seismic bracing of hvac systems for lds...

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.

TABLE OF CONTENTS

Executive summary .................................................................................................................................................... 2

Introduction ............................................................................................................................................................... 4

Design ........................................................................................................................................................................ 5

Specifications ......................................................................................................................................................... 5

Details .................................................................................................................................................................... 7

Minimum Bracing Design ....................................................................................................................................... 8

Conclusion ................................................................................................................................................................. 9

APPENDIX A ............................................................................................................................................................. 10

APPENDIX B.............................................................................................................................................................. 11

INTRODUCTION

The Church of Jesus Christ of Latter-Day Saints (LDS) is continually announcing and constructing new

temples around the world. There are 140 temples currently in operation, 12 under construction, and 16

announced. As these new temples are built, they are used daily for worship, and therefore, built according to the

highest standards. The mechanical system seismic bracing is important to maintaining a functional building and

reducing damage after a seismic event. Our team provided the LDS church with a guideline for the creation of a

seismic restraint specification section as well as standard details drawn in Revit, to ensure that proper seismic

bracing is provided in newly constructed temples as well as retrofits.

Without standard specifications and details specific to the seismic bracing of LDS temples, it is difficult for

the LDS church to compare designs and costs provided by various contractors due to the varying methods of

design. The church has also encountered problems with ensuring that seismic bracing has met their expectations.

These specifications and details allow all parties to be informed of what is expected in a project's seismic bracing

design and installation, prior to bid and for the duration of a project. The LDS church will be able to clearly

communicate their requirements and expectations and receive equally satisfactory bids that can be compared

against specific standards for inspecting completed work.

The details consist of standard Revit drawings of square and round ductwork bracing for transverse and

longitudinal applications, as well as the bracing of hanging equipment. There are also details and an associated

table containing minimum bracing lengths for longitudinal and transverse bracing as well as the combination of

both. The specification document contains lists of specific items an engineer needs to include in the seismic

bracing specification section along with a table listing the Ap and Rp values of the various duct types and sizes.

Current standards practiced and maintained within the professional community as well as specific seismic

design codes were thoroughly consulted and referenced in the guideline and details created. Specifically, The

International Building Code (2012) and ASCE 7-10 Chapter 13 with reference to SMACNA Seismic Restraint Manual

(third edition), and the Practical Guide to Seismic Restraint (second edition) by the American Society of Heating,

Refrigerating and Air-Conditioning Engineers (ASHRAE) were used.

It is our intention and hope that this guideline and the standard seismic bracing details will be used to

assist design professionals in creating seismic restraint specification sections for LDS temple projects. These will

meet the specific needs and expectations of the LDS church by providing effective mechanical system seismic

bracing of all temples, past and future.

DESIGN

In preparation for the design portion of this report, each team member familiarized themselves with the

necessary seismic design codes and standards namely, ASCE 7-10, SMACNA, and ASHRAE. Once the code was

understood, the team met with John Masek and Enoch Eskelson from International Seismic Application Technology

(ISAT). John Masek is the senior structural engineer at ISAT and Enoch is the operations manager. ISAT was not

only a tremendous technical resource, but also accompanied the team on a tour of the print and distribution

facility of the LDS church which is currently undergoing a seismic restraint upgrade. The team also met with Dave

Halverson from Halverson Mechanical, a mechanical contractor with extensive experience with HVAC demands of

LDS temples. Both ISAT and Halverson mechanical helped us gain an understanding of current practices,

shortcomings in the industry, and specific applications for LDS temples. The team also learned to use MathCad and

Revit to create the details and maximum spacing specifications.

With an understanding of the code, current practices, and the design requirements for LDS temples, the

team became equipped to make recommendations for the formulation of a seismic restraint specification and the

creation of some typical seismic restraint designs that can be included in the construction drawings.

SPECIFICATIONS

Specifications are an important way to ensure that a project in a seismic area is constructed as planned. A

list of recommended specifications was produced in this project to be included in a specification document for the

design and construction of a temple for the LDS church. These recommendations have been compiled from various

sources including: ASCE 7-10, IBC, and recommendations from professionals practicing within the industry. These

recommendations should be used in order to clarify the code and to ensure all parties involved understand

expectations. The specifications are currently not complete and may contain internal notes for future reference as

the document is completed. The full list of specifications may be viewed in Appendix A.

The specifications are arranged in five categories for ease in organizing and better understanding their

context. They are arranged into five categories: General/ Definitions, Submittals, Design of Forces, Bracing, and

Connections. This may not be the organization chosen when generating the actual specification document. These

categories cover clarifications of definitions and rules from ASCE 7-10, required submittals, and requirements

regarding the design of forces, braces and connections. Specifications that were specifically noted as important are

discussed below.

The General/Definitions section assigns liability requiring that a contractor abide by ASCE 7 and IBC. The

specification clarifies inspection requirements to ensure compliance. These requirements include inspections pre-

submittal, prior to cover up and at completion. It is also recommended that inspections be required at regular

intervals. This section also contains a list of acceptable seismic restraint manufacturers to ensure that the seismic

braces are certified.

Several rules or guidelines in the code have room for interpretation to accommodate various situations.

These need to be stated in the specifications so that the interpretation of the code meets the expectations of the

LDS church in their seismic bracing. As stated in ASCE 7-10 13.6.7, all ductwork designs to carry toxic, highly toxic

or flammable gases or used for smoke control must be braced. A specific definition of toxic was suggested as a

specification to ensure that all ducts posing as a health hazard if released are braced. A similar variation in

interpretation is seen in the 12 inch (in.) rule in ASCE 7-10 13.6.7.1b that states if the, "ductwork is supported by

hangers and each hanger in the duct run is 12 in. or less in length from the duct support point to the supporting

structure," it is exempt from being braced. The 12 inches can be interpreted differently, and while it isn't explicitly

stated, it must be less than 12 in. for the full run of duct otherwise the duct isn't being braced properly. Therefore,

we further defined the 12 in. rule in the specification to clarify what specifically classifies under this rule and that it

must be on the full run of duct.

The required submittals are detailed to ensure equivalent submissions. It is specified that the design must

be project specific and stamped by an engineer in the state of construction. This guarantees that the engineer is

licensed in the state of construction and qualified to sign off on the requirements of that state. Project specific

plans discourage general submissions lacking any calculations for the specific project. It is also recommended that

they require them to state the exact location of braces on the plans and indicate the types. In designing the forces,

it is specified that the brace capacity must be calculated to include the dead load as well as the seismic load. This

may seem to be an apparent requirement but it must be stated so as to ensure that the duct is not being under

braced. The Ap and Rp values for calculation of the forces on the duct are included in the specifications and can be

seen in Table 1.

Table 1: Assigned Ap and Rp values

Duct Type Ap Rp

Air-side HVAC, fans, air handlers, air conditioning units, cabinet heaters, air

distribution boxes, and other mechanical components constructed of sheet

metal framing

2.5 6.0

Wet-side HVAC, boilers, furnaces, atmospheric tanks and bins, chillers, water

heaters, heat exchangers, evaporators, air separators, manufacturing or process

equipment, and other mechanical components constructed of high-

deformability materials

1.0 2.5

Suspended vibration isolated equipment including in-line duct devices and

suspended internally isolated components

2.5 2.5

Ductwork, including in line components, constructed of high deformability

materials, with joints made by welding or brazing

2.5 9.0

Ductwork, including in-line components, constructed of high or limited

deformability materials with joints made by means other than welding or

brazing

2.5 6.0

Ductwork, including in-line components, constructed of low deformability

materials, such as cast iron, glass and non-ductile plastics

2.5 3.0

The bracing section of the specification discuses rules and exceptions for bracing the HVAC ducts. The

bracing exceptions can also be seen on plan sheet DT-04. This section states that if transverse bracing is used as

longitudinal bracing it must be designed for those loads (DT-01). Also, it requires a maximum of 45 degrees

measured from the horizontal for bracing and prohibits the use of cable and rigid braces on the same run. These

and other specifications provide specific guidelines on designing and constructing the seismic braces. They ensure

common submittals that are easily compared and that the code is being upheld during construction.

DETAILS

Standardized details are included to ensure all parties involved have a proper understanding of what is

expected and to ensure proper installation. This is not an exhaustive list and is to serve as a guideline. Each detail

will need to be modified to the specific needs of each individual project. The details were compiled using various

sources as reference such as ASHRAE, SMACNA, and the structural engineer at the LDS church over temple

projects, Brent Maxfield. A Revit file for each drawing was included with the final report to ensure that any

necessary project specific adjustments can be made. Figure 1 displays a longitudinal brace detail and Figure 2

contains a transverse brace detail for a rectangular and round duct.

Figure 1: Longitudinal Brace

Figure 2: Transverse Bracing of Round and Rectangular Ducts

Once an adequate level of proficiency in Revit was attained, the team spent time deciding what types of

details might best represent the needs for a temple project. The team consulted with seismic bracing professionals

familiar to the LDS church such as ISAT and Halverson Mechanical, as well as the details found in the SMACNA and

ASHRAE seismic design manuals. Once details were selected as potential options, we consulted with Brent

Maxfield and narrowed down the list of details. Our team then had a specific list of details that best represented

what a design professional might need to include in the drawings of a temple project. These drawing were then

created in Revit, in transverse and longitudinal views.

MINIMUM BRACING DESIGN

When designing seismic braces of ductwork, there are many different factors that must be considered to

ensure proper performance in the event of an earthquake or other natural disaster. It is necessary for the

structural engineer to determine the proper spacing of seismic braces to ensure the strength is adequate. The

governing limit state which determines the brace spacing must be determined from the following:

• Duct Brace Spacing Schedule

• Capacity of the structure to resist brace load

• Connection strength of the brace to the duct

• Brace capacity

• Capacity of duct to span between braces

The Duct Brace Spacing Schedule is a table which provides maximum transverse and longitudinal brace

spacing depending on the seismic acceleration input. This table provides maximum values that cannot be exceeded

even if the capacity of the other limit states allows it.

Once the maximum transverse and longitudinal brace spacing is calculated, the actual locations of the

braces on the ductwork must be determined. Often, ductwork bends and changes direction, leading to

complicated labyrinths of ductwork. When this occurs various rules must be followed to ensure proper seismic

bracing.

Due to the complexity of ductwork systems it is essential for these rules to be clear and include drawings. One of

the rules states, “If a straight run of ductwork has less than two support points, is connected to a braced straight

run of ductwork at each end, and its total length is less than two duct widths, brace across the run by adding its

length to the transverse and longitudinal brace design of the connected runs. If its length is greater than two duct

widths, a support point with a transverse brace is required.” This rule is not easily understood with one reading

and to ensure the interpretation is consistent, Figure 3 is provided. A complete list of rules and figures for the

determination of brace spacing can be found in Appendix B.

Figure 3: Drawing to Clarify Brace Spacing Rule

These rules were developed using ASCE 7-10, ASHRAE, and SMACNA. They were also reviewed by John Masek of

ISAT to ensure correctness.

CONCLUSION

The team met the sponsor’s needs by providing details for seismic bracing, a specification outline and

developing a system for determining brace spacing. This project has been performed in consultation with licensed

structural engineers, SMACNA and ASHRAE seismic design manuals and ASCE 7-10. These deliverables will assist

the LDS church in standardizing bids received so that a fair comparison can be made. They will also help to ensure

that design and installation of ductwork seismic bracing will be done properly according to the latest seismic

design standards.

The specifications and details provided are not meant to be a comprehensive list. It is suggested that

connection details would be added to the standard details. The specific seismic bracing requirements will need to

be developed according to the needs of each project. When used properly, these deliverables will effectively

communicate the expectations of the LDS church and ensure the proper seismic bracing of all current and future

temple projects.

APPENDIX A

STANDARD SPECIFICATIONS RECOMMENDATIONS

______________________________________________

General/Definitions

� Define Toxic (ex. Natural gas, flammable, poses health hazard if released).

� Furnished engineering and materials should meet the requirement of seismic design of supports

and attachments of systems.

� Materials shall be in conformance with national recognized standard ASCE 7-13.6.5.4.

� The seismic restraint of nonstructural components shall meet the requirements of ASCE 7. If the

component in question is exempted by Section 13.1.4 of ASCE 7, a submittal noting that seismic

restrain of the particular component is not required.

� The following seismic restraint manufacturers are accepted:

o Vibro-Acoustics

o International Seismic Application Technology(ISAT)

o Amber/Boothe

o Mason Industries Inc. (M.I.)

o Kinetics Noise Control Inc (K.N.C.)

o Vibration Mounting & Controls, Inc.

� Clarify special inspection requirements included in bid specs.

� Specify inspections are required in regular intervals (recommended: time of construction/5 or

every other week).

� Inspections must be performed at least pre-submittal, prior to cover up and at completion.

� Comply with applicable requirements as in ASCE 7 Table 13.2-1.

� Default Ip=1.25 unless otherwise specified or required.

Submittals

� Must submit calculations by a structural engineer specific to the project to be reviewed by

consulting structural engineer.

� Drawings and calculations that take into account relative displacements are required.

� Don’t require certification of components with Ip=1.5 if it does not contain hazardous

substances, as per ASCE 7-13.2.2.

� Drawings shall specify anchor bolt type, embedment, concrete compressive strength, minimum

spacing between anchors and minimum distances of anchors from concrete edges. All anchor

ICC certifications shall be submitted.

� Project-specific design prepared by a registered design professional in state where the project is

being constructed and manufacturer’s certification of component seismic qualifications that

meet the requirements are required.

� Each contractor responsible for the installation of Designated Seismic Systems must submit a

“Statement of Responsibility” as required by section 1706.1 of the IBC 2006, prior to beginning

work on the system or component.

� Submittal document must include a “Basis for Designing” or “Design Criteria” which includes a

statement from the registered design professional that the design complies with the

requirements of the ASCE 7-05, chapter 13 and IBC 2009 Chapter 1912/ACI 318(concrete

anchors).

� Submittals must include seismic bracing layout drawings indicating the location of all seismic

restraints. The submittal package must include seismic restraint details providing specific

information relating to the materials, type, size, and locations of anchorages; materials used for

bracing; attachment requirements of bracing to structure and component, and locations of

transverse and longitudinal sway bracing and rod stiffeners.

� Catalog cut sheets and installation instructions shall be included for each type of seismic

restraint used on equipment or components being restrained.

� Submittal drawings and calculations must be stamped by a registered professional engineer in

the state where the project is being constructed who is responsible for the seismic restraint

design. All seismic restraint submittals not complying with this certification will be rejected.

Design of Forces

� The component Ip values must be specified by item by the engineer.

� The system shall be designed such that it will not transmit isolated vibration to the structure

(isolators).

� Thermal Expansion, Isolation and Thrust Forces shall be considered in design.

� The various utilities will coordinate so as to ensure displacement won’t cause failure to other

components.

� Design must include seismic loads in conjunction with dead loads as required by the IBC/ASCE 7.

� Design must consider flexibility as well as strength, as per ASCE 7-13.2.4.

� The force Fp shall be applied independently in at least two orthogonal horizontal directions,

except where non-seismic loads on nonstructural components exceed Fp, such loads shall govern

the strength design.

Duct Type Ap Rp

Air-side HVAC, fans, air handlers, air condiConing units, cabinet

heaters, air distribuCon boxes, and other mechanical components

constructed of sheet metal framing 2.5 6.0

Wet-side HVAC, boilers, furnaces, atmospheric tanks and bins, chillers,

water heaters, heat exchangers, evaporators, air separators,

manufacturing or process equipment, and other mechanical

components constructed of high-deformability materials

1.0 2.5

Suspended vibraCon isolated equipment including in-line duct devices

and suspended internally isolated components 2.5 2.5

Ductwork, including in line components, constructed of high

deformability materials, with joints made by welding or brazing 2.5 9.0

Ductwork, including in-line components, constructed of high or limited

deformability materials with joints made by means other than welding

or brazing 2.5 6.0

Ductwork, including in-line components, constructed of low

deformability materials, such as cast iron, glass and non-ducCle

plasCcs

2.5 3.0

Bracings

� The 12 inch rule must be explicitly defined or not allowed. Recommended wording for explicitly

defining 12 inch rule:

o Seismic restraints are not required on HVAC ducts suspended from hangers that are 12

inches or less in length from the top of the duct to the supporting structure and the

hangers are detailed to avoid significant bending of the hangers and their connections.

Duct must be positively attached to hangers within 2” from the top of the duct. Hanger

rods shall not be constructed in a manner that would subject the rod to bending

moments (swivel, eye bolt, or vibration isolation hanger connection to structure are

required to prevent bending moments when utilizing this exclusion). Displacement of

the component shall not cause damaging impact with other utilities or the structure.

Flexible connections are required between unbraced systems and equipment to

accommodate differential displacements. Where HVAC systems Ip>1.25, this exclusion

shall not apply (per ASCE 13.6.7).

� If transverse braces are used to brace longitudinally, they shall be designed for both the

longitudinal and transverse forces.

� Rods must be stiffened such that the Euler buckling strength will not results in buckling.

Specifications may include a minimum length required to be braced for the project.

� All isolation materials, flexible connectors and seismic restraints shall be properly certified and

shall be from the same vendor.

� Inline items greater than 75 lbs. shall be braced separately.

� Cable restraints must always be straight and may not bend around obstructions.

� Braces shall be a maximum of 45° from the horizontal or 60° if braced twice as often.

� The bracing loads on the structure shall be coordinated with the structural engineer.

� When using vibration isolator’s cable bracing shall be used.

� Multi-tiered racks shall be stiffened.

� Attachment of brace to duct must provide a positive load path to structure. Seismic bracing

details shall clearly indicate positive load path.

� 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

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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.

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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)

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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

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L<= Max. Transverse Braces Spacing - Offset


Figure 4: Offset With Transverse Brace Required

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12. Cable bracing shall be in a straight line to the structure, it shall not touch other ductowrk, piping, or other buildingcomponents.

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Duct Brace SpacingMaximum SeismicAcceleration Sds

Input (g)

MaximumTransverse BraceSpacing, Lt (ft.)*

MaximumLongitudinal Brace

Spacing, Ll (ft.)

0.2 40' - 0" 80' - 0"0.4 30' - 0" 60' - 0"0.8 30' - 0" 60' - 0"1.6 30' - 0" 40' - 0"

Maximum Offset Lengths for Pipe

Max PipeDiameter (in)

0.25g,Seismic

Input

0.5g,Seismic

Input

1.0g,Seismic

Input

2.0g,Seismic

Input

0' - 1" 3' - 0" 1' - 0" 0' - 0" 0' - 0"0' - 2" 2' - 0" 1' - 0" 0' - 0" 0' - 0"0' - 3" 2' - 0" 1' - 0" 0' - 0" 0' - 0"0' - 4" 4' - 0" 2' - 0" 1' - 0" 1' - 0"0' - 6" 8' - 0" 4' - 0" 2' - 0" 2' - 0"0' - 8" 10' - 0" 8' - 0" 4' - 0" 4' - 0"0' - 10" 10' - 0" 10' - 0" 5' - 0" 5' - 0"1' - 0" 10' - 0" 10' - 0" 6' - 0" 6' - 0"1' - 2" 10' - 0" 10' - 0" 10' - 0" 10' - 0"

Pipe Brace SpacingMax PipeDiameter

(in)Max Transverse

Distance (ft)Max Longitudinal

Distance (ft)

0' - 5" 40' - 0" 80' - 0"0' - 8" 40' - 0" 40' - 0"1' - 4" 20' - 0" 20' - 0"

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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SPACING TABLES

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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.

General Notes

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INCLUDECONNECTIONDETAILSEE CONNECTIONDETAILS

VERTICALHANGER ORSTIFFENEDRODS.SEE STIFFENEDROD DETAIL.

45º MA

X

INCLUDE CONNECTION DETAILSEE CONNECTION DETAILS


45º MA

X





TRAPEZE

45º MA

X

CONCRETE ORMASONRY WALL





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RECTANGULAR DUCTS

DT-05

TRANSVERSE RECTANGULAR DUCT BRACING

INCLUDE CONNECTION DETAILSEE CONNECTION DETAILS

VERTICAL HANGEROR STIFFENED RODS.SEE STIFFENED ROD DETAIL.

45° MAX

VERTICAL HANGEROR STIFFENED RODS.SEE STIFFENED ROD DETAIL

INCLUDE CONNECTION DETAIL.SEE CONNECTION DETAILS

45º MAX

INCLUDE CONNECTION DETAILS.SEE CONNECTION DETAILS

VERTICAL HANGER ORROD STIFFNERS.SEE DETAIL STIFFENED ROD DETAIL.

CONCRETE OR MASONRY WALL


TRANSVERSE ROUND DUCT BRACING




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ROUND DUCTS

DT-06


RECTANGULAR DUCT ROUND DUCT

45º MA

X



45º MA

X



45º MA

X

LONGITUDINAL DUCT BRACING




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LONGITUDINAL BRACING

DT-07

Equipment

Four-Cable

Equipment

Equipment

Eight Cable

Solid Brace

STIFFENER CLIP SPACED PER MANUFACTURER (2 MIN)

ATTACHMENT CLAMP

STEEL ANGLE ORSTRUT CHANNEL

6" MAX

ROD STIFFENER

CABLE OR RIGID BRACE

6" MAX

45º MA

X




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EQUIPMENT BRACING

DT-08

seismic bracing of hvac systems for lds...

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