Damage of RC Building Structures Due to 2011 East Japan Earthquake

Abstract

This paper presented the investigation of reinforced concrete building structures by 2011 East Japan Earthquake. Generally, reinforced concrete structures in Miyagi region performed very well during the earthquake and effect of seismic retrofit was found in mitigation of damage, although severe damage to some seismically retrofitted buildings was noticed. A good correlation was observed between calculated seismic capacity Is-index and observed damage. Moreover, buildings designed according to the current seismic design code had minor damage in its structural members. However, major damage to non structural elements was commonly observed. Some typical damage observed by author's field survey in Miyagi pref. which is conducted mainly as an activity of the AIJ committee is described. Damage to structural members was not found in most of RC buildings which suffered tsunami, although damage to non structural elements was generally severe. However, severe structural damage induced by devastating tsunami was observed in some buildings.

Full text

Damage of RC Building Structures due to 2011 East Japan Earthquake
Masaki MAEDA1, Hamood AL-WASHALI2 , Kazuki SUZUKI3
and Kanako TAKAHASHI4 ,
1 Professor, Department of Architecture and Building Science, Tohoku University,
Aobayama 6-6-11-1207, Sendai 980-8579, Japan; PH & FAX 81-22-795-7872;
email: maeda@archi.tohoku.ac.jp
2 Graduate student, Department of Architecture and Building Science, Tohoku
University, Aobayama 6-6-11-1207, Sendai 980-8579, Japan; PH & FAX
81-22-795-7872; email: hamood@sally.str.archi.tohoku.ac.jp
3 Graduate student, Department of Architecture and Building Science, Tohoku
University, Aobayama 6-6-11-1207, Sendai 980-8579, Japan; PH & FAX
81-22-795-7872; email: suzuki@ sally.str.archi.tohoku.ac.jp
4 Graduate student, Department of Architecture and Building Science, Tohoku
University, Aobayama 6-6-11-1207, Sendai 980-8579, Japan; PH & FAX
81-22-795-7872; email: takahashi@sally.str.archi.tohoku.ac.jp
ABSTRACT
This paper presented the investigation of reinforced concrete building
structures by 2011 East Japan Earthquake. Generally, reinforced concrete structures
in Miyagi region performed very well during the earthquake and effect of seismic
retrofit was found in mitigation of damage, although severe damage to some
seismically retrofitted buildings was noticed. A good correlation was observed
between calculated seismic capacity Is-index and observed damage. Moreover,
buildings designed according to the current seismic design code had minor damage
in its structural members. However, major damage to non structural elements was
commonly observed. Some typical damage observed by author’s field survey in
Miyagi pref. which is conducted mainly as an activity of the AIJ committee is
described. Damage to structural members was not found in most of RC buildings
which suffered tsunami, although damage to non structural elements was generally
severe. However, severe structural damage induced by devastating tsunami was
observed in some buildings.
1 INTRODUCTION
This paper is to describe reconnaissance activities of AIJ, Architectural
Institute of Japan, after the 2011 East Japan Earthquake. Typical damages to
reinforced concrete school buildings are outlined, both by the ground motion and
tsunami waves, based on the field observation data of about two hundred school
buildings in Miyagi region.
The school building committee and the reinforced concrete steering
committee of AIJ jointly organized a special task committee and working groups on
the post-earthquake investigation and damage evaluation of school buildings and
1023Structures Congress 2012 © ASCE 2012

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1024Structures Congress 2012 © ASCE 2012

Figure 3 shows acceleration time history at MYG004, MYG013 and 4B9
which recorded large ground acceleration. According to JMA, the earthquake may
have ruptured the fault zone from Iwate to Ibaraki Pref. with a length of 500 km and
a width of 200 km, therefore both acceleration time histories have plural peaks, and
the duration of ground shaking is very long, about 180 sec. Due to long duration, soil
liquefaction occurred at several locations from Tohoku district to Kanto district.
Table 1 shows the records of ground motion for intensities over 5.6 using
JMA Seismic Intensity Scale observation stations in Miyagi pref. Several records
exceed 1000 gal in their peak ground accelerations(PGA) and the maximum recorded
acceleration was 2699 gal obtained at MYG004, N-S direction.
Figure 4 shows 5%-damped acceleration response spectrum and comparison
with past major earthquakes.MYG004 has extremely high acceleration response,
11852gal, in the very short period(T＜0.5sec). MYG013 and 4B9 has a response
spectrum peak around 1sec, also the peak value of their acceleration response is
almost as same as JR Takatori at 1995 Kobe and COUNTRY HOSPITAL at 1994
Northridge, which had severe damage.
Figure 3. Observed acceleration time history
-3000
-2000
-1000
0
1000
2000
3000
Acc（cm/s
2
）
MYG004-NS
-3000
-2000
-1000
0
1000
2000
3000
0 20 40 60 80 100 120 140 160 180
Acc（cm/s
2
）
time
（
s
）
MYG004-EW
-2000
-1000
0
1000
2000
Acc（cm/s
2
）
MYG013-NS
-2000
-1000
0
1000
2000
Acc（cm/s
2
）
MYG013-EW
-1000
-500
0
500
1000
Acc（cm/s
2
）
4B9-NS
-1000
-500
0
500
1000
0 20 40 60 80 100 120 140 160 180
Acc（cm/s
2
）
time（s）
4B9-EW
1025Structures Congress 2012 © ASCE 2012

Table 1. Records of ground motion at each observation stations in Miyagi pref.
Figure 4. 5%-damped acceleration response spectrum
and comparison with past major earthquakes
3 OUTLINE OF DAMAGE TO RC SCHOOL BUILDINGS IN MIYAGI
3.1 Damage Statistics
The Japanese seismic design codes for buildings were revised in 1971 and
1981. Specifications such as maximum spacing of hoops of reinforced concrete
columns were revised to increase structural ductility in 1971, whereas the
verification on the ultimate lateral load carrying capacity of designed structure by
limit state or pushover analysis considering deformation capacity of members was
required in 1981.In Japan, screening by seismic evaluation and retrofit of vulnerable
buildings has been widely applied to existing buildings, especially after the 1995
Kobe Earthquake. As a result, more than 90 percent of school buildings in Miyagi
prefecture are reported to be provided with required seismic capacity.
Figure 5 shows seismic capacity statistics classified according to the
construction year and seismic capacity. There are 686 elementary and junior high
schools which have 2371 school buildings in Miyagi Prefecture (2010, MEXT).
Generally one gymnasium, usually steel structure, is located on the average in each
Name of statio n directio n PGA（gal）PGV（kin e）JM
A
Scale
※
Name of station direction PGA（gal ）PGV（kine）JMA Scale
※
NS 2699.1 117.6 NS 359.5 54.6
EW 1268.6 51.2 EW 336.9 70.1
NS 444.1 50.6 NS 405.8 87.2
EW 571.5 89.1 EW 438.7 80.7
NS 568.0 34.9 NS 389.6 55.6
EW 650.9 34.1 EW 433.9 52.7
NS 458.2 51.5 NS 551.8 49.5
EW 377.0 53.1 EW 710.7 35.9
NS 921.0 18.6 NS 379.1 28.0
EW 688.2 35.5 EW 664.4 54.6
NS 758.5 31.6 NS 549.6 78.0
EW 1969.1 61.8 EW 456.4 86.9
NS 1517.1 84.3 NS 409.9 53.9
EW 982.3 43 .0 EW 317.9 54.2
NS 410.7 69.9 NS 332.8 49.2
EW 353.2 52 .6 EW 329.8 61.1
NS 317.4 45.6
EW 349.3 49 .2
MYG004 6.67
MYG006 6.16
MYG007 5.81
MYG010 5.93
MYG011 5.63
MYG012 6.02
MYG013 6.38
MYG015 5.99
MYG017 5.83
8A3(Matsushima) 5.74
8A4(Wakuya) 6.02
8A5(Tome) 5.75
8A6(Kurihara) 5.70
4B8(Kesennuma) 5.80
4B9(Osaki) 6.21
E06(Sendai) 5.69
THU 5.60
※JMA Scale＝Japan Meteorology Agency Secimic Intencity Scale
0
500
1000
1500
2000
2500
3000
0123
5% dampe d Response Sp ectrum
Accellaration(cm/sec
2
)
Period T(sec)
2011 4B9
1995Kobe
1994 Northridge
2011 Chiristcurch
2011 East Japan MYG004
2011 East Japan MYG013
2011
East Japan THU 1978 Miyagi-Oki
1026Structures Congress 2012 © ASCE 2012

Slight or Non
Minor
Moderate
Severe
Collapse
school. So, there are about 1600 RC school buildings in Miyagi Pref. Figure 5(b)
shows RC school buildings investigated by the AIJ committee after this earthquake.
This figure excludes small building such as connecting passage ways and staircases.
The percentage of school buildings designed by current seismic design code (post-
1981) is 50% of the total number. However, the investigated buildings designed by
current seismic design code are only 20% of the whole investigated number. On the
other hand, rate of investigated vulnerable buildings is as twice as that of all
vulnerable buildings.
Figure 6 shows damage statistics due to ground motion. This figure excludes
buildings suffered from tsunami and damage of the foundation. Most of vulnerable
buildings (post-1981, Is < 0.7) suffered from moderate to severe damage.
Figure 7(a) shows the damage ratio of 151 RC school buildings in Nada and
Higashi-nada Ward, Kobe City suffered from the 1995 Kobe Earthquake. Most of the
buildings, which suffered from serious damage, were designed and constructed
before 1981, and especially those before 1971 had extensive damage. On the other
hand, most new buildings designed according to the current seismic codes enforced
in 1981 showed fairly good performance and prevented severe structural damage. As
mentioned above, seismic capacity evaluation and strengthening have been applied to
existing buildings especially after the 1995 Kobe Earthquake. All RC school
buildings in Sendai City were satisfied with the criteria. Figure 7(b) shows the
damage ratio of 386 RC school buildings in Sendai City suffered from the 2011 East
Japan Earthquake. It is obvious that there is no buildings suffered from over severe
damage. In addition , there are few buildings suffered from over moderate damage
irrespective of age.
0 1020304050
1982～
～1981(r et rof itte d or Is≧0.7)
～1981(I s＜0.7)
Frequency
(a) All buildings in Miyagi pref. (b) Investigated RC buildings
Figure5. Seismic capacity statistics of school buildings
Figure6. Damage level of investigated school buildings in Miyagi Pref.
1027Structures Congress 2012 © ASCE 2012

(a) 1995 Kobe EQ (b) 2011 East Japan EQ
Figure 7. Damage ratio of RC school building
94
42
19
33
23
3
9
11
25
2
4
19
4
1
3
5
5
0% 20% 40% 60% 80% 100%
Total
Post-1981
1971-1981
Pre - 1971
359
176
153
30
20
3
16
1
7
3
3
1
0% 20% 40% 60% 80% 100%
3.2 Relationship between Seismic Capacity and Damage
Figure 8 shows the relationship between the seismic capacity index
(Is-Index) and construction age of 32 RC school buildings, where Is-Indices of each
building are evaluated by the “Japanese Standard for Seismic Capacity Evaluation of
Existing Reinforced Concrete Building”(JBDPA 2001b). Is-Index can be calculated
by Eq.(1) at each story and each direction.
TSEIs D××= 0 (1)
E0 is a basic structural index calculated by Eq.(2).
FCE ××=
φ
0 (2)
C-Index is strength index that denotes the lateral strength of the buildings in terms of
shear force coefficient. F-Index denotes the ductility index of the building ranging
from 0.8 (extremely brittle) to 3.2 (most ductile), depending on the sectional
properties such as bar arrangement, member proportion, shear-to-flexural-strength
ratio etc.
φ
is story index that is a modification factor to allow for the mode shape of
the response along the building height. SD and T are reduction factors to modify E0 in
consideration of structural irregularity and deterioration after construction,
respectively.
The Seismic Evaluation Standard recommends as the demand criterion that
Is-Index higher than 0.6 should be provided to prevent major structural damage or
collapse. This criterion is based on the correlation study from the past earthquake
damage and the calculated indices for the damaged buildings(Okada 1998). Past
experiences of the big earthquakes reported that buildings with Is-Indices higher than
0.6 escaped severe damage or collapse. Is-Index of school buildings is demanded
higher value (0.7) than normal buildings. It is because that school buildings require
not only the security of safety but also the security of function to use buildings
without repairing structural damage after big earthquake. As can be found in Figure 8,
Is-Indices for most of the buildings were more than 0.7 and prevented severe
structural damage even if they were old buildings. Figure 9 shows the relationship
between Is-Index and damage level indices R-Index proposed in “Standard for
Post-earthquake Damage Level Classification of Reinforced Concrete Building”
(JBDPA 2001a). A good correlation was observed between calculated Is-index and
observed damage. Most buildings with Is-values lower than 0.6 were vulnerable to
moderate and severe damage. Most of the buildings with Is-values higher than 0.7
1028Structures Congress 2012 © ASCE 2012

Figure 9. Is-Indices and damage
indices
Figure 8. Construction age and
Is-Indices of RC school buildings
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1960 1965 1970 1975 1980 1985
Is-Index
Construction Age
Slight or Non
Minor
Moderate
Severe
0
10
20
30
40
50
60
70
80
90
100
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Residual seismic capacity ratio, R[%]
Is-Index
Slight
Moderate
Minor
Severe
avoided severe damage and had minor and slight damage (R > 80). Is-Index of 0.7 is
generally regarded as an effective demand criterion for screening seismically
vulnerable buildings.
4 TYPICAL OBSERVED DAMAGE
In this chapter, some typical damage observed by author’s field survey in
Miyagi pref. which is conducted mainly as an activity of the AIJ committee is
described. The damage is classified into 2 main classes; Damage by tsunami and
damage by ground motion.
4.1 Damage by Ground motion
4.1.1 Severely damaged buildings
Comparatively, the percentage of severely damaged building of the observed
buildings is not greater than previous damaging earthquakes. Some of the severely
damaged buildings are mentioned below.
Figure 10 hows 3 storied RC school building in Shitigahama town built in
1966. Seismic capacity Is-index of the building was evaluated much lower than the
criteria of 0.7, however, it was not retrofitted before the earthquake. Many of its
columns and shear walls failed in shear as shown in figure 11and figure 12.
Figure 13 hows 9-story steel reinforced concrete(SRC) building of Civil
Engineering and Architecture building in Tohoku University constructed in 1969,
Figure 12. Shear failure
in shear wall
Figure 11. Shear
failure in column
Figure 10. North view
o
f
sc
h
oo
l
bu
il
d
in
g
1029Structures Congress 2012 © ASCE 2012

wh
i
sh
e
an
d
Ac
c
lon
jac
k
ret
r
Th
e
tra
n
Da
m
Fi
g
wo
u
An
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wh
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as
2
F
b
i
ch suffere
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ar cracks
a
d
few colu
m
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eleration r
e
In 20
0
n
gitudinal
d
k
eting of
a
r
ofitte
d
, it
w
e
damage
w
n
sverse dir
e
m
age to c
o
g
ure 17). O
n
u
ld be po
o
o
ther reaso
n
i
ch is fund
a
2
011 East J
a
F
igure 13.
N
b
uildin
g
in
T
(a) 1978
M
Fi
g
d
from mi
n
a
nd flexure
m
ns in the
e
cords wer
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1, it was s
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irection,
r
a
djacent be
a
w
as severel
y
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as concen
t
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ction were
o
nnection b
n
e of the
r
o
r connecti
o
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may be s
t
a
mental vib
r
a
pan THU
N
N
orth vie
w
T
ohoku U
n
M
i
y
a
g
i Oki
g
ure 15. C
r
n
or damage
cracks wer
e
3
rd
and 4
t
e
obtained
b
e
ismically
r
r
eplacemen
t
a
ms with s
t
y
damage
d
b
t
rated in t
h
crushed w
i
etween ins
t
r
easons for
o
n between
rong groun
d
r
ation peri
o
N
S.
w
of
n
iv.
Earthqua
k
r
ack
p
atter
n
due to the
e observed
t
h
floor as
b
oth in 1
st
a
n
r
etrofitte
d
b
t
of shear
teel plates
(
b
y the 2011
h
e 3
rd
story.
i
th fracture
t
alled shea
r
such a se
v
n
new insta
l
d motion a
t
o
d of this b
u
Figure 14.
k
e
n of buildi
n
1978 Miy
a
in main s
h
shown in
f
n
d 9
th
floor
.
b
y installin
g
walls in
(
see Figure
earthquak
e
Boundary
and buckli
n
r
wall and
v
ere damag
e
l
led eleme
n
t
the site es
p
u
ilding as
m
T
y
pical fl
o
(b) 2011
E
ng
in Toho
k
a
gi Oki ear
t
h
ear walls,
a
f
igure 15(
a
.
g
framed ste
transverse
14). Even
e
as shown
i
columns o
n
g of steel
(
frame was
e
to a retr
o
n
ts and exi
s
p
ecially for
m
entioned a
b
o
or plan
E
ast Japan
k
u Univer
s
r
thquake. S
m
a
djacent b
e
a
)(Shiga 1
9
e
el braces t
o
direction
though it
in figure 1
5
o
f shear wa
l
(
see Figure
s
observed
o
fitte
d
b
uil
d
sting struc
t
period of 1
b
ove in fig
u
Earthqua
k
s
it
y
m
all
ams
80).
o
the
and
was
5
(b).
l
l in
16).
(see
d
ing
t
ure.
sec.
u
re 4
k
e
1030Structures Congress 2012 © ASCE 2012

4.1
ac
c
b
ui
ge
n
cit
y
an
d
sei
s
wa
s
Ea
s
thi
s
the
Sh
e
axi
a
Ho
w
of
f
me
n
4.1
sei
s
F
.2 Seismic
a
Most
c
ording to
lding suff
e
n
eral, seism
i
Figur
e
y
construct
e
d
east side.
s
mic evalu
a
s
evaluated
s
t side buil
d
s
earthquak
East side
b
e
ar failure
o
a
l loads co
u
w
ever, the
s
f
unctionali
t
n
tioned ab
o
.3 Dama
g
e
All t
h
s
mic code
o
F
igure 16.
B
shear
w
Figure 18.
buildi
n
a
ll
y
retrofi
t
of the ex
i
the old se
e
re
d
severe
i
cally retro
f
e
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e
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ic code
w
ith the cu
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1031Structures Congress 2012 © ASCE 2012

Severely damaged buildings which may be a threat to life safety were not observed
in this survey. However, Moderate damage to some buildings designed according to
the early versions (early 1980s) of the current seismic design code was observed.
This damage caused the building to be non-functional after the earthquake. Figure 20
shows a typical example of a four storied elementary school building constructed in
1985. This building had a shear failure in one of its walls as shown in figure 21.
Beams with shear failure were also noticed as shown in figure 22.
4.1.4 Damage to non structural elements:
Major damage to non structural elements was observed in buildings
designed according to current seismic design code, although the damage in its
structural members was commonly minor. This damage was likely to be observed in
high-rise housing buildings.
Figure 23 shows an eleven storied SRC apartment building in Sendai city. It
had a minor damage in its structural members. However, many of its non structural
partition RC walls around doors and windows were severely damage as shown in
Figure 23. Most of the residents of this building were concerned about safety and had
to leave. Therefore, this building became unusable due to such damage. In figure 28,
large parts of ceiling fell in a gym of a junior high school in Kurihara city fell down.
4.1.5 Damage to foundations;
Settlement and tilting of buildings as a result of liquefaction had occurred in
some regions of Miyagi prefecture. Figure 25 shows a junior high school building in
Osaki city. The right side of the building was constructed in 1978. The left side was
Fi
g
ure20. North view. Figure 21. Large shear
cracks in wing wall.
Figure 22.Shear
failure in beam
Figure23. Damage to non structural
wall
Figure 24. Large parts of the false
ceiling fell down
1032Structures Congress 2012 © ASCE 2012

added in 1991. This school rests on a soft ground with pile foundation of 20m in
depth. Evidence of liquefaction was seen around the school as shown in figure 26.
The right side part had a settlement of about 60 cm, the south part was inclined by
angle of 1/25 rad. The newly added part had a settlement of about 10 cm and slightly
inclined. The response spectrum of this area is mentioned above in figure 4 as 2011
East Japan 4B9 NS.
4.2 Damage by Tsunami;
The Northeast coastal areas have been heavily damaged by Tsunami.
However, as for reinforced concrete structures, most of the damage due to tsunami
were in its non structural elements such as false ceilings, window and doors.
Figure 27 shows a high school building in Kesennuma city. The flooding reached 3rd
floor. Windows, doors ceiling were washed away and classrooms were full of debris.
Figure 28 shows a floor slab that was lifted up and damaged at connections with
beams in Ishonamaki city.
Figure 26. Liquefaction evidence located
3 stair ste
p
s from the
g
round surface.
Figure 25. Difference in level of
Expansion joint
Figure 27. Flood reached 3rd floor Figure 28. Slab uplifted and
dismantled from beam
Figure 29. Building overturned by
tsunami
Figure 30. piles were pulled out
and fractured
1033Structures Congress 2012 © ASCE 2012

In addition, Onagawa town suffered a devastating tsunami, some RC
building were overturned from its base as shown in figure 29. Piles were pulled out
and buildings overturned as shown in figure 30. Design structures to resist such force
were not considered since it the first time to experience such forces and behavior.
Such phenomena needs further study.
5. CONCLUSION
This paper presented the investigation of reinforced concrete building
structures. Overall, reinforced concrete structures in Miyagi region performed very
well during the earthquake, although severe damage to some seismically retrofitted
buildings was found. A good correlation was observed between calculated seismic
capacity Is-index and observed damage. Most of the buildings with Is-values lower
than 0.6 were vulnerable to moderate and severe damage. Most of the buildings with
Is-values higher than 0.7 escaped severe damage. Moreover, buildings designed
according to current seismic design code had minor damage in structural members.
However, major damage to non structural elements was seen even in new buildings.
Damage to structural members was not found in most of RC buildings
which suffered tsunami, although damage to non structural elements such as
windows, partitions, ceiling boards and equipments was generally severe. However,
severe structural damage induced by devastating tsunami was observed. Structural
design against tsunami force, which is not taken into account in the current design
code, needs to be studied.
REFERENCES
Architectural Institute of Japan (AIJ). (2011), Preliminary Reconnaissance Report of
the 2011 Tohoku-Chiho Taiheiyo-Oki Earthquake (in Japanese), Maruzen, Japan
BRI Strong Motion Observation, http://smo.kenken.go.jp/ja/smreport/201103111446/
Japan Building Disaster Prevention Association(JBDPA). (2001a). Standard for
Post-earthquake Damage Level Classification of Reinforced Concrete Building.
Japan Building Disaster Prevention Association(JBDPA). (2001b). Standard for
Seismic Evaluation of Existing Reinforced Concrete Buildings.
JMA,http://www.seisvol.kishou.go.jp/eq/kyoshin/jishin/110311_tohokuchiho-taiheiy
ouoki/index.html
NIED K-NET, http://www.k-net.bosai.go.jp/k-net/
OKADA, T., KABEYASAWA T.，NAKANO Y., MAEDA M.，and NAKAMURA
T.(2000). “Improvement of Seismic Performance of Reinforced Concrete
School Buildings in Japan -Part 1 Damage Survey and Performance Evaluation
after 1995 Hyogo-ken Nambu Earthquake-”，Proceedings of 12th World
Conference on Earthquake Engineering，paper No.2421（CD-ROM）.
Shiga T.,(1980).”performance of the building of faculty of engineering, Tohoku
University, During the 1978 Miyagi-Ken-Oki Earthquake”, 7th WCEE Instabul.
1034Structures Congress 2012 © ASCE 2012