Journal of Natural Disaster Science, Volume 23, Number 2, 2001, pp53-63

Damage to Masonry Buildings
Caused by the El Salvador Earthquake of January 13, 2001
Koji YOSHIMURA and Masayuki KUROKI
Department of Architectural Engineering, Oita University,(Received for 10 Sep., 2001)

ABSTRACT
Based on a field investigation conducted in the Republic of El Salvador, damage done to buildings by the El
Salvador Earthquake of January 13, 2001 is briefly discussed. Special emphasis is placed on the damage to theun-reinforced adobe and brick buildings.

1. INTRODUCTION
On January 13, 2001, an earthquake of Magnitude Mw=7.7
occurred in the Republic of El Salvador in Central America. As of
the 13 February 2001, the death toll was 844, 4,723 people were
injured, and more than 75,000 houses were totally destroyed.
These damage statistics are based on information provided by the
National Emergency Committee (CDEN), El Salvador (El Diariode Hoy de El Salvador, 2001; La Prensa Grafica, 2001).
We arrived in San Salvador, the capital of the Republic of El
Salvador, on February 9, 2001 to investigate structural damage tothe buildings caused by this earthquake and spent five days, mainlyin the most severely damaged areas of El Salvador. Non-damagedbuildings also were investigated in downtown, San Salvador City
on the last day before our leaving El Salvador on February 13,
2001.
Since early 1990s when one of us (Yoshimura, K.) attended
the International Cooperation Project at the National Center for
Disaster Prevention (CENAPRED) in Mexico City, a number ofexperimental and field investigations have been conducted in the
Structural Engineering Laboratory of Oita University to develop
much higher seismic performance of un-reinforced and confined
masonry wall buildings for use in developing countries prone toearthquakes (Camacho et al., 1993, 1994; Yoshimura et al., 1995,
1996; Liu et al., 1997; Yoshimura et al., 1998, 1999a, 1999b,
1999c; Kagami et al., 1999; Yoshimura et al., 2000a, 2000b). The
main objective of this reported field investigation was to collectgeneral information about damage done to the masonry structuresby the El Salvador Earthquake of January 13, 2001.
2. RECENT SEISMIC ACTIVITY IN EL SALVADOREl Salvador is located on the western border of the Caribbean
Plate. The Cocos Plate subducts under the Caribbean Plate, which
is one cause of seismic activity in El Salvador. The other maincause of Salvadorian earthquakes, are the active volcanoes along
the volcanic belt running from Guatemala to Costa Rica, that haveproduced much extensive earthquake damage in El Salvador(Lopez, 1999).
From 1965 through 1999, the most significant earthquakesthat occurred in El Salvador were the 1965, 1982, and 1986 ones
with respective Richter Magnitudes of Ms=6.0, 7.2, and 5.4, andrespective maximum ground shaking intensities in San Salvador
City of MM=VIII, VII, and VIII on the Modified Mercalli Scale(EERI and IAEE, 2001). The 1965 earthquake, whose epicenter
was 10 km from San Salvador and 8 km deep, caused severe damage and killed 120 people. The epicenter of the 1982 earthquake
was approximately 60 km southeast of San Salvador at a depth of
80 km. It killed eight people and damaged 1,630 houses.
Although the 1986 earthquake had the smallest magnitude,
Ms=5.4, of the three earthquakes, about 1,500 people were killed,
7,000 to 10,000 injured, and 100,000 affected by it. Its epicenter
was just south of San Salvador at a focal depth of less than 8 km
(Castillo, 1994).
3. SEISMIC AND STRUCTURAL DESIGN STANDARDSIN EL SALVADOR
After the 1965 El Salvador earthquake, the government published the first seismic design code January 21, 1966 (Official
Report of the Republic of El Salvador, 1996), which was a modification of the seismic code of the city of Acapulco, Mexico. Afterthe 1986 earthquake, the Association of Engineers and Architects
in El Salvador (ASIA) published "Emergency Regulations for
Seismic Design in the Republic of El Salvador", which was an
improved and extended version of the 1966 code. Based on theseregulations, another revised edition of the seismic design code waspublished in 1989 (Association of Engineers and Architects in El
Salvador, 1989). The present seismic design standard was published in 1997 (Ministry of Public Works, 1997). Table 1 shows
the design base shears prescribed in those three seismic designcodes in El Salvador (Gracia, 1996).
In addition to the current seismic design standard, El Salvador
has eight technical standards: design for wind-pressure, the design

KEY WORDS: El Salvador earthquake, structural damage, masonry buildings, adobe houses, confined masonry walls

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K. YOSHIMURA AND M. KUROKI

and construction of concrete, steel, masonry and timber structures,the design of foundations, slope-stability, quality control of structural materials, and a special standard for the design and construction of houses.
4. STRUCTURAL SYSTEMS IN USE IN EL SALVADOR
Before the 1965 earthquake, the most frequently used methodof house construction in El Salvador was the timber, bamboo andmud wall construction called bahareque, in which mud walls were
reinforced by cane, wooden plates, boards, and/or bamboo connected to each other by nails and finished with lime mortar. Fromthe early "1940s to mid-1960s", buildings of three- to eight-stories
were constructed using a structural system consisting of concrete
frames and masonry walls, which was believed to automaticallyincrease structural safety. During the 1986 earthquake, however,
severe structural damage occurred to buildings constructed by thismethod. The bahareque and simple adobe brick (or dried claymud brick) construction method are still used in El Salvador, andin most inland cities many houses are still constructed using these
simple mud wall technique. Photos 1 and 2 show a mixed timber,bamboo, and mud wall house under construction in an inland cityduring our field investigation.

Table 1.

Use of reinforced masonry walls now is more popular for construction of residences. Photos 3,4, and 5 show reinforced masonry walls, called "confined masonry wall", under construction, eachwall being confined by slender reinforced concrete (R/C) columns
and beams. This type of reinforced masonry wall is frequently
used in house construction. Photos 6,7, and 8 show another type ofreinforced masonry wall under construction. For buildings of threestories or more, reinforced concrete (R/C) frame systems usuallyare used. Dual systems consisting of frame and concrete wall nor
steel frame systems are not common.
5. BRIEF DESCRIPTION OF THE EARTHQUAKEThe main shock of this earthquake occurred at 17:33,
Saturday the 13th of January 2001. Its Magnitude was Mw=7.6.
The epicenter, 100 km southwest of the city of San Miguel, El
Salvador, was located off coast of Central America (Figure 1).
The depth of the main shock was 39 km based on information provided by the USGS National Earthquake Information Center[http://neic.usgs.gov/neis/bulletin/01-EVENTS/010113173329/
zoom-in.html].
During the main shock, a number of earthquake accelerograms were recorded by the University of Central America. Of

Design base shears in the 1966, 1989, and 1997 El Salvador seismic design codes.

DAMAGE TO MASONRY BUILDINGS CAUSED BY THE EL SALVADOR EARTHQUAKE OF JANUARY 13, 2001

Photo 1.

A mixed timber, bamboo, and mud house under construction in La Paz Province.

Photo 5.

A confined masonry wall house under construction in
Usulutan.

Mud filling work in the house in Photo 1.

Photo 6.

A reinforced masonry wall supermarket under construction in Santa Ana Province.

Photo 3.

A confined masonry wall house under construction in
La Paz Province.

Photo 7.

Reinforcing details of a masonry wall in the buildingin Photo 6.

Photo 4.

Reinforcing details of a confining column in thebuilding in Photo 3.

Photo 8.

Reinforcing details of a column in the building in
Photo 6.

Photo 2.

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K. YOSHIMURA AND M. KUROKI

these, the respective peak accelerations in the E-W and N-S directions that were recorded at the ULLB (La Libertad) Station about
75 km northwest of the epicenter were 531, and 876 cm/sec2. The
peak acceleration in the U-D (Vertical) direction, recorded at the
USPN (San Pedro Nonualco) Station, was 428 cm/sec2 (Seo,2001). These values, the maximum recorded accelerations
obtained for this earthquake, will soon be published officially.
Sawada et al. (2001) noted that the very short period componentsof the recorded ground acceleration were prominent. The vibration
characteristics indicate that soil structures and low-rise buildings
with short vibration periods were affected severely by this earthquake in comparison to high-rise building structures.
Preliminary maximum intensities of ground shaking in Central
America during this earthquake have been reported by the
Seismological Center of Central America (CASC). According tothat report, the maximum ground shaking intensity in the coastal

area of El Salvador, near the epicenter, was MM=VIII and in mostcities of El Salvador MM=VII (Sawada et al., 2001).
According to the newspaper of February 13, 2001 and theweb-site information of February 21, 2001 (source the National
Emergency Committee (CDEN), El Salvador), the total number ofdead was 844, 4,723 people were injured, 74,955 houses weretotally destroyed, and 318 churches and 639 public buildings weredamaged (El Diario de Hoy de El Salvador, 2001; La Prensa
Grafica, 2001). Table 2 gives the damage statistics for this earthquake, the official information published by the government of the
Republic of El Salvador on January 25, 2001.
Characteristic of this earthquake was the large number oflandslides (see Photos 9 and 10). Of those landslides, the one at
Santa Tecla, La Libertad Province was the worst, more than 400 of
the 687 people in the Las Colinas district having been killed(Time, 2001).

Fig. 1 Epicenter location and areas visited.

Table 2.

Damage statistics (http://www.terremoto.gob.sv/informacion General/Cifras.htm).

DAMAGE TO MASONRY BUILDINGS CAUSED BY THE EL SALVADOR EARTHQUAKE OF JANUARY 13, 2001

6.

FIELD INVESTIGATION

Field reconnaissance in the areas severely damaged by thisearthquake was conducted for five days, from the 9 through 13
February 2001. The solid circles in Figure 1 show the cities visited. They are located mainly along the Pacific Coast of El
Salvador. Of the Provinces visited, Usulutan, La Libertad, and La
Paz were the most severely damaged by this earthquake (Table 2).
7.

DAMAGE TO MASONRY BUILDINGS

7.1 Adobe construction (Photos 11-21)
One of the most severely damaged structural systems used in

Photo 9.

A landslide in Santa Tecla.

Photo 10.

A landslide between San Salvador and Santa Ana.

Photo 11.

Damage to an adobe house in Santiago Nonualco.

Photo 12.

Vertical crack at the corner of an adobe wall in
Usulutan.

Photo 13.

Failure of an adobe house in San Pedro Nonualco.

Photo 14.

Damage to an adobe house in Maria Otsuma.

Photo 15.

Inside of the house in Photo 14.

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K. YOSHIMURA AND M. KUROKIEl Salvador was that of adobe construction, in which dried claymud brick units only are used to erect most walls, very little wall
reinforcement being provided in most of them. Photos 11 through20 show the typical damage done to this type of construction usedin residences, churches, and school buildings. Vertical cracks inwall edges at intersections in the plan were presented in most of
the damaged buildings. Photo 21 shows an example of a displaced
block of adobe bricks 30 cm x 23 cm x 7 cm.
7.2

Mixed timber, bamboo, and mud wall housing (Photos
22-24)The other structural system seen in the most severely damagedbuildings is based on a timber wall construction method. This is a

Photo 16.

Photo 19.

Damage to an adobe church in Zacatecoluca.

Damage to an adobe store in Santa Tecla.

Photo 20.

Damage to an adobe school in Usulutan.

Photo 17.

Damage to another adobe store in Santa Tecla.

Photo 21.

Adobe blocks in San Pedro Nonualco.

Photo 18.

Damage to an adobe church in Maria Otsuma.

Photo 22.

Damage to a mixed timber, bamboo, and mud wallhouse in Santa Tecla.

DAMAGE TO MASONRY BUILDINGS CAUSED BY THE EL SALVADOR EARTHQUAKE OF JANUARY 13, 2001

Photo 23.

Damage to another mixed timber, bamboo, and mudwall house in Santa Tecla.

Photo 24. Damage to a mixed timber, bamboo, and mud wallschool in Usulutan.

Photo 25.

Damage to an un-reinforced masonry wall church in
San Pedro Nonualco.

Photo 26.

Slight damage to an un-reinforced masonry wall
church in Santa Ana.

Photo 27.

Photo 28.

Forming clay bricks at the factory in Photo 27.

Photo 29.

Photo 30.

A clay brick factory in Maria Otsuma.

Hearth furnace in the factory in Photo 27.

A three-story confined masonry wall house in
Zacatecoluca.

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K. YOSHIMURA AND M. KUROKI

traditional wall structure used in house construction in various
Latin American countries. The structural (and/or partition) walls
are composed of timber frames and/or bamboo (quincha in
Spanish) with mud or clay filler combined with chopped straws (orwhole canes in some cases), and a plaster finish. Photos 22
through 24 show the damage typical to the mixed timber, bamboo,
and mud wall type of housing. The crushed mud walls have collapsed causing acute inclination of the building in some cases. A
main cause of this type of severe structural damage is the lack ofadequate wall strength in both the in- and out-of-plane directions.

wall structural system widely used throughout the world. Most of
the structural and non-structural walls are built of clay bricks andmortar. No wall reinforcement (such as steel reinforcing bars) is
provided within the walls in either the horizontal or vertical direction. Because these brown clay bricks usually are fired at a relatively low temperature, excellent mechanical properties such as
high compressive strength can not be obtained (Photos 27, 28 and
29). Although no severe structural damage to the many buildings
constructed by this structural system was observed, some church
buildings showed damage; bell towers and spires cantilevered at
the tops of the buildings cracked and totally collapsed.

7.3 Un-reinforced masonry churches (Photos 25, 26)
The un-reinforced masonry wall system is a popular, boxed-

Photo 31.

Photo 32.

A confined masonry wall house in Usulutan.

Photo 34.

A confined masonry wall house in Santa Tecla.

A two-story confined masonry wall house in
Usulutan.

Photo 35.

A confined masonry wall house in San Pedro
Nonualco.

Photo 33. A two-story confined masonry wall house in Santa
Tecla.

Photo 36.

Damage to a confined masonry wall house in San
Pedro Nonualco.

DAMAGE TO MASONRY BUILDINGS CAUSED BY THE EL SALVADOR EARTHQUAKE OF JANUARY 13, 2001

7.4 Reinforced masonry buildings (Photos 30-38)
The reinforced masonry system is a typical masonry wall
structural system widely used throughout Latin America andsoutheast Asia for low- and medium-rise houses and/or other kindof residential buildings. In this system, cast-in-place, slender R/Ccolumns are presented at most of the extreme edges and intersections of the masonry walls. In addition, cast-in-place R/C collar
beams, wall girders, or floor slabs usually are placed along the topof each masonry wall. In most cases, longitudinal Re-bars andhoops are installed in the R/C columns before the masonry wall
units are placed within the wall plane. After the brick or block
masonry units are connected with mortar to a height of a half or

one story, the concrete columns are cast, then the R/C collar
beams, wall girders, or floor slabs are constructed using cast-inplace concrete after all the masonry walls and R/C cast-in-placecolumns have been completed. Four longitudinal Re-bars usuallyare placed in each R/C column section. This type of construction
is called "confined masonry walls" in Latin American countries.
Photos 3, 4, and 5 show confined masonry walls under construction, at the time of our field investigation.
A large number of the buildings of confined masonry wallconstruction exist in El Salvador, but most were not severely damaged during the earthquake (Photos 30 through 35). A few, rarecases of damage to confined masonry buildings (Photos 36, 37,

Photo 37. Failure of a hollow concrete-block masonry wall in
the house in Photo 36. The hollow concrete blockunits are separated from the R/C confining column.

Photo 40.

Failure of an adobe garden wall in San Pedro
Nonualco.

Photo 38.

Photo 41.

An un-reinforced masonry garden wall in San
Salvador (no damage).

Photo 42.

An un-reinforced masonry garden wall in San
Salvador (no damage).

Damage to a confined clay-brick masonry wall in
Usulutan.

Photo 39.

Damage to an adobe garden wall in Usulutan.

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K. YOSHIMURA AND M. KUROKI

and 38) show where hollow concrete block walls and clay masonrybrick walls were severely damaged. In the building in Photo 37, a
concrete block masonry wall has separated into parts due to shear
cracking, and part of the wall has separated from its adjacent R/C
confining column and overturned in the out-of-plane direction.
Also, shear cracks formed in the clay brick masonry walls of thebuilding in Photo 38 have penetrated the R/C confining columns.
This damage seems to have been caused by pounding from a collapsed building (upper right in Photo 38) rather than by groundshaking.
7.5 Masonry garden walls (Photos 39-46)
A large number of masonry garden walls have been constructed of adobe, clay brick, or hollow concrete blocks throughout thiscountry. Except for many built of adobe, most walls were notseverely damaged. It should be noted that in El Salvador verticalwall reinforcements 40 cm apart are presented in most masonrygarden walls comprised of hollow concrete block units. Damage
to adobe garden walls consisted of sloughing off of finishes andthe toppling of adobe blocks (Photos 39 and 40).
8.

CONCLUDING REMARKS

Although a large number of buildings were damaged during
the El Salvador earthquake of January 13, 2001, most human damage was caused by the total or partial collapse of relatively lowrise, boxed-wall buildings; in particular, one- and two-story houses

constructed of un-reinforced dried clay-mud adobe or of timber
and/or bamboo walls filled with clay-mud. In addition, because
most existing buildings in El Salvador are one- and two-story residences constructed of un-reinforced adobe masonry or of timber
and/or bamboo walls, damage description mainly has been focusedon these most popular low-rise types of houses.
In most of the severely damaged adobe and timber and/or
bamboo wall houses, none of the vertical wall-edges at L-, T-, and＋ - shaped intersections of the construction were connected toeach other because no wall reinforcement is provided there. As aresult, each wall behaved independently in the out-of-plane direction during the earthquake. Some walls separated from the adjacent walls at their vertical connections and overturned in the outof-plane directions, or collapsed, resulting in severe structural
damage. This means that, as these types of wall structures without
adequate wall material strength, can not retain their original boxedwall shapes during strong-motion earthquakes, considerable severe
structural and human damage can be expected to occur again andagain during future earthquakes.
In the this type of the boxed-wall structure, the vertical edge
faces between adjacent walls, as well as the horizontal edge faces
between the walls and adjacent strong collar beams must be firmly
connected. Once this type of building is designed and constructedso as to retain its original box-shape configuration, each wall canbe expected to develop in-plane anti-seismic capacity.

Photo 43.

A confined masonry garden wall in Zacatecoluca(no damage).

Photo 45.

A reinforced masonry garden wall in Santa Tecla(no damage).

Photo 44.

A confined masonry garden wall in Usulutan (nodamage).

Photo 46.

A reinforced masonry garden wall in Santa Tecla(no damage).

DAMAGE TO MASONRY BUILDINGS CAUSED BY THE EL SALVADOR EARTHQUAKE OF JANUARY 13, 2001

ACKNOWLEDGMENTS
All the investigations done were made possible through thekind cooperation of Mr. Tomás A. Sánchez of the National Center
for Disaster Prevention, Mexico (CENAPRED). We thankProfessor Takeshi Mikumo of National Autonomous University of
Mexico (UNAM), Professor Patricia Alarc of Michoacan
University, Mexico, and Professor Kazuoh Seo of the Tokyo
Institute of Technology for their kind advice on and information
given for our study. We also are grateful to Mr. Jose Amilcar
López, a taxi driver in El Salvador City, Mr. Ange Lara of the
National Civil Police, El Salvador, and Ms. Maria Teresa Arbiw of
the Camino Real Intercontinental Hotel, San Salvador for theirkindness to us during our field investigation.
REFERENCES
Association of Engineers and Architects in El Salvador (ASIA), 1989.
Emergency Regulations for Seismic Design in the Republic of El
Salvador (in Spanish).
Camacho, O., Yoshimura, K., Kikuchi, K., Takano, K. and Sánchez, T. A.,
1993. Experimental study on confined concrete masonry walls, Proc.
of 4th East Asia-Pacific Conference on Structural Engineering &Construction, 619-624.
Camacho, O., Sueoka, T., Yoshimura, K. and Shirahama, T., 1994.
Analytical study on seismic behavior of confined concrete masonrywall, Trans. of Japan Concrete Institute, Vol. 16, 241-248 (inEnglish).
Castillo, H. D. A., Calvo, N. J. A. and Guerra, S. W. M., 1994. Evaluationof response spectra for design of structures in El Salvador, Universityof Central America (in Spanish).
EERI and IAEE, 2001. Encyclopedia of Housing Construction Types in
Seismically Prone Areas of the World, Compact Disk.
El Diario de Hoy de El Salvador, 2001. Earthquake in image, EARTHQUAKE 7.9(http://www.elsalvador.com/noticias/terremoto/cifras.html) (inSpanish).
Kagami, H., Ueda, Y., Sato, H., Taniguchi, H., Ishiyama, Y., Yoshimura,K., Nishigami, K. and Hayashi, H., 1999. Reconnaissance Report on
the 1999 Quindio, Central Western Colombia, Earthquake and its
Disasters, No. 10400018, Report supported by the Ministry of
Education of Japanese Government (in English).
La Prensa Grafica, February 13, 2001 (in Spanish).
Liu, L., Kajiwara, K., Yoshimura, K., Kikuchi, K. and Sánchez, T. A.,
1997. Effect of applied lateral forces and wall reinforcement on seismic behavior of confined concrete masonry walls, Proc. of 11th
International Brick/Block Masonry Conference, 585-594.
Lopez, M. A. M, 1999. Standards for earthquake-resistant design and construction in El Salvador, Country report presented to the National
Center for Disaster Prevention in Mexico (CENAPRED) (in Spanish).
Ministry of Public Works, San Salvador, 1997. Technical Standards for

63

Seismic Design, Regulation for Structural Security and Construction(in Spanish).
Official Report of the Republic of El Salvador, 1966. Regulations for
Seismic Design, No.15 (in Spanish).
Porrtill Gracia, Edwin, 1996. Background of civil engineering and evaluation of design standards in El Salvador, The Seismic Engineer in El
Salvador (Seminar), University of El Salvador (in Spanish).
Sawada, S., Katsuma, H., Yamasaki, Y. and Seo, K., 2001. Preliminary
report on damage caused by the El Salvador earthquake of January 13,
2001, Japan Earthquake Engineering NEWS, 177, 20-25 (inJapanese).
Seo, K., 2001. On earthquake damage in the January 13, 2001 in El
Salvador (Report presented on the web-site of
http://www.enveng.titech.ac.jp/seo/contents/research/elsalvador/report0215.html) (in Japanese).
Time, January 29, 2001. Death in the Valley of the Hammocks, 10.
Yoshimura, K. and Kikuchi, K., 1995. Experimental study on seismic
behavior of masonry walls confined by R/C frames, Proc. of PacificConference on Earthquake Engineering, 97-106.
Yoshimura, K., Kikuchi, K., Okamoto, T. and Sánchez, T. A., 1996. Effectof vertical and horizontal wall reinforcement on seismic behavior of
confined masonry walls, Proc. of 11th World Conference on
Earthquake Engineering (CD-ROM), Paper No. 191, 8pp.
Yoshimura, K., Kikuchi, K., Kuroki, M., Liu, L., Kajiwara, K. andUshijima, M., 1998. Effect of vertical axial loads and wall reinforcements on seismic behaviour of confined concrete masonry walls,
Proc. of 23rd Conference on Our World in Concrete & Structures,
221-228.
Yoshimura, K., Kikuchi, K., Kuroki, M. and Liu, L., 1999a. Experimental
study of the effect of height of lateral forces, applied vertical axial
loads and wall reinforcements on seismic behavior of confined concrete masonry walls, Journal of Structural and Construction
Engineering, Architectural Institute of Japan, No.524, 141-148 (inJapanese).
Yoshimura, K., Croston, T., Kagami, H. and Ishiyama, Y., 1999b. Damage
to building structures caused by the 1999 Quindio earthquake in
Colombia. Faculty of Engineering Research Report, Oita University,
No. 40, 17-24 (in English).
Yoshimura, K., Liu, L., Croston, T. and Ma, L., 1999c. Seismic strengthening for low-rise bamboo- and masonry-wall residential buildings in
Colombia. Faculty of Engineering Research Report, Oita University,
No. 40, 25-32 (in English).
Yoshimura, K., Kikuchi, K., Kuroki, M., Liu, L. and Ma, L., 2000a. Effectof wall reinforcements, applied lateral forces and vertical axial loads
on seismic behavior of confined concrete masonry walls, Proc. of
12th World Conference on Earthquake Engineering (CD-ROM),
Paper No. 0984, 8pp.
Yoshimura, K., Kikuchi, K., Kuroki, M., Nonaka, H., Croston, T., Koga,
S., Kim, K. T. and Ma, L., 2000b. Experimental study for higher seismic performance of masonry walls in developing countries, Proc. of
25th Conference on Our World in Concrete & Structures, 695-702.