Earthquake Resistant Structures – Design, Assessment and Rehabilitation:Design Principles of Seismic IsolationFull description
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Complete study of earthquake isolationDescripción completa
Antenna isolation calculation
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Complete study of earthquake isolation
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Sanatatea Optima de-a lungul vietii. Vol. 4 Sanatatea adultului, cap. Nutritia
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SEISMIC ISOLA ISOLATION TION
EFFECTSEISMIC OF THEPROTECTION EARTHQUAKE STRATEGY
EFFECTSEISMIC OF THEPROTECTION EARTHQUAKE STRATEGY
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
T 2
M K
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 Response Spectrum depending on the damping
DESIGNSEISMIC PROTECTION STRATEGY Design approach according to European Standard (EN 1998) CA PA CITY DESIGN The earthquake d e f o r m a t i o n :
energy
is
absorbed
by
the
structure
with
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;
plastic
DESIGNSEISMIC PROTECTION STRATEGY Design approach according to European Standard (EN 1998) SEISMIC ISOL ATION T h e s e is m i c e ff e c t s a r e r e d u c e d a n d t h e d es i g n w i l l b e m a d e w i t h o u t p l a s t ic d e f o r m a t io n : •
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
DESIGNSEISMIC PROTECTION STRATEGY Design approach according to European Standard (EN 1998) SEISMIC ISOLATION T h e s ei s m i c e ff e c t s a r e r e d u c e d a n d t h e d e s i g n w i l l b e m a d e w i t h o u t p l a s t ic d e f o r m a t io n :
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
EFFECT OF A BASE ISOLATION SYSTEM
Not Isolated Building
Isolated Building
EFFECT OF A BASE ISOLATION SYSTEM
Fire Protection
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 Spring of constant K
T 2
M K
Pendulum of length l
T 2
l g
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
RE-CENTERING OF THE ISOLATION SYSTEM
Energy dissipation and Re-centering capability are two antithetic functions. 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 E H.
Ei = ES + EH + EV The energy EV dissipated by viscous damping does not participate in the re-centering process.
RE-CENTERING OF THE ISOLATION SYSTEM
According to EN 15129
E s
0,25E h
Where:
Es is the reversibly stored energy Eh is the dissipated energy
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
PERFORMANCE ORIENTED CLASSIFICATION OF ANTISEISMIC DEVICES (ACCORDING TO EN15129) 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
THE COMPLETE STRUCTURE OF EN 15129 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.
Scope Normative references Terms and definitions, symbols and abbreviations General design rules Rigid connection devices Displacement dependant devices Velocity dependant devices Isolators Combination of devices Evaluation of conformity Installation In-service inspection
THE MAIN CONCEPTS 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; 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 MARKING – INFORMATION TO BE REPORTED 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 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)
TESTING ACCORDING TO EN 15129 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
FACTORY PRODUCTION CONTROL - TEST FREQUENCIES FPC 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
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 e v er y p r o j e c t 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 structure’s life. Therefore they shall fulfil also all relevant requirement for bearings.
CONCLUSIONS How much is the cost of the seismic isolation? Values %
