structure, the base input
acceleration at the equipment natural frequency must
demonstrate the ability to withstand levels of 2.28g base
acceleration or 3.42gs at the equipment C.G.
C. New Madrid seismic requirements
According to the IBC, the New Madrid fault maximum considered
earthquake spectral response acceleration is Ss = 3.69g and
S1 = 1.25g. The method to develop the required spectrum and
required forces at the C.G. is the same as described above. Based
on the exercise in the previous section, and by virtue of the
equations being of the first order, the requirements can be directly
determined by linearly increasing the complete levels and static force
requirements by the ratio of 3.69/2.85 = 1.29. The resultant RSC is
shown in Figure 16.
The maximum seismic forces at the C.G. for equipment mounted
at the top floor will be equal to 1.29 x 3.42 = 4.41g or 2.94g peak
spectral acceleration.
Eaton’s seismic requirements for (equipment on or in proximity to)
the New Madrid area is:
1. For equipment on grade, the base seismic requirements are
shown in Figure 16.
2. For equipment inside a structure or on top of the roof, the
base input acceleration at the equipment natural frequency
must exceed the levels of 2.94g base acceleration or 4.41g at
the equipment C.G.
The 2007 CBC, effective January 1, 2008, adopted the 2006 IBC as
CBC-Title 24. The seismic requirements are essentially the same
as described in the IBC, with some minor modifications. When
considering the maximum seismic requirements, the IBC and CBC
are basically identical.
To better compare all levels and determine the final enveloping
seismic requirements, the IBC standards are used for California and
New Madrid areas, as plotted in Figure 17. All curves are plotted at
5% damping. All curves are determined for equipment mounted on
grade or in the basement of the structure.
An envelopment of the seismic levels in the frequency range of 3.2
Hz to 100 Hz are also shown. This level is taken as Eaton’s generic
seismic test requirements for all certifications. These levels are also
plotted in Figure 18. The levels are listed below:
Frequency
Acceleration
1
0.719
3.2
2.28
11
2.28
33
1.02
100
1.02
Many standards require that seismic levels be increased by 10% to
account for differences in commercial hardware. Applying this will
bring the spectral peak acceleration to 2.51g and the ZPA to 1.12g.
Frequency
Acceleration
1
0.7
3.2
2.51
11
2.51
33
1.12
100
1.12
The vertical levels are taken equal to 2/3 of the horizontal
requirements.
2.46g
0.83g
In addition, Eaton performs seismic tests on the equipment at
approximately 120% of the generic enveloping seismic
requirements (see Figure 18). This testing is designed to
establish margin in anticipation of future changes in the codes.
For seismic certification of equipment located in the New Madrid
area, Eaton proceeds as follows:
Complete testing to the generic levels in Figures 17 and 18.
Perform additional tests at approximately 20% higher seismic levels
than shown in Figures 18.
1.0g
To
Ts
1.0
Period T
During September 2008, Eaton performed experimental seismic
testing on electrical equipment levels higher than the combined
requirements. Some of the equipment test results are shown in
Figures 19, 20, and 21. The levels are provided in the front-to-back,
side-to-side, and vertical directions. As indicated, the actual test
levels recorded were much higher than current codes require.
Figure 16. Response Spectrum Curve—Ground
(New Madrid Area)
19 See discussion under “A. Ground motion” on page 9 for
acceleration at 1 Hz.
14
EATON CORPORATION www.eaton.com
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
10
10
SS TRS
IBC 2006 New Madrid
Acceleration (g)
Acceleration (g)
IBC 2006/CBC 2007
1
Eaton Seismic
0.1
SS RRS
1
0.1
1
10
Frequency (Hz)
100
Figure 17. RRS Comparison
1
10
Frequency (Hz)
Figure 20. Test Response Spectrum Curve (Side to Side)
10
100
Eaton 120% Seismic Envelope
V TRS
Acceleration (g)
Acceleration (g)
100
Eaton 100% Seismic Envelope
1
10
1
V RRS
0.1
0.1
1
10
Frequency (Hz)
100
1
10
Frequency (Hz)
100
Figure 21. Test Response Spectrum Curve (Vertical)
Figure 18. 100% vs. 120%
10
Acceleration (g)
FB TRS
FB RRS
1
0.1
1
10
Frequency (Hz)
100
Figure 19. Test Response Spectrum Curve (Front to Back)
EATON CORPORATION www.eaton.com
15
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
Part IV
Test facility and test table
Test facility and test methodology
Test specimens for current production products are tested on
a truly independent triaxial shake table at the locations such as
Wyle Seismic Test Laboratory, located in Huntsville, Alabama.
Wyle Laboratories is accredited by the American Association for
Laboratory Accreditation (A2LA) in the field of vibration testing. The
Wyle Laboratories, Huntsville Facility, Quality Management System
is registered in compliance with the ISO-9001 International Quality
Standard. All instrumentation, measuring, and test equipment
used in the performance of test programs is calibrated in accordance
with Wyle Laboratories’ Quality Assurance Program, which complies
with the requirements of ANSI/NCSL Z540-1, ISO 10012-1, and
ISO/IEC 17025. The table and control systems are capable of
exciting the test specimens in all three directions simultaneously,
using statistically independent and phase incoherent seismic input
signals. A sketch of a test unit mounted to the shake table is shown
in Figure 22.
Test specimens
Since the inception of Eaton’s test program in 1985, more than
100 specimens have undergone seismic testing. Since it was not
feasible to test every single configuration, it was necessary to
select a number of test specimens that adequately represent
the total product portfolio. Each product line was reviewed and
evaluated to determine the number and design configurations of
the test specimens. Criteria were established for representation
of all equipment in each product line:
1. The test unit structure shall be similar to the major structural
configurations being supplied in the product lines. If more
than one major structure is being offered, then these
configurations shall also be selected for testing.
2. The mounting configuration of the test units to the shake
table shall simulate the different mounting conditions for the
product line. If several mounting configurations are used, the
different product variations are required to be included in
the testing program.
Test sequence
The seismic verification testing consisted of the following 10 steps
for each specimen:
1.
Receipt and inspection
2.
Functional operation
3.
Hi-pot electrical testing
4.
Resonance search testing
5.
Seismic test at 50% of the combined seismic requirements
4. The weight of the test units shall be similar to the typical
weight of the equipment being represented. Equal and
higher weights than the typical weight shall be acceptable.
6.
Seismic test at 100% of the combined seismic requirements
7.
Seismic test at higher than the 100% combined seismic
requirements (typically 120%–130%)
5. Other variations, such as the number of structures in
production assemblies, and indoor and outdoor applications,
will also be represented by the test specimens.
8.
Functional operation
9.
Hi-pot electrical testing
3. The major electrical components should be included in
the test specimens. The components shall be mounted at
similar locations to their mounting locations in production
configurations. The components shall be mounted to the
structure using the same mounting hardware used in the
typical design.
10. Final inspection
Resonance search test
Response
Accelerometers
Typical
Test Unit
Shake Table/
Base Motion
Accelerometers
Shake
Table
Resonance search (sine sweep) tests are performed on all test
specimens. The sine sweep tests are performed in the three principal axes of the test specimens: front-to-back, side-to-side, and
vertical directions. The sine sweep tests are conducted at amplitude
of 0.2g. The sine sweep tests are performed from 1 to 50 Hz at a
sweep rate of 1 octave per minute.
Seismic test input
The seismic inputs are generated using random signals with a
frequency and energy content up to 100 Hz. The test inputs are
independent in the three principal directions of the test specimens:
front-to-back, side-to-side, and vertical directions. All seismic test
inputs are 30 seconds in duration (see Figure 23).
Data acquisition
Side-to-Side
Base Input
Front-to-Back
Base Input
Vertical
Base Input
Figure 22. Test Specimen
The test inputs to the shake table are monitored using three
accelerometers mounted on the shake table. The accelerometers
are oriented in the shake table principal axes, which coincide with
the equipment front-to-back, side-to-side, and vertical directions.
The seismic response of the test specimens are monitored using
several accelerometers mounted on the test specimen and oriented
along the three principal axes of each test specimen. The test
input and seismic response of the equipment is recorded on and
analyzed using a shock spectra analyzer. The test response
spectra are derived at 5% damping (see Figures 23 and 24).
Electrical connection and test specimen monitoring
As stated previously, the acceptability of the test specimen requires
that all equipment maintain structural integrity and perform its
intended function before and after the seismic test.
16
EATON CORPORATION www.eaton.com
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
Test assembly and mounting conditions
At the beginning of each test, the test units are mounted to the shake
table (Figure 25) using the specified seismic mounting conditions.
3.0
MIN = – 0.1921E+01
MAX = 0.1588E+01
G
Min/max x:
B in size = 8
0.0
–2.0
0.00
30.00
Time (sec) x interval = 2.0000
Figure 23. Test Input
Figure 25. Typical Equipment Mounting and Installation
of Accelerometers
Test procedure
All test specimens identified in Part VI (Figure 26 See note on
pp. 20 regarding list of products.) are subjected to the seismic test
requirements specified in Figure 18. Testing is conducted in
accordance with IBC (ASCE 7-05), CBC, and ANSI C37-81 test
requirements. The test programs are documented in third-party
laboratory test reports.
Acceptance criteria
The seismic verification of the test specimens was based on the
following acceptance criteria:
Figure 24. Test Data Acquisition
1. The test specimens’ structure shall maintain structural
integrity with no major structural failure that may impact
the electrical performance of the test specimens or impact
adjacent equipment.
2. The test specimens shall perform their electrical function
immediately after seismic testing.
3. The test specimens shall pass one minute dielectric
withstand testing per the associated industry standards
after seismic testing.
EATON CORPORATION www.eaton.com
17
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
Part V
Shared responsibilities
The equipment manufacturer, specifier, Authority Having Jurisdiction
(AHJ), and installer have a shared responsibility to ensure that the
installation will meet the seismic requirements of the code. The
equipment manufacturer determines that the equipment will be
functional following a seismic event. The equipment specifier and
installer must ensure that the equipment is rigidly supported
and will not leave its foundation during a seismic event. The AHJ
shall confirm that the installation method conforms to the
manufacturer’s guidelines.
Previously in this paper, the Eaton interpretation of the various codes
and standards, as well as the levels of the test response spectra
used in testing, was described. The test results ensure that Eaton
equipment will perform the intended function after the seismic
event. However, the foundation and the anchorage must also meet
the codes and standards for the entire installation to be functional
after a seismic event. Equipment poorly anchored or mounted to a
flexible foundation will not meet the requirements.
The anchoring of electrical equipment as recommended by the
structural or civil engineer is critical. If the equipment is not attached
to the building structure in accordance with the minimum standards
recommended, the complete equipment installation might become
too flexible and may overturn or shear the attachment devices and
slide off its foundation. Such movement may damage either the
building structure or other components, including items connected
to the equipment.
Structural and civil engineers formulate methods of attachment that
are applicable to each specific condition based on past experience.
They evaluate the equipment, methods, and techniques of attachment along with tested anchoring systems. The structural or civil
engineers responsible for the structural design review the proposed
method of attachment. Based on both established criteria and direct
calculation, they verify its performance and the capability of the
building’s structural elements to accommodate the seismic forces.
In many states, registered professional civil or structural engineers
must attest that the design is adequate for the seismic environment
and apply their seal.
In evaluating the equipment mounting, the structural or civil engineer
performs calculations based on data received from the equipment
manufacturer specifying the size, weight, center of gravity, and
mounting provisions of the equipment. The embedded concrete
anchors, wood, or steel attachments must be adequate to resist the
site-specific seismic forces. For either attachment, bolts of the
proper grade of steel must be correctly sized and tightened to
recommended torque levels. If an embedded anchor is used, engineering data for the anchoring hardware will allow the engineer to
determine the size required. The mounting depth and the strength
of concrete to contain it will also be determined. The embedded
anchors must be correctly installed in accordance with the method
specified by the anchor manufacturer.
The reliability of electrical connections within the system must also
be considered. Electrical equipment is installed as part of a system.
Busway or conduits connect individual components of the electrical
system to each other. Interface methods that will prevent damage
from an earthquake must be specified. For example, bottom entry
of conduits is recommended for transformers and switchgear.
If top entry is specified, seismic fittings or a flexible interface
designed to accommodate the necessary enclosure motion
are needed. Transformers are often close coupled to switchgear
with a flexible connector to minimize transfer of relative motion.
Likewise, a flexible connector can be used to connect generators
to the bus duct, and the addition of insulating boots improves the
integrity of such installations.
The availability of electrical power following a disaster is often
critical. It is certain that earthquakes will occur in the future. It is
the responsibility of the engineer to design and specify reliable
equipment and systems that will withstand them. The IBC and CBC
establish minimum requirements for equipment seismic design and
18
EATON CORPORATION www.eaton.com
installation. As required by the IBC and CBC, Eaton has equipment
available that has been seismically certified. When specified, such
equipment increases the likelihood that the electrical system will
function in the aftermath of an earthquake.
Part VI
Typical Eaton seismic equipment specifications
1.01
The manufacturer of the assembly shall be the
manufacturer of the major components within
the assembly.
1.02
For the equipment specified herein, the manufacturer shall
be ISO 9001 or 9002 certified.
1.03
The manufacturer of this equipment shall have produced
similar electrical equipment for a minimum period of five
(5) years. When requested by the engineer, an acceptable
list of installations with similar equipment shall be provided
demonstrating compliance with this requirement.
1.04
Provide seismic qualified equipment as follows:
Note: To spec writer: To help understand the 2006 IBC/2007
CBC seismic parameters for a specific location, the attached link
to the U.S. Geological Society will be extremely helpful:
http://earthquake.usgs.gov/research/hazmaps/design/
•
Download the file “Java Ground Motion Parameter Calculator—Version
5.0.8 (4.6 MB)” and save it to your hard drive, then run the executable
file (.exe) that was downloaded.
•
Enter the latitude and longitude of your project location.
(To find exact latitude and longitude for a given address,
go to http://geocoder.us/)
•
The IBC seismic criteria for that location will then be displayed.
It is simply a matter of verifying that the criteria shown for your specific
building location is less than the equipment certification levels.
1. The equipment and major components shall be suitable for
and certified by actual seismic testing to meet all applicable
seismic requirements of the 2006 International Building Code
(IBC) Site Classification [enter classification from above Web
site]. The site coefficients Fa = [enter value from above Web
site], and spectral response accelerations of SS = [enter
value from above Web site]g, S1 = [enter value from above
Web site]g are used. The test response spectrum shall be
based upon a 5% damping factor, and a peak (SDS) of at least
[enter value from above Web site] g’s (3–12 Hz) applied at
the base of the equipment in the horizontal directions. The
forces in the vertical direction shall be at least 66% of those
in the horizontal direction. The tests shall cover a frequency
range from 1 to 100 Hz. Guidelines for the installation
consistent with these requirements shall be provided by the
equipment manufacturer and based upon testing of representative equipment. Equipment certification acceptance
criteria shall be based upon the ability for the equipment
to be returned to service immediately after a seismic event
within the above requirements without the need for repairs.
-- OR -2. The manufacturer shall certify the equipment based upon
a dynamic and/or static structural computer analysis of the
entire assembly structure and its components, provided it is
based upon actual seismic testing from similar equipment.
The analysis shall be based upon all applicable seismic
requirements of the 2006 International Building Code (IBC)
Site Classification [enter classification from above Web site],
site coefficient Fa = [enter classification from above Web
site], FV = [enter classification from above Web site] and
spectral response accelerations of SS = [enter classification
from above Web site]g, S1 = [enter classification from above
Web site]g. The analysis shall be based upon a 5% damping factor, and a peak (SDS) of at least [enter classification
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
from above Web site]g, S1 (3–12 Hz), applied at the base of
the equipment in the horizontal directions. The forces in the
vertical direction shall be at least 66% of those in the horizontal direction. The analysis shall cover a frequency range
from 1 to 100 Hz. Guidelines for the installation consistent
with these requirements shall be provided by the equipment
manufacturer, and should be based upon testing of representative equipment. Equipment certification acceptance criteria shall be based upon the ability for the equipment to be
returned to service immediately after a seismic event within
the above requirements without the need for repairs.
Seismic White Paper SA12501SE
Effective August 2009
When the MCC test units were tested supported at the bottom
and with the top attached to a lateral wall, the seismic capacity
of the test units were found to be much higher than their seismic
capacity when supported at the bottom only. The seismic capacity of equipment presented in some papers appears to be based
on testing of equipment with both top and bottom supports. It is
important, therefore, to recognize that those published curves only
apply to equipment mounted using top and bottom supports. Other
mounting arrangements without top lateral supports will need to be
re-established based on new testing programs.
A. The following minimum mounting and installation guidelines
shall be met, unless specifically modified by the above
referenced standards.
1. The contractor shall provide equipment anchorage details,
coordinated with the equipment mounting provision,
prepared and stamped by a licensed civil engineer in the
state. Mounting recommendations shall be provided by the
manufacturer, and should be based upon the above criteria
to verify the seismic design of the equipment.
a. The equipment manufacturer shall certify that the
equipment can withstand, that is, function following the
seismic event, including both vertical and lateral required
response spectra, as specified in above codes.
b. The equipment manufacturer shall document the requirements necessary for proper seismic mounting of the
equipment. Seismic qualification shall be considered
achieved when the capability of the equipment meets
or exceeds the specified response spectra.
SEISMIC QUALIFIED
TEST CERTIFICATE OF SEISMIC WITHSTAND CAPABILITY
Eaton’s Cutler-Hammer equipment identified below was tested for seismic withstand capability and tested in accordance
with the combined requirements specified in the International Building Code, California Building Code and the Uniform
Building Code. As required by the codes, the equipment demonstrated its ability to function after the seismic tests.
The seismic capability of the equipment exceeds the worst-case required levels, as illustrated in the figure below.
0HWDO(QFORVHG/RZ9ROWDJH6ZLWFKJHDU³0DJQXP'6
)URQW$FFHVVLEOHZLWK7\SH0'6&LUFXLW%UHDNHUVRU
&01HWZRUN3URWHFWRUV
Period (seconds)
.31
.25
.20
.16
.13
.10
.08
.06
.05
.04
.03
0
4.0
Eaton’s equipment test levels and ICC-ES-AC156
The frequency sweep
tests revealed that the
lowest equipment natural
frequency is:
3.5
Damping = 5%
2.5
Response
Acceleration
(g)
2.0
Zero Period Acceleration
In December 2006, the ICC-ES issued an “Acceptance Criteria
for Seismic Qualification by Shake-Table Testing on Nonstructural
Components and Systems.” The criteria was made effective January
1, 2007. Eaton’s methodology for seismic certification of electrical
equipment is consistent with the proposed criteria and meets the
testing requirements specified. Eaton, however, differs in one important aspect: Eaton has taken the ratio of the equipment response
modification factor (RP) to equipment importance factor (IP) equal to
2.5/1.5. This ratio provides the minimum ratio required by the codes
for electrical distribution and control equipment, and also considers that the acceleration is required to be measured at the center
of gravity of the equipment. The ICC-ES-AC156 employs a factor of
1.0 to this ratio producing unnecessary and overtesting conditions.
One additional difference needs to be mentioned—Eaton’s electrical
equipment, with high natural frequencies (per ICC-ES-AC156), are
also tested and certified to the same seismic test input as flexible
equipment. ICC indicates that this equipment may be tested to 0.4
of the seismic levels developed for flexible equipment. Eaton’s test
program is more conservative by testing all equipment types to the
highest levels.
3.0
1.5
1.0
.5
+]
0
3.2
4
5
6.4
8
10
13
17
20
26
32
Frequency (Hz)
3RD PARTY TEST ENGINEER IN CHARGE
1DWKDQ*OHQQ3(
:HVWLQJKRXVH(OHFWULF&RPSDQ\//&
7(67('%<
:\OH/DERUDWRULHV
6HSWHPEHU
For interpretation of testing data
refer to Eaton
Publication SA12501SE
'UDZLQJ1XPEHU6$(
In addition, an important note should be made regarding the mounting configurations of the test units. Eaton’s equipment is mounted
to the shake table in their most conservative and common mounting
configurations to establish the lower bound of the equipment
seismic capabilities. For example, Eaton seismic certification curves
for motor control centers (MCCs) are based on a test unit mounted
at the base as a free cantilever item, free at the top and supported
only at the bottom. This test configuration encompasses all
other mounting configurations because of its conservative nature.
The test capability in Eaton’s certificates, therefore, covers
all other applications.
EATON CORPORATION www.eaton.com
19
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
Low Voltage Metal-Enclosed Switchgear
s $3))
s -AGNUM$3
s (IGH2ESISTANCE'ROUND
Panelboards
s 0OW2,INE#AA,8AA,8A%0
&AND0OW2#OMMAND%
Switchboards
s )NSTANT
s )NTEGRATED&ACILITIES
s -ULTIMETER
MCC
s !DVANTAGE[h
s &LASH'ARD[h
s &REEDOM
s 0OW2,INE0
s 0OW2,INE#
s 0OW2,INEI
gh IT.
gh 3ERIES
Low Voltage Busway
s 0OW27AY姞AND!SSOCIATED&ITTINGS
s 0OW27AY)))AND!SSOCIATED&ITTINGS
Dry Type Transformers
s -INI0OWERCENTERS
s %0%04$3$4
Transfer Switches
s !UTOMATIC4RANSFER3WITCH%QUIPMENT
Uninterruptible Power Supplies (UPS)
s "ATTERY-ODULES
s 503S
Enclosed Control
Safety Switches
s 'ENERAL$UTY
s (EAVY$UTY
s %LEVATOR#ONTROL-ODULE
Medium Voltage Switchgear
s 4YPE6AC#LAD7
s 4YPE--63
s -%&
s 4YPE-63-%"
MV Bus
s -ETAL%NCLOSED.ON3EGREGATED0HASE"US
Network Protectors
s 4YPE#-
s 4YPE#-$
Medium Voltage Control
s !MPGARD4
s 3#$RIVES
Substation Transformers
s $RY4YPE
s ,IQUID4YPE
s 5NITIZED$RY4YPE0OWER#ENTERS
Figure 26. Seismic Test Units
20
EATON CORPORATION www.eaton.com
Part VII
References
http://www.math.montana.edu/~nmp/materials/ess/geosphere/
expert/activities/earthquakes/index.html
http://rchrd.com/weblog/archives/archive_2004-m09.php
http://w3.salemstate.edu/~lhanson/gls100/gls100_plate_tec.htm
Beer, Ferdinand P. and Johnston, E. Russell, Jr., (1962),
Vector Mechanics for Engineers Statics and Dynamics
McGraw Hill Book Company
New York, NY, 1962
California Building Standards Commission,
California Building Code (2007)
428 J. Street, Suite 450
Sacramento, CA 95814
International Code Council,
International Building Code (2006)
Suite 708,
Falls Church, VA 22031-3401
International Conference of Building Officials, (1997),
Uniform Building Code
5360 Workman Mill Road
Whittier, CA 90601
Institute of Electrical and Electronics Engineers, Inc.,
ANSI/IEEE C37.81 (1987)
Guide for Seismic Qualification of Class 1E Metal Enclosed Power
Switchgear Assemblies
East 47th Street
New York, NY 10017-2394
Institute of Electrical and Electronics Engineers, Inc.,
ANSI/IEEE 344 (1987)
Recommended Practice for Seismic Qualification of Class 1E
Equipment for Nuclear Power Generating Stations
East 47th Street
New York, NY 10017-2394
Newmark, Nathan M. and Rosenblueth, Emilio, (1971),
Fundamentals of Earthquake Engineering
Prentice-Hall, Inc.
Englewood Cliffs, NJ 01971
The Building Officials and Code Administrators International, Inc.
W Flossmoor Rd
Country Club Hills, Il 60478-5795
Wiegel, Robert L., (editor),
Earthquake Engineering
Prentice-Hall, Inc.
Englewood Cliffs, NJ 01971
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
This page intentionally left blank.
EATON CORPORATION www.eaton.com
21
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
This page intentionally left blank.
22
EATON CORPORATION www.eaton.com
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Seismic White Paper SA12501SE
Effective August 2009
This page intentionally left blank.
EATON CORPORATION www.eaton.com
23
Seismic White Paper SA12501SE
Effective August 2009
Earthquake requirements and seismic
capabilities for Eaton’s electrical
distribution and control equipment
Eaton Corporation
Electrical Sector
1111 Superior Ave.
Cleveland, OH 44114
United States
877-ETN-CARE (877-386-2273)
Eaton.com
© 2009 Eaton Corporation
All Rights Reserved
Printed in USA
Publication No. SA12501SEE / Z8772
August 2009
PowerChain Management is a registered
trademark of Eaton Corporation.
All other trademarks are property of their
respective owners.