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158
EARTHQUAKE BUILDING DAMAGE IN DEVELOPING
COUNTRIES: A REVIEW OF RECENT
RECONNAISSANCE REPORTS
A.W. Charleson1 and G.D. Fyfe2
ABSTRACT
This study reviews twenty-nine earthquake reconnaissance reports from developing countries
in
the
period from I 990--1998. After identifying trends
in
the different types and causes
of
damage
to
buildings reviewed
in
the reports, the paper suggests areas where earthquake damage mitigation should
be focussed; namely architectural and engineering conceptual design, engineering details and
construction. An analysis
of
all causes
of
seismic damage suggests conceptual design is the most
important area to focus on, and that codes or standards must include provisions to prevent poor building
configurations. Finally, the paper considers the nature
of
reconnaissance teams and their reports.
It
comments on teams' objectives and concludes by suggesting how teams might contribute towards
improving the mitigation
of
earthquake building damage
in
developing countries more directly.
INTRODUCTION
This research was undertaken under the auspices
of
the
Earthquake Hazard Centre, a non-governmental organisation
that disseminates earthquake engineering information to
developing countries [I]. Its aim
is
to reduce the gap
between developed and developing countries in terms
of
knowledge and practice
of
earthquake hazard reduction.
Significant reduction can be achieved by implementing
already proven existing seismic design and construction
techniques. By providing technologically appropriate
information and encouraging local research and other
initiatives, skills and standards are improved. Answers to the
question that
is
the basis
of
this paper, "what are the typical
types and causes
of
earthquake damage to buildings?" will
help ensure that the Centre disseminates relevant information
and directs its resources where needs are greatest.
For the purposes
of
the study, a developing country
is
defined
as
one that
is
essentially non-industrialised, where buildings
are predominantly non-engineered and building codes are not
implemented effectively. A group
of
such countries exhibits
wide variation in geographic location, climate, topography
and culture, including construction practices.
In
the period
1990-1998, one hundred and two earthquakes
of
approximate
Magnitude 6.5 or greater caused fatalities, injuries or
substantial damage in developing countries [2]. A
combination
of
literature searches and personal
correspondence
to
earthquake engineering organisations
in
the affected countries yielded a total
of
only twenty-nine
reconnaissance reports
in
English for nineteen earthquakes.
Even allowing for the fact that some earthquakes are located
in remote regions and some reconnaissance reports are
published only
in
local languages, it appears that potentially
valuable post-earthquake reporting
is
not being widely
disseminated.
Table 1 summarises the sources
of
the reconnaissance reports
and lists the numbers
of
individual buildings or groups
of
buildings whose damage reports are the basis
of
the study.
Most reports mix damage accounts
of
individual buildings,
usually those more prominent or important, with descriptions
of
damage to groups
of
buildings, often classified
geographically
as
in
the case
of
villages, or
by
building type.
Low cost housing and non-engineered construction
is
usually
discussed a group. Here are three typical examples
of
damage accounts
to
groups
of
buildings that have been
analyzed
in
the paper:
• "In these villages,
an
average
of
20%
of
the adobe
houses collapsed, 75% were heavily damaged and only
5% received light,
if
any, damage. The least damaged
houses are relatively new constructions with good adobe
quality
in
terms
of
maintenance and mixture. Three
typical failure modes can be detected from severely
damaged houses. The first one
is
the result
of
inadequate bond in the adobe wall corners, leading to
corner cracks and eventually to
an
outward failure
of
the
walls ..... "
• "In the epicentral area nearly all the buildings suffered
some damage and there was a large number
of
partial
and total collapses.
In
most cases the absence or
inadequacy
of
lateral ties caused out-of-plane collapse
of
stone masonry or adobe load bearing walls. Many other
stone masonry buildings suffered separation
of
the inner
and outer skins
of
the wall due
to
the absence
of
"through stones" and sufficient bonding."
1 School
of
Architecture, Victoria University
of
Wellington. (Fellow)
2 BBSc Hons. Graduate, School
of
Architecture, Victoria University
of
Wellington.
BULLETIN OF THE NEW ZEALAND SOCIETY FOR EARTHQUAKE ENGINEERING, Vol. 34, No.
2,
June
2001
•
"Damage
patterns observed in unreinforced masonry
(stone
or
brick) low-rise construction were
(I)
serious
damage
or
collapse
of
parapets; (2) vertical cracks in the
walls
due
to the presence
of
wide openings (windows
and doors); (3)
roof
and floor partial
or
full collapse
due
to inadequate wall support; and (4) separation
of
complete wedges from the
building
...
"
Engineered buildings tend to
be
singled out for more detailed
description and analysis.
Table
1:
Numbers and sources
of
reconnaissance
reports, and numbers
of
accounts
of
damaged buildings
Sources
of
Number Number
of
Number
of
reconnaissance of earthquakes either
reports reports individual
buildings
or groups
of
buildings
Costa Rica 3 I 8
Egypt 2 2
11
Greece I I 4
India 2 I
23
Indonesia -I I I
Flores Island
Iran 3 2 8
Mexico 3 2
14
Peoples 3 2 8
Republic
of
China
Peru I I 3
Philippines 3 2
23
Turkey 6 3
31
Venezuela I I 3
Total 29 19 139
Most
of
the buildings
or
groups
of
buildings discussed in
these reports comprise
one
of
the following construction
types:- unreinforced masonry without reinforced concrete in
lateral load resisting elements
(URM),
reinforced concrete
with no structurally significant masonry infills (RC),
combinations
of
reinforced concrete and unreinforced
masonry infill walls
(URM
and RC), and finally, adobe.
The
frequency with which each construction type is reported upon
is
listed in
Table
2.
The
relatively low occurrence
of
reports
on
adobe
damage
is
due
to reports describing damage to
groups
of
adobe buildings, often entire villages
or
even
regions.
Adobe
construction is
uncommon
in non-residential
construction, while
RC
is generally
uncommon
in residential
situations other than multi-storey apartments. Usually no
159
information on
the
age
of
damaged
buildings is provided in
reconnaissance reports.
Table
2:
Percentage
of
damage reports for different
construction materials
Construction material % total individual building
and building group damage
reports
URM
6
RC 36
URM and
RC
46
Adobe
12
TYPES OF DAMAGE
Many types
or
descriptions
of
damage
are reported, often in
quite general terms.
The
most significant are classified
in
Table
3.
While
some
descriptions are
not
very informative,
others point to recurrent themes
of
damage.
For
example,
unreinforced masonry infills
and
load
bearing
walls are
vulnerable to both in-plane (shear cracking), and out-of-plane
actions. This is hardly surprising given that these two
systems represent the most
common
form
of
lateral resistance
in developing countries.
There
are virtually
no
reports
of
damage
to beams, in stark contrast to frequent mention
of
column
damage. Unfortunately,
columns
are
not
only more
vulnerable to damage,
but
of
all structural elements, most
often lead to building collapse
when
they are damaged. This
observation reinforces the
importance
of
the strong column-
weak
beam
concept.
Table
3:
Main types
of
reported damage for
buildings that did not collapse
Types of % residential % non-residential
damage building damage building damage
reports reports
Wall out-of-
24
16
plane damage
Shear
cracks
19
25
(walls)
Column
16
23
damage
General
17
IO
damage
Other
24
26
Although the study
of
types
of
damage
does not identify any
unexpected trends, it prepares for a more constructive study
of
causes
of
damage, which, when addressed, will lead to
more resilient building construction.
CAUSES OF DAMAGE
The
reconnaissance reports note a total
of
approximately
thirty different causes
of
building
damage. In
some
buildings
the damage
is
attributed to more
than
one
cause. An analysis
160
of
causes indicates that they can be divided into three groups;
conceptual, detailing and construction, as shown in Table 4.
Each cause
of
damage is listed
if
its occurrence is more than
five percent
of
the total. As mentioned above, due to the fact
that residential building damage is usually described in the
context
of
groups
of
buildings, and non-residential damage to
individual buildings, the percentage values are intended only
to indicate trends.
Although some reports note poor ground as a cause
of
damage, due to a general lack
of
detailed information the
study excludes causes
of
damage resulting from foundations
and soil conditions.
Table
4:
Categories and causes of damage
Categories of causes
of
Causes
of
damage %
of
causes in residential %
of
causes in non-residential
damage
Conceptual Soft-storey
Short column effect
Irregularity
of
plan
stiffness
Other causes
Detailing
Poor
detailing
(unspecified)
Lack
of
ties
Inadequate ductility
Other
Construction
Poor
construction
( unspecified)
Poor
material quality
Other
Conceptual
Causes
of
damage resulting from conceptual architectural,
engineering, and traditional building decisions are included in
this category.
For
both residential and non-residential
construction, conceptual deficiencies account for about
half
of
all causes
of
damage.
Poor
building configuration
(structural layout) caused by soft-storeys, short columns, and
plan irregularities is a major contributor. Sixteen separate
causes
of
damage are included in the 'other causes'
of
damage resulting from conceptual deficiencies. They include
vertical discontinuity
of
infills, slender walls, pounding, one-
directional structural systems, lack
of
redundancy, high roof
mass, large diaphragm openings, and inadequate
roof
bracing.
Poor architectural and engineering conceptual design is
bel!eved to be an even more significant cause
of
damage than
shown above. A poor building configuration concept
mcreases structural demands on both detailing and
construction quality, and, depending on whether the intensity
of
shaking causes structural damage, these inadequacies may
be exposed. However,
if
a design concept is sound, neither
detailing nor construction quality may be tested at all.
The
importance
of
sound design concepts in achieving adequate
seismic performance is therefore underestimat;d in this
analysis.
9
5
7
23
9
11
5
4
10
11
6
buildings buildings
13
9
44 6
52
24
18
29
4
30
5
3
8
27
4
18
6
In
several instances, non-compliance with building codes
is
noted
as
a cause
of
damage in reconnaissance reports.
Typical examples include column ties too widely spaced, or
ties with ninety degree rather than one hundred and thirty five
degree bends. Codes generally provide specific guidelines for
detailing and such details are easily checked after a damaging
earthquake. Clearly, more emphasis is required on reviewing
code compliance with respect to building configuration,
which this study shows to be the predominant cause
of
seismic damage. Where a strong earthquake engineering
culture and community exists, and designers are aware
of
the
importance
of
good configuration, emphasis in codes on
detailed rather than conceptual design may not be such a
problem. However, building codes in developing countries
perhaps need to
be
more explicit in preventing poorly
configured buildings.
Unfortunately, this aspect
of
code development
is
difficult.
More than detailed structural engineering considerations are
at stake. Architectural, building use and other cultural factors
can predominate. For example, modern architectural
planning with an adherence to open ground floors for shops
or parking often leads to numerous soft storeys. In addition,
professionals in fields other than structural engineering are
often not interested in seismic issues. Not only
is
a multi-
disciplinary approach required where a uniform level
of
professional commitment is lacking, but the technical basis
for inclusion
of
code configurational constraints may
be
fuzzy. Engineering judgement honed by exposure
to
earthquake damage
is
indispensable for code committee
decision making given the levels
of
structural complexity and
uncertainty. For
any
community to have a satisfactory level
of seismic resilience, attention must be paid
to
conceptual
design issues
in
codes.
Detailing
Depending on the quality
of
a conceptual design, poor
detailing may or may not be another cause
of
damage.
As
discussed above, if the design concept
is
poor, resulting
in
a
soft storey for example, then any poor detailing
will
be
exposed. There are a number
of
reasons for poor detailing;
poor design
of
details, poor
superv1s1on
and
poor
construction.
If
design details are poor or even non-existent,
supervision
and
construction can not remedy the situation.
At
best,
an
enlightened and concerned supervisor or
contractor might take remedial action. Structurally adequate
details must always be provided
in
construction
documentation. The next method
of
improving detailing
is
to
provide site supervision.
If
it
is
reliable and of sufficient
quality it can avoid, or
at
least reduce instances of poor
construction.
If
supervision
is
ineffective, and unless there
is
specific evidence
to
the contrary, one must assume the
quality
of
construction
is
suspect.
A review
of
causes
of
damage that can be attributed
to
detailing problems highlights poor detailing of steel
reinforcement
in
reinforced concrete construction,
particularly
in
non-residential buildings. Many
reconnaissance teams comment on insufficient amounts
of
reinforcing steel. While poor performance
of
reinforced
concrete construction
is
of
great concern there
is
real
possibility for improvement. Almost
all
non-residential
buildings
and
many
residential buildings
in
this study rely
upon reinforced concrete. Although it
is
considered
an
acceptable, if not indispensable construction material,
in
many situations it proves inadequate when subject
to
significant seismic actions. Increased industry education that
begins by emphasising the importance
of
building
configuration
to
designers, and even includes basic lessons
for workers
on
building sites, will improve building standards
and reduce vulnerability.
Poor detailing
in
residential construction
is
often due
to
a
lack of "through stones" that tie outer wythes
of
adobe walls
together, and
an
overall general lack
of
interconnection
of
building elements.
In
most cases such buildings are built
by
owners with minimal financial resources. Again, education
should be the focus
of
any seismic damage mitigation
program.
Within reconnaissance reports there are few,
if
any, causes
of
damage reported that are believed
to
be new or not
understood. Causes
of
seismic damage have either been seen
before, or at least are expected. This confirms the view that a
basic problem of ensuring adequate seismic performance
in
developing countries may not only be due to a lack of
knowledge, but rather a lack
of
application
of
techniques that
have been proven,
at
least in structural laboratories
in
other
parts
of
the world.
Construction
No
strong trends emerge from the list
of
reported
construction defects. Construction inadequacy
is
far more
likely
to
be a cause
of
damage
in
residential buildings than
in
161
other building types. This
is
presumably due
to
the fact that
many houses are owner built.
In
these cases, poor
construction and material quality are reported frequently,
whereas
in
non-residential construction these issues represent
a surprisingly low contribution
to
overall causes of damage.
Reasons for poor construction are not usually cited explicitly.
Often they are not known with' certainty, but one can assume
some combination
of
the following: lack
of
resources,
ignorance and dishonesty.
Of
these three reasons, the first
is
the most serious, given its widespread nature, and it
challenges those associated with the building industry
worldwide
to
keep developing cheaper
and
more suitable
construction materials, systems and details
in
order to
improve seismic safety. Ignorance can be addressed by
improved educational efforts, but dishonesty can be
ameliorated only by high quality supervision.
RECONNAISSANCE REPORTS
Two thirds
of
the reports studied are authored by engineers
and researchers from developed countries.
In
most cases
these visitors seek information and lessons that are relevant
and transferable
to
their own situations. Their focus is upon
building stock and construction systems similar to their own,
increasing the relevance
of
their reconnaissance
to
their peers
and sponsors back home. Meanwhile host countries may
benefit eventually from the considerable expertise
of
reconnaissance teams via the "trickle down" effect.
The fact that a reconnaissance team's research agenda
is
orientated towards the needs
of
its own society rather than
those of the local people,
is
not necessarily bad. However,
perhaps this focus should be more openly acknowledged in
order
to
identify more tangible ways
of
providing local
assistance. A voluntary levy,
of
say
ten
percent
of
visiting
reconnaissance teams' costs would be very effective
in
promoting on-going research
at
a local level. Providing
resources for longer term seismic damage evaluation
is
likely
to
be particularly valuable, especially considering the lack
of
detailed study undertaken
by
reconnaissance teams. Their
limited duration
of
visits does not permit detailed research, or
even a more rigorous approach where attention
is
not
inevitably drawn to prominent buildings that have been
damaged. Perhaps teams could work specifically with
counterparts and report locally
as
well
as
to their colleagues
back home.
Reports place far greater emphasis on damage to engineered,
rather than
to
non-engineered buildings. Adobe building
performance for example, does not receive the attention it
deserves, given both its unlimited use and its high
vulnerability.
Of
course, visitors from developed countries
may not be conversant with this type
of
construction.
What
is
less certain
is
the extent
to
which reconnaissance
teams understand why some buildings perform better than
others. The focus
of
most reports
is
on
damage, even though
it
is
well recognised there
is
much
to
learn from less damaged
buildings
in
the same vicinity. There are many accounts
of
undamaged buildings surrounded by those that have
collapsed. Studies
of
surviving buildings might identify
characteristics that contribute
to
good performance and
thereby provide additional evidence for code modifications.
For example, correlation of damage with degrees
of
code
162
compliance might be possible. Due to the limited duration
of
visits by reconnaissance teams, this work is probably best left
to local researchers, where possible, encouraged and aided by
personnel
of
overseas teams.
CONCLUSIONS
The main causes
of
damage
to
buildings in developing
countries can be classified under the headings
of
conceptual,
detailing and construction.
Flawed design concepts are responsible for over half the
damage to both residential and non-residential construction.
This area
of
conceptual design is where education and code
development programs should be aimed.
Damage
to
adobe and other buildings with vernacular
construction methods is under-represented in reconnaissance
reports.
In
recognition
of
lessons gained by reconnaissance teams
from developed countries that are valuable for their own
countries, and the fact that much valuable post-earthquake
research can be undertaken, visiting teams should consider
contributing resources
to
local researchers. Such a gesture
would significantly improve the contribution reconnaissance
teams and reports make to developing countries.
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INTERNET REPORTS:
The July 9, 1997, Cariaco, Eastern Venezuela Earthquake,
EERI Special Earthquake Report -October 1997,
http://www.eeri.org/Reconn/Cariaco/Cariaco.html
The N azca, Peru, Earthquake
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http://www.eeri.org/Reconn/Nazca/Nazca I .html
The Aqaba Earthquake
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November 22, 1995, EERI Special
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http://www.eeri.org/Reconn/ Aqaba/ Aqaba I .html
163
The January 21, 1997, Jiashi, China Earthquake, EERI
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http://www.eeri.org/Reconn/Jiashi/Jiashi.html
The September
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1995 Ometepec, Mexico Earthquake,
EERI Special Earthquake Report -December 1995,
http://www.eeri.org/Reconn/Ometepec/Ometepec.html
The Dinar, Turkey Earthquake
of
October I, 1995, EERI
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Reconnaissance team returns from Lijiang Earthquake
Investigation, EERI Special Earthquake Report -May
1996, http://www.eeri.org/Reconn/Lijiang/Lijiang.html
The October 9,1995 Magnitude 7.6 Manzanilla, Mexico
Earthquake, EERI Special Earthquake Report -
December 1995,
http://www.eeri.org/Reconn/Manzanillo/Manzanillo.html
The Ardekul, Iran, Earthquake
of
May
10,
1997, EERI
Special Earthquake Report -September 1997,
http://www.eeri.org/Reconn/ Ardekul/ Ardekul .html
Some observations
on
engineering aspects
of
the Jabalpur
Earthquake
of
22
May 1997, EERI Special Earthquake
Report- August 1997,
http://www.eeri.org/Reconn/Jabalpur/Jabalpur.html
