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IBC Seismic Code and
Ceiling Installation Requirements
Armstrong World Industries
2500 Columbia Ave, P.O. Box 3001
Lancaster, PA 17604
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Slide 1 of 65
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IBC Seismic Code and Ceiling Requirements
IBC Seismic Code and Ceiling Installation Requirements
Presented By:
Armstrong Techline
Armstrong World Industries
2500 Columbia Ave, P.O. Box 3001
Lancaster, PA 17604
Description:
Provides an overview of IBC Seismic Design Categories and
installation requirements for suspended ceilings, including
key variables used to establish a Seismic Design Category, and
requirements for Seismic Design Categories C, D, E, and F.
AIA/CES Info:
Provider No. J624 – Course No. AEC036; LUs – 1.00
MCE Info:
Contact your respective governmental licensing and
regulatory agency. This program qualifies for HSW credit.
Expiration date:
February 28, 2006.
This program is registered with AIA/CES for continuing professional registration. As such, it does not include content that may be deemed
or construed to be an approval or endorsement by the AIA or AEC Daily Corporation of any material or construction or any method or
manner of handling, using, distributing or dealing in any material or product. Questions related to specific materials, methods and
services should be directed to the program instructor.
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Slide 2 of 65
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IBC Seismic Code and Ceiling Requirements
How to use this Online Learning Course
•
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•
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•
Within this course is a code word that you will be required to enter in order to
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•
To receive a certificate indicating course completion, refer to the instructions at
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Slide 3 of 65
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IBC Seismic Code and Ceiling Requirements
Learning Objectives
Upon completing this course, you will have a better understanding of:
•
The International Building Code (IBC) as it pertains to suspended ceilings
•
The three key variables that are used to establish a Seismic Design Category
•
How occupancy (seismic use group) affects requirements for suspended ceilings
•
Installation requirements for suspended ceilings in Category C structures
•
Additional installation requirements for Category D, E, and F suspended ceilings
•
How IBC requirements affect project costs for different seismic design categories
This document is intended as a guideline only. It is not intended to provide legal or engineering services. It is not a substitute for the full
text of the referenced standards and does not reflect all building codes and regulations that may be applicable to a particular installation.
The user should be familiar with all building codes and regulations applicable to the particular locale and installation, and assure
compliance with all applicable legal requirements.
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Slide 4 of 65
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IBC Seismic Code and Ceiling Requirements
Today's Seismic Standards
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Slide 5 of 65
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IBC Seismic Code and Ceiling Requirements
Today's Seismic Standards
What is the IBC?
•
The International Building Code (IBC)
is the first model building code to
address differences in seismic hazard
to ceilings based on soil type.
•
The IBC continues to be adopted
across the country, with 44 states
using the IBC at state or local levels.
•
Adoption of the IBC increases safety,
as well as the costs associated with
the installation of suspended ceilings
in many areas of the country.
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Slide 6 of 65
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IBC Seismic Code and Ceiling Requirements
Today's Seismic Standards
Non-Structural Systems
•
Previous codes were concerned with
protecting the structural integrity of
buildings; the failure of non-structural
systems was not a primary concern.
•
In contrast, the IBC also recognizes
that the failure of non-structural
systems can render a space unusable.
•
Today, non-structural systems such
as suspended ceilings–designed and
installed to meet IBC requirements–
can survive intact, without the need
for repair or replacement.
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Seismic Speech Video
To view this video, simply click on the play
button above. This video has audio; please
ensure that your speakers are turned on.
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Slide 7 of 65
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IBC Seismic Code and Ceiling Requirements
Today's Seismic Standards
Seismic Design Categories
•
The primary difference between the
IBC and previous codes is that the IBC
requires a "Seismic Design Category"
to be assigned to each project.
•
The IBC outlines a total of six Seismic
Design Categories (A, B, C, D, E, F),
ranging from least to most stringent.
•
Project design teams are responsible
for determining this category and
communicating it to the construction
team prior to the submittal of bids.
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Slide 8 of 65
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IBC Seismic Code and Ceiling Requirements
Today's Seismic Standards
How is IBC 2003 different from IBC 2000?
•
In the first edition of the International Building Code, IBC 2000, the installation
requirements for suspended ceilings were listed in Section 1621. This version of
the code is the one currently being used in the majority of the jurisdictions that
have adopted the IBC.
•
In the latest edition of the code, IBC 2003, most of the information in Section
1621 has been replaced by the American Society of Civil Engineers' "Minimum
Design Loads for Buildings and Other Structures" [ASCE 7-02].
•
Despite this change in referencing, it is important to note that the information
on seismic design and the actual requirements for suspended ceiling systems
have not changed from IBC 2000 to IBC 2003. The original requirements in IBC
2000 were taken from the ASCE document that is now referenced in IBC 2003.
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Slide 9 of 65
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IBC Seismic Code and Ceiling Requirements
Establishing a Seismic Design Category
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Slide 10 of 65
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IBC Seismic Code and Ceiling Requirements
Establishing a Seismic Design Category
Introduction
There are three key variables used to
establish a seismic design category for
a given project:
1. Ground Motion: Anticipated ground
motion for a geographic location.
2. Soil Class: Refers to the type of soil
(e.g. rock, sand, etc.) at a specific site.
3. Seismic Use Group: Three different
use groups based on occupancy.
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Slide 11 of 65
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IBC Seismic Code and Ceiling Requirements
Establishing a Seismic Design Category
Ground Motion
•
The first step in establishing a seismic design category is determining the
maximum amount of anticipated ground motion for your particular building
site. Ground motion is presented as a percentage of the acceleration of gravity
(% g), where g is equal to 32 feet / second2.
•
Ground acceleration values can be obtained by using GPS coordinates for a given
site, by referring to the hazard maps contained in the IBC, or by entering the zip
code for a given site into software provided by the U.S. Geological Service.
•
Anticipated ground motion is usually represented by two different maps, one
showing ground motion for a 0.2 second period and the other showing ground
motion for a 1 second period. Two sets of calculations are carried out using
these values. The one that provides the least favorable result must be followed.
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Slide 12 of 65
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IBC Seismic Code and Ceiling Requirements
Establishing a Seismic Design Category
Ground Motion Cont'd…
This map illustrates anticipated seismic hazards for the conterminous United States.
Highest Hazard
32+
24-32
16-24
%g
8-16
4-8
2-4
0-2
Lowest Hazard
Source: U.S. Geological Service
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Slide 13 of 65
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IBC Seismic Code and Ceiling Requirements
Establishing a Seismic Design Category
Soil Class
•
The second step in establishing a
seismic design category for a given
project involves investigating the
site's existing soil conditions.
•
Soil type is typically evaluated to a
depth of 100' , with ratings from A
(hard rock) to F (unstable soil).
•
If no soil analysis is carried out, the
soil type or "site classification" for
that particular site typically defaults
to a "D" rating.
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Slide 14 of 65
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IBC Seismic Code and Ceiling Requirements
Establishing a Seismic Design Category
Soil Class Cont'd…
•
In some cases, building officials can
overrule the default to a "D" rating
if they feel that Type "E" or "F" soil
is likely to be present.
•
Soil type is an important variable that
can have a significant impact on the
design and construction of a project.
•
Similar projects located within the
same geographical area may fall into
different seismic design categories as
a result of soil type.
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Slide 15 of 65
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IBC Seismic Code and Ceiling Requirements
Establishing a Seismic Design Category
Seismic Use Group
•
The final step in establishing a
seismic design category involves
determining a project's seismic use
group based on its occupancy.
•
How critical the operability of the
facility is in the event of a disaster
is also taken into account.
•
The idea of assessing risk factors
based on occupancy is not new.
Codes have long recognized that
some uses are more important.
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Slide 16 of 65
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IBC Seismic Code and Ceiling Requirements
Establishing a Seismic Design Category
Seismic Use Group Cont'd…
Real Earthquake Video
The IBC outlines three different seismic
use groups based on building occupancy:
•
Group I: Normal occupancy. Includes
any building not assigned elsewhere.
•
Group II: High occupancy. Includes
schools, large office buildings, and
shopping malls.
•
Group III: Essential use. Includes fire
and police stations, and emergency
medical facilities.
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To view this video, simply click on the play
button above. This video has audio; please
ensure that your speakers are turned on.
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Slide 17 of 65
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IBC Seismic Code and Ceiling Requirements
Establishing a Seismic Design Category
Combining the Variables
•
•
Ground motion, site classification,
and seismic use group designations
are combined to yield a seismic
design category of A, B, C, or D.
An "E" or "F" designation only
occurs for sites where anticipated
ground motion is extremely high.
Which Seismic Design Category
would be assigned to a large office
building located in an area with
high anticipated ground motion?
a) Seismic Design Category B
b) Seismic Design Category D
c) Seismic Design Category E
•
Structures in an area with ground
motion of 0.75 G or more at 1 second
are classified as Category "E" (Group
I or II) or Category "F" (Group III).
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d) Seismic Design Category F
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Slide 18 of 65
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IBC Seismic Code and Ceiling Requirements
Free-Floating Components
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Slide 19 of 65
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IBC Seismic Code and Ceiling Requirements
Free-Floating Components
Installation Requirements
•
Before we discuss the requirements
for specific seismic design categories,
it is important to note the exception
for free-floating components.
•
Suspended ceiling systems that do
not run to the walls are considered
to be "free-floating".
•
As such, they must be restrained to
prevent damage that would be
caused by excessive motion (1).
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Slide 20 of 65
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IBC Seismic Code and Ceiling Requirements
Free-Floating Components
Installation Requirements Cont'd…
•
However, the components that can
move 12" minimum or swing 45° off
vertical without damage do not need
to be restrained (1).
•
Also, attachment systems for freefloating components are required to
have a minimum 3:1 safety factor.
•
Although ASCE 7 is not as specific
as the IBC, it does state that these
components may not be damaged or
cause damage during a seismic event.
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Slide 21 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories A and B
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Slide 22 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories A and B
Installation Requirements
•
The IBC does not contain any
additional requirements pertaining
to suspended ceiling installations in
seismic design categories A or B.
•
For these types of buildings, the
basic requirements established in
ASTM C636 should be followed.
•
ASTM C636 covers the "Standard
Practice for Installation of Metal
Ceiling Suspension Systems for
Acoustical Tile and Lay-In Panels".
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Slide 23 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories A and B
Relative Installation Costs
•
•
•
Since categories A and B involve
standard installations, they can be
used to establish a baseline for the
evaluation of other categories.
Typically, one half of the installation
cost is associated with the grid, and
the other half with the ceiling panels.
Assuming both the grid and the
panels cost $1.00 / ft2 for a basic, flat,
2 x 4, lay-in ceiling, the total cost for
categories A and B is $2.00 / ft2.
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Estimated Installation Costs
Categories A and B
Item
Cost
Suspension Grid
$1.00 / ft2
Ceiling Panels
$1.00 / ft2
Total
$2.00 / ft2
Note: Total installation costs may vary by
market, however the 1:1 grid to panel cost
ratio should remain relatively constant.
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Slide 24 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
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Slide 25 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Installation Requirements
•
For Category C, all structures equal
to or greater than three stories, and
all Group III structures, must comply
with additional IBC requirements.
•
The only exception is for Seismic Use
Group I and II buildings that are less
than three stories tall.
•
These additional code requirements
will impact construction methods for
partitions and penetrations in Seismic
Design Category C structures.
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Slide 26 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Unrestrained Ceiling
•
IBC 2000 calls for suspended ceilings
in Seismic Design Category C to be
installed in accordance with CISCA
Seismic Zone 0-2 recommendations.
•
The goal of this standard is to create
an "unrestrained" ceiling that allows
movement during a seismic event.
•
A free-floating ceiling that cannot
touch or be attached to walls will
increase installed costs because it is
harder to keep it straight and square.
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Slide 27 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Ceiling Weight
•
CISCA standards require that the
ceiling system weight not exceed
2.5 lbs/ ft2 (2). Heavier systems
must meet CISCA Zone 3-4
recommendations.
•
"System" weight includes the grid,
panels, light fixtures, and any air
terminals supported by the grid.
•
Typical suspended ceiling assemblies
weigh about 1-1/4 to 1-1/2 lbs/ ft2.
Heavier wood or GRG ceiling panels
often exceed this weight limit.
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Slide 28 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Wall Molding
•
CISCA identifies minimum horizontal
flange dimensions and minimum
clearances to ensure that the ceiling
assembly can move in all directions.
•
A minimum 7/8" horizontal flange
must be used, with a minimum 3/8"
clearance from the wall on all sides.
•
Step or shadow molding may be used
to meet this requirement (minimum
3/8" perch). Perimeter attachment is
not permitted in either case (3,4).
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Minimum 7/8" Horizontal Flange
with Minimum 3/8" Wall Clearance
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Slide 29 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Wall Molding Cont'd…
An appropriate step molding can also be used to provide the required clearances.
min. 3/8"
min. 3/8"
Spacer bar (or other
suitable system)
to keep perimeter
components from
spreading apart
min. 3/8"
min. 3/8"
min. 7/8"
min. 7/8"
Angle Molding
Stepped Molding
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Slide 30 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Wall Molding Cont'd…
•
When the horizontal leg is less than
7/8", the terminal ends of each grid
member must be independently
supported within 8" of the wall (3).
•
This support may consist of 12-gauge
hanger wire or other support to
prevent the grid from falling.
•
Perimeter wires may attach to the
structure above or the wall above the
plane of the ceiling, however the 3/8"
end clearance must be maintained.
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©2005
9/16"
molding
Note: Installation costs increase significantly
when perimeter support wires are required.
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Slide 31 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Wall Molding Cont'd…
•
For essential use (Group III) facilities
within Category "C", the option to
use a molding with a horizontal
flange less than 7/8" is eliminated (5).
•
In addition, perimeter wire must be
used to support the terminal ends of
each grid component.
•
Also, the minimum clearance from
the ends of the suspension system
components to the wall is increased
from 3/8" to 1/2" on all sides.
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Slide 32 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Suspension Systems
•
In addition to ceiling weight and
molding requirements, the IBC also
outlines requirements regarding the
pull out strength of the grid.
•
Information regarding pull out
strength can typically be found in
the suspension system data pages.
•
For Category C, main beam and cross
tee intersections and splices must have
a minimum connection strength of
60 lbs in compression and tension (6).
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Slide 33 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Perimeter Spacers
•
With unrestrained ceilings, there is no
positive attachment to the perimeter,
meaning that grid components could
spread apart and allow panels to fall.
•
As a result, perimeter components
must use spacer bars or another
suitable system to prevent spreading
(4).
•
This photo shows how stabilizer or
spacer bars can be installed over the
cut ends of the perimeter grid
components to prevent spreading.
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Slide 34 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Light Fixtures
•
The code requires that light fixtures
be supported by two 12-gauge wires
(that may be slack) that are attached
at diagonal corners (7).
•
Light fixtures in excess of 56 lbs must
be independently supported from the
building structure.
•
This requirement does not specify a
type of light fixture, however it is
assumed to apply to all light fixtures
other than pendant-mounted types.
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Slide 35 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Penetrations and Partitions
•
•
To maintain the ceiling's ability to
move, all penetrations must allow 3/8"
minimum clearance by use of suitable
escutcheons or closure details (3).
The goal of CISCA Seismic Zone
0-2 recommendations for Seismic
Design Category C structures is a
suspended ceiling system that is?
The code states that attachment of
partitions must allow the ceiling to
move 3/8" in any direction
a) Restrained
b) Unrestrained
c) Supported
•
Walls and partitions may be braced
independently, however the material
and labor costs associated with this
are not included in the cost model.
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©2005
d) Unsupported
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Slide 36 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Category C
Relative Installation Costs
•
•
•
For Groups I and II, IBC requirements
increase grid costs by 25%, resulting
in a total cost of $2.25 / ft2, or a 12.5%
increase, over Categories A and B.
For Group III, the requirement for
perimeter wires adds an additional
25% to the suspension system costs.
As a result, the total installed cost
for a Group III structure increases to
$2.50 / ft2, which represents a 25%
increase over standard ceiling systems.
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©2005
Estimated Installation Costs
Category C (Groups I, II, and III)
Item
Group I & II
Group III
Grid
$1.25 / ft2
$1.50 / ft2
Panels
$1.00 / ft2
$1.00 / ft2
Total
$2.25 / ft2
$2.50 / ft2
Note: Total installation costs may vary by
market, however the grid to panel cost
ratio should remain relatively constant.
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Slide 37 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
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Slide 38 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Installation Requirements
•
For Categories D, E, and F, the IBC
requires ceilings to be designed and
installed in accordance with CISCA
Seismic Zone 3-4 recommendations.
•
In addition to the CISCA guidelines,
the IBC also outlines eight additional
requirements for D, E, and F ceilings.
•
In contrast to Category C, which
requires a ceiling to be unrestrained,
the goal for Categories D, E, and F is
to design a restrained ceiling system.
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Slide 39 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Lateral Load Exemptions
CISCA recommendations for Seismic
Zones 3-4 exempt two types of ceilings
from lateral load requirements:
1.
Ceiling areas of 144 ft2 or less (9)
2.
Lath and plaster or screw-applied
gypsum board ceilings (10)
It should be noted that IBC requirements
override the first exemption in that the
IBC does not require lateral force bracing
for ceiling areas less than 1,000 ft2.
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Slide 40 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Wall Molding
•
Wall moldings are required to have
a horizontal flange of at least 2",
with the ceiling grid attached to
the molding at two adjacent walls.
•
The unattached ends of the grid must
have 3/4" clearance from the wall and
be free to slide on the molding (11).
•
Attachment at adjacent walls with
clearance at opposite walls prevents
the system from banging into walls
during a more severe seismic event.
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Slide 41 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Hangers
•
•
Hangers used to support the ceiling
system must consist of a minimum of
12-gauge wire at 4' on center, or 10gauge wire at 5' on center (12).
The goal of CISCA and IBC
requirements for Seismic Design
Category D, E, and F structures is a
suspended ceiling system that is?
In addition, the attachment devices
used to fix the upper end of the wire
to the building structure must be able
to support a minimum of 100 lbs.
a) Unsupported
b) Supported
c) Unrestrained
d) Restrained
Please remember the word ATTACHMENT. You
will be required to enter it in order to proceed
with the online examination.
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Click here for the correct answer
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Slide 42 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Perimeter Support
•
Categories D, E, and F must have
main beams and cross tees supported
within 8" of each wall with 12-gauge
wire or approved wall support (13).
•
Perimeter support wire is required
for all suspended ceilings, regardless
of seismic use group.
•
This photo shows 2" perimeter wall
molding with typical perimeter wire
attachment within 8" of the terminal
end of each piece of the grid system.
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Slide 43 of 65
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Perimeter Spacers
As with category C ceilings, the cut ends of grid components (main runners and
cross tees) must be tied together with spacer bars to prevent spreading (14).
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Suspension System
•
For Category D, E, and F structures,
the IBC requires main beams to be
of "heavy-duty" construction (15).
•
ASTM C 635 defines "heavy-duty" as
capable of supporting 16 lbs / linear
foot without deflecting more than
1/360 of span length.
•
In addition, main beam and cross tee
intersections and splices must have
connection strengths of at least
180 lbs in compression and
tension (16).
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Suspension System Cont'd…
•
Cross tees that support light fixtures
must have the same load-carrying
capacity as the main beams (17).
•
Cross tees supporting mechanical
services are also required to have
the same load-carrying capacity as
the main beams (18).
•
For cross tees that do not have a
load capacity comparable to the
main beams, supplemental hangers
(e.g. wires) must be added.
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Lateral Force Bracing
•
The IBC requires ceiling areas greater than or equal to 1,000 ft2 to have lateral
force bracing, which may consist of diagonal splay wires or rigid bracing (19).
The IBC also specifies that this lateral force bracing must limit ceiling movement
to less than 1/4" at the point of attachment (19).
•
This last point clearly establishes a performance requirement for the bracing,
which is a new concept. Previous codes required lateral bracing, however they
did not specify how well it was required to work.
•
Typical lateral force bracing is achieved with clusters of four diagonal wires,
however the IBC specifically mentions rigid bracing as an acceptable option.
There are some instances (which will be discussed later), where rigid bracing
appears to be the preferred method.
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Lateral Force Bracing Cont'd…
•
Splay wire bracing typically consists
of clusters of four 12-gauge wires
attached to the main beam within
2" of the cross tee intersection (20).
•
The wires are arrayed 90° from each
other at an angle not to exceed 45°
from the plane of the ceiling.
•
Struts are attached at each bracing
location in order to prevent any upward movement of the ceiling that
may be induced by the application of
lateral force to the diagonal wires.
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Lateral Force Bracing Cont'd…
•
By default, CISCA requires lateral
force bracing to be applied in a 12'
x 12' pattern with the first restraint
point within 6' of each wall (20).
•
The IBC does allow the pattern to be
altered by calculation, but assumes a
ceiling weight of 4 lbs / ft2.
•
Attachment devices for the bracing
wires to the main beam and to the
structure must support the greater
of 200 lbs or the actual design load
with a safety factor of two (20).
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Light Fixtures
•
Light fixtures must be positively
attached to the suspension system
with devices able to withstand the
full weight of the fixture (17).
•
Light fixtures weighing less than
56 lbs must have two 12-gauge wires
attached at diagonal corners (17).
•
Heavier light fixtures, weighing
more than 56 lbs are required to be
independently supported from the
building structure.
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Light Fixtures Cont'd…
•
With regard to pendant-mounted
fixtures, CISCA stipulates that they
must be supported directly from the
structure using 9-gauge wire.
•
Unlike other types of light fixtures,
they may not use the suspended
ceiling system for support regardless
of the weight of the fixture.
•
This photo shows a support bracket
for a pendant fixture. The bracket
accommodates the 9-gauge hanger
wire, as required by CISCA.
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Mechanical Services
•
Like light fixtures, mechanical devices
must be attached to main beams and
cross tees, however devices less than
20 lbs do not require safety wires.
•
Terminals or services weighing 20 lbs
to 56 lbs require two 12-gauge wires
connecting them to existing ceiling
hanger wires or the structure above.
•
Mechanical services weighing more
than 56 lbs must be independently
supported from the structure (18).
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Partitions and Penetrations
•
Partitions attached to the suspension
grid must be laterally braced to the
building structure–independent of
any ceiling splay wire bracing (21).
•
The only exception is for walls less
than 9' tall, where horizontal seismic
loads do not exceed 5 lbs / ft2.
•
Except where rigid bracing is used,
penetrations must have 2" oversized
trim in order to allow 1" of lateral
movement in all directions (22).
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Seismic Separation Joints
•
Ceiling design is also impacted by
joints. Ceilings greater than 2,500 ft2
must have seismic separation joints
or full height partitions (23).
•
Analysis must demonstrate that trims
and angles provide enough clearance
for ceiling movement.
•
This diagram illustrates how a series
of 1" x 2" angle moldings can be
used to create the required seismic
separation joint between panels.
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Other Requirements
•
Height Transitions: The IBC also
requires additional positive bracing
to be added to the grid system at
every point where there is a change
in ceiling plane elevation (24).
•
Cable Trays: The IBC also specifies
that all electrical conduits and cable
trays must be supported and braced
independently of the suspension
system (25). Note that this is not a
new requirement and is also a part
of the National Electrical Code.
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Special Inspection
•
Suspended ceiling systems are
subject to special inspection, which
entails manufacturer certification of
product performance and periodic
inspection of the suspended ceiling
system anchorage (26).
•
Evaluation services are now being
consolidated under the International
Code Council Evaluation Service (ICCES). Reports issued by earlier services
(ICBO, BOCA, etc.) will be transferred
to and maintained by ICC-ES.
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Full-Scale Simulation Video
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IBC Seismic Code and Ceiling Requirements
Seismic Design Categories D, E, and F
Relative Installation Costs
•
•
•
For Categories D, E, and F, additional
IBC requirements significantly increase
grid costs, resulting in a 100% increase
over Categories A and B.
Some additional time is required to
install panels around the bracing, but
it does not significantly impact costs.
As a result, the total installed cost
for a Category D, E, or F structure
increases to $3.00/ ft2, which is a 50%
increase over standard ceiling systems.
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Estimated Installation Costs
Categories D, E, and F
Item
A, B
D, E, F
Grid
$1.00 / ft2
$2.00 / ft2
Panels
$1.00 / ft2
$1.00 / ft2
Total
$2.00 / ft2
$3.00 / ft2
Note: Total installation costs may vary by
market, however the grid to panel cost
ratio should remain relatively constant.
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IBC Seismic Code and Ceiling Requirements
Course Summary
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IBC Seismic Code and Ceiling Requirements
Course Summary
Today's Seismic Standards
•
The IBC is the first model building code to address differences in seismic hazard
to ceiling systems based on soil type. As such, the IBC requires a "Seismic Design
Category" to be assigned to each project, which results in a three-tiered system
of ceiling installation requirements based on ASTM and CISCA recommendations.
•
Whereas previous codes were primarily concerned with protecting the structural
integrity of buildings, the IBC also recognizes that the failure of non-structural
systems, such as suspended ceilings, can just as easily render a space unusable.
•
In IBC 2000, the installation requirements for suspended ceilings were listed in
Section 1621. In IBC 2003, the information in Section 1621 has been replaced by
ASCE 7-02. Despite this change in referencing, it is important to note that the
installation requirements for suspended ceiling systems have not changed.
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IBC Seismic Code and Ceiling Requirements
Course Summary
Establishing a Seismic Design Category
•
The three key variables used to establish a seismic design category for a given
project are anticipated ground motion, soil class, and seismic use group. Ground
motion is presented as a percentage of the acceleration of gravity (% g), and
values can be obtained from the IBC hazard maps or the U.S. Geological Service.
•
Soil class is typically evaluated by carrying out a soil analysis to a depth of 100' ,
with ratings from A (hard rock) to F (unstable soil). If no soil analysis is carried
out, the soil type or "site classification" typically defaults to a "D" rating.
•
Seismic use group is based on occupancy and how critical the operability of the
facility is in the event of a disaster. Normal Occupancy (Group I) includes most
normal buildings, High Occupancy (Group II) includes schools and office buildings,
and Essential Use (Group III) includes fire and police stations, and hospitals.
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IBC Seismic Code and Ceiling Requirements
Course Summary
Seismic Design Category C
•
For Category C, all structures equal to or greater than three stories, and all
Group III structures, must comply with additional IBC requirements. The only
exception is for Seismic Use Group I (Normal Occupancy) and Group II (High
Occupancy) buildings that are less than three stories tall.
•
Suspended ceilings in Seismic Design Category C must be installed in accordance
with CISCA Seismic Zone 0-2 recommendations. The goal of this standard is to
create an "unrestrained" ceiling that allows movement during a seismic event.
•
These additional requirements include restrictions regarding ceiling weight
(maximum 2.5 lbs / ft2), horizontal flange dimensions (minimum 7/8"), wall
clearance (3/8" to 1/2" depending on Seismic Use Group), connection strength
(minimum 60 lbs), and the use of perimeter spacers to prevent spreading.
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IBC Seismic Code and Ceiling Requirements
Course Summary
Seismic Design Categories D, E, and F
•
For Categories D, E, and F, the IBC requires ceilings to be designed and installed
in accordance with CISCA Seismic Zone 3-4 recommendations as well as eight
additional IBC requirements. In contrast to Category C, the goal for Categories
D, E, and F is to design a restrained ceiling system.
•
These requirements include restrictions regarding horizontal flange dimensions
(minimum 2"), wall clearance (3/4" on unattached sides), hanger wire (12-gauge
wire within 8" of each wall and 4' on center), and the use of perimeter spacers.
•
In addition, main beams must be of "heavy-duty" construction and ceiling areas
greater than or equal to 1,000 ft2 must have lateral force bracing (diagonal splay
wires or rigid bracing), which limits ceiling movement to less than 1/4" at the
point of attachment.
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IBC Seismic Code and Ceiling Requirements
Course Summary
Additional Information
For additional information, please visit the following code-related web sites:
American society for
Testing and Materials (ASTM)
www.astm.org
Federal Emergency
Management Agency (FEMA)
www.fema.gov
Building Seismic
Safety Committee (BSSC)
www.nibs.org
Multidisciplinary Center for Earthquake
Engineering Research (MCEER)
mceer.buffalo.edu
International Code Council (ICC)
www.iccsafe.org
US Geological Service (USGS)
geohazards.cr.usgs.gov
For information specific to your region, please consult your local code professional.
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IBC Seismic Code and Ceiling Requirements
Course Summary
References
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
IBC 1621.2.1 / ASCE 9.6.2.2.
CISCA 0-2, Page 3, Section 4, #3
CISCA 0-2, page 4, Section 1, #5
CISCA 0-2, page 4, Section 1, #6
CISCA 0-2, page 4, Section 1, #7
CISCA 0-2, page 4, Section 4, #2
CISCA 0-2, page 3, Section 4, #1
CISCA 0-2, page 4, Section 1, #4
CISCA 3-4, page 1, Section 2, #1
CISCA 3-4, page 1, Section 2, #2
IBC 1621.2.5.2.2 #2 / ASCE 9.6.2.6.2.2 b.
CISCA 3-4, page 1, Section 4, #1
CISCA 3-4, page 2, Section 1, #2
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(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
(24)
(25)
(26)
CISCA 3-4, page 2, Section 1, #4
IBC 1621.2.5.2.2 #1 / ASCE 9.6.2.6.2.2 a
CISCA 3-4, page 2, Section 3, #2
CISCA 3-4, page 2, Section 2
CISCA 3-4, page 2, Section 3
IBC 1621.2.5.2.2 #3 / ASCE 9.6.2.6.2.2 c.
CISCA 3-4, page 2, Section 1, #3
IBC 1621.2.7 / ASCE 9.6.2.8.1
IBC 1621.2.5.2.2 #5 / ASCE 9.6.2.6.2.2 e.
IBC 1621.2.5.2.2 #4 / ASCE 9.6.2.6.2.2 d
IBC 1621.2.5.2.2 #6 / ASCE 9.6.2.6.2.2 f.
IBC 1621.2.5.2.2 #7 / ASCE 9.6.2.6.2.2 g.
IBC 1621.2.5.2.2 #8 / ASCE 9.6.2.6.2.2 h.
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IBC Seismic Code and Ceiling Requirements
Conclusion of This Program
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