NATIONAL BUREAU OF STANDARDS REPORT

4813

Effect of Type and Arrangement of

Cellular Blocks on Strength of Prestressed Assemblies

by

M. Chi and D. Watstein

Report to

Bureau of Yards and Docks

Department of the Navy

<J0>>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary NATIONAL BUREAU OF STANDARDS

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

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1001-10-4811 August 10, 1956 4813

Effect of Type and Arrangement of

Cellular Blocks on Strength of Prestressed Assemblies

by

M. Chi and D 0 Watstein

To

Bureau of Yards and Docks

Department of the Navy

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, 1

unless permission

25, D.C. Such p>

cal ly prepared If

Approved for public release by the tr in part, is prohibited Director of the National Institute of standards, Washington Standards and Technology (NIST)

on October 9, 2015.

eport has been speclfireport for its own use.

Effect of Type and Arrangement of

Cellular Blocks on Strength of Prestressed Assemblies

by

M. Chi and D. Watstein

Abstract

Investigation was made of the mechanism

of failure of two-way prestressed slabs

made of cellular concrete blocks. Small

columns, beams and slabs were studied

and cracks in webs of blocks due to prestress were discovered. Reinforcement

was found to be very effective both in

minimizing the extent of these cracks and

in increasing the strength of the assemblies; the shape of holes was found to

have no effect on the occurrence of these

chacks. The suitability of different

types of blocks for use In a two-way prestressed slab can be predicted with this

method of testing.

1. INTRODUCTION

In the continuing study of the properties of the two-way

prestressed cellular slabs, several slabs composed of 6-in.

cellular blocks were tested. The results of the tests of

slabs Nos. 1 through 4 composed of cells procured by Preload

Corporation, were reported in NBS Report 4396. As will be

described in detail in a forthcoming report on some of the

other slabs tested, the specimens consisting of high-strength,

precision cellular blocks having no reinforcement failed under

smaller load than those of inferior but reinforced blocks;

these slabs exhibited distinctly different crack patterns.

T/Jhile this finding has confirmed the Conclusion 3 in NBS Report

4396, further tests were deemed necessary to study the cause

and mechanism of premature failure in slabs containing unreinforced blocks. It is for this purpose that the Structural

Engineering Section initiated the auxiliary series of tests

of small columns, beams and slabs described in this report.

2. DESCRIPTION OP TEST SPECIMENS

2.1 Cellular blocks

The following different types of cellular blocks were

used in this test series, (see Pigure 1):

Type UE - 6 in. unreinforced cells having an

opening 41/2 in. square in cross

section, with one 1- by 2-in.

elliptical hole in each web.

Type UR - Same as Type UE except that it has

1-in. round holes instead of elliptical hole in each web; unreinforced.

Type UN - Same as Type UE except thar it has no

holes in the webs; unreinforced.

Type PE - Identical with Type UE except that it

is reinforced with 1- by 1-in. 15/15

welded wire fabric.

Type SE - Identical with Type UE except that it

is reinforced with stirrups of No. 4

gage mild steel wire, one in each web.

All blocks were made of mortar containing a concrete

sand; the proportions of the mortar were 1“3> by weight, and

the water-cement ratio was 0.57* Type I cement with 2 percent

calcium chloride was used for Type UN block and Type III

cement for all other types. It was assumed that the compressive strength of the mortar was essentially the same for all

blocks under similar curing conditions in spite of the difference in cement types. The compressive strength of 2-in.

cubes of a typical mix, after seven days of moist curing was

6200 psi. Young’s modulus ranged from 3«5> to 4«5 x 10° psi

with an average about 4 x 10° psi. Ail blocks were precision

made, had excellent texture and were virtually free of

shrinkage cracks. All blocks were at least six months old

when incorporated into test specimens, except for blocks of

Type UR which were about one month old.

2 .

2.2 Prestressing steel

The prestressing units in the test beams were 5/8 in.

"Stressteel" bars. The anchorage of these bars consisted of

hexagonal nuts, 1 l/4 in. long, which bore on 5 3/4- by 4 3/4“

by 3/4“in « anchor plates. The tensile strength of unthreaded

Stressteel bars was found to be 163,000 psi, whereas threaded

bars supported by fully tightened nuts developed a tensile

strength of 152,000 psi. The yield strength of the steel,

determined by the "offset” method (offset = 0.2/) was 142,000

psi. The stress- strain characteristics was a straight line

up to 65,000 psi, giving a Young’s modulus of 30 x 10& psi;

the secant modulus at 100,000 psi was 28.2 x 10& psi. The

reduction in area at point of fracture was 35 percent.

2.3 Specimens

All types of blocks were so precisely made that intimate

contact between them could be provided by a very thin joint.

One assembly was tested with bare joints and later retested

with asbestos gaskets. All others had either neat cement,

neat plaster or calked joints. Cement or plaster joints

were made by dipping the ends of blocks into the respective

material. All cement joints were moist-cured for at least

two days. Plaster joints were found to be very convenient

to use since they did not need any moist curing and gained

sufficient strength after a few hours of drying.

Two kinds of joint fillers were used in calked joints:

"Igas No. 7," a soft bituminous material and "Kalk-Kord," a gray heavy mastic in the form of extruded bead. Because they

are soft and squeezed to a very thin layer when under load,

these caulking materials are applicable only to precision

blocks.

Test Series 1 consisted of 20 small column specimens composed of three blocks each, the type of blocks and type of

joints being as designated in table 1. In specimens Nos. 1

through 13, "Stacked" arrangement was used, i.e., the blocks

were stacked like a chimney with all holes In the webs at

corresponding locations. In specimens Nos. 14, 15, 16 , and

17, "Crisscross" arrangement was used, i.e., the axis through

the open ends of a block was perpendicular to that of adjacent

one. The same "Stacked" arrangement was used in specimens

Nos. 18 and 19 for Type UN blocks (no holes in the web).

"Stacked" arrangement of cells is Illustrated in figures 5

through 13, and "Crisscross" arrangement is shown in figures

14 and 15.

3 .

Specimen No. 20 consisted of a solid block on the top and

on the bottom and a "Preload” block in the middle. The joints

between these blocks were l/8 in. mortar of one part of Type

III portland cement and three parts of masonry mortar sand, by

weight

„

Test Series 2 consisted of 20 beams composed of five

blocks each, the type of blocks and type of joints being as

designated in table 2. "Stacked” arrangement was used In

beams Nos. 1 through 8 and "Crisscross" arrangement was used

In beams Nos. 9 through 18. Neat cement joints were used in

beams Nos. 1 through 13, and subsequently neat plaster joints

were used In all the others for the sake of expediency. Beams

Nos. 19 and 20 were arranged with ail the blocks side by side,

i.e., all webs in contact. This arrangement is hereafter referred to as "Side Construction/'

Prestressing of the Stressteel bars was accomplished by

means of a hydraulic jack whose force was measured by a calibrated dynamometer in the adapter bar. The loss of prestress

due to shrinkage and creep of concrete was not measured but

believed to be negligible.

The average prestress applied to the beams is given in

table 2. The maximum value of pre stress given in the table is

the initial prestress. In several cases the initial prestress

was reduced prior to test of the beam and the reduced value is

also given in the table.

In beams Nos. 1, 2, 3, Ip> 5, 6, 12, and 13 , the average

maximum and working prestress for each beam was 600 psi. Beams

Nos. 19 and 20 had no webs and therefore a correction was made

to provide an average flange prestress of 600 psi and 1200 psi,

respectively.

In all other beams it was intended to cause the specimens

to crack prior to testing to show the effect of the web reinforcement. Accordingly, In beams Nos. 7, 8, 10, 11, lip , l£,

16, and 17 a maximum prestress of 1200 psi was applied Initially; the prestress was then reduced to 600 psi In all beams

except Nos. 7 and 8, in which the prestress was not disturbed.

Beams Nos. 9 and 18 were prestressed to an initial maximum

of 900 psi and 1^00 psi, respectively, and both tested at 600

psi

.

Test Series 3 consisted of determination of compressive

strengths of individual blocks, two miniature slab tests and

a determination of strain distribution in Individual units

and short columns. The blocks used In the compressive tests

4 .
.
were representative of the types used in Series 1 and 2 and

had similar curing and age„ A sufficient number of tests were

made to determine the concrete compressive strengths both in

the stacked and side construction positions. The miniature

slabs consisted of nine blocks of Type UE with three rows of

three blocks each. The blocks were arranged in a crisscross

fashion and Stressteel bars were staggered to give concentric

resultant prestressing just as in the 5” by 5>-ft slabs

described in NBS report 4396. The prestressing force applied

in Slab A was enough to furnish about 1500 psi average stress

in the blocks in both directions and 1000 psi in Slab B. No

jointing material was used in either of these miniature slabs.

The strain distribution tests included one individual

specimen each of Type UN, Type PE and Type UE block, and of

a column test of three Type UE blocks, Stacked, and having

cemented joints. Bonded wire strain gages were attached to

individual block specimens; Tuckerman optical gages were

attached to the column specimens to measure longitudinal

strain and bonded wire gages were used to measure transverse

strain. The locations of gages are shown in figures 2 and 3»

3. TESTING METHODS

3.1 Test series 1, column tests

All columns were tested to failure In a 300,000 lb capacity hydraulic testing machine. Irregularities in the end

surfaces of the columns were taken up by placing a thin

asbestos gasket on each bearing end. Cracks were traced as

they developed and maximum loads were recorded. No crack

pattern was available for column No. 18 because the first

crack occurred at a load too close to ultimate load. Column

No. 19 was loaded with bare concrete blocks in contact with

each other and cracks occurred near the joints. Consequently,

the load was removed, asbestos gaskets were placed at the

joints and the column was loaded again until failure.

3.2 Test series 2, beam tests

All beams were tested to failure by flexure and shear in

a 60,000 lb capacity hydraulic machine. The beam was supported

on 6- by l/2- by 3/4“in « steel plates under each end block

and the plates rested on knife-edges approximately 2 ft apart

as shown in figure 4° Load was applied through a 1 in. roller

welded to a 6- by 6- by 3/4“in ' steel plate which rested

squarely on the center block in the beam. The center deflection of the beam was measured with a 0.001 in. micrometer dial

5 .
’

.
indicator placed as close to the middle as practicable. Again

the crack pattern traced as it developed with load.

3.3 Test series 3* compressive strength, strain

distribution and miniature slabs

All individual blocks were tested to failure in a 300,000

lb capacity hydraulic testing machine. At first all blocks

in the compression tests were capped with high strength gypsum

plaster on both loaded surfaces, but later on, asbestos gaskets were substituted as caps when they were found to be satisfactory in taking up small variations in dimensions of the

precision cast blocks. Some blocks were tested in end construction position (with load applied in the direction of the cell)

and others in side- construction position. Maximum load in each

test was recorded. The cracking load for those blocks that

developed cracks in early stage of the test were recorded.

In the miniature slabs the prestress was removed Immediately after completion of prestressing operation, and the slabs

were disassembled for Inspection. No loading tests were performed.

In the strain distribution tests all specimens were tested

in a 300*000 lb capacity hydraulic testing machine. Asbestos

gaskets were used to transfer the load uniformly from the

machine to the specimen. Readings of all gages were recorded

for the 5*000 lb M £lexing n load and zero readings were recorded

upon removal of the load. The strain increments of all vertical gages were promptly computed and were used as a guide for

centering of blocks with respect to the axis of the machine.

This process was repeated until the strain increments indicated

fairly uniform strain distribution. During the tests the readings of all gages were recorded for each load increment of

10,000 lb and sometimes for each 5*000 lb.

4. TEST DATA

The data for the columns in test series 1 are shown in

table 1 and crack patterns are shown in figures 5 to 15 . As explained in Section 3.1* column No. 19 was initially

loaded with the concrete in adjacent blocks in direct contact

1/ The numbers alongside the cracks indicate the applied loads.

The encircled number indicate the order of occurrence of

cracks

„

6 .
.
and the cracking load given in table 1 corresponds to this condition. The load was then released, asbestos gaskets were

placed between the blocks and the column was loaded to failure.

The test data for the specimens in beam tests are shown , in table 2 and crack patterns are shown in figures 17 to 29.

^

The relationship between center deflection and the load under

different conditions is shown in figure 30 . The compressive strengths for the single blocks in series

3 are listed in table 3* No crack patterns for blocks in the

end construction position were available since the cracking

load was very close to failure load. No cracks were observed

on the webs of blocks during the test of block of type UE in

the side construction position. Type UR block in this position cracked at approximately the same load as in test of

series 1, and the cracks were in the webs, usually through

the holes. In the miniature slab A which had 1^00 psi prestress, all nine blocks developed cracks during pre s tre s sing

,

while slab B, with 1000 psi prestress, six blocks developed

cracks. The cracks were very narrow and irregular. They were

essentially parallel to the shells and most of them passed

through the elliptical holes. The strain distribution data of

a three block column and three representative types of single

blocks are given in table !]_ and table 5? respectively.

l/ The numbers alongside the cracks Indicate the applied loads.

The encircled number indicate the order of occurrence of

cracks

.

7 .
•*
5. DISCUSSION OF RESULTS

From the data in tables 1 and 3> the following tables

can be summarized:

Average strength of column, ( stacked arrangement)

Joint material

Type

of

block

Cement

paste

Igas

KalkKord

Average Efficiency

kip s kips kip s kip s UE 68 60 74 67.it- 69

FE 62 60 61 63

SE 65 58 -- 62 ,, 8 65

UN 97 = — — 97 79

Average cracking load of column , (stacked arrangement)

Type

Crack at joint Crack at hole

of Percent Percent

bio ck Cracking of Cracking of

load maximum load maximum

load load

kip s kip s UE 22 32 29 43

FE 27 44 40 65

SE 24 38 30 47

Average strength of column, ( crisscross arrangement

)

Type Percent

of Cracking of Maximum Effi- bio ck load maximum load ciency load

kip s kip s UE 15 31 48 .71

UR 10 26 39 .75

UN 12 24 50 .57 (est.

8 .

In the above tables, the efficiency of a column with

stacked arrangement of cells is defined as Its strength

divided by the compressive strength of a single block In the

end- construction position; the efficiency of a column with

crisscross arrangement Is defined as its strength divided by

the compressive strength of a single block in the side-construction position.

As shown in the above tables, blocks of Type UN had

the highest block strength, column strength and efficiency

in a stacked arrangement; they had only moderate column

strength and somewhat lower efficiency in crisscross arrangement. The reinforced blocks of Type PE and Type SE blocks

cracked at higher loads but failed at same, or slightly lower

load than the unreinforced Type UE blocks. It was also found

that cracks appeared at the joints before cracking occurred

near the holes. In view of the fact that most of these

columns were fabricated of precision blocks with thin joints,

the initial cracking could be attributed to reasons other

than stress concentration near the holes.

A close examination of figures 5 to 13, revealed two

important facts. The first fact was that the cracks occurred

mostly in the webs and did not occur In the shells until incipient failure. The second fact was that only about 50 percent of the total number of cracks passed through the holes

before failure occurred. The other 50 percent originated at

the joints and did not pass through the holes at all. These

two effects were particularly pronounced in crisscross arrangement as shown In figure 16. The Type UN blocks, in stacked

arrangement and with cement joints, demonstrated freedom from

this type of cracking as illustrated in column No. 18 but

were just as vulnerable as the other types of blocks In the

crisscross arrangement. Since Type UN blocks had no holes

in the web, these tests had further indicated that the stress

concentration at the holes was at most a secondary cause of

cracks in the column tests.

In comparing the test results of columns Nos. 18 and 19,

the early appearance of cracks in the latter must be attributed to the lack of joint material to take up the Irregularities at the joint. These tests along with miniature slab

tests indicated that longitudinal cracks would occur, even in

precision blocks without jointing material, under axial compression.

Test series 2 indicated that the beams of unreinforced

blocks did not crack in stacked arrangement but cracked in

crisscross arrangement under nominal prestressing force. The

9 .
.

.
use of reinforcement in the webs of the other types of blocks

had either reduced the width of cracks or eliminated them altogether for the same prestressing force. These cracks had reduced the load carrying capacity of ail beams of crisscross

arrangement, especially the unreinforced blocks. The ratio of

the load carrying capacities of unreinforced to reinforced

blocks decreased from 0.78 for stacked arrangement to 0.54 for

crisscross arrangement. Beam No. 18 which carried 30 percent

less load than other beams of the same cell arrangement indicated that excessive prestress was detrimental to reinforced

blocks as well.

The strain distribution data indicated large variations

of strains for different locations on the same block or for

corresponding positions of different blocks. Nevertheless,

the data established the following:

1. High tensile strain existed near the hole in the transverse direction.

2. The band of concrete between the holes in the webs

and the bearing surfaces of the testing machine was subject to

a very small compressive strain in the longitudinal direction.

In other words, the stress flow by-passed not only the holes

but also the concrete directly above and below them.

3. Ihe restraining effect of the platens of the testing

machine was felt near the edge of the block in contact with

them. In the three block columns, the stress concentration

near the hole In the top block was of a moderate amount.

4. There was no continuity of stress pattern from block

to block across the joint and abrupt changes In longitudinal

and transverse stresses were observed across the thin cement

joints. In some cases changes from low tensile to low compressive strain was observed.

As explained above the stress concentration around the

hole played a secondary role in causing cracks in the webs of

the blocks. The principal cause of cracking is open to speculation. One possible explanation may be the bowing out of

shells under high load as shown in figure 31 where the stress

distribution is extremely complex and non-uniform. The

slightest deviation of the shells of the blocks from a true

plane would induce eccentric loading. Under this condition

the shells would bow like a buckled column even for low

slenderness ratios. Owing to the stress concentration around

the holes and the inability of concrete to resist tensile

forces, the webs In the middle blocks that serve as "ties”

10 .
.
to the twin columns, would crack at a relatively low load.

Reinforcement in the web would delay the occurrence of the

cracks and materially increase the cracking load. After

cracking, the reinforcement holds the crack width to a minimum and resists the transverse load tending to cause diagonal

tension failure. The reinforcement did not eliminate cracks

but minimized the damage caused by the cracks.

Crisscross arrangement showed a much lower resistance

to cracking due to prestressing and also lower resistance

to transverse shear, especially if the blocks were not reinforced.

Figure 30 gives graphically the relationship between

loads and deflections for the 5-cell beams. Deflection

varied nearly proportionally with the load up to the point

when the cracks in the web began to open up and then the deflection increased more rapidly with small increases of load,

without a sharply defined transition.

As long as the shear resisting webs of the blocks were

not cracked, the deflection curves for reinforced and unreinforced blocks coincided in spite of the marked differences

between their load carrying capacities. In the case of reinforced block both the stacked and crisscross arrangements

showed, up to a point, the same relation between the deflection and load. In the case of unreinforced blocks the effect

of arrangement could not be determined because all webs in

the crisscross arrangement were cracked due to prestress. It

was also observed that if the shear resisting webs were cracked,

the deflection curves for stacked reinforced and crisscrossed

unreinforced blocks coincided, and the beams were less rigid

than those with uncracked blocks. This observation indicates

that the cracks in the web of a beam of this type were the

largest single factor affecting the rigidity of a beam. That

is, the elastic deflection equation of a beam of this type

failed to predict the deflection accurately if and when the

webs of the beam were cracked. This held true whether the

cracks were due to transverse shear during the testing or

other causes prior to testing. Beams with blocks that were

cracked due to prestressing and beam No. 4 which was cracked

when it was inadvertently loaded upside down, produced a load

deflection curve which deviated consistently from a straight

line during the early stage of loading.

11 .

6. CONCLUSIONS

1. Cracks running parallel to shells occur in the webs

of all types of blocks under axial compression. Blocks in a

crisscross arrangement develop cracks at lower stresses than

similarly loaded blocks in stacked arrangement.

2. Suitable jointing material must be used even in most

precisely made blocks in order to avoid early cracks.

3. Shape of holes in the webs of blocks Is a minor

factor in the formation of cracks. Cracks occurred in blocks

without holes.

4. Presence of these cracks reduces the load carrying

capacity and increases the deflection of beams composed of

these blocks.

5. While the occurrence of these cracks Is unavoidable

in this type of block and arrangement, the formation of cracks

can be significantly delayed by Increasing the tensile resistance of the block webs either by suitable reinforcement or by

improving the quality of the masonry units.

6. It was observed that a nominal prestress in beams

(600 psi) with crisscross arrangement of blocks produced

longitudinal cracks, while a prestress of 1000 psi in miniature slabs produced such cracks in both of the slabs examined

immediately after pre s tre s sing

.

12 .

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Table 3* Compressive Strength of Individual Cellular

Bio cks

Compressive strength, (kips)

Type UE Type UR Type UN

On end On side On end On side On end On si

87

94

97.4

110

64

65.1

67.8

68

70.4

73.6

60

63.5

67.2

73

60

76.3

79.8

45.9

59.2

53.8

125

120.5

Avg.

strength 97.1 67.7 72.0 52.0 122.8 87

( e s t . ) Ratio of

strengths

(side to end

)

0.70 C\J c

0 0.71

( est .

)

Maximum 6070

stress

,

psi

7530 4500 5780 7670 9670

(est.

)

Ratio of

maximum

stresses

( side to end

)

1.24 1.28 OJ vO 1

—

1

Table 4- Strain Distribution in a Column.

Strain, in. /in. u

SR-4 Gage No. 2/

t Load

, (kips)

t

! T

- ~i t ? ? t r ? t

*

' 1

t

’ 2

t

f 3

t

1 4

1

T 5

1

* 6

t

' 7

t

! 8

t

t 9

t

< 10 '

f

1

10 - 7 - 10 28 35 - 5 • 43 8 5 10 -25

20 16 12 30 55 -23 70 3 25 2 -45

30 14 45 67 180 -35 105 13 45 - 8 -62

1+0 - 7 125 300 432 -40 145 38 70 -30 -88

5o 7 162 1683 3640 -45 185 200 75 48 30

55 30 160 2538 4250 -30 210 213 85 80 38

1

t

t Load

i (kips)

t

1

t Tuckerman Gage No.

1

t

!

’ E-l , W-l

t

C\J

•N 1 CM E-3, W-3

t

t

* e-4, w-4 ’

t

’

10 -140 -40 -136 -105

20 -283 -90 -296 -225

30 -468 -113 -410 -338

40 -668 -120 -652 -463

50 -859 -45 390 -903 -613

55 -966 -45 5oo -1025 -746

1/ Positive numbers indicate tensile strains.

Negative numbers indicate compressive strains.

2/ For location of gages see Figure 3.
.

ft

'
Table 5* Single Block Strain Distribution

Strain, 10 _o in. /in. —

/

t

»

T Type T

» of ’

f blocks *

t t

t Load |

(kips) »

t

SR-4 Gage No. 2/ ?

?

1 , 2

I

' 3,4

t

t

1

' 5,6 *

t t

1 7,8

; 9,10 ’

?

! 11,12 *

?

10 - 7 - 81 26 - 248

20 12 -208 36 - 493

30 66 -327 - 3 - 766

UN 40 123 -475 -17 - 982

50 177 -634 -29 -1308

60 213 -778 -74 -1530

65 237 -871 -71 -1658

5 - 5 - 20 - 91 - 112 - 61

10 - 4 - 51 - 181 - 221 - 131

15 11 - 77 - 282 - 338 - 208

20 53 -101 - 383 - 477 - 286

FE 25 218 -117 - 497 - 615 - 347

30 374 -103 - 601 - 711 - 429

35 845 - 81 - 701 - 908 - 514

40 1236 - 81 - 798 -1065 - 606

45 1619 - 91 - 897 -1230 - 706

5 - 5 - 30 - 72 - 72 - 92

10 l - 56 -140 - -133 - 160

15 20 - 74 -168 - 172 - 213

20 22 -106 -282 - 234 - 315

UE 25 50 -115 -3 55 - 360 - 388

30 63 -108 -423 - 439 - 473

40 429 -156 -578 - 609 - 658

5o 836 -197 -728 - 776 - 877

60 1586 -232 -885 - 940 -1031

65 2186 -237 -986 -1058 -1157

1/ We gat ive sign indicates compressive strain.

Positive sign indicates tensile strain,

2/ For lo cat ion of gages, see figure 2,

note: cell dimensions in end view are same for all

TYPES OF BLOCKS. FOR DETAILS OF SIDE VIEWS

OF TYPE SE 8 TYPE FE SEE TYPE UE.

TYPE UE

NO. 4

WIRE

TYPE SE TYPE FE

1" ({> HOLE-^

b 6

SIDE VIEW

TYPE UR

SIDE VIEW

TYPE UN

FIG. I CELLULAR BLOCKS

E

| Wi

8

-—

6

4

2

BLOCK NO. I TYPE UN BLOCK

BLOCK NO. 2

TYPE FE BLOCK

BLOCK NO. 3

TYPE UE BLOCK

FIG. 2 LOCATION OF SR 4 STRAIN GAGES IN

STRAIN DISTRIBUTION TEST.

legend: gage i thru io - SR 4 ELECTRIC GAGES

GAGE E-l THRU W-4 - TUCKERMAN GAGES

TYPE UE BLOCK

FIG. 3 GAGE LOCATION IN STRAIN DISTRIBUTION TEST

FIG. 4 SET - UP FOR BEAM TEST

TYPE

UE

BLOCK,

STACKED

NEAT

CEMENT

JOINTS.

FIRST

CRACK -

32

KIPS

MAX.

LOAD68

KIPS

CO

in

(£

Li_

CRACK

PATTERN

SN

COLUMN

NO.

TYPE

UE

BLOCK,

STACKED,

NEAT

CEMENT

JOINTS.

FIRST

CRACK

-

19

KIPS

MAX.

LOAD

-

70.2

KIPS

(/)

TYPE

UE

BLOCK,

STACKED,

NEAT

CEMENT

JOINTS.

FIRST

CRACK -

12

KIPS

MAX.

LOAD65.5

KIPS

</>

ro

in

ID o £

If)

CRACK

PATTERN

IN

COLUMN

NO.

TYPE

UE

BLOCK,

STACKED I

GAS

JOINTS.

in

CL— CO * a. in *

CM

iD i <0 * i O< a

cl < o o

-J

Li. 2

FIG. 8

CRACK

PATTERN

IN

COLUMNS

NO. 4a5

TYPE

UE

BLOCK,

STACKED

KALK -

KORD

JOINTS.

co in

CL CL ^ *

in

O CJ (X) Xo a < <

<z

O o _i

hCO

X

tr <

COa co . co x «

h- • CO X £ <

Li_ 5

CD6

CRACK

PATTERN

IN

COLUMNS

NO. 687

TYPE

FE

BLOCK,

STACKED

NEAT

CEMENT

JOINTS. o<

oro

f—00

o:

Q<O

_JX<2 o<

o:o i Q<O H

in

orL

x<

FIG.

10

CRACK

PATTERN

SN

COLUMNS

NO. 8&9

TYPE

FE

BLOCK,

STACKED

IGAS

JOINTS.

FIRST

CRACK -

20

KIPS

MAX.

LOAD60

KIPS

FIG.

II

CRACK

PATTERN

IN

COLUMN

NO.

10

TYPE

SE

BLOCK,

STACKED

NEAT

CEMENT

JOINTS.

(/) a.

OJ*u<

a:o

CDQ<O

to

x* E 5

C\J

cCO

(/> 3

_ioo

TYPE $E

BLOCK,

STACKED

IGAS

JOINTS.

FIRST

CRACK -

20

KIPS

MAX.

LOAD58

KIPS

FIG.

13

CRACK

PATTERN

IN

COLUMN

NO.

13

TYPE

UE

BLOCK,

CRISSCROSS

ARRANGEMENT,

NEAT

PLASTER

JOINTS.

FIRST

CRACK -

10

KIPS

FIRST

CRACK -

15

KIPS

MAX.

LOAD38.7

KIPS

MAX.

LOAD47.6

KIPS

Id

FIG.

14

CRACK

PATTERN

IN

COLUMNS

NO.

14a

15

TYPE

UN

BLOCK,

CRISSCROSS

ARRANGEMENT,

NEAT

PLASTER

JOINTS.

FIRST

CRACK -

15

KIPS

FIRST

CRACK - 8

KIPS

MAX.

LOAD50

KIPS

MAX.

LOAD49

KIPS £ I

FIG.

15

CRACK

PATTERN

IN

COLUMNS

NO.

16

,g. 16 - Typical crack pattern in columns with crisscross arrangement.
II
TYPE UE BLOCK, STACKED,

NEAT CEMENT JOINTS.

MAX. LOAD - 8.0 KIPS

SOUTH

NORTH

FIG. 17 CRACK PATTERN IN BEAM NO. I

TYPE UE BLOCK, STACKED

NEAT CEMENT JOINTS.

MAX. LOAD - 7.2 KIPS

SOUTH

FIG. 18 CRACK PATTERN IN BEAM NO. 2

TYPE FE BLOCK, STACKED,

NEAT CEMENT JOINTS.

MAX. LOAD - 10. 1 KIPS

SOUTH

legend: —FRACTURE

CRACK

FIG. 19 CRACK PATTERN N BEAM NO. 3

TYPE FE BLOCK, STACKED,

NEAT CEMENT JOINTS.

MAX. LOAD - II. I KIPS

SOUTH

NORTH

NORTH

FIG. 20 CRACK PATTERN IN BEAM NO. 4

TYPE SE BLOCK, STACKED,

NEAT CEMENT JOINTS,

MAX. LOAD - 9.5 KIPS

TOP

SOUTH

TOP

FSG. 21 CRACK PATTERN IN BEAM NO. 5

TYPE SE BLOCK, STACKED

NEAT CEMENT JOINTS.

MAX. LOAD - 8.3 KIPS

NORTH

TOP

SOUTH

BOTTOM

FIG. 22 CRACK PATTERN IN BEAM NO. 6

BEAM NO. 7, TYPE UE BLOCK, STACKED,

NEAT CEMENT JOINTS. MAX. LOAD-9.4 KIPS

SOUTH

BEAM NO. 8, TYPE UR BLOCK, STACKED,

NEAT CEMENT JOINTS. MAX. LOAD-13.0 KIPS

SOUTH

NORTH

FIG. 23 CRACK PATTERN IN BEAMS NO. 7 8 8

BEAM NO. 9, TYPE UE BLOCK, CRISSCROSS ARRANGEMENT,

NEAT CEMENT JOINTS. MAX. LOAD - 3.4 KIPS

SOUTH

BEAM NO. 10, TYPE UE BLOCK, CRISSCROSS ARRANGEMENT,

NEAT CEMENT JOINTS. .MAX. LOAD - 3.3

SOUTH

o

NORTH

FIG. 24 CRACK PATTERN IN BEAMS NO. 9 a 10

BEAM NO. II, TYPE UR BLOCK, CRISSCROSS ARRANGEMENT,

NEAT CEMENT JOINTS. MAX. LOAD - 2.8 KIPS

SOUTH

NORTH

BEAM NO. 12, TYPE UR BLOCK, CRISSCROSS ARRANGEMENT,

NEAT CEMENT JOINTS. MAX. LOAD - 3.2 KIPS

SOUTH

FIG. 25 CRACK PATTERN IN BEAMS NO. II & 12

BEAM NO. S3, TYPE UE BLOCK, CRISSCROSS ARRANGEMENT,

NEAT CEMENT JOINTS. MAX. LOAD - 4.1 KIPS

SOUTH

NORTH

BEAM NO. 14, TYPE FE BLOCK, CRISSCROSS ARRANGEMENT,

NEAT PLASTER JOINTS. MAX. LOAD - 5.8 KIPS

SOUTH

NORTH

FIG. 26 CRACK PATTERN IN BEAMS NO. 13 Q 14

BEAM NO. 15, TYPE FE BLOCK, CRISSCROSS ARRANGEMENT,

NEAT PLASTER JOINTS. MAX. LOAD - 7.0 KIPS

SOUTH

BEAM NO. 16, TYPE SE BLOCK, CRISSCROSS ARRANGEMENT,

NEAT PLASTER JOINTS. MAX. LOAD - 5.9 KIPS

SOUTH

NORTH

FIG. 27 CRACK PATTERN IN BEAMS NO. 15 a 16

BEAM NO. 17, TYPE SE BLOCK, CRISSCROSS ARRANGEMENT

NEAT PLASTER JOINTS. MAX. LOAD - 6.3 KIPS

SOUTH

NORTH

BEAM NO. 18, TYPE SE BLOCK, CRISSCROSS ARRANGEMENT

NEAT PLASTER JOINTS. MAX. LOAD - 4.2 KIPS

SOUTH

NORTH

FIG. 28 CRACK PATTERN IN BEAMS NO. 17 8 18

BEAM NO. 19, TYPE UE BLOCK , SIDE CONSTRUCTION,

NEAT PLASTER JOINTS. MAX. LOAD - 1.2 KIPS

SOUTH

o

NORTH

BEAM NO. 20, TYPE UE BLOCK, SIDE CONSTRUCTION,

NEAT PLASTER JOINTS. MAX. LOAD - 1.2 KIPS

SOUTH

NORTH

FIG. 29 CRACK PATTERN IN BEAMS NO. 19 a 20

o

o

Ul

_J

Ll, UJQ

CCUJ

h*

Z

UJo

sdix ‘avcn

VIEW OF COLUMN ASSUMED MECHANISM OF

AT ZERO LOAD FAILURE OF THE COLUMN

FIG. 31 SCHEMATIC DIAGRAM SHOWING

MECHANISM OF FAILURE OF COLUMN

THE NATIONAL BUREAU OF STANDARDS

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The functions of the National Bureau of Standards are set forth in the Act of Congress, March

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