seismic isolation v4

SEISMIC ISOLATION

SEISMIC PROTECTION STRATEGY EFFECT OF THE EARTHQUAKE

SEISMIC PROTECTION STRATEGY

SEISMIC ACTION

The seismic action is represented by accelerograms that define the ground

acceleration vs time


SEISMIC ACTION

In the case of a single DOF mass the seismic action can be represented by the

Response Spectrum that defines the acceleration vs. the natural period of vibration

K

MT 2


SEISMIC ACTION

The Elastic Response Spectrum give the acceleration of the structure in function of

the following parameters:

The geographic position;

The Earthquake Return Period (500 750 2475 years);

The ground type;

The ground morphology;

The equivalent viscous damping of the structure (capacity of dissipating energy

- Ductility);


SEISMIC ACTION

The geographic position


SEISMIC ACTION

Elastic Response Spectrum (P100-2006)

Max Amplification

Factor

Design Response

Spectrum Basic

Acceleration

Reduction factor due to

the equivalent viscous

damping


SEISMIC ACTION

Elastic Response Spectrum (P100-2006)


Response Spectrum depending on the damping

Design approach according to European Standard (EN 1998)

CAPACITY DESIGN

The earthquake energy is absorbed by the structure with plastic

deformation:

The structure will be damaged (plastic hinges);

The design follows principles of high ductility;

The stability is obtained increasing the structural resistance;

The serviceability is not granted after a seismic event;

SEISMIC PROTECTION STRATEGY DESIGN


SEISMIC ISOLATION

The seismic effects are reduced and the design will be made without

plastic deformation:

The structure will NOT be damaged (NO plastic hinges)

The design DOES NOT follow principles of high ductility

The stability is NOT obtained increasing the structural resistance

The serviceability is not granted after a seismic event



SEISMIC ISOLATION

The seismic effects are reduced and the design will be made without

plastic deformation:

The structure is designed to remain ELASTIC under REDUCED ACTIONS

DAMAGES are concentrated only in the SEISMIC DEVICES


EFFECT OF A BASE ISOLATION SYSTEM

The base isolation is the only way to

protect both the structure and the

non-structural parts and its contents


Not Isolated Building Isolated Building

Fire Protection


Piping

Gap cover Details of non-structural elements


The strategy is very clear looking at the shape of the response spectrum

Increasing the Natural Period of the structure

Introducing Energy Dissipation

Generally both strategies are used in combination


Increase the Natural Period of the structure

Inserting between structures and foundations an oscillator that forces the

structure to move mainly according to the natural mode of the oscillator

K

MT 2

Spring of constant K Pendulum of length l

g

lT 2


Energy Dissipation is obtained by:

Friction

Metals Yielding

Fluid or Rubber Viscosity

All types of energy dissipation produce a heat equivalent to the

dissipated energy


Displacement Spectrum depending on the damping

Energy approach:

the re-centering capability of a seismic isolation system is based on a

comparison between the energy stored by the system in a reversible form

ES (elastic, potential etc.) and the one hysteretically dissipated EH.

Ei = ES + EH + EV

Energy dissipation and Re-centering capability are two antithetic functions.

The energy EV dissipated by viscous damping does not participate in the

re-centering process.

RE-CENTERING OF THE ISOLATION SYSTEM

RE-CENTERING OF THE ISOLATION SYSTEM

hs EE 25,0

Where:

Es is the reversibly stored energy

Eh is the dissipated energy

According to EN 15129

FUNCTIONS OF A BASE ISOLATION SYSTEM

Seismic Isolators are devices providing four functions:

Support the vertical load

Provide lateral flexibility

Provide a restoring force

Damp the energy

THE STANDARDS FOR THE ANTISEISMIC DEVICES

In Europe:

EN 1998 (Eurocode 8)

EN 1337 Structural Bearings

EN 15129 European Standard for Antiseismic Devices

In USA:

AASHTO LRFD Guide Specification for Seismic Isolation Design

DISPLACEMENT ACCORDING TO EN 15129

The seismic displacement obtained from a dynamic analysis shall be

combinated with the displacements due to other causes.

The maximum displacement is calculated by the sum of the displacements

due to:

Permanent actions

Long term deformations (Creep & Shrinkage)

50% Thermic Displacement

150% Seismic Displacement

120% Seismic Displacement (Buildings)

(Bridges)

TYPE ORIENTED CLASSIFICATION OF ANTI-SEISMIC

DEVICES

- HDRB (High Damping Rubber Bearings)

- LRB (Lead Rubber Bearings)

- Sliding Pendulum Isolators

- Hydraulic Devices

Viscous Dampers

Shock Transmission Units STU

- Hysteretic Devices

Hysteretic dampers

Hysteretic bracings

Rigid connection devices

Restraints (Dowels and Guides)

Hydraulic connecting devices STU

Displacement Dependent Devices

Linear Devices

Non Linear Devices HY

Velocity Dependent Devices FD

Isolators

Sliders

Rubber Bearings (High or Low Damping)

Sliding Pendulum

PERFORMANCE ORIENTED CLASSIFICATION OF

ANTISEISMIC DEVICES (ACCORDING TO EN15129)

1. Scope

2. Normative references

3. Terms and definitions, symbols and abbreviations

4. General design rules

5. Rigid connection devices

6. Displacement dependant devices

7. Velocity dependant devices

8. Isolators

9. Combination of devices

10. Evaluation of conformity

11. Installation

12. In-service inspection

THE COMPLETE STRUCTURE OF EN 15129

As far as possible the standard shall be performance oriented;

Devices shall be CE marked;

Prototype tests are required on at least on 2 prototypes;

Factory production control tests shall be performed on a certain

percentage of the manufactured devices;

THE MAIN CONCEPTS OF EN 15129

CE marking

It is mandatory in all CEN Countries (28 European states);

It implies regular audits of the manufacturer by a Notified Body;

Manufacturers shall certify the conformity;

Devices can freely circulate in all CEN Countries;

CE Mark

Identification N. of the Notified Body

Address of the manufacturer

Year

CE conformity certificate Number

Reference Standard

Device identification Number

Characteristics of the device

0123-CPD-0001

Any Co Ltd, PO Box 21, B-1050

01

0123-CPD-0456

EN 15129:2010

DEVICE N

High Damping Rubber Bearing

Characteristic load bearing resistance (kN)

Characteristic rotation capacity (rad)

Horizontal Distorsion capability (mm)

Durability: conforming

CE MARKING INFORMATION TO BE REPORTED

CE MARKING

In CEN countries seismic devices shall be provided by the CE mark respecting all

the requirements of the EN 15129.

In order to obtain the CE mark for a product the supplier shall perform:

The Factory Production Control (initial inspections, check of the used materials, periodic audits, )

The execution of the type tests with the presence of a Notified Body

At the end of this process the Notified Body release the Certificate of

Conformity (CE MARK)

Every time that the material, the load, the displacement or one of the design

parameters is changed more than a defined % only the type testing shall be

repeated.

After completion of succesful type tests the extension of the CE mark for the new

parameters is obtained

CE - CERTIFICATE OF CONFORMITY

HDRB and LRB


FD and STU


Friction Pendulum


Hysteretic bracings (E-PAD)

TESTING ACCORDING TO EN 15129

There are 2 levels of tests:

Type Tests

Qualification of the device based on type, load, displacement, material,

main parameters

Routine Tests (Factory Production Control Tests)

Tests to check the manufactured devices (from 5% to 20% of the overall

supply)

Type testing according to EN15129

Shall be performed on 2 prototypes

Shall be repeated if the design parameters vary more than 20%

For rubber isolators only type test on models scaled 1:2 is allowed

TESTING ACCORDING TO EN 15129

High Damping Rubber Bearings 20%

Lead Rubber Devices 20%

Hysteretic Dampers 2%

Hydraulic Devices* 5%

Sliding Pendulum Isolators* 5%

* Dynamic test required

FPC Testing according to EN 15129

FACTORY PRODUCTION CONTROL - TEST

FREQUENCIES

BI-AXIAL TEST ON A PAIR OF RUBBER ISOLATORS

(ALGALAB)

Testing according to EN 15129

TEST OF A SLIDING PENDULUM AT THE EUCENTRE

LABORATORY (UNIVERSITY OF PAVIA)


DYNAMIC TESTS ON SLIDING PENDUUM WITH TWO

SLIDING SURFACES AT EUCENTRE (UNIVERSITY OF PAVIA)


DYNAMIC TESTS ON SLIDING PENDULUM

ISOLATORS - THERMOGRAPHIES


TESTING EQUIPMENT FOR PENDULUM ISOLATORS

AT ALGALAB


TESTING ACCORDING TO AASHTO

There are 2 levels of tests:

Type Tests

Qualification of the device for every project both in seismic and service

condition

Routine Tests

Tests to check the manufactured devices on the 100% of the products to

be supplied

TESTING LABORATORIES: ALGALAB

ALGA is provided of an internal testing labotatory equipped with the following main testing devices:

Static hydraulic press for the application of vertical loads up to 50.000 kN and simultaneously horizontal loads up to 20.000 kN

Dynamic equipment with continuos oil flow of 600 l/min and maximum flow up to 1800 l/min at 210 bar; dynamic actuators up to 16.000 kN, 15 data acquisition channels, frequency analysis up to 1000 Hz


Static Test on Pot Bearings


Static Biaxial test on isolator type HDRB


Dynamic test on STU 16000 kN (Carquinez Bridge California)

TESTING LABORATORIES: EUCENTRE PAVIA - ITALY

EUCENTRE is provided by a testing laboratory equipped with the following main testing devices:

Hydraulic press for the application of static vertical loads up to 50.000 kN and dynamic vertical load up to 40.000 kN with simultaneous horizontal load of 1700 kN and displacement up to 500 mm

Dynamic actuator up to 3750 kN with velocity up to 1 m/s

Shaking table with movement up to 500 mm and dynamic load up to 1700 kN


Hydraulic press for tests on bearings and isolators


Dynamic test on a viscous damper FD 2000/2400

TESTING LABORATORIES: SAN DIEGO

(UCSD) - USA

The University of California (UCSD) San Diego - USA is provided by a testing laboratory equipped with the following main testing devices:

Hydraulic press for the application of triaxial loads up to 53.000 kN dynamic vertical load, 8900 kN horizontal load and max. displacement of 1200 mm, velocity up to 1.8 m/s

COST-BENEFITS OF THE ISOLATION SYSTEMS

HDRB LRB PS HY FD

Energy dissipated 1 3 3 5 5

Period shift 3 3 5 3 3

Re-centering capacity 5 4 4 3 1

Initial cost 3 4 5 4 1

Maintenance 5 5 5 4 3

CONCLUSIONS

There are many kinds of anti-seismic devices that proved their reliability and efficiency and can meet nearly any requirement of the designer in order to

protect structures from the earthquake

In addition isolators can protect also the content of the structure

Quality assurance of the devices is of primary importance. Devices may be required to perform only few second in the life time of the structure. Their

failing would vanish the whole investment.

Isolators shall act also as structural bearings all days of structures life. Therefore they shall fulfil also all relevant requirement for bearings.

CONCLUSIONS

Values % not isolated bridge Isolated Bridge

Deck 50 50

Bearings 1 24

Piers & Found. 49 35

TOTAL 100 8789

How much is the cost of the seismic isolation?

Thanks for your attention!

seismic isolation v4

Documents

seismic effects

protection effect

capacity design

damping design approach

plastic deformation

earthquake energy

european standard en

contents effect