Paper: Strength and Deformation of Conﬁned Brick Masonry ...ares.tu.chiba-u.jp/peru/pdf/output/2014/Dr9-6-10-6903Sugano.pdf · Strength and Deformation of Conﬁned Brick Masonry

Sugano, S. et al.

Paper:

Strength and Deformation of Confined Brick Masonry WallsSubjected to Lateral Forces

– Review of Existing Test Data in Japan and Peru –Shunsuke Sugano∗, Taiki Saito∗∗, Carlos Zavala∗∗∗, and Lourdes Cardenas∗∗∗

∗Building Research Institute1 Tachihara, Tsukuba, Ibaraki 305-0802, Japan

E-mail: [email protected]∗∗Toyohashi Institute of Technology, Toyohashi, Japan

∗∗∗Centro Peruano Japones de Investigaciones Sısmicas y Mitigacion de Desastres (CISMID), Lima, Peru[Received August 11, 2014; accepted November 5, 2014]

The Japanese and Peruvian experimental databaseson confined brick masonry walls are put together asone database, and the strength and deformation of thewalls are reviewed. First, the applicability of existingequations for the ultimate strength of reinforced con-crete or reinforced masonry walls to the estimationof the maximum strength of confined brick masonrywalls which failed in shear, flexural-shear, or flexurewhen subjected to lateral forces, is discussed. Then,empirical equations for the maximum strength, dis-placement at maximum strength, and ultimate stateof the walls are proposed based on multiple regres-sion analysis, and the accuracy of the proposed equa-tions is discussed. It is concluded that the maximumstrength can be estimated using the existing equationsor the proposed empirical equations with good accu-racy. The deformations at maximum strength and theultimate state can be estimated using the proposed em-pirical equations, although there is a large amount ofscatter.

Keywords: confined masonry, test data, strength, defor-mation, lateral force, backbone model

1. Introduction

The Building Research Institute (BRI) of Japan hasbeen collecting research papers and test data on reinforcedmasonry (RM) and confined masonry (CM) walls from allover the world to propose a backbone model for the de-sign and analysis of masonry buildings subjected to lateralforces. The Centro Peruano-Japones de InvestigacionesSısmicas y Mitigacion de Desastres (CISMID) of Peru hasalso been collecting papers and test data on confined brickmasonry walls in Latin American countries for the samepurpose.

In this paper, the Japanese [1–3] and Peruviandatabases [4–6] on confined brick masonry walls (Figs. 1and 2) are put together and reviewed with respect to thefailure mode, the maximum strength, the deformations at

maximum strength, and the ultimate state of walls sub-jected to lateral forces.

This paper describes (1) the applicability of existingequations for the design and analysis of reinforced con-crete walls or reinforced masonry walls to the experimen-tal maximum strengths of confined brick masonry walls,(2) the factors that affect the strength and deformabilityof confined brick masonry walls, (3) multiple regressionanalyses of the maximum strength, the deformations atmaximum strength, and the ultimate states of walls.

2. Outline of Experimental Database

2.1. Japanese DatabaseSince 1992, the Chiba Institute of Technology, Building

Research Institute, Oita University, Akita University, theUniversity of Tokyo, Hokkaido University, and Mie Uni-versity have conducted tests on confined masonry wallsunder static cyclic loading. Among them, the test data ofBuilding Research Institute [1] and Oita University [2, 3]were selected as the database for the review in this studybecause (1) a large number of test specimens were in-cluded in a series of tests and (2) the effects of manystructural factors on the behavior of confined brick ma-sonry walls were studied.

There are 55 walls in total in the Japanese database,and the ranges of structural factors are as follows:prism compressive strength of brick masonry, Fm: 18.5–60.6 N/mm2; wall length l: 1,070–1,750 mm; wall thick-ness t: 100–183 mm; wall height h: 665–1,663 mm;shear span ratio, h/l: 0.52–0.95; column reinforcementratio, Pte: 0.05–0.67%; wall lateral reinforcement ratio,Pwe:0.00–0.64%; and axial stress, σ0: 0.39–1.37 N/mm2.

2.2. Peruvian DatabaseThe Peruvian database consists of the experimental

data on the 34 confined brick masonry walls tested inthe CISMID since 1993 [4–6]. The ranges of structuralfactors are as follows: prism compressive strength of

984 Journal of Disaster Research Vol.9 No.6, 2014


Fig. 1. Confined brick masonry walls in the test of BuildingResearch Institute in 1994 [1].

Column size:125 x 250 mm

Wall length:1,800 – 3,600 mm

Wall thickness115 – 250 mm

Wall height2,300 – 4,600 mm

Shear span ratio:0.92 – 1.44

Axial stress:0.18 – 0.61 N/mm2

Fig. 2. Confined brick masonry walls in the test of CISMIDin peru [4–6].

masonry, Fm: 2.2–29.8 N/mm2; wall length, l: 1,800–3,600 mm; wall thickness, t: 120–250 mm; wall height, h:2,300–3,450 mm; wall shear span ratio, h/l: 0.64–1.44;column reinforcement ratio, Pte: 0.05–0.20%; wall lateralreinforcement ratio, Pwe: 0.23–0.28%; and axial stress,σ0: 0.18–0.61 N/mm2.

3. Load – Deformation Relationship

In the review of the database, the envelope of hys-teresis curves of each wall tested was idealized into thefour-line backbone curve shown in Fig. 3. The curve hasthree breaking points where stiffness changes: the crack-ing point (C), yielding point (Y), and maximum strengthpoint (Max), and ultimate point (Ult). The ultimate pointis defined as the point where the strength decreases to 80%of the maximum strength. The yielding point is definedas the point where the observed strain at the flexural rein-forcement exceeds the yield strain or as the point wheresignificant change in stiffness is observed in the hysteresiscurves.

The failure mode of a wall which has failed in shearwithout yielding is defined as “shear failure” and is ab-breviated as “S” in this paper. The failure mode of awall which has failed in shear after yielding is definedas “flexural-shear failure” and is abbreviated as “FS.” Thefailure mode of a wall which has failed in flexure is de-fined as “flexural failure” and is abbreviated as “F.”

4. Application of Existing Equations

The applicability of existing equations for the designand analysis of reinforced concrete walls or reinforced

C

Ultimate

Shearforce

Displacement

Maximum Strength

Rmax Ru Drift angle

YieldingMaxY

Cracking Ult

20% Vmax

umax

Vmax

Vc

ycRyRc

Vy

Failure ModeC Y Max Ult Flexural Failure (F)C Max Ult Shear Failure (S)C Y Max Ult Flexural Shear Failure (FS)

Fig. 3. Backbone model of restoring force characteristics ofconfined brick masonry walls.

masonry walls to confined brick masonry walls is deter-mined by comparing the observed maximum strength tothe strength calculated using the equations.

4.1. Existing Equation for Ultimate Shear Strengthof Reinforced Concrete Shear Walls

For design and analysis of reinforced concrete shearwalls, the following equation is used to calculate the lowerboundary of the observed shear strength in tests.

Qsu1 ={

0.053 · p0.23te (Fm +18)

M/(Q · l)+0.12+0.85

√pwe ·σwy

+0.1σ0e} · te · j . . . . . . . . . . (1)

where te: wall thickness and te = Aw/l, Aw: section areaof wall, l: wall length, Pte: tensile reinforcement ratio(= 100at/(telw), unit %), at : section area of tensile rein-forcement (mm2), Fm: compressive strength of masonryprism (N/mm2), lw: wall effective length = 0.9l, Pwe: lat-eral reinforcement ratio (= aw/tes) (must be 0.012 whenit exceeds 0.012), aw: section area of a pair of lateral rein-forcements and s: its space, σwy: yield strength of lateralreinforcement (N/mm2), j: distance between centers oftensile and compressive stresses (= (7/8)lw), σ0e: aver-age axial stress of wall (N/mm2) (= Nw/Aw), Nw: axialforce acting on the wall (N), M/(Ql): shear span ratio= h/l, h: height of inflection (loading) point, which mustbe 1.0 when it is less than or equal to 1.0 and 3.0 when itexceeds 3.0.

Figure 4 shows the relationship between observedstrength and the strength calculated by Eq. (1), both interms of the average shear stress in N/mm2. Eq. (1) over-estimates the maximum strength for most shear failurewalls and overestimates more for all the flexural-shearfailure or flexural failure walls.

4.2. Equation for Shear Strength of Masonry WallsThe following equation has been proposed by the Ar-

chitectural Institute of Japan as the equation to use toevaluate the ultimate shear strength of reinforced masonrywalls subjected to lateral forces [8]. The equation is

Journal of Disaster Research Vol.9 No.6, 2014 985

Sugano, S. et al.

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2 2.5

Expe

rimen

tal V

alue

(N

/mm

2 )

Calculated Value (N/mm2)

Peru_FS

CM1_S

CM1_FS

CM1_F

jtplQM

FpQ eewywemte

su 0

23.0

1 1.085.012.0./

18053.0

CM1: Confined Brick Wall

Fig. 4. Evaluation of the maximum strength using existingequation for shear strength of RC walls.

based on tests conducted by Matsumura on hollow con-crete block walls [9].

Qsu3 ={

ku · kp

[0.76

h/d +0.7+0.012

]√Fm

+0.18γ ·δ√ph ·h σy ·Fm +0.2σ0

} · t · j (2)

where ku: reduction factor depending on masonry mate-rial (ku = 0.64 [8]), kp: 1.16p0.3

t (pt = 100at/(t ·d), unit%), h: height of inflection point×2, d: effective lengthof wall (= l0 − t/2), l0: wall length, t: wall thickness, at :section area of tensile reinforcements (mm2), Fm: com-pressive strength of masonry prism (N/mm2), γ: reductionfactor depending on reinforcement (γ = 0.6 [8]), δ : reduc-tion factor depending on loading condition (δ = 1.0 [8]),ph: lateral reinforcement ratio (= aw/ts), aw: section areaof a pair of lateral reinforcements and s: space of thepair of lateral reinforcements, hσy: yield strength of lat-eral reinforcement (N/mm2), σ0: average axial stress ofwall (N/mm2), Nw: axial force acting on the wall (N), andj: distance between centers of tensile and compressivestresses (= (7/8)d).

Figure 5 shows the relationship between observedmaximum strength in test and the calculated shearstrength using Eq. (2), where the strengths are expressedin terms of the average shear stress in N/mm2. It has beenobserved that Eq. (2) provides the average of the observedmaximum strength, though there is a significant amount ofscatter. It is interesting that Eq. (2) provides the averageof the test results of confined brick masonry walls despitethe fact that it is based on the test results from hollow con-crete block walls, another type of wall altogether.

4.3. Approximate Equation for Flexural StrengthThe following equation is used to approximate the ul-

timate flexural strength of reinforced concrete walls. Itis known that this equation predicts the ultimate flexural

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2 2.5

Expe

rimen

tal V

alue

(N

/mm

2 )


Peru_FS

CM1_S

CM1_FS

CM1_F

Number of specimen 91Mean Value 1.01Standard deviation 0.57Coefficient of variation 0.57

Fig. 5. Evaluation of the maximum strength using AIJ equa-tion for shear strength of hollow concrete block walls.

0

1

2

3

4

0 1 2 3 4

Expe

rimen

tal V

alue

(N

/mm

2 )


Peru_FS

CM1_S

CM1_FS

CM1_F

CM1: Confined Brick Wall

wwywytu

umu

lNaaMhMQ

5.05.0'/

1

11

Fig. 6. Evaluation of the maximum strength using the ap-proximate equation for ultimate flexural strength.

strength of walls well even though it is an approximateequation based on simple assumptions.

Qmu1 = Mu1/h′

Mu1 = (at ·σy +0.5aw ·σwy +0.5N) · lw . (3)

where Mu1: flexural strength of wall, h′: height of theinflection (loading) point, at : section area of tensile rein-forcement (mm2), σy: yield strength of tensile reinforce-ment (N/mm2), aw: section area of vertical reinforce-ments in the wall section (mm2), σwy: yield strength ofvertical reinforcements in the wall section (N/mm2), l:length of wall, lw: wall length ×0.9, and N: axial force(N).



0

0.1

0.2

0.3

0.4

0 0.05 0.1 0.15 0.2

u /

F m

0 / Fm

PeruCM1_SCM1_FSCM1_F

Fig. 7. Maximum strength vs axial stress ratio.

0

0.1

0.2

0.3

0.4

0 0.1 0.2 0.3

u /

F m

(Pte* y) / Fm


Fig. 8. Maximum strength vs flexural reinforcement.

Figure 6 shows the relationship between observedmaximum strength and the flexural strength as calculatedby Eq. (3). It has been observed that Eq. (3) well esti-mates the maximum strengths of flexural (F) or flexural-shear failure (F-S) walls, the behavior of which have beenaffected by flexure, while it overestimates the maximumstrength of shear failure (S) walls.

5. Analysis of the Maximum Strength

5.1. Factors Affecting the Maximum Strength

Figures 7 to 10 indicate the relationships betweenthe observed maximum strength and factors affectingit, i.e., the axial stress ratio (σ0/Fm), the amount offlexural reinforcement (Pteσy) normalized by the prismcompressive strength (Fm), the amount of lateral rein-forcement (Pweσwy) normalized by the prism compres-sive strength (Fm) and the margin of the shear strength,

0

0.1

0.2

0.3

0.4

0 0.2 0.4 0.6

u /

F m

(Pwe* wy) / Fm


Fig. 9. Maximum strength vs lateral reinforcement.

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2 2.5 3 3.5

u

Qsu1 / Qmu1


Fig. 10. Maximum strength vs margin of shear strength.

(Qsu1/Qmu1: shear strength calculated using Eq. (1) / flex-ural strength calculated using Eq. (3)). The observedmaximum strength normalized by the prism compres-sive strength τu/Fm increases with an increase in the ax-ial stress ratio σ0/Fm, the amount of flexural reinforce-ment Pteσy/Fm, and the amount of lateral reinforcementPweσwy/Fm. It decreases with an increase in the margin ofshear strength Qsu1/Qmu1.

5.2. Regression Equation for the MaximumStrength

A multiple regression analysis was done for the ob-served maximum strength of all test walls (89 walls) con-sidering the previously explained factors that affect it.The following empirical equations were then derived.

τu = 1.57+3.23Pwe ·σwy

Fm−11.52

σ0

Fm−0.31

Qsu1

Qmu1(4)

τu

Fm= 0.0038+0.26

Pte ·σy

Fm+0.14

Pwe ·σwy

Fm+0.89

σ0

Fm(5)


Sugano, S. et al.

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2 2.5

Expe

rimen

tal v

alue

(N

/mm

2 )

Calculated value (N/mm2)

Peru_FS

CM1_S

CM1_FS

CM1_F


Fig. 11. Evaluation of the maximum strength with the pro-posed regression equation.

0

0.1

0.2

0.3

0.4

0 0.1 0.2 0.3 0.4

Expe

rimen

tal v

alue

Calculated value

Peru_FS

CM1_S

CM1_FS

CM1_F


Fig. 12. Evaluation of the maximum strength using the pro-posed regression equation.

These equations globally predict the maximum strengthof the walls despite the failure mode. Other empiri-cal equations corresponding to each failure mode are de-rived, but they will be mentioned on another occasion.In Eq. (4), the maximum strength is expressed in termsof the average shear stress τu. The variables in the lin-ear equation were the amount of lateral reinforcement(Pweσwy) normalized by the compressive strength of ma-sonry prism (Fm), axial stress ratio (σ0/Fm), and the mar-gin of the shear strength (Qsu1/Qmu1). The correlationcoefficients of each factor to τu were 0.301, -0.509, and-0.490 for Pweσwy/Fm, σ0/Fm, and Qsu1/Qmu1, respec-tively. The strength calculated using Eq. (4) and that de-termined through tests are compared in Fig. 11. The co-efficient of variation (standard deviation / mean value) is28%, and 73% of the total number of walls are within 30%

error. The correlation coefficient R is 0.70.In Eq. (5), maximum strength is expressed in terms of

the average shear stress τu normalized by the compressivestrength of masonry prism Fm. The variables in the linearequation are the amount of lateral reinforcement (Pweσwy)and the amount of flexural reinforcement (Pteσy), respec-tively, normalized by the compressive strength of ma-sonry prism Fm and the axial stress ratio (σ0/Fm). Thecorrelation coefficients to τu/Fm were 0.667, -0.589, and0.411 for Pteσy/Fm, Pweσwy/Fm, and σ0/Fm, respectively.The strength calculated using Eq. (5) and that determinedthrough tests are compared in Fig. 12. The coefficient ofvariation is 28%, and 75% of the total number of walls arewithin 30% error. The correlation coefficient R is 0.97.

As shown in the figures above, these equations can pre-dict the maximum strength of walls well regardless oftheir failure mode.

6. Analysis of Deformation at the MaximumStrength

6.1. Distribution of Deformation at the MaximumStrength RRRmax

Figure 13 shows the distribution of the deformationat the maximum strength Rmax in terms of the cumula-tive probability Pc(Pc|R=Ri(%): Pc = Number of data|R≤Ri/ Total Number). The deformation Rmax in the Japanesedatabase (55 walls) ranges from 0.5 to 20 × 10−3 rad.while it ranges from 2.5 to 15×10−3 rad. in the Peruviandatabase (34 walls). However, the distribution curves aresimilar, both having an “s” shape.

Figure 14 shows the distribution of the deformation atthe maximum strength Rmax in terms of the probabilitydensity PD (probability density PD: PD|R=Rm (% per unitdrift angle R0) is the differential coefficient at R = Rmon the R−Pc curve). The deformation at the maximumprobable density differs in the Japanese and Peruviandatabases. The deformation at the most probable densityis 4× 10−3 rad. in the Japanese database while is larger,7×10−3 rad., in the Peruvian database.

For reference, the distribution of the deformation atthe maximum strength of reinforced concrete shear wallsis shown in Figs. 15 and 16. These data come from a1968 review by Tomii of 200 reinforced concrete shearwalls [10]. According to Fig. 15 which shows the cumu-lative probability of the deformation at maximum strengthRmax, the deformation ranges from 0.5 to 15× 10−3 rad.The distribution curve is s-shaped, similar to the curves ofconfined brick walls seen in Fig. 13. The probability den-sity of Rmax is shown in Fig. 16. The deformation at themaximum probability density, at the peak of the distribu-tion curve, is 4× 10−3 rad. (drift angle of 1/250). Sincethis figure was published, it has become well known thatthe deformation at the maximum strength of reinforcedconcrete shear wall is 4 × 10−3 rad. or 1/250. In thestandard for the seismic evaluation of reinforced concretebuildings, it is assumed that the shear failure member fails



0

20

40

60

80

100

120

0 5 10 15 20

P C(%

)

Rmax (10- rad)

Peru n=34

CM1 n=55

Fig. 13. Distribution of Rmax of confined brick walls.

0

5

10

15

0 5 10 15 20

P D(%

/10

rad

)

Rmax (10- rad)

Peru n=34

CM1 n=55

Fig. 14. Distribution of Rmax of confined brick masonry walls.

in shear at the deformation 4 × 10−3 rad. or 1/250 [7].This assumption is based on the distribution of Rmax inFig. 16.

6.2. Factors Affecting Deformation at the Maxi-mum Strength RRRmax

The multiple regression analysis indicates that the shearspan ratio (h/l) is the key factor in the deformation atmaximum strength. It shows that deformation increasesas the shear span ratio increases (Fig. 17). The correla-tion coefficient of Rmax and h/l are 0.214. The effects ofother factors are minor.

6.3. Regression Equations for Deformation at theMaximum Strength RRRmax

The following regression equation for the deformationat maximum strength Rmax is derived in terms of the shearspan ratio h/l.

Rmax = 0.41+5.7h/l (×10−3 rad.) . . . . (6)

Cumulative Probability Pc|R=Ri(%)Pc=No. of data|R Ri / Total No.

RC Shear Walls

Fig. 15. Distribution of Rmax of RC walls (after Tomii [10]).

Probability Density PDPD|R=Rm(% per unit drift angle R0) is thedifferential coefficient |R=Rm on R-Pc curve

RC Shear Walls

Fig. 16. Distribution of Rmax of RC walls (after Tomii [10]).

The comparison between the calculated deformation byEq. (6) and the observed deformation of Rmax is shown inFig. 18. The coefficient of variation to mean value is 77%,which is very large, and only 33% of the total number ofwalls are within 30% error. The correlation coefficient Ris 0.43. The range of shear span ratios is from 0.52 to2.09.

As indicated by these statistical values, the deformationat maximum strength can be evaluated using the empiricalequation above, but there is a large amount of scatter.

7. Analysis of Deformation at the UltimateState RRRuuu

7.1. Distribution of Ultimate Deformation RRRuuu

The distribution of the ultimate deformation Ru fromboth the Japanese and Peruvian databases is shown interms of the cumulative probability Pc in Fig. 19 and interms of the probability density PD in Fig. 20. The ulti-mate deformation Ru ranges from 1 to 19× 10−3 rad. inthe Japanese database and from 2 to 16× 10−3 rad. inthe Peruvian database. As seen in Fig. 19, the distributionforms “s” curves, as do those of Rmax in Fig. 13.


Sugano, S. et al.

0

5

10

15

20

0 0.5 1 1.5 2 2.5

R max

h/l


Fig. 17. Deformation at the maximum strength Rmax vsshear span ratio h/l.

0

5

10

15

20

0 5 10 15 20

Expe

rimen

tal v

alue

(x

10-

)

Calculated value (x10- )

Peru_FS

CM1_S

CM1_FS

CM1_F


Fig. 18. Evaluation of the displacement at the maximumstrength Rmax using the proposed regression equation.

The deformation at the maximum probability densityis 9 × 10−3 rad., which is 2.3 times the deformation atthe maximum probability density of Ru in the Japanesedatabase and 11×10−3 rad., which is 1.6 times the defor-mation at the maximum probability density of Ru in thePeruvian database.

7.2. Factors Affecting Ultimate Deformation RRRuuu

The relationships between observed ultimate deforma-tion Ru and the factors affecting it are shown in Figs. 21to 23. The observed ultimate deformation is affected bythe influencing factors as shown below.

It can be seen that the ultimate deformation Ru in-creases as the flexural reinforcement (Pteσy/Fm) increasesfor shear failure-type walls while it decreases for flexuralor flexural-shear failure-type walls (Fig. 21). It can also

0

20

40

60

80

100

120

0 10 20 30

P C(%

)

Ru (10- rad)

Peru n=34

CM1 n=54

Fig. 19. Cumulative probability of Pc.

g. 18 Distribution of Ru of Confined Brick Wa

0

5

10

15

0 10 20 30

P D(%

/10

rad

)

Ru (10- rad)

Peru n=34

CM1 n=54

Fig. 20. Probability density of PD.

be seen that Ru increases as the margin of shear strengthQsu1/Qmu1 increases (Fig. 22). The correlation coefficientof Ru and Pteσy/Fm is 0.187, and that of Ru and Qsu1/Qmu1is 0.138. The effect of axial stress ratio σ0/Fm is not clear(Fig. 23).

7.3. Regression Equation for Ultimate DeformationRu

The following linear regression equation for ultimatedeformation Ru is derived in terms of the amount of flex-ural reinforcement Pteσy/Fm, axial stress ratio σ0/Fm, andthe margin of shear strength Qsu1/Qmu.

Ru =7.32+30.92Pteσy

Fm−68.3

σ0

Fm+1.47

Qsu1

Qmu1

(×10−3 rad.) (7)

Deformation values calculated using Eq. (6) are shownin Fig. 24. The coefficient of variation to mean value is54%, smaller than that for Rmax, and 40% of the values for



0

10

20

30

0 0.1 0.2 0.3

R u

(Pte* y) / Fm


Fig. 21. Ultimate deformation Ru vs flexural reinforcement.

0

10

20

30

0 0.5 1 1.5 2 2.5 3 3.5

R u

Qsu1 / Qmu1


Fig. 22. Ultimate deformation Ru vs margin of shear strength.

0

10

20

30

0 0.05 0.1 0.15 0.2

R u

0 / Fm


Fig. 23. Ultimate deformation Ru vs axial stress.

0

10

20

30

0 10 20 30

Expe

rimen

tal v

alue

(x

10-

)

Calculated value (x10- )

Peru_FS

CM1_S

CM1_FS

CM1_F


Fig. 24. Evaluation of the ultimate deformation Ru using theproposed regression equation.

the total number of walls are within 30% error. The rangeof Pteσy/Fm is from 0.0055 to 0.29, that of σ0/Fm is from0.0 to 0.19, and that of Qsu1/Qmu1 is from 0.44 to 4.57.

8. Concluding Remarks

The results of tests on confined brick masonry walls inthe Japanese database (55 walls) and Peruvian database(34 walls) were reviewed as one group of 89 walls interms of failure mode maximum strength, deformation atmaximum strength, and ultimate deformation. Results ofthe review can be summarized as follows.

(1) Applicability of existing equations used to estimatethe maximum strength of confined brick masonry walls

The observed maximum strength of confined brick ma-sonry walls was much smaller than the shear strength cal-culated using the existing equation for the ultimate shearstrength of reinforced concrete shear walls.

The equation for the shear strength of hollow concreteblock walls proposed by the Architectural Institute ofJapan (AIJ) provided the average of the observed max-imum strength of confined brick masonry walls, thoughthe scatter of the evaluation was large.

The approximate equation for the ultimate flexuralstrength of reinforced concrete walls estimated the ob-served maximum strength of flexural or flexural-shearfailure-type of confined brick masonry walls well, but itoverestimated the maximum strength of the shear failuretype of confined masonry walls.

(2) Deformation of confined brick masonry walls

The deformation at the maximum strength of confinedbrick masonry walls was equal to or larger than that ofreinforced concrete shear walls (4× 10−3 rad.). The ulti-


Sugano, S. et al.

mate deformation was 1.6 to 2.3 times the deformation atmaximum strength.

(3) Multiple regression analysis and empirical equationsto estimate the maximum strength

The obtained empirical equation based on the multipleregression analysis of the maximum strength estimatedthe maximum strength of any type of failure mode of con-fined brick masonry walls with good accuracy and littleerror.

(4) Multiple regression analysis and empirical equationsused to estimate deformations

The empirical equations obtained, which were basedon the multiple regression analysis of the deformation atmaximum strength and ultimate deformation, did estimatethe deformations. However, as errors were large, the esti-mates were inaccurate.

AcknowledgementsThis study was conducted as a part of the research project “En-hancement of Earthquake and Tsunami Disaster Mitigation Tech-nology in Peru” supported by the Japan International CooperationAgency (JICA) and the Japan Science and Technology Agency(JST).

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[2] K. Yoshimura and K. T. Kim, “Experimental Study for Higher Seis-mic Performance of Confined Brick Masonry Walls,” Journal ofStructural and Construction Engineering, Architectural Institute ofJapan, No.571, pp. 169-176, Sept. 2003 (in Japanese).

[3] K. Yoshimura, K. Kikuchi, M. Kuroki, H. Nonaka, K. T. Kim,and A. Oshikata, “Experimental Study for Developing Higher Seis-mic Performance of Brick Masonry Walls,” Proceedings of the 13th

World Conference on Earthquake Engineering (13WCEE), Vancou-ver, Canada, August 2004.

[4] C. Zavala, P. Gibu, C. Homma, L. Chang, and G. Huaco, “Compor-tamiento Frente a Cargas Laterales de una Vivienda de Albanileriade Dos Pisos Mediante Ensayo en Linea,” Proceedings of the XIVCongreso Nacional de Ingenieria Civil – Iquitos, Peru, 2003 (inSpanish).

[5] C. Zavala, C. Homma, P. Gibu, and G. Huaco, “Sesimic Behavior ofTwo Stories Masonry Building,” Proceedings of Japan-Peru Work-shop on Earthquake Disaster Mitigation, Lima, 2005.

[6] R. Salinas, F. Lazares, “La Alnanilerıa Tubular y su Uso en Vivien-das en Zona Sısimicas,” Proc. of the Conferncia Internacianal enIngenieria Sısmica, Agost, 2007 (in Spanish).

[7] Japan Building Disaster Prevention Association, “Standard for Seis-mic Evaluation of Existing Reinforced Concrete Buildings, 2001and Guidelines for Seismic Retrofit of Existing Reinforced Con-crete Buildings, 2001,” English Version, 1st, January, 2005.

[8] Architecrural Institute of Japan, “Ultimate Strength and Deforma-tion Capacity of Buildings in Seismic Design (1990),” October,1990 (in Japanese).

[9] A. Matsumura, “Shear Strength of Reinforced Masonry Walls, Pro-ceedings of the 9th World Conference on Earthquake Engineering,pp. VI-121-126, Tokyo, Kyoto, 1988.

[10] M. Tomii and M. Takeuchi, “The Relations between the DeformedAngle and the Shearing Force Ratio (0.80 – 1.00) with Regard to200 Shear Walls,” Transaction of Architectural Institute of Japan,No.153, November 1968.

Name:Shunsuke Sugano

Affiliation:Visiting Research Fellow/Lecturer, Building Re-search Institute

Address:1-Tatehara, Tsukuba, Ibaraki, JapanBrief Career:1971- Joined Takenaka Corporation, Technical Research Laboratory2000- Professor, Hiroshima University2009- Visiting Research Fellow/Lecturer, Building Research InstituteSelected Publications:• S. Sugano (Ed.), “Seismic Rehabilitation of Reinforced ConcreteStructures,” International Publication Series 2 (IPS-2), American ConcreteInstitute, 2007.• S. Sugano, “Lessons on Seismic Rehabilitation of Reinforced ConcreteBuildings Learned from Recent Earthquakes,” Proceedings of theSymposium Honoring Jim Jirsa, American Concrete Institute, 2014.Academic Societies & Scientific Organizations:• Architectural Institute of Japan (AIJ)• Japan Concrete Institute (JCI)• American Concrete Institute (ACI)• Earthquake Engineering Research Institute (EERI)• Japan Association for Earthquake Engineering (JAEE)


Paper: Strength and Deformation of Conﬁned Brick Masonry ...ares.tu.chiba-u.jp/peru/pdf/output/2014/Dr9-6-10-6903Sugano.pdf · Strength and Deformation of Conﬁned Brick Masonry

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