“Real-time” seismic vulnerability assessment of a
high rise RC building using field monitoring data
Sotiria Karapetrou
Maria Manakou
Despoina Lamprou
Sofia Kotsiri
Kyriazis Pitilakis
Aristotle University of Thessaloniki
Istanbul, August 24-29, 2014
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
Laboratory of Soil Mechanics,
Foundations and Geotechnical
Earthquake Engineering, AUTH
Introduction
 Aim of this study: “real-time” seismic vulnerability assessment of RC
building using field monitoring data reflecting the actual state of the
structure (degradation due to time, possible pre-existing damage, changes
in geometry and mass distribution etc.)
 EU project REAKT (Strategies and Tools for Real Time EArthquake RisK
ReducTion): Rapid post-earthquake assessment of buildings based on field
monitoring data
 Target structure: high-rise RC hospital building in Thessaloniki
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
Laboratory of Soil Mechanics,
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Earthquake Engineering, AUTH
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Methodological framework
Fragility assessment of buildings using field monitoring data
Finite element
modeling (FEM)
Operational modal
analysis (OMA)
Evaluation of MAC values
Comparison between numerical
and experimental modes
Finite element model updating
Sensitivity in
material properties
Selection of the “best” FE model
Nonlinear incremental
dynamic analysis
Derivation of “real – time”
fragility
“Real-time” seismic vulnerability assessment
of a high curves
rise RC building using field monitoring
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Foundations and Geotechnical
Earthquake Engineering, AUTH
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Description of the hospital building in Thessaloniki
Target building
AHEPA Hospital complex
Target building: high-rise (8-storey) RC infilled MRF structure designed with low
seismic code level (SYNER-G taxonomy).
• It hosts both administration and hospitalization activities.
• It is composed of two adjacent tall building units that are connected with a
structural joint
• The foundation consists of simple footings without tie-beams combined partially
with a raft foundation.
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Description of the hospital building
RC buildings
Total mass (t)
fc (MPa)
fy (MPa)
fm (MPa)
UNIT 1
3719.0
14.0
220.0 and 500.0
3.0
UNIT 2
3112.0
14.0
220.0 and 500.0
3.0
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Temporary instrumentation array
• February 2013: ambient noise measurements (AUTH, GFZ)
N
S
36 triaxial seismometers:
Basement
UNIT 1
→ Mark short-period seismometers
(L4C-3D, 1Hz natural frequency)
→ EarthData recorders EDL (PR6-24)
UNIT 2
• 4 stations at each floor installed
along the middle corridor of the
building near and far the
structural joint.
4th floor
UNIT 1
UNIT 2
• North – South (NS) ‖ longitudinal
direction of the structure
Top floor
• 4 hour recordings
→ Sampling rate 500Hz
UNIT 1
UNIT 2
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Temporary instrumentation array
Basement
A
A’
Structural joint between the
building UNITS
UNIT 1
UNIT 2
Section A-A’
UNIT 1
UNIT 2
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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System identification and Operational modal analysis
(ΟΜΑ)
• MACEC 3.2 software (Reynders et al. 2011)
• OMA for the two adjacent building units separately (UNIT 1 and UNIT 2)
and for the entire hospital building analyzed as one (BUILDING).
• Grid of the models: the defined nodes correspond to the nodes that are
measured.
• Non-parametric and parametric identification techniques are applied.
• Non-parametric: Frequency Domain Decomposition FDD (Brincker et
al. 2001)
• Parametric: Stochastic Subspace Identification SSI (Van Overschee
and De Moor 1996)
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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System identification and Operational modal analysis
Frequency Domain Decomposition – FDD  Singular values
UNIT 1 - FDD
UNIT 2 - FDD
BUILDING - FDD
Stochastic Subspace Identification – SSI  Stabilization diagrams
UNIT 1 - SSI/COV
UNIT 2 - SSI/COV
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
BUILDING - SSI/COV
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System identification and Operational modal analysis
• Modal identification results for UNIT 1, UNIT 2 and BUILDING estimated
using parametric (SSI) and non-parametric (FDD) identification techniques
UNIT 1
UNIT 2
BUILDING
Mode
Mode type
1
Coupled
translational
1.65
1.65
0.8
1.65
1.65
0.9
1.65
1.65
0.8
2
Coupled
translational
1.90
1.91
1.3
1.91
1.91
1.1
1.91
1.91
0.8
3
Torsional
2.33
2.33
3.6
2.35
2.33
3.5
2.35
2.33
3.2
4
1st Longitudinal
3.50
3.47
5.4
3.58
3.52
5.8
3.58
3.51
6.4
5
2nd Longitudinal
5.20
5.15
3.0
5.22
5.16
1.1
5.20
5.15
2.1
FDD
(Hz)
SSI
(Hz, ξ %)
FDD
(Hz)
SSI
(Hz, ξ %)
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
FDD
(Hz)
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SSI
(Hz, ξ %)
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Finite element model updating
• “Initial” elastic numerical model of the building units:
based on the design and documentation plans provided by the Technical Service
of the hospital.
→ numerical modeling conducted in OpenSees (Mazzoni et al. 2009) separately for
UNIT 1 and UNIT 2
→ Elastic beam-column elements to model the RC elements (beam and columns)
→ Elastic truss elements to model the masonry infills: double strut model to
represent the in plane behavior of the infill panel.
→ Fixed base conditions are assumed for both building units
UNIT 1 - initial state
T (sec)/f(Hz)
UNIT 2 - initial state
T (sec)/f(Hz)
Mode 1
0.69sec/1.46Hz
0.67sec/1.50Hz
Mode 2
0.48sec/2.06Hz
0.49sec/2.05Hz
Mode 3
0.37sec/2.66Hz
0.36sec/2.77Hz
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Finite element model updating
• Sensitivity parameter: compressive strength of the masonry infill fm
• Normal distribution for fm (Mosalam et al. 1997)
→ mean value μ=3MPa
→ covariance COV=20%
• Masonry compressive strength
values calculated based on the
mean and standard deviation values
of the normal distribution adopted
with:
μ-3s≤ fm≤ μ+3s, s: standard deviation
• Elastic modulus in compression of masonry infills computed based on
compressive strength: Em= 1000fm (Paulay and Priestley 1992)
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
Laboratory of Soil Mechanics,
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Finite element model updating
• Evaluation of modal assurance criterion MAC values regarding the correlation
between numerical and experimental modes and the selection of the “best” updated
model
φj eigenvector j from numerical model
φEi eigenvector i from field monitoring test
• Selection of the “best model” based on MAC values (MAC>0.8)
→→ Optimal scenario
Emlong1
Emtransv1
Emlong1= 3GPa (fm=μ=3MPa)
Emlong1
Emtransv2 Emtransv2
Emlong2
Emlong2
Emtransv1
Emlong2=1.8GPa (fm=μ-2σ=1.8MPa)
Emtransv1=3GPa (fm= μ=3MPa)
Emtransv2=4.8GPa (fm=μ+3σ=4.8MPa)
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Finite element model updating – UNIT 1
Initial FEM
T (sec)/f(Hz)
Mode shape of updated
FEM
T (sec)/f(Hz)
Mode shape of
experimental model
T(sec)/f(Hz)
Coupled translational
T1=0.69sec/f1=1.46Hz
MAC
0.96
T1=0.64sec/f1=1.56Hz
T1=0.61sec/f1=1.65Hz
Coupled translational
T2=0.48sec/f2=2.06Hz
0.94
T2=0.53sec/f2=1.89Hz
T2=0.52sec/f2=1.91Hz
Torsional
T3=0.37sec/f3=2.66Hz
0.97
T =0.37sec/f =2.70Hz
Laboratory of Soil Mechanics,
T =0.43sec/f
=2.33Hz
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and
Geotechnical
3
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“Real-time” seismic vulnerability assessment of a3high rise RC building
using field monitoring
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Finite element model updating – UNIT 2
Initial FEM
T (sec)/f(Hz)
Mode shape of updated
FEM
T (sec)/f(Hz)
Mode shape of
experimental model
T(sec)/f(Hz)
MAC
Coupled translational
T1=0.67sec/f1=1.50Hz
0.98
T1=0.65sec/f1=1.54Hz
T1=0.61sec/f1=1.65Hz
Coupled translational
T2=0.49sec/f2=2.05Hz
T2=0.53sec/f2=1.89Hz
T2=0.52sec/f2=1.91Hz
<0.8
due to the
particular
structural
configuration
Torsional
T3=0.36sec/f3=2.77Hz
0.94
T =0.35sec/f =2.86Hz
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T =0.43sec/fEarthquake
3=2.33Hz
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3 building using field monitoring
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Inelastic finite element modeling
 Finite element code OpenSees (Mazzoni et al. 2009)
 Inelastic force-based formulation
 Geometric nonlinearity and distributed material plasticity (fiber based
approach)
 Concrete (confined and unconfined): Popovics concrete material model
(1973)
 Steel: uniaxial bilinear with kinematic hardening
 Masonry infills: inelastic struts assigned with an elastoplastic forcedisplacement relationship
 Diaphragm constraint is employed to account for the rigidity against the
in-plane deformation of the floor slabs.
 Fixed base conditions are assumed for both structural models
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Seismic input motion for incremental dynamic analysis
(IDA)
• 15 real ground motion records from the ESMD (http://www.isesd.hi.is) referring to
soil conditions at sites classified as stiff soil according to EC8 (soil type B)
→ Selection criteria
• moment magnitude: 5.8<Mw<7.2
• epicentral distance: 0<R<45km
• average acceleration spectra of the set
to be of minimal “epsilon” (Baker and
Cornell 2005) at 0<T<2.0sec with respect
to the acceleration spectrum adopted from
SHARE for a 475 year return period.
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Incremental dynamic analysis (IDA)
• IDA (Vamvatsikos and Cornell 2002 )  initial and updated models
• Intensity measure IM : peak ground acceleration PGA
• Engineering demand parameter EDP : max interstorey drift ratio maxISD
• Two limit states in terms of max interstorey drift maxISD
→ Immediate Occupancy (IO): 0.1% according to FEMA-356 for RC infilled MRFs
→ Collapse Prevention (CP): assigned on the IDA curve at a point where the IDA
is softening towards the flatline but at low enough values of maxISD so that we still
trust the model (Vamvatsikos and Cornell 2004).
IDA curves of updated UNIT 1
IDA curves of updated UNIT 2
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Incremental dynamic analysis (IDA)
• IDA (Vamvatsikos and Cornell 2002 )  initial and updated models
• Intensity measure IM : peak ground acceleration PGA
• Engineering demand parameter EDP : max interstorey drift ratio maxISD
• Two limit states in terms of max interstorey drift maxISD
→ Immediate Occupancy (IO): 0.1% according to FEMA-356 for RC infilled MRFs
→ Collapse Prevention (CP): assigned on the IDA curve at a point where the IDA
is softening towards the flatline but at low enough values of maxISD so that we still
trust the model (Vamvatsikos and Cornell 2004).
• CP limit state maxISD values defined on the IDA curve for each building unit
(initial and updated)
Initial model
Updated model
UNIT 1
0.014
0.011
UNIT 2
0.014
0.011
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Time-dependent fragility curves
 Two – parameter lognormal distribution functions:
 
 In  IM  - In IM 

P  DS / IM    





Where
Φ: the standard normal cumulative distribution function
IM: the intensity measure of the earthquake expressed in terms of PGA
(in units of g),
IM and β: the median values (in units of g) and log-standard deviations respectively
of the building fragilities
DS: the damage state.
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Time-dependent fragility curves
 Median values PGA: determined based on regression analysis of the IDA results
(PGA– maxISD) for each building unit
 Uncertainties are taken into account through the log-standard deviation β(t):
total dispersion related to each fragility curve
𝛽=
2
𝛽𝐷2 + 𝛽𝐶2 + 𝛽𝑑𝑠
 Three primary sources of uncertainty:
• βD: seismic demand (variability in the numerical results)
• βC: structural capacity (HAZUS=0.3 for low code structures)
• βds: definition of damage state (HAZUS=0.4)
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Fragility curves
• Comparative plots of the “initial” fragility curves derived for the two adjacent
building units with the corresponding fragility curves provided by Kappos et al.
(2003 and 2006)
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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Fragility curves
• Comparative plot of the fragility curves derived for the initial and updated models
of UNIT 1 and UNIT 2.
RC building
UNIT 1
UNIT 2
Finite Element
Model
Initial
Updated
Initial
Updated
Median PGA (g)
IO
CP
0.059
1.49
0.057
1.21
0.074
1.35
0.065
0.99
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
Laboratory of Soil Mechanics,
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Dispersion
0.78
0.76
0.79
0.72
23
Conclusions
• The present study provides further insight on the assessment of the “real-time”
seismic vulnerability of typical RC buildings using field monitoring data, taking into
account the actual state of the structure (degradation due to time, possible preexisting damages, changes in geometry and mass distribution, etc).
• The proposed updating procedure can be used to yield more reliable structural
models with respect to their real conditions in terms of structural detailing, mass
distribution and material properties
• The applied methodology in this study may be used in the context of “real-time”
risk assessment and post-seismic fragility updating.
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
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The work of this study was carried out in the framework of the
ongoing REAKT (http://www.reaktproject.eu/) project, funded by the
European Commission, FP7-282862.
Thank you for your attention!!
“Real-time” seismic vulnerability assessment of a high rise RC building using field monitoring
Laboratory of Soil Mechanics,
Foundations and Geotechnical
Earthquake Engineering, AUTH
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