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Technical Note (National Research Council of Canada. Division of Building Research), 1962-08-01

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Changes in Fire Test ASTM E119 Since 1918 and Comparison with BS

476Galbreath, M.

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DIVISION OF BUILDING RESEARCH

NATIONAL RESEARCH COUNCIL OF CANADA

']['ECIHIN][CAL NOTlE

No.

378

NOT FOR PUBLICATION

PREPARED BY M. Galbreath

PREPARED FOR Fire Test Board

FOR INTERNAL USE

CHECKED BY R. S. Ferguson APPROVED' BY NBH

DATE August 1962

SUBJECTCHANGES IN FIRE TEST ASTM El19 SINCE 1918

AND COMPARISON WITH BS 476

The fire testing of building assemblies by standardmethods of test has been progressing for over 40 years. Manychanges and refinements in the test methods have been intro­duced during this period. In order to assess the relevanceｯ ｾ recorded fire test data for use today, information isrequired on the Standard that applied when the tests weremade.

The Standards for fire endurance required by theNational Building Code are {l} The Standard Methods of FireTest of Building Constructions and Materials, ASTM El19-58 ofthe American Society for Testing and Materials and (2) TheFire Endurance Section of Fire Tests on Building Materialsand Structures, BS 476 1953 of the British StandardsInstitution.

ASTM El19, developed out of a program of firetesting at the University of Columbia, was adopted as atentative method in 1917 and as a Standard in 1918 by theAmerican Society for Testing and Materials. BS 476, the fireendurance section of which is similar in many respects toASTM El19, was adopted as a Standard by the British StandardsInstitution in 1933 and revised in 1953. Reports of teststo the ASTM Standard are in common use in Canada althoughthe British test is also accepted. The changes made in ASTMEl19 since it was first adopted as a Standard are summarizedbelow, and these are followed by a comparison of ASTM El19and BS 476.

, •- 2 -

CHANGES MADE IN ASTM El19 SINCE 1918

Test Methods of ,Particular Assemblies

The original Standard Test Methods included descrip­tions of the manner of test for building assemblies includingonly floors, roofs and non-load-bearing partitions.

The following is a list of the detailed methods oftest for assemblies, with the year in which they were intro­duced into the Standard:

Tests of floors and roofs 1918Tests on non-load-bearing partitions 1918Tests on load-bearing walls 1926Tests on columns 1926Tests on protection for combustible framing 1926Alternative test for column protection 1947Test for ceilings 1947Alternative test for protection of solid

structural steel beams and girders 1953

Factor of Safety

A factor of safety 1-1/4 times the period for whichclassification was desired remained in force from 1918 to1926. In 1926 it was dropped and in its place this generalstatement was included: "When a factor of safety exceedingthat inherent in the test conditions is desired a proportionalincrease should be made in the specified time classificationperiod."

Classification as "Combustible"

From 1926 to 1954 assemblies containing combustiblesin sufficient quantity, or arranged so as to continue burningafter the desired time period, were classified as combustible.This was dropped in 1954, and in 1955 a paragraph was includedreqUiring "that observations be made of significant detailsof the behaviour of the material or construction during thetest'and after, giving information on deformation, spalling,cracking, burning, continuance of flaming, and production ofsmoke."

Rating Period

From 1918 to 1950 classification was in terms of 4hours, 1/2 hour, etc. ａ ｦ ｴ ･ ｾ 1950 results are ｲ ･ ｰ Ｐ Ｑ ｾ ･ ､ in timeperiods of resistance to the nearest integral minute. Theremay be some discrepancy in that the introduction to the

- 3 -

Standard states that "The methods may be cited as StandardFire Tests and the performance or exposure shall be expressedas 2 hours, 6 hours, 1/2 hour, etc."

Hose Stream Test

The hose stream test was required for fire enduranceperiods over 1/2 hour ｢ ･ ｾ Ｏ ･ ･ ｮ 1918 and 1941. In 1941 thiswas changed; the hose stream test is now required only forperiods of over 1 hour. Exposure of a duplicate sample tothe furnace prior to the hose stream test was required for3/4 of its fire resistance period but not more than 1 hourbetween 1918 and 1926. In 1926 this was changed to 1/2 ofthe fire endurance period but not less than 1 hour, and hasbeen unchanged since.

The hose stream test was required for floors, roofpand load-bearing walls. Since 1954 the hose streanr tes·t 118.S beenrequired only for load-bearing walls. A clause permittingsamples smaller ｴ ｾ ｡ ｮ the Standard prescribed, if justified byconditions of use, was introduced in 1941.

ｾ ｯ ｡ ､ ｩ ｮ ｧ After Test

In Ｑ Ｙ Ｑ ｾ ｡ ｦ ｴ ･ ｲ the fire endurance test, a floor orroof was submitted to a superimposed load 2-1/2 times theload during the test. In 1926 this was changed to doublethe test load. In 1954 this requirement was deleted. Thehose stream test is now not required for floor and roof tests.

Load-bearing walls are exposed to the hose streamtest while carrying a superimposed load equal to the designload. After cooling, but within 72 hours the walls areSUbjected to a load equal to twice the superimposed load.

Temperature Rise Criterion

In 1918, a 3000 F rise in temperature of theunexposed surface of a partition was one criterion forfailure. No temperature rise was applied to floors androofs. The present standard of 250 0 F temperature rise abovethat at the start of the test was applied to partitions,walls, floors and roofs in 1926.

Control of Furnace Temperatures

There have been a number of changes in the controland recording of temperatures over the years, all tendingtoward greater accuracy in measurement. In 1918 only three

- 4

thermocouples were required to measure furnace temperature.In 1941 this was changed to five, and in 1950 to nine. In1918, readings ｯ ｾ temperature were taken every 5 minutesduring the first hour and every 15 minutes thereafter.Since 1950 readings have been taken every 5 minutes duringthe first 2 hours and every 10 minutes thereafter. Therelative accuracy measured by the area under the time­temperature curve between 1918 and 1941 was limited to a15 per cent error for fire endurance periods of 1 hour orless, within 10 per cent for 1 to 2 hours and within 5 .per cent for over 2 hours. In 1941 this was changed toacquire accuracy within 10 per cent for fire enduranceperiods of 1 hour or less, 7-1/2 per cent for 1 to 2 hoursand 5 per cent for over 2 hours.

Recording of Temperatures on Unexposed Face

Between 1918 and 1954 temperatures on the unexposedface of the sample assembly were measured by 5 thermometersor thermocouples, and since 1954 by 9 thermocouples. Thefrequency of temperature recordings has not changed since1926. Readings are taken at intervals not exceeding 15minutes until a reading exceeding 212°p has been obtained atanyone point. Thereafter readings may be taken more frequentlybut need not be less than every 5 minutes.

Conditioning of Specimen

In 1918 a floor or roof was to be tested as soonafter construction as desired but within 40 days. Artificialdrying was permitted but not required.

In 1926 the material or construction was requiredto have attained a large proportion of its final strengthand was not tested until excess free water had been givenoff. This would require about 30 days; where drying wouldnot be completed within 40 days by natural means,artificialdrying at air temperatures not exceeding 100°F was permitted.In 1933 the references to 40 days and to 10QoF were deleted,and "artificial drying at temperatures not injurious to thematerial" was substituted.

In 1953 it was stipulated that the material shouldbe weighed at intervals and that drying should continue untilthe weight remained fundamentally constant for 5 successivedays. If it is inconvenient to weigh the test assembly asample could be fabricated for this purpose.

In 1961 more restrictive clauses were introduced.The test specimen was to be exposed to air at a relativehumidity of 30 to 35 per cent and at a temperature of 70 to

- 5 -

80°F until the interior or dampest section of the assemblyattained 70 per cent relative humidity within a tolerance of+ 5 per cent. If a specimen, after exposure to the requiredconditions, has not attained 70 per cent relative humidityafter 12 months it may be considered suitable for testing.

The changes of greatest significance in assessingpast results are those that would tend to make the fireendurance by present test less than that by the older test.Amant these changes may be considered increasing requirementsfor accuracy in the recording and control of temperature, andin increasingly stringent requirements for conditioning ofthe test specimens.

COMPARISON OF BS 476 AND ASTM El19

The Standard for Fire Tests on Building Materialsand Structures, BS 476 of the British Standards Institution,was introduced in 1932 and revised in 1953. The Standardincludes methods of test for combustibility, surface spreadof flame and fire resistance of structures. Only the testfor fire resistance is required by the National Building Code.The fire resistance test, like ASTM El19, may be applied tothe testing of walls, floors, roofs, beams, columns, etc. TheBritish test may also be used for testing doors and shutters.

Control of Furnace Temperatures

The time-temperature curve is identical in bothASTM and BS tests up to 2 hours from the start. At 4 hoursthe British furnace is at a temperature of 2050 0 F while theａ ｓ ｾ ､ furnace is at 2000oF. The temperature at 6 hours inBS 476 is 2200 0 F and in ASTM El19 2l50oF. As fire enduranceratings of over 4 hours are not required by the National .Building Code, the difference in temperatures between thetwo methods is not very significant.

Six thermocouples are required to measure furnacetemperatures in the British test and nine in the ASTM test.The degree of accuracy measured as the permissible error inthe area under the time-temperature curve varies slightly.In the British test, the accuracy of the area under the time­temperature curve for tests in which the temperature rise onthe unexposed face is a factor is as follows:

1/2 hour fire endurance or less1/2 hour to 1 hour fire endurance1 hour to 2 hours fire enduranceOver 2 hours fire endurance

15 per cent10 per cent10 per cent

5 per cent

6 -

In the ａ ｓ ｾ ｾ test the accuracy required is:

1 hour or less fire endurance1 hour to 2 hours fire enduranceOver 2 hours fire endurance

10 per cent7 1/2 per cent

5 per cent

Reports of tests are stated to the nearest minute in theBritish test and grading is in periods of 1/2 hour, 1 hour,2 hours, 3 hours, 4 hours and 6 hours. The comparable sentencein ASTIi'I states "performance or exposure shall be expressedas 2 hours, 6 hours, 1/2 hour, etc."

Measuring Surface Temperatures

In the British test, surface temperatures aremeasured by means of thermocouples, each attached to theface of a I-in. diameter copper disc, secured to the surfaceof the element. The ASTM test method requires that tempera­tures be measured by thermocouples placed under flexible,dry, felted asbestos pads. This may lead to an increase inthe fire endurance rating by the British test.

Hose Stream Test

Since 1953 the British have not stipulated the useof the hose stream test. ASTM still retains it, but onlyfor load-bearing walls.

Loading After Test

The British test requires that the design load bere-applied 48 hours after the test on all load-bearingassemblies. The ASTM test applies twice the superimposedload on bearing walls only, within 72 hours after completionof the test.

Conditioning Specimen

The requirement for drying the specimen in BS 476is that the element be conditioned "to reproduce the state inwhich the element is likely to be when in service in thebuilding." ａ ｓ ｾ Ｑ Ｌ ｩ ｛ now has a very detailed specification fordrying to a controlled moisture content.

Size of Specimen

The minimum size of specimen in the British testis 10 by 10 ft or 10 ft in length for COlumns, beams, etc.

- 7 -

ASTM includes several dimensions for differing purposes:

e.g. 100 sq' ft for walls and partitions180 sq ft for ｾ ｬ ｯ ｯ ｲ ｳ Ｌ roofs, ceilings, etc.9-ft length for columnsl2-ft length for beams.

The significant variations in the two methods oftest are (I) the control of moisture content, (2) the relativeaccuracy of furnace temperatures, (3) the methods of measuringsurface temperatures, and (4) the differences in the superim­posed loads applied after test.

BIBLIOGRAPHY

American Society for Testing and Materials (1916 Race Street,Philadelphia)

Standard Specifications for Fire Tests of Materials andConstructions. ASTM C19-l8.

Tentative Specification for Fire Tests of Building Con­struction and Materials. ASTM C19-26T.

Standard Specifications for Fire Tests ｯ ｾ Building Con­struction and Materials. ASTM C19-33.

Standard Methods of Fire Tests of Building Constructionand Materials. ASTM C19-4l; El19-47; El19-50;El19-53; El19-54; El19-55; El19-58; El19-61.

British Standards Institution (2 Park Street, London)

British Standard Definitions for Fire-Resistance,Incombustibility and Non-Inflammability of BuildingMaterials and Structures (including methods of test).BS 476-1932.

British Standard Specification for Fire Tests on BuildingMaterials and Structures. BS ＴＷＶＭＱＹＵｾＮ (Sectionthree: Fire-Resistance Tests of Structures.)