1 Scope
NOTE This standard covers the materials, selection, and installation of vibration isolation and seismic restraint for mechanical, electrical, and plumbing equipment and for the piping, ductwork, and conduit distribution systems that connect to it. (1.1)
NOTE Two linked but distinct subjects are addressed: vibration isolation, which keeps equipment-generated vibration out of the building structure, and seismic restraint, which keeps equipment and distribution systems in place during an earthquake. (1.2)
NOTE Vibration isolation and seismic restraint are addressed together because they share the same attachment point and frequently conflict: an isolator that decouples equipment from the structure for vibration control also removes the rigid path that would resist seismic load, so isolated equipment in a seismic region must use restrained isolators that provide both functions. (1.3)
NOTE The boundary of work under this standard is the isolation and restraint hardware and its attachment to both the equipment and the building structure; the supported equipment and the distribution systems themselves are governed by their respective standards. (1.4)
NOTE A vibration isolation or seismic restraint deficiency is rarely discovered at installation; it appears later as transmitted noise and vibration complaints in occupied spaces, as a failed special inspection, or as catastrophic displacement of equipment and ruptured piping during a seismic event. (1.5)
1.6 Seismic Coordination with the Structural Engineer of Record
1.6.1The seismic design forces, the attachment loads delivered to the structure, and the adequacy of the supporting structure to receive those loads shall be coordinated with the structural engineer of record (SEOR).
NOTE This standard governs the isolation and restraint of the nonstructural components; it does not govern the design of the building structure or its seismic-force-resisting system. (1.6.2)
1.6.3Attachment forces computed under ASCE/SEI 7 Chapter 13 shall be transmitted to the SEOR for confirmation that the structure can receive them at each attachment location.
1.7 Coordination with Other Standards
1.7.1Equipment selection, weights, and operating speeds shall be obtained from the equipment standards and schedules, including Hvac Fans and Hvac Pumps. 1.7.2Housekeeping pad dimensions, reinforcement, and embedded anchorage shall be coordinated with Concrete Pads. 1.7.3Pipe and duct gravity supports and the seismic bracing of piping and ductwork shall be coordinated with Hydronic Piping and Hvac Ductwork. 2 Referenced Standards
2.1Equipment, materials, and installation shall comply with the latest adopted edition of each standard below unless a specific edition is referenced by the contract documents or by the local building code.
2.2Where conflicts exist between referenced standards, the more stringent requirement shall govern unless the structural engineer of record directs otherwise in writing.
2.3 Referenced standards list
| Standard |
Title |
| ASCE/SEI 7 |
Minimum Design Loads and Associated Criteria for Buildings and Other Structures (Chapter 13, Seismic Design Requirements for Nonstructural Components) |
| IBC |
International Building Code (Chapter 16 structural design; Chapter 17 special inspections and tests) |
| ACI 318 |
Building Code Requirements for Structural Concrete (Chapter 17, Anchoring to Concrete) |
| ACI 355.2 |
Qualification of Post-Installed Mechanical Anchors in Concrete |
| ACI 355.4 |
Qualification of Post-Installed Adhesive Anchors in Concrete |
| ICC-ES AC156 |
Acceptance Criteria for Seismic Qualification by Shake-Table Testing of Nonstructural Components |
| ICC-ES AC193 |
Acceptance Criteria for Mechanical Anchors in Concrete Elements |
| ICC-ES AC308 |
Acceptance Criteria for Post-Installed Adhesive Anchors in Concrete Elements |
| SMACNA |
Seismic Restraint Manual: Guidelines for Mechanical Systems (4th Edition) |
| ASHRAE Handbook |
HVAC Applications, Chapter 49 (Noise and Vibration Control) |
| ANSI/ASHRAE 171 |
Method of Testing Seismic Restraint Devices for HVAC&R Equipment |
| MSS SP-58 |
Pipe Hangers and Supports — Materials, Design, Manufacture, Selection, Application, and Installation |
| ASTM A36 |
Standard Specification for Carbon Structural Steel |
| ASTM A123 |
Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products |
| ASTM A1011 |
Standard Specification for Steel, Sheet and Strip, Hot-Rolled, Carbon, Structural |
| ASTM D2240 |
Standard Test Method for Rubber Property — Durometer Hardness |
| NFPA 13 |
Standard for the Installation of Sprinkler Systems (sprinkler-pipe seismic bracing, where it governs) |
| MIL-spec / aircraft cable |
Galvanized aircraft cable for cable seismic bracing (per the restraint manufacturer's listing) |
3 Submittals
3.1 Action Submittals
3.1.1The Contractor shall submit the following for the Engineer's and structural engineer of record's review and return prior to procurement or fabrication of isolation and restraint components:
- Vibration isolation schedule listing, for each isolated equipment tag, the equipment operating weight and distribution, the lowest operating speed and disturbing frequency, the selected isolator type, the rated load, the rated and operating static deflection, and the resulting isolation efficiency
- Isolator product data for each isolator type, including load-versus-deflection data, spring free height and solid height, lateral-to-vertical stiffness ratio for spring isolators, and the durometer of elastomeric elements per ASTM D2240
- Base product data and structural calculations for inertia bases and structural-steel bases, including base weight, reinforcement, and isolator locations
- Flexible pipe connector and flexible conduit product data, including pressure and temperature rating, movement capability, and end connection type
- Thrust restraint product data for high-static fans, including spring rate and the calculated thrust force
- Seismic restraint schedule listing, for each restrained component and distribution run, the seismic design force, the restraint type, the brace spacing, and the attachment to the structure
- Seismic design force calculations per ASCE/SEI 7 Chapter 13 for each restrained component and distribution system, prepared and stamped by a licensed professional engineer, showing the parameters used (ap, Rp, Ip, the component weight, and the resulting Fp)
- Anchorage calculations for each attachment to concrete or structural steel, prepared and stamped by a licensed professional engineer, citing the anchor evaluation report and demonstrating adequacy for the seismic design force per ACI 318 Chapter 17
- Special seismic certification (ICC-ES AC156 shake-table test report or equivalent) for each active or designated seismic component required to function during or after the design earthquake
- Anchor evaluation reports (ICC-ES ESR or equivalent) for each post-installed anchor, confirming qualification for cracked concrete and seismic loading per ACI 355.2 or ACI 355.4
- Manufacturer's installation instructions for each isolation and restraint component
☑ Vibration isolation schedule (per equipment tag)
☐ Isolator product data with load-deflection curves
☐ Inertia and structural base data and calculations
☐ Flexible pipe connector and flexible conduit data
☐ Thrust restraint data for high-static fans
☐ Seismic restraint schedule (per component and run)
☐ ASCE 7 Chapter 13 seismic force calculations (PE-stamped)
☐ Anchorage calculations per ACI 318 Chapter 17 (PE-stamped)
☐ Special seismic certification (AC156) for active components
☐ Anchor evaluation reports (ICC-ES ESR) for post-installed anchors
☐ Manufacturer's installation instructions
3.1.2Fabrication, procurement, and installation shall not proceed until the associated action submittals have been reviewed and returned with no outstanding engineering questions.
3.2 Closeout Submittals
3.2.1At substantial completion the Contractor shall provide the following closeout submittals:
- Operation and maintenance data including isolator adjustment instructions, the recommended re-leveling and limit-stop reset procedure, and the seismic restraint inspection checklist
- As-installed isolation and restraint schedule reflecting any field-approved substitutions or relocations
- Special inspection reports prepared by the approved special inspector documenting verification of anchorage installation, post-installed anchor torque and embedment, and restraint configuration per IBC Chapter 17
- Field verification records confirming that isolated equipment is floating free on its isolators with all shipping restraints removed and that all restrained isolator limit stops are set to the operating clearance
- Manufacturer's special seismic certification labels and supporting test reports for active and designated seismic components
☑ Operation and maintenance data (adjustment and inspection)
☑ As-installed isolation and restraint schedule
☑ Special inspection reports per IBC Chapter 17
☑ Field verification of free-floating equipment and limit-stop settings
☑ Special seismic certification labels and test reports
4 Quality Assurance
4.1 Manufacturer Qualifications
4.1.1Isolation and seismic restraint components shall be the products of a manufacturer regularly engaged in the design and production of vibration isolation and seismic restraint hardware for commercial MEP service.
NOTE A single isolation and restraint manufacturer should furnish the isolators, bases, restraints, and snubbers for a given equipment item so that the load path is coordinated by one source. (4.1.2)
4.2 Design Responsibility
4.2.1Seismic design forces and restraint and anchorage details shall be designed by a professional engineer licensed in the project jurisdiction and retained by the Contractor or the restraint manufacturer.
4.2.2The seismic restraint design shall be reviewed and accepted by the structural engineer of record before installation.
NOTE Delegated design of seismic restraint by the restraint manufacturer's engineer is standard industry practice, but the structural engineer of record retains responsibility for the building structure that receives the restraint loads; the two scopes must be reconciled in writing. (4.2.3)
4.3 Special Seismic Certification
4.3.1Active and designated seismic components that are required by ASCE/SEI 7 Section 13.2.2 to function during or after the design earthquake shall be certified by shake-table testing in accordance with ICC-ES AC156, by approved analysis, or by experience data, as accepted by the building official.
NOTE The component importance factor Ip equals 1.5 for components designated to function for life-safety purposes after an earthquake, for components conveying or supporting hazardous materials, and for components in or attached to designated essential facilities; certification by shake-table testing is the prevailing method for such active equipment. (4.3.2)
NOTE In jurisdictions and on facility types governed by the California HCAI (formerly OSHPD) program, components may carry an OSHPD Special Seismic Certification Preapproval (OSP) or the manufacturer's anchorage details may carry an OSHPD Preapproval of Manufacturer (OPM); both are issued on the basis of AC156 shake-table testing. (4.3.3)
4.3.4 Special seismic certification datasheet
Not required — component is not active and not designated seismic (Ip = 1.0)
Shake-table tested per ICC-ES AC156
Certified by approved analysis
Certified by experience data
OSHPD/HCAI Special Seismic Certification Preapproval (OSP)
4.4 Special Inspection
4.4.1Where seismic restraint of nonstructural components is required, the installation shall be subject to special inspection by an approved special inspector in accordance with IBC Chapter 17.
4.4.2Special inspection shall include verification of post-installed anchor type, embedment, hole cleaning, and installation torque or adhesive cure, and verification that restraint and snubber configuration matches the accepted design.
NOTE Post-installed anchors are the most frequently mis-installed element of a seismic restraint system — wrong anchor type, insufficient embedment, an uncleaned hole for an adhesive anchor, or installation in a cracked or edge-distance-deficient location — and the special inspection is the control that catches these before they are concealed. (4.4.3)
5 Seismic Design Basis
5.1 Seismic Design Category and Exemptions
5.1.1The seismic design category (SDC), the design spectral response accelerations, and the applicable exemptions shall be established from the structural drawings and the governing building code for the project.
NOTE ASCE/SEI 7 Chapter 13 exempts certain nonstructural components from seismic restraint, including, subject to the conditions stated in the standard, components in Seismic Design Category A and B, many mechanical and electrical components in SDC C, distribution systems and components supported by hangers within the length limit of the standard, and small or light components below the weight and height thresholds of the standard. (5.1.2)
NOTE An exemption shall be applied only after confirming that every condition the standard attaches to that exemption is met, including the flexible-connection condition for distribution systems and the positive-attachment condition for components whose anchorage is detailed on the drawings. (5.1.3)
5.1.4 Seismic design category datasheet
Per drawings — structural general notes
5.1.5 Component importance factor datasheet
● 1.0 — standard component (no post-earthquake function required)
○ 1.5 — designated/active component (life-safety function, hazardous contents, or essential facility)
Per drawings — structural general notes
5.2 Seismic Design Force
5.2.1The horizontal seismic design force Fp on each component, its supports, and its attachments shall be computed in accordance with ASCE/SEI 7 Chapter 13 using the component amplification factor, the component response modification factor, the component importance factor Ip, and the component operating weight.
5.2.2The vertical seismic force component shall be added to the load on supports and anchorage as required by ASCE/SEI 7 Chapter 13.
NOTE Where the weight of a component equals or exceeds 20 percent of the combined effective seismic weight of the component and its supporting structure, the component shall be designed as a nonbuilding structure rather than under the simplified nonstructural-component provisions. (5.2.3)
NOTE The ASCE 7-22 nonstructural force equation revised the prior approach to account for the dynamic response of the supporting structure and the ductility of the component anchorage; the calculation shall use the equation of the code edition adopted by the project jurisdiction, not a remembered formula from a superseded edition. (5.2.4)
6 Vibration Isolation Selection
6.1 Selection Basis
6.1.1Each isolated equipment item shall be provided with isolators selected for the required static deflection at the equipment operating weight so that the isolator natural frequency is far enough below the equipment disturbing frequency to achieve the required isolation efficiency.
NOTE Isolator selection follows from one governing ratio: the equipment disturbing frequency divided by the isolator natural frequency. A larger ratio gives more isolation. Because the isolator natural frequency falls as static deflection rises, the selection reduces to choosing an isolator whose operating static deflection is large enough for the required isolation. (6.1.2)
NOTE Effective isolation begins only where the disturbing frequency exceeds the isolator natural frequency by a factor of at least the square root of two; below that ratio the isolator amplifies rather than isolates. Practical design targets a frequency ratio of three or more, corresponding to roughly 90 percent isolation, and five or more for the 95 percent and greater isolation expected over noise-sensitive spaces. (6.1.3)
NOTE Selecting an isolator by load rating alone, without confirming the operating static deflection against the equipment's lowest disturbing frequency, is the most common vibration isolation error and produces equipment that is mounted on springs yet still transmits objectionable vibration to the structure. (6.1.4)
6.2 Disturbing Frequency
6.2.1The lowest disturbing frequency shall be taken as the equipment's lowest normal operating rotational speed, including the minimum speed of any variable-speed equipment, because isolation efficiency is governed by the lowest, not the nominal, operating frequency.
NOTE Variable-speed equipment shall be isolated for its minimum operating speed; an isolator selected for full-speed operation provides far less isolation at reduced speed, where the disturbing frequency approaches the isolator natural frequency. (6.2.2)
6.2.3 Lowest operating speed datasheet
2003600
2003004006009001160175035003600
Default: 1160 RPM
Per drawings — equipment schedule
6.3 Required Static Deflection
6.3.1The required operating static deflection shall be selected for the equipment type, the equipment lowest operating speed, and the location of the equipment in the building, following the selection guidance of the ASHRAE Handbook — HVAC Applications, Chapter 49.
NOTE Equipment on a stiff slab on grade requires less static deflection than the same equipment on an upper floor, because a flexible long-span floor has its own low natural frequency and requires a softer isolator to remain well below it; a slab-on-grade selection installed on an upper floor is a frequent cause of transmitted vibration. (6.3.2)
NOTE Lower-speed equipment requires greater static deflection than higher-speed equipment for the same isolation efficiency, because the lower disturbing frequency demands a correspondingly lower isolator natural frequency. (6.3.3)
6.3.4 Required static deflection datasheet
0.054
0.050.10.250.50.7511.522.533.54
Default: 1 in.
6.3.5 Equipment location datasheet
Slab on grade (stiff)
Upper floor, short span (under ~20 ft)
Upper floor, medium span (~20 to 30 ft)
Upper floor, long span (over ~30 ft, flexible)
Roof structure
Per drawings — structural floor framing plans
7 Isolator Types
7.1 Isolator Type Selection
7.1.1The isolator type shall be selected to provide the required static deflection at the equipment operating weight, with a restrained (seismic) type used wherever the equipment also requires seismic restraint.
NOTE Elastomeric (neoprene) mounts and pads provide small static deflection and are the economical selection for higher-speed equipment with low isolation requirements; steel spring isolators provide the larger static deflection required for low-speed equipment and noise-sensitive locations; and air springs provide very large effective deflection where the lowest natural frequency is required. (7.1.2)
7.1.3 Isolator type datasheet
Ribbed or waffle neoprene pad (small deflection, vibration pads under non-critical equipment)
Rubber-in-shear / molded neoprene mount (deflection up to ~0.5 in.)
Open (free-standing) steel spring isolator
Restrained (seismic) steel spring isolator with integral limit stops
Spring isolator with neoprene acoustic base pad (spring plus pad)
Air spring (pneumatic isolator, very low natural frequency)
7.2 Spring Isolator Construction
7.2.1Steel spring isolators shall have springs selected so that the lateral stiffness is at least equal to the rated vertical stiffness and so that the spring provides additional travel to solid of at least 50 percent of the rated operating deflection.
NOTE A laterally stable spring (lateral-to-vertical stiffness ratio of at least one) and adequate travel to solid prevent the spring from short-circuiting against its own coils or rocking under load, either of which destroys isolation. (7.2.2)
7.2.3Open spring isolators shall include a non-skid, sound-isolating neoprene acoustic pad bonded to the base plate to interrupt high-frequency vibration transmission through the spring steel.
7.2.4Spring isolators shall include a leveling bolt and means to adjust the equipment to level and to the operating height.
7.3 Restrained Spring Isolators
7.3.1Equipment that requires both vibration isolation and seismic restraint shall be mounted on restrained spring isolators that provide the operating static deflection during normal service and limit motion in all directions during a seismic event.
7.3.2Restrained spring isolators shall include integral limit stops with a resilient (elastomeric) snubbing element so that seismic motion is arrested without metal-to-metal impact.
NOTE The limit stops shall be set to clear the operating motion of the equipment so that the isolator floats free during normal operation and engages only on seismic or startup excursion. (7.3.3)
NOTE Bolting isolated equipment rigidly to the structure to provide seismic restraint defeats the isolation entirely — the bolt becomes a rigid vibration path; restrained isolators exist precisely so that restraint and isolation coexist, and a rigid restraint shall never be substituted for a restrained isolator on isolated equipment. (7.3.4)
7.4 Vibration Hangers
7.4.1Suspended equipment, piping, and ductwork requiring isolation shall be hung on vibration hangers selected for the required static deflection.
7.4.2Spring hangers shall be used where the required static deflection exceeds that available from an elastomeric hanger; combination spring-and-neoprene hangers shall be used where both low-frequency isolation and high-frequency (structure-borne noise) interruption are required.
NOTE The hanger box shall be designed so that the hanger rod does not contact the box at any point in the operating range; rod contact short-circuits the isolation and is a common installation defect. (7.4.3)
7.4.4 Vibration hanger datasheet
Neoprene-in-shear hanger (small deflection)
Steel spring hanger
Combination spring and neoprene hanger
Not applicable — floor-mounted equipment
8 Equipment Bases
8.1 Base Type Selection
8.1.1Each isolated floor-mounted equipment item shall be provided with the base type required to distribute the isolator loads, to maintain alignment of the equipment, and to provide the mass needed for stable low-frequency isolation.
NOTE A rail or structural-steel base spreads isolator loads and keeps a long or flexible equipment frame aligned; an inertia base adds mass that lowers the assembly's center of gravity, reduces motion at startup and shutoff, and is used for close-coupled pumps and high-thrust equipment where the added mass stabilizes the isolated system. (8.1.2)
8.1.3 Base type datasheet
Isolators mounted directly to equipment feet (no base)
Structural-steel rail base
Structural-steel perimeter base
Concrete-filled inertia base (steel frame, reinforced concrete fill)
Curb-mounted isolation (roof-mounted equipment)
8.2 Inertia Bases
8.2.1Inertia bases shall be a welded structural-steel perimeter frame with reinforcing steel and concrete fill, with isolator brackets located outside the frame so that isolators can be serviced without lifting the base.
8.2.2Inertia base mass shall be selected per the equipment manufacturer's and isolation manufacturer's recommendation, commonly 1 to 1.5 times the supported equipment weight for pumps and similar equipment, to provide stable isolation and limit dynamic motion.
NOTE Close-coupled pumps shall be mounted on an inertia base because the short coupling makes the assembly sensitive to motion; the inertia base mass restrains the reaction to flow-induced and starting torques. (8.2.3)
8.3 Curb-Mounted Equipment
8.3.1Roof-mounted equipment requiring isolation shall be mounted on an isolation curb that provides the required static deflection while maintaining a weathertight, wind-resistant, and seismically restrained connection to the roof structure.
NOTE Isolation curbs shall integrate the spring isolation, the seismic restraint, and the weatherproofing in a single assembly so that the roof penetration is not compromised by separate field-installed isolators. (8.3.2)
9 Flexible Connections and Thrust Restraints
9.1 Flexible Pipe Connectors
9.1.1Each isolated equipment item with a piping connection shall be connected to its piping through a flexible pipe connector at the equipment so that the piping does not short-circuit the isolation and so that the connector accommodates the isolated equipment's motion.
9.1.2Flexible pipe connectors shall be rated for the system operating pressure and temperature and shall be installed at the published face-to-face length without compression or extension.
NOTE A control rod or thrust restraint shall be provided across flexible connectors where the unrestrained pressure thrust would over-extend the connector or impose thrust on the equipment nozzle. (9.1.3)
NOTE Piping shall be independently supported and, where required, isolated for the first several hangers away from isolated equipment so that the piping does not transmit equipment vibration through the building or load the equipment nozzle; refer to
Hydronic Piping for the isolated-pipe-support detail.
(9.1.4) 9.1.5 Flexible pipe connector datasheet
Spherical (twin-sphere) elastomeric connector
Single-arch elastomeric connector
Braided stainless steel flexible hose with control rods
Not applicable — no piping connection
9.2 Flexible Conduit and Duct Connections
9.2.1Electrical connections to isolated equipment shall be made with a length of flexible conduit looped to accommodate the equipment's isolated motion without transmitting vibration into the raceway system; refer to Raceways And Conduit. 9.2.2Ducted connections to isolated air-handling equipment shall include a flexible duct connector at the equipment so that fan vibration is not transmitted into the ductwork; refer to Hvac Ductwork. 9.3 Thrust Restraints
9.3.1Fans developing high static pressure shall be provided with thrust restraints arranged to limit the fan's startup and operating movement caused by the air thrust reaction without short-circuiting the vibration isolation.
9.3.2Thrust restraints shall be horizontal spring assemblies installed on each side of the fan parallel to the airflow thrust, preloaded and adjusted to limit movement to the manufacturer's allowable value.
NOTE A high-static fan on soft isolators will lurch when started and may pull its flexible duct connector apart or surge against the ductwork; the thrust restraint absorbs the thrust reaction while preserving the isolation. (9.3.3)
9.3.4 Thrust restraint datasheet
○ Required — fan static pressure high enough to cause objectionable startup movement
● Not required — low-static fan or thrust within isolator allowable movement
10 Seismic Restraint of Equipment
10.1 Restraint of Isolated Equipment
10.1.1Vibration-isolated equipment requiring seismic restraint shall be restrained by restrained (seismic) spring isolators or by seismic snubbers arranged around the equipment, not by a rigid attachment.
10.1.2Seismic snubbers, where used in place of restrained isolators, shall be installed with an air gap and a resilient snubbing element set to clear the equipment's operating motion and to engage only on seismic excursion.
10.1.3 Restraint type for isolated equipment datasheet
Restrained spring isolators with integral limit stops
Open spring isolators with separate all-directional seismic snubbers
Restrained elastomeric mounts
Not required — equipment exempt from seismic restraint
10.2 Restraint of Non-Isolated Equipment
10.2.1Equipment that does not require vibration isolation but does require seismic restraint shall be anchored directly to the structure or to its housekeeping pad through anchorage designed for the seismic design force.
10.2.2 Direct-anchored equipment datasheet
Cast-in anchor bolts in housekeeping pad or slab
Post-installed expansion anchors (mechanical)
Post-installed adhesive anchors
Welded or bolted to structural steel
10.3 Anchorage to Concrete
10.3.1Anchorage of equipment, bases, isolators, and snubbers to concrete shall be designed in accordance with ACI 318 Chapter 17 for the seismic design force, including the reduction factors and ductility provisions the code requires for seismic anchorage.
NOTE Cast-in anchors shall be used in new housekeeping pads and slabs where the anchor locations are known at the time of the concrete pour, because cast-in anchors develop full capacity without the edge-distance and cracked-concrete penalties of post-installed anchors. (10.3.2)
10.3.3Post-installed anchors shall be qualified for cracked concrete and for seismic loading by an evaluation report (ICC-ES ESR or equivalent) per ACI 355.2 (mechanical) or ACI 355.4 (adhesive), and shall be installed at the embedment, spacing, and edge distance the evaluation report requires.
10.3.4Adhesive anchors installed in a horizontal or upwardly inclined orientation to resist sustained tension shall be installed by personnel certified for adhesive anchor installation and shall be subject to continuous special inspection, as ACI 318 requires.
10.3.6Housekeeping pad dimensions and embedded anchorage shall be coordinated with Concrete Pads. 10.3.7 Anchor type datasheet
Cast-in headed anchor or anchor bolt
Post-installed expansion anchor (mechanical, seismic-qualified)
Post-installed undercut anchor (seismic-qualified)
Post-installed adhesive anchor (seismic-qualified)
11 Seismic Restraint of Distribution Systems
11.1 Distribution Restraint Basis
11.1.1Piping, ductwork, conduit, and cable tray requiring seismic restraint shall be braced transversely and longitudinally in accordance with ASCE/SEI 7 Chapter 13 and the SMACNA Seismic Restraint Manual, except where a referenced system standard (such as NFPA 13 for sprinkler piping) governs.
NOTE A transverse brace resists motion perpendicular to the run and a longitudinal brace resists motion along the run; a length of pipe or duct needs both, because the two act on independent directions of seismic motion. (11.1.2)
NOTE Distribution systems suspended by hangers are exempt from seismic bracing only where every condition of the applicable ASCE/SEI 7 exemption is met, including the hanger length limit and the flexible-connection provision; the exemption shall be confirmed run by run, not assumed for the project. (11.1.3)
11.2 Brace Spacing
11.2.1Transverse and longitudinal brace spacing shall not exceed the maximum spacing established by the SMACNA Seismic Restraint Manual selection tables for the system, size, and seismic load, and shall not exceed the spacing shown on the accepted restraint submittal.
NOTE As a starting point before the SMACNA tables are applied, transverse braces are commonly spaced at intervals up to 40 ft and longitudinal braces up to 80 ft, with closer spacing required for larger or heavier runs and higher seismic loads. (11.2.2)
NOTE A longitudinal brace shall engage the run through a clamp or attachment that cannot slip along the pipe or duct, so that the brace actually develops the longitudinal restraint it is credited for. (11.2.3)
11.2.4 Transverse brace spacing datasheet
1040
10152025303540
Default: 40 ft
11.2.5 Longitudinal brace spacing datasheet
2080
20304050607080
Default: 80 ft
11.3 Brace Type
11.3.1Distribution systems shall be braced with cable (aircraft cable) bracing, with rigid strut bracing, or with a combination, as required by the system and as shown on the accepted restraint submittal.
NOTE Cable bracing resists tension only and is installed in opposing pairs so that each direction of motion is taken by a cable in tension; rigid strut bracing resists both tension and compression and so can restrain a direction with a single member, and is preferred where overhead space or geometry will not accommodate the splay of cable braces. (11.3.2)
NOTE Cable braces shall be installed at the splay angle within the range its listing permits, because both an excessively shallow and an excessively steep brace angle reduce the brace's effectiveness. (11.3.3)
11.3.4 Brace type datasheet
Cable (aircraft cable) bracing — tension only, opposing pairs
Rigid strut bracing — tension and compression
Combination cable and rigid bracing
11.4 Flexibility at Joints and Connections
11.4.1Flexibility shall be provided in piping, ductwork, and conduit where a run crosses a seismic separation joint or a building expansion joint, and at the connection between a braced run and an isolated or independently supported component, so that differential movement does not rupture the run.
NOTE Restraint and flexibility are complementary, not contradictory: the braces hold the run to one structural element, and the flexible element absorbs the relative movement where that run meets a differently moving element, such as across a seismic joint or at a flexibly mounted piece of equipment. (11.4.2)
12 Installation
12.1 Equipment Location and Arrangement
12.2 Setting Isolated Equipment
12.2.1Isolated equipment shall be installed so that, after all shipping restraints and blocking are removed, the equipment floats free on its isolators and bears no load through any rigid path to the structure.
NOTE All shipping bolts, blocking, and transit restraints shall be removed after the equipment is set and before startup; equipment left blocked transmits full vibration to the structure exactly as if it had no isolators. (12.2.2)
12.2.3Spring isolators shall be adjusted so that the equipment is level and at the operating height and so that each spring carries its design share of the load with the rated operating deflection.
NOTE Where a piping or duct connection imposes a load that shifts the equipment off level, the connection shall be corrected rather than compensated for by uneven isolator adjustment. (12.2.4)
12.3 Setting Restrained Isolators and Snubbers
12.3.1Restrained isolator limit stops and snubber air gaps shall be set to the clearance shown on the accepted submittal so that the restraint clears the operating motion and engages only on seismic excursion.
NOTE After the equipment is floating free, the limit-stop clearance shall be verified on every restrained isolator; a limit stop left bottomed against the equipment short-circuits the isolation in the same way a shipping bolt does. (12.3.2)
12.4 Installing Distribution Bracing
12.4.1Transverse and longitudinal braces shall be installed at the spacing and the attachment details shown on the accepted restraint submittal and shall attach to building structure, not to other nonstructural systems or to suspended ceilings.
NOTE A seismic brace shall not be attached to another distribution system, to the suspended ceiling grid, or to any element that is not part of the building structure, because the brace can only restrain the run if its far end is anchored to something that does not move with it. (12.4.2)
12.4.3Bracing attachments to the structure shall use the connector type qualified for the structure type (concrete insert, beam clamp, or welded attachment) and the seismic load.
12.5 Installing Anchors
12.5.1Post-installed anchors shall be installed at the embedment, hole diameter, spacing, and edge distance the anchor's evaluation report requires, with the hole drilled and cleaned by the method the report specifies.
NOTE Adhesive anchor holes shall be cleaned exactly as the manufacturer's published instructions require, because adhesive anchor capacity depends entirely on the bond to clean concrete and an uncleaned hole can lose most of its rated capacity. (12.5.2)
NOTE Anchors shall not be installed in cracked or spalled concrete or closer to an edge than the evaluation report permits; where field conditions prevent compliant installation, the condition shall be referred to the engineer before the anchor is set. (12.5.3)
13 Field Verification
13.1 Isolation Verification
13.1.1After installation and removal of all shipping restraints, the Contractor shall verify that each isolated equipment item is floating free, is level, and is at its operating height, and that no rigid path bypasses the isolators.
13.1.2The Contractor shall verify that piping, conduit, and duct connections to isolated equipment are made through their flexible connectors and do not load or short-circuit the isolation.
13.2 Restraint Verification
13.2.1The Contractor shall verify that restrained isolator limit stops and snubber gaps are set to the specified operating clearance on every restrained isolator and snubber.
13.2.2The Contractor shall verify that distribution braces are installed at the specified spacing, at compliant angles, and attached to building structure, and shall make the installation available for the special inspector's verification per IBC Chapter 17.
14 Delivery, Storage, and Handling
14.1Isolation and restraint components shall be delivered in original packaging, labeled with the equipment tag or run they serve, and stored indoors in a clean, dry location.
14.2Spring isolators and restrained isolators shall be protected from distortion and corrosion in storage and shall not be used to support construction loads before the equipment is set.
14.3Adhesive anchor cartridges shall be stored within the temperature range and shall not be used after the shelf-life date the manufacturer marks on the cartridge, because expired or temperature-abused adhesive does not develop rated bond strength.
15 Warranty
15.1The isolation and restraint manufacturer shall warrant the isolators, bases, restraints, snubbers, and connectors against defects in materials and workmanship for the period specified below, beginning from the date of substantial completion.
15.2 Warranty period datasheet
1 year from substantial completion (minimum)
2 years from substantial completion
5 years from substantial completion (extended)
15.3The Contractor shall warrant the installation workmanship — including isolator setting and adjustment, limit-stop and snubber clearances, brace installation, flexible connections, and anchorage — for one year from the date of substantial completion.
16 Spare Parts
NOTE The following spare parts datasheet establishes the spares to be delivered at substantial completion. (16.1)
☐ Spare restrained spring isolators — one per isolator size and rating used
☐ Spare seismic snubber elastomeric elements — one set per snubber size
☑ Spare flexible pipe connectors — one per connector size
☐ Spare vibration hanger elements — one per hanger type
☐ Adhesive anchor installation tools and cleaning brushes for the anchors used
16.2Spare parts shall be delivered to the Owner in original packaging, each tagged with the corresponding equipment tag, component model, and date of delivery.