Effect of Vertical Load under Cyclic Lateral Load Test for Evaluating ...

Effect of Vertical Load under Cyclic Lateral Load Test for Evaluating Sugi CLT Wall Panel Minoru OKABE1, Motoi YASUMURA2, Kenji KOBAYASHI3, Takeshi HARAMIISHI4, Yo NAKASHIMA5, Kazuhiko FUJITA6

ABSTRACT: Structural performance of shear walls to resist against wind and seismic loading is evaluated by applying static or cyclic load testing. ISO21581 specifies the static and cyclic lateral load test for shear wall. ISO defines two method of lateral load test. Method 1 shows the boundary conditions are designed to produce mainly the shear response of the wall. Method 2 shows the boundary conditions are designed to produce mainly the rocking (rigid body rotation of the wall) or combined shear-rocking response of the wall reflecting the intended actual construction details of joints connecting the wall to bottom and top boundaries. Cross Laminated Timber panels (also known as CLT or X-LAM) are relatively new building material and high rigidity and strength compared to sheathing materials. It is possible to apply to low-rise residential buildings from the multi-story timber buildings. In Japan manufacturer has been already trying to produce Sugi CLT. Sugi (Cryptomeria japonica）is most popular softwood in Japan. In this report shows effect of vertical load based on ISO21581 method 2 under cyclic lateral load test of Sugi CLT. Vertical load applied three condition, 15kN/m, 30kN/m and without vertical load. Stiffness of CLT wall panel against horizontal load shows higher on vertical load. However maximum strength increase due to vertical load was smaller than the stiffness. KEYWORDS: Vertical load, Cyclic lateral load test, Sugi CLT

1 Introduction123 Structural performance of shear walls to resist against wind and seismic loading is evaluated by applying static or cyclic load testing. ISO21581 specifies the static and cyclic lateral load test for shear wall. ISO defines two method of lateral load test. Method 1 shows the boundary conditions are designed to produce mainly the shear response of the wall. Method 2 shows the boundary conditions are designed to produce mainly the rocking (rigid body rotation of the wall) or combined

shear-rocking response of the wall reflecting the intended actual construction details of joints connecting the wall to bottom and top boundaries. Cross Laminated Timber panels (also known as CLT or X-LAM) are relatively new building material and high rigidity and strength compared to sheathing materials. They have been used to build everything from houses to multi-story apartment buildings. In Japan manufacturer has been already trying to produce Sugi CLT. Sugi (Cryptomeria japonica）is most popular softwood in Japan. In this report shows effect of vertical load based on ISO21581 method 2 under cyclic lateral load test of Sugi CLT.

1

Minoru OKABE, Center for Better Living Tsukuba Building Research and Test Laboratory, 2 Tatehara Tsukuba Ibaraki, Japan & The United Graduate School of Agricultural Science, Gifu University E-mail: [email protected] 2 Motoi YASUMURA, Professor, Faculty of Agriculture Shizuoka University, 836 Ohya Suruga Shizuoka, JAPAN E-mail: [email protected] 3 Kenji KOBAYASHI, Assistant Professor, Faculty of Agriculture Shizuoka University, 836 Ohya Suruga Shizuoka, JAPAN E-mail: [email protected] 4 Takeshi HARAMIISHI, MEIKEN Lamwood Corporation. LTD. 1209 Katsuyama Maniwa Okayama JAPAN E-mail: [email protected] 5 Yo NAKASHIMA, MEIKEN Lamwood Corporation. LTD. 1209 Katsuyama Maniwa Okayama JAPAN E-mail: [email protected] 6 Kazuhiko FUJITA, Hiroshima prefectural Technology Reserch Institute Forestry Research Center,6-1 4 Toukaitihigashi Miyoshi Hiroshima JAPAN E-mail: [email protected]

2 Manufactured Sugi CLT MEIKEN Lamwood Corporation. LTD. has stated the prototype Sugi CLT panel. Sugi lumber used CLT panel was screened by machine grading based on glued laminated timber provided Japanese Agricultural Standard (JAS). Figure 1 shows the distribution of lumber MOE used CLT panel by machine grading. MOE of CLT lumber was used as the MOE of less 8.0kN/mm2 over 3.5kN/mm2. Average MOE of lumber shows 5.6kN/mm2. Dimensions of the CLT wall panel manufactured, 1m wide, 3m long and 90mm thickness. And the test specimen of CLT was prepared three types of cross-sectional configuration. Layer arrangement of prototype CLT was provided 3 layers, 4 layers and 5 layers on 90 mm thickness. Adhesive bonding is used water based polymer- isocyanine adhesive which formaldehyde emission F4star certificated by Japan

0.16

G1-G3 Ave.=5.66 STD.=1.27 AVE.=5.83 STD.=1.50

0.14

necessary to confirm the shear performance using spline material. Horizontal displacement Horizontal displacement Horizontal displacement

H

Vertical displacement

Adhesive Industry Association (JAIA). And this adhesive was generally used on structural glue laminated timber in Japan. Adhesive is used only lamination without edge glue of lumber. Measured average density of Sugi CLT was 439 kg/m3 and coefficient of variation shows 1.2%. And measured average moisture content was 12% used wood moisture tester by dielectric constant. Manufactured prototype Sugi CLT is shown in Photo 1 includes thickness 120mm and 150mm floor panel and 6m length.

0.12

W

W

W

0.10

Figure 2 Comparison of deformation mode of CLT shear wall

0.08 0.06

3.1 Tension Performance of Hold-down Fastener

0.04

3.1.1 Test specimen

0.02 0.00

G1

0

1

2

3

4

G2

5

G3

6

7

8

9

10 11 12 13

MO E(kN/mm 2 )

Figure 1 Distribution of lumber MOE by machine grading

Test specimen of CLT is consisted of 240mm width, 1000mm maximum length and 90mm thickness. 2 types of Hold-down fastener were prepared which allowable tension strength shows 20kN and 25kN. And 2 types of Hold-down fastener which connected CLT and holddown are used ZN90 (diameter 4.11mm length 90mm JIS) nail type and M12 (diameter 12mm JIS) bolt type. Hold-down fasteners tested every type used M16 (diameter 16mm JIS) bolt to connect steel basement. Those hold-downs called Z mark fastener which were certificated for post and beam timber construction by Japan Housing and Wood Technology Center. Test specimen is shown in Figure 3. Caption of Hold-down fastener, N is meaning ZN65 nailed and 20kN used 20 nails and 25kN used 26 nails. B is meaning M12 bolted and 20kN used 4 bolts and 25kN used 5 bolts. HD-N25

HD-B25 650

240

150

200

550

70 100 70

200

70 100 70

150

240

Frequ ency

Rocking mode Bending mode Shear mode

1000

700

240

150

200

500

70 100 70

200

70 100 70

409.4

1000

90

669.2

90

CLT panel has rigid-body for using shear wall. Main criteria deformation mode shows rocking than bending deformation mode and shear deformation mode. Figure 2 shows the comparison of deformation mode of CLT shear wall. In order to predict load-displacement performance of CLT wall, it is necessary to confirm the tension performance of hold-down fastener against uplift load of CLT shear wall. And shear performance between bottom of CLT wall and sill or between top of CLT wall and floor CLT panel is important against horizontal load. If 1m width CLT wall panel placed continuously, 2m width or 3m width shear wall to wall connection is

HD-B20

HD-N20 100

3 Structural Design of CLT Shear Wall

900

240

Photo 1 Prototype Sugi CLT panel which is 90mm, 120mm and 150mm thickness

90

499.2 90

588.2

850

Figure 3 Tension test specimen of Hold-down fastener

3.1.2 Test method Tension test was carried out based on ISO 16670:2003, Timber structures - Joints made with mechanical fasteners - Quasi-static reversed-cyclic test method. Based on monotonic loading test, cyclic loading protocol

Final failure mode of HD-25N, HD-25B and HD-20B is rapture of M16 bolt to connect the steel base. Rapture on M16 bolt was shown at the part of screw． HD-B20 failure mode shows not only rapture of M16 bolt but the embedding of M12 bolt at the CLT. Final failure mode of HD-20N is embedding of ZN90 nail at the Hold-down fastener connected of CLT. Photo 2 shows the general failure mode of HD-N25 and HD-N20. 100

CLT90 HD-N25

100

80

80

60

60

Load(kN)

Load(kN)

was determined. However hold-down fastener worked on tension load did not work on compression load. So reversed cyclic test was carried out on only tension side. Figure 4 shows loading protocol of reverse cyclic test for hold-down fastener on CLT. Ultimate displacement decided 40mm based on monotonic loading test result and loading rate was provided approximately 1mm/sec. Figure 5 shows the hold-down tension test specimen set up the loading apparatus using slider. Number of cyclic loading test specimen is 6. And HD-B20 was tested only monotonic loading.

40

40 20

20 0

CLT90 HD-N20

0

20

40 60 80 Displacemennt(mm)

0

100

0

20

40 60 80 Displacemennt(mm)

100

Figure 6 Comparison of monotonic and cyclic loading of HD-N25 and HD-N20

100

HD-25N

100

HD-25B

80

60

60

Load(kN)

Figure 4 Loading protocol of reverse cyclic test for hold-down fastener on CLT

Load(kN)

M16 bolt Rapture 80

40 20

40 20

Displacement transducer 0

Load Cell100kN 100

0

10

HD-20N

80 Load(kN)

Jack 100kN (Tension side）

100

ZN65 nail CLT Failure

Steel base Displacement transducer Load Cell 100kN

60 40 20

Steel base

Slider

Figure 5 Hold-down test specimen set up the loading apparatus

0

0

20 30 40 50 60 70 80 Displacement(mm)

0

10

20 30 40 50 60 70 80 Displacement(mm)

HD-20B M16 bolt Rapture

80 Load(kN)

Jack 100kN (Tension side）

M16 bolt Rapture

60 40 20

0

10

20 30 40 50 60 70 80 Displacement(mm)

0

0

10

20 30 40 50 60 70 80 Displacement(mm)

Figure 7 Envelop load-displacement curve on 4 types of Hold-down fastener

3.1.3 Test results Figure 6 shows the comparison of monotonic and cyclic loading of HN-N25 and HD-N20 hold-down fastener. Envelop load-displacement curve on 4 types of holddown fastener shows in Figure 7. HD-N25 and HD-B25 hold-down fastener shows approximately 80kN maximum load and rapidly tension load was reduced. HD-20N hold-down shows approximately 60kN maximum load. Beyond the maximum load, tension load was reduced gradually. HD-B20 shows approximately 80kN maximum load and rapidly tension load was reduced. However load-displace curve is different from HD-N25 and HD-B25.

HD-N25

HD-N20

Photo 2 Failure mode of HD-N25 and HD-N20

3.2.1 Test specimen Test specimen of CLT is consisted of 500mm width, 250mm height and 120mm thickness. Sill plate is consisted of 120mm by 120mm section, 980mm long of glue laminated timber and made of Hinoki (Chamaecyparis obtuse) . Average density of sill plate made of Hinoki was measured 482 kg/m3 and average moisture content was measured 15.9%. At the center of the sill plate, CLT is set up. Face and back Layers of CLT are arranged vertical in the longitudinal direction and perpendicular to the sill plate grain. Connected fastener of CLT and sill plate was used wood screw manufactured Rothoblaas HBS D8-L180 in Italy. Connection between CLT wall panel and sill plate was toe screw connection from the CLT wall to sill plate. One test specimen was consisted four wood screws and screw spaced at 100mm. Number of monotonic loading test specimen is 2 and cyclic loading is 6. Test spacemen is shown in Figure 8.

monotonic loading shows embedding screw to the CLT wall and sill plate. Failure mode of cyclic loading shows breakage for bending wood screw. Photo 3 shows the typical failure mode. Jack

150

Disp. transducer 100kN 荷重計 100kN Load cell Jack

CLT t=120mm

CLT t=120mm

5 layer

10 8 6

80 60

120

ﾟ

GlueLam t=120mm 4lamina

GlueLam t=120mm 4lamina 980

4-Wood Screw Rothblass HBS 8-180

Figure 9 Shear test apparatus of bottom of CLT wall and sill plate

5 layer

4-Wood Screw Rothblass HBS 8-180

150

M16 Bolt

Flat roller

Disp. transducer

120

Figure 8 Test specimen of CLT wall and sill plate

3.2.2 Test method Horizontal shear test was carried out based on ISO 16670:2003, Timber structures - Joints made with mechanical fasteners - Quasi-static reversed-cyclic test method. Based on monotonic loading test, cyclic loading protocol was determined. In this test, ultimate displacement was measured 80mm based on monotonic loading test result and loading rate was provided approximately 1mm/sec. load was measured in the load cell attached at the tip of oil jack and relative displacement from sill plate to CLT wall was measured displacement transducer. Measuring load was divided by the number of wood screws. Shear test apparatus of bottom of CLT wall and sill plate is shown in Figure 9 . 3.2.3 Test results Envelop load-displacement curve for horizontal shear force between CLT wall panel and sill plate is shown in Figure 10. Red line shows monotonic loading and blue line shows envelop curve of cyclic loading. And the vertical axis shows the load per screw. Monotonic loading results show high ductility. Initial curve of cyclic loading was consistent with the monotonic loading. However when relative displacement between CLT wall and sill plate shows over 30mm, cyclic loading force were reduced but monotonic loading force were continually. Failure mode of

Load (kN/screw)

120

250

120

st=300mm

150

500 120

st=300mm

250

3.2 Shear performance between bottom of CLT wall and sill

4 2 0 -2 -4 -6 -8 -10 -120

-80

-40

0

40

80

120

Displacement(mm)

Figure 10 Envelop load-displacement curve for horizontal shear load between CLT Wall and sill plate (red line: monotonic loading, blue line: cyclic loading)

Monotonic loading

Cyclic loading

Photo 3 Failure mode of monotonic and cyclic loading test for shear force between CLT wall and sill plate

3.3 Vertical shear performance between CLT wall to wall connection

3.3.3 Test results

3.3.1 Test specimen Shear performance of wall to wall connection used spline is necessary to evaluate consecutive shear wall performance. Test specimen of spline is laminated veneer lumber made of larch provided JAS structural LVL 120E-385F. LVL spline is consisted of 27mm thickness and 149mm width. Wood screw of connected fastener is manufactured by rothoblaas HBS in Italy. CLT is cut off the surface and make single surface spline type and CLT cut off internal and arrange LVL as double shear connection. Test specimen shows Figure 11. Four types of test were carried out 63

63

63

63

D18キリ

100 100

250

149

150

200

348

900

40

Envelop load-displacement curves on four types of spline connection between CLT wall and wall were shown in Figure 13. Red line shows monotonic loading and blue line shows envelop curve of cyclic loading. And the vertical axis of graph shows the load per screw. Comparison of single shear and double shear at CLT thickness 90mm shows upper graph and comparison of CLT thickness 120mm and 150mm connected internal spline shows lower graph. Monotonic loading results show high ductility. Initial curve of cyclic loading was consistent with the monotonic loading. However when relative displacement between CLT wall and LVL spline shows over 20mm, cyclic loading force were reduced but monotonic loading force were continually. Failure mode of monotonic loading shows embedding screw to the CLT wall and LVL spline. Failure mode of cyclic loading shows breakage for bending wood screw and embedding wood screw to the LVL spline shows long hole at LVL spline by cyclic loading. Photo 4 shows typical failure mode of wall to wall LVL spline. CLT 90mm Internal Spline

CLT 90mm Surface spline Rothoblaas Wood Screw HBS

12

12

6

6

90

120

150

LVL t=27 w=179 LVL t=27 w=149

150

LVL t=27 w=149

CLT 120mm 5ply

150

28

120 80

Rothblass HBS-8-100

Rothblass HBS-8-100 80

LVL t=27 w=149

CLT 150mm 5ply

28

28

150 CLT 90mm 3ply

80

Rothblass HBS-8-120

150

150 CLT 90mm 3ply

Loa d(k N/Screw)

90

Loa d(k N/Screw)

198

0

-6

-6

80

0

Rothblass HBS-8-160

Figure 11 Test specimen of CLT wall to wall connection.

-12 -120

-80

-40

0

40

80

120

-12 -120

12

6

6 Loa d(k N/Screw)

Loa d(k N/Screw)

0

40

80

120

80

120

CLT 150mm Internal Spline

12

0

-6

-12 -120

-40

Displacemennt(mm)

CLT 120mml Internal Spline

3.3.2 Test method Shear test was carried out based on ISO 16670:2003, Timber structures - Joints made with mechanical fasteners - Quasi-static reversed-cyclic test method. Based on monotonic loading test, cyclic loading protocol was determined. In this test, ultimate displacement was decided 80mm based on monotonic loading test result and loading rate was provided approximately 1mm/sec. load was measured in the load cell attached at the tip of oil jack and relative displacement from LVL splinel plate to CLT wall was measured displacement transducer. Measuring load was divided by the number of wood screws. Shear test apparatus of bottom of CLT wall and spline is shown in Figure 12.

-80

Disp lacemenn t(mm)

0

-6

-80

-40

0

40

Displacemennt(mm)

80

120

-12 -120

-80

-40

0

40

Displacemennt(mm)

Figure 13 Envelop load-displacement curve of four types of connection between CLT Wall to wall spline (Red line: monotonic loading, Blue line: cyclic loading)

Transducer

Lateral Gaide Roller

Load Cell 50kN

Oil Jack st=300mm

Figure 12 Shear test apparatus of CLT wall to wall spline

Photo 4 Typical failure of wall to wall connection of internal LVL spline on 120mm CLT

3.4 Evaluation on strength of fastener Envelope curve is determined using load-displacement test data of cyclic loading. Yield strength (Py) is obtained by cross point of 10% maximum load (Pmax) to 40% Pmax line and tangent to the envelope curve of 40% Pmax to 90% Pmax line. Stiffness (K) is obtained by the yield strength divided yield displacement (Dy). Ultimate displacement determined envelope curve reduced 80% Pmax after maximum load. Ultimate strength (Pu) is obtained by the area of trapezoid equal to surround area using envelope curve from zero to ultimate displacement. Py, K, Pu are obtained as shown in Figure 14. Yield strength and ultimate strength of hold-down fastener, toe screw of bottom CLT wall to sill plate and wall to wall spline shows Table 1.

Figure 14 Evaluation methods on yield strength and ultimate strength of fastener

3.5 Structural Design of CLT shear wall based on the strength of fastener CLT panel has rigid-body for using shear wall. Main criteria deformation mode shows rocking as shown in Figure 2. And Figure 15 shows the horizontal and vertical load distribution of CLT shear wall. Shear wall test specimen was selected doubled hold-down fastener HD-N20 at the bottom of wall. Hold-down HD-N20 shows 33.7kN yield strength and 3.47mm yield displacement in Table 1. Double arrangement of holddown at the bottom of wall calculated 67.4kN and aspect ratio of wall shows 3, so horizontal yield load calculated 22.5kN/m and horizontal ultimate load calculated 37.2kN. Against horizontal load, bottom of wall and sill plate should be connected rigidly. 10 wood screws per 1m connected and screw spaced 100mm, so horizontal yield strength calculated over 35kN for cyclic loading. Wall to wall connection was selected single surface spline because of easy setup. Wall to wall connection decided 30 wood screws per 3m for each CLT wall connected and screw spaced 100mm. Calculated yield shear strength of 30 wood screws shows 89.4kN. Embedding deformation of sill plate assumed same of uplift deformation of hold-down fastener. Figure 16 shows design load-displacement of shear wall used hold-down fastener’s structural performance. F

2F

Type of fastener

Num ber

3000

Table 1 Yield strength and ultimate strength of holddown fastener, toe screw of bottom CLT wall to sill plate and wall to wall spline Average Py(kN)

Dy(mm)

Pu(kN)

Du(mm)

HD-N20

6

33.75

3.47

55.88

38.03

HD-B20

1

42.23

7.51

69.18

69.71

HD-N25

6

40.65

4.33

66.91

32.64

HD-B25

6

45.67

7.30

67.58

31.02

3.85

4.73

5.83

40.54

-3.53

-3.86

-4.86

-38.72

3.34

2.86

5.15

33.50

-2.62

-2.03

-3.99

-32.33

5.20

1.62

7.50

22.53

-4.58

-1.73

-6.57

-25.37

4.70

1.29

7.23

34.94

-4.21

-1.16

-6.51

-30.21

5.46

1.35

8.34

24.76

-4.71

-1.55

-7.17

-19.05

Wall to sill plate per screw (1)

Wall to wall spline per screw

(2)

(3)

(4)

6

6

6

6

6

1000

2000

Figure 15 Horizontal and vertical load distribution of CLT shear wall

Note: wall to wall spline Symbol (1) shows CLT90mm single surface spline. Symbol (2) shows CLT90mm internal spline. Symbol (3) shows CLT120mm internal spline. Symbol (4) shows CLT150mm internal spline. Figure 16 Design load displacement curve used holddown fastener structural performance

4 Horizontal Loading Test of CLT Shear Wall 4.1 Shear wall test specimen Basic dimension of Sugi CLT wall panel was 1000mm width, 3000mm height and 90mm thickness. Three types of CLT shear wall were setting up and test condition of wall is 1P, 2P and 3P. Bottom sill plate of wall assembly was firmly attached to 105mm square Hinoki (Chamaecyparis obtuse) glue lam and bottom timber secured steel basement of test apparatus. Top plate of wall was attached 300mm width and 90mm thickness Sugi CLT panel. Connection of CLT wall and top and bottom plate was used wood screw HBS 8mm diameter and 180mm length and pitched 100mm. doubled holddown fasteners HD-N20 were arranged at the corner of CLT wall panel. Wall to wall connection is 150mm width and 27mm thickness LVL attached and screwed D8 and L100mm pitched 100mm

Strong beam H500-300-11-18

Slider 12

12

12

Lateral guide Oil Jack 260

Load cell

Actuater Load 300kN st=}250mm

90ﾟ

90ﾟ

90ﾟ

Counter Weight

Stopper

2500 2000

Steel Base

90

90

1500 1000

angle is provided horizontal displacement divide height of test specimen. And the three times cyclic test at the each deformation of 1/450, 1/300, 1/200, 1/150, 1/100, 1/75, 1/50, 1/37.5, 1/30, 1/24, 1/20, 1/17, and 1/15.

Wood Screw HBS D8 L180 spaced 100mm


Figure 18: Test Apparatus of 3P CLT wall panel Strong Beam H500-300-11-18

CLT wall Panel

CLT wall Panel

3000

3000

CLT wall Panel

Slider 2 1

2-Hold-down fastener HD-N20 M16 bolt

2-Hold-down fastener HD-N20 LVL Spline M16 bolt Wood Screw HBS D8 L100 spaced 100mm

Lateral guide

Oil Jack

105

105

Ball Bearing Load Cell

90

3500 3000

Figure 19: Vertical loading system

4.3 Test Results CLT wall Panel

CLT wall Panel

3000

CLT wall Panel

2-Hold-down fastener HD-N20 M16 bolt LVL Spline Wood Screw HBS D8 L100 spaced 100mm

105

20-ZN90


Figure 17: Test specimen of CLT shear wall

Load-Displacement curve of 1P CLT wall applied vertical load shows in Figure 20. Load-Displacement curve shows over 30kN strength and high ductility. Bilinear line of shear wall based on hold-down strength and deformation shows circle line. Ductility shows similarity to the test results; however stiffness of wall shows higher than the test results. Failure mode was nail yield (CN90) of hold down fastener connected Sugi CLT wall. CLT Wall 1P 50

4.2 Shear wall test method

40 30 20 Load (kN)

Test apparatus of 3P CLT wall panel is shown in Figure 18. Appling lateral load on test shear wall was used actuator loading jack and vertical load on test shear wall was used oil jack with feedback controlled using load cell arranged on the top of shear wall. Position of vertical load to test specimen is the center of CLT wall panel. Vertical loading system of shear wall was shown in Figure 19 . Cyclic test procedure of shear wall under 1/50 radian was according to the building minister certification method on Performance Evaluation Organization in Japan. After 1/50 radian cyclic procedure was simulated to ISO method of three time’s cyclic test. Deformation

10 0 -10 -20 -30 -40

V Load: 0kN V Load: 15kN/m V Load: 30kN/m

-50 -250 -200 -150 -100 -50 0 50 100 150 200 250 Displacemennt(mm)

Figure 20: Load-Displacement curve of 1P CLT wall

Load-Displacement curve of 2P CLT wall applied vertical load is shown in Figure 21. And 3P CLT wall is shown in Figure 22. Ductility of test results is reduced than the calculation value. Because before hold-down fastener failed, LVL spline of wall to wall connection is failed splitting.

35

CLT Wall 2P

30

80 60 40 20

25 20 15 10

0

Py 0.2Pu√(2μ-1) 2/3Pmax P1/120

5

-20

-80


1P

2P

30kN/m

15kN/m

0kN/m

30kN/m

15kN/m

0kN/m

30kN/m

V Load: 0kN V Load: 15kN/m V Load: 30kN/m

-60

15kN/m

0

-40

0kN/m

Load (kN)

40

Strength(kN/m)

100

However in 2P shear wall and 3P shear wall, strength of 0.2 Pu multiplied by square root of (2u-1) shows lower value than the strength of yield Py. Because before holddown fastener failed, LVL spline of wall to wall connection is failed splitting as shown in Photo 5.

3P

Figure 23: Comparison of each strength and effect of vertical load

Figure 21: Load-Displacement curve of 2P CLT wall 160

CLT Wall 3P

120

Load (kN)

80 40 0 -40 -80 -120

V Lo ad: 0kN V Lo ad: 15kN/m V Lo ad: 30kN/m


Figure 22: Load-Displacement curve of 3P CLT wall

Envelope curve is determined using load-displacement data of shear wall. Yield strength (Py), maximum load (Pmax), stiffness (K), yield displacement (Dy), ultimate strength (Pu) and ultimate displacement (Du) shows in Figure 14. Allowable strength of shear wall of post and beam timber structure in Japan is usually determined using four criteria; First one is yield strength Py, second is 20 % ultimate strength 0.2 Pu multiplied by square root of (2u-1) that u means yield ratio calculated Du divided Dy multiplied by Pu/Py, third is 2/3 maximum strength Pmax and fourth is 1/120 radian deformation strength P1/120. Figure 23 shows the comparison of strength on four criteria due to applying the vertical load. Y axis shows the strength per meter meaning divided test wall length. Strength of the four criteria determined on the allowable strength was increased by applying vertical load. Strength of 0.2 Pu multiplied by square root of (2u-1) shows the ductility shear performance. In 1P shear wall, strength of yield Py and Strength of 0.2 Pu multiplied by square root of (2u-1) shows almost the same value.

Photo 5: Failure mode of 3P CLT shear wall applying 30kN/m vertical load.

5 Conclusion On the basis of the experimental data obtained from cyclic loading test of shear walls and strength and stiffness of hold-down fastener, wood screw and spline connection, following could be concluded. 1. Regardless of the length of the wall, strength of the four criteria determined on the allowable strength was increased by applying vertical load in Sugi CLT shear wall. 2. Main deformation mode of Sugi CLT shear wall was shown rocking mode. Strength and deformation at the bottom corner of CLT shear wall was determined the strength and deformation of shear wall. 3. 2P and 3P CLT shear walls were shown in the splitting failure of wall to wall connected by LVL spline.

Acknowlegement This study was conducted based on subsidy by the Ministry of Land, Infrastructure and Transport that MEIKEN Lamwood Corporation has been adopted.