17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020
Paper N° 002285
Registration Code: S-A00801

Stiffness, Ultimate Strength Capacity and Cyclic Loading Deterioration
Characteristics of Two Different Wood-Structure Dwellings Following The
Current Japanese PracticeT. Takahashi(1), T. Nagae(2), S. Uwadan(3), C. Yenidogan(4)(5), S. Yamada(6),H. Kashiwa(7), K. Hayashi(8), T. Inoue(9)(1) Senior Researcher, NIED, takehiro@bosai.go.jp(2) Associate Professor, Nagoya University, nagae@nagoya-u.jp(3) Graduate Student, Nagoya University(4) JSPS Fellow, Nagoya University, cem.yenidogan@gmail.com(5) Assistant Professor, Bahçeşehir University, cem.yenidogan@eng.bau.edu.tr(6) Associate, NIKKEN SEKKEI LTD, shohei.yamada@nikken.jp(7) Senior Researcher, NILIM, kashiwa-h92ta@mlit.go.jp(8) Assistant Professor, Toyohashi University of Technology, hayashi@ace.tut.ac.jp(9) Deputy Director, NIED, dinoue@bosai.go.jp

Abstract
Two Grade-3 index buildings were designed and constructed according to the current Japanese seismic design guidelines.
One was a Post-and-Beam Structure (A-building), and another a Shear-Wall structure (B-building). The sills, columnbases and wall bases were anchored to reinforced concrete foundations by steel anchor bolts, thereby fulfilling theguideline requirements. The foundations were firmly fixed, and shaking table motions were fully applied to thefoundations. JMA-Kobe motion and JR-Takatori motion recorded in the 1995 Kobe earthquake were used for the ultimate
state tests. The two test buildings had stiffness more than two times higher than the design evaluations. The ultimate
strength capacities were more than four times that of the allowable stress design capacity.
Keywords: Shaking table test, Wood house, Soil-structure interaction, Functionality, Base isolation

1. Introduction
Comprehensive seismic performance assessment of wood dwellings located in densely populated urban areas
was selected as a target of the current E-Defense tests regarding the Tokyo Metropolitan Resilience Project(2017-2022). “The 2019 full-scale shake table test program of wood dwellings” is summarized with the entire
test results.[1] This paper focuses on the evaluations of stiffness, ultimate strength capacity and cyclic loading
deterioration characteristics of two different wood buildings shown in Fig. 1.

(1) Construction site (outside west yard)(2) Completion of setups in E-Defense

Fig. 1 Construction and setup of two wood test buildings (January, 2019)17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

Two test buildings were designed according to the current Japanese design guidelines. One was a Postand-Beam Structure (A-building), and another a Shear-Wall structure (B-building). The upper structures wereplaced on stiff reinforced concrete foundations. The foundations were designed by assuming general soil
properties. The sills, column bases and wall bases were anchored by steel anchor bolts, thereby fulfilling thecurrent guideline requirements. The foundation slabs were firmly fixed so that shaking table motions were
fully applied to the foundation slabs.

2. Test Building
Figure 2 shows the plans of the first, second and third floors adopted for both A-building and B-building. The
two test buildings had identical configurations and plans. Regarding the Post-and-Beam Structure (A-building),braces were fixed by metal connection reinforcement. Structural plywood was fixed by nails. The exterior wall
was finished by siding boards. Gypsum board was fixed by screws to the interior side. The exterior wall wasfinished by wall cloth. The Shear-Wall structure (B-building) adopted prefabricated wall panels composed ofa vertical frame, lateral frame and plywood. The siding board, gypsum board and wall cloth were the same inboth test buildings. Figure 3 shows the construction process of the test buildings.
Y-direction

X-direction

1st floor

2nd floor

3rd floor

Fig. 2 Plans of A-building and B-building(1) Post-and-Beam Structure / A-building(2) Shear-Wall Structure / B-building

Fig. 3 Construction process of two test buildings (Photos: November-December, 2018)2

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020

Table 1 shows the seismic force used in the designs of A-building and B-building. Figure 4 shows theframing elevation. For both buildings, the design of the Grade-3 index building was adopted so that the strength
Table 1 Seismic force in the designA-building

AiShear force coefficient
Ci

Seismic forceeQi (kN)

3rd story

Total weightwi (kN)
79.57

1.603

0.481

38.25

2nd story

230.88

1.207

0.362

83.63

1st story

382.22

1.000

0.300

114.67

B-building

Total weightwi (kN)
79.91

Ai

Shear force coefficient
Ci

Seismic forceeQi (kN)

1.60

0.480

38.32

3rd story
2nd story

226.83

1.21

0.363

82.31

1st story

376.50

1.00

0.300

112.95(1) A-building (Post-and-Beam Structure)(2) B-building (Shear-Wall Structure)

Fig. 4 Framing elevation

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Sendai, Japan - September 13th to 18th 2020

(1) A-Building(2) B-building

Fig. 5 Locations of steel anchor bolts holding column basemargin to the requirements was minimized. That is, the design stress level to the base shear force coefficientof 0.3 became close to the allowable stress level. Through past experiences of failure modes due to lack ofconnection strength and column base strength, strict requirements concerning the metal reinforcement forconnections and steel anchor bolts holding the column base have been established. Figure 5 shows the locationsof steel anchor bolts holding the column base in blue. The equivalent allowable stress design procedures wereapplied to both the Post-and-Beam Structure (A-building) and Shear-Wall structure (B-building). As a result,the number of steel anchor bolts holding the column base became very different. This is because the tension
force in the column base was governed by different design models for the Post-and-Beam and Shear-WallStructures. The modeling of shear wall panels produced much smaller tension forces in the column bases.
Figure 5 (2) shows the locations of anchor bolts fixing the lateral sills to the foundation in red. A-building had
the same number of anchor bolts fixing sills to the foundation slab although they are not shown in Fig. 5 (1).
The shear wall panels were fixed to sills by nails and metal reinforcements in B-building.

3. Test Results of A-building
The test program was divided into three phases (Phase 1, Phase 2 and Phase 3), while keeping the same upper
structures of the Post-and-Beam Structure (A-building) and Shear-Wall structure (B-building).[1] A-building
was equipped with a base isolation structure in Phase 1. In such condition, the upper structure of A-building
had small drift angles of less than 0.003 rad. B-building was supported by a foundation on soil in Phase 1 andPhase 2.[2] Under such condition, the upper structure of B-building had modest drift angles of less than 0.018
rad. Regarding A-building, the foundation was firmly fixed in Phase 2, while in B-building, it was firmly fixedin Phase 3. JMA-Kobe motion and JR-Takatori motion were used for the tests. In Phase 2, JMA-Kobe 25%,JMA-Kobe 50%, JMA-Kobe 100% and JR-Takatori 100% were used. In Phase 3, JMA-Kobe 100% only wasused. The followingly planned tests were canceled because the ultimate failure occurred in B-building in thefirst test. This paper focuses on the tests of A-building in Phase 2 and the test of B-building in Phase 3.

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17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020

Figure 6 shows the acceleration response spectra of the records at the shaking table and foundation for Abuilding (Phase 2). The orange lines of the foundation are very close to the blue lines of the shaking table. Theinput motions to the shaking table were fully applied to the foundation.

(1) JMA-Kobe 100%(2) JR-Takatori 100%

Fig. 6 Acceleration response spectra evaluated at shaking table and foundation slab
(A-building of Phase 2)
The maximum inter-story drift angle was limited to less than 0.008 rad in JMA-Kobe 50%. JMA-Kobe
50% is equivalent to the Design-Based Earthquake. On the other hand, when subjected to JMA-Kobe 100%,
the response deformation was concentrated on the first story, and the drift angle exceeded 0.03 rad in the Xdirection. The maximum inter-story drift exceeded 0.04 rad in the following JR-Takatori 100%. Figure 7 shows
the typical damage to the first story after being subjected to JMA-Kobe 100%. In the X-direction, the siding
boards fractured in the exterior walls. Significant cracks started at the corners of windows in the interior
gypsum boards. In the JR-Takatori 100%, the siding boards spalled from the exterior walls, as shown in Fig.

Fig. 7 Damage to the first story of A-building in the story drift of 0.03 rad (JMA-Kobe 100%)5

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020

8 (1). Cracks progressed slightly in the interior walls under cyclic deformations, as shown in Fig. 8 (2). Notethat the steel anchor bolts holding the column bases showed maximum strain slightly exceeding 0.2%, andcolumn bases constraint vertical deformations due to tension forces. The first-story deformation comprised
mostly of story shear deformation.

(2) Cracks slightly progressed in the interior walls
under cyclic deformations(1) Fractured and spalled siding boards came off
in the cyclic drift angle of 0.04 rad

Fig. 8 Video capture of interior and exterior walls when subjected to JR-Takatori 100% (A-building)Figure 9 shows the relationships between story shear force and story drift angle in each story whensubjected to JMA-Kobe 100%. Regarding the first-tory relationship, significant inelastic behaviors are shown
from the drift angle of 0.01 rad in the X-direction. The maximum strength reached 600 kN at the drift angle of0.03 rad. Peak orienting shape and pinching shape are observed in the hysteretic loops. In the Y-direction, themaximum drift angle slightly exceeded 0.01 rad, and maximum shear force reached 400 kN. The maximumdrift angles were limited to less than 0.01 rad in the second story and less than 0.005 rad in the third story. The
maximum shear forces were less than 100 kN in both the X and Y-directions in the third story. Figure 10 shows
the relationships when subjected to JR-Takatori 100%. Pinching hysteretic loops are repeatedly depicted. InFig. 9 Relationship between shear force and drift angle in each story of A-building / JMA-Kobe 100%

617th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020

Fig. 10 Relationship between shear force and drift angle in each story of A-building / JR-Takatori 100%
the first story, the maximum shear force exceeded the values experienced in JMA-Kobe 100% on the negativeside in the X-direction and on both the positive and negative sides in the Y-direction.

3. Test Results of B-building
When subjected to JMA-Kobe 100%, the table input motion was fully applied to the foundation of B-building.
Figure 11 shows the ultimate failure states of B-building. Severe fractures of the wall base occurred at theinterface between shear wall panels and sills. Regarding the steel anchor bolts holding the column base, thescrews were completely pulled out from the column base. The overviews captured at the moment of the wallbase fractures (Fig. 12) indicated that the overturning moment due to significant inertia force in the Y-direction
uplifted the south exterior frame. The recorded maximum value of uplifting was more than 400 mm.

After testFig. 11 Wall base fracture at the south exterior wall and screws pulled out at column base(B-building after subjected to JMA-Kobe 100%)7

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020

At the moment of wall base fracture

Fig. 12 Overviews of B-building subjected to JMA-Kobe 100%
Figure 13 shows the relationship between the story shear force and drift angle of each story when Bbuilding was subjected to JMA-Kobe 100%. The maximum drift angle reached 0.08 rad in the X-direction,and exceeded 0.1 rad in the Y-direction. Such value was more than two times that of A-building in the Xdirection, and more than three times that of A-building in the Y-direction. The response deformations weresignificantly concentrated on the first story. In the large deformation ranges, steep negative slopes are depicted,
and the shear force decreased to less than 20% of the maximum shear force in each of the X and Y-directions.
Figure 14 shows the relationship between the overturning moment and rocking rotation angle at the wallbase level when subjected to JMA-Kobe 100%. The horizontal dotted line shows the resisting moment due tothe total weight of the upper structure. This is evaluated as the product of the total weight (376.50 kN) and thehalf-length of the structural plane (X-direction: 10,010/2 mm, Y-direction: 4,550/2 mm). After the overturning
moment significantly exceeded the weight resisting moment, the hysteretic loop showed a steep negative slope
from the peak point. The rotation angle due to rocking exceeded 0.04 rad in the Y-direction. The overturning
moment decreased to less than 20% from the peak due to the brittle wall base fracture.

Fig. 13 Relationship between story shear force and drift angle (B-building in JMA-Kobe 100%)8

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020

M
Wall base level

W
Fixed foundation

Fig. 14 Relationship between overturning moment and rocking rotation angle at wall base level(B-building subjected to JMA-Kobe 100%)

5. Stiffness and Strength Capacity
Figure 15 shows the relationship between the base shear force coefficient and drift angle. The results ofsequential tests are shown together in the same graph. Regarding A-building shown in the upper part of Fig.
15, the maximum strength capacity is correspondent to the base shear force coefficient of 1.8 in the X-direction
and 1.2 in the Y-direction. Regarding B-building shown in the lower part of Fig. 15, the maximum strength
capacity is correspondent to the base shear force coefficient of 1.4 in the X-direction and 1.2 in the Y-direction.
In design practice, the story stiffness is checked at the drift angle of 1/150 rad. Compared to such design values,
the test results reached values about two times higher. The allowable stress design for the Grade 3 index
building adopts the base shear coefficient of 0.3 as the seismic design force. Compared to such allowable stress(1) A-building(2) B-building
Fig. 15 Relationship between the base shear force coefficient and drift angle

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Sendai, Japan - September 13th to 18th 2020

capacities required in design, the ultimate strength capacities reached a value four times higher. Especially in
the X-direction of A-building, the strength capacity had the largest margin by a value six times higher.

6. Conclusions
Two Grade-3 index buildings were designed and constructed base on the current Japanese seismic design
guidelines in order to assess their ultimate states, stiffness and deteriorating behaviors. Two three-story test
buildings represented typical Japanese current constructions seen in densely populated urban areas. One
adopted the Post-and-Beam Structure, and the other the Shear-Wall structure. The sills, column bases and wallbases were anchored to the reinforced concrete foundations by steel anchor bolts, thereby fulfilling theguideline requirements. The foundations were firmly fixed, and shaking table motions were fully applied tothe foundations. JMA-Kobe motion and JR-Takatori motion recorded in the 1995 Kobe earthquake were used
for the sequential tests. The test buildings represented stiffness more than two times higher than the designevaluations. Regarding A-building, the maximum inter story drift angle was limited to less than 0.008 rad inJMA-Kobe 50%, which is equivalent to the Design-Based Earthquake. However, when subjected to JMAKobe 100%, the response deformations were concentrated on the first story, and exceeded the drift angle of0.03 rad. The story deformation was mainly comprised of story shear deformation. In the deformation range
exceeding 0.01 rad, the hysteretic loops depicted peak orienting shape and pinching shape. The ultimate
strength capacities were more than four times the allowable stress design capacity of the Grade-3 index
building. Regarding B-building, severe fractures of wall bases occurred at the interface between the sill andwall panel. During the test of JMA-Kobe 100%, the overturning moment of the upper structure exceeded theweight resisting moment capacity at the wall base. Thus, the wall base was short of steel anchor bolts holding
the column base. The tension forces to the wall and column base are governed by the component models. TheShear-Wall Structure produced much smaller tension forces in the allowable stress design. The maximum
strength capacities reached four times the allowable stress design capacity of the Grade-3 index building. After
exceeding the ultimate fracture state, significant strength deterioration occurred, and the steep negative slope
ended at a point of less than 20% of the maximum strength capacity.

7. Acknowledgements
This work is supported by the Tokyo Metropolitan Resilience Project of the National Research Institute for
Earth Science and Disaster Resilience (NIED). Collaboration on earthquake engineering research using EDefense and NHERI facilities is proceeding continuously. Construction of the test buildings was managed byICHIJO Co., Ltd. Test-relevant affairs were administrated by the Graduate School of Environmental Studies,
Nagoya University and E-Defense, NIED.

8. References[1] T. Nagae, S. Uwadan, C. Yenigodan, S. Yamada, H. Kashiwa, K. Hayashi, T. Takahashi, T. Inoue (2020): The 2019full-scale shake table test program of wood dwellings. 17th World Conference on Earthquake Engineering, 17WCEE,Paper No. C002274.
[2] T. Nagae, S. Uwadan, K. Takaya, C. Yenidogan, S. Yamada, H. Kashiwa, K. Hayashi, T. Takahashi, T. Inoue (2020):
Sliding-rocking combined actions at base foundation influencing global and local deformations of upper woodstructure. 17th World Conference on Earthquake Engineering, 17WCEE, Paper No. C002277.

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