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STANDARDS REPORT

9395

. REPORT OF FIRE TESTS ON TWO SCR BRICK WALL COLUMNS

by

J . V . Ryan

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

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standards of measurement, and the provisions of means for making measurements consistent with

those standards; determination of phvsical constants and properties of materials; development of methods for testing materials, mechanisms, and structures, and making such tests as may be necessary, particularly for government agencies; cooperation in the establishment of standard practices

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activities is suggested in the following listing of its three Institutes and their organizational units. Institute for Basic Standards. Applied Mathematics. Electricity. Metrology. Mechanics. Heat. Atomic Physics. Physical Chemistry. Laboratory Astrophysics.* Radiation Physics. Radio Standards

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

421-2104 September 9, 1966 9395

REPORT OF FIRE TESTS ON TWO SCR BRICK WALL COLUMNS

by

J. V. Ryan

NATIONAL BUREAU OF STA

for use within the Government. E and review. For this reason, the whole or in part, is not authoriz Bureau of Standards, Washington

the Report has been specifically p

IMPORTANT NOTICE Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

accounting documents intended

ibjected to additional evaluation

isting of this Report, either in Office of the Director, National

the Government agency for which

lies for its own use. <NBS>

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

REPORT OF FIRE TESTS ON TWO SCR BRICK WALL COLUMNS

by

J . V . Ryan

ABSTRACT

Two brick wall -columns were subjected to fire tests,

under applied loads, in cooperation with the Structural Clay Products Research Associateship . The two

specimens were nominally identical, except as to age.

The first was tested to failure under load, which

occurred at 2 hours 54 minutes. The fire exposure

in the second test was stopped after 2 hours but the

load maintained. The intention was to load the

specimen to failure after cooling. However, it collapsed about 1 3/4 hours after the fires were shut off.

1. INTRODUCTION

Since the establishment of the Structural Clay Products Research Associateship at the National Bureau of Standards, part of their research has been

on the effects of fire exposure on brick and brick masonry. This is the

report of two full scale fire tests of brick wall columns. The first

specimen was tested under an applied load computed by recognized design

formulas and using strength data obtained with small wallettes. The

second was tested under the same load but the fire exposure was stopped

at a predetermined time, well short of the failure time observed in the

first test. It was planned that the second specimen would be allowed to

cool naturally to room temperature, that it would be instrumented, and

the load increased until structural failure. The cooling was expected to

take most of a day, with another day possibly for instrumentation.

2. SPECIMENS

Both specimens were built, on successive days, by the same experienced

brick mason, using materials from the same sources and lots. The speci- mens were conditioned in the same room but to different ages. The room was not equipped to provide controlled temperature and humidity. Table 1 gives data on the bricks, which are illustrated in Figure 1.
Table 1. Brick Data

Length, inches

Width, inches

Height, inches

Solid, percent

Weight, lbs.

Modulus of rupture, psi

Compressive strength, psi 10460

11 .52

5.48

2.25

85

9.9

619

Each brick column was one brick thick by two bricks long by 60 courses high.

With mortar joints, the columns were 23 1/2 inches long and 13 feet 2 inches

high. The brick were laid in a common running bond pattern, so that every

other course consisted of two full bricks, and the other courses of one

full brick between two half bricks. The cut ends of the halves were turned

in. A specimen is shown, in the furnace, in Figure 2. One long face was well aligned; the other face showed the random variation in brick widths.

The mortar was Type S, mixed 1: 1/2:4 1/2 by volume (1:0.27:3.93 by weight)

of cement: lime: sand . The average compressive strength of three 2-inch

cubes was 1720 psi, measured on the day of the first fire test. The

average compressive of three 5 1/2 by 11 3/8 by 12 1/2 inch masonry

prisms was 5810 psi; the average modulus of elasticity was 3,080,000 psi.

The quality of workmanship was excellent.

As the specimens were being fabricated, four thermocouples (22 gage chromelalumel) and two brass tubes were built into each. The thermocouple junctions

were located one each at the bottom, and 2 feet 6 inches, 5 feet, and 7 feet

6 inches above the bottom; each at the center of the cross-section of the

specimen. The brass tubes were placed at the midthickness and extended in

6 inches from one of the narrow faces. For specimen 1, the tubes were

6 feet 6 inches and 12 feet 6 inches above the bottom; for specimen 2 they were 4 fqet 3 inches and 8 feet 1 inch above the bottom. The brass tubes

served as cavities into which relative humidity sensors were placed to

measure the relative humidity of the entrapped air. Data were obtained

frequently from each of the four cavities. The values of all four were quite

similar. Figure 3 shows the values for two, one in each specimen.

In addition to the insertion of the two humidity gage cavities in mortar

joints, three mortar samples were made up for each wall column by filling

6 inch long pieces of 1 inch ID tubing. These samples were kept with the

wall- column and were weighed frequently. Representative weight loss data are shown in Figure 4. Also, six wallettes were made 11 1/2 by 12 1/2 by

5 1/2 inches. All but the two 11 1/2 by 12 1/2 inch faces were sealed, with

bituminous paint, to simulate the drying conditions in the fire test specimens.

These walletes were weighed frequently. The data shown in Figure 4A, were

similar to those for the mortar cores, whown in Figure 4, further confirming the

fact that the specimens had not reached an equilibrium moisture content.

Both specimens were fabricated during the first week in April and were

conditioned in a room maintained suitable for work but not controlled to

specific temperature or humidity. Specimen 1 was tested at age of 42

days; Specimen 2 at age of 75 days.
-3-

3. TEST METHOD

Each specimen was placed in a furnace specifically designed for fire

endurance testing of columns, with or without applied load. The specimen's

orientation was such that its wide faces were to the North and South. Of

the 13 feet 2 inches overall height, the top 2 feet 8 inches was in or above the top closure to the furnace chamber. The bottom 3 inches was sur- rounded by loose insulation. '

Each test was instrumented for measurement of applied load, lateral deflection, vertical expansion and contraction under the combined effects of heat and

load, and for temperatures in the specimen and in the furnace. The latter

measurements were made with 18 gage chromel-alumel thermocouples run through

porcelain spacers and encased in sealed iron tubes.

Each specimen was subjected to an applied load of 56,300 lbs., computed by

the SCPI Research Associate, on the basis of 13 feet 2 inches height. This

load corresponds to a stress of 435 psi, the allowable stress for f 'm of

4470 psi and slenderness ratio of 29. It was learned just before the second

test that he was not aware that the top closure of the furnace chamber was firm enough and in good enough contact with the specimen to constitute

lateral bracing. The same load was used in the second test in order to be

consistent. The lateral bracing effect of the closure is applicable to all

columns tested under load in this furnace. The load was applied, through a spherical bearing block, from a hydraulic jack beneath the furnace chamber.

Each specimen was subjected to fires controlled to produce, as closely as practicable, the temperatures of the standard time- temperature curve defined in Standard Method for Fire Tests of Building Construction and

Materials,. ASTM E119, which include: 538 C (1000 F) at 5 min., 704 C

(1300 F) at 10 min., 843 C (1550 F) at 30 min., 927 C (1700 F) at 1 hour,

1010 C (1850 F) at 2 hours, and 1052 C (1925 F) at 3 hours. The sole

criterion, in the Standard Test Method, for loaded columns is the ability

to sustain the applied load.

4. TEST RESULTS

The orientation of each specimen in the furnace was such that its narrow

faces were to the East and West, its wide faces to the North and South.

Reference, in the observations and results, to the faces will be on that

basis. Measurements of transverse deflection were in the North-South

directions

.

4.1 Specimen 1.

The test was conducted May 17, 1966. The specimen exhibited a length re- duction of 0.121 inch as a result of the application of load, just before
-4-

the start of the fire exposure. Short vertical cracks appeared within

2 inches of the specimen corners in the first 20 minutes. A few cracks

4 inches and more from corners appeared at about 30 minutes. There was little change until after 1 hour 20 minutes; between then and 2 hours,

several vertical cracks appeared on the North and South faces and a few

grew to full height of the specimen. All remained 1/16 inch or less,

in width. By 2 hours 9 minutes there were cracks at 3 to 4 inches spacing

completely across the South face; they were all less than 1/16 inch wide.

At 2 hours 47 minutes a few cracks were judged to be 1/8 inch wide.

At about 2 hours 51 minutes a slight bow toward the North appeared in the

specimen which became pronounced by 2 hours 52 minutes. The specimen

collapsed at 2 hours 52 1/2 minutes.

The specimen expanded rapidly early in the test, reaching approximately

half its total expansion in the first 20 minutes. The overall length

change began decreasing at about 2 hours, and became negative about 4

minutes before collapse. The data are plotted in Figure 5. The design

of the transverse deflection measurement system had not anticipated all

possible problems; it jammed very early in the test and meaningful data

were not obtained.

After the test, the specimen was a somewhat ordered pile of debris. It

had folded and laid back on itself, so that about half the remains were neatly aligned. The rest were in a random jumble. The cracks observed

during the fire exposure had become complete breaks. The broken bricks are shown in Figure 6.

The time-temperature data are plotted in Figure 7. The severity of the

fire exposure was 101.5 percent of standard. A correction of plus 1 minute was applicable due to deviation of the actual furnace temperatures

from the Standard Time-Temperature Curve. The results of the test indicated that the fire endurance of the particular specimen tested was

2 hours 54 minutes, as determined by load failure.

4.2 Specimen 2

The test was conducted June 20, 1966. The specimen exhibited a length

reduction of 0.195 inch as a result of the application of load one hour

before the start of the fire exposure. Short vertical cracks appeared

within 2 inches of the specimen's corners in the first 20 minutes. By

50 minutes there were a few cracks 4 inches from the corners and extending

vertically through two to seven courses of brick. By 1 hour 32 minutes

four cracks (one each 4 inches from each side of the North and South faces)

extended essentially the full exposed height of the specimen, but were less

than 1/16 inch wide. The furnace fires were turned off at 2 hours, but the

load was maintained. The furnace door was kept closed.
-5-

The specimen expanded rapidly early in the test, reaching approximately half

its total expansion in the first 20 minutes. The maximum overall expansion

was reached at 1 hour 54 minutes. A gradual reduction in length took place,

under continued loading, as the specimen cooled. Between 2 hours 30 minutes

and 2 hours 40 minutes, the rate of shrinkage increased and the specimen collapsed at 2 hours 43 1/2 minutes. The last reading, 1/2 minute before collapse,

indicated that the specimen still had nearly half its maximum expansion. The

data are plotted in Figure 5. The specimen deflected .02 inch to the North

under load application. This increased to approximately .12 inch at 15

minutes but decreased .04 by 35 minutes. Very little change was observed

after that time. However, it is doubtful that the readings had much meaning

beyond 35 minutes, due to high temperature effects on the measurement system.

After the collapse, a pier about 6 feet high remained. It was badly cracked

and retained the original width only for the bottom 3 courses of brick. It was about half the original width for most of its height but only a few

inches for the top two courses.

The severity of the fire exposure for the two hours was 101.2 percent.

Since the fire test was not carried to failure, the ultimate fire endurance

cannot be stated for the specimen. However, the fire endurance of 2 hours was exhibited, and very probably fire endurance of the same order of magnitude as that of specimen 1 would have been exhibited had the fire exposure

been continued. The time- temperature data are plotted in Figure 8.

5 . SUMMARY

Two brick wall columns were subjected to fire exposure and applied load

in accordance with the standard test method. The first test was continued

to the applicable end point, load failure, and the particular specimen

exhibited fire endurance of 2 hours 54 minutes. The fire test of the sec- ong specimen was stopped at 2 hours with the intention of measuring the

specimen’s modulus of elasticity and ultimate strength after cooling. The

load applied throughout the fire exposure was maintained during the cooling.

However, the specimen collapsed approximately 1 3/4 hours after the end of

the fire exposure.

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FIG. 7-TIME-TEMPERATURE DATA FOR TEST 450

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