THE DESIGN AND INSTALLATION OF
A FIVE-STORY NEW TIMBER BUILDING IN JAPANKOSHIHARA Mikio, Assoc. Prof., Dr.Eng.
Institute of Industrial Science, University of Tokyo, Japan, kos@iis.u-tokyo.ac.jp
ISODA Hiroshi, Assoc. Prof., Dr.Eng.
Faculty of Engineering, Shinshu University, Japan, hisoda@gipwc.shinshu-u.ac.jp
YUSA Shuitsu, Dr.Eng
Tsukuba Building Test Laboratory of Center for Better Living, Japan, yusa@tbtl.org
SUMMARY
Buildings in Japan have been constructed using timber since olden times. At the same time,
Japan is a country beset by earthquake and timber buildings were weak against fire. So, from 1950
to 1987 wooden buildings over 13m height were prohibited by law. Revision of the BuildingStandards Law 2000 allowed the construction of buildings four-story or taller with fire-resistance
performance. M-Bldg. built in 2005 is the first five-storied timber building after established
Building Standard Law in Japan. This paper describes the structural framing and fire resistancesystem for this building and details. M-Bldg. was built in Kanazawa city, Ishikawa prefecture. In
this building, first-story was built in reinforced concrete construction and from 2-5 stories was built
in timber-based hybrid construction. In structural framing, the performance-based design method(“Calculation of Response and Limit Strength”) was applied and some static structural experiments
were conducted about the seismic performance of shearing wall and the buckling stress oftimber-based hybrid column. In fire resistance system, fireproof construction was needed for thisbuilding. Three fireproof elements, column, girder and bracing, were tested for 1 hour fire resistive
period. All elements could have enough properties for 1 hour fire resistance. The possibilities of
middle-rise and high-rise timber buildings are extended by completion of this building.

1. INTRODUCTION
Buildings in Japan have been constructed using timber since olden times. Traditionaltimber temples and shrines, such as the Horyu-ji Temple, look the same as they did whenconstructed more than 1400 years ago. Many large-scale timber buildings were constructed duringthat time, and include the Hall of the Great Buddha in Todai-ji Temple (height: 46.8 m, area: 2878m2) and the five-story Pagoda in Toji Temple (height: 54.8 m). Even after the Meiji Era, four andfive-story timber buildings were used as factories, warehouses, and inns, until the construction oflarge-scale timber buildings was restricted by the Urban Building Law of 1919, and the BuildingStandards Law of 1950 further restricted the construction of large-scale timber buildings. In 1959,
the Architectural Institute of Japan carried a resolution against timber construction to prevent fire,storm, and flood damage, making it impossible to construct large-scale timber buildings. Timberbuilding height restrictions were loosened in 1987, allowing the construction of three-story
structures and buildings taller than 13 m. Eaves having a height of more 9 m were also permittedusing large sections of laminated timber. Revision of the Building Standards Law in 2000 allowed
the construction of buildings four stories or taller with fire-resistance performance. The present
study reports the structural and fire resistance characteristics of the first timber-based hybrid
structure in Japan, the five-story Kanazawa M building (Kanazawa M Bldg.), constructed in 2004.

2. OUTLINE OF THE BUILDINGThe five-story Kanazawa M Bldg. (height: 14.237 m, area: 6.195
m x 12.100 m) was constructed in Kanazawa City, Ishikawa
Prefecture.(Photo.1) The first story has a Reinforced Concrete structure
and the second to fifth stories have a timber-based hybrid structure withbuilt-in steel materials. Building data are listed in Table 1, and the floor
plan and elevation are shown in Fig. 1 and Fig. 2.
Table 1 Building data
Architect-architect office- Strayt Sheep

Structural Design

Kirino Structural Engineering OfficeArea374m2(total floor) / 74.96m2(building)Use

SchoolHeight14.237m

Structure

RC construction(first story)
Timber-based hybrid construction(2-5 storied)

Photo.1 External viewof Kanazawa M Bldg.

Fig. 1 Floor plan

Fig.2 Elevation

Members
The building mainly uses the structural members listed below to satisfy the requirements for verticalload performance, seismic performance, and fire resistance. This building is required fire resistive
construction, and structural elements are required 1 hour fire resistive period.
(1) Column, beam, and brace
The building uses laminated timber with built-in steel materials for columns, beams, and braces tosatisfy the structural and fire resistance requirements of a five-story building. The cross section ofeach member is shown in Fig. 3.
The column is square laminated timber (larch E105-F300, 200 x 200 mm) with built-in square steel
bars (SS400, 65 x 65 mm). The beam is laminated timber (200 x 330 mm) with steel plates (SS400,
PL-22x300). The cross section of a brace looks identical to that of a column, which is necessary forfire resistance certification.
(2) Floor and roof
The floors and roofs are made of reinforced concrete slabs joined together with lag screws and steel
plates built into the beams.
(3) WallThe longitudinal walls are load-bearing and made of nailed plywood. The lateral walls arenon-load-bearing, because of setting braces.
(4) Stairs
The stairs are made of steel frames.

columnbeam
brace
Fig.3 Cross sections of column, beam, and brace

3. STRUCTURAL PLANNING
Similar to ordinary timber buildings, a five-story timber-based hybrid structure requires
verification of its safety against self weight, live load, vertical load by snow coverage, andhorizontal load under a horizontal force, such as an earthquake or wind. Fire resistive buildings arealso required to maintain building integrity in the event of a fire. Based on these structural
performance requirements, the following structural verification was conducted on the Kanazawa M
Bldg.
Vertical Load
The timber and steel frame function together as a structural member in the second to fifth stories ofa timber-based hybrid structure. To clarify the function of the timber and the steel frame about eachmember, the joint was designed as follows:(1) Beam
Since the vertical deformation is equal between the timber and the steel frame, vertical load should
be shared depending on their ratio of flexural rigidity, EI (E: Young's modulus, I: Geometricmoment of inertia). The flexural rigidity ratio EI / ∑EI is shown in Table 2.
The timber and steel frame of the beam are joined at a beam edge using drift pins to transmit theload from the timber to the steel frame, so the steel frame bears all the shear force at the edge. The
gusset plate from the steel frame of the column and the steel frame of the beam are joined with high

Timber frame
Steel frame

Table 2 Flexural rigidity ratio of timber and steel frame
E
I
EI
2
4
(N/mm )
(mm )(Nmm2)
1.05x104
5.55x1080.583x1013
57
2.05x104.95x101.01x1013

EI/∑EI
0.366
0.634

tension bolts for the column-beam connection. The holes in the side of the timber frame are filledwith timber after high tension bolts are clamped. (Fig. 4).
Snow load stress on both the timber and steel frame of the beam are designed not to exceed theshort-term allowable limit, even in the very rare case of a snow load with a vertical depth of 1.2 m(multiplied by 1.4).
(2) Column
Vertical load is transmitted to the steel frame of a column through a gusset plate, and verticalloading of the timber is avoided using a 3 mm clearance, which is essential for combining thetimber with the steel frame. The timber of the column functions as a buckling restraint for the steel
frame, and, as the structural experimentation in Chapter 4 shows, alone, the steel frame of thecolumn buckles at about 20% of the yield stress. However, the timber-based hybrid column did notbuckle when the steel frame yielded to axial force compression because the timber functioned as abuckling restraint.

Fig.4 Joint (Lateral)Fig.5 Joint (longitude)

Horizontal Load
The structural planning of the building is different from each direction. A timber-based hybrid beam
is suspended laterally and supported by columns of identical material, and the longitudinal beam isbuilt in a reinforced concrete slab. Damage limit seismic force produces greater horizontal force
than the load exerted by very rare wind, as prescribed in the Building Standards Law, so horizontal

resisting elements are braces the lateral roof face and the longitudinal plywood (load-bearing) walls.
(1) Beam
A lateral timber-based hybrid beam bears axial force and produces a reaction force of braces during
an earthquake. The steel frame bears axial force, the timber frame functions as a buckling restraint,
and calculations confirmed the absence of buckling within the safety limits of applied axial force.
(2) Column
During a lateral earthquake, a timber-based hybrid column produces a reaction force of braces. This
column does not buckle when the steel frame yielded to axial force compression as mentioned
above.
During a longitudinal earthquake, vertical shear force is transmitted from the plywood bearing wall
to the timber of the column through the vertical frame (Fig. 5). The timber has a bearing plate of thesteel frame (PL-19) at both ends of the timber of the column, and when the timber collides against
the bearing plates, axial force is transmitted to the steel frame of the column. Therefore, during anearthquake, the timber functions as a buckling restraint.
(3) Brace
A brace bears axial force during a lateral earthquake. Only one steel frame (PL-22x65), at the center,
contributes to the structure as the steel frames. Buckling of the brace was not observed undersignificant plastic deformation of the steel frame by compression axial force.
(4) Plywood bearing wall
A plywood bearing wall bears horizontal force during a longitudinal earthquake, and consists ofstructural plywood (thickness: 24 mm), screws (diameter: 8 mm) and both vertical and horizontal
frames of laminated timber arranged around the plywood (Fig. 5). Vertical shear force of theplywood bearing wall is as mentioned in Section (2), and horizontal shear force is transmitted fromthe structural plywood to both the horizontal frame and the downstairs plywood bearing wall
through anchor bolts (M16) embedded in the reinforced concrete slab.
After Fire
(1) Beam
Only the steel frame bears vertical load on the assumption that the timber had burnt completely.
Although timber actually stops burning, the remaining timber cannot be used as a structural member
under present law. The vertical load is assumed to be the same as before a fire, and for safety
reasons, the steel frame stress should not exceed the long-term allowable limit.
(2) Column
The column also bears vertical load only using the steel frame and the stress applied should notexceed the long-term allowable limit for buckling.

(3) Brace
The timber of a brace is also assumed to have completely burned. The wind pressure, at the
maximum momentary wind velocity of 15 m/s, is set as the constant wind load, and both bracetension and beam bending resist the lateral horizontal force. In this case, the steel frame stress isprevented from exceeding the short-term allowable limit.
(4) Plywood bearing wall
A plywood bearing wall is assumed to have completely burned.
(5) Longitudinal RC beam
An RC slab has a built-in longitudinal RC beam, as shown in Fig. 5. The rigid frame structure,
consisting of the RC beam and the steel frame of the column, resists the longitudinal horizontal
force produced by the constant wind.
4. STRUCTURAL EXPERIMENTATION
According to structural planning in Chapter 3, we clarified the structural performance ofeach member through experimentation. More specifically, we conducted a buckling performance
test on a timber-based hybrid column and a shear performance test on a load-bearing wall.
Methods and Results of Experimentation(1) Column
According to the structural design policy described in Chapter 3, the columns support vertical load
only using the steel frames, but the surrounding timber supports axial force to resist buckling during
an earthquake. Therefore, the timber requires a flexural rigidity (EI) that prevents buckling up to theyield load (Py) of steel.
We conducted a full-size buckling test to verify the buckling restraint of the timber a specimen of
the full length (L = 2800 mm) was monotonously pressurized on both ends as shown in Photo 2,
and the load-deformation relationship is shown in Fig. 6. Rigidity decreased at an axial deformationof 5 to 10 mm, resulting in strain hardening, because the partial loss of area at the end of the steel
for jig yielded. Under a load of 1000 kN, the steel also yielded and suffered from a plastic
deformation of approximately 30 mm. The yield axial force calculated from the result of a material
test on a square steel bar (yield stress = 284 N/mm2) is 912 kN. The square steel bar contracted andthe timber of the column made contact with the jig, producing axial force, as axial deformation
reached 30 to 40 mm. The timber cracked and buckled from a further increase in the load. The
buckling strength (Nk) of the laminated timber is greater than the 672 kN calculated from thestandard compressive strength. Results indicate that the timber-based hybrid column did not tobuckle until the short-term allowable axial force (908 kN) of the square steel bar was reached.

2000

C2
C3

Load (kN)

1500
1000
500
0
0

Photo 2 Full view of experimentation

10

20

30
40
deformation (mm)5060

Fig.6 Column load-deformation relationship(2) Wall
As a load-bearing wall, plywood (thickness: 24 mm) is secured on each side of a framework withscrews (dia.: 8 mm) at intervals of 150 to 250 mm. The shear rigidity and shear strength of thescrews securing the plywood were calculated experimentally, and are shown in Table 3.
Table 3
Shear rigidity: K1(N/mm)

Shear strength
(N)

1300

7126

Performance per screw

An analytical model of the Plywood bearing wall and frame is shown in Fig. 7, and the detail ofmodel is as follows:
1. The frame consists of square steel bar columns and RC
beams, and the ends of the members form plastic hinges
when yielded.
2. The load-bearing wall consists of plywood, timber column,
sill, and both screws and bolts for joining the members.
3. The connectors between the plywood and the frame aremodeled as a spring as screws (rigidity: K1, Table 3).
4. The spring formed between the column timber and thesquare steel bar transmits shear force, received from screws
colliding against the bearing plate, from the timber to theFig.7 Plywood bearing wall
steel bar. To ensure elasticity, even during deformations
modelwithin safety limits, K2 is set at 11.5 N/mm. This also takes into consideration the axial
rigidity of the column timber and the rigidity due to the clearance between the column timber
and the bearing plate.
5. The spring formed between the sill and the RC beam transmits shear force, received from thescrews through anchor bolts, from the sill to the RC beam. To ensure elasticity, even during
deformations within safety limits, K3 is set as 81.6 N/mm. this also takes into consideration
the transmission of shear force between the bolt and the sill and the rigidity due to theclearance between the bolt and the sill.
If the rigidity K1 of the plywood bearing wall is linked in series with the rigidity K2 by the column
timber or the rigidity K3 by the sill, and K2 and K3 are linked in parallel, the equivalent rigidity canbe calculated as follows:
K = 1/ {1/K1+1/ (K2+K3)}
Using this equation, the yield strength and ultimate strength can be calculated as "analytical values"(Table 4).
Table 4 Performance of plywood bearing wall
Analytical values

Experimental values

Rigidity (kN/mm)

2.85

2.56

Yield strength (kN)

97.5

92.3

Ultimate strength (kN)

178

182

We conducted a full-size static loading test to verify the performance of the plywood bearing wall.
The specimen had a column span of 1710 mm and a height of 2740 mm as shown in Fig. 8. Reverse
cycling loading was used for the static loading test, and the cyclic loading profile was controlled byapparent shear deformation angle. Loading of the same deformation profile was repeated threetimes, using a loading profile of ±1/600 - ±1/450 - ±1/300 - ±1/200 - ±1/100 - ±1/75 - ±1/50 - ±1/25- ±1/15 rad. The load-deformation relationship of the plywood bearing wall is shown in Fig. 9.
When the maximum strength (Pmax) is 235 kN, the drift is 161.5 mm (1/17 rad.). A crack developed
and grew along the RC part of the joint between the square steel bar column and the RC beam;
resulting in the destruction of the screws by shear force and the collapse of the plywood.
Performance of plywood bearing wall was investigated experimentally, and results are shown in
Table 4. The experimental values are slightly greater than the analytical values.

300

Load (kN)

200
100
0
-200

-100

0
-100
-200

100

200

300
400
deformation (mm)Experiment
Analytical-300

Fig. 8 Specimen of
plywood bearing wallFig.9 Wall load-deformation relationship

5. CALCURATION OF RESPONSE AND LIMIT STRENGTH
We created an analytical model of the building based on the experimental results, andverified the safety against seismic force by predicting response deformation using theperformance-based design method (“Calculation of Response and Limit Strength”).
Verification by Safe Limit Strength Calculation(1) Safe limit drift angle
A safe limit drift angle of 1/50 was set for both the lateral and longitudinal directions. Since thestrength of longitudinal plywood bearing wall rose to a drift angle of approximately 1/20, 1/50, as asafety margin, is more than adequate. This margin was set in accordance with the deformation
tracking performance of a sash window used for an outside wall of an ordinary building.
(2) Calculation of response
The experimental and analytical safety limit strength exceeded the required safety limit strength,
and the true response value is calculated as follows:a) Creating a relation diagram of the load-deformation curve (Sa-Sd) at the representative material
point of the buildingb) Calculating the acceleration (San) of input into the building at equivalent cycles by consideringbuilding attenuation at each stepc) Plotting San on a straight line connecting Sa-Sd (load deformation of the building) andtheorigin at the stepd) The true response value is the intersection of the San curve at each step (demand curve)
andthe Sa-Sd curve of the building.

lateral direction
longitudinal direction
Fig.10 Prediction of responses at the time of an earthquake
Results of the calculation are shown in Fig.10. The safety against seismic force both direction wasverified. In the lateral direction, strength hardly increases after the yielding of horizontal resistingelements. In the longitudinal direction, the plywood bearing wall is in an elastic area, up to 1/50 of
the safe limit drift angle.
5. CONCLUSION
Besides verifying the safety against seismic force, to satisfy the fire resistance performancerequired for fireproof buildings, we verified fire resistance using a beam-loaded heating test, a
column-loaded heating test, and a joint heating test. Based on the results of structure and fire
resistance research, Japan's first building using a timber-based hybrid structure, having 1- hour fire
resistance, was completed in Ishikawa Prefecture in 2005,
REFERENCES
M.KOSHIHARA, H.ISODA, et al.: A Study of five storied timber based hybrid building forpractical use (Part 1-3), Summary of Technical Papers of Annual Meeting Architectural Institute ofJapan, C-1, pp.201-206, 2005
S. YUSA, T.YOSHIKAWA, et.al: Research in practice on 5-story fire resistance hybrid wooden
structure building, Summaries of Technical Papers of Annual Meeting Japan Society for Finishings
Technology, pp.7, 2005