Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanSEISMIC PERFORMANCE OF REINFORCED
CONCRETE SCHOOL BUILDINGIN FUKUSHIMA UNDERTHE GREAT EAST JAPAN EARTHQUAKE
Kazuya KAMATAKI1, Akira TASAI2, and Koichi KUSUNOKI3
1

Graduate Student Department of Architecture Engineering,
Yokohama National University, Kanagawa, Japan, kamataki-kazuya-jy@ynu.ac.jp
2
Professor Department of Architecture Engineering,
Yokohama National University, Kanagawa, Japan,tasai@ynu.ac.jp
3
Associate Professor Department of Architecture Engineering,
Yokohama National University, Kanagawa, Japan, kusunoki@ynu.ac.jp
ABSTRACT: On March 11 of 2011, a great earthquake occurred in Tohoku region, which caused
severe damages and collapses of buildings. That is why, it is necessary the study of the seismic
performance of buildings to understand the causes of their damages, especially, if these buildings areimportant facilities which ensuring the life safety. In this sense, this study attempts to evaluate theseismic performance by the standard evaluation of seismic capacity and the static elastoplastic analysis
method on the 3D model of the school building.
Key words: Great East Japan Earthquake, nonlinear static analysis, school building

INTRODUCTION
This study analysis the seismic performance of RC School Building under the Great East Japan
Earthquake which performs a nonlinear static analysis in order to study the earthquake resistantcapacity.
OUTLINE OF THE BUILDING AND DAMAGES

Outline of the buildingThis school is located in Fukushima prefecture, which is conformed by 4 RC buildings, the layout planof buildings is shown in Fig.1. Buildings for classrooms (Building “A” and Building “B”) are locatedon the north and south. Two connecting corridor buildings (Building “C” and Building “D”) areconnected to A Building and B Building with gap.
Building “A” is 4-story Reinforced Concrete (referred to as RC, hereafter) building with total floor
space of 2,962m2. Building “B” is 3-story RC building with total floor space of 2,059m2. Building “C”

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is 2-story RC building for connecting corridor and class rooms with total floor space of 459m2.
Building “D” is also 2-story connecting corridor with class rooms building of which 1st story is RC
and 2nd story is steel structure with total floor space of 382m2.
East portion of Building “A” and 1st floor of Building “D” was constructed at 2973, East portion ofBuilding “B” and Building “C” was constructed at 1974, and west portions of Building “A” and “B”,
and 2nd floor of Building “D” was constructed at 1975.
Outline of damage
Overview of Building “A” is shown on Fig.1, and 1st floor plan with damage indexes of columns andwalls is shown in Fig.2.
The north frame of the building was severely damaged, and the columns of the special classroom at
the west end of the building on the 1st floor failed in shear with its damage index of V. Window framesby the sides of the column deformed due to its vertical shortening as shown in Fig.2
On the other hand, the shear wall at the west end of the building suffered no serious damage as shownin Photo 3. Some girders with standing wall in the north frame failed in shear. Floor level of Building“A” was 15cm lower than building “C”.
The minimum residual seismic capacity index “R” according to Japanese Guidelines for Damage
Classification was 33.3% for the longitudinal direction of the 1st floor. The building was evaluated as“severely damaged” according to the index.
The school is on a small hill, and all four buildings suffered moderate or severe damages. The damagelevel is much higher than another school buildings located just at the foot of the hill. Further researchsuch as pushover analysis is needed to investigate seismic capacity of the buildings. The JMA seismic
intensity measured around the school was 5-.
Constructed at 1973
Constructed at 1974
Constructed at 1975

Gym.

Build. B

Gym.

Fig. 1 Location of buildings

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Build. D
Entrance

Build. C

Build. AFig. 2 Overview of Building “A”

Fig. 3 Shear failure of the first story column at north frame of Building “A”

Fig. 4 West side view of Building “A”

7500

Y1216000

Y13

2500

6000

Y14

Y11
N
4500

4500

4500

4500

6000

4500

4500

4500

4500

4500

4500

4500

4500

6000

66000

X1

X2

X3

X4

X5

X6

X7

X8

X9

X10

X11

X12

X13

Fig. 5 Plan and damage grade of structural members of Building “A”

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X14

X15

１階平面図

ANALYSIS OF THE BUILDING

Outline building modelThis structure has columns, beams and shear walls as earthquake resistant elements. In longitudinaldirection (X axis), the earthquake resistant structure is conformed by moment-resisting frames, whilein transversal direction (Y axis), the earthquake resistant structure is conformed by a combination ofshear walls and moment-resisting frames, shown in Fig.6 and Fig.7.

Fig. 6 Frame model of the Building A

Fig. 7 Section model of the Building A
Elements of this structure are replaced by models, shown in Fig.8 and Fig. 9, and their plastic hingesare located at 1/4 of length from the end of each member. Each wall plane is connected by rigid beams,
and the last to the adjacent floor, therefore it is considered as a rigid diaphragm. Bending moment andshear force are considered in frames and shear walls to provide the nonlinearity.
Shear Spring

Plastic Spring

Elastic

Elastic

Plastic Spring

Fig. 8 Line model of the column and beam1212

Flexural Spring
Shear Spring
Flexural Spring

Fig. 9 Line model of the shear walls
The external force distribution to conduct the static analysis (pushover) has the triangular shape.
Restoring Force Characteristics
Trilinear model is assumed as the restoring force model for the flexural spring model and shear springmodel, shown in Fig. 10.

QQy

Q
Qy
α・K2
Bα2・KB

MMyM
MyMc

M
αc1・KB α1・KB

Qc β1・KB β1・KB

Qc

αy・KB αy・KB

Ks

Ks

τc y τyτc K τ

KB

β2・KBβ2・KBγc γcγy γyB：Yield point：CrackFig. 10 Restoring force model：crack point：crack point：yield point：yield point

RESULTS OF NONLINEAR STATIC ANALYSIS
Fig. 15 shows the shear damage pattern in the Building A by observation after the Great East Japan
Earthquake, which is described in Fig. 11.
ⅠⅡForce

YieldⅢⅣ

Ultimate

Crack
Displacement

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ⅤCollapse

Fig. 11 Seismic performance level
The inverted triangular external force distribution along the building height conducts the nonlinear
static analysis of the structure. The purpose of this study is to analyze the most affected structure(Building A) in the weakest direction (X axis). The shear force and relative story displacement of theBuilding A is show in Fig, 12.
Furthermore, damage state of the drift angle 1/50 is show in the Fig.14, the damage pattern in theBuilding A by mean of observation is shown in the figure.15, collapse mechanism of the Building A by
the shear force is shown in Fig. 16.

16000
0.41

14000

Shear Force(kN)

0.31
10000
0.26
8000
0.20
6000
0.15
1st Yield Point

4000

R=1/100
R=1/200

2000

R=1/50

1F
2F
3F
4F

001020

30

4050

60

Relative Story Displacement(mm)Fig. 12 Capacity curve of the Building AFig. 13 Framing elevation of the Building A (Y13-Frame)

1214700.100.05

Base Shear Coefficient

0.36

12000

Fig. 14 Hinges pattern in the Building A by analysis (Y13-Frame; R1=1/50)

Fig. 15 Shear damage pattern in the building A by observation

Fig. 16 Collapse mechanism in the Building A by shear force

CONCLUSIONSThis study conducted a nonlinear static analysis in an existing RC school building in Fukushima,
which was damaged by the Great East Japan Earthquake.
Results show a slightly difference between collapse stage of structure (R=1/50) and the actual
damages pattern obtain by observation.
Time-history analysis is needed in order to acutely study the dynamic behavior of this type ofstructures under strong ground motions.
REFERENCES
Technical Manual for Seismic Evaluation and Seismic Retrofit of Existing Reinforced Concrete
Buildings, 2001. Translate by Building Research Institute, and published by The Japan Building
Disaster Prevention Association.

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