SEISMIC BRACING OF HVAC SYSTEMS FOR LDS TEMPLES 12 APRIL 2013 KDK ENGINEERING KEVIN COUCH, DAVID DE KOCK, KIRSTEN HINDS AND JASON HIRSCHI DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING IRA A. FULTON COLLEGE OF ENGINEERING AND TECHNOLOGY BRIGHAM YOUNG UNIVERSITY
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SEISMIC BRACING OF HVAC SYSTEMS FOR LDS TEMPLES
12 APRIL 2013
KDK ENGINEERING
KEVIN COUCH, DAVID DE KOCK, KIRSTEN HINDS AND JASON HIRSCHI
DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERING AND TECHNOLOGY
BRIGHAM YOUNG UNIVERSITY
EXECUTIVE SUMMARY
Seismic bracing of ducts and pipes has become a standard requirement for most modern buildings, but it
is often not installed correctly or completely overlooked. The Church of Jesus Christ of Latter-day Saints (LDS) is,
therefore, concerned with ensuring that all necessary components in their structures are correctly secured to
ensure the safety of its members and continued use of the structure after a seismic event. The details, bracing
length constraints and specifications in this project address this problem in providing clear requirements to be
adhered to for bid submittals and construction. This will allow the LDS church to equally compare bid submittals
and inspect construction according to these requirements.
Recommendations for specifications were provided to clarify and state requirements regarding the
American Society of Civil Engineers (ASCE) 7-10 Chapter 13, submittals and force design, bracing and spacing
requirements. Various details for ductwork bracing were produced in reference with ASCE 7-10 and Sheet Metal
and Air Conditioning Contractors’ National Association (SMACNA) including rectangular transverse, round
transverse, longitudinal and equipment bracing. These generic details provide a template for contractors
submitting designs of the details required. Lastly, brace spacing requirements were specified according to ASCE 7-
10 and recommendations from professional engineers. These provide maximum allowable spacing between braces
to ensure consistent and sufficient designs.
This report, which deals specifically with LDS temple structures, is expected to be used as a guideline for
design professionals when specifying the seismic requirements of all ductwork for LDS temple projects. Design
engineers specializing in seismic restraint, mechanical contractors, and seismic design standards and codes were
consulted in the formulation of the guidelines that comprise this report. When used in the creation of seismic
bracing specifications, this project will assist in ensuring that the seismic bracing of LDS temple ductwork and its
associated components is performed in a high-quality, predictable, and consistent manner.
APPENDIX A ............................................................................................................................................................. 10
� Cable and rigid braces shall not be combined on one run.
� Seismic restraints shall not inhibit isolation systems.
� Duct:
o Where duct Ip=1.25, brace all rectangular duct greater than and equal to 6 ft2, all round
duct greater than 33” dia.
o Where duct Ip>1.25, brace all duct > 5lb/ft.
� Equipment items installed in-line and rigidly mounted at the inlet and outlet to the duct system
(e.g. fans, heat exchangers and humidifiers) with an operating weight less than 75 pounds need
not be braced if the duct run it is attached to is braced. Equipment with an operating weight
greater than 75 lbs. must be braced and supported independent of the duct.
� Brace spacing for low deformability duct shall not exceed one half of the brace spacing of high
deformability duct.
� Bracing brackets shall be designed to yield in a ductile manner prior to achieving a load
level which would result in non-ductile concrete cone pullout failure. This ductility shall
be demonstrated by psuedostatic cyclic testing. An OSPHD approval of bracket design values
shall be considered as adequate demonstration of bracket ductility. Alternately, if cyclic testing
is not available, maximum brace spacings in the table presented on the brace spacing details
sheet shall be reduced by 50%.
Connections
� If shot pin anchors are allowed, walls shall be designed for those forces and verified with wall
structural engineer.
� If the area of influence for multiple anchors overlap, group affects shall be taken into account.
� Anchor type shall satisfy the requirements for the parent material.
� Anchor must be positively fastened without consideration of frictional resistance produced by
effects of gravity.
� Design documents must contain sufficient information relating to the attachments to verify
compliance with ASCE 7-13.4.
� Anchors and supports must be designed for the same forces and displacements, as per ASCE 7-
13.6.5.
� All post installed anchors utilized in the seismic design must be qualified for use in cracked
concrete and approved for use with seismic loads.
� All beam clamps utilized for vertical supports must also incorporate retention straps.
� All seismic brace arm anchorages to include concrete anchors, beam clamps, truss connections,
etc. must be approved for use with seismic loads.
� Gravity supports must be designed by a licensed engineer in the project state for systems
subject to seismic requirements as listed above. Gravity supports include primary support and
anchorage of all distributed systems, riser supports, and supports for floor mounted utilities.
Design to include seismic loads in conjunction with dead loads as required by the IBC/ASCE 7.
APPENDEX B
KDKENGINEERING
KEVIN COUCH
DAVID DE KOCK
KIRSTEN HINDS
SEISMIC BRACING OF HVACSYSTEMS OF LDS TEMPLES
KDK ENGINEERINGKEVIN COUCH, DAVID DE KOCK, KIRSTEN HINDS
DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERINGIRA A. FULTON COLLEGE OF ENGINEERNIG AND TECHNOLOGY
BRIGHAM YOUNG UNIVERSITY
<= Max Longitudinal Brace Spacing
TTL
L
T - Transverse Brace LocationL - Longitudinal Brace
LocationX- Gravity Support
T
T
1. The spacing of seismic bracing of ductwork or pipes shall be determined by seismic analysis based on the requirements of ASCE 7-10.This design shall be performed by a licensed structural engineer in responsible charge for nonstructural seismic bracing design(NSE).
2. The NSE shall coordinate this design with the building design Structural Engineer of Record (SER) and the Mechanical Engineer ofRecord (MER). Maximum brace spacing shall not exceed values which would exceed allowable limits on the building or facility structure,as provided by the SER.
3. Each straight run of ductowrk or pipe should be installed with a minimum of two transverse braces perpendicular to the ductworkand one longitudinal brace installed parallel to the ductwork, as shown in the Figure 1.
4. Transverse seismic braces should be installed at the final gravity support point of each run of duct or pipe that has two or more gravitysupports. If the distance between the seismic braces exceeds the maximum calculated transverse brace spacing in the following relevanttable, then additional transverse seismic braces shall be located to limit the seismic brace spacing to the maximum calculated transversespacing.
5. A longitudinal brace must be located on each straight run of duct greater than 8' in length and each run of pipe with lengthgreater than the calculated longitudinal seismic brace spacing. Additional seismic braces shall be located on the run tolimit the seismic brace spacing to the maximum longitudinal brace spacing.
6. A transverse brace located within two duct widths of a 90 degree turn can provide some longitudinal bracing for thestraight run of duct around the turn. The length of ductwork longitudinally braced by this transverse brace is equal to onehalf the maximum transverse brace spacing minus the distance from the transverse brace to the turn, as shown in Figure 2.For pipes this may apply if the transverse brace is within the offset length from the offset length table. The lengthof pipe that may supported longitudinally is one half the maximum transverse brace spacing minus the distance from thetransverse brace to the turn.
TSupport Point
The following steps and figures shall be used to determine the distance of brace spacing. Brace spacing shall notexceed the lesser of the following:
1. Duct brace spacing schedule for duct2. Pipe brace spacing schedule for pipe3. Pipe Brace Spacing provided by the NSE2. Capacity of the structure to resist brace load3. Connection strength of the brace to the duct or pipe4. Brace Capacity5. Capacity of duct or pipe to span between braces
The Structural Engineer of Record(SER) and Mechanical Engineer of Record(MER) must provide the capacity of connectedparts of the structure to the Non-Structural Engineer (NSE).
Seismic supports are referred to as either lateral or transverse bracing, other supports are referred to as gravity supports.
Figure 1
2 times Duct Width or Maximum offset length(for pipes)
Duc
t Wid
th
Leng
th=
1/2
Cal
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Tra
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Bra
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paci
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2*D
uct W
idth
Figure 2
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SEISMIC BRACINGOF HVAC SYSTEMSDESIGN FOR LDS
TEMPLES
WINTER 2013
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7. If a straight run of ductwork or pipe has less than two gravity support points, is connected to a braced straight runof ductwork or pipe at each end, and its total length is less than two duct widths for duct or the maximum offsetlength in the table below for pipe, brace across the run by adding its length to the transverse and longitudinalbrace design of the connected runs. If its length is greater than two duct widths for duct or the maximum offsetlength for pipe in the table below, a support point with a transverse brace is required, as shown in Figure 3 and 4.
T
T L
L<= Max. Transverse Braces Spacing - Offset
<= Max Longitudinal Brace Spacing
<=
2x
Duc
t Wid
th
8. Vertical drops to equipment require a transverse brace at the final gravity support location before the ductwork or pipe drops. Thetotal length of the ductwork from the support point to the equipment connection or flexible connector shall be less than halfthe maximum spacing of the transverse brace, and the length of ductwork or pipe from the support point to the drop should be lessthan two duct widths for pipe or the applicable maximum offset length from the pipe brace spacing schedule, as shown in the figure 5.
Offest Length<= 2x Duct Width or Maximum offset Length(for pipes)
<=
Max
Tra
nsve
rse
Bra
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paci
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Offs
et L
engt
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9. Bracing brackets shall be designed to yield in a ductile manner prior to achieving a load level which would result innonductile concrete cone pullout failure. This ductility shall be demonstrated by psuedostatic cyclic testing. An OSPHDapproval of bracket design values shall be considered as adequate demonstation of bracket ductility. Alternately, ifcyclic testing is not available, maximum brace spacings in the Duct Brace Spacing Schedule and the Pipe Brace SpacingSchedule shall be reduced by 50%.
10. Do not mix solid bracing with cable bracing in the same direction on any duct or pipe run.
11. Duct and Pipe seismic bracing design shall consider mechanical vibration and thermal loading using vibration and thermalrequirements provided in mechanical specifications.
Figure 3: Offset With No Transverse Brace Required
T
T L
L<= Max. Transverse Braces Spacing - Offset
<= Max Longitudinal Brace Spacing
Figure 4: Offset With Transverse Brace Required
>=
2x
Duc
t Wid
th
Gravity Support
Transverse Brace
45.00°
Figure 5
12. Cable bracing shall be in a straight line to the structure, it shall not touch other ductowrk, piping, or other buildingcomponents.
KEVIN COUCH, DAVID DE KOCK AND KIRSTEN HINDSDEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERINGIRA A. FULTON COLLEGE OF ENGINEERING AND
TECNOLOGYBRIGHAM YOUNG UNIVERSITY
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KDK ENGINEERING
KDK
SPACING TABLES
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NOTES LDS
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SEISMIC BRACINGOF HVAC SYSTEMSDESIGN FOR LDS
TEMPLES
WINTER 2013
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Mechanical and Electrical components listed in this Schedule shall be braced and shall conform to ASCE 7-10 Chapter 13Seismic Design Category Notes Clarification
Seismic Design Categories A and BNo seismic bracing is required
Seismic Design Category CFire protection sprinkler systems: This includes all mechanical and electrical components required for the fire protectionsprinkler system to operate following an earthquake, such as: piping, fire pumps, fire pump control panels, water tanks, firedampers, smoke dampers, smoke exhaust systems, generators, transfer switches, switches, emergency lighting systems,and other life-safety systems or systems supporting life-safety systems.
Pipes and Components with Ip = 1.5Special Bracing Excpetions for Piping (does not apply to fire protection sprinkler piping)
Piping with Rp = 4.5 (per Table 13.6-1 ofASCE 7-10) or greater, and with Ip = 1.5 orless, and with nominal diameter of 2 inches(50 mm) or less, and spaced to avoid impactwith other ducts, piping, or architecturalcomponents, need not be braced.
Seismic Design Category D, E, and FFire protection sprinkler systems as noted in Seismic Design Category CAll components without flexible connections between the component and associated ductwork, piping, and conduit.All components with flexible connections between the component and associatedAll components with flexible connections between the component and associatedductwork, piping, and conduit that weigh more than 20 lbf (89 N), and have acenter of gravity greater than 4 feet (1.22 m) above the adjacent floor.
All distributed systems without flexible connections between the component andassociated ductwork, piping, and conduit.Distributed systems with flexible connections between the component andassociated ductwork, piping, and conduit that weight more than 5 lbf (73 N/m).
Importance Factors
DescriptionCode
RequirementLDS
Requirement Notes
Sprinkler systems (including all mechanical and electrical componentsrequired for the fire protection sprinkler system to operate following anearthquake) and other life-safety components required by ASCE 7-1013.1.3.
Ip = 1.5 Ip = 1.5
All Other Systems Ip = 1.0 Ip = 1.25 Use Ip = 1.25 only to calculate loads. for all other coderequirements assume Ip = 1.0
The following bracing exceptions are allowed; however, flexibleconnections must be provided between un-braced
Type Exception
Speciacl Exceptions for DuctworkDuctwork weighing less than 17 lbf/ft (248 N/m) (including the acoustical ductliner) or having a cross sectional area less than 6 ft2 (0.557 m2), spaced to avoidimpact with other ducts, piping, or architectural components need not bebraced. If not spaced to avoid impact with other ducts, piping, or architecturalcomponents, then an engineer must certify that impacts with such will notcause damage to such components. Otherwise ducts must be braced.
Ductwork supported by hangers when the distance from the top of the ductto the structure support point is 12 inches or less, AND a swivel is used on rodhangers, need not be braced.
Ductwork supported by a trapeze assembly when the total weight of theductwork supported by the trapeze is less than 10 lbf/ft (146 N/m), the trapezeneed not be braced.
Special Exceptions for Piping *Does not apply to fire protection sprinkler pipingPiping with Rp = 4.5 (per Table 13.6-1 of ASCE 7-10) or greater, and with Ip =1.5, and with nominal diameter of 1 inch (25 mm) or less, and spaced to avoidimpact with other ducts, piping, or architectural components, need not bebraced.
Piping with Rp = 4.5 (per Table 13.6-1 of ASCE 7-10) or greater, with Ip < 1.5,and with nominal diameter of 3 inches or less, and spaced to avoid impact withother ducts, piping, or architectural components, need not be braced.
Piping supported by hangers when the distance from the top of the pipe tothe structure support point is 12 inches or less, AND a swivel is used on rodhangers, need not be braced.
Piping supported by trapezes when the distance from trapeze to the structuresupport point is 12 inches or less, AND a swivel is used on rod hangers, neednot be braced.
Piping supported by a trapeze assembly when the total weight of all piping isless than 10 lbf/ft (146 N/m), and no pipe supported by the trapeze exceed 3inches (75 mm) for Ip < 1.5 or 1 inch (25 mm) for Ip = 1.5, the trapeze need notbe braced.