Teorija - Experimental Determination Mechanical Properties Clay Brick Masonry

8/19/2019 Teorija - Experimental Determination Mechanical Properties Clay Brick Masonry

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Canadian Journal on Environmental, Construction and Civil Engineering Vol. 3, No. 3, March 2012

EXPERIMENTAL DETERMINATION OF THE MECHANICAL PROPERTIES

OF CLAY BRICK MASONRY

T.C. Nwofor

Department of Civil and Environmental Engineering

University of Port Harcourt, Rivers State, Nigeria.

P.M.B 5323, Port Harcourt

[email protected]

Abstract:

The structural behaviour of masonry is influenced by the mechanical properties of the

constituent materials. Therefore a full mechanical characterization is required for propernon-linear analysis of masonry structures. Hence uniaxial compressive test is carried out

on unreinforced masonry and its constituents (clay bricks and mortar). From this study,

compressive stress-strain relationships at different confining stress levels have been

defined. In this paper the experimental results obtained is used to formulate simpleanalytical models for the purpose of estimating the modulus of elasticity of unreinforced

masonry, utilizing the control points established in this work. The proposed material

model can be employed in the non-linear finite element analysis of masonry structures.

Keywords: Brick-mortar masonry, compressive stress, strain and modulus of elasticity.

1. Introduction

The properties of brickwork are influenced by variables of bricks, type of mortar,

physical properties of the sand and lime used for the mortar, state of bricks before

casting, curing workmanship and many others. Hence it can be deduced that in the

experimental determination of mechanical properties of brickwork, a large number of

variables can be considered. We should note that the analysis and design of buildings

require the material properties of masonry, for example, the modulus of elasticity of

masonry is require for the non-linear static analysis. Stress-strain curves of masonry are

required for more detailed non-linear analysis of masonry structures. Limited research


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has been carried out by researches to obtain a realistic material property for masonry [1]-

[4]. Also laboratory test have also been carried out on masonry, adopting the approach of

a homogenous continuum material made up of brick units, mortar joints and any unit-

joint interfaces [5]. The wide variation of test value of the mechanical property of

masonry and its units especially when under the influence of compressive load [6]-[9] has

not aided the formulation of realistic stress-strain curves for non-linear modeling of

masonry and infilled frame structures. Hence, in this present study, extensive

experimental testing of brick masonry prism material according to ASTM specification

[10] would be performed to obtain stress-strain curves. Also experimental relationships

would be obtained between the modulus of elasticity of masonry units of its compressive

strength. Furthermore, simple analytical equations are developed using the experimental

data to estimate the mechanical properties and plot the stress-strain curves for masonry.

However, to maintain the scope of this research, the materials used have been kept

constant. The bricks, cement, sand and lime used are described below.

2. Materials and Experimental Procedure

The bricks employed are solid burnt clay bricks of average size of 224 x 106 x 72mm.

Typical physical properties are shown in Table 1. The absorption rate of bricks immense

in water at room temperature is also shown in Figure 1.

Table 1: Physical properties of bricks

No. of

specimens

Compressive Strength

(x 106 kN/m

2 ) Std Dev

Mean Range

Crushing strength * 20 23.30 18.69-27.25 2.21

ψ 102 22.00 - 2.32

Length (mm)

Breadth (mm)

Depth (mm)

*

*

*

20

20

20

224

106

72

223.1-224.5

106.2-106.8

71.1-72.9

0.391

0.183

0.194

Water Absorption

% by wt. after 25 hrs, immersion 12.49

% by wt. after 5 hrs, boiling 12.91


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(*) Values obtained by author

(ψ ) Values obtained by British Ceramic Research Association

The mortal mixes will consist of cement, lime and sand, while ordinary Portland cement

would be used for this investigation so as to use the 28

th

day strength.

0

2

4

6

8

10

12

14

16

0 5 10 15 20 25

immersion time (mins)

A b s o r p t i o n

( b y w e i g h t ) %

Figure 1: Absorption of Bricks

Also, graded sand classified in zone 2 was generally used for this investigation to prepare

the mortar. The particles distribution analysis is shown below for a sample of 300grams.

Sieve analysis was carried out on the river sand sample and the results shown in Table 2.

The result revealed the sand sample was well graded falling into zone 2 near border of

zone 1, which is very appropriate for concrete work in accordance with BS 882, part 2

1992 [11]. The fineness modulus of the sand was found to be 3.15, which makes the sand

sample a rather coarse one.


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Table 2: Particle size analysis on fine aggregate sampleSieve Mass on

(g)

% on sieve %

retained

%

passing

Zone 2

Limits

Max. on sieve

permitted (g)

5.00mm

2.36mm

1.18mm

600.00µm300.00µm

150.00µmTray

No.7

14

2552

100

12

54

60

6663

+

39

6

4

18

20

2221

13

2

4

22

42

6485

98

-

96

78

58

3615

2

-

90-100

75-100

55-90

35-598-30

0-10

-

-

200

100

7550

40

315

+Needed dividing as it exceeded the maximum permitted on sieve.

Zone = zone 2, near border of zone 1.

Fineness modulus (FM) 315 ÷ 100 = 3.15 (rather coarse)

A mortar mix proportioning of 1:¼:3, 1:0.5:4.5 and 1:0:6 corresponding to avolume proportioning of cement, lime, and sand respectively are generally used, while

maintaining reasonable workability for mortar is achieved by varying the water-cement

ratio ( C W ) to produce suitable workability.

2.1 Water Cement Ratio ( C W ) of Mortar

In concrete work the term water/cement ratio, if not qualified, could refer either to

effective water/cement ratio or total water/cement ratio. In this investigation, thewater/cement ratio of fresh mortar is an important factor in determining the properties of

the hardened mortar (as a joint) in brickwork. It is therefore necessary to clarify the

definition of this term as used in this work.

Assuming only fine aggregates (i.e. sand in the case of this investigation), the effective

water/cement ratio for strength is defined as:

Effective ( C W ) = total ( C W ) – as( C S ) (1)

where

total C W = total amount of water added to the dry mix

aS = 30mins absorption capacity of the sand (in the air-dry state).

S/c = sand/cement ratio by weight.

For the oven-dry sand used throughout this investigation as (in this case corresponding to

maximum absorption capacity) was found to be 0.024.


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Hence from equation 1

Eff. W/C = total W/C – 0.024s/c (2)

Table 3 gives a comparison of the effective W/C with the total W/C for two typical mixes

used.

Table 3: Comparison of the effective W/C with the total W/C

Mortar Total W/C (by wt.) Effective W/C (by wt.)

1:¼:3 1.0

0.8

0.93

0.73

1:05:45 1.0

2.6

0.88

2.48

It should be noted that the term W/C used throughout this work refers to the total

W/C as defined above.

2.2 Actual C W of Mortar Joint

Owing to absorption of water by bricks, the W/C of the mortar before placing is

different from that after placing between bricks. Therefore, while any control specimens

(such as cubes or prisms) would be useful for indicating the relative qualities of different

batches of mortar mixes, it should be appreciated that properties such as crushing

strength, Young’s modulus, Poisson’s ratio, determined from such specimens may not

bear much resemblance (except by correlation) to those of the same mortar in the

hardened state (as a joint) between the bricks.

A theoretical relation between the W/C’s of the control specimens and the mortar

joint was derived by considering the amount of water absorbed from a known weight of

fresh mortar placed between two bricks. The relationship is given by

C W a = W/C – k(C + L + S + W)/C (3)

where

C W a = actual water/cement ratio of mortar between bricks (or of mortar joint)


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C W = water/cement ratio of the fresh mortar (or control specimen)

mortaroriginalof wt.

bricksbyabsorbedwaterof wt.=K

The value of k was determined experimentally. It is assumed that loss of water to theatmosphere from the bricks- mortar couplet and from the control specimen is the same.

For 1:¼:3 mortar with W/C = 1.0

C W a = 1.0 – 5.25k (3a)

Corresponding expressions for other values of C W could be obtained similarly.

These relationships are plotted in Figure 2. The conditions for saturated bricks and for

bricks soaked for one minute before casting are indicated by vertical lines AB and CD

respectively obtained from measured values of k. The intersections of these lines with

the straight line represented by equation 3a give the values of actual water/cement ratio

(Wa/C) for ‘saturated’ bricks and for bricks soaked for one minute.

.

.

.

.

.

.

. . . . . . .

/ .

/ .

/ .

Figure 2: Relationship between C W a and K

The respective values being 0.94 and 0.5. The indication is therefore that for

saturated bricks, while the W/C for the control specimen is 1.0, the actual water/cement

ratio ( C W a ) of the corresponding mortar joint would be of the order of 0.94. For bricks


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soaked for one minute (or with a moisture content of about 6%) the corresponding values

are W/C = 1.0, C W a = 0.5. The deductions drawn from these results are as follows:-

i. To determine properties of mortar joint, such as tensile or shear strength, realistic

values may be directly obtained from test on brick-mortar couplets.

ii. For elastic analysis of brick-mortar couplet or brick-work as a non-homogenous

material, meaningful values of elastic modulus and Poisson ratio for the mortar

joints may be obtained from tests on mortar specimens with C W ratio value

equal to the value of the actual water/cement ratio ( C W a ) of the mortar joint.

3. Mechanical Properties of Bricks and Mortar

3.1 Compressive/Crushing Strength of Brick The maximum compressive stress of a brick-mortar prism is determined by applying a

compressive load in the direction parallel and perpendicular to the bedding planes, hence,

the fabricated bricks are built into a prism of different layers with constant mortar joint

thickness. It is important to note that while these test give reasonably good indication of

the crushing strength of brick-mortar prism for control purposes it is doubtful if they give

the compressive strength of brick work as a basic physical property. Several research

work on concrete specimens which can also be related to brickwork has shown that some

important factors influences the compressive strength of specimen such as size of

specimen, surface condition, state of stress induced in the specimen, thickness of mortar

joint and also the testing technique. Hence the most important factor arrived at, is that

the direct measure of the uniaxial compressive strength of concrete which gave a realistic

value of the value for the basic property of concrete in uniaxial compression is a case

where the height to width ratio of the prisms is greater than 2.5.

From the foregoing, compression tests were carried out on bricks with varying

height to width ratios in the compression machine. For the case of loading parallel single

bricks were tested, Figure 3a while for the case of loading perpendicular to the bedding

planes of the brick the respective H/L ratios are obtained by varying the number of bricks

in the prisms as is shown in Figure 3b.


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The crushing strength of the bricks were generally found to decrease with increase

H/L ratio to a limiting value of 23.28N/mm2. This reflects the value shown in table 3.1.

This value shows the average of the result obtain from both loading perpendicular and

parallel to the bedding plane. The variation of brick crushing strength with H/L ratios is

shown in Figure 4. Hence it can be observed that more realistic results would be

obtained by loading single bricks parallel to these bedding plane.

Table 4: Summary of crushing strength of bricks

Number oftests

H/L Crushing meanstrength (f b)

×103kN/m3

Range description

10

101010

10

0.32

0.901.512.15

2.12

38.36

25.1929.7124.15

23.16

33.92-44.33

22.59-28.0819.26-29.8222.48-25.89

18.69-27.25

Type (b) 1 brick

Type (b) 3 brickType (b) 5 brickType (b) 7 brick

Type (a) 1 brick

3.2 Crushing Strength of Mortar

Compressive strength test were carried out on 20mm mortar cubes and a graphical

representation of the results shown in Figure 3.4 for different ages of a 1:¼:3 nominal

mix of mortar by varying the water-cement ration of the mix.

() ()

Figure 3: Compressive loading on brick specimens (a) Loading parallel to

bedding planes (b) loading perpendicular to bedding plane


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0

2

4

6

8

10

12

14

16

18

20

0 5 10 15 20 25 30

Age (days)

C r u s h i n g s t r e n g t h

( x 1 0 3 k N / m 2 )

W/c = 0.8

W/c = 1.0

W/c = 1.2

Figure 4: Crushing strength of 1:¼:3 grade of mortar mix.

3.3 Modulus of Elasticity and Poissons Ratio for Brick

The static method was used to obtain elastic properties of brick. In order to

produce uniaxial compression in the middle portion, single bricks were loaded in

compression in a direction perpendicular to the bedding planes. Longitudinal

compressive strain yε and the corresponding lateral tensile strain ( )

xε were measured

in the middle region by using suitable electrical strain gauges. By measuring the

compression load and the strains ε y and ε x as shown on table 5, the stress-strain curves

y

y

ε α

and x

y

ε α

can be obtained. Young’s modulus (E) and Poissons ratio (v) were

obtained from the slopes of the linear portions of the stress-strain curves as follows.

x

y E

ε

α = (4)

x

y

y

y

y

xv

ε α

ε

α

ε ε == (5)

Table 5 shows values of Modulus of elasticity (E) and Poissons ratio (v) thus

obtained. E1 and V1 denote values obtained from strain measurements on face 1, E2 and

V2 correspond to values for face 2. Two sizes of bricks were tested. Type (a) is the


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normal single brick, and type (b) is the single brick made to produce a square section

(72mm x 72mm) perpendicular to the loading direction.The values shown in Table 5

were obtained from test on twenty (20) specimen of bricks and the stress-strain curves

were obtained from an average of about six sets of readings obtained by loading and

unloading the specimen six times.

Table 5: Summary of test result for brick units

Description No. of

specimens

(x 103kN /

m2) Fb

(x 10 kN/m2) V1 V2 Failure

strainE1 E2 Av.E

10 23.10 8.83 8.14 8.49 0.09 0.08 0.0045

10 23.18 8.76 8.89 8.83 .06 .08 0.0048

The stress-strain curve as a result of the two cases of loading for bricks is shown

in Figure.5. The average value for crushing strength Fb and failure strain is also shown inTable 6. The variation of modulus of elasticity Eb with the crushing strength Fb is shown

in Figure 6 and it is seen with the best line of fit drawn, that the average relationship in

equation (6) can be obtained between Eb and Fb with a coefficient of correlation Cr = 0.60

=b

E 348.51Fb (6)

Type (a)

2 1

Normal bricks

2 1

Type b

Brick with squarecross-section


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. . . . . . . . .

(εεεε)

( σ σσ σ )

Figure.5: Stress-strain curves for brick

.

.

( )

( )

Figure 6: Variation of modulus of elasticity with crushing

strength of bricks (40No. bricks)


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3.4 Modulus of Elasticity and Poissons Ratio for Mortar

It was seen earlier that due to the absorption of water by the bricks from the fresh mortar,

the value of the actual water/cement ratio of the mortar joint is smaller than its original

value. In order to obtain realistic values of the Modulus of elasticity and Poisson ratio for

the mortar joint, a 50mm x 50mm x 125mm mortar Prisms with a particular water/cement

cured for 21 days, were tested. Both longitudinal strain yε and lateral strain ( )

xε were

measured by electrical resistance strain gauges, and stress-strain curves can be plotted for

εy and εx. Modulus (E) and Poissons ratio (v) were calculated by using Equations 4 and 5.

Table 6: Summary of average of test result conducted on different mix proportions

of mortar prisms

Mortargrade

No. ofspecimen

Average f rx 10

3kN/m

2

Er x 10

6kN/m

2

V Failurestrain

1:¼:3

1:0.5:4.51:0:6

4

44

22.03

13.104.2

3.90

3.450.75

0.18

0.180.17

0.019

0.02200.0090

The compressive stress-strain curves for the mortar mix for the adopted grades of

mortar is shown in Figure 7 while the variation of the modulus of elasticity of mortar (Er)

with the corresponding compressive strength (f r) is shown in Figure 8.

. . . . . .

(εεεε)

( σ )

( σ )

( σ )

( σ )

/

..

Figure 7: Stress-strain curve for different grade of mortar prisms


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.

.

( )

( )

/

. .

Figure 8: Variation of modulus of elasticity to compressive strength for mortar

The relationship between the stress and strain was linear while observing the

initial portion of the stress-strain curve up to about 35 percent of the mortar strength and

then is followed by a non-linear curve extending beyond the strain limits. The stress

reading beyond the strain limits of the mortar prisms with of grade 1:0:6 was difficult to

read because of the relatively low strength of these samples with a mean value of the

failure strain equal to 0.0090. An observation of Figure 8 shows that an average

relationship can be obtained in equation 7 by drawing a line of best fit.

Er = 231.11Fr (7)

A good correlation coefficient of 0.9 was obtained between the values of the

experiment test results. Also it would appear that more realistic values for E for the

mortar joint in a brickwork may be obtained by substituting the compressive strength

value (Fr) obtained from the test cubes of mortar with water/cement ratio value equal to

the value of the actual water/cement ratio ( C W a ) for the mortar joint given by the

expression in equation (3). An average value of 0.177 for poisons ratio (v) can also be

deduced from Table 6.


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4. Mechanical Properties for Brickwork

Elastic modulus and poisons ratio values for brickwork were obtained from compression

test on brick-mortar prisms by maintaining a length-height ratio of about 2. The

longitudinal and lateral strains would be obtained for cases of loading parallel and

perpendicular to the bedding plane as to obtain the modulus of elasticity in the two

orthogonal directions. The longitudinal and lateral strains will be measured by use of

electrical resistance strain gauges, and similarly the modulus of elasticity (E) and the

poisons ratio (v) values would be obtained through equation 4 and 5. Table 7 shows

summary of values obtained from the test carried out on a number of brick-mortar prisms

specimens. Values are obtained for compressive strength, failure strains, modulus of

elasticity and the poission’s ratio of masonry.

Table 7: Summary of test results on brick-mortar prisms

Description

of loading

Mortar

mix

Number

of

specimen

Compressive

strength

(×103kN/m

2)

Fm

Max.

strain

Modulus of

elasticity

(×106kN/m

2)

E

Poisson’s

ratio V

Perpendicularto bedding

plane

1:¼:31:0:4.5

1:0:6

88

8

13.4611.54

10.58

0.00190.0020

0.0047

8.417.21

6.61

0.290.33

0.36

Parallel to

beddingplane

1:¼:3

1:0:4.51:0:6

8

88

8.5

7.25.1

0.0057

0.00920.0086

5.32

4.673.21

0.18

0.210.28

Note * Vyx = xy x

yV

E

E

a

(b)

Figure 9: Set up for loading of brick-mortar prisms (a) perpendicularto bedding plane (b) parallel to bedding plane.


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The stress-strain curves are plotted using the average of values obtained from test

on 8 specimens of masonry prisms made with a specific mortar mix. The height of the

prisms was 400mm maintaining 10mm mortar joint thickness. A general setup for

loading in the two major directions is shown is Figure 8. The stress-strain curves for the

masonry prisms with mortar mix of 1:¼:3 is shown in Figure 10. Similar stress-strain

curves of masonry prisms made with other grades of mortar mix can also be obtained.

We should note here that in most cases, failure was as a result of vertical splitting cracks

along the depth of the prisms, when loading is perpendicular to the bedding plane while a

relatively diagonal splitting failure is notice when loading is parallel to the bedding plane.

It was generally noticed that the strength properties of masonry reduced as weaker mortar

is used. The stress-strain curve was seen to be linear to an extent after which a non-

linearity pattern is noticed. The variation of modulus of elasticity Em with compressive

strength f m is shown in Figure 11. An average relationship can be obtained for Em and f m

for perpendicular and parallel loading in Figure 8 and 9 respectively, with a coefficient of

correlation of 0.9 between the experimental value obtained from test on the masonry.

Em1 = 634.66Fm1 (8)

Em2 = 640.00Fm2 (9)

It would also be observed that the worst performance was seen in the prisms with weak

mortar joint as the compressive strength (Fm) was low with a corresponding high valuefor strain.

. . . . . .

(εεεε)

( )

Figure 10: Stress-strain curve for brickwork


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A study of the stress-strain curve, especially for the case of parallel loading shows that

certain salient points are easily observed on the stress-strain prisms pattern. The strain

values used to determine these points of interest varying with the grade of mortar used in

the prisms, as great difficulty is observed with deriving strain values when a weak grade

of mortar is used, especially after the near linear range; due to brick-mortar bond failure

and inivitable sudden collapse of the test specimens.

( )

( )

..

/

(a)

( )

(

)

/

.

(b)

Figure 11: Variation of modulus of elasticity for brickwork with corresponding

compressive strength (a) case of perpendicular loading (b) case of parallel loading


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Hence the following salient points are easily observed from this work and compares

favourably with [11].

(a) point 0.40Fm corresponding to the limit of the region at which the stress-strain

curve is near linear as much as possible, after which regional cracks starts

developing suggesting non-linearity.

(b) Point 0.75Fm corresponding to the particular stress at which vertical splitting

cracks are seen, but the masonry specimen still remains relatively stable.

(c) 0.95Fm corresponds to the stress level at which the splitting cracks have reached a

very advanced level and failure is ready to occur.

(d) Fm is the ultimate stress level in which the masonry is in a collapse state with a

corresponding rapid increase in strain reaching an observable failure strain in the

masonry.

5. Analytical Model for prediction of Stress-strain Curves of Masonry

Acknowledging that there exist a reasonable mathematical relationship between

the compressive strength of masonry and the modulus of elasticity of masonry, hence

analytically modeling to obtain f m is necessary as it is not always very feasible to conduct

test on masonry prisms. On the other hand, the compressive strength of bricks and

mortar (Fb and Fr) can readily to obtained through tests. The compressive strengths of

bricks, mortar and masonry can be properly related as proposed by Eurocode [12] by

equation 10

β α r bm f Kf f = (10)

where k, α and β are all constants for effective relationship. Observing experimental

stress-strain curves, f m depends on the brick strength more than the mortar strength, hence

α must be higher than β. Conducting an unconstrained regression analysis of equation 10

using the data obtained from our experimental study the values of 0.61, 0.51 and 0.36

have been obtained for k, α and β respectively using the least – square fit method and the

following equation proposed.


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Fm = 0.6136.051.0

r b f f (11)

The effectiveness of this relationship can be tested by the parameter λ, which represents

the standard error of estimate. A value of λ in equation 12 close to minimum reflects

low scatter of the actual data from the value obtained by the regression analysis [13].

( )

3

2

−

−= ∑

n

f f Riiλ (12)

where f i and^

Ri f = ith experimentally obtained and regression estimated prism strength,

respectively.

n = total number of data points.

From the experimental data a value of and 0.46 x 10

3

kN/m

2

is obtained for λ.

6. Conclusion

From the foregoing the basic mechanical properties of masonry has been obtained by

tests carried out on specimens. These mechanical properties are basic input parameters

for the numerical modeling of masonry and infilled frame structure, noting that masonry

is a composite material made up of brick units binded by mortar. Thus non-linear stress-

strain curves have been obtain for masonry with salient points identified on the stress-

strain curves with stress level of 0.40Fm corresponding to the limit of the near linear

region. Also simple analytical model has been proposed for prediction of the modulus of

elasticity of masonry, to aid the numerical analysis of masonry structures. Finally,

compressive test result obtained from test on brick units and mortar is enough to predict

the elastic properly of masonry, as simple relationships have been obtained for obtaining

the modulus of elasticity of bricks, mortar and masonry from their corresponding

compressive strengths.

References

1. Atkinson, R. H.; Noland, J. L.; Abrams, D.P. and McNary S., “ A deformation

failure theory for stack-bond brick masonry prisms in compression,’’ Proc. 3rd

NAMC, Arlington, pp. 1-18, 1985.

2 Lourenço, P.B., “Computational strategies for masonry structure,’’ PhD-Thesis,

Delft University of Technology, 1996, Delft University Press: Delft.


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3. Augenti, N., ‘’ Il Calcolo Sismico Degli Edifici In Muratura’’, UTET: Turin (in

Italian), 2004.

4. Augenti, N. and Parisi, F., “Stress-strain relationships for yellow tuff masonry in

direct shear,’’ 8th International Masonry Conference Dresden, 2010.

5 Lourenço, P.B., “Experimental and numerical issues in the modelling of the

mechanical behaviour of masonry,’’ In: Proc. of the 2nd Conf. on Structural

Analysis of Historical. Constructions, eds. P. Roca, J.L. González, E. Oñate &

P.B. Lourenço, CIMNE: Barcelona, 57-91, 1998.

6. Knutson H. H., “The Stress-Strain Relationship for Masonry,’’ Masonry

International, Vol. 7, No. 1, pp. 31-33, 1993.

7. Ali, S. & Page, A.W., “A failure criterion for mortar joints in brickwork

subjected to combined shear and tension, Masonry International, pp. 43-54, 1986.

8. Hansen, K.F. & Pedersen, E.S.: Shear and Torsion Testing of Brick-mortar Joints, Masonry International, pp.31-38, 2009.

9. Lourenço, P.B. & Ramos, L.F., “Characterization of Cyclic Behavior of Dry

Masonry Joints”, Journal of Structural Engineering ASCE , 130 5, 779-786, 2004.

10. ASTM “Standard test method for compressive strength of masonry prisms,’’Masonry test methods and specifications for the building industry; ASTMC 1314-

1346, 4th

Ed., Philadelphia, 2001.

11. BS 882, Part 2, “Specifications for aggregate from material source for concrete,’’

British standards Institution (BS1), UK, 1992.

12 European Committee of Standardization (CEN), “Design of masonry structures,Part 1.1: General rules of buildings – Reinforced and unreinforced masonry”,

ENV 19961.1, Eurocode 6, Brussels, Belgium, 1996.

13 Wesolowsky, G.O., “ Multiple regression and analysis of variance”, Wiley,

New York. 1976.

Teorija - Experimental Determination Mechanical Properties Clay Brick Masonry

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