Ph.D. Thesis project of Paolo E. Sebastiani PBEE - Mala Rijeka Viaduct
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Transcript of Ph.D. Thesis project of Paolo E. Sebastiani PBEE - Mala Rijeka Viaduct
1
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
1. PERFORMANCE-BASED EARTHQUAKE ENGINEERING
CONDITIONAL PROBABILISTIC APPROACH
(IM-BASED METHODS)
APPROACHES
UNCONDITIONAL PROBABILISTIC
APPROACH
SEMI-PROBABILISTIC APPROACH (DM2008)
PHILOSOPHY
PBEE DETERMINISTIC APPROACH
EVALUATION, DESIGN AND
CONSTRUCTION OF STRUCTURES TO
MEET SEISMIC PERFORMANCE
OBJECTIVES
1.1 – PBEE Outline
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1.2 – Definition
Performance-based earthquake engineering (PBEE) consists of the evaluation,
design and construction of structures to meet seismic performance objectives
(expressed in terms of repair costs, downtime, and casualties) that are specified
by stakeholders (owners, society, etc.)
It is based on the premise that performance can be predicted and
evaluated with quantifiable confidence to make, together with the client,
intelligent and informed trade-offs based on life-cycle considerations rather than
construction costs alone.
Krawinkler, H. and Miranda, E. (2004). “Performance-Based Earthquake Engineering”. Chapter 9 of
Earthquake Engineering: From engineering seismology to performance-based engineering, edited by Y.
Bozorgnia, and V. Bertero, CRC press.
1. PERFORMANCE-BASED EARTHQUAKE ENGINEERING
1.3 – Assumptions
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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1.4 – Development of PBEE
Most of the concepts that are implemented in the context of PBEE are not new.
In various forms they have been explored, tried and partially
implemented in past design/evaluation guidelines and standards of
various countries and industries
In the United States various efforts were initiated during the early 1990s which
faced up to the many challenges of performance-based seismic design. The most
widely known ones are Vision 2000 (SEAOC, 1995), FEMA 273 and FEMA 274
(1996) and ATC-40 (1996)
1. PERFORMANCE-BASED EARTHQUAKE ENGINEERING
Krawinkler, H. and Miranda, E. (2004). “Performance-Based Earthquake Engineering”. Chapter 9 of
Earthquake Engineering: From engineering seismology to performance-based engineering, edited by Y.
Bozorgnia, and V. Bertero, CRC press.
1.5 – PBEE concepts in the Codes
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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1.6 – Vision 2000 report (SEAOC 1995)
1. PERFORMANCE-BASED EARTHQUAKE ENGINEERING
One of the many strong points of the Vision 2000 document is that it proposes
a comprehensive design/assessment/build process that incorporates important
aspects of:
• Selection of a suitable site
• Selection of suitable structural materials and systems
• Configuration and continuity of load path
• Quality of detailing
• Strength and stiffness
• Consideration of nonstructural and content systems
• Quality and consistency of design
• Quality of design review
• Quality of construction
• Quality of inspection
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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1. PERFORMANCE-BASED EARTHQUAKE ENGINEERING
Performance objectives for buildings, recommended in SEAOC (1995).
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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1. PERFORMANCE-BASED EARTHQUAKE ENGINEERING
CONDITIONAL
PROBABILISTIC
APPROACHES
PEER
METHOD
It is not in closed form but it allows more flexibility and generality in the evaluation of the desired so-called “decision variable”, not necessarily coinciding with Pf.
SAC/FEMA
It has the advantage of providing a closed-form expression for the failure probability (Pf), that can also be put in a partial factor format.
1.7 – Conditional Probabilistic Approaches
In the middle of the 90’s very promising results started to materialize (i.e.
Bazzurro and Cornell 1994, Cornell 1996). The problem was posed in terms of
a direct (probabilistic) comparison between demand and capacity, with the
demand being the maximum of the dynamic response of the system to a seismic
action characterized in terms of a chosen return period
Fib (2012) Probabilistic performance-based seismic design. Bulletin n°68, Fédération internationale du
béton, Lausanne, Switzerland
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
2.1 – Definition
The Pacific Earthquake Engineering Research (PEER) Center has focused for
several years on the development of procedures, knowledge and tools for
a comprehensive seismic performance assessment of buildings and
bridges
In the approach, decision variables are identified whose quantification, together
with an assessment of important uncertainties, will make it feasible to
characterize and manage economic and societal risks associated with
direct losses, downtime and collapse and life safety.
Krawinkler, H. and Miranda, E. (2004). “Performance-Based Earthquake Engineering”. Chapter 9 of
Earthquake Engineering: From engineering seismology to performance-based engineering, edited by Y.
Bozorgnia, and V. Bertero, CRC press.
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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2.2 – Components of PEER method: Performance Targets
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
It is assumed that a performance target can be expressed in terms of a
quantifiable entity and, for instance, its annual probability of exceedance. For instance, l$(y), the mean annual frequency (MAF) of the loss
exceeding y dollars, could be the basis for a performance target
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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2.3 – Components of PEER method: Decision Variables
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
The quantifiable entities, on which performance assessment is based, are
referred to as decision variables (DVs). Examples of DVs of primary interest are
the existence of collapse, the number of casualties, dollar losses and the length
of downtime
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
To compute DVs and their uncertainties, other variables have to be evaluated to
define:
1. The seismic hazard
2. The demands imposed on the structural systems by the hazard
3. The state of damage
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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2.4 – Components of PEER method: Seismic Hazard
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
The seismic hazard is quantified in terms of a vector of intensity measures (IMs),
which should define the seismic input to the structure. This vector could have a
single component, such as spectral acceleration at the first mode period of the
structure, Sa(T1), or could have several. If a single component is used, such as
Sa(T1), the hazard is usually defined in terms of a hazard curve. The outcome of
hazard analysis, which forms the input to demand evaluation, is usually expressed in terms of an MAF of IMs, i.e., l(IM),
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
12
2.5 – Components of PEER method: Engineering Demands Parameters
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
Given the ground motion hazard, a vector of engineering demand parameters
(EDPs) needs to be evaluated, which defines the response of the structure in
terms of parameters that can be related to DVs. Interstory drift is an example
of a relevant EDP for buildings
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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2.6 – Components of PEER method: Damage Measures DM
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
In most cases an intermittent variable, called a damage measure (DM), has to be
inserted between the EDP and the DV simply to facilitate the computation of
DVs from EDPs. A DM describes the damage and consequences of damage to a
structure or to a component of the structural, nonstructural or content system,
and the term G (DM|EDP) can be viewed as a fragility function for a specific
damage (failure) state (probability of being in or exceeding a specific damage
state, given a value of EDP).
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
The assessment problem has been “de-constructed” into the four basic
elements of
1. hazard analysis
2. demand prediction
3. modeling of damage states
4. failure or loss estimation
by introducing the three intermediate variables, IM, EDP and DM
To close the loop…
1. EDPs have to be related to IMs (Probabilistic Seismic Demand Analysis
PSDA)
2. DMs have to be related to EDPs (Damage Analysis)
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
15
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
Relationships between EDPs and IMs (also called Probabilistic Seismic Demand
Models PSDM) can be obtained through simulations, which should incorporate
the complete structural, geotechnical and SFSI (soil–foundation–structure
interaction) systems
2.7 – Probabilistic Seismic Demand Analysis in the PEER method
So the first step is the evaluation of a PSDM
The outcome of this process, which may be referred to PSDA, can be
expressed as G(EDP|IM) or more specifically as G[EDP ≥ y | IM = x], which is the
probability that the EDP exceeds a specified value y, given (i.e., conditional) that
the IM is equal to a particular value x
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
16
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
Synthetic or recorded accelerograms
SEISMIC LOADS
STRUCTURE
Geometry Meterials Method of design Ductility Isolation system
INPUTS
Type Range of values Scalar or vector One or more
EDP
IM
SETTINGS
Type Range of values Scalar or vector One or more
COMMON APPROACHES
BIN APPROACH
CLOUD METHOD
STRIPE METHOD
IDA SIMPLIFIED METHOD
IMPROVED CLOUD
METHOD MCS - LHS
EMPIRICAL METHOD
PSDM
2.8 – PSDM in the PSDA
Two values for each level of IM: - mIM , Median of EDP
- z, Standard deviation of EDP
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
A regression analysis can be used to obtain the mean (mIM) and the standard
deviation (z) by assuming the logarithmic correlation between median EDP and
an appropriately selected IM:
where the parameters "a" and "b" are regression coefficients obtained for
example by the nonlinear time history analyses
ln(𝐸𝐷𝑃) = ln 𝑎 + 𝑏 𝑙𝑛(𝐼𝑀)
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
18
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
Assuming a log-normal distribution of EDP at a given IM, the probability that the
EDP exceeds a specified value y, given (i.e., conditional) the IM, can be written
as:
where F is the standard normal distribution function
𝐺 𝐸𝐷𝑃 ≥ 𝑦|𝐼𝑀 = 1 − Φ ln 𝑦 − ln(𝑎 𝐼𝑀𝑏)
𝜁
The remaining variability in ln(EDP) at a given IM is assumed to have a constant
variance for all IM range, and the standard deviation can be estimated:
𝜁 = ln 𝐸𝐷𝑃𝑖 − (ln 𝑎 + 𝑏 ln 𝐼𝑀𝑖)
2𝑛𝑖=1
𝑛 − 2
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
19
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
2.9 – Damage analysis and fragility functions in the PSDA
The specified value y of EDP, defined previously, can be related to a Damage
Measure DM. Consequently it is possible to define some Limit States LS
according to different damaging.
STRUCTURAL CAPACITY
(DAMAGE ANALYSIS)
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
Nielson, B. G. (2005). “Analytical fragility curves for highway bridges in moderate seismic zones.”
PhD Thesis, Georgia Institute of Technology, Atlanta, Georgia.
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
Therefore G (DM|EDP) can be viewed as a fragility function for three
different damage states
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
22
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
2.10 – Loss analysis
The seismic fragility can be convolved with the seismic hazard in order to assess
the annual probability PAi of exceeding the ith damage state:
where H(a) is the hazard curve that quantifies the annual probability of
exceeding a specific level of IM at a site.
Additionally, under the assumption of time-invariant structural resistance, it is
possible to evaluate the T-year probability PTfi of exceeding the damage state ith,
estimated as:
𝑃𝐴𝑖 = 𝑃 𝐷𝐼 ≥ 𝐿𝑆|𝐼𝑀 𝑑𝐻(𝑎)
𝑑𝑎 𝑑𝑎
PTf 𝑖 = 1 − 1 − PA𝑖 T
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
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2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
2.10 – Loss analysis
For each damage state it is possible to define a nominal cost of restoration
which depends on the repair strategy. So the probability of exceeding a damage
state can be related to the probability of exceeding a “cost” to close the loop
of PEER method
Fib (2012) Probabilistic performance-based seismic design. Bulletin n°68, Fédération internationale du
béton, Lausanne, Switzerland
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
24
2. PEER METHOD: A PROBABILISTIC
DESIGN/ASSESSMENT APPROACH TO PBEE
2.10 – Loss analysis
At the same time it is possible to calculate the expected value of the life-cycle
costs due to seismic damage in present day dollars can be expressed as follow:
where i is the damage state, T=50 years is the remaining service life of the
bridge, Ci is the cost associated with damage state i. An inflation adjusted discount ratio, a=0.03, is used for converting future costs into present values
Wen, Y. K., and Kang, Y. J. (2001a). “Minimum Building Life-Cycle Cost Design Criteria. I:
Methodology.” Journal of Structural Engineering, 127(3), 330–337.
E LCC =1
αT 1 − e−αT −C𝑖
3
𝑖=1
ln 1 − PTf𝑖 − ln 1 − PTf𝑖+1
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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25
3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.1 – The case study
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
27
3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.2 – The case study: geometry
The case study bridge "Mala Rijeka" is one of the most important bridges on
the Belgrade - Bar International Line. The bridge was built in 1973 as the highest
railway bridge in the World (Worlds Record Lists) and it is a continuous five-
span steel frame carried by six piers of which the middle ones have heights
ranging from 50 to 137.5 m measured from the foundation interface. The main
steel truss bridge structure consists in a continuous girder with a total length
L=498.80 m. Static truss height is 12.50 m, and the main beams are not parallel,
but are radially spread, in order to adjust to the route line
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.3 – Uncertainties
AVAILABLE DATA
•Geometry
•Site Characteristics*
•Damage inspection made in
the 2007
NOT AVAILABLE DATA
•Pier’s section
•Materials
•Devices
Z. Radosavljevid and O, Markovic. (1976) Some Foundation Stability Problems of the Railway Bridge over
the Mala Rijeka. Rock Mechanics 9, 55--64
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.4 – Modeling of the highest pier
The response of the pier III in figure 1 is evaluated via non-linear dynamic
analyses run in OpenSees 2.2.2 (McKenna, 1997). The column is modelled with a
nonlinear element with fiber-section distributed plasticity
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.5 – Material assumptions
Deck (120 m for the 3th pier) : 870 kNs2/m
Pier (distributed along the pier) : 7166 kNs2/m
3.6 – Mass assumptions
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.7 – Section assumptions
•Tube 6.5 16.5 m x 6.516.5 m
(variable)
•0.5 m of thickness
•Rebar F26 / 0.2 m
SECTION A
P. E. Sebastiani – Ph.D. Student
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32
3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.8 – Pushover analysis to define limit states
First Cracking
st = 5.2 N/mm2 is the concrete tensile strength
SEC 107
SEC 105
SEC 103
SEC 101 P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.9 – Pushover analysis to define limit states
SEC 107
SEC 105
SEC 103
SEC 101
Yielding
ss = 440 N/mm2 is the steel yield strength
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.10 – Pushover analysis to define limit states
Three damage states DS namely slight, moderate and complete damage are
adopted in this study and their concerning limit values are shown in tab. 6.
Through the pushover analysis presented previously, the slight damage has been
associated to the achievement of maximum tensile strength of concrete, while
the moderate one to the yielding of the steel rebar.
A comparison between the values adopted by Choi et al. (2004) and the
ductility factor defined in the EC8 for piers, has allowed us to define also limit
values referred to the collapse.
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.11 – PSDM results with different type of retrofit
NOT ISOLATED ISOLATED (FRICTION-PEDULUM SYSTEM) ISOLATED (ELASTOMERIC BEARINGS)
Using the curvature ductility at the pier base mc and displacement ductility dc as
EDPs, for different type of IMs and type of retrofit, the PDSM results are the
following:
Sebastiani P.E., Padgett J.E., Petrini F., Bontempi F. (2014). Effectiveness Evaluation of Seismic
Protection Devices for Bridges in the PBEE Framework. In proceeding of: ASCE-ICVRAM-ISUMA
2014 - second International Conference on Vulnerability and Risk Analysis and Management
(ICVRAM) Liverpool, 13th-17th July 2014
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.12 – PSDM results with different type of retrofit
Sebastiani P.E., Padgett J.E., Petrini F., Bontempi F. (2014). Effectiveness Evaluation of Seismic
Protection Devices for Bridges in the PBEE Framework. In proceeding of: ASCE-ICVRAM-ISUMA
2014 - second International Conference on Vulnerability and Risk Analysis and Management
(ICVRAM) Liverpool, 13th-17th July 2014
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org
3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.12 – Fragility results
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.12 – Fragility results
In terms of damage probability, choosing the example of slight damage and
referring to the curvature ductility as EDP, the probability of damage during a
period of 50 years is: 23% for the structure without isolation, 7% for the
structure equipped with ERB, and 3% for the structure equipped with FPS
isolation.
Sebastiani P.E., Padgett J.E., Petrini F., Bontempi F. (2014). Effectiveness Evaluation of Seismic
Protection Devices for Bridges in the PBEE Framework. In proceeding of: ASCE-ICVRAM-ISUMA
2014 - second International Conference on Vulnerability and Risk Analysis and Management
(ICVRAM) Liverpool, 13th-17th July 2014
P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
www.francobontempi.org 38
3. APPLICATION TO THE “MALA RIJEKA” VIADUCT
3.12 – Example of expected cost calculation
P. E. Sebastiani – Ph.D. Student
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4. FUTURE WORK
1) Full 3D model of the Mala Rijeka Bridge
2) Loss estimation taking into account aging effects
3) Effectiveness Evaluation of different Seismic Protection Devices
4) Application to two representative categories of Highway bridges:
- Most common bridge type, i.e. short span, simply supported deck
- Less common bridge type, i.e. high piers, long span, continuous deck
DEMAND CAPACITY FRAGILITY
COMPONENT
SYSTEM
NETWORK
LOSS
? P. E. Sebastiani – Ph.D. Student
Sapienza University of Rome - a.a. 2013/2014
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KEYWORDS
PBEE
PRACTICE-ORIENTED TARGET
OPENSEES
SEISMIC ADJUSTMENT AGING
LIMIT STATES
ISOLATION (MFPS, ERB)
LCC
4. FUTURE WORK
P. E. Sebastiani – Ph.D. Student
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