IMPROVEMENT OF MASONRY STRUCTURESAGAINST SEISMIC FORCE
Khan Shahzada*Supervisor:

Dr. Tetsuro Goto**

MEE06013
ABSTRACTIn this paper, Plane and confined masonry specimens have been tested by Portable Structural
Testing Equipment (PSTE). The shear strength and tensile strength of unconfined masonryincreases by 1.34 times and 1.7 times respectively, using Plaster. Use of wire mesh and plasterin unconfined masonry increases the shear strength by 1.61 times and the tensile strength by 2.35.
Confinement increases the shear strength by 1.65 times and tensile strength by 3.05.
Confinement and plaster increases the shear strength by 1.79 times and the tensile strength by
3.35. Confinement with bamboo mesh and plaster increases the shear strength by 2.12 times andthe tensile strength by 4.05. Confinement with wire mesh and plaster increases the shear strengthby 2.73 times and the tensile strength by 5.40. Wall density ratio for confined masonry buildings inPakistan has been proposed for different zones and soil type.
Keywords: unconfined masonry, confined masonry, modulus of elasticity, tensile strength, Shear strength,PSTE, wall density ratio

INTRODUCTION
A major earthquake of magnitude 7.6 on Richter scale struck Northern parts of Pakistan and Kashmir onOctober 8, 2005. Due to the deadliest earthquake of this region, more than 73,000 people lost their lives,
80,000 were left injured, and 3.5 million people were left homeless (WB & ADB, 2005). Most of thecasualties were the direct result of buildings collapse, either partially or fully.
The Himalayan region is considered to have potential of creating an earthquake of magnitude 8.0and greater once every 100 years (W.F Chin, 2003). In the recent past, several earthquakes of moderatemagnitudes (i.e., Mw = 5.0 to 5.5) have struck northern parts of Pakistan. These earthquakes have provedthat the northern part of Pakistan is a seismically active area.
Among the natural disasters, earthquake might be infrequent but more destructive. It is notpossible to prevent this natural disaster but the losses can be mitigated. Buildings which are properly
designed and detailed on the basis of modern seismic building codes are less affected because thesebuildings dissipate energy through inelastic behavior. Improper design of buildings can make thesebuildings vulnerable to earthquakes. The enormous losses inflicted by the October 8, 2005 earthquake inNorthern Areas of Pakistan were mainly due to the fact that in the absence of a seismic building code, all
the buildings were either non-engineered or designed for gravity loads only.
* Lecturer Department of Civil Engineering N-W.F.P University of Engineering & Technology

Peshawar, Pakistan** National Institute of Land Infrastructure and Management Tsukuba, Japan1

This research aims to find the most important parameter of plane and confined brick masonry i-ecompressive strength, diagonal compression strength and shear strength. Portable Structural Testing
Equipment (PSTE), developed by Dr. Tetsuro Goto of National Institute for Land and InfrastructureManagement (NILIM) Japan, has been used for testing masonry performance against earthquake force. As
currently there is no enough experimental data available about various parameters for brick masonry work,
it is extremely useful to find out such parameters in quantifiable terms for earthquake resistant design, riskzoning and damage assessment of such structures.
DIAGONAL COMPRESSION TEST FOR MASONRY TENSILE STRENGTHP.Sheppard and S.Tercelj have performed diagonal compression test on masonry specimens with different
arrangements. The following equations have been used for tensile strength calculation of the masonry
specimen (P.Sheppard, 1980).

⎡
σ n = σ o ⎢− 1 / 2 +⎢⎣Eq. (1)σ o = 0.83

PA

σo= 0.55

PA

Eq. (3)σ n = 0.49

PA

Eq. (4)

τo =Where;2⎤⎛ τo ⎞⎜⎜1.5 ⎟⎟ + 0.25 ⎥ = 0.62σ o⎥⎝ σo ⎠⎦

1. 5

Eq. (2)A = x-sectional area of masonry wall (mm2), P = maximum applied Load on the specimen (N)σ0 = axial compression strength of masonry (N/mm2), τ0 = shear Strength of masonry (N/mm2)
σn = σt = tensile Strength of masonry (N/mm2)
0.49 = factor of stress reduction due to corner holding (determined from Finite elementanalysis)

Tensile strength and lateral resistance of masonry specimen
By considering the masonry wall as an elastic, homogeneous and isotropic structural element, the basic
equation for the evaluation of the shear resistance of plain masonry walls can be derived by taking into
account the assumptions of the elementary theory of elasticity (Miha Tomazevic, 2000).
Compression strength of the specimen is calculated by following equation.

σ c = σ o / 2 + (σ o / 2) 2 + (bτ ) 22Eq. (5)Tensile strength of the specimen is calculated by following equation.

σ t = −σ o / 2 + (σ o / 2) 2 + (bτ ) 2Eq. (6)Shear strength of the specimen is calculated by following equation.

τ = σ t / b σ o /σ t +1

Eq. (7)

The following equation is used for determining lateral resistance of plane masonry,H s , w = Awτ

Eq. (8)σtEq. (9)H s , w = Awbσo+1σtWhere,b = h/d,

Aw = d x t, and t = thickness of wall (mm), d = width of wall (mm)For lateral resistance of confined masonry specimen the following equation has been reviewed and used(Miha Tomazevic, 2000).

H s ,c =σ t Aw ⎡⎛Nw ⎞ ⎤⎟⎟ + 1⎥ + n.0.806d rv2⎢1 + C I2 ⎜⎜1 +CI b ⎢⎝ σ t Aw ⎠ ⎥⎦⎣f con f yEq. (10)By knowing the tensile strength of masonry specimens from laboratory tests, the lateral resistance ofspecimens has been calculated by using the equation (9) and equation (10).
Mechanical properties of materials
The material properties were determined and the results are given in the table as follows;
Table 2 Mechanical Properties of Materials
Material
Concrete
MortarBambooBrick unit
Compressive strength MPa)
27.3
21.53
NA
8.9
Tensile Strength (MPa)
2.56
2.2
234.5
NAModulus of Elasticity (GPa)19.36814.782
NANA
Failure pattern of masonry specimens
The following figures explain the failure pattern of masonry specimens.

3Brick Prism
2.43
NA28.182

Figure 1 Behavior of Specimen J10B after testing Figure 2 Behavior of Specimen J10B after testing

Figure 3 Behavior of Specimen J10BCTP after testing Figure 4 Behavior of Specimen J10BCWP aftertesting
Diagonal compression strength of masonry specimens
Seven types of different specimens were prepared and tested. In the specimen names J, stands forJapan, 10 for compressive strength of brick unit in MPa, B for brick, P for Plaster, W for wire mesh, C forconfined, T for Take (in Japanese) Bamboo, and W for wire mesh. Diagonal compression test of wall
specimens were performed by using PSTE. Test results are given in the table;
Table 3 Diagonal Compression Strength of Brick specimens
Sectional area ofMaximum
Diagonal Compression Strengthspecimen (A) (mm2)
Load (P) (KN)
= P/A(N/mm2)
J10B
48792
20.02
0.41
J10BP
71920
70.53
0.98
J10BWP
71920
97.25
1.35
J10BC
100920125.28
1.24
J10BCP
100920138.65
1.37
J10BCTP
100920166.35
1.65
J10BCWP
100920219.432.17
Result shows that a specimen with confinement and wire mesh gives higher value of diagonalcompression strength.
Specimen Designation

4Tensile strength of masonry specimens
Tensile strength has been calculated from Diagonal compression test by using Equation (4) andthe results are given in the table as follows;
Specimen Designation
J10B
J10BP
J10BWP
J10BC
J10BCP
J10BCTP
J10BCWP

Table 4 Tensile strength of masonry specimens
Maximum
Sectional area ofLoad (P) (KN)
specimen (A) (mm2)
48792
71920
71920
100920100920100920100920

20.02
70.53
97.25
125.28138.65166.35219.43Tensile Strength
σt = 0.49P/A(N/mm2)
0.20
0.34
0.47
0.61
0.67
0.81
1.08

Test results shows that application of plaster, confinement, Bamboo and chicken mesh increases
the Tensile strength of brick masonry specimens.
Shear strength of masonry specimens
Shear strength has been calculated by using Equation (2) and Equation (7); where b = 1 for h/l =1 and the results are given in the table as follows;
Specimen Designation
J10B
J10BP
J10BWP
J10BC
J10BCP
J10BCTP
J10BCWP

Table 5 Shear strength of masonry specimens
σt = 0.49P/A
Compression Strength(N/mm2)
σ0 = 0.83 P/A (N/mm2)
2.02
0.20
2.02
0.34
2.02
0.47
2.02
0.61
2.02
0.67
2.02
0.81
2.02
1.07

Shear Strength (τ)(N/mm2)
0.67
0.90
1.08

1.11
1.20
1.42
1.83

Test results shows that shear strength of brick masonry increases with Plaster, chicken mesh,confinement, Bamboo and Chicken mesh.
WALL DENSITY RATIO FOR BUILDINGS IN PAKISTAN
There are no rules and regulations for wall density ratio of confined masonry structures in Pakistan. To
have safe masonry structures against earthquake, wall density ratio for masonry structures is of prime
importance. On comparing with the seismicity of different zones of Peru and the corresponding wall
density ratio of each zone the following wall density ratios are proposed for confined masonry buildings inPakistan (UNI, March, 2004).

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Table 6 Wall Density ratio for confined masonry buildings in Pakistan
Soil Type
Zone-I
Zone-II
Zone-III
Zone-IV
S1
3%
1%
1%
1%
S2
3%
2%
2%
1%
S3
4%
2%
2%
1%
Damage level
Very high hazard
High hazardModerate hazard
Low hazard
CONCLUSIONS

From test results which were carried out to determine the Diagonal compression strength, shear
strength and tensile strength of different specimens the following conclusions are made.
1.
The shear strength and tensile strength of unconfined masonry increases by 1.34 times
and 1.7 times respectively using Plaster.
2.
Use of wire mesh and plaster in unconfined masonry increases the shear strength by 1.61
times and the tensile strength by 2.35.
3.
Confinement increases the shear strength by 1.65 times and tensile strength by 3.05.
Confinement and plaster increases the shear strength by 1.79 times and the tensile4.
strength by 3.35.
5.
Confinement with bamboo mesh and plaster increases the shear strength by 2.12 times
and the tensile strength by 4.05.
6.
Confinement with wire mesh and plaster increases the shear strength by 2.73 times andthe tensile strength by 5.40.
7.
Wall density ratio for confined masonry buildings in Pakistan has been proposed.
ACKNOWLEDGEMENT
I would like to express my sincere gratitude to the advisor Dr. Taiki Saito for his continuous support,
valuable suggestion and guidance during my study. I am grateful to Engr. Amjad Naseer AssistantProfessor Department of Civil Engineering University of Engineering and Technology, Peshawar, forsending me a lot of information from my country regarding masonry construction, his confidence andsupport.

REFERENCES
Miha Tomazevic, 2000 “Earthquake-Resistant Design of Masonry Buildings” Series on innovation inStructures and Construction-Volume-1, Imperial College London.
P.Sheppard and S.Tercelj P, 1980 “The Effect of Repair and Strengthening Methods for Masonry Walls”,
7 WCEE, Istanbul, pp 255-262.
UNIVERSIDAD NACIONAL DE INGENIERIA (UNI), March 2004, MASONRY CONSTRUCTIONGUIDE Lima-Peru.
WB & ADB report, Nov 2005.
W.F.Chin & Charles Scawthorn, 2003 “Earthquake Engineering Hand Book”, CRC 2003, pp 2-5.

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