NATIONAL BUREAU OF STANDARDS REPORT

5608

REPORT OF FIRE TEST OF

CELLULAR STEEL DECK AND BEAM

by

Jr V, Ryan

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT MBS REPORT

1002-30-4820 October l4, 1957 5&08

REPORT OF FIRE TEST OF

CELLULAR STEEL DECK AND BEAM

by

J® Vo Ryan

for

Department of the Air Force

(AFCIE-ES)

IMPORTANT NOTICE

NATIONAL BUREAU OF STANDARDS REPORTS are usually preliminary or progress accounting documents

intended for use within the Government, Before material in the reports is formally published it is subjected

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however, by the Government agency for which the Report has been specifically prepared if that agency wishes

to reproduce additional copies for its own use,

U. $. DEPARTMENT OF COMMERCE

REPORT OF FIRE TEST OF

CELLULAR STEEL DECK AND BEAM

ABSTRACT

A fire endurance test was conducted on a floor specimen consisting of a beam supporting cellular

steel deck units of two cross-sections * The beam

was encased in metal lath and gypsum-vermiculite

plaster* The cellular units had concrete fill

above and vermiculite acoustical plastic below*

The results indicated a fire resistance of b hr

25 min for the particular specimen tested*

1. Introduction

The use of floors of concrete on cellular steel units

various units has increased in recent years* The cells of uh_lo;> have been designed and proposed as raceways for electrical wiring ? telephone lines, and ducts of air-cooling systems* Such use permits

. the direct application of ceiling finish or acoustical material without leaving exposed raceways and Thl3 lead t

? reduction of overall heights of

^ii 1S

+:oryJ

kUildings, or increase In the number of stories, without reduction of the headroom in each story* Because such construction is of interest to the public and the government, a specimen of this type was subjected to fire

t

r lrd °f * 3 ?T ies of related tests* The specimen consisted of a combination of cellular units of two cross-

? u

i tadle for electrical and telephone lines lntended to serve as an air duct, with conThf o 1

- ad 9^e and vermiculite acoustical plastic below*

. included a steel beam encased in expanded metal lath and gypsum vermiculite plaster*

2» Materials and Specimen

A steel beam 8 in*

(8WF24- section) and 13

deep, 6-g- in* across the flange

ft 2 in* long was secured to 1 in*
thick steel plates at each end by standard steel angle

connectors bolted to the web of the beam and to the plates*

The plates were bolted to the steel H-section frame of the

floor- test furnace with a gap between each plate and the

frame q The two gaps totalled 1 1/8 in* and were intended to

allow for some expansion of the beam and some tilting of

the plates as the beam deflected , thereby permitting

consideration of the beam as only partially restrained at

the ends* This was intended to be representative of the

conditions existing in buildings having such beams* The

plates and beam were so located that the latter spanned

the short dimension of the 18 ft by 13 ft 6 in* furnace

opening and the centerline of the beam, was 9 ft 10 in*

from one end, and 8 ft 2 in® from the other*

Cellular steel deck units were placed to span from the

beam to steel bearing angles bolted to the furnace frame

across each end. The units were of two cross-sections®

For the first, each unit was ma.de of two sheets of metal

formed and spot welded together to make four nearly

rectangular cells of 3 1/8 in* overall height, 3 3/4- in*

average width, with space between cells an average of 2 1/4-

in® The upper sheet was of 18 ga (U«S* Std plate) steel,

the lower of 16 ga* The upper sheet was bent along each

edge to form a standing seam interlocking joint between

units* The units were 3 1/8 in* deep and 24- in* wide*

For the other cross-section, each unit was made of two sheets

of metal formed and spot welded together to make a single

cell of 3 1/8 in* overall height and 9 5/8 in* average

width* This single cell has been proposed for use as a

duct for cool air circulation* Both sheets were of 14- ga

steel* The upper sheet was bent along each edge to

provide the same joint as the 4—cell unit* The single-cell

units were 3 1/8 in* deep and 12 in* wide*

The two types of units were alternated, starting with

a 4—cell unit* They were welded to the beam and bearing

angles at 12 in* oc for the 4—cell units and 6 in* oc for

the single-cell air duct units* After all the units were

in place, the joints were spot welded by an electric arc

welder* Preformed sheet steel cover plates were placed

over the end-to-end joints between units above the beam*

Holes were punched through at the joints between units

and between cells of the 4— cell units and 0*164- in* diameter

hanger wires dropped through* Each wire had a loop of about

1 in. diameter at the top, which loop rested on the steel

deck units* The wires were located at 12 in* oc along each

side of the beam. Each was bent to pass under the beam and
3

“

lap 3 1/2 to 6 in,, on a wire from, the opposite side. The

pairs of wires , one from each side of the beam, were laid

together below the beam and tied together with 18 ga wire*

Transit mixed concrete, proportioned 1 part cement,

2 parts Potomac River sand, and 4- parts Potomac River

gravel (both siliceous aggregates) was poured on the deck

and screeded to a depth of 2 1/2 in, above the top plane

of the steel deck units. The upper surface of the concrete

was 1 in. above the top of the furnace restraining frame.

The concrete delivery ticket indicated that the gravel

had passed through a 3/4 in. sieve * Flat di amend-mesh expanded metal lath (nominal 3*4

lb/yd2

, actual 3«26 lb/yd2 ) was bent into U- or channelshaped pieces to fit around the bottom and sides of the

beam. The lath was tied to the wire hangers with single

strands of 18 ga wire at top, center, and bottom of each

side and at the center of the beam soffit. Corner beads,

consisting of a formed sheet metal nose and woven wire

legs, were prepared with 3 in, wide strips of metal lath

as 4 to 5 in* extensions of the legs at about 2 ft oc.

These leg extension pieces were tied to the metal lath,

on the beam so that the corner beads provided 1 1/2 in,

grounds for plaster, as measured from the face of the

lath* Wooden screed strips were tied to the face of the

metal lath about 2 1/2 in* from the top of the beam* These

strips provided 1 1/2 in. grounds*

Gypsum-vermiculite plaster was applied to the metal

lath in two coats* The first or scratch coat plaster

was mixed in the ratio of 1 bag (nominal 99« 2 5 lb net)

unfibered gypsum cement plaster to 2 ft/ of vermiculite

plaster aggregate, with 4 oz of accelerator added per

bag of plaster* This coat was applied by trowel and

care taken to fill the corner bead and to provide a good

key behind the lath* The thickness over the face of the

lath averaged about 1/4 in. The plaster surface was

scratched with a wire tool for the purpose* The brown

coat plaster was mixed in the ratio of 1 bag of gypsum

to 3 ft-5 of vermiculite aggregate to 4 oz of accelerator*

It was sprayed on by a Thomsen Supply Company "Tommy Gun,” a commercially available machine built for this

use* The surface was screeded smooth, and the wooden ground

strips removed* The spaces they had occupied were filled

with brown coat plaster* Following the plaster application,

the underside of the cellular deck units was wiped carefully

to remove all spatterings.
Aluminum foil faced glass fiber insulation board was

cemented to the lower surface of the air duct units. The

insulation was in pieces 15 3/8 in. wide with a notch in

the glass fiber about 1 3/8 in, from each edge. Adhesive

was spread on the glass fiber surface of each piece, the

pieces bent along the notches, and the glass fiber surfaces

pressed against the lower surfaces of the air duct units.

After all the air duct units had the insulation applied,

the butt joints between pieces of insulation, and the edge

joints between the insulation and deck units were covered

with a 2 in, wide vapor barrier tape. The 15 3/8 in.

wide pieces, with foil, weighed 0,5*+ lb/running foot.

Copper-clad steel studs (in the same shape as nails)

3 A in, long, 0,103 in. diameter, with 3/18 in. diameter

heads were applied to the under side of the deck by

"flash-welding" the stud heads to the steel units. They

were spaced 6 .in, oc along lines about 8 to 8 1/4 in, from

and parallel to the centerlines of the air duct units.

Fiat diamond mesh expanded metal lath was cut in

strips about 19 in. wide and 97 1/2 in. long. The lath was

the same as that used around the steel beam. The strips

were placed below and with their long dimensions parallel

to the insulated air duct units. They were stretched

across the insulation, engaged on the lines of studs and

held by locking clips shoved on the studs. The bow of the

lath across the insulation left a clearan.ee of about 5/18

in 9 from the face of the lath to the foil face on the

insulation.

Vermiculite acoustical plastic was applied to the under

side of the deck. The plastic was prepared by mixing a

dry loose material with water. The dry material, a proprietary product, was not identified, either by analysis or by

manufacturers statement. The plastic was prepared in the

same mixer and sprayed by the same machine as used for the

plaster, except that the second application was by trowel,

The weights and densities for the acoustical plastic, and

for the plaster, are given in Table 1 , The first application filled the spaces between the cells of the 4-cell

units and was brought out flush with the bottoms of the

latter 5 the second application, by trowel, filled the

spaces behind the metal lath strips and built up about 1/4

in® thickness over the lath; the third was intended to

build up a thickness of 5/8 in. below the cells of the

4-cell units and 1 1/8 in. from the face of the metal lath

under the air duct units; the fourth and fifth were to fill

cracks and patch four areas each about 1 fA from which the
5- plastic had fallen or loosened 5 the sixth an attempt to

develop a more uniform contour and thickness 5 and the

seventh a texture coat* The texture coat material contained

white pigment , all other coats did not contain white

pigment * The various applications were spaced from one to

eight days apart* A total of 33 days elapsed from the first

to the seventh application* An additional 15 days elapsed before the test*

The day before the test a series of measurements were

made with a wire probe to determine the average thickness of

acoustical plastic* Measurements from 33 symmetrically

distributed points indicated an average thickness of about

11/16 in* under the 4-cell units 5 and measurements from

16 symmetrically distributed points indicated average

thickness of about 1 25/64 in* from the aluminum foil face

of the glass fiber insulation* Allowing for the bow of the

lath under the insulation (approximately 5/16 in*), the

thickness from the face of the lath was about 1 1/16 in.

Some of the details of the construction are shown in

figure 1 .

3 * Test Method

The specimen was subjected to fire test in general

compliance with the methods defined in the Standard Methods

for Fire Tests of Building Construction and Materials,

ASTM E-119*

3 o 1 Furnace

The furnace was in the shape of a large, fire-brick

lined box with the specimen filling the otherwise open top.

The furnace was equipped with steel frame to support

and restrain the specimen, gas-air burners, thermocouples,

loading apparatus, means for measuring deflections, and

windows through which the exposed surface could be observed

during the test*

3®2 Aging

The specimen aged 15 days from the application of the

thin texture coat but 22 days from the last application of

base coat material to develop the full thickness. The
- 6 -

period of aging was determined by periodic weighing

of a representative sample of the construction. Aging

was continued until the weight was essentially constant

for five consecutive days.

3*3 Loading

The dead load or weight of the specimen was ^5»5

lb/ft 2 of floor area, as computed from the weights of

samples of the materials. The applied or live load computed

to produce a deflection of I/36 O of the span of the

cellular units was 108 lb/ft2

. The design load for the

SWFl^- steel beam, on 13 ft 2 in, span, was 20,8 kips. The

total floor load provided 16,6 kips. Therefore, weights

in the amount of 285 lb/lin ft were placed on the floor

above the beam to bring the beam load up.

3,*+ Temperatures

Temperatures were measured by means of chromel-alumel

thermocouples connected to self-balancing potentiometers

calibrated to read directly in degrees C« Thermocouples

were placed in the furnace chamber, on the steel beam,

the cellular steel deck, and the unexposed surface. The

thermocouples in the furnace chamber were in porcelain insulators and encased in wrought iron pipes; the others

were in glass fiber sleeving. The thermocouple locations

are indicated in figure 1, The furnace fires were controlled

to produce temperatures as near as feasible to those of

the Standard Time-Temperature Curve defined in ASTM E-119,

which include: 1000°F at 5 min. 1300°F at 10 min, 1550°F

at 30 min, 1700°F at 1 hr, l850°F at 2 hr, 2000°F at 4- hr,

and 2300° F at 8 hr.

3*5 End-Point Criteria

The Standard Test Method required that: 1) the

specimen continued to sustain the applied load, 2 ) flames,

or gases hot enough to ignite cotton waste, not have

passed through the specimen, 3 ) transmission of heat

shall not have been such that the average temperature of

the unexposed surface increased 250 degrees F nor the

temperature at any one point have increased 325 degrees F

above their initial values* The fire endurance was

defined as the time at which the first of these conditions
-7

was attained, with a correction to the time for variation,

if any, of the furnace temperatures from those defined.

4- a Results

The fire test was conducted August 15? 1957* By 23

minutes there were two cracks across the beam soffit,

one of which extended up the North face of the beam

protection^ An odor, similar to that of burning plastics,

had become fairly strong by 2 7 min and continued so for

the next 1/2 to 3/4- hour® By 1 hr 4-3 min there were still

only two cracks in the beam protection and a crack 1/8 in®

wide across the unexposed surface above the beam* The net

deflection at the center of the beam was 0*1 in®; at the

centers of the floor areas on each side of the beam 0*4-

and 0 a 6 in« T he maximum temperature of the beam was about

295°F arid the average temperature of the unexposed surface

had risen about 85 deg F above its initial value* By 2 hr

12 min there were fine diagonal cracks across all corners

of the unexposed surface and appreciable amounts of smoke

were issuing from the periphery* At 3 hr 9 min, a loud

metallic thump was heard but there was no fluctuation of

oil pressure in the loading system nor sudden change of

deflection* The net deflections at the centers of the

beam and the two sections of the floor were 0*7 in®, 0*6 in*

and 1*0 in* respectively* The average temperature on the

unexposed surface had risen 157 deg F and the maximum on

the beam was 725° F* By 3 hr 4-1 min, the larger of the two

cracks in the beam protection was about 3/16 in* wide*

The limiting one -point temperature rise of 325 deg F was completed on the unexposed surface at 4- hr 26 min, at which

time the maximum temperature of the steel beam was 991°F;

and the net deflections at the centers of the beam and the

two sections of the floor were 1*4- in*, 0*9 in,, and l*4b in*

respectively* An average temperature of 1000°F was reached

at one section of the beam at 5 hr 27 min* By 6 hrs 1 min

there was a crack 1/8 in* wide in the ceiling finish,

extending from, the beam cover to the North wall. The

maximum observed temperature on the beam was 1200°F and

the net deflections at the centers of the beam and two

sections of the floor were 2,8 in., 0,8 in., and 1.6 in, respectively, At 6 hr 12 min, a piece of ceiling finish about

1 ft was hanging from place near the South wall* The test

was stopped at 6 hr 33 min*
-8

After the test, and cooling, there were six cracks

across the team soffit, three of which extended up the

sides of the beam protection* There were several long cracks

in the ceiling finish parallel to the cellular units and

short transverse cracks under the air duct units. The surface of the acoustical plastic was slightly darker than

before the fire exposure. However, behind the texture

coat, the base coat plastic was a dark brown. During the

disassembly of the specimen, it was discovered that the

plaster keys of the beam protection were exceptionally heavy,

extending to the beam web in several places. It was

estimated that the heavy keys filled about one- third to

one-half the re-entrant space on each side. The approximate

volume filled is indicated on the cross-section of the

beam protection in figure 1,

The fire endurance of the specimen was limited by

one-point temperature rise of 325 deg F at 4 hr 26 min.

The control of the furnace fires was such that a correction

of minus 1 min was applicable to the failure time.

Therefore, the fire endurance limit was 4 hr 25 min for the

particular specimen tested. The beam and floor continued

to support the applied load throughout the 6 hr 33 min fire

exposure period, although temperatures were reached at

5 hr 27 min that would have been considered indicative of

failure in a test of a steel beam without applied load.
Table

!«,

Weight

and

Density

Data

on

Raster

and

Acoustical

Plastic i H

O- I i O t 8 rn

OJ

ONo 1 8 » 8 1 CMO

ON 1 o lr\ o ® 9 on \ H O

CM Etn NO

C\J

H

p 8P >> 0 0 I P

•H Oh 1—1 s CQ

cd •H

aa P o o

CD P Pi P Pp pnO

o3

p S €T» CnC,_) ~P P\ CD 0 P P ^ P Q CN On g CTN P &0 a pvn P 0 P Cti •H P •H H

tuOP co <p CO

N

•H \ d\ £ N 0 P ® p 0 O p Q P pfl3 Oo

CDp0pX

CD EH
. *
CO

crx

CO

LxJ >

cr

IDO

Ld

crID

h-<

cr; UJ

Q_

Q

<

COO

£o

o

o

o

o

crUJX

hUJQ

OO

CDU_

Jo

4 3dniVd3d^31

Fig. 2. Method of attachment for metal lath below air

duct units. Visible cracks due to shrinkage

of initial application of vermiculite acoustical

plastia.

Fig. 3* Condition of exposed surface after test. The

waviness in the specimen was the original

contour, not due to fire exposure.

U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its headquarters in Washington,

D. C., and its major field laboratories in Boulder, Colorado, is suggested in the following listing of

the divisions and sections engaged in technical work. In general, each section carries out spe- cialized research, development, and engineering in the field indicated by its title. A brief

description of the activities, and of the resultant reports and publications, appears on the

inside front cover of this report.

WASHINGTON, D. C.

Electricity and Electronics. Resistance and Reactance. Electron Tubes. Electrical Instruments. Magnetic Measurements. Dielectrics. Engineering Electronics. Electronic Instrumentation.

Electrochemistry.

Optics and Metrology. Photometry and Colorimetry. Optical Instruments. Photographic

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and Lubrication. Engine Fuels.

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Data Processing Systems. SEAC Engineering Group. Components and Techniques. Digital

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• Office of Basic Instrumentation • Office of Weights and Measures

BOULDER, COLORADO

Cryogenic Engineering. Cryogenic Equipment. Cryogenic Processes. Properties of Materials.

Gas Liquefaction.

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Propagation Services. Sun-Earth Relationships.

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Systems Application Engineering.

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