Seismic Suspend Ceiling-1

8/20/2019 Seismic Suspend Ceiling-1

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CPA T-Bar Guidelines Page 1 of 15

Revision Date: 10/2012

General Requirements/Checklist for:

Commercial

SUSPENDED CEILING

SYSTEMS INSPECTION

City of Palo Alto (CPA)

Building Inspection Division Inspection Request Line: 650 329-2496

Building Division Inspection Code IVR# 304

Codes/Standards Enforced:

2010 CBC, ASCE 7-50, ASTM C

635, 636, CISCA 3-4

Palo Alto Municipal Code (PAMC)The information provided in this document is general and intended as a guide only. Each project is unique and

additional requirements may be enforced as deemed appropriate.

REQUIRED ITEMS All existing tenant improvement suspended ceiling systems installed prior to January 1,

2008 in areas affected by renovation, structural repair, or alterations must be upgraded tomeet seismic requirements set forth in CISCA 3-4/UBC Standard 47-18. (See CISCA Guidelinesfor Seismic Upgrade requirements following checklist)

PLANS/SHOP DRAWINGS/ICC ES REPORT Contractor shall provide City of Palo Alto Inspector with engineered “heavy duty” suspended

ceiling system plans/shop drawings/manufacturer’s installation requirements at time of

inspection. Plan must include engineering specifications for compression struts, wall attachments, and

layout for seismic joints when areas in excess of 2500 square feet. Provide inspector with current ICC ES Report for suspended ceiling system.

SPECIAL INSPECTION City of Palo Alto adopted policy #15 on 07/09/2009 of ICC Tri-Chapter Uniform Code

Committee - Special Inspection is not required for suspended ceiling.

MINIMUM CODE REQUIREMENTS Suspended Ceilings (2010 CBC 2506.2.1/ASCE 7-05 13.5.6)

o

Seismic Design Categories D requirements for Suspended Ceiling Systems shall be

designed and installed in accordance with ASTM C635, ASTM C636, and the CISCA forSeismic Zones 3-4 as modified by the following:

A heavy duty T-bar grid system shall be used.

The width of the perimeter supporting closure angle shall be not less than 2 inches. Approved perimeter seismic clips may be used in lieu of 2 inch wall angle and shall beinstalled per manufacturer’s instruction and ICC-ESR reports information.

In each orthogonal (orthogonal means "involving right angles") horizontal direction, oneend of the ceiling grid shall be attached to the closure angle.

The other end in each horizontal direction shall have a 0.75 inches clearance from thewall and shall rest upon and be free to slide on a closure angle.

o

For ceiling areas exceeding 1,000 ft2, horizontal restraint of the ceiling to the structuralsystem shall be provided.

The tributary areas of the horizontal restraints shall be approximately equal.(Manufacturer may required vertical post every 12 square feet)EXCEPTION: Rigid braces are permitted to be used instead of diagonal splay wires. Braces and attachments to the structural system above shall be adequate to limit

relative lateral deflections at point of attachment of ceiling grid to less than 0.25inch for the loads prescribed in Section 13.3.1.


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MINIMUM CODE REQUIREMENTS (continued)

o

For ceiling areas exceeding 2,500 ft2, a seismic separation joints or full height partition thatbreaks the ceiling up into areas not exceeding 2,500 ft2 shall be providedEXCEPTION

Structural analyses of the ceiling bracing system for the prescribed seismic forces thatdemonstrate ceiling system penetrations and closure angles provide sufficient clearanceto accommodate the anticipated lateral displacement.

o

Except where rigid braces are used to limit lateral deflections, sprinkler heads and otherpenetrations shall have a 2 inches oversize ring, sleeve, or adapter through the ceiling tileto allow for free movement of at least 1 inch in all horizontal directions.

Alternatively, a swing joint that can accommodate 1 inch of ceiling movement in allhorizontal directions is permitted to be provided at the top of the sprinkler headextension. (see example illustrations for flex drops)

o Changes in ceiling plan elevation shall be provided with positive bracing. (See exampleillustrations below)

o

Cable trays and electrical conduits shall be supported independently of the ceiling per ASCE7-05 chapter 13 requirements.

o

Integral Construction. As an alternate to providing large clearances around sprinklersystem penetrations through ceiling systems, the sprinkler system and ceiling grid arepermitted to be designed and tied together as an integral unit. (ASCE 7-05 13.5.6.3)

Such a design shall consider the mass and flexibility of all elements involved, includingthe ceiling system, sprinkler system, light fixtures, and mechanical (HVAC)appurtenances. Such design shall be performed by a registered design professional.

Perimeter hangers - terminal ends of each cross runner and main runner shall be supportedindependently a maximum of 8” inches from each wall or ceiling with number12 gage wire orapproved wall support.

Vertical wires shall be attached to the suspension member and to the support above with a

minimum of three turns.

Trapeze or equivalent device may be used where obstruction precludes direct suspension.

Seismic separation joints shall be installed per manufacturer’s specifications & approved plans.

Vertical hangers: Suspension wires shall not be smaller than #12 gauge spaced at 4’ oncenter or #10 gauge at 5’ on center along each main runner.

Compression strut/seismic posts are typically required every 144 sq. ft., starting a maximum6’-0” from perimeter with seismic wires (4) directions @ max. 45 degrees from horizontal.

Partitions Tied To Suspended Ceilings (ASCE 7-05 13.8)o

General. Partitions that are tied to the ceiling and all partitions greater than 6ft in heightshall be laterally braced to the building structure.

Such bracing shall be independent of any ceiling splay bracing.

Bracing shall be spaced to limit horizontal deflection at the partition head to becompatible with ceiling deflection requirements as determined in Section ASCE 7-0513.5.6 for suspended ceilings and elsewhere in this section for other systems.EXCEPTION: Partitions that meet all of the following conditions:1) The partition height does not exceed 9 ft.2)

The linear weight of the partition does not exceed the product of 10lb times theheight (ft) of the partition.

3) The partition horizontal seismic load does not exceed 5 psf.


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Fire ratings shall comply with the requirements of the 2010 California Building Code chapter7, UL listing, Office of the State Fire Marshal’s listing, and installation per the manufacturer’ssuspended ceiling system installation manual.o The components and installation details must conform to the U.L. or SFM approval for the

design number specified.o

Custom designs which combine components from different approved designs but have notbeen tested as a complete assembly are not acceptable .

o

For schools and Essential Services Buildings, bracing assemblies are required for each 96square feet.

o

The first bracing assembly is required not more than four (4) feet from each wall.o A minimum of one bracing assembly is required between any two adjacent expansion cut-

outs on runners being braced.

Fire Separation Marking and Identification Requirements

Fire walls, fire barriers, fire partitions, smoke barriers and smoke partitions or any other wall required to have protected openings or penetrations shall be effectivelyand permanently identified with signs or stenciling. (2010 CBC section 703.6) O Such identification shall:

Be located in accessible concealed floor, floor-ceiling or attic spaces; Be repeated at intervals not exceeding 30 feet measured horizontally along the wall or

partition; and Include lettering not less than 0.5 inch in height, incorporating the suggested wording:

"FIRE AND/OR SMOKE BARRIER-PROTECT ALL OPENINGS," or other wording.Exception: Walls in Group R-2 occupancies that do not have a removable decorativeceiling allowing access to the concealed space.

ABOVE CEILING INSULATION

Concealed installation. Insulating materials, where concealed as installed in buildings ofany type of construction, shall have a flame spread index of not more than 25 and a smoke-

developed index of not more than 450. (2010 CBC section 719.2)o Facings. Where such materials are installed in concealed spaces in buildings of Type III,

IV or V construction, the flame spread and smoke-developed limitations do not apply tofacings, coverings, and layers of reflective foil insulation that are installed behind and insubstantial contact with the unexposed surface of the ceiling, wall or floor finish. (2010CBC 719.2.1)Exception: All layers of single and multilayer reflective plastic core insulation shall comply with

Section 2613.

Exposed installation. Insulating materials, where exposed as installed in buildings of anytype of construction , shall have a flame spread index of not more than 25 and a smoke-developed index of not more than 450. (2010 CBC 719.3)

Surface insulation or other purposes shall be considered interior finish if they cover 10percent or more of the wall or of the ceiling area, and shall not be considered decorative materials or furnishings. (2010 CBC 806.1)o Paper faced insulation is not permitted in exposed above ceiling areas, the open side of

furred spaces, and ventilated interstitial spaces due to the potential of embers igniting thepaper.

o

Quilted foil-backed or un-faced fiberglass batts and blankets are better suited to conditionsof potential fire hazards.

o

Use approved quilted foil-backed insulation such as “Reflectix Insulation” in areas where a

vapor barrier is required and use as a fix when paper back insulation is exposed.


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ELECTRICAL Abandoned cables are not permitted to remain. CEC 800.52 (b

Junction boxes and similar enclosures shall be accessible and shall have required workingclearances CEC 314.29, 110.26(a)

Cables and raceways shall not be supported by ceiling grids. CEC 300.11(a)

CEILING MOUNTED AIR TERMINALS

Air terminals weighing less than 20 pounds shall be positively attached using sheet metalscrews. Minimum of two screws are to be installed on each side of the terminal, near thecorners, and fastened into the main runners.

Air terminals weighing 20 lbs but not more than 56 pounds, in addition to the above, shallhave two #12-gage hangers connected from the terminal or service to the ceiling systemhangers or to the structure above. These wires may be installed with limited slack.

Air terminals weighing more than 56 pounds shall be supported directly from the structureabove by approved hangers.

RETURN AIR PLENUMS Verify that all materials meet the applicable flame spread rating for return air plenums and

ducts noted as “plenum rated”.

Equipment and devices shall be permitted only when necessary for their direct action upon, orsensing of, the contained air. CEC 300.22 (b)

Verify that fire damper is clear and operational. CBC

Communication plenum rated cable (CMP) shall be listed as suitable for use in ducts,plenums and listed as having adequate fire resistant and low smoke producing characteristics.CEC 800.179 (a), CEC 800.154 (a)

LIGHTING FIXTURE SUPPORTS Only “Heavy-Duty” systems listed for Seismic Design Category D shall be used in the City of

Palo Alto.

All lighting fixtures shall be positively attached to the suspended ceiling system with 4 screws -typically one at each corner.

Wires required to the fixture:o

Fixture less than 56 lbs: two no. 12-gage hangers connected from the fixture housing tothe structure above. These wires may be installed with limited slack.

o Fixtures more than 56 lbs shall be supported directly from the structure above by approvedhangers.

o

Pendant Hung Fixtures shall be supported directly from the structure above with #9 gaugewire without using the ceiling suspension system for direct support.

ASCE 7-05 CHAPTER 13 SEISMIC BRACING EXEMPTIONS FOR PIPING SYSTEMS

The exemptions that apply specifically to seismic bracing for piping systems are covered inSection 13.6.8 of ASCE 7-05. The provisions of this section do not cover elevator system piping which is covered in Section

13.6.10 of ASCE 7-05. Also not covered in this section is fire protection piping. Fire protection piping will be covered

in a separate publication. The piping considered in this section is assumed to be high-deformability piping.

o This implies pipes made from ductile materials that are joined by welding, brazing, orgroove type couplings, similar to Victaulic couplings, where the grooves in the pipe havebeen roll formed rather than cut.


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ASCE 7-05 CHAPTER 13 SEISMIC BRACING EXEMPTIONS FOR PIPING SYSTEMS(continued)

Limited deformability piping on the other hand, would be pipes made of ductile materials thatare joined by threading, bonding, or the use of groove type couplings where the grooves inthe pipe have been machine cut.o

Low deformability piping would be comprised of pipes made from relatively brittle materials

such as cast iron or glass.The 12 inch Rule (ASCE 7-05 Section 13.6.8-1]1): No restraints will be required for piping that meets the requirements of the 12 inch Rule for

the entire piping run. The 12 inch Rule will be said to apply to a piping run if:o

The piping is supported by rod hangers.o

For single clevis supported pipe, all of the hangers in the piping run are 12 inches or less inlength from the top of the pipe to the supporting structure.

o For trapeze supported pipe, all of the hangers in the piping run are 12 inches or less inlength from the top of the trapeze bar to the supporting structure.

The past practice by SMACNA and other recognized authorities in the industry to call for the

connection between the hanger and the supporting structure to be “non-moment generating”.

This means that the connector must be one that allows the piping run to swing freely on itshangers without introducing a bending moment in the hanger.o

There must be sufficient space around the piping run to accommodate the expected motionof the pipe as it sways back and forth with the earthquake motion in the building.

o Connections between the piping and the interfacing components must be designed and/orselected to accept the full range of motion expected for both the pipe and the interfacingcomponent.

Single Clevis Supported Pipe in Seismic Design Categories D (ASCE 7-05 Sections 13.6.8-2a and13.6.8-2c)

For single clevis supported piping in buildings assigned to Seismic Design Categories D forwhich the Component Importance Factor is equal to 1.5, and for which the nominal size is 1inch or less; no seismic restraint is required.

For single clevis supported piping in buildings assigned to Seismic Design Categories D forwhich the Component Importance Factor is equal to 1.0, and for which the nominal size is 3inches or less; no seismic restraint is required.


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Exemptions for Trapeze Supported Pipe per VISCMA Recommendations

Neither ASCE 7-98-02 nor ASCE 7-05 specifies how the piping is to be supported. The point is that many pipes of the exempted size may be supported on a common trapeze

bar using hanger rods of the same size as would be specified for a single clevis supportedpipe.o

Keep in mind that the purpose of the seismic restraints is to make sure the pipe moves

with the building.o The amount of force that the hanger rod must carry will be a direct function of the weight

of pipe being supported.o There must be some limit to how much weight a trapeze bar can support for a given

hanger rod size before seismic restraint is required.

VISCMA (Vibration Isolation and Seismic Control Manufacturer’s Association) has investigated thisissue and can make the following recommendations on the application of the exemptions inSections 5.4 and 5.5 above to trapeze supported pipe, www.viscma.com. The following basic provisions must apply:

o The hangers must be ASTM A36 all-thread rod.o

The threads must be roll formed.o

The pipes must be rigidly attached to the hanger rods.o

Provisions must be made to avoid impact with adjacent pipe, duct, equipment, or buildingstructure, or to protect the pipe from such impact.

Trapeze Supported Pipe in Seismic Design Category D: (ASCE 7-05 Sections 13.1.4-5, 13.6.8-2a, and 13.6.8-2c) For trapeze supported piping in buildings assigned to Seismic Design Category D, which have a

Component Importance Factor equal to 1.5, and for which the nominal size is 1 inch or less,no seismic restraint is required if:o The trapeze bar is supported by 3/8-16 UNC, or larger, hanger rods.o

The maximum hanger spacing is 7 ft. on center.o

The total weight supported by the trapeze bar is 4 lbs/ft or less. For trapeze supported piping in buildings assigned to Seismic Design Category D, which have a

Component Importance Factor equal to 1.0, and for which the nominal size is 3 inches or less,no seismic restraint is required if:o

The trapeze bar is supported by ½”-13 UNC, or larger, hanger rods.o The maximum hanger spacing is 10 ft. on center.o The total weight supported by the trapeze bar is 25 lbs/ft or less.

The Seismic Design Category to which the project has been assigned must be known.o

This should be noted on the issued permit plans.o The design professional responsible for the piping system must assign an appropriate

Component Importance Factor to the system. As a sidebar to the previous statement, it should be noted that the specification for the buildingmay increase the Seismic Design Category in order to ensure an adequate safety margin and thecontinued operation of the facility. This is a common practice with schools, government buildings,and certain manufacturing facilities.

The building owner has the prerogative, through the specification, to require all of the pipingsystems to be seismically restrained. Careful attention to the specification must be paid, as someor all of the exemptions in this section may be nullified by specification requirements that aremore stringent than those provided by the code.


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DETAILS

REFERENCES

STANDARDS


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EXAMPLES OF DRYWALLL SUSPENDED CEILING SYSTEM - NO MIXING COMPONENTS

EXAMPLES OF DRYWALLL SUSPENDED CEILING SYSTEM - NO MIXING COMPONENTS


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EXAMPLES OF FLEXIBLE SPRINKLER SUSPENDED CEILING SYSTEM ATTACHMENTS

If the "cross-runners" are not the scarrying capacity as the "main-runnsupplementary #12 gauge hangerwires shall be attached at each sid


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EXAMPLES OF SEISMIC CONNECTORS FOR SUSPENDED CEILING SYSTEMS


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STANDARD FOR EXISTING SUSPENDED CEILING SYSTEM

UPGRADES


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U.B.C. STANDARD 47-18

T-BAR CEILING INSTALLATIONS

EXISTING

SYSTEMS

Systems installed prior to

Jan 1

2008 shall

be

upgraded

to

meet 1997 Standards 47 18.

UBC

STANDARD

47 18

INSTALLATION

REQUIREMENTS AND ILLUSTRATIONS

Part 11 1 ns tall a lon

Scope

Sec. 47.1808. This standard describes procedures for the installation o suspen

sion systems for acoustical

tile

and lay-in panels.

Installation of Components

Sec. 47.1809. a) Hangers. Hangers shall be attached to the bottom edge

of

the

wood joists or to the vertical face of the wood joists near the bottom edge. Bottom

edge attachment devices shall be an approved type.

In

concrete construction mount hangers using cast-in-place hanger wires hanger

inserts or other hanger attachment devices shall be an approved type. If greater

center-to-center distances than 4

feet

0 inch are used for the hangers reduce the

load-carrying capacity of the ceiling suspension system commensurate with the ac·

tual center-to-center hanger distances used.

Hangers shall

be

plumb and shall not press against insulation covering ducts or

pipes.

If some hangers must

be

splayed offset the resulting horizontal force

by

brac

ing,

countersplaying or other acceptable means.

Hangers formed from galvanized sheet metal stock shall be suitable for suspend

ing

carrying channels or main runners from

an

existing structure provided that the

hangers do not yield twist or undergo other objectionable movement.

Wire

hangers

for

suspending carrying channels or main runners from an existing

structure shall be prepared from a minimum of No. 12-gage galvanized soft-an

nealed mild steel wire.

Special attachment devices that support the carrying channels or main runners

shall be

approved to support

five

times the design load.

b) Carrying Channels. The carrying channels shall be installed so that they are

all

level to within Y inch i n 12 feet.

Leveling

shall

be

performed with the supporting hangers taut.

Local

kinks or bends shall not

be

made

in

hanger

wires as

a means

o

leveling car

rying

channels.

In installations where hanger wires are wrapped around carrying channels the

wire

loops

shall

be tightly formed to prevent any vertical movement or rotation of

the

member

within the loop.

1368


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988 EDITION 47-18

c) Msin Runners. Main runners shall

be

installed so that they are all

level lO

within Y inch in

12

feet.

Where main runners are supported directly

by

hangers, leveling shall

be

per-

formed with the support.ing hanger taut.

Local kinks or bends shall not be made in hanger wires as a means of

leveling

main runners.

In

installations where hanger wires are wrapped through or around main runners,

the wire loops shall be tightly wrapped and sharply bent.

d) Cross Runners. Cross runners shall be supported by either main runners or by

other cross runners to within

X

inch

of

the required center distances. This tolerance

shall be noncumulative beyond

12

feet.

Intersecting runners shall form a right angle.

The exposed surfaces

of

two intersecting runners shall

lie

within a vertical distance

of 0.015 inch

of

each other

with

the abutting cross) member always above the con

tinuous main) member.

e) Splines. Splines used to form a concealed mechanical joint seal between adja

cent tiles shall

be

compatible with the tile kerf design so that the adjacent tile

will

be

horizontal when installed. Where splines are longer than the dimension between

edges of supporting members running perpendicular

to

the splines, place the splines

so that they rest either all above or all below the main running members.

f)

Assembly Devices. Abutting sections of main runner shall be joined

by

means

of suitable connections such

as splices, interlocking ends, tab locks, pin locks, etc. A

joint connection shall be judged suitable both before and after ceiling loads are im

posed

if the joint provides sufficient alignment so that the exposed surfaces of two

abutting main runners lie within a vertical distance of 0.015 inch of each other nd

within a horizontal distance of 0.0

S

inch of each other.

There shall be no visually apparent angular displacement

of

the longitudinal axis

of one runner with respect to the other.

Assembly devices shall provide sufficient spacing control so that horizontal gaps

between exposed surfaces of either abutting or intersecting members shall not exceed

0.020 inch.

Spring

wire dips

used for supporting main runners shall maintain tight contact

between

the main runners and the carrying channels when the ceiling loads are im

posed on the runners.

g)

Ceiling Fixtures. Fixtures installed in acoustical tile or lay-in panel ceilings

shall be mounted

in

a manner that will not compromise ceiling performance.

Fixtures shall not be supported from main runners or cross runners if the weight

of the fixtures causes the total dead load to

e x ~ e d

the deflection capability of

the

ceiling suspension system.

In

such cases, the fixture load shall be supported by sup

plemental hangers within 6 inches

of

each corner, or the fixture shall

be

separately

supported.

Fixtures shall not

be

installed so that main runners or cross runners will be eccen

trically loaded except where provision

is

inherent in the system or

is

separately

pro-

vided for)

to

prevent undesirable section rotation or displacement, or both.

In

ny

case, runners supporting ceiling fixtures shall not rotate more than 2 degrees after

the

fixture loads are imposed.

Where fixture installation would produce rotation of runners in excess of

2

degrees, install fixtures with the use of suitable accessory devices. These devices shall

support the fixture

in

such a manner that the main runners and cross runners

will be

loaded symmetrically rather than eccentrically.

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47 18

U.B.C. STANDARDS

Part l l l Latmal Design Requirements

Scope

Sec. 47.1810. Snspencled ceiling which

are

designed

and

constructed

to

support ceiling

panels or tiles, with or without lighting fixtures, ceiling mounted air terminals or other

ceiling

mounted

services shall comply with

the

requirements of this standard.

EXCEPTIONS: I. Cci

ling

an· a of 14 4 square feet or less surrounded by walls which connect

dir..:ctly to

the

stn1cture above shnll be exempt from the lateral load design requirements of these

~ t a n d a r d s

2. Ceilings constr11ctrd of l ~ t h and plaster or gypsum board. screw or nail attached to

suspcndrd members tlmt support a ceiling on one level extending from wall to wall.

Minimum Design Loads

Sec

47.1811.

a) Lateral Forces. Such ceiling systems and their connections to the

building structure shall be designed and constructed to resist a lateral force specified

in

Chapter

3

of he Uniform Building Code.

Where

the ceiling system provides lateral support for nonbearing partitions, it shall be

designed for the prescribed lateral force reaction

from

the partitions u specified in Section

47.1815.

Connection of lighting fixtures

to

the

ceiling system shall

be

designed for a lateral force

of

100 percent of

the

weight of

the

fixture in addition to

the

prescribed vertical loading as

specified in Section 47 1813

b) Grill

Members, Connectors anu Expansion Devices. The main runners and cross

runners

of the ceiling system and their splices, intersection connectors and expansion

devices

shall

be

designed

and

constructed to carry a mean ultimate test load

of

not less than

180

pounds or

twice the actual load, whichever is greater,

in

tension with

a

5-degree

misalignment of the members in any direction, and in compression. In lieu of 5-degree

misalignment, the load may be applied with a l-inch eccentricity on a sample not more than

24

inches

long

each

side of

the

splice. The connections at splices and intersections all shall be

of the

mechanical interlocking type.

Where the composition or configuration of ceiling systems members or assemblies and

their connections

are

such that calculations of their allowable load-carrying capacity cannot

be made in accordance

with

established methods of analysis, their performance shall be

established by test.

Evaluation of test results shall be made on the basis of

the

mean values resulting from tests

of not

fewer than

three identical specimens, provided

the

deviation of any individual test

result from

the

mean

value does not exceed plus or minus I 0 percent. The allowable load

carrying capacity as determined

\ ly

test shall

not

exceed one half of the mean ultimate test

value.

(c)

Substantiation. Each ceiling systems manufacturer shall furnish lateral loading

capacity and displac

1

ement or elongation characteristics for his systems, indicating the

following:

I.

Maximum

bracing pattern

and

minimum wire

siz.es.

2. Tension and compression force capabilities of main runner splices, cross runner

connections

and

expansion devices.

All tests shall be conducted by

an

approved testing agency.

Installation

Sec.

47.1812. (a)

Vertical Hangers. Suspension wires shall be not smaller than No.

12

gage

spaced

at 1 feel on center or No. 10 gage at 5 feet on center along each main runner

unless

calculations justifying the incre


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988 EDITION

47-18

Each vertical wire shall be attached

to the

ceiling suspension member

and to the

support

above with a minimum of three turns. Any connection device at the supporting construe lion

shall be capable of carrying not less than 100 pounds.

Suspension wires shall not hang more than l

in

6 out-of-plumb unless countcrsloping

wires are provided.

Wires

shall not attach

to

or bend around interfering material or equipment. A trapeze or

equivalent device shall be used where obstructions preclude direct suspension. Trapeze

suspensions shall

be

a minimum

of

back-to-back

11/4-inch

cold-rolled channels

for

spans

exceeding

48

inches.

(b) Perimeter Hangers.

the

terminal ends of each cross runner and main runner shall

be

supported independently a maximum of 8 inches from each wall or ceiling discontinuity

with No. 12 gage wire or approved wall support. •

c) Lateral Force Bracing. Where substantiating design caltulations

are

not provided,

horizontal restraints shall be effected by four No. I 2 gauge wires secured to the main runner

within 2 inches of

the

cross runner intersection

and and

splayed 90 degrees from each other

at

an

angle not exceeding

5

degrees from the plane

of the

ceiling. A strut fastened

to the

main

runner shall

be

extended

to

and

fastened

to

the structural members supporting

the

roof or

floor above. The strut shall be tH.lcquatc to resist

the

vertical component

i n u t l ~ c t l by

the

bracing wires. These horizontal restraint points shall be placed 12 feet on center in both

directions with the first point within 6 feet from each wall. Attachment of the restraint wires

to

the structure above shall be adequate for the load imposed.

Lateral force bracing members shall be spaced a minimum

of

6 inches from all horizontal

piping or duct work that

is

not provided with bracing restraints for horizonta I forces. ·Bracing

wires shall be attached to the grid and to the structure

in

such a manner that they can support a

design load of not less than 200 pounds or

the

actual design load, whichever

is

greater, with a

safety factor of 2.

d) Perimeter Members. Unless perimeter members are a structural part of the approved

system, wall angles or channels shall be considered as aesthetic closers and shall

have

no

structural value assessed

to

themselves or their method

of

attachment

to

the walls.

or

tile

ceilings, ends of main runners

and

.cross members shall be tied together

to

prevent their

spreading.

e)

Attachment of Members to the Perimeter.

To

facilitate installation, main runners

and cross runners

may

be attached to the perimeter member at two adjacent walls with

clearance between the wall and the runners maintained

at

the other two walls or as otherwise

shown or described for

the

approved system.

Lighting Fixtures

Sec.

47.1813.

Only intermediate

and

heavy duty

c;eiling

systems

as defined in

Section

47.1802

may be used for the support of lighting fixtures.

All

lighting fixtures shall

be

positively attached

to the

suspended ceiling system. The

attachment device shall have a capacity of 100 percent of the lighting fixture weight acting in

any

direction.

When intermediate systems are used, No.

12

gage hangers shall

be

attached

to the

grid

members within 3 inches of each corner of each fixture. Tandem fixtures may utilize

common wires.

Where heavy duty systems are used, supplemental hangers are not required if a 8 inch

modular hanger pattern

is

followed. When cross runners are used without supplemental

hangers

to

support lighting fixtures, these

c;ross

runners must provide the same

carrying

capacity as the main runner.

Lighting fixtures weighing less than 56 pounds shall have,

in

addition to the require rnents

. 1371


30/30

47-18

U.B.C. STANDARDS

outlined above,

two

No.

12

gage hangers connected from the fixture housing

to

the structure

above.

These wires may

be

slack.

. Lighting fixtures weighing

56

pounds or

more

shall be supported directly from the

structure above by approved hangers.

Pendant-hung lighting fixtures shall be supported directly from the stnrcture above using

No. 9 gage wire

or

approved alternate support wjthout using the ceiling suspension system

for

direct support.

Mechanical Services

t

J J

•

2. S

C Q f 2 1.-1.. ')'

I\'-.) tb

,.,,

-'

\ i ~ \A A A 11 j2. \..- .. tv V R.._

. ~ n t e d air terminals or services weighing

less'

tthan

20

pounds shall

be

ositivel attache_

Seismic Suspend Ceiling-1

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