Performance of Base Isolated Structure for Tsunami Loading

Mineo TakayamaFukuoka University

Topics

• Performance of Seismically Isolated Buildings based on Earthquake Records

• Guideline for Structural Design of Tsunami Evacuation Buildings

• Response of Seismically Isolated building due to Tsunami Wave Force

2005 Fukuoka

1995 Kobe

2004 NiigataFukushima NPP

Tokyo

2011 Tohoku

2000 Tottori

2008 Iwate-Miyagi

2007 Niigata Chuetsu

2003 Tokachi-oki

Major earthquakes in the last 20 years

20??

Seismically Isolated Building at Fukushima Dai-ichi & Dai-ni NPP

0

1

2

3

0 200 400 600 800

Fukushima Dai-ichi

NS-dir.EW-dir.

Stor

y

Max. Acceleration (gal)

0

1

2

3

0 200 400 600 800

Fukushima Dai-ni

NS-dir.EW-dir.

Stor

y

Max. Acceleration (gal)

1/4

1/2

0.0

0.5

1.0

1.5

2.0

2.5

0 200 400 600 800

1995 Kobe2004 Niigata2005 Fukuoka2011 Tohoku (1FL/BASE)2011 Tohoku (ROOF/BASE)

Am

plif

icat

ion

of A

ccel

erat

ion

Max. Acceleration at BASE (gal)

Amplification Factor of Acceleration of Seismically Isolated Buildings

Good performance

Total Damage$2.2 Trillion

Total Damage$2.2 Trillion

Number of Death

320,000

Number of Death

320,000

Height of Tsunami WaveFrom 15m to 34m

Damage Estimation of Nankai Trough EarthquakeDamage Estimation of Nankai Trough Earthquake

gah

h

ah

Inundation Depth

Tsunami Wave Pressure

Building

Hydrostatic Force Distribution due to Tsunami Wave

z

Water Depth Coefficient

Japanese Guidelines for Tsunami Evacuation Building

zahgqZ

Zq

: Tsunami pressure: The mass of unit volume of water (1.0 t/m3) : Gravitational acceleration (9.8 m/s2): Design Inundation depth (m): The height of the part of interest from the

ground level, (m): Water depth coefficient

ahz 0

ghz

Tsunami Pressure

a

Water Depth Coefficient “a”

2

1

Z

ZZ dzBzahgQ

Qz: Tsunami force in direction of travel for structural design (kN)

B: Width of pressure-receiving surface of relevant part (m)

Z1: Minimum height of pressure-receiving surface (0≤Z1≤Z2) (m)

Z2: Maximum height of pressure-receiving surface (Z1≤Z2≤ah) (m)

Tsunami Force

gah

H

DB

Isolation Layer

Superstructure

Base

H

D

hah

Inundation Depth

Isolation Layer

Tsunami Loading

Seismically Isolated Building Modelfor Tsunami Response

No. of stories N

HeightH (m)

Depth D (m)

H/D =1 H/D =3 H/D =5

5 15 15 5 310 30 30 10 615 45 45 15 920 60 60 20 1230 90 90 30 18

Building Model Dimensions

DBNwW 1Total Weight of Building Models

(w=12 kN/m2)

Hysteresis Characteristics ofIsolation Layer

SQfK

tQ

t

Shear Force

Shear Deformation0

gKWT

ff 2

WQS

S

Stf

t

gTWQ

2

24

Yield Shear Coefficient

Isolation Period

gah

H

D

hah

Inundation Depth

Tsunami Load Acting on Isolation Layer

gBahQt 2

21

tQ

These influences were not included:Openings such as windowsBuoyancyFloating debris

DNw

gahWQt

t 12

2

0

10

20

30

40

50

0 0.2 0.4 0.6 0.8 1Hei

ght o

f Tsu

nam

i Pre

ssur

e a

h (m

)

Base Shear Coefficient t

H=90m H=60mH=45m

H=30m

H=15m

H/D=10

10

20

30

40

50

0 0.2 0.4 0.6 0.8 1Base Shear Coefficient t

H=90m

H=60m

H=45m

H=30m

H=15m

H/D=3

0

10

20

30

40

50

0 0.2 0.4 0.6 0.8 1

H=90m

H=60m

H=45m

H=30m

H=15m

H/D=5

Base Shear Coefficient t

Height of Tsunami Pressure “ah”vs. Base Shear Coefficient

H/D=1 H/D=3 H/D=5

t

ah

Stf

t

gT

2

2

4

Prediction of Max. Deformation

0

10

20

30

40

0 0.2 0.4 0.6 0.8 1

H/D=3, s=0.03

Hei

ght o

f Tsu

nam

i Pre

ssur

e a

h (m

)

Max. Deformation (m)

Solid Line:Tf=3sDashed Line:Tf=5s

H=90m

H=60m

H=45m

H=30m

H=15m

H/D=3

03.0Ssec5or sec3fT

ah

t

0

0.1

0.2

0.3

0.4

0.5

0 0.2 0.4 0.6 0.8 1

H/D=3N

orm

aliz

ed T

suna

mi H

eigh

t ah

/H

Max. Deformation (m)

Tf=3s

Tf=5s

s=0.03

Normalized Height of Tsunami Pressurevs. Max. Deformation

H=15m--90mHah

t

Tf a H/D =1 H/D =3 H/D =5

3sec3 0.14H 0.08H 0.06H

1.5 0.28H 0.16H 0.13H

5sec3 0.10H 0.05H 0.04H

1.5 0.20H 0.10H 0.08H

Tsunami Inundation Depth when Max. Deformation of Isolation Layer

Reaches 40 cmS = 0.03

2km

Isolated Warehousehit by the Tsunami, 2011 Tohoku Eq.

Sendai-Shiogama PortMiyagi Prefecture

200m

Structural System of Warehouse

Superstructure :Steel structure

Isolation System :24 HDRs

Diameter：800mm or 850mm

Isolation Period :

Yield Shear Coefficient:sec2.4fT

50m30

m

30m

03.0S

Floor Plan

Section

W=93240kN

Inundation Depth : 4m

4m

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8 1

B=30mB=50mB=58.3m

Inum

datio

n D

epth

h (m

)

Max. Deformation (m)

a=2.0

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8 1

B=30mB=50mB=58.3m

Inum

datio

n D

epth

h (m

)

Max. Deformation (m)

a=1.5

Calculation of Max. Deformation

Observed Max. Deformation : 21 cm

30m

50m

Direction of TsunamiTsunami Height : 4 m

a=1.5 a=2.0

0.2a5.1am500

ShelterOcean

The Moving Directionof Tsunami

m200 m2000 Can the hydrostatic tsunami pressure become

applicable to seismically isolated buildings?Can the hydrostatic tsunami pressure become applicable to seismically isolated buildings?

Selection of Water Depth Coefficient

Further research into matters such as the validity of the method used to set the tsunami load and the influence of buoyancy is required to confirm the tsunami safety of seismically isolated buildings.

Further research into matters such as the validity of the method used to set the tsunami load and the influence of buoyancy is required to confirm the tsunami safety of seismically isolated buildings.

It was confirmed that most seismically isolated buildings demonstrated an adequate seismic isolation effect in response to the earthquake.

In this research, we applied the same tsunami loads as those used in the design of tsunami evacuation buildings. As tsunami inundation depth increases, large shear forces and deformation occur in the isolation layer.

The smaller the size of the building (height and depth) and the more flexible the isolation layer, the greater the deformation of the isolation layer.

Conclusions

“Disaster will attack when you have forgotten”

Thank you for your attention