12TH INTERNATIONAL

BRICK/BLOCK Masonry c O N F E R E N C E

EXPERIMENTAL STUDY ON STRENGTH OF THIN JOINT

By Mitsuaki NISHIYAMN, Shigeyuki IZAWN and Koji NISHIN03 'Assistant Professor of Dept. Architecture, Faculty of Engineering,

Nippon Institute of Technology

' Plant manager, Tohhoh Co.,Ltd.

'Adviser, Tohhoh Co.,Ltd.

ABSTRACT

The strength of O mosonry woll depends on the strength of the joint [7]. Therefore, it is indispensob/e to study the influence of bonding to understond the strength of a mo­sonry woll. As for mosonry with joints, decreosed strength hos usuolly been exomined by o compression test of a mosonry unit without joints ond o three-course prism. But, to prove the influence of a joint on the intensity, we hove to experiment not on/y with o compression test but O/50 with vorious other kinds of tests. From these points of view, this study wos investigoted with compression, tens i/e, bending, ond sheoring tests to see how the joint influenced the intensity. /n consequence of these experi­ments, eoch test indicated a different vo/ue with a decreose caused by the joint. Es­peciol/y, in the case of the sheoring test, the decreose wos remorkob/e.

Key words: thin-joint, epoxide resin, pre-mixed mortor, compression test, tensi/e test, bending test, sheoring test, strength ratio.

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INTRODUCTION

On a masonry wall, the joint has a function of adjusting dimensions, and yet it is also requires such abilities as transmitting stress naturally, prevention of leaks du­ring rain, excellent durability, and so on. A masonry joint is one of the important factors, which determines the entire durability of a masonry wall. Therefore, the choice of materiais for joints and the method of construction can decide the qua­lity of masonry.

In recent years, structures are being required to be of good quality (as to dura­bility, earthquake-proof, extensive space, and various efficiency for dwellings). Better masonry is absolutely needed in order to improve joints as well as im­proving masonry units. In japan, most materiais for joints of masonry walls are mortar with a thickness of around 1 cm. And, I regret to say, not a few masonry structures are of inferior structure beca use of a lack of technicians among other factors.

In these circumstances, simplification and rationalization of masonry construction are suggested. One of these is the thin-joint method (in the following, we call the thin-joint just a joint). This study was done to investigate whether this joint has enough availability or noto

The purpose of this research lies in looking into the intensity of the joint un­der various kinds of stress. In t his experiment, we examined the behavior of deformation, too . But I make mention of just the intensity due to a lack of spa­ce .

2. TEST PROGRAM

2.1. Specimen

As materiais for the base specimen, both a masonry unit and concrete have been chosen. Specimens without joints (as the base) are used for the purpose of chec­king their intensity, and we took the three kinds of materiais of a masonry unit, concrete and the materiais for joints (except the epoxide-type). Each specimen was examined as to its efficiency by compression test, tensile test, bending test and shearing testo And with each test, three specimens were used. The specimen related with the masonry unit was cut from each part of the unit shown in figure 1. The shape of each specimen is shown in figure 2, and the dimension is shown in table 1.

As figure 2 shows, the compression test has five kinds of specimens, the ten­sile test has three kinds, the bending test has three kinds and the shearing test has four. To examine the influence of the joint angle (the angle from the gi­ven pressure line) of both the compression test and the tensile test, we made specimens with angles of 90-deg rees, and 45-degrees. In the same way, on

fo r Compression Test for Te nsi le Tes t

···<>;·~r

( ..... .

' .. , ... for Te nsi le Spl i t t ing Test Masonry Uni t fo r Sheari ng Test for Full Grout

Figure 7. Cut Down for Specimens.

Speciments for CllfI'Ilress ion Test -l-

• - - - -<l Joint -l--l- CCy [t cuc O t

t -------

CUH -l-CP

<J

~ITr ,-, í - ------- <l

f------- + t t t

Specimens for Tensile Test . - - - -<l Joi nt

1m $ '1" .,iI, t t [t TUR Spli tti ng

TUC O TCY _~: Test , I -l-

-l-

Speclmens for Bending Test ·--- -<lJoint

ç;=:J~ OOH I

150 I

OCG I i fuQJ

I t

Table 7. Dimension of Specimens

for Compress ion T est

Symbol D imension

Base Materiais ( L*H*T 0*1:)

CUC 30*30*60 piece (form unit)

CUH 390*190*240 unit

CUV 190*390*240 unit

CP 390*(190*3)*240 3 units

CCY 100.p *200 concrete

for Tensile Test

Symbol Dimension

Base Materiais (L*H*T <1>*1:)

TUC 30*30*60 piece (form unit)

TUR 150.p *30 piece (form unit)

TCR 150 <b *40 concrete

TCY 100 <b *200 concrete

for Bending Test

Symbol Dimension

Base Materiais ( L*H*T)

BUC 40*30*120 piece (form unit)

BUH 390*190*240 unit

BCG 100*100*400 concrete

for Shearing T est

Symbol Dimension

Base Materiais (L*H*T <I> *1:)

SUR 150<b*30 piece (form unit)

SCR 150.p*30 concrete

SMR 150<b*30 joint material

SUD 190*190*30 piece (form unit)

SCD 190*190*30 concrete

SMD 190*190*30 joint material

SUDF 190*190*30 piece (form unit)

SUDU ( 190*2)*390*240 2 units

SCG 100*100*200 concrete

L. Length H: Height T,t : Thlckness (mm)

p

Specimens for Shearing Test . - - - -<l Joint

$MA SCR

SU~

~

SUD SUJU SCD -l-

~<> t

Figure 2. Shapes of Specimens and Ecperimental Methods.

Join t

......... -'--" "" Apparatus

p

Specimen Adhesion

Rounded Suppo r t

Figure 3. Method of Shearing Test on Circular Specimen.

the shearing test, we made specime ns wi th ang les of 90-degrees, 45-degre­es, and O-degrees . The contents of specimens on each test are shown in ta­bles from 2 to 5.

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Table 2. Specimens and Results on Comprression Test.

Joint

Name of Bactl material·' material e specimens 1 1

'3 Specimen shapes Joint ., thickness

0", .. mm de. N/ mm2

C [] CUC U - -

CUH H - -

CUHM1J90 -I Ml / 1 90

CUHM2J90 EJ M2 / 1 90

CUHM3J90 t M3 / 3 90

CUHM4J90 M4 / 3 90

CUV V

CUVM1 J45 Ml / 1 45 U

CUVM2J45 M2 / 1 45 -I

CUVM3J45

B M3/3 45

CUVM4J45 M4/3 45

CUVM1J90 M1 / 1 90

CUVM2J90 t M2 / 1 90

CUVM3J90 M3 / 3 90

CUVM4J49( M4 / 3 90

CCY C Y - -CM3Y M3 - -CM3Y M3 - -CM4Y M4 - -CCYM 1J45 lo M1 / 1 45

CCYM2J45 8 M2 / 1 45

CCYM3J45 l' M3/3 45

CCYM4J45 C

M4 / 3 45

CCYM1J90 M1 / 1 90

CCYM2J90 M2 / 1 90

CCYM3J90 V :joint M3 / 3 90

CCYM4J90 M4 / 3 90

CPM 1J90

IJ M1 / 1 90

CPM2J90 M2 / 1 90 U

CPM3J90 M3 / 3 90

CPM4J90 M4/3 90

*1 . U. Unlt, C. Concrete . M3. Mate rlal_3 of Jomt

M4: Material_4 ofjoint

32.4

41.0

44.2

36.7

44.9

44.6

36.6

30.8

5.6

22.0

27.8

37.9

27.7

32.3

32.0

54.3

28.6

37.6

49.4

46.3

3.4

15.3

21.0

52.6

41.1

50.1

53.8

33.4

28.5

34.4

35.2

*2 C: P iec8 H: Horizontal seUina: V: Vertical setting

V: Cylinder P : Prism *3 Joint angte from loading direction (degree)

*4 Compre ssive strength

- : Without joint

2.2. Joint materiais

Strength ratio

-

1.00

1.08

0.90

1.10

1.09

1.00

0.84

0.15

0.60

0.76

1.04

0.76

0.88

0.87

1.00

---

0.85

0.06

0.28

0.39

0.97

0.76

0.92

0.99

0.81

0.70

0.84

0.86

Table 3. Specimens and Results on Tensile Test.

J o int

Nsme of Bace material .1 material e 0", Strength

/ / '3 ratio spec lmens

Specimen shapes Joint ., ., thickness

mm de. N/ mm2

C t TUC U

2 - - 3.03

TUR U R - 3.47 1.00

TCR C - 3 .91 -

M3 Tensile - - 2.89 -TCRM3 splittine:

TCRM4 M4 teat - - 2.48 -

TURM1JO Ml / 1 O 5.14 1.48

TURM2JO M2 / 1 O 4.49 1.29

TURM3JO M3 /3 O 2.24 0.65

TURM4JO é M4/3 O 3.22 0.93

TURM1J45 Ml / 1 45 3.58 1.03

TURM2J45 t M2 / 1 45 1.68 0.48 U

TURM3J45 M3 / 3 45 3.25 0.94

TURM4J45 M4/3 45 2.70 0.78

TURM1J90 Ml / 1 90 3.93 1.13

TURM2J90 M2 / 1 90 4.00 1.15

TURM3J90 ll. :joint M3 / 3 90 3.62 1.04 ----TURM4J 90 M4 / 3 90 3.59 1.03

TCY C Y - 3.11 1.00

TM3Y M3 - 1.23 -TCYM1J45 M1 / 1 45 3.52 1.13

TCYM2J45 t M2 / 1 45 1.74 0.56

TCYM3J45 D M3 / 3 45 3.03 0.98

TCYM4J45 M4/3 45 3.20 1.03 C

90 3.37 TCYM1 J 90 W

Ml / 1 1.08

TCYM2J90 M2 / 1 90 1.80 0.58

TCYM3J90 M3 / 3 90 2.13 0.69

TCYM4J90 M4/3 90 2.47 0.79

*1 . U. Umt, C. Concrete . M3. Matenat 3 of JOlnt

M4: Material 4 of joint *2 C: Piece R: T ensile splittini' test Y: Cylinder

*3 Joint angle from loadinr direction (degree)

*4 T ensile stren(th

- : Without joint

In th is experiment, four kinds of materiais for joints were used, and each of them is practical for architecture and civil engineering works in Japan. However, they are not used for masonry joints.

Table 6 indicates the substance of these joints taken in the experiment. Both Ml and M2 are epoxide-resin adhesives. On the other hand, M3 and M4 are pre-mi­xed mortars that have already been compounded with cement, fine dried sand and additives, and they are used for tile works or as materiais for the finishes for reinforced concrete floors.

Table 4. Specimens and Results on Bending Test.

Name of B ace material _ I

specimens / $pecimen shapes .,

BUC C

"i3üCM1 ,j, 'ilUCi.12 U R BüCM3 -BUCM4 l:J. ·joint

BUH H

BüHMiJõ

W=J EiUHM2:iO U

~ BUHM4Jõ' BCG G

"B'C'GMiJõ' 'BCGM2Jo C •• ~ ~

"ii'êGM4Jõ . 1 . U. Umt, C. Concrete

*2 C: Piece H: Unit G: Be am

*3 Flexur.1 strength - :Withoutjoint

Mark af

Joint

mate ri al O' h Strength

I ratio Joint '3

thickness

mm N/ mm2

- 9.83 1.00

MI / I 5.32 0.54

M2 / 1 5.17 0 .53

M3 / 3 3.8 1 0 .39

M4 / 3 6. 15 0 .63

- 14.50 1.00

M I / I 11.57 0.80

M2 / I 13.60 0.94

M3 / 3 5.19 0 .36

M4 / 3 9.94 0.69

- 6.01 1.00

Ml / I 5.89 0.98

M2 / 1 4.16 0.69

M3 / 3 4.28 0.71

M4 / 3 4.28 0 .71

Joint fo r Use Materi.1

Materiais t hic kness

Ml Epoxide res ;n

I mm Adhesion of

Dne liquid type structural me mber

M2 Epo)l ide resin

Imm Inst alling st one

Dne liquid t ype

M3 Pre- mixed mortar

3mm J oint o n t il8 works

M4 Pre-mixed

3mm Finish of re inforced

mortar concrete s lab

Table 6. joint Materiais.

2.3. Method

Table 5. Specimens and Results on Shearimg Test.

Joint

Name of Bace mat erial _ I material e

/ specimens / Joiot

' 3

Specimen shapes .,

th icknes$

mm d ••

SUR R - -SURMIJO MI / I o SURM2JO M2 / 1 o SURM3JO M3 / 3 o SURM 4JO M4 / 3 o SURM1 J45

$ MI / I 45

SURM2J45 U M2 / 1 45

SURM3J45 M3 / 3 45

SURM4J45 M4 / 3 45

SURM 1J90 MI / I 90

SURM2J90 M2 / I 90

SURM3J90 M3 / 3 90

SURM4J90 6}oint M4 / 3 90

SCR C - -

SM3R M3 - -

SM4R M4 - -SUO U o - -

SCO C

<> - -

SM30 M3 - -SM320 M3 - -SM40 M4 - -

SUOFM1J45 DF MI / I 45

SUOFM2J45

<> M2 /1 45

SUOFM3J45 M3 / 3 45

SUOFM4J45 M4 / 3 45 U

~v SUOUMI J45 MI / I 45

SUOUM2J45 M2 / 1 45

SUOUM3J45 M3 / 3 45

SUOUM4J45 M4 / 3 45

SCG C G - -SCGMIJO 4- MI / I o SCGM2JO A M2 / 1 o

C SCGM3JO M3 / 3 o SCGM4JO M4 / 3 o *1 . U. Unrt.. C. Concre t e. M3. Matenat3 of JOlnt

M4: Materiat 4 of joint

O's Stre ngtJ .. ratio

N/ mm ,

5.24 I .OC

5.40 1.03

1.91 0.3E

1.90 0.3E

3. 14 0.6C

5.24 1.0C

2. 10 0.4C

4.29 O .8~

5.26 1.0C

4.85 O.9~

3.49 0.67

4.34 0.83

4.04 0.77

7.40 -7.21 -7.94 -5.23 I .OC

7.69 -8.44 -7.69 -9.84 -5.02 0.9E

2.79 0.5:1

4.73 0.9C

4.78 0.91

6.36 1.2~

2.63 0.5e

5.19 0.9\

6.30 1.2C

19.63 1.0C

17.09 0.87

3.53 O.I!

2.00 O.IC

2.79 O.1ol

. 2 R: Oirect shearing test O: Diagonal compressio n test

DF: ~ia gon al compression test (face shell)

UO: Oia&ona l compr-ession test (unit)

G: Oirect s hearing test on beam *3 Joi nt anete trom lo ading direc t ion (degree)

*4 She ar strength

- : Without ioint

This experiment was done as shown in Figure 2 in order to examine the intensity of joints when they were under four kinds of stress (compression, tension, bending, she­aring). As for the compression test, a method that adds stress to a specimen placed vertically (CUV) was adopted as well as methods based on jlS Uapanese Industrial Standard). Therefore, we can gain an advantage for a joint set at a 45-degree angle.

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Figure 4. Strength Ratio on joint Material (Compression Test).

1.2

1.0

~ 0.8

t 0.6 ~ ~ 0.4

0.2

0.0

1= - ~ ~ l-

~ ~ ~ l-

~ ~

Ml

OJoint angle : 45 1 090

= = -f:: = ::::: r- - = f:: = -= r- ::: = ~ ::::: = r- = =

r~ = = = :: M2 M3 M4 Joint Materiais

Figure 6. Strength Ratio on joint Material (Bending Test).

1.2 r-i-T,==:r:==:;-t 1.0 I---t---H

~ 0.8 I--:=::--If----+---+---j a: tO.6 ~ ~ 0.4

0.2

0.0

M1 M2 M3 M4 Joint Materiais

Figure 5. Strength Ratio on joint Material (Tensile Test) .

1.2

1.0

J 0.8

t 0.6 ~ ~ 0.4

0.2

0.0

r-= ::::: ::::: = = = :::: :::

M1

OJoint anslo: 45 090

-;::: = :::: ;:;:- ~ ;:: = ~

= f= -= = ::: ;:: :: f= ::: ::::: ::: ;:: = ::: = = = ::::: = ::::: - -

M2 M3 M4 Joint Materiais

Figure 7. Strength Ratio on joint Material (Shearing Test) .

1.2

1.0

J 0.8

~ 0.6

~ 0.4

0.2

0.0

f- ~

~

r

M1

8Joint ang1e: O 045 090

- -I"" ::: ::;-

r-- -

~ j -M2 M3 M4

Joint Materiais

About the tensile test, the tensile splitting tests (TCR, TUR) were adopted as well as direct tensile tests (TUC, TCY).

On the bending test, there are three kinds of methods, which consist of a piece cut out of a unit (BUC), and the utilization of a vertical line of a joint on a unit (BUH), and the beam-type mode of concrete (BCG).

As to the shearing test, there are two types of methods. One method is the direct type (SMR, SCR, SUR, SCG), and the other is the diagonal type. There are also two types of direct methods.

In the case of the coupon inside the circular apparatus, the test is done by exer­ting pressure to the circular apparatus (direct shearing test: SMR, SCR, SUR). And the other is the beam-type test (SCG).

There are two diagonal types. One is what is cut out of a unit's face shell (SUDF), and the other is what is piled from two units (SUDU). Figure 3 shows the direct method of the shearing test on a circular specimen.

Figure 4. 5trength Ratio on joint Material 1.2 (Compression Test).

1.0 fI+-+---t-----I ~ 0.8 c..... •..•• f-_ ..... t-i 0.6 '- !jli! f-f- !::~~ f-f- t~ -- :{ -~ 0.4 -::::: c-f- ::::; c-f- ::::: -- :;:;: -

0.2 - ~:m C-f- m~j e-~ i}. --}: c-

0.0 1......I--.:.s.....L.-.JI:.:.:"--"'--......... .I.....J-...... '"'--I

. ~ . ~ .. ·r .5; ., lO "O ., <: <: e .. li

., .... al .J:;

§ In

() Kinds of Stress

Figure 6. 5trength Ratio on joint Material (Bending Test) .

1.2 ..----,.-----,----r----,

1.0 1----+---+--- +------1

~ ~ ~

1 ~~ ~ I!!l ~~ llijl-=-+=-r-j-t--r-:.-J--I 0.0 ......., ...... L..-l ....... :':':O .............. ::';':O .............. ~....J

.~ <: .. .2 .k

Z! ., ""2

K li ., .... al

~ Kinds of Stress ()

3. RESUlTS

Figure 5. 5trength Ratio on joint Material

o ., ~

t <:

~

1.2 ( r-T_e_n_si_le_Tr-e_st-,-J_. -,...---,...-----,

1.0 I----t----t----t-----I 0.8

0.6

0.4

0.2

0.0

~~~1~:;}_r_--~--_4

~ :! :~i!: :=~~mt g

I ()

<: o .;;; <: .. ....

Kinds of Stress

Figure 7. 5trength Ratio on joint Material (5hearing Test).

1.2 ,..----r---,----r----,

.~ . ~ .~ .. <:

co '" "O ' 1: (I) <: <: tO

e li ., ~

~ .... al In

() Kinds of Stress

Table 2-5 shows the results from the compression test, the tensile test, the ben­ding test and the shearing test. Every value is the average of the three specimens. According to this, the compression strength of the unit without a joint shows 32.4-41.0N/mm 2

, and one with a joint (a 90-degree angle) shows 36.7-44.9N/mm 2

• On the other hand, the shearing strength of the unit without a joint is about 5.24N/mm 2

, shown in Table 5, and the one with a joint (a O-degree an­gle) of the circular specimen is 1.91-5.40N/mm2

•

4. CONSIDERATION

4.1. Strength Ratio

The strength ratio (the ratio of joint/no joint) on each test is shown in Table 7-14. The strength ratio is calculated from the standard intensity of the unit without a joint on each kind of specimen. If there are specimens, which have not the value

135

' 360

T bl e 7. Strenat a h RatlO on ComoresslOn Test. Specimen Joint Joint materiais

type angle Ml M2 M3 M4 MeG" CUV 45' 0.84 0.15 0.60 0.76 0.59

CY 45 ' 0.85 0.06 0.28 0.39 0.40

Mea" - 0.85 0.11 0.44 0.58 0.49

Table 8. StrenCjth Ratio on Compression Test. Specimen Joint Joint materiais

type angle Ml M2 M3 M4 Mea"

CUH 90' 1.08 0.90 1.10 1.09 1.04

CUV 90' 1.04 0.76 0.88 0.87 0.89

CP 90' 0.81 0.70 0.84 0.86 0.80

CY 90' 0.97 0.76 0.92 0.99 0.91

Me." - 0.98 0.78 0.94 0.95 0.91

Table 9. Strength Ratio on Tensile Test. Specimen Joint Joint materiais

type angte Ml M2 M3 M4 Mean

TUR 45' 1.03 0.48 0.94 0.78 0.81

TCY 4s" 1.13 0.56 0.98 1.03 0.93

Mean - 1.08 0.52 0.96 0.91 0.87

Table 7 O Strength Ratio on Tensile Test Specimen Joint Joint materiais

type angle Ml M2 M3 M4 Mea"

TUR 90' 1.13 1.15 1.04 1.03 1.09

TCY 90' 1.08 0.58 0.69 0.79 0.79

Mea" - 1.11 0.87 0.87 0.91 0.94

Table 77 Strength Ratio on Bending Test Specimen Joint Joint materiais

type angle Ml M2 M3 M4 Mea" BUC O· 0.54 0.53 0.39 0.63 0.52

BUH O· 0.80 0.94 0.36 0.69 0.70

BCG o' 0.98 0.69 0.71 0.71 0.77

Mean - 0.77 0.72 0.49 0.68 0.66

Table 72 Strength Ratio on Shearing Test. Specimen Joint Joint materiais

type angle Ml M2 M3 M4 Mea" SUR O· 1.03 0.36 0.36 0.60 0.59

SCG O· 0.87 0.18 0.10 0.14 0.32

Mea" - 0.95 0.27 0.23 0.37 0.46

Ta bl e 73. Strengt h RatlO on Sh eanng est. Specimen Joint Joint materiais

type angte Ml M2 M3 M4 Mean

SUR 45' 1.00 0.40 0.82 1.00 0.81

SUDF 45' 0.96 0.53 0.90 0.91 0.83

SUDU 45' 1.22 0.50 0.99 1.20 0.98

Me." - 1.06 0.48 0.90 1.04 0.87

Table 74. Strength Ratio on Shearing Test. Specimen

type SUR

Mea"

0.80

of the standard intensity, on the compression test, the strength ratio of CPM ty­pe is taken from CUH. Likewise, on the shearing test, the strength ratio of the SU­DU type is taken from SUD.

4.2. kinds of materiais for the joint and strength ratio

Figure 4-7 indicates the strength ratio of each test, in view of the kinds of mate­riais and the joint angle. The strength ratio in the Figures is taken from the ave­rage value of the strength value of the specimens with the same joint angle.

Figure 4 shows the strength ratio of the compression test. According to this, when the joint is at a 90-degree angle, its strength ratio is 0.78-0.98. But when it is at a 45-degree angle, the ratio becomes 0.11-0.85 . In other words, the spe­cimen with a 45-degree joint angle becomes smal ler. Especially, the strength ra­tio of M2 with a 45- degree angle is 0.11, and this is the smallest value throug­hout the examination.

The strength ratio of the tensile test is shown in Figure 5. This proves that the joint material of M1 makes the strength ratio larger, and M2 makes it smaller on every angle, the same as the compression test. In the case of a 90-degree angle, the ra­tio is 0.87-1 .11. On the contrary, when it is a 45-degree angle, the ratio is 0.52-1.08, and the strength ratio becomes much larger than that on the compression

test (under the same conditions of a 45-degree angle). Figure 6 indicates the strength ratio of the bending test. As for this test, the ratio is within the limits of 0.49-0.77 and the difference owing to the materiais is comparatively small.

The strength ratio of the shearing test is shown in Figure 7. Whatever angle it ta­kes, the same as other tests, Ml shows the largest value. That is within the limits of 0.92-1.06. M2, however, shows the smallest ratio . Particularly, when the angle is O-degrees, the ratio becomes 0.27, and this is a remarkably small value.

4.3. Kinds of stress and strength ratio

Figure 8-11 shows the strength ratio of the kinds of tests in view of classified ma­teriais (M1-M4). On the compression test, the strength ratio is taken from the ave­rage value of the specimens with a joint angle of 90-degrees (CUH, CUV, CP, CY) as shown in Table 8. On the tensile test, shown in Table 9, the ratio is taken from the average value of the specimens with a joint angle of 90-degrees (TUR, TCY).

In the bending test, shown in Table 10, the average value from the specimens (BUC, BUH, BCG) is taken. In the shearing test, shown in Table 11, the average value is taken from the specimens (SUR, SCG).

Regarding Ml, the strength ratio excludes the bending stress. But the strength ratio of M2 is within the limits of 0.27-0.87. Above ali, the ratio on the shearing stress becomes remarkably small .

In the case of re-mixed mortar M3 and M4, the ratio is within the limits of 0.23-0.94 shown in Tables 10 and 11. The same as M2, the ratio of the shearing stress becomes very small.

Considering ali of these figures, the strength ratio under the compression stress is within 0.78-0.98, and under the tensile stress, it is within 0.87-1.11. But under the bending stress, it is within 0.49-0.77, and under the shearing stress it is wit­hin 0.23-0.95. From these results, we can understand that the strength ratio de­pends very much on what kind of stress it is.

5. CONCLUSIONS

In this experiment, we have researched the strength of joints when they are gi­ven various stresses.

Then I have concluded as follows:

1 . Whatever stress was given, the epoxide material of Ml has the most satis­factory strength capacity (the average value of the strength ratio is within 0.77-1 .11).

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On the contrary, the epoxide material of M2 is inferior with every stress than Ml. 5till, it has good a quality in its deformation capacity.

50 it should be considered for more practical use.

On pre-mixed mortar, the average value of strength ratio is within 0.23-0.95, that is smaller than the epoxide material of Ml. Above ali, in case of the ben­ding stress and the shearing stress, there is big difference between Ml and two kinds of pre-mixed mortar.

2. The strength ratio of the joint is influenced considerably by the kinds of stress which are given. Especially, in case of the bending stress and the shearing stress, this becomes small.

3. The grading test for examining the strength capacity of joints should be mo­re general as well as the experiment which researches the unit's intensity.

And the compression test with a joint angle of 45-degrees (CUV _45) is surely regarded as the simplest and most effective method.

6. REFERENCES

1. M. NISHIYAMA, "Experimental Study on Bonding Factor of Masonry - Decrease Caused by Bonding on Shearing strength - ", Summaries of technical papers of annual meeting archi­tectural institute of JAPAN , 1998.pp.1 043,1044.