vulnerability assessment of buildings contribution from large-scale laboratory tests
DESCRIPTION
Vulnerability Assessment of Buildings Contribution from Large-scale Laboratory Tests. A. Pinto ELSA, JRC, Ispra (VA), Italy. Kocaeli (Turkey) Earthquake, August 17, 1999 (A. Elnashai, 1999). Mt. Parnes, Athens (Greece) Earthquake, Spet. 7, 1999 (M. Fardis & N. Bousias, 1999). - PowerPoint PPT PresentationTRANSCRIPT
ELSAELSA
Vulnerability Assessment of Buildings Contribution from
Large-scale Laboratory Tests
A. Pinto
ELSA, JRC, Ispra (VA), Italy
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Kocaeli (Turkey) Earthquake, August 17, 1999 (A. Elnashai, 1999)
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Mt. Parnes, Athens (Greece) Earthquake, Spet. 7, 1999 (M. Fardis & N. Bousias, 1999)
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Reinforced Concrete Buildings
Represent the largest part of the European building stock at risk, in earthquake prone urban areas
Many of the important structures [Hospitals, Schools, Emergency management, …] are RC structures
There is a lack of codified guidelines for seismic Assessment and Re-design, in Europe Design and Re-design may have different performance requirements
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Seismic Assessment &Retrofit of RC buildings
Design for earthquake resistance: No formal Seismic Design provisions- until the ‘50s in US and ‘60s in Europe
Issues/Difficulties Economical and political
High costs - compared with seismic resistance in new construction
Low premium market is willing to pay for higher safety
Tendency of politicians to avoid complex and socially sensitive problems
Provisions for design and detailing of members and structures: Standards in mid-’70s in US and mid-80s in Europe
Lack of control to the design, construction and maintenance processes
Why (causes)?
Technical Much easier to design a new ER
buildings than to assess and strength an old one
Lack of codified criteria and rules for redesign, which leads to somehow arbitrary interventions …(existing for masonry buildings …)
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Assessment --- Retrofitting
Assessment Determines the need for
seismic retrofit or not Identifies particular
weakness and deficiencies to be corrected
Requires: Tools to allow rapid
screening and empirical evaluation of existing structures
‘Solutions’: Conventional procedures Deformation and
displacement based evaluation procedures(Performance and model calibration from Lab Tests required)
Retrofitting To provide improved seismic
performance
Requirements: Technically feasible acceptable cost-benefit ratios
(cost benefit analysis)
Technical solutions according to the weakness
identified in the assessment procedure (local and/or global) and to the protection required:
• Stiffness
• Strength
• Ductility (deformation capacity)
• Damping or isolation
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Retrofitting ‘guidelines’ (General)
Key ideas Seismic retrofitting
combined with architectural remodeling, rehabilitation
and/or change in use Find a feasible and
acceptable solution allowing occupancy during the works
Technical Requirements Any intervention should not
prejudice the safety of any part of the building in any aspect
Continuity of the load path(s) between new and existing elements, floors, …
Foundations ?!
Retrofitting solutions New Shear-walls
Drift control, May solve irregularity problems, Design according to new codes, Foundations?!
Steel Bracing (with/out dissipation devices)
Very effective Connection between bracing
and concrete very peculiar
Jacketing (Steel, RC, FRC)
Element strength and deformation capacity (local)
Joints ?!
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ICONS - Topic 2Assessment Strengthening & Repair
ELSA
TMR-Large-scale Facility
European Laboratory for Structural Assessment (ELSA)
EC, Joint Research Centre, ISIS, SSMU, TP480
2120 Ispra (VA), Italy
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Assessment Strengthening & Repair
The research work is part of research programme of the
ICONS TMR-Network
Project Participants:E.C. Carvalho, E. Coelho, A. Campos-Costa, LNEC, Lisbon (PT)
A.S. Elnashai, R. Pinho, Imperial College of London (UK)M.N. Fardis, S.N. Bousias, G. Tsionis, University of Patras (GR)
GM. Calvi, A. Pavese, M. Recla, University of Pavia (IT)P.E. Pinto, G. Monti, University of Rome (IT)
J. Bouwkamp, S. Gomez, University of Darmstadt (DE)E. Alarcon, R. Perera, H. Lutz, Univ. Politecnica of Madrid (ES)
A. Plumier, University of Liege (BE)JM. Reynouard, INSA de Lyon (FR)
A.V. Pinto, G. Verzeletti, J. Molina, H. Varum, ELSA, JRC, Ispra (IT)
Other Contributions:
M. Griffith, University of Adelaide, Australia
The tests at the ELSA laboratory were financed under the TMR - Large-scale Facilities programme of the European Commission
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Tests on 4-storey RC Frames Objectives
Assessment of a typical RC frame representative of existing buildings
Design and Construction practice of 40~50 years ago • Simplified design (8% seismic coefficient), (concrete - C16/20, Steel -
Smooth rounded bars), lap-splicing, 90 degrees bent stirrups, no shear reinforcement in joints, Strong beam - Weak column system
Bare frame vs masonry Infilled frame
Assessment of retrofitting schemes and techniques Selective Retrofitting solutions
(balancing Ductility, Strength and Stiffness) Shotcrete of existing infill masonry walls K-bracing with shear-link (additional strength and damping)
Other aspects (Plastic-hinge length, Slab participation, Shear and bending deformations of Stocky column, Joints’ behaviour …)
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Frame lay-out
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Beam Reinforcement
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Column Reinforcement
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The ICONS Frame
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Transport
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ICO
NS
Fra
mes
Specimen A
Specimen B
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Test ProgramS
peci
men
BS
peci
men
A
Bare Frame (BF) Selective Retrofit (SR)
Infilled Frame (IN) Shotcrete (SC)
K-Bracing/Shear-link (KB)
Cyclic Test
PSD Tests
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Bare Frame and Selective Retrofit Frame Tests
Testing Programme Pseudo-dynamic tests for increasing earthquake
intensities (475, 975 and 2000 yrp)
A ‘complete’ measuring system Global (Storey forces and displacements) Local refined [rotations, deformations (joint, slab, column,
beam)] Photographic and video documentation
Detailed damage descriptions Damage categorization, Reparability …
Vulnerability and ultimate capacity Quantify Improved performance of retrofitted frame
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Instrumentation (Inclinometers)
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Instrumentation (Local)
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Earthquake Test at ELSA
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BARE FRAME3rd storey - Shear-Drift diagrams
475 yrp975 yrp
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BARE FRAME
0
1
2
3
4
0 0.5 1 1.5 2 2.5 3
Drift (%)
Sto
rey
475 yrp
975 yrp
Max. Inter-storey Drift Profiles
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BARE FRAME975 yrp test
3rd Storey collapse
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Selective Retrofitting Schemes
A
A ' S e c t i o n A - A '
S t e e l P l a t e s ( F e 4 3 0 )
60
12
0
60
19
0
B B '
12
0
19
0
Strength-only intervention
Ductility-only intervention
(Elnashai and Pinho, 1999)
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Selective Retrofitting Schemes
Strength-only intervention
Ductility-only intervention
Ductility andStrength intervention
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Max. Inter-storey Drift Profiles
REPAIRED FRAME
0
1
2
3
4
0 0.5 1 1.5 2 2.5 3 3.5
Drift (%)
Sto
rey
475 yrp
975 yrp
2000 yrp
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Max. Drift Profiles
BARE FRAME
0
1
2
3
4
0 0.5 1 1.5 2 2.5 3
Drift (%)
Sto
rey
475 yrp
975 yrp
REPAIRED FRAME
0
1
2
3
4
0 0.5 1 1.5 2 2.5 3 3.5
Drift (%)
Sto
rey
475 yrp
975 yrp
2000 yrp
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Global Drift
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2
1 1.2 1.4 1.6 1.8 2
Input Intensity (Acc_max/Acc_ref)
Glo
ba
l Dri
ft (
%)
Bare Frame (BF)
Collapse of BF
Selective Retrofit (SR)
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Max. Inter-storey Drift
0
0.4
0.8
1.2
1.6
2
2.4
2.8
1 1.2 1.4 1.6 1.8 2
Input Intensity (Acc_max/Acc_ref)
Dri
ft (
%)
Bare Frame (BF)
Collapse of BF
Selective Retrofit (SR)
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Storey Maximum-Shear Profiles
0
1
2
3
4
0 50 100 150 200 250 300
Shear (kN)
Sto
rey
BF 475BF 975SR 475SR 975SR 2000
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Infilled Frame with openings
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Infill construction
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Max. Drift Profiles
BARE FRAME
0
1
2
3
4
0 0.5 1 1.5 2 2.5 3
Drift (%)
Sto
rey
475 yrp
975 yrp
INFILLED FRAME
0
1
2
3
4
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Drift (%)
Sto
rey
475 yrp
975 yrp
2000 yrp
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Shear-Drift (Storey 1)Infilled and Bare Frame
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Global Drift
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2
1 1.2 1.4 1.6 1.8 2
Input Intensity (Acc_max/Acc_ref)
Glo
ba
l Dri
ft (
%)
Bare Frame (BF)
Collapse of BF
Selective Retrofit (SR)
Infilled Frame (IN)
Infilled Frame (IN)
Trend (IN)
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Max. Inter-storey Drift
0
0.4
0.8
1.2
1.6
2
2.4
2.8
1 1.2 1.4 1.6 1.8 2
Input Intensity (Acc_max/Acc_ref)
Dri
ft (
%)
Bare Frame (BF)
Collapse of BF
Selective Retrofit (SR)
Infilled Frame (IN)
Infilled Frame (IN)
Trend (IN)
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Shotcrete
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“Shotcrete”
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Max. Drift Profiles
INFILLED FRAME
0
1
2
3
4
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Drift (%)
Sto
rey
475 yrp
975 yrp
2000 yrp
SHOTCRETE
0
1
2
3
4
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Drift (%)
Sto
rey
475 yrp
975 yrp
2000 yrp
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Shear-Drift (Storey 1)Shotcrete and Infilled Frame
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Column Shear-out
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Column Shear-out
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Max. Inter-storey Drift
0
0.4
0.8
1.2
1.6
2
2.4
2.8
1 1.2 1.4 1.6 1.8 2
Input Intensity (Acc_max/Acc_ref)
Dri
ft (
%)
Bare Frame (BF)
Collapse of BF
Selective Retrofit (SR)
Infilled Frame (IN)
Infilled Frame (IN)
Trend (IN)
Shotcrete (SC)
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Response maximum values
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Concluding Remarks
RC frame Assessment
Storey mechanism ~1% drift for DE Collapse for 1,4xDE
(~2.5% drift)
RC frame with infills Assessment
Much Higher resistance Hiding irregularity Much Lower deformation
demands Structural integrity for 1.4xDE
but heavy damage to infills Story mechanism markedly
prompted after peak resistance (Softening)
Selective Retrofitting ‘Too good to be true’
well known structural characteristics, high costs, no infills
Withstanding 1.8xDE without serious damages and a stable dissipation mechanism (~3%Drift)
Infill Shotcrete Infill protection Slight lower softening and
higher ductility Column Shear-off (Shear-
out)
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ONGOING AND FUTURE PROJECTS AT ELSA
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SPEAR project (2001-2004)
Torsionally Unbalanced Structure to be tested at ELSA:
Simplification of an existing Greek 3-storey building
Designed for gravity loads Designed using the Greek
design code applied from 1954 to 1995
Doubly non symmetric plan configuration, regular in elevation
2-bay frames spanning from 3 to 6 m (10m x 10m)
3-DOF PsD Test
Partners:JRC (P. Negro), U.Patras (M. Fardis),
U.Pavia, U.Rome, IC-London, EQE-London, U.Ljubljana, U.Cyprus, LNEC-Lisbon,Other: ECOLEADER
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RC Flat-slab Structure (2002-3)
5.20
1.25
2.80
1.15
8.50
3.00 4.00 1.50
2.80 1.25
9.00
1.150.20
2.80
2.80
3.30
0.30
0.40
0.50
8.50
3.00 4.00 1.50
5.20
0.30
0.50
0.50
0.30
0.50
0.40
Shear-punching (detailing for seismic) Essentially non-dissipative (?) Significantly more flexible than
traditional frame/wall or frame structures Second order, P-d, effects
Additional measures for guiding conception and design
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JRC-ELSAInstitutional Programme (2003-6)
Creation of a Virtual Laboratory: - To link structural engineering
research sites across Europe, - Provide data storage facilities
and repositories,
- Offer remote access to the latest research tools, and - Enhance experimental techniques and procedures by full
exploitation of the electronic communication facilities (enlarged participation in testing preparation, conduction, analysis, distributed testing).
To explore the possibility of developing a common advanced platform for analytical/computational development and simulation