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ASHRAE

American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.H

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The following details can be used to help prevent the effects of earthquakes on:• Mechanical Systems • Piping • Ductwork • Suspended Equipment • Floor Mounted Equipment

• Electrical Systems • Cable Trays, Bus Ducts • Conduit

PROTECTIONEARTHQUAKE

• Plumbing Systems • Piping• Fire Protection Systems • Piping

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ASHRAE

Suspended systems such as piping, equipment and ductwork need seis-mic braces to keep them from swaying during an earthquake. Seismic braces can be flexible using aircraft quality cables, or rigid (solid) using steel sections such as pipe, angles, or strut channels. Braces are typi-cally installed 30-40 ft (10-13 m) apart, at system turns and at the end of runs. Braces are attached to the pipe/duct at horizontal supports such as clevis’s or trapezes. The other end is attached to structure such as over-head concrete slabs or structural steel. Suspended equipment requires a minimum of four braces, one at each corner. Floor mounted equipment needs to be anchored to the structural slab. This also includes equipment that is Vibration Isolated with seismic snubbers.

Pipe, Cable Trays, Bus Ducts & ConduitBracing Details

Cable Bracing

TRANSVERSE & LONGITUDINAL CABLE BRACE FOR HORIZONTAL SUSPENDED PIPEFIGURE 1

TRANSVERSE BRACE LONGITUDINAL BRACE

ROD STIFFENER(WHEN REQUIRED)

STIFFENER CLAMP

HANGER RODSWIVELFASTENER

(TYP.)

FORCESEISMIC

SWAY BRACE

CLEVISSTIFFENER

ROD STIFFENER(WHEN REQUIRED)

STIFFENER CLAMP

HANGER ROD

NO LOADON CABLE

SEISMICTENSION

LOAD(REACTION)

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ASHRAE

Rigid or Solid Bracing

CABLE BRACE FOR TRAPEZE SUSPENDED PIPEFIGURE 2

CABLE BRACE

SEISMICFORCE

SWIVELFASTENER

(TYP.)

HANGER ROD

STIFFENER CLAMP

ROD STIFFENER(WHEN REQUIRED)

PIPE SECUREDTO TRAPEZE

SOLID BRACE IN COMPRESSIONFOR INDIVIDUALLY SUPPORTED PIPE

SOLID BRACE

SWIVELFASTENER

(TYP.)

CLEVIS STIFFENER

FIGURE 3

FORCESEISMIC

STIFFENERCLAMP

ROD STIFFENER(WHEN REQUIRED)

HANGER ROD

SOLID BRACE IN COMPRESSIONFOR TRAPEZE PIPE

FIGURE 4

SWIVELFASTENER

(TYP.)

PIPE SECUREDTO TRAPEZE

FORCESEISMIC

STIFFENER CLAMP

HANGER ROD

ROD STIFFENER(WHEN REQUIRED)SOLID BRACE

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Duct Bracing DetailsCable Bracing

CABLE BRACING OF SUSPENDED DUCTWORK

TRANSVERSE BRACE LONGITUDINAL BRACE

FIGURE 5

CABLEBRACE

SWIVELFASTENER(TYP.)

HANGERROD

STIFFENERCLAMP

ROD STIFFENER(WHEN REQUIRED)

DUCTWORK SECUREDTO TRAPEZE WITH SCREWS

Rigid or Solid Bracing

STIFFENERCLAMP

HANGER ROD

SOLID BRACE OF DUCTWORK ON TRAPEZE

L

ROD STIFFENER(WHEN REQUIRED)

SOLIDBRACE

FIGURE 6

FPV

PHF C.G.W

FPV

SWIVELFASTENER

TRAPEZE SUPPORT

SHEET METALSCREW

ADDITIONAL UPPER SUPPORT

H

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Suspended Equipment Bracing

STIFFENER CLAMP

ROD STIFFENER(WHEN REQUIRED)

TYPICAL SOLID BRACE ARRANGEMENT

SWIVELFASTENERS

(TYP.)

SOLID BRACEO = 30° TO 60°

FIGURE 8

ELEVATION

EQUIPMENT

HANGER RODSOLID BRACE(4)-TYPICAL

PLAN VIEW

HANGER ROD

EQUIPMENT

SOLIDBRACE

STIFFENERCLAMP

TYPICAL CABLE BRACE ARRANGEMENT

ELEVATION

O = 30° TO 60°

EQUIPMENT

ROD STIFFENER(WHEN REQUIRED)

HANGERROD

PLAN VIEW

FIGURE 7

CABLE BRACE(4)-TYPICAL

SWIVELFASTENER(TYP.)

CABLEBRACE

EQUIPMENT

HANGERROD

Suspended equipment requires bracing as shown in Figure 8 using rigid steel sections or Figure 7 using cables. Connections to the equipment such as piping, conduit or ductwork should be made with flexible connections.

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ASHRAE

Floor Supported EquipmentFloor mounted equipment may be bolted down if no vibration isolation is required. If the equipment is isolated then the equipment must either have bumpers as shown in Figure 9 or snubbers as shown in Figure 10.

ANCHOR BRACKET

NO CLEARANCE

STRUCTURAL ANCHOR

ANCHOR BRACKET CONNECTED TO EQUIPMENT

1/4" NEOPRENE

FIGURE 9

DETAIL A-A

EQUIPMENT

ANCHOR BRACKET(2) PER SIDE

PLAN VIEW

EQUIPMENT

TWO BOLTSPER BRACKET

A A

SUPPLEMENTAL BASE - OPEN SPRINGS AND SNUBBERS

SEISMIC SNUBBERSLOCATED AT OR NEARCROSS BRACING

ISOLATOR(TYPICAL)

VIBRATION

FIGURE 10

CONCRETE INERTIA BASESTEEL FRAME OR

SEISMIC SNUBBER(TYPICAL)

(SHOULD BE CONNECTED

CONCRETE INERTIA BASE) TO STEEL FRAME OR

HEIGHT SAVING BRACKET(TYPICAL)

EQUIPMENT

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Anchor BoltsAnchor bolts are one of the most impor-tant parts of a correctly designed and installed Seismic Restraint System. The most widely used anchors for seismic restaints are the wedge, adhesive and undercut.

Proper installation of anchors isimportant.

Basic installation methods for shelland adhesive anchors is shown inFigure 12.

FIGURE 11

FIGURE 12

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Sites with additional information:

• ASHRAE, American Society of Heating Refrigerating and Air Conditioning Engineers, www.ASHRAE.org

• ASHRAE Technical Committee TC 2.7 Seismic & Wind Restraint Design, www.ASHRAE.org/technology/page/1727

• FEMA, www.FEMA.gov , Publications 412, 413 & 414

• USGS, United States Geological Survey, www.USGS.gov

• SMACNA, Sheet Metal and Air Conditioning Contractors National Association, www.SMACNA.org

• VISCMA, Vibration Isolation and Seismic Control Manufacturers Association, www.VISCMA.com

• ICC, International Code Council, www.ICCSAFE.org

• National Fire Protection Association, www.NFPA.org

• AHRI, Air Conditioning, Heating and Refrigeration Institute, www.ahrinet.org

This publication was written by ASHRAE’s Technical Committee TC 2.7, Seismic and Wind Restraint Design. All details in this document are from ASHRAE’s Publication,” A Practical Guide to Seismic Restraint”, 2000, or FEMA Document 412