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SEISMIC ISOLATION
SEISMIC PROTECTION STRATEGY EFFECT OF THE EARTHQUAKE
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 PROTECTION STRATEGY
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 PROTECTION STRATEGY
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 PROTECTION STRATEGY
SEISMIC ACTION
The geographic position
SEISMIC PROTECTION STRATEGY
SEISMIC ACTION
Elastic Response Spectrum (P100-2006)
Max Amplification
Factor
Design Response
Spectrum Basic
Acceleration
Reduction factor due to
the equivalent viscous
damping
SEISMIC PROTECTION STRATEGY
SEISMIC ACTION
Elastic Response Spectrum (P100-2006)
SEISMIC PROTECTION STRATEGY
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
Design approach according to European Standard (EN 1998)
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 PROTECTION STRATEGY DESIGN
Design approach according to European Standard (EN 1998)
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
SEISMIC PROTECTION STRATEGY DESIGN
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
EFFECT OF A BASE ISOLATION SYSTEM
Not Isolated Building Isolated Building
Fire Protection
EFFECT OF A BASE ISOLATION SYSTEM
Piping
Gap cover Details of non-structural elements
SEISMIC PROTECTION STRATEGY
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
SEISMIC PROTECTION STRATEGY
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
SEISMIC PROTECTION STRATEGY
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
SEISMIC PROTECTION STRATEGY
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
CE - CERTIFICATE OF CONFORMITY
FD and STU
CE - CERTIFICATE OF CONFORMITY
Friction Pendulum
CE - CERTIFICATE OF CONFORMITY
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)
Testing according to EN 15129
DYNAMIC TESTS ON SLIDING PENDUUM WITH TWO
SLIDING SURFACES AT EUCENTRE (UNIVERSITY OF PAVIA)
Testing according to EN 15129
DYNAMIC TESTS ON SLIDING PENDULUM
ISOLATORS - THERMOGRAPHIES
Testing according to EN 15129
TESTING EQUIPMENT FOR PENDULUM ISOLATORS
AT ALGALAB
Testing according to EN 15129
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
TESTING LABORATORIES: ALGALAB
Static Test on Pot Bearings
TESTING LABORATORIES: ALGALAB
Static Biaxial test on isolator type HDRB
TESTING LABORATORIES: ALGALAB
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
TESTING LABORATORIES: EUCENTRE PAVIA - ITALY
Hydraulic press for tests on bearings and isolators
TESTING LABORATORIES: EUCENTRE PAVIA - ITALY
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!