NATIONAL BUREAU OF STANDARDS REPORT

5376

REPORT OF FIRE TEST OF

CELLULAR STEEL DECK AND BEAM

by

J, Vo Ryan

NBS
THE NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1002-30-4820 July 8, 1957 5376

REPORT OF FIRE TEST OF

CELLULAR STEEL DECK AND BEAM

by

Jo Vo Ryan

for

Department of the Air Force

(AFCIE-=ES)

IMPORTANT NOTICE

NATIONAL BUREAU OF

intended for use within

to additional evaluation

listing of this Report, ei) the Office of the Directo however, by the Governr

to reproduce additional ^

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

or pi’ogress accounting documents

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ting, reproduction, or open-literature rmission is obtained in writing from

C. Such pemiission is not needed,

ally prepared if that agency wishes

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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REPORT OF FIRE TEST OF

CELLULAR STEEL DECK AND BEAM

ABSTRACT

A fire endurance test was conducted with a

floor specimen consisting of cellular steel deck

units supported by a steel beanio The beam was

encased in metal lath and gypsum-vermiculite

plaster o The cellular units had concrete fill

above and vermiculite acoustical plastic below®

The results Indicated a fire resistance of 2 hr

4-3 min for the particulan specimen tested®

lo introduction

The use of floors of concrete on cellular steel units

has increased in recent years o The cells of the units

have been employed or proposed as raceways for electrical

wiring and telephone lines® Such use would permit the

direct application of ceiling finish or acoustical material

without leaving exposed raceways and would lead to

reductions of the overall heights of multistory buildings

without reduction of the headroom in each story® Because

such construction is of interest to the government and

the public, a fire test was made to determine the fire

resistance of an assembly composed of cellular steel units

having concrete fill on top, and vermiculite acoustical

plastic applied directly to the under surface of the

cellular units® The specimen included a steel beam protected

by vermiculite-gypsum plaster on expanded metal lath®

2o Specimen

A steel beam 8 in® deep, 6-^ in® across the flange

(8WF2^- section) and 13 ft 2 in® long was secured to 1 in®

thick steel plates at each end by standard steel angle
„2»

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* The two gaps totalled 5/S in* and were intended to

allow for some expansion of the beam and some tilting of

the plates as the beam deflected downward 9 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 I8 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 dpck units 2 ft wide and 3 1/8 in®

deep were placed to span from the beam to steel bearing

angles bolted to the furnace frame at each end. The units

were of two lengths; 9 ft 9 1/8 in® and 8 ft 1 1/8 in®

They were welded to the tops of the beam and of the bearing

angles at 12 in* oc* Each unit was ro.ade of two sheets of

metal formed and spot welded together to form nearly

rectangular cells 3 1/8 in® high^ of 3 3/^ in® average

width, with space between cells aja average of 2 1/h in®

The upper sheet was of I8 ga steel and the lower of I6 ga

steel* The upper sheet was bent along each edge of each

unit to form an interlocking joint between units* After

all the units were in place and welded, the joints were

pinched together at 2 ft oc*

Holes were punched through between the cells and

0®19^ in* diameter wires hung through at 12 in® oc along

each side of the beam* The wires were about 1/h in* from

the beam at the top* Each was bent to pass under the

beam. Pairs of wires, one from each side of the beam,

were laid together about 5 1/2 in® directly below the beam

and wire-tied* Each of these heavy wires had a loop of

about 1 in® diameter at the top, which loop rested on the

cellular unit*

Transit-mixed concrete, proportioned 1 part cement,

3 parts Potomac River sand, and 5 parts Potomac River

gravel (both siliceous aggregates), was poured on the

deck and screeded to a depth of 2 1/2 in* above the tops

of the deck unit cells* The upper surface of the concrete

was 1 in* above the top of the furnace restraining frame.
3“

Flat, dlaniond mesh expanded metal, lathj nominally

3 9 ^ Ib/yd^, was bent into U- or channel-shaped pieces to

fit around the bottom and sides of the beamo The lath

was tied to each wire hanger with single strands of l8 ga

lathers tie wire at top, center, and. bottom of each side

and at the center of the beam soffit®

Gypsum-vermiculite plaster was mixed in the proportions of 1 bag (nominal net contents 99^25 lb) un~

fibered gypsum cement plaster, 2 1/2 ft-^ verm.iculite plaster

aggregate, h oz accelerator® T.he water averaged 12®2 gal

(102 3/^ lb) per batch* The plaster was mixed in a

machine built for the purpose® Plaster was trowelled on

in strips about 4- in* wide across the soffit and up each

side, at the center and about 1 ft from each end of the

beam, to form grounds® These strips were carefully checked

for level, or vertical, and for minimum depth of 1 1/2 in*

from the face of the lat,h* This plaster was allowed to

start to set and then the remainder of the lath was

covered by spraying the plaster on with the use of an

"Easy-On" machine* The sprayed plaster was rodded and

the drop-outs filled by trowelling.

The average density of the 10 ft3 of vermiculite

aggregate used was 7a 6 Ib/ft^, of three samples of the

freshly mixed plaster 72 lb/ft3* and of two samples of

the plaster as discharged from the spraying nozzle

77 Ib/ft^*

About two to three hours after the plaster application

to the beam had been completed, application of vermiculite

acoustical plastic to the under side of t.he cellular deck

was started® The deck units had been clean when received.

After the application of plaster to the beam, all

spattering s were wiped from the deck units before the

plastic was applied* The plastic came as a dry, loose

material in paper bags and required only mixing with water*

Its composition was not determined nor did the manufacturer

make any identification of the components* T.he dry material

and water were mixed in the same mixer and sprayed on from

the same machine used for the plaster on the beam* For

the initial application, the proportions as mixed were

one bag (average 23*1 lb) of dry material to 9 1/4 gal

(77 lb) of water; the average wet density of the freshly

mixed material was 45 lb/ft3, and of the material after
having been sprayed 5^ Ib/ft^Q This application filled the

spaces between the cells of the deck nnits* The plastic

was rodded off flush with the bottoms of the cells

One week was allowed to elapse during which time

the acoustical plastic shrank to produce cracks from 1/8

to 5/18 in, wide along one or both sides of each .cell and

from 1/k- to 3/8 in, wide across several of the filled

spaces. This shrinkage of the plastic caused the surface

to recede by as much as 5/8 in, from its original level.

Probing with fine wire Indicated that the cracks extended

the full 1 1/2 in, depth of the between-cells spaces.

For the second application 5 the proportions as mixed

were one bag (average 23,3 lb) of dry material to 10 gal

(83 lb) of water, the average wet density of the freshly

mixed material was ^8 Ib/ftOj and of the material after

having been sprayed 53 lb/ft3« No grounds were used as

a guide to thickness, but frequent checks were made with

a depth gage as the spraying and rodding progressed. The

application was completed to a uniform thickness of 1/2 in,

from the bottoms of the cells,

Approximately two weeks after the second application,

the surface of the acoustical plastic showed numerous

cracks, some of which were filled. Also, the thickness

of material, as Indicated by probing, varied from 1/h

to 3/^ in, below the cells. Additional material was applied

to an area of several square feet near the beam to Increase

the thickness to 1/2 in. Measurements at twelve points,

made the day before test, which was 29 days after the patching of cracks and addition of material, indicated that the

thickness ranged from 3/8- to 9/18- in, below the cells,

with the average essentially 1/2 in.

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-II9, One exception to this involved the placement

of thermocouples to indicate furnace temperatures. This

exception, and its significance, will be discussed in

later portions of this report.
” 5

”

3»1 Furnace

The furnace was in the shape of a large 5 fire-brick

lined box with the specimen filling the otherwise open

topo The furnace was equipped with steel frame to support

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

loading apparatus, m.eans for measuring deflections, and

windows through which the exposed surface could be observed

during the testa

3s2 Aging

The specimen was allowed to age 30 days from the day

the last material had been applied® The period of aging

was determined by periodic weighing of a representative

sample of the constructions Aging was continued until the

sample's weight was essentially constant for five

consecutive dayse

3a3 Loading

The dead load or weight of the specimen was Ib/ft^

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/36O of the span of the cellular

units was IO8 Ib/ft^^ The design load for the 8WF24 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 Ib/lin ft were placed on the floor above the beam

to bring the beam load ups

3a^^ Temperatures

Temperatures were measured by means of ehromel-aJ-umel

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 5 the others

were in glass fiber sleeving* The thermocouple locations

are indicated in figure 1* The furnace fires were controlle d

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, 18^0° F at 2 hr, 2000° F at h hr

and 2300° F at 8 hr*
6-^

Because the thickness of the deck units was small compared to the depths of joists usually employed in floors,

the bottom surface of the specimen was several inches

farther than usual from the floor of the furnace chamber.

Eight of the twelve furnace thermocouple pipes were placed

through fixed openings in the furnace walls. The highest

of these openings were so located that the eight thermocouple junctions were about l6- to 17“in. below the specimen,

rather than the 12 in. specified in the method o The other

four junctions were 12 in. below the specimen. It was

felt that this misplacement of thermocouples would have no

significant effect because the lai^ge volume of gas-and-air

delivered at high velocity from the l8 burners produced

high turbulence. The resultant mixing was believed to be

such that the average of the tempera-tures at the actual

thermocouple locations would be the same as, or not

signif icantly different from, that at the specified

locations

Measurements of temperatures at both sets of thermocouple locations were made in a subsequent test to provide

an indication of the validity of this assumption. The

findings of those measurements will be discussed in later

sections of this report, with the results of this test.

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

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

if any, of the furnace temperatures from those defined.

Results

The fire test was conducted March 1H-, 1957. The

observations of deflections, physical behavior, and temperatures are reported together although each was made
independently of the other So All times are from the start

of the fire exposure At 7 min? a crack in the unexpcsed

concrete surface extended completely across the specimeno

It was located ahore the steel beam® At 20 min a horizontal crack 3 to ^ ft long was observed near the East

end and about 2 in® from, the bottom of the North face of

the beam protect Ion® By 28 min t,his crack extended the

full length of the beam and there was a vertical crack

2 to h ft from each end of the beamo By 1 hir 12 min similar

cracks had developed in the South face of the beam protection®

The deflection at the center of the beam was 0<,2 in® ^ the

maximum beam temperature was 250° F^, and the max.imum

temperature on the unexposed surface was 1^0 degrees F

above the initial value® By 1 hr 51 min additional cracks

had developed 9 Including two across the beam soffit® At

2 .hr 17 m.in some cracks were 1/h- In® wide and a small

section of plaster about 10 in® long by 2 in® wide fell

from the beam soffit® The deflection at the center of the

beam was 0®8 in® ^ the maximum beam temperature was 826°F,

and the average temperature on the unexposed surfa.ce was

215 degrees F above the initial value® At 2 hr h2 min,, the

average temperature on the unexposed surface reanhed the

limiting rise of 250 degrees F® The one-point rise of

325 degrees F was reached at 2 hr ^5 min^ by which time

several cracks in the beam protection were 1/2 in® wide

and three pieces of plaster had faJi.len from the edges of

the beam protection® The deflection at the center of the

beam was 1®2 in® and the maximum beam, temperature was

1005° Fo At 3 hr 6 miUj an average temperature of 1000°F

was reached at one group of thermocouples on the steel

beam® By ^ .hours 5 several cracks in the beam protection

were 1/2 to 1 in® wide and the deflection of the center

of the beam was 3ol in® By 5 hr 12 minj lath and plaster

had fallen to expose about 1 1/2 ft length of the bottom

flange of the beam® T.he load was removed and the gas shut

off at 5 hr 23 min® The deflection at the center of the

beam was 8®in® 5 the tem.peratures at the 2h thermocouples

on the beam ranged from. 124'5°F to 1915°

5 and the temperatures on the unexposed surfa.ce ranged from 604 to 8OI

degrees F above their Initial values®

After cooling 5 the a.coustieal plastic on the bottom

surface of the steel deck was shrunken^, covered with

cracks or fissures up to 1 in® wide® and its surface was

dark and glossy® However 9 none of the plastic had faJ.len

from place® The bottom flange of t.he beam was exposed
along the center half of its lengths There were two long

cracks in the concrete slab. The steel deck was bowed

and most of the welds between the deck and beam were broken^

The concrete and steel deck were still in close contact

and the joints between cellular units were closedo The

beam was bowed to a permanent deformation of 8 ^/l6 in. at

the center.

4.1 Procedures to Determine Effect of

Furnace Thermocouple Placement

As previously mentioned in section SA of this report,

the eight furnace thermocouple junctions mounted in iron

pipes through fixed openings in the furnace walls were

located ^ to 5 in. farther from the test specimen than the

start“Of “test position defined in ASTM E-=1198 It was felt

that the mixing of hot gases in the furnace chamber was such

that no significant error would be Introduced in the fire

exposure to the specimen. However, after the test, persons

interested in the results questioned the validity of this

assumption. Consequently, procedures designed to provide an

Indication of the effect, and its magnitude, were carried

out during the next test in the floor furnace.

In the later test, furnace thermocouples were mounted

in the same positions relative to the specimen as in the

test reported herein, that is, four along a central pier

were 12 in, below the specimen and eight through the furnace

walls at l6 to 17 in. below the specimen, all in iron pipes.

No attempt was made to prevent sag of the approximately

horizintal pipes through the furnace walls. Eight addltional thermocouples, in iron pipes, were placed thnough

extra holes drilled in the furnace walls so that the

thermocouple junctions were 12 in. below the specimen. The

iron pipes for the latter thermocouples were supported

by nichrome wire in an attempt to prevent, or minimize,

sag as these pipes were heated, although this is not

required directly or by implication in the Standard Test

Method E“119.

The furnace fires were controlled to provide the

temperatures of the standard time-temperature curve as

indicated by the average of the 12 thermocouples located
-9-

12 in« from the specimen at the start of the test* After

6 hours fire exposure, the comhined effects of the sag of

the specimen plus the limited sag of the eight supported

thermocouple pipes through the furnace walls resulted in

the thermocouple junctions within the latter being from

12 to l4 Ino from the specimen surface « The eight

unsupported pipes were deformed so that the thermocouple

junctions were from 20 to 3^ 1/2 ln<» from the specimen

surfaces

To permit evaluation of the effect of thermocouple

placement, the temperatures observed were averaged in

two groups: A, those originally 12 in® below the specimen

including eight through the walls and four from the central

pier 5 B, the eight, through the furnace walls, originally

16 to 17 Ine below the specimen plus the four from the

central pier*

The average temperature of Group A was consistently,

but only slightly, lower than that of Group Bo The difference

vamied from about 1 degree F to l6 degrees F® The maximum

difference was observed at 15 min, and the difference

decreased steadily thereafter o The individual differences

were summed over the time corresponding to the duration,

of the test reported herein, for which the correction was

computed® This sum was applied to the furnace temperature

data put into the formuj-a® The resulting correction

obtained from the formula differed by only 0*8 min from

that obtained using the original data® This difference,

which would have decreased the original correction,

was not considered significanto

4o2 Fire Endurance Limit

The fire endurance of the specimen was limited by

temperature rise on the unexposed surface at 2 hr *+2

mirio The fire exposure severity was lOlol percent up to

this time and 100e4 percent over the entire 5 hj? 23 min

durations The correction to the fire endurance limit, as

computed by the formula given in ASTM E-119 and based on

the data from the test reported herein, was plus 1 min®

Therefore, the corrected fire endurance of the specimen

tested was 2 hr ^3 mino
5o Summary

The results of this test indicated a fire endurance

of 2 hr ^-3 min for the particular specimen tested, as

determined by temperature rise on the unexposed surface*

The beam continued to support the applied load for over

5 hours although the steel reached temperatures at just

over 3 hours that would have constituted failure of a

beam tested without load*

The determination of the effect of furnace thermocouple location, actually carried out during a subsequent

test but applied to the results of the test reported herein,

indicated that this effect was small enough that no correction

was made*
>

do‘3dniVd3dl/^3i

Fig. 2. Shrinkage cracks one week after Initial application

of acoustical plastic to fill between-cell spaces.

Fig. 3. Condition of exposed surface after fire exposure and cooling.

Fig. 4-. Condition of unexposed surface after cooling and removal of loading apparatus.

u. s depaktmp:nt of commerce

Sincluir Wet-ks, 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, an«l engineering in the field indicated by its title, A brief

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

inside front cover of this report,

W ASHINGTON, D. C.

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

Electrochemistry.

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

Technology, Length. Engineering Metrology.

Heat and Power. Temperature Physics. Thermodynamics. Cryogenic Physics. Rheology

and Lubrication. Engine Fuels.

Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry, Solid State Physics. Electron Physics. Atomic Physics. Nuclear Physics. Radioactivity, X-rays. Betatron. Nucleonic Instrumentation, Radiological Equipment. AEC Radiation Instruments. Chemistry. Organic Coatings. Surface Chemistry. Organic Chemistry. Analytical Chemistry.

Inorganic t^ilvemistry. Electrodeposition. Gas Chemistry. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances.

Mechanics. Sound. Mechanical Instruments. Fluid Mechanics, Engineering Mechanics.

Mass and Scale. Capacity. Density, and Fluid Meters. Combustion Controls,

Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifications. Polymer Structure Organic Plastics. Dental Research.

Metallurgy. Thermal Metallurgy, (!!hemical Metallurgy. Mechanical Metallurgy. Corrosion.

Metal Physics

Mineral Products. Engineering Ceramics. Glass. Refractories. Enameled Metals. Concreting

Materials. Constitution and Microstructure

Building Technology. Structural Engineering. Fire Protection. Heating and Air Condi

tioning. Floor, Roof, and Wall Coverings, Codes and Specifications.

Applied Mathematics. Numerical Analysis, (^Computation. Statistical Engineering. Mathematical PhysicsData Processing Systems, SEAC Engineering Group. (Components and Techniques. Digital

Circuitry . Digital Systems. Analogue Systems. Application Engineering.

• Office of Basic Instrumentation • (Office of Weights and Measure.- BOULDER, COLORADO

Cryogenic Engineering, (.ryogenic Equipment. Cryogenic Processes. IVoperties of Material.-

Gas Liquefaction.

Radio Propagation Physics. Upper At’Tiosphere Researeli. lonosphern Reseandi. Regular

Propagation Services Sun-Earth Ht lalionslups.

Radio Propagation Engineering. Data Reduction Instrumentation. Moiiuialion Nysleius

Nnvjgation Systems Hatlio Noise I’ropospherie Measurements. 'i'ro|)ospherir Analysis. K.idio

Sys«' nis Applieation Engineering.

Radio Standards. Radio Frequoneics Microwave Frequencies. High hrequciuy Eleelrical

Siimlards. Radio Broadcast .'service High Frequency Impedance Stamlards. (.alihratioa

renter Microwave Physics. Microwave Circuit ''itaiidardB.