Basic Concept of Base Isolation System for Buildings

8/12/2019 Basic Concept of Base Isolation System for Buildings

1/23

1

Basic Concept of Base Isolation

System for Buildings

Dr. Taiki SAITO

Japan Society of Seismic Isolation

Chief Research Engineer,

Building Research Institute, Japan

Email: [email protected]

Contents

Introduction

Basic Idea of BI system

Design procedure of BI building

Response spectrum method

Time history analysis

Ultimate capacity of isolators

International activity of JSSI


2/23

2

Basic Idea of BI system

Isolation from ground

By balloon? By Magnetic force?

Introduction

Seismic isolation

Rolling? Sliding?Stopper Friction


3/23

3

Introduction

Example of sliding system

Kamakura statue was rehabilitated in 1960 adopting sliding foundation.

Introduction

Restoring position?

Sliding?


4/23

4

Introduction

Restoring system

By spring? By sliding on a

curved plate?

IntroductionGravity Force and Inertia Force

Resisting Force

k

mT 2=

g

LT 2=

(m: mass, k: stiffness)

Effective for heavy building(L: curvature, g: gravity acceleration)

Effective for light building


5/23

5

Introduction

d0

time

T

d0

With Damper

Damping system

Damper

Introduction

Requirement of BI devices

1. Isolating the building from the ground

2. Supporting the weight of building

3. Damping of response amplitude

4. Restoring the original position after an earthquake


6/23

6

Introduction

Isolators

Rubber bearingLarge axial deformation

Weight ofbuilding

Rocking

Rubber lock

Stiff

Rubber

Earthquake

Load

Soft

Steel

Laminated Rubber

Weight of

building

-500

-400

-300

-200

-100

0

100

200

300

400

500

-300 -200 -100 0 100 200 300

Displacement (mm)

Force(kN)

High damping rubber

Reinforcing steel plate

Cover rubber

Flange plate

High damping rubber

Reinforcing steel plate

Cover rubber

Flange plate

-2

-1

0

1

2

-3 -2 -1 0 1 2 3

Shear

stress(N/mm

2)

-800

-600

-400

-200

0

200

400

600

800

-300 -200 -100 0 100 200 300

Displacement (mm)

Force(kN)

Natural Rubber Bearing

(NRB)High-damping Rubber

Bearing (HRB)

Lead Rubber Bearing

(LRB)


7/23

7

Introduction

Isolators

Sliding bearing or Roller bearing

Linear Rail

Linear BlockRubber Shim

Flange Plate

Sliding bearing

Curved plane

sliding bearing

-50

-40

-30

-20

-10

0

10

20

3040

50

-150 -100 -50 0 50 100 150

Displacement (mm)

Force(kN)

-200

-150

-100

-50

0

50

100

150

200

-4 00 - 30 0 -2 00 - 100 0 1 00 2 00 30 0 4 00

Displacement (mm)

Force(kN)

Rail roller bearing

Introduction

Dampers

Cast Lead

Steel Flange Plate

Steel Damper Rod

Steel Flange Plate

Stud

F =1150(kNs/m) V0.38

- 20 - 15 - 10 -5 0 5 10 15 20( cm)

(kN)

800

600

400

200

0

-200

-400

-600

-800

Lead damper

Viscous damper

Steel damper


8/23

8

Introduction

Response of BI building

STERA 3D

Introduction

Response of BI system

Y"

X

Upper structure

(rigid mass)

Base Isolation level

(spring)


9/23

9

Introduction

Response of BI system

Y"

X

- m(X"+Y" )

Q=keX

c X'

Vibration model Equilibrium of forces

M X + CX + Ke X = - MY

Numerical integration

X + 2h X + 2 X = - Y

= (2 /T) = (Ke/M)

T: natural period

h : damping factorY X

X

X

Equation of motion

Introduction

Effect of natural period Y: JMA-Kobe NS componenth = 0.05

T longer

Displacement larger

T longer

Accelerationsmaller

X

X


10/23

10

Introduction

Response spectrum

Time history of accelerationResponse spectrum of acceleration for

JMA Kobe-NS wave, h=0.05

Response of

SDOF system

with naturalperiod of T &

viscous damping

ofh

X

Y

T longer

Accelerationsmaller

Introduction

Effect of damping JMA Kobe-NS wave

Acceleration response spectrum Displacement response spectrum


11/23

11

Introduction

Reduction of applied

lateral forces to super

structure

Increase of displacement

response of isolated story

Contents

Introduction

Idea of BI system







12/23

12


Statistics Number of buildings

Private house

Apartment building

1995 The Great Hanshin-

Awaji Earthquake Disaster

2000 Revision of

Building Standard Law


Building Standard Law, Japan

Height>60m

NO

YES

Reviewed by local government official Reviewed by

special committee

Response Spectrum Method Time History Analysis

Need for Structural Calculation?

YES

NO

Specification code

1 or 2 story wooden house1 story S or RC building


13/23


14/23

14


Response Spectrum Method

Upper structure

(elastic range)

Base Isolation level

(inelastic range)

Force

Drift

Force

Drift

Ke

he

Ke: equivalent stiffness

he : equivalent damping

Responses are obtained by equivalent linearization.

Nonlinear system Equivalent linear system

he

he

h=0.05

h=0.05

Te

Te

Acceleration response

Displacement response

cm/s2

cm

s

s

Response evaluation


Time History Analysis

cm/s2

s

Artificial earthquake compatible with design spectrum

Three different

phase models

cm/s2

s

Historical earthquake scaled to have the max. velocity 50cm/s

El Centro1940NS,

Taft 1952EW,

Hachinohe1968EW,

etc.

cm/s2

s

Site specific artificial earthquake

Wave generation

from the nearest

Fault, etc.

cm/s2

s

Bedrock

5% damping

cm/s2

s

Bedrock

5% damping

Earthquake response is obtained

by time history analysis

(numerical integration method)

using design earthquake ground

motions.


15/23

15


Time History AnalysisBuilding is modeled by MDOF nonlinear hysteresis system.

Sway

Rocking

RFL

10FL

9FL

8FL

7FL

6FL

5FL

4FL

3FL

2FL

Living Kitchen

10F

FL

8FL

7FL

6FL

5FL

4FL

3FL

2FL

1FL

Isolator Isolator Isolator

RFL

,800 6,000 2,700

15,500960 950

Y Y2 Y3

30,7

9

29,9

9

3,5

50

2,

860

2,8

60

GL

600

600

800

Responses are obtained by numerical integration method.


Confirmation of ultimate limit state

Example. LRB

Diameter: 800mm

Rubber sheet: 5.1mm

Number of sheets: 33

Rubber height: 168mm

Design criteria

21N/mm2

Design criteria

240% 168 = 403mm =

Compression stress (N/mm2)

Shear strain (%)

a. Allowable deformation of isolation device

b. Compressive and tensile load of isolator

c. Isolation gap (horizontal and vertical)

Isolation gap


16/23

16



Ultimate Shear Test

(from Prof. Nishi, Tokyo Institute of Technology, Japan)

Ultimate Compression Test

Contents

Introduction

Idea of BI system




Ultimate capacity of isolators, etc.



17/23

17

International Activity of JSSI

CIB/W114

As one of the working

commissions in CIB

(International Council for

Research and Innovation

in Building and

Construction), W114:

Earthquake Engineering

and Buildings has been

established since

November 2006 .

Headquarter: JSSI

Coordinator: Taiki SAITO

http://www.cibw114.net/


CIB/W114The first CIB/W114 meeting, "International Workshop on Response Control and Seismic

Isolation of Buildings," was held in Guangzhou, China on 27 November 2006.


18/23

18


CIB/TG44 bookContents

1. Introduction

2. Devices for Seismic Isolationand Response Control

3. A Comparative Study of

Seismic Isolation Code

Worldwide4. Observed Response of

Seismically Isolated Buildings

5. World Report

5.1 China5.2 Italy

5.3 Japan

5.4 Korea

5.5 New Zealand

5.6 Taiwan

5.7 The United of America

6. Conclusions

published in November 2006

China from Dr. Zhou Fulin adn Dr. Wen Liuhan

Around 600 base isolation buildings have been constructed. The

one was constructed in 1991.

35 base isolation buildings are constructed on the two-story reinforced concreteplatform of subway station in Beijing, China.

Base isolators at the large span structure of theShanghai F1 circuit.

Miniature building modelsfor shaking table test


19/23

19

Italy from Mauro Dolce, Massimo Forni and Alessandro Martelli

60

50

40

30

20

10

0

1981 1986 1991 1996 2001 2006

Currently, there are

only two seismically

isolated buildings in

Korea, with a third to

be built soon.

The Unison Research

and Development

Center building,

constructed in 1997,

was the first

seismically-isolated

building.

Korea from Dong Guen Lee


20/23

20

The second was

Traum Hous III, a 12-

story apartment

building in Seoul

Korea from Dong Guen Lee

The first seismically

isolated structure in

New Zealand was the

Motu Bridge in the

North Island

completed in 1974.

New Zealand from John X. Zhao

The isolation mechanism is provided by

stepping action of each of the two feet

of the piers. Steel dampers are used for

energy dissipation.

Rocking Seismic Isolation System


21/23

21

Construction of the first seismically-isolated building in the

USA was completed in 1985, and by mid-2005 there were

approximately 80 seismically-isolated buildings in the USA

USA from Ian Aiken and Andrew Whitaker

The first building in the

USA is the Foothill

Communities Law &

Justice Center, in Rancho

Cucamonga, California,

was completed in

1985,with 98 high-damping rubber bearings

located below the

basement level


The second building

application in the USA

was the City and County

Building, in Salt Lake

City, Utah, completed in

1989 with 208 lead-rubberand 239 natural rubber

bearings.

This project was the first

in the world to use

isolation for retrofit,

completed in 1989.


22/23

22

The USC University Hospital in

Los Angeles, completed in 1991,

was the first hospital in the world to

use seismic isolation with 68 lead-

rubber isolators and 81 natural-

rubber isolators.


Roof

6th

4th

LowerFoundation

The 1994 Northridge earthquake

Macedonia from Garevski A. Mihai and James M. Kelly

Primary School Pestalozzi" in Skopje, the first structure in the world

base isolated by means of rubber bearings constructed in 1969


23/23

Thank you for your attention.

Basic Concept of Base Isolation System for Buildings

Documents

Transcript of Basic Concept of Base Isolation System for Buildings