Journal of Natural Disaster Science, Volume 35, Number 1, 2014, pp1-20

Seismic assessment of Japanese traditional wooden structure
by dynamic interaction numerical analysis of surrounding groundHisakazu SAKAI*
Kazuyuki IZUNO**
Kazunari SAKO***
Takahiro ENDO****
Ryoichi FUKAGAWA**
Kenzo TOKI******Department of Civil and Environmental Engineering, Hosei University**Department of Civil Engineering, Ritsumeikan University***Department of Ocean Civil Engineering, Kagoshima University****Nagoya Construction Division, Meiko Construction Co., Ltd.
*****Institute of Disaster Mitigation for Urban Cultural Heritage, Ritsumeikan University(Received September 10, 2013 Accepted March 17, 2014)
ABSTRACT
We conducted seismic evaluations of a traditional wooden building using threedimensional earthquake response analyses. The building is registered as one of the “Historic
Monuments of Ancient Kyoto”, UNESCO World Heritage Site, and is located in a regionof strong earthquake motion from a scenario earthquake. The structure is an invaluableasset, but it is at risk of damage resulting from earthquake. Our numerical estimation was
based on a dynamic interaction analysis between the building and the surrounding groundbecause it was located on the slope of a hill with complicated geophysical features. We
also conducted a dynamic non-interaction analysis of the structure for a comparison withthe aforementioned interaction model. Boring explorations and geotechnical tests wereconducted before the assessment in order to investigate the ground foundation. We included
the surrounding ground for a more realistic analysis because the seismic estimation for amodel consisting only of the main structure differs significantly from that of the structureground coupling model. The results showed that the main wooden building was at risk ofpartial damage as it exceeded the safety limits prescribed for a scenario earthquake, andwould collapse in the case of double the amplitude of the scenario earthquake.
Keyword: seismic estimation, earthquake response analysis, traditional wooden structure,scenario earthquake, soil-structure interaction.

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H. SAKAI, K. IZUNO, K. SAKO, T. ENDO, R. FUKAGAWA, K. TOKI

1. INTRODUCTION

However, these studies estimated the seismic performance of a traditional wooden structure with a model
consisting of only the building. This seems to be particularly important for a traditional wooden building
with a stage on the slope of a hill located in complex
topography. Toki et al. (2013) examined the performance based on the dynamic structure-ground interaction. However, the response of the main structure
must be estimated with higher frequency than the actual response, because they used the linear stressstrain model for the structure and the perfectly elastoplastic constitute model for the surrounding soil.
Therefore, we conducted non-linear three-dimensional
numerical simulations for the building during scenario
earthquakes using a non-linear constitute model forthe structure and the Ramberg-Osgood type curvilinear model for the ground.

In Japan, a large number of traditional woodenbuildings have managed to escape many natural andartificial disasters, and most of them are concentrated
in the Kinki region, situated in the western region of
Honshu, the main Japanese island. The Central Disaster Management Council of Japan (2008.2) reportsthat many of these cultural heritage buildings are located in regions that have strong ground motion. Recently, many studies on seismic assessments of traditional wooden structures in Japan have been
performed. Fujita et al. (2004) discussed the vibration
characteristics of a newly built traditional timber pagoda based on the results of earthquake monitoringand micro tremor measurements. Fujita et al. (2008)
conducted analyses for shaking table tests conducted
for a traditional timber pagoda in 2004-2006. Mori etal. (2007) showed the effect of axial force fluctuationof supporting columns for the seismic performance ofthe main wooden building of this study by conducting
three-dimensional nonlinear earthquake response
analyses. Suzuki et al. (2007) examined the effect of astage on the earthquake response of the traditional
structure and showed that non-rigid floor assumption
affects the response of the stage of the structure.

2. IN-SITU INVESTIGATION
The main building with a wooden stage is located on the slope at the foot of a mountain and in complex topography as mentioned above, and there areseveral stone masonry walls around the building (seeFig.1). We conducted three boring investigations
around the main building at the locations of B1, B2N

wooden stage

mainbuilding

Figure 1. Positions of boring investigations. Stone masonry walls are indicated by the gray area.
2

SEISMIC ASSESSMENT OF JAPANESE TRADITIONAL WOODEN STRUCTURE BY DYNAMIC INTERACTION NUMERICAL ANALYSIS OF SURROUNDING GROUND

and B3 shown in Fig.1. The standard penetration tests
were conducted at each borehole. Figs.2–4 show theboring logs obtained from these examinations. The
investigations at B1 were conducted on the slope under the main wooden stage of the building. The Nvalues for B1 were greater than 60 at the soil layer
more than 10 m below the surface, and the groundwater surface existed at a depth of 5.5 m below the

0

10

20

30

40

50

ground surface. Laboratory soil tests using the boringcore were also conducted to estimate the soil properties at B1. Soil particle density, grain size distribution,
classification of geomaterials, and consistency arelisted in Table 1. A standard penetration test at B2
showed that the N-Values are greater than 50 at thesoil layer more than 7 m below the surface, and theground at B2 seemed relatively stable. There is no
ground water surface at B2. The point B3 of the boring investigation and standard penetration test was located on the lower part of the slope on which the main
structure stood. The N-Values of B3 were less than 30
in most layers, and the bedrock did not appear in theboring core. Based on these in-situ investigation results (see Architectural Research Association: Reportof survey of existing circumstances at main buildingof Kiyomizu temple and 8 other buildings (2007) for
more information) and laboratory soil tests, the parameters of numerical simulation were estimated.

60

0
B1

Depth [m]

5

10

138

15

600
600
360
360
257
450

3. METHODOLOGY
We evaluated the safety of the main traditional
wooden building based on three-dimensional finite element method (FEM) analysis (SoilPlus, CTC, ITOCHU Techno-Solutions Corporation, Japan), whichused the 3D elements of ground and structure with
non-linear properties. In addition, we compared the20
N-Value

Figure 2. The result of standard penetration test at
B1.
0

10

20

30

40

50

0

60

20

30

40

50

60

0

0
2

10

B2

B3

2

6

Depth [m]Depth [m]

4

70

8

63
68
68
63
63
79
75

10
12
14
16

4

69

6

8

10

N-Value

N-Value

Figure 3. The result of standard penetration test at
B2.

Figure 4. The result of standard penetration test at
B3.
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H. SAKAI, K. IZUNO, K. SAKO, T. ENDO, R. FUKAGAWA, K. TOKI

Table 1. Soil properties of boring core obtained at No. B1 in
No.
Depth [G.L.-m]
3

Soil particle density [g/m ]Natural water content [%]Grain size distribution

1

2

3

4

5

2.15 - 2.55

4.15 - 4.45

6.15 - 6.45

8.15 - 8.45

11.15 - 11.45

2.577

2.623

2.655

2.663

2.653

51.3

30.1

18.7

11.8

14.3

Gravel fraction [%]

21.9

35.9

30.0

6.6

6.7

Sand fraction [%]

27.2

29.9

37.4

54.7

52.2

Silt fraction [%]

32.0

25.4

16.9

26.6

21.2

Clay fraction [%]

18.9

8.8

15.7

12.1

19.9

Uniformity coefficient-

227.68-147.96-

Coefficient of curvature

-

0.33

-

0.99

-

Cohesive sandy gravel

Cohesive gravelly sandCohesive sand including gravel

Cohesive sand including gravel

SCsG

SCs-G

SCs-G

Classification of geomaterials

Sandy and gravelly clay
CLSG

GCsS

Consistency
Liquid limit WL [%]

40.1

-

-

-

-

Plastic limit WP [%]

22.9

-

-

-

-

Plasticity index

17.2

-

-

-

-

results from the analysis of a model consisting only of
the building (structure model) with that of a structureand ground coupling model (coupling model) in orderto propose an appropriate methodology for a seismic
assessment of a valuable structure located in complex
topography.

1633 following a fire (see Fig.5). Suzuki et al. (2007)
conducted a field investigation, and clarified the profiles, section size of the support columns, clay walls,
slabs and penetrating beams, and plain and side view.
The plain and section views are shown in Figs.6 and7, and the analytical FE model is shown in Fig.8. We
assumed that the columns, penetrating beams andslabs are linear beams, column feet, penetrating tie
beams and joints are nonlinear rotational and horizontal springs, and substitute clay walls, stage floor androof are linear braces. Japanese cypress was used forthe stage floor; for the others, a type of zelcova wasused. The elastic and shear modulus of the cypress
were 5880 N/mm2 and 390 N/mm2, and those of zelcova were 8800 N/mm2 and 590 N/mm2, respectively.
The nonlinear spring properties are shown in Table 1.

3.1 Analytical model(1) Main traditional wooden building
The main wooden structure with the stage wasconstructed on the slope at the hill. Forty- eight talland short columns support the overhanging part of thestage. The area of the structure is about 1170 m2, theheight of the main building is about 18 m, and theheight of the stage is about 13 m at the tallest support
column point. The structure had been reconstructed in

Figure 5. Main wooden structure with stage.
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SEISMIC ASSESSMENT OF JAPANESE TRADITIONAL WOODEN STRUCTURE BY DYNAMIC INTERACTION NUMERICAL ANALYSIS OF SURROUNDING GROUND

Y11pent roof

Y12pent roof

pent roof

Y13

Y10

room forenshrined Buddaha

Y9central room

Y6

aisle

Y7

worship space

Y5

aisle

Y8

aisle

Y4
Y3
Y2

stage

Y1

X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12 X13 X14
Figure 6. Plain view of the main structure.

wooden stage

kakezukuri

Figure 7. Section drawing of the main structure. (From AIJ: Architectural Design Data Corpus, Vol.10, Technology)
For more details of these properties, see (Suzuki et al.
2007). The appropriateness of the model was confirmed by comparing the numerical natural frequencies of the analytical model and the microtremor measurements by Suzuki et al. (2007). The first natural

frequencies were 1.6 Hz and 1.8 Hz in the NorthSouth direction, and the second were 1.7 Hz and 1.9
Hz in the East-West direction, respectively. The deformation mode shapes of the structure at natural frequencies are shown in Fig.9.
5

H. SAKAI, K. IZUNO, K. SAKO, T. ENDO, R. FUKAGAWA, K. TOKI

Figure 8. Finite elemental model of the main structure.

N(a) The first natural deformation mode shape of the main building. The deformation mode shape trends predominantly N-S.

(2) Surrounding groundWe created the ground model for the shallow
sediments in the engineering basement. The area ofthe model with East-West and North-South lengths of
320 m and 300 m, respectively, was more than twice
the width of the main structure. S-wave velocity inthe engineering basement was 750 m/s, since the input ground motion on the basement was calculated as

per Toki et al. (2007) under the condition that its Swave velocity was exceeded 700 m/s (see Fig.10). We
determined the characteristics of the layers by reference to the in-situ investigation of Chapter 2 and othersurveys (Kuwata, 2009; Kyoto city government,
2003). For example, the surface shear wave velocities
were determined based on the results of the shallow
shear wave velocity sounding by Kuwata, the internal
6

SEISMIC ASSESSMENT OF JAPANESE TRADITIONAL WOODEN STRUCTURE BY DYNAMIC INTERACTION NUMERICAL ANALYSIS OF SURROUNDING GROUNDN(b) The second natural deformation mode shape of the main building. The deformation mode shape trends predominantly E-W.
Figure 9. Predominant deformation mode shapes.

Table 2. Properties of nonlinear springs.
Section

Property type

Rotation of foot of support column

Tri-linear elastic

Rotation between column and penetrating beam

Nonlinear elastic

Rotation between top of column and beam

Nonlinear elastic

Rotation of penetrating tie beam

Nonlinear elastic

Horizontal spring

Normal bi-linear

Horizontal spring of foot of support column

Joint element

friction angles, cohesions and unit weight of the surface ground were defined with the results of the laboratory test by Sako, and the deep ground structure wasset based on the report by Kyoto city government. For
evaluations of the ground, we consulted the results of
the in-situ investigation of Chapter 2. The geologicalproperties were classified into mountainous or nonmountainous areas as shown in Tables 3 and 4, andwere applied as the Ramberg-Osgood type non-linear
characteristics except elements for the stone masonrywalls. Herein, tetrahedron and pentahedron elements
arranged on the ground surface were also assumed aslinear elasticity considering the accuracy of those elements with non-linear properties on the FEM code.
The linear characteristics of the element for the stone
masonry wall were calculated in proportion to thewall volume in the element.
(3) Structure and ground coupling model
As mentioned above, the main wooden building
was built on a slope with a stage supported by 48 talland short columns; hence, a different input motion
should be incident for each support column. On theother hand, a dynamic interaction spring is generally
used between the structure and ground in architectural
seismic estimations in order to express the radiation
damping as well as the effective input motion to thestructure. However, the characteristics of the springstrongly influence the response solutions in spite ofthe difficulty of the adequacy of the data set. Due tothese reasons, we adapted this coupling model for theseismic estimation of the structure. The structure is7

H. SAKAI, K. IZUNO, K. SAKO, T. ENDO, R. FUKAGAWA, K. TOKI

N

Layer (Table 3)2
4
5

mountainous area
non-mountainous area
Figure 10. Surrounding ground model. Red elements indicate stone masonry walls and the high stage of the main
structure is built on the slope (white ellipse at the center of the model).

Table 3. Geological properties of sediment layers of non-mountainous area.
1-1(except 1-2)

Layer

1-2
(beneath stage)

2

3

4

5

Depth (m)

0–6

0–6

6–20

20–25

25–38

38–63

Unit weight (kN/m3)

18.0

18.0

18.0

19.6

20.6

22.5

S-wave velocity (m/s)

250

155

330

400

500

600

Poisson’s ratio

0.33

0.23

0.36

0.45

0.45

0.45

2

252

90.0

450

946

1550

2880

Shear modulus G(MN/m )

96.0

36.4

165

327

536

992

Cohesion (kN/m )

0

0

0

5.0

5.0

5.0

Friction angle (deg.)

35

30

38

40

45

48

Elastic modulus E(MN/m )2

2

Table 4. Geological properties of sediment layers of mountainous area.
Layer

6(subsurface)

7(under subsurface)

Unit weight (kN/m3)

17.6

22.5

S-wave velocity (m/s)

200

600

Poisson’s ratio

0.33

0.45

2

195

2880

Shear modulus G(MN/m )

73.5

992

Cohesion (kN/m )

14

5.0

Friction angle (deg.)

19

48

Elastic modulus E(MN/m )2

2

8

SEISMIC ASSESSMENT OF JAPANESE TRADITIONAL WOODEN STRUCTURE BY DYNAMIC INTERACTION NUMERICAL ANALYSIS OF SURROUNDING GROUND

connected to the slope of the surrounding groundmodel by joint elements. Figure 11 shows the main
structure and ground coupling model.

sional earthquake response analysis with non-linear
properties of the ground. We adapted the ground motions at the surface and basement for the seismic assessment of the structural model and coupling model,
respectively. Both motions included two horizontal
components, the E-W and the N-S directions. The
four input acceleration components are shown in
Figs.12 and 13. For reference purposes, the Fourier

3.2. Input ground motion
Toki et al. (2007) estimated the ground motion
around the traditional structure from a scenario earthquake of the Hanaore Fault based on a three-dimen-

N

Figure 11. Main wooden structure and surrounding ground coupling model.

Acceleration (Gal)

1000
500
0
-500

-1000

0

1

2

3

4
Time (s)

5

6

7

8

1

2

3

4
Time (s)

5

6

7

8

E-W component

Acceleration (Gal)

1000
500
0
-500

-1000

0

N-S component
Figure 12. Input ground motion in the basement for the structure-ground interaction model.
9H. SAKAI, K. IZUNO, K. SAKO, T. ENDO, R. FUKAGAWA, K. TOKI

Acceleration (Gal)

1000
500
0
-500

-1000

0

1

2

3

4
Time (s)

5

6

7

8

1

2

3

4
Time (s)

5

6

7

8

E-W component

Acceleration (Gal)

1000
500
0
-500

-1000

0

N-S component
Figure 13. Input ground motion in the basement for the structure model.

spectra of these input motions are shown in Fig.14
and 15. For the assessment of the coupling model, we
assumed double the amplitude of the input groundmotion in the basement as well as the original amplitude from a scenario earthquake.
The seismic evaluation for the three cases above
was conducted not only to examine the safety of themain wooden structure during a scenario earthquake,but also to propose an appropriate analytical model
for a structure with a stage constructed in complex topography.

dynamic analysis, respectively. Meanwhile, the foundation side of the joint element arranged at the foot of
the support column is pin support for the initial stressand the dynamic analysis. In adapting the stiffness
proportional damping characteristic for the earthquake
response analysis, the damping factor of elastic soil
elements was equal to 15% and that of elasto-plastic
elements was 2% for the fundamental mode. The
Newmark-beta method (beta = 1/4) was used to solve
equations of motions for a total analytical time ofeight seconds with a time interval of 2/1,000 seconds.

3.3. Analytical conditions
We conducted non-linear static analysis for the
structure and the coupling models before the earthquake response analysis. As some elements with elasto-plastic characteristics are subjected to the stresscondition, the initial stress condition of the elements
should be calculated before the dynamic response
analysis. For the coupling model, the vertical slide
boundaries for the four lateral faces (Eastern, Western, Northern and Southern edges of the model) wereadapted for static analysis and the horizontal faces for
dynamic analysis, and the bottom face was a rigid
boundary for static analysis and viscous boundary for

4. SEISMIC ASSESSMENT FOR MAINWOODEN STRUCTURE BASED ON
EARTHQUAKE RESPONSE ANALYSIS
4.1. Structure modelFirst, we estimated the damage of the mainwooden structure during the scenario earthquake
based on the earthquake response analysis for the
structure model generally used for architectural seismic assessment. We focused the responses on twosites: the front edge of the stage (X8Y1 in Fig.6) andthe top of the support column at the center of the mainbuilding (X8Y8 in Fig.6), and the distribution of ab10

SEISMIC ASSESSMENT OF JAPANESE TRADITIONAL WOODEN STRUCTURE BY DYNAMIC INTERACTION NUMERICAL ANALYSIS OF SURROUNDING GROUND

Fourier Spectrum (Gal.s)

25

20

15

10

5

0
0.1

1

10

Frequency(Hz)E-W component

Fourier Spectrum (Gal.s)

25

20

15

10

5

0
0.1

1

Frequency(Hz)10N-S component
Figure 14. Fourier spectra of the input ground motion at the basement for the structure-ground interaction model.

solute peak acceleration, and compared them withthose of another case mentioned in Section 4.2. The
two absolute peak values are shown in Table 5, andthe distribution of the acceleration component of E-W
and N-S directions is shown in Fig.16. As shown in
Table 5 and Fig.16, we found that the main wooden
structure responded heavily; the peak accelerations ofboth components of E-W and N-S directions exceeded
1 G at the stage, and with respect to E-W components

at the top support column of the main structure, thepeak response velocity and acceleration exceeded 100
kine and 1 G, respectively. The N-S components of
response displacement and velocity are significantly
small at the front edge of the stage. This is because
the stage is almost the same level as the floor of themain hall whose support columns are anchored to the
fixed points. The deformations of expansion and contraction of the stage are very slight because the stage
11

H. SAKAI, K. IZUNO, K. SAKO, T. ENDO, R. FUKAGAWA, K. TOKI

Fourier Spectrum (Gal.s)

40

30

20

10

0
0.1

1

10

Frequency(Hz)E-W component

Fourier Spectrum (Gal.s)

40

30

20

10

0
0.1

1

10

Frequency(Hz)N-S component
Figure 15. Fourier spectra of the input ground motion at the basement for the structure model.

Table 5. The absolute peak response values at the front edge of the stage and the top of the support column at thecenter of the main wooden structure.
Front edge of the stage
Directional component

E-W

Top of support column

N-S

U-D

E-W

N-S

U-D

Displacement (cm)

3.8

0.4

0.002

13.7

5.9

0.005

Velocity (kine)

52.1

9.5

0.04

144

61.5

0.1

Acceleration (Gal)

1528

1331

1.4

1249

733

5.6

12

SEISMIC ASSESSMENT OF JAPANESE TRADITIONAL WOODEN STRUCTURE BY DYNAMIC INTERACTION NUMERICAL ANALYSIS OF SURROUNDING GROUNDN

E-W directional componentN

N-S directional component
Figure 16. Distribution of absolute peak response acceleration of the main wooden structure (Unit: m/s2).

was built as a plate structure. Therefore, the movement of N-S direction of the stage is controlled by thefloor of the main hall. Herein, a frequency of about
1.8 Hz was outstanding at the top of the support column in both horizontal components, and a frequency
from 2.5–4 Hz and frequencies of 2 Hz, 3.5 Hz and6.5 Hz were dominant in E-W and N-S components at

the front edge of the stage, respectively. For reference
purposes, the distribution of the displacement component of E-W and N-S directions is shown in Fig.17.
4.2. Coupling model
In this section, we conducted the seismic assessment for the main historic building based on the cou13

H. SAKAI, K. IZUNO, K. SAKO, T. ENDO, R. FUKAGAWA, K. TOKI

N

E-W directional componentN

N-S directional component
Figure 17. Distribution of peak response displacement of the main wooden structure (Unit: m).

pling model. The results of the earthquake response
analyses are shown in Table 6 and Fig.18.
As shown in Tables 5 and 6, the E-W and N-S
components of the response acceleration of the coupling model at the center of the top column exceed 1
G and are larger than those of the structure model.
The reason is that the building stands at the foot of themountain and the response accelerations at the location of the main building are amplified on behalf ofthe ground with the three-dimensional irregular interface. In contrast, at the front of the stage, the response
accelerations of the coupling model are smaller thanthose of the structure model. This is attributed to thephase difference of the input motion for the columns
14

SEISMIC ASSESSMENT OF JAPANESE TRADITIONAL WOODEN STRUCTURE BY DYNAMIC INTERACTION NUMERICAL ANALYSIS OF SURROUNDING GROUND

Table 6. The absolute peak response values at the front edge of the stage and the top of the support column at thecenter of the main wooden structure. (Single amplitude)
Front edge of the stage

Top of support column

Directional component

E-W

N-S

U-D

E-W

N-S

U-D

Displacement (cm)

10.1

5.3

1.1

21.3

11.1

2.1

Velocity (kine)

111.3

60.7

11.9

171.9

84.6

25.1

Acceleration (Gal)

1307

691

293

1567

946

542

N

E-W directional componentN

N-S directional component
Figure 18. Distribution of absolute peak response acceleration of the structure and ground coupling model (Single
amplitude) (Unit: m/s2)
15

H. SAKAI, K. IZUNO, K. SAKO, T. ENDO, R. FUKAGAWA, K. TOKI

N

E-W directional componentN

N-S directional component
Figure 19. Distribution of peak response displacement of the structure and ground coupling model (Single amplitude) (Unit: m)
supporting the stage. For reference purposes, the distribution of the displacement component of E-W and
N-S directions, the response accelerations of theground surface at the main hall (room for enshrined
Buddha) and the Fourier spectra are shown in Figs.1820, respectively. As shown in Figs.18, 20 and 21, thepeak response accelerations of the ground surface at
the main structure are marginally larger than the peak
input accelerations of the structure model, but thedominant frequencies of those are reduced to 1.2-1.5
Hz.

4.3. Seismic evaluation for main wooden
structure
We estimated the damage of the historical main
structure based on the maximum inter-story deflection
angle of the first floor. Herein, the deflection angle ofthe damage limit for high-frequency low-impact
earthquakes was assumed to be 1/120 radian based on
the Japanese Building Standards Act (2011), and thatof the safe limit for low-frequency high-impact earthquakes to be 1/30 radian based on the seismic guideline for important cultural properties of the Japanese
Agency for Cultural Affairs (2001). The maximum in16

Acceleration.(Gal)SEISMIC ASSESSMENT OF JAPANESE TRADITIONAL WOODEN STRUCTURE BY DYNAMIC INTERACTION NUMERICAL ANALYSIS OF SURROUNDING GROUND

1000
500
0
-500
-1000

0

1

2

3

4

5

6

Time(s)

Acceleration (Gal)E-W component

1000
500
0
-500
-1000

0

1

2

3

4

5

Time(s)6

N-S component
Figure 20. Earthquake response acceleration of the ground surface at the main building for the coupling model.

Fourier Spectrum (Gal.s)

40

30

20

10

0
0.1

1
Frequency(Hz)E-W component

17

10



H. SAKAI, K. IZUNO, K. SAKO, T. ENDO, R. FUKAGAWA, K. TOKI

Fourier Spectrum (Gal.s)

40

30

20

10

0
0.1

1
Frequency(Hz)10N-S component
Figure 21. Fourier spectra of the response acceleration of the ground surface at the main building for the coupling model.
ter-story deflection angle was calculated as the relative displacement between the top and the bottom of
the support column divided by a height of 4.5 m. The
maximum deflection angles of the E-W and the N-S
directions at X3 and Y12 lines (see Fig.6) are shownin Fig.22. Figure 22 indicates that the inter-story deflection angle on the structure model is 0.5–0.8 times
that on the coupling model. That means that we havethe potential to overestimate the seismic safeness ofthe main structure in the case of the structure model.
Non-negligible damage of the main wooden structure,especially in the E-W direction, is anticipated during
a scenario earthquake of the Hanaore Fault, because
the inter-story deflection angle is estimated to partly
exceed the safe limit. The ground motion of the scenario earthquake is not so accurate that we could havedouble or half the amplitude of the input acceleration.
On the condition that we have double the ground motion of the scenario earthquake, the maximum deflection angles of most columns were larger than the safe
limit of the structure and the structure was in dangerof collapse.

three-dimensional non-linear earthquake response
analysis for two analytical models against the scenario earthquake from the Hanaore Fault. One model wasconstructed solely for the main structure (structure
model) and the other for the structure and surrounding
ground with irregular geometry (coupling model).
The salient results obtained from our estimations are
as follows:
1. The seismic capacity of the main wooden
structure based on the structure model is overestimated, because the inter-story deflection
angle of the first floor based on the model is
0.5–0.8 times that of the coupling model.
Therefore, it is very important for a valuable
structure built on a slope at irregular geometry
and in rugged terrain to estimate the seismic
safety with the structure-ground coupling
model.
2. From the computational results for the coupling model, we estimated that the damage ofthe main building partly transcends the safety
limit during the scenario earthquake. The
building stands a risk of collapsing during
double the amplitude of the scenario earthquake, because the maximum inter-story de-

5. CONCLUSIONS
We conducted seismic assessment of a main traditional wooden building with a stage based on the18

SEISMIC ASSESSMENT OF JAPANESE TRADITIONAL WOODEN STRUCTURE BY DYNAMIC INTERACTION NUMERICAL ANALYSIS OF SURROUNDING GROUND

Maximum deflection angle (rad)

0.07
0.06

Safe limit
Damage limit
Structure model (Single amp.)
Coupling model (Single amp.)
Coupling model (Double amp.)

0.05
0.04
0.03
0.02
0.01
0

2

3

4

5

6

7

8

9

10

11

12

13

Y-line number(a) E-W component of X3-line

Maximum deflection angle (rad)

0.05
0.04

Safe limit
Damage limit
Structure model (Single amp.)
Coupling model (Single amp.)
Coupling model (Double amp.)

0.03
0.02
0.01
0

3

4

5

6

7

8

9

10

11

12

13

14

X-line number(b) N-S component of Y12-line
Figure 22. Maximum deflection angle of main wooden structure.

flection angles of most of the support columnson the first floor exceeded the safety limit.

on Earthquake Engineering, 54, CDR.
Fujita K, Chiba K, Kawai N, Kshihara M, Minowa C and
Hanazato T., 2008. Earthquake Response Analysis of

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20