Bulletin No.SRM/2000
Series SCR &
SAB Seismic
Restraints
Seismic
Braces for
Piping,
Ductwork,
Conduit, and
Equipment
VMC Seismic Restraints - Technical Data
VMC Seismic cable restraints (SCR) and single arm
braces (SAB) are an excellent means to restrain
suspended equipment, piping, duct and electrical
cable trays during an earthquake.
With isolated systems, seismic cables are required.
The cables are installed slightly slack so as to avoid
short-circuiting the isolation system. The VMC seismic cable restraints come in kit form to minimize
labor cost for the contractor. Each pre-packaged kit
contains all of the necessary hardware for proper
installation and positive attachment to the building
structure. Our cables are factory swaged on one
end to eliminate extra installation time.
Seismic cable kits are made from 7 x 19 aircraft
cable and are available in 1/8",1/4", and 3/8" sizes.
Non-isolated systems can utilize our single arm
brace. Our SAB series brackets allow for positive
seismic attachment of all suspended systems. The
bracket design accepts field-supplied unistrut or
steel angle and allows for a full range of motion in all
directions for ease of installation. The SAB-1 is
designed for steel attachment, and the SAB-2 is utilized when concrete is the anchoring medium.
Both the VMC Series SCR and Series SAB strictly
comply with all requirements of the national building
codes and the International Building Code (IBC 2000).
1. W = Weight at Center of Gravity
2. fp = Horizontal force by code = "g" x W
3. P Cable = fp
= Force on cable or brace
Cos45°
To determine the approximate seismic load imparted
on the restraint:
1. Determine weight of the equipment, pipe, or duct
to be restrained.
2. Multiply the weight by the seismic acceleration
specified by code to determine horizontal seismic
force.
3. Solve for force on seismic cable or brace by dividing the horizontal seismic force by Cos45°.
Throughout this brochure, you will find graphs and
charts which are to be used as guidelines only.
Many different installation configurations are possible which may effect the performance of the
restraints used.
As a basic rule of thumb, the force acting on the
seismic cable restraint or single arm brace can be
broken down into a static analysis for selection purposes.
Looking at suspended pipe, duct, cable tray or
equipment, you will notice that the seismic restraint
is positioned at an angle of approximately 45° up
from the point of support.
2
VMC Seismic Restraints - Technical Data
Type SCR Seismic Cable Restraints
Each Kit consists of:
2 - lengths of cable - swaged one end -11 ft. long or 20 ft. long,
7 x 19 Galvanized Aircraft Cable, 1/8", 1/4", 3/8" dia.
2 - concrete angle brackets
4 - shackles
2 - thimbles
4 - U-bolts
2 - clevis angles
Seismic Load Table
Wire
Rope Dia.
in.
Recommended
Working Load
lbs.
1⁄ 8
667
942
471
1⁄ 2
31⁄2
1⁄ 4
2330
3292
1646
5⁄ 8
4
3⁄ 8
4200
5936
2968
1
6
Cable Spacing Guide - .5 "G"
Max. Equipment
Weight
.5g
1g
Cable Spacing Guide - 1 "G"
Cable Size and Spacing
1/4"
Cable Size and Spacing
Pipe Size
1/8"
T* - L*
T* - L*
T* - L*
1
40 - 80 ft.
40 - 80 ft.
11⁄4
40 - 80 ft.
11⁄2
3/8"
Pipe Size
1/8"
1/4"
3/8"
T* - L*
T* - L*
T* - L*
40 - 80 ft.
1
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
11⁄4
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
11⁄2
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
2
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
2
40 - 40 ft.
40 - 80 ft.
40 - 80 ft.
21⁄2
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
21⁄2
40 - 40 ft.
40 - 80 ft.
40 - 80 ft.
3
40 - 40 ft.
40 - 80 ft.
40 - 80 ft.
3
30 - 30 ft.
40 - 80 ft.
40 - 80 ft.
4
40 - 40 ft.
40 - 80 ft.
40 - 80 ft.
4
20 - 20 ft.
40 - 80 ft.
40 - 80 ft.
5
30 - 30 ft.
40 - 40 ft.
40 - 80 ft.
5
10 - 10 ft.
40 - 40 ft.
40 - 80 ft.
6
20 - 20 ft.
40 - 40 ft.
40 - 80 ft.
6
10 - 10 ft.
40 - 40 ft.
40 - 80 ft.
8
10 - 10 ft.
40 - 40 ft.
40 - 80 ft.
8
N/A
20 - 20 ft.
40 - 40 ft.
10
10 - 10 ft.
40 - 40 ft.
40 - 40 ft.
10
N/A
20 - 20 ft.
30 - 30 ft.
12
N/A
30 - 30 ft.
40 - 40 t.
12
N/A
10 - 10 ft.
20 - 20 ft.
14
N/A
20 - 20 ft.
40 - 40 ft.
14
N/A
10 - 10 ft.
20 - 20 ft.
16
N/A
20 - 20 ft.
30 - 30 ft.
16
N/A
10 - 10 ft.
10 - 10 ft.
18
N/A
20 - 20 ft.
30 - 30 ft.
18
N/A
N/A
10 - 10 ft.
*T = Transverse
*L = Longitudinal
*T = Transverse
Project:
*L = Longitudinal
VIBRATION MOUNTINGS & CONTROLS, INC.
Architect:
An Aeroflex, Inc. Company
113 Main St. Box 270, Bloomingdale, NJ 07403 Toll Free: 1-800-LOW-VIBE
Tel: 973/838-1780 Fax: 973/492-8430
Acoustician
Contractor:
TYPE "SCR "
SEISMIC RESTRAINTS
Project No.
Date:
Mimimum Recommended
Concrete Anchor (2)
Dia. (in.) Embedment
Drawing No.
3
VMC Seismic Restraints - Technical Data
Single Arm Brace – Type SAB
SAB-1 for equipment and steel
structure attachment
SAB-2 for concrete anchorage
13⁄ 16" hole for
9⁄ 16" hole
(1⁄ 2" concrete
3⁄ 4" bolt
anchors) 2 places
9⁄ 16" holes
8"
6"
for 1⁄2" bolt
9⁄ 16" holes
for 1⁄2" bolt
(6 places)
23⁄4"
4"
11⁄2"
4"
11⁄2"
23⁄4"
Single Arm Brace
Spacing Guide - .5 "G"
Single Arm Brace
Spacing Guide - 1 "G"
Pipe Size
Pipe Size
1
11⁄4
11⁄2
2
21⁄2
3
4
5
6
8
10
12
14
16
18
*T = Transverse
Spacing
T - L
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 40 ft.
40 - 40 ft.
40 - 40 ft.
40 -40 ft.
30 - 30 ft.
20 - 20 ft.
20 - 20 ft.
20 - 20 ft.
*L = Longitudinal
1
11⁄4
11⁄2
2
21⁄2
3
4
5
6
8
10
12
14
16
18
*T = Transverse
Spacing
T - L
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 80 ft.
40 - 40 ft.
40 - 40 ft.
20 - 20 ft.
20 -20 ft.
10 - 10 ft.
10 - 10 ft.
10 - 10 ft.
N/A
*L = Longitudinal
Project:
VIBRATION MOUNTINGS & CONTROLS, INC.
Architect:
An Aeroflex, Inc. Company
113 Main St. Box 270, Bloomingdale, NJ 07403 Toll Free: 1-800-LOW-VIBE
Tel: 973/838-1780 Fax: 973/492-8430
Acoustician
Contractor:
TYPE "SAB"
SEISMIC RESTRAINTS
Project No.
Date:
SAB brackets have been designed to accept
field-supplied unistrut or steel angle as the rigid
brace. Two brackets are required per brace.
Model SAB-1 is used at the equipment, pipe, or
duct and at the building structure when attaching to steel.
When bolting the brace into concrete building
structure, SAB-2 must be utilized. (SAB-1 at
equipment, SAB-2 at structure).
Drawing No.
4
VMC Seismic Restraints - Technical Data
Isolated Piping
Building Structure
Anchor Bolts
by others
Concrete
Angle Bracket
Thimble
VMC Type RSH
Vibration Hanger
Shackle
U-bolt
VMC Series SRBC
Seismic Rod Clamp
7 x 19
Aircraft Cable
Each Cable Kit consists of:
2 - lengths of cable - swaged one end
2 - concrete angle brackets
4 - shackles
2 - thimbles
4 - U-bolts
2 - clevis angles
45°
VMC Series SCR
Seismic Cable Restraint
Clevis
Angle Bracket
Pipe Clevis (secondary pipe clamp
must be used for longitudinal brace)
Typical Transverse Brace
(1 SCR Kit)
Transverse/
Longitudinal
Transverse
Transverse/
Longitudinal
Transverse
Piping must be positively attached to the structure of the
building in case of an earthquake.
Typically, pipe is suspended on vibration isolation hangers
within mechanical equipment rooms, or within 50 feet of
vibrating equipment, whichever is greater. This isolated
piping must also be seismically restrained to the building
structure without compromising the vibration isolation (also
known as "short circuiting"). A "run" of pipe must be
restrained both longitudinally (in the direction of its run)
and transversely (perpendicular to its run) to insure that it
moves with the building and remains attached to it during
an earthquake.
Restraining the isolated pipe is accomplished by utilizing
the VMC series SCR seismic cable restraints. Our seismic
cable restraints insure positive attachment to the pipe supports, and when installed slightly slack, do not compromise the vibration isolation by short-circuiting the spring
hanger.
Our cable kits come with 2 lengths of cable, swaged on
one end, and all of the necessary hardware for easy installation by the contractor. VMC Seismic cable restraints are a
required component when restraining isolated pipe.
TYPE SCR BRACING SCHEMATIC
5
VMC Seismic Restraints - Technical Data
Non-Isolated Piping
SAB-2 required for
concrete attachment.
SAB-1 may be used
for steel attachment
VMC Series SRBC
Seismic Rod Bracing Clamp
Anchor bolts by others
(minimum of 2 for concrete
attachment)
VMC Series SAB-2
Non-isolated
threaded rod
Unistrut or angle
steel (by others)
Longitudinal Brace
(requires additional
pipe clamp at clevis not
shown)
Transverse Brace
VMC Series SAB-1
Clevis Hanger
(pipe clamp must be used for
longitudinal restraint capability)
Non-isolated piping has the same bracing requirements as
isolated piping. However, piping that is rigidly supported
without isolators can be seismically restrained using the
VMC series SAB Single Arm Brace.
Our rigid single arm brace consists of two brackets, which
allow the brace a full range of motion for ease of installation. The bracing material (typically unistrut or angle steel)
is contractor supplied and cut to size in the field. The
brace brackets are available in two sizes and incorporate
properly sized and spaced anchor bolt holes. The SAB-1
is designed for attachment to the pipe hanger and anchoring into steel. The SAB-2 incorporates two anchor bolt
holes for attachment to concrete. Unlike cable restraints,
which require 2 cables per brace location, the SAB series
requires only one brace per transverse location and one
brace per longitudinal location. An example on ordering
the SAB series is as follows:
Transverse brace anchored into concrete requires:
1 pc SAB-1 (for the attachment at the pipe hanger)
1 pc SAB-2 (for the attachment of the brace to the concrete ceiling)
OR
Transverse brace anchored into steel requires:
2 pcs SAB-1 (1 pc for attachment to the pipe hanger, 1 pc
for attachment to the steel structure)
Transverse/
Longitudinal
Transverse
Transverse/
Longitudinal
Transverse
TYPE SAB BRACING SCHEMATIC
6
VMC Seismic Restraints - Technical Data
Isolated Suspended Equipment
NOTE: Equipment must be
positively attached to
support steel
VMC Type RSH Hanger
VMC Series SCR
(2 kits required per piece
of equipment)
Hanger Rods (by others)
Support Steel (by others)
All suspended mechanical equipment must be seismically restrained. While floor mounted equipment
typically utilizes a seismically rated vibration isolator
or separate snubber, no such device exists for suspended equipment. This is because suspended
equipment can have any number of possible elevations.
Fortunately, it is possible to seismically restrain isolated suspended equipment by using VMC Series
SCR Seismic Cable Restraints. Series SCR cable
restraints are required for externally isolated equipment only.
Each piece of equipment requires a minimum of 4
cables, (2 SCR kits) installed slightly slack to insure
continuity of the vibration isolation system.
The cables are installed at 45° from the horizontal
plane of the equipment, and in plan view, 45° from
each corner.
The diameter of the cable is determined through calculation and is based on the weight of the equipment and specified seismic force.
Seismic Load Table
Wire
Rope Dia.
in.
Recommended
Working Load
lbs.
1⁄ 8
667
1⁄ 4
2330
3⁄ 8
4200
Max. Equipment
Weight
.5g
1g
Mimimum Recommended
Concrete Anchor (2)
Dia. (in.) Embedment
471
1⁄ 2
31⁄2
3292
1646
5⁄ 8
4
5936
2968
1
6
942
7
VMC Seismic Restraints - Technical Data
Non-Isolated
Suspended Equipment
Plan View
VMC SAB-1
Threaded Rod (by others)
VMC SAB-2
Structural Steel (by others)
Non-isolated or internally isolated
suspended equipment can be
seismically restrained utilizing the
VMC Series SAB Single Arm
Brace.
Any internal isolation must have its
own seismic capability certified by
the unit manufacturer. While externally isolated suspended equipment requires a minimum of 4
cables, the SAB series brace can
use as few as two braces per
application.
The braces are installed at 45° up
from the horizontal plane of the
equipment, and perpendicular to
each other at either end of the
equipment.
Electrical Cable Trays
VMC SAB-2
VMC SAB-2
Cable Tray
Longitudinal Brace
(unistrut by others)
VMC SAB-1
Transverse Brace
(unistrut by others)
VMC SAB-1
8
The electrical system in a building
is perhaps the most important part
of the HVAC system. Should the
power be interrupted due to inadequately restrained electrical systems, the HVAC system will be rendered inoperable, and the building
useless. While we typically take
great strides to insure that the
mechanical equipment, pipe and
ductwork are properly restrained,
the electrical system is often overlooked.
Any electrical conduit, cable trays,
etc. used to supply power to the
HVAC or emergency backup systems must be properly restrained
using the VMC Series SAB Single
Arm Brace.
VMC Seismic Restraints - Technical Data
Isolated Ductwork
Anchor Bolts
(by others)
Building Structure
Concrete Angle Bracket
Shackle
VMC Type RSH
Vibration Hangers
U-bolts
Thimble
Each Kit consists of:
2 - lengths of cable - swaged one end -11 ft. long or 20 ft. long,
7 x 19 Galvanized Aircraft Cable, 1/8", 1/4", 3/8" dia.
2 - concrete angle brackets
4 - shackles
2 - thimbles
4 - U-bolts
2 - clevis angles
Transverse/
Longitudinal
Transverse
Transverse/
Longitudinal
Lower Angle Bracket
Duct: (6 square feet and larger
requires restraint)
Ductwork must be positively attached to the structure of
the building in case of an earthquake. Isolated duct must
be seismically restrained to the building structure without
compromising the vibration isolation (also known as "short
circuiting").
A "run" of duct must be restrained both longitudinally (in
the direction of its run) and transversely (perpendicular to
its run) to insure that it moves with the building and
remains attached to it during an earthquake. Restraining
the isolated duct is accomplished by utilizing the VMC
series SCR seismic cable restraints. Our seismic cable
restraints insure positive attachment to the ductwork, and
when installed slightly slack, do not compromise the vibration isolation by short-circuiting the spring hanger.
Our cable kits come with 2 lengths of cable, swaged on
one end, and all of the hardware shown above for easy
installation by the contractor. VMC Seismic cable restraints
are a required component when restraining isolated duct.
Transverse
SCR BRACING SCHEMATIC
9
VMC Seismic Restraints - Technical Data
Non-Isolated Duct Work
Anchor bolts
(by others)
Non-isolated
threaded rod
SAB-2 required for
attachment to concrete.
SAB-1 may be used for
attachment to steel
Longitudinal brace
(unistrut by others)
Transverse brace
(unistrut by others)
SAB-1
Duct: (6 square feet and larger
requires restraint)
Transverse/
Longitudinal
Transverse
Transverse/
Longitudinal
Transverse
TYPE SAB BRACING SCHEMATIC
Non-isolated duct has the same bracing requirements as
isolated duct. However, duct that is rigidly supported without isolators can be seismically restrained using the VMC
series SAB Single Arm Brace.
Our rigid single arm brace consists of two brackets, which
allow the brace a full range of motion for ease of installation. The bracing material (typically unistrut or angle steel)
is contractor supplied and cut to size in the field. The
brace brackets are available in two sizes and incorporate
properly sized and spaced anchor bolt holes. The SAB-1
is designed for attachment to the ductwork and anchoring
into steel. The SAB-2 incorporates two anchor bolt holes
for attachment to concrete. Unlike cable restraints, which
require 2 cables per brace location, the SAB series
requires only one brace per transverse location and one
brace per longitudinal location. An example on ordering
the SAB series is as follows:
Transverse brace anchored into concrete requires:
1 pc SAB-1 (for the attachment at the duct)
1 pc SAB-2 (for the attachment of the brace to the
concrete ceiling)
OR
Transverse brace anchored into steel requires:
2 pcs SAB-1 (1 pc for attachment to the duct, 1 pc for
attachment to the steel structure)
10
VMC Seismic Restraints - Technical Data
Seismic Rod Bracing Clamp
SRBC Rod
Bracing Clamp
Seismic forces act in all directions. Because the threaded
rod is sized purely for gravity loads, it is necessary to add
additional rod bracing to prevent buckling. Uplift forces
can easily exceed the dead load on the rod resulting in
compressive forces. If un-braced the rod can buckle and
fail. With the addition of the VMC series SRBC bracing
clamp, angle steel bracing can be quickly and easily
added to the rod, stiffening and strengthening it.
When vibration hangers are utilized, VMC recommends
attaching the hanger directly to the overhead structure and
adding an uplift washer under the box to prevent the
spring from becoming unloaded.
Clamp Sizing Table:
Used with
Size
Angle Size
SRBC-11⁄4
1" x 1" x 1⁄4"
SRBC-11⁄2
11⁄2" x 11⁄2" x 1⁄4"
Hanger Rod Sizes
3⁄ 8", 1⁄ 2", 5⁄ 8"
3⁄ 4", 7⁄ 8",
1", 11⁄8"
Note: Three clamps are required per rod. Clamps are
furnished complete with bolt and nut as illustrated.
Project:
VIBRATION MOUNTINGS & CONTROLS, INC.
Architect:
An Aeroflex, Inc. Company
113 Main St. Box 270, Bloomingdale, NJ 07403 Toll Free: 1-800-LOW-VIBE
Tel: 973/838-1780 Fax: 973/492-8430
Acoustician
Contractor:
TYPE "SCR "
SEISMIC RESTRAINTS
Project No.
Date:
Drawing No.
11
Vibration Mountings & Controls, Inc.
An Aeroflex, Inc. Company
113 Main Street, Box 270, Bloomingdale, NJ 07403
Tel: 973/838-1780 TOLL FREE: 1-800-LOW-VIBE Fax: 973/492-8430
©Vibration Mountings & Controls, Inc.
5M 4/2000