SECTION 20 05 49
SEISMIC RESTRAINT SYSTEMS - PLUMBING
PART 1 - GENERAL
1.1
DESCRIPTION
A. This specification covers design and installation of seismic bracing and anchorage required for
piping, ductwork, and equipment. Contractor is responsible for design and installation of
seismic bracing and anchorage systems.
B. Description of systems:
1. Transverse and longitudinal bracing for seismic forces on suspended mechanical systems
including piping, ductwork, and equipment.
2. Anchorage of floor and roof mounted mechanical equipment
C. Seismic bracing of vibration isolated equipment:
1. See Section 20 05 50
Meet Quality Assurance requirements specified herein.
1.2
QUALITY ASSURANCE
A. Seismic design requirements.
1. Seismic design criteria: Provide bracing and anchoring for equipment, piping, ductwork,
stacks and breeching designed, constructed, and installed to resist stresses produced by
lateral forces specified under the authority below:
a. IBC ( ______ year), for Seismic Design Category _____.
b. UBC ( ____ year), for Seismic Zone ____.
c. California Administrative Code, Title-22 and Title-24.
d. Applicable local codes.
B. Design and install seismic anchorage and bracing for all floor or roof mounted equipment
weighing 400 pounds or more and all suspended or wall mounted equipment weighing 20
pounds or more.
C. The following components are exempt from the requirements of this section:
1. Mechanical components in structures assigned to Seismic Design Category C provided that
the importance factor (Ip) is equal to 1.0.
2. Mechanical components in Seismic Design Categories D, E, and F where Ip = 1.0 and
flexible connections between the components and associated ductwork and piping are
provided and that are mounted at 4 FT or less above a floor level and weigh 400 lb or less.
3. Mechanical components in Seismic Design Categories D, E, and F weighing 20 lb or less
where Ip = 1.0 and flexible connections between the components and associated ductwork
and piping are provided, or for distribution systems, weighing 5 lb/ft or less.
D. For this project, the following seismic coefficients shall be used in calculating the required
lateral force:
1. SDS = ______ (IBC)
2. Ca = _____ (UBC)
3. Ip = ______
4. Ip= 1.0, except as noted below:
a. Ip= 1.5, for all life safety and critical systems including:
1) Fire protection.
2) Smoke Control.
3) Fuel piping.
4) Medical gas piping.
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5) Additional systems as defined by applicable codes.
E. All lateral forces shall be presumed to act through the components center of gravity
1.3
INSTALLATION INSPECTION
A. Certify that seismic bracing system installed is in accordance with approved shop drawings
B. Certifier qualifications:
1. Pre-engineered systems: Qualified factory representative.
2. Custom engineered systems: Design engineer as identified under submittal requirements.
1.4
SUBMITTALS
A. Shop Drawings:
1. Layout and mounting detail drawings showing system and proposed brace locations for all
systems including pre-engineered systems.
2. The specific detail for each type of brace or anchor must be referenced on a plan that
identifies the required location. Supplying a book of details without referencing the proper
detail to a specific location on a plan is not acceptable.
3. All submittals, including pre-approved systems, shall be signed and sealed by a registered
Engineer, licensed to practice Structural Engineering in the state in which the project is
located.
B. Product Data:
1. Technical data on seismic control devices.
C. Project Information:
1. Structural calculations for required lateral force level for each component.
PART 2 - PRODUCTS
2.1
SUSPENDED BRACING SYSTEMS
A. Acceptable manufacturers:
1. Pre-Engineered systems:
a. Base:
1) Mason Industries.
b. Optional:
1) Amber/Booth Company.
2) Vibro-Acoustics.
3) Vibration Mountings and Controls.
c. Other manufacturers desiring approval shall comply with Section 00 26 00.
2. Custom engineered systems designed using specified criteria and common building
materials.
2.2
EQUIPMENT ANCHORS AND SUPPORTS
A. Drilled-in-place concrete anchors shall have an approved ICBO Evaluation Services Report.
B. Cast-in-place anchors shall comply with ASTM-A36, ASTM-A307, or ASTM-F1554-36.
C. Anchors permanently exposed to weather or corrosive environments shall be stainless steel or
hot-dipped galvanized.
D. Structural steel for supports: ASTM-A36.
E. Cold formed metal and connection material: Unistrut or equal
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F. Any details provided are based on assumed equipment and arrangement. Design and acquire
approval for support and anchorage of equipment and arrangement which varies from equipment
and arrangement assumed in detail provided.
PART 3 - EXECUTION
3.1
GENERAL REQUIREMENTS
A. Design and install all bracing and anchoring for equipment, piping, ductwork, stacks and
breeching in accordance with the requirements of this specification
B. Every run which requires bracing shall have a minimum of two Transverse Braces and one
Longitudinal Brace.
C. A “run” is defined as suspended pipe, duct or trapeze rack having a minimum 5 FT straight run
length.
D. Brace spacing shall not exceed the maximum allowable brace spacing as engineered by the
manufacturer or custom bracing designer.
E. Bracing may be omitted from piping, ductwork, conduit, cable tray and bus duct runs less than 5
FT in length.
F. Except for sprinkler piping, bracing may be omitted from piping and ductwork runs where rod
hung supports of less than 12 IN in length are required, subject to the following:
1. All unbraced suspended ductwork and other unbraced suspended utility systems are to be
installed with a minimum 6 IN clearance to suspended ceiling vertical hanger wires.
2. The piping, or ductwork shall be installed such that the lateral motion of the members will
not cause damaging impact with other systems or structural members or loss of vertical
support.
3. All supports are less than 12 INRod hung supports less than12 INshall not create moment
forces on the hanger rod.
G. A longitudinal brace at a 90 deg. change in direction may act as a Transverse Brace if it is
located within 2 FT or two duct widths, which ever is greater, of the change in direction.
H. A Transverse brace may act as a longitudinal brace if it is located within 2 FT or 2 duct widths,
whichever is greater, of a change in direction and if the brace arm and anchorage have been
sized to meet or exceed the requirements of the Longitudinal Brace.
I.
When bracing equipment or a utility system that is suspended from an overhead deck, brace back
to the overhead deck or to the supporting structure supporting the deck. Do not brace to another
element of the structure which may respond differently during a seismic event.
J.
Obtain approval from the Structural Engineer prior to attaching to any brace elements to
structural steel or wood framing.
K. When utilizing cable bracing, tension the cable to remove slack without inducing uplift of the
suspended element. Tension seismic bracing system prior to system start up and adjust if
necessary after equipment start up.
L. As a general rule, do not mix rigid bracing with cable bracing in the same run. However, once
bracing has transitioned a 90 degrees change in run direction, the bracing may switch from rigid
to cable or vice versa if required due to a significant change in overhead deck elevation or to
provide an implementable bracing scheme in a congested area.
M. Install brace members at an angle of 45 degrees from horizontal within a tolerance of plus 2 1/2
degrees or minus 45 degrees provided the brace length is accounted for in design. Brace angle
may be increased to 60 degrees provided the brace spacing is reduced to 1/2 that required for a
45 degree brace.
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N. Seismic bracing may not pass through a building separation joint. Utility systems that pass
through a separation joint must be seismically restrained within 5 FT of point of connection or
any hardware designed to accommodate seismic movement across the span of the separation
joint.
O. With approval of the Structural Engineer, utility systems within a basement that are suspended
from the overhead deck may be braced to load bearing basement walls provided that the walls
and the overhead decks will respond similarly during a seismic event.
P. Each layer of a multiple layer trapeze rack shall be braced individually based on the weight of
the individual layer.
Q. Pipes or ductwork constructed of non ductile material (plastic, fiberglass, or no hub cast iron),
shall have brace spacing reduced to 1/2 of the spacing allowed for ductile materials. In addition,
no hub cast iron piping shall be braced on either side of a horizontal 90 degree change in
direction and when installed as a riser, shall include the use of a joint stabilizer where the joints
are unsupported between floors.
R. Where brace elements are through-bolted, the mounting hole in the element is to be no more
than 1/16 IN diameter larger then the bolt or threaded rod.
S. Seismic braces shall directly brace system and not hanger.
3.2
SUSPENDED PLUMBING, MECHANICAL AND PROCESS PIPING
A. Install seismic bracing for pipe runs meeting the following parameters:
1. All fuel, medical gas and medical vacuum piping with diameters equal to or greater than 1
IN.
2. All other piping (regardless of use) with diameters equal to or greater than 2-1/2 IN.
B. All trapeze assemblies supporting pipes shall be braced considering the total weight of the
elements on the trapeze computed as pounds per lineal feet.
C. Unless an individual element or trapeze would otherwise require bracing, brace trapezes with a
minimum weight in excess of 10 lbs per lineal foot.
D. For the purpose of calculating weight, all piping is to be treated as full of water.
E. Locate seismic bracing no more than 10 FT from each main riser, at every piece of equipment,
and at the entrance to the building.
F. Do not use branch lines to brace main lines.
G. At vertical pipe risers, wherever possible, support weight of riser at a point or points above
center of gravity of riser.
H. Provide lateral guides at the top and bottom of the riser, and at intermediate points not exceeding
30 FT on center.
3.3
I.
The bracing requirements and installation details for piping anchors and guides designed to
accommodate thermal pipe movement are require custom analysis and design. Thermal pipe
stress analysis and anchor /guide design shall be undertaken by a licensed engineer trained in
thermal pipe stress analysis. Seismic forces and detail requirements as specified in this section
shall be included in the design of such anchors and guides.
J.
Individually supported pipes on rollers or hangers suspended from dual threaded rods shall
employ a top roller in contact with the top of the pipe to prevent uplift during a seismic event.
HVAC DUCTWORK AND SUSPENDED HVAC EQUIPMENT
A. Install seismic bracing on HVAC ducts meeting the following parameters:
1. All rectangular air handling ducts equal to or greater than 6 square feet in cross sectional
area.
2. All round air-handling ducts with diameters equal to or greater than 28 IN.
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B. All trapeze assemblies supporting ducts shall be braced considering the total weight of the ducts
on the trapeze.
C. In line equipment rigidly mounted to the duct shall be braced independently of the duct work if
the unit weighs 50 pounds or more. If the equipment is flexibly connected to the ductwork,
independently brace all equipment weighing 20 pounds or more. All mechanical piping
connections to the equipment are to be flexible. The nearest transverse brace for the connected
duct shall be at a distance away from the equipment of no more than 1/2 the transverse brace
spacing required.
D. Vertical duct runs which are mechanically attached to floors at a point of penetration may be
considered as a transverse and longitudinal brace location provided the anchorages and the duct
framing accommodate the engineered load and provided the distance to the nearest 90 degree
change in direction is no more than two duct widths.
3.4
FIRE PROTECTION PIPING
A. Install lateral (transverse) seismic bracing spaced no more than 40 FT on center on all feed and
cross mains and all branch lines and other piping 2 ½ IN diameter and larger.
B. Install lateral (transverse) seismic bracing on the last length of pipe and at the end of a feed or
cross main. The distance between the end of the pipe and the last brace shall not exceed 20 FT.
C. Install longitudinal bracing at a maximum of 80 FT on center for feeds and cross mains
D. Seismic bracing may be omitted from sprinkler piping suspended by individual hangers 6 IN or
less in length from the top of the pipe to the bottom of the structural attachment for the hanger
provided the hanger rods are constructed in such a manner as to not produce bending in the rod
or the attachment.
E. For the purpose of calculating weight, all piping is to be treated as full of water.
F. Tops of vertical riser piping shall be seismically braced using 4 way bracing.
3.5
FLOOR OR ROOF MOUNTED EQUIPMENT
A. Provide one anchor on each leg or support with a minimum of three 3/8 IN diameter anchors.
B. Friction shall be neglected when designing anchors for shear.
C. Seismic forces shall be presumed to act through the center of mass of the equipment in a
direction that will produce the largest single anchor force.
D. Vertical seismic forces, when required, shall be presumed to act concurrently with horizontal
seismic forces.
END OF SECTION
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