Changes in Fire Test ASTM E119 Since 1918 and Comparison with BS 476

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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 476

Galbreath, M.

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DIVISION OF BUILDING RESEARCH

NATIONAL RESEARCH COUNCIL OF CANADA

']['ECIHI N][ CAL

NOTlE

No.

NOT FOR PUBLICATION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

SUBJECT

CHANGES IN FIRE TEST ASTM El19 SINCE 1918 AND COMPARISON WITH BS 476

The fire testing of building assemblies by standard

methods of test has been progressing for over 40 years. Many

changes and refinements in the test methods have been

intro-duced during this period. In order to assess the relevance

ｯｾ recorded fire test data for use today, information is

required on the Standard that applied when the tests were made.

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

Institution.

ASTM El19, developed out of a program of fire testing at the University of Columbia, was adopted as a

tentative method in 1917 and as a Standard in 1918 by the

American Society for Testing and Materials. BS 476, the fire

endurance section of which is similar in many respects to ASTM El19, was adopted as a Standard by the British Standards

Institution in 1933 and revised in 1953. Reports of tests

to the ASTM Standard are in common use in Canada although

the British test is also accepted. The changes made in ASTM

El19 since it was first adopted as a Standard are summarized below, and these are followed by a comparison of ASTM El19 and BS 476.

,

•

2

-CHANGES MADE IN ASTM El19 SINCE 1918 Test Methods of ,Particular Assemblies

The original Standard Test Methods included descrip-tions of the manner of test for building assemblies including only floors, roofs and non-load-bearing partitions.

The following is a list of the detailed methods of test for assemblies, with the year in which they were intro-duced into the Standard:

Tests of floors and roofs 1918

Tests on non-load-bearing partitions 1918

Tests on load-bearing walls 1926

Tests on columns 1926

Tests on protection for combustible framing 1926

Alternative test for column protection 1947

Test for ceilings 1947

Alternative 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 which classification was desired remained in force from 1918 to

1926. In 1926 it was dropped and in its place this general

statement was included: "When a factor of safety exceeding that inherent in the test conditions is desired a proportional increase should be made in the specified time classification period."

Classification as "Combustible"

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

Rating Period

From 1918 to 1950 classification was in terms of 4

hours, 1/2 hour, etc. ａｦｴ･ｾ 1950 results are ｲ･ｰＰＱｾ･､ in time

periods of resistance to the nearest integral minute. There

3

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

Hose Stream Test

The hose stream test was required for fire endurance

periods over 1/2 hour ｢･ｾＯ･･ｮ 1918 and 1941. In 1941 this

was changed; the hose stream test is now required only for

periods of over 1 hour. Exposure of a duplicate sample to

the furnace prior to the hose stream test was required for 3/4 of its fire resistance period but not more than 1 hour

between 1918 and 1926. In 1926 this was changed to 1/2 of

the fire endurance period but not less than 1 hour, and has been unchanged since.

The hose stream test was required for floors, roofp

and load-bearing walls. Since 1954 the hose streanr

tes·t

required only for load-bearing walls. A clause permitting

samples smaller ｴｾ｡ｮ the Standard prescribed, if justified by

conditions of use, was introduced in 1941. ｾｯ｡､ｩｮｧ After Test

In ＱＹＱｾ｡ｦｴ･ｲ the fire endurance test, a floor or roof was submitted to a superimposed load 2-1/2 times the

load during the test. In 1926 this was changed to double

the test load. In 1954 this requirement was deleted. The

hose stream test is now not required for floor and roof tests. Load-bearing walls are exposed to the hose stream test while carrying a superimposed load equal to the design

load. After cooling, but within 72 hours the walls are

SUbjected to a load equal to twice the superimposed load. Temperature Rise Criterion

In 1918, a 3000_{F rise in temperature of the}

unexposed surface of a partition was one criterion for

failure. No temperature rise was applied to floors and

roofs. The present standard of 2500_{F temperature rise above}

that 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 control

and recording of temperatures over the years, all tending

- 4

thermocouples were required to measure furnace temperature.

In 1941 this was changed to five, and in 1950 to nine. In

1918, readings ｯｾ temperature were taken every 5 minutes

during the first hour and every 15 minutes thereafter.

Since 1950 readings have been taken every 5 minutes during

the first 2 hours and every 10 minutes thereafter. The

relative accuracy measured by the area under the

time-temperature curve between 1918 and 1941 was limited to a

15 per cent error for fire endurance periods of 1 hour or

less, within 10 per cent for 1 to 2 hours and within 5 .

per cent for over 2 hours. In 1941 this was changed to

acquire accuracy within 10 per cent for fire endurance

periods of 1 hour or less, 7-1/2 per cent for 1 to 2 hours

and

5

Recording of Temperatures on Unexposed Face

Between 1918 and 1954 temperatures on the unexposed

face of the sample assembly were measured by 5 thermometers

or thermocouples, and since 1954 by 9 thermocouples. The

frequency of temperature recordings has not changed since

1926. Readings are taken at intervals not exceeding 15

minutes until a reading exceeding 212°p has been obtained at

anyone point. Thereafter readings may be taken more frequently

but need not be less than every

5

Conditioning of Specimen

In 1918 a floor or roof was to be tested as soon

after construction as desired but within 40 days. Artificial

drying was permitted but not required.

In 1926 the material or construction was required

to have attained a large proportion of its final strength and was not tested until excess free water had been given

off. This would require about 30 days; where drying would

not be completed within 40 days by natural means,artificial

drying 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 the material" was substituted.

In 1953 it was stipulated that the material should

be weighed at intervals and that drying should continue until

the weight remained fundamentally constant for

5

days. If it is inconvenient to weigh the test assembly a

sample could be fabricated for this purpose.

In 1961 more restrictive clauses were introduced.

The test specimen was to be exposed to air at a relative

5

-80°F until the interior or dampest section of the assembly attained 70 per cent relative humidity within a tolerance of

+ 5 per cent. If a specimen, after exposure to the required

conditions, has not attained 70 per cent relative humidity after 12 months it may be considered suitable for testing.

The changes of greatest significance in assessing past results are those that would tend to make the fire endurance by present test less than that by the older test. Amant these changes may be considered increasing requirements for accuracy in the recording and control of temperature, and

in increasingly stringent requirements for conditioning of

the test specimens.

COMPARISON OF BS 476 AND ASTM El19

The Standard for Fire Tests on Building Materials and Structures, BS 476 of the British Standards Institution,

was introduced in 1932 and revised in 1953. The Standard

includes methods of test for combustibility, surface spread

of flame and fire resistance of structures. Only the test

for fire resistance is required by the National Building Code. The fire resistance test, like ASTM El19, may be applied to

the testing of walls, floors, roofs, beams, columns, etc. The

British test may also be used for testing doors and shutters. Control of Furnace Temperatures

The time-temperature curve is identical in both

ASTM and BS tests up to 2 hours from the start. At 4 hours

the British furnace is at a temperature of 20500_{F while the}

ａｓｾ､ furnace is at 2000oF. The temperature at 6 hours in

BS 476 is 22000_{F and in ASTM El19 2l50}o_{F. As fire endurance}

ratings of over 4 hours are not required by the National .

Building Code, the difference in temperatures between the two methods is not very significant.

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

1/2 hour fire endurance or less 1/2 hour to 1 hour fire endurance 1 hour to 2 hours fire endurance Over 2 hours fire endurance

15 per cent 10 per cent 10 per cent 5 per cent

6

-In the ａｓｾｾ test the accuracy required is:

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

Over 2 hours fire endurance

10 per cent 7 1/2 per cent

5

Reports of tests are stated to the nearest minute in the British test and grading is in periods of 1/2 hour, 1 hour,

2 hours, 3 hours, 4 hours and 6 hours. The comparable sentence

in ASTIi'I states "performance or exposure shall be expressed as 2 hours, 6 hours, 1/2 hour, etc."

Measuring Surface Temperatures

In the British test, surface temperatures are measured by means of thermocouples, each attached to the face of a I-in. diameter copper disc, secured to the surface

of the element. The ASTM test method requires that

tempera-tures be measured by thermocouples placed under flexible,

dry, felted asbestos pads. This may lead to an increase in

the fire endurance rating by the British test. Hose Stream Test

Since 1953 the British have not stipulated the use

of the hose stream test. ASTM still retains it, but only

for load-bearing walls. Loading After Test

The British test requires that the design load be re-applied 48 hours after the test on all load-bearing

assemblies. The ASTM test applies twice the superimposed

load on bearing walls only, within 72 hours after completion of the test.

Conditioning Specimen

The requirement for drying the specimen in BS

476

is that the element be conditioned "to reproduce the state in which the element is likely to be when in service in the

building." ａｓｾＱＬｩ｛ now has a very detailed specification for

drying to a controlled moisture content. Size of Specimen

The minimum size of specimen in the British test is 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 partitions

180 sq ft for ｾｬｯｯｲｳＬ roofs, ceilings, etc.

9-ft length for columns l2-ft length for beams.

The significant variations in the two methods of test are (I) the control of moisture content, (2) the relative accuracy of furnace temperatures, (3) the methods of measuring surface temperatures, and (4) the differences in the superim-posed loads applied after test.

BIBLIOGRAPHY

American Society for Testing and Materials (1916 Race Street, Philadelphia) Standard Specifications for Fire Tests of Materials and

Constructions. ASTM C19-l8.

Tentative Specification for Fire Tests of Building

Con-struction and Materials. ASTM C19-26T.

Standard Specifications for Fire Tests ｯｾ Building

Con-struction and Materials. ASTM C19-33.

Standard Methods of Fire Tests of Building Construction

and 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 Building Materials and Structures (including methods of test). BS 476-1932.

British Standard Specification for Fire Tests on Building

Materials and Structures. BS ＴＷＶＭＱＹＵｾＮ (Section