Minutes of
PEER Van Nuys Testbed Meeting
Nov. 8, 02
Deliverables for year six (incomplete, based on discussion):
1- General Issues:
i)
ii)
iii)
iv)
Solving the M-P-V problem
Shear wall. Develop a shear wall model in Opensees. It is essential if
we want to do assessment of the Van Nuys retrofit.
Post processing tools in Opensees to extract ALL relevant information.
Better models for piles and shallow foundations.
2- Beam-Column Joints modeling in Van Nuys model (Prof. Lowes)
Three options exist or to be implemented:
i)
Scissors elements
ii)
The steel panel zone element (Krawinkler)
iii)
Multi-spring joint model
iv)
Prof. Deierlein’s model
And what to do to get fragility curves!
3- Simulating column axial failure and consequences
Includes the following actions:
i)
Finalize development and implementation of column model including
axial “failure”.
ii)
Define a subgroup for this purpose (Prof. Deierlein, Prof. Lowes, and
Ken Elwood)
iii)
Check validation of model.
iv)
Do the modeling in Van Nuys.
4- Posting more sensitivity results on the webpage (Prof. Lowes)
Calls for a meeting including Prof. Lowes and Prof. Miranda to come up with the
parameters needed in the sensitivity study. Currently, the following parameters
are considered:
i)
ii)
iii)
Effective moment of inertia (extent of cracking)
Restraints at base connection
Types of elements: linear elastic, equivalent elastic, concentrated
plasticity, distributed plasticity, etc
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5- Show that soil structure interaction will not have a significant effect on the
Van Nuys structures response.
Considering the results presented by T. Nagae and Prof. Kutter, it is quite likely
that soil structure interaction will not have a significant effect on the structural
response of the existing structure. This should be verified with the Opensees
model of Van Nuys structure (spring properties to be provided by B. Kutter to L.
Lowes).
6- Deliverables by Prof. Deierlein
i)
ii)
iii)
Column shear element in Opensees
Column axial failure element in Opensees
Post processing material for Opensees?
7- Likelihood of column axial failure and consequences of failure in Van Nuys
building (Prof. Lowes)
8- Van Nuys testbed report
Deliverables and schedule identified in report outline – see web site.
9- Down time modeling (Prof. Miranda)
Miranda is “overloaded”.
Option 1 = no downtime modeling for Van Nuys
Option 2 = K. Porter to test his approach
Option 3 = Prof. Comerio to test her approach
10- Documentation of past experimental data in a format suitable for DM
modeling (Prof. Lehman)
The PEER experimental results need to be brought into a format suitable for
damage modeling. First, such a format needs to be established. Should involve
i)
Robertson
ii)
Stanton
iii)
Wallace
iv)
Eberhard
Develop a questionnaire for obtaining expert opinions on repairing damaged
components (scenario, costs, repair action, etc.). Also, analysts and
experimentalists should arrive at measures that both can measure/predict (strain?
curvature? crack size? rotation? etc.)
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Minutes of General Discussion:
Structural Model:
Prof. Lowes:
 Opensees 2D models with interior and exterior frames are
ready.
 Shear capacity of columns is calculated, and failure is modeled
by limiting flexural strength..
 Splice failure is important and is considered in the Van Nuys
model.
 In the lumped plasticity model, the elastic characteristics of
the intermediate beam-column element are modified till the
first natural period of the system is 1.5 sec.?? The reduction
factor for Igross is 0.5 at the moment.
 The current model assumes rigid elements at the joints with
the beam and column width dimensions (not a centerline
model)
 Try to model soil-foundation interaction with p-y springs and
see what will happen to the response. It is believed that there
will be not much change but this will be a sanity check.
 Will model the joints by using different elements developed in
Opensees:
o Scissors elements
o Multi-spring joint model
o Prof. Deierlein’s model
A subgroup of Prof. Deierlein and Prof. Lowes will meet to
decide on this matter.
 Will model the column axial failure (if possible) by using
Ken’s models. His models do exist now but need validation.
Prof. Miranda:
 Has done some sensitivity study on the period of the structure
and reported it is between 0.5 to 2.0 seconds. He believes that
1.5 seconds is a reasonable estimate for the pre-Northridge
condition.
 The building has gone through 1.5% drift during Northridge. It
is believed that it will collapse at 2% drift.
 Prof. Trifunac has reported large soil structure interaction
which Prof. Miranda believes is not realistic.
 He wants to list the important parameters for sensitivity
analysis. Also, believes in some cases it may be necessary to
consider combinations of parameters. To be posted on the
web site.
 He proposed to introduce another integral to the triple integral
of PEER to consider the uncertainty in the structural model.
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
Prof. Cornell believed it is not necessary as it will be taken
care of in the IM-EDP evaluation.
Nonstructural component modeling is important but this calls
for a lot of work specially using a 3D model. It is shelved for
later.
Prof. Kutter:
 The soil is pretty stiff and uniform in this project but he does
not know where the bedrock is.
 According to the slides he showed, there is not that much
difference in the lower level soil response and surface soil
response around the 1.5 second period, but at lower periods
were the higher modes are, differences do exist. The bottom
line is the soil depth will not have much influence.
 He liked what Takuya Nagae had done and was interested to
see his results. It was decided to model the soil with p-y
springs and see what will be the effect on the structure – to
confirm that there will be not much change in the response by
modeling the soil.
Performance Metrics and Decision Variables
Professor May gave a presentation that is reproduced on the following pages.
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PEER Testbed Decision Variable Discussion
Summary of Meeting 10/22/02 – P. May Notes
This note summarizes a meeting among “social science types” (Stephanie Chang,
Anthony Falit-Baiamonte, Ufuk Inces, Peter May, and Jack Meszaros) with telephone
coordination with Keith Porter. Background material for this discussion is a summary of
past research and testbed discussions of dv’s prepared by P. May dated 9/24/02.
Issues Discussed
1. Relevant decision variables and their operationalization for the PEER PBEE
methodology.
2. Decision variables and their operationalization for the LSA and VN testbeds.
3. Presentation of analytic findings from PEER testbed analyses in ways that would
be meaningful to relevant decision-makers.
PEER PBEE Relevant Decision Variables
The generic considerations that the PEER methodology should be addressing have been
identified through our research and discussions in evaluating the seismic performance of
a single facility are:
1. Life-safety calculated as deaths and serious injuries.
2. Functionality calculated as the amount of time (days, hours) that a given facility is
not functional [at a specified level of functionality].
3. Repairability calculated as the costs of repair of a given structure (and clean up of
contents).
4. Potential for financial ruin calculated on a facility specific basis relative to the
above considerations [Jack Meszaros to flesh out]
LSA Decision Variables [per Mary Comerio and Keith Porter]
Related to the above generic decision variables, the LSA test bed is considering:
1. Life-safety calculated as the potential ( based on likely damage states) for loss of
life or serious injury within a specified planning horizon.
2. Functionality calculated as the likely period of time that the lab functions would
be disrupted.
3. Repairability calculated as the costs of repair of a given structure (and clean up of
contents).
4. Potential for operational failure of the lab (i.e., equivalent to risk of ruin) within a
given planning horizon.
Van Nuys Decision Variables
1. Life-safety calculated as deaths and serious injuries.
2. Functionality calculated as the amount of time (days, hours) that the facility is not
functional [at a specified level of functionality].
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3. Repairability calculated as the costs of repair of thestructure (and clean up of
contents).
4. Potential for financial ruin calculated as the likelihood that the facility would be
put out of business [Jack Meszaros to flesh out]
From Evaluating a Single Facility to Making Seismic Retrofit Decisions
The PEER research being conducted by Ufuk Inces, with support from Eduardo Mirandes
and Jack Meszaros, is also considering for the Van Nuys test bed how the PBEE
methodology can be used to inform decisions about retrofit (based on different levels of
retrofit vs. no action). This has involved consideration of the ways to incorporate the
probabilistic information about sources and damage states into meaningful financial
decision terms. The issues have been:
(1) Relevant financial decision criteria (Internal Rate of Return, Net Present
Value, Payback Period) as they relate to costs and benefits of retrofits, and
(2) Presentation of results (annualized expected values vs. probability of
exceedance for specified values).
Ufuk is expanding the model to consider insurance as a choice to be explicity considered.
We talked about this as very useful next step in pushing the Van Nuys testbed that needs
to be developed in conjunction with next directions of the testbed.
Related issues that came up for this type of analysis were thinking about relevant
uncertainties for such calculations, beyond those inherent in the uncertainties associated
with calculating damage states. This draws attention to the need for sensitivity analyses
concerning discount rates and time horizons.
Presentation of PBEE Decision Considerations
We talked about the diverse audiences and differing needs of those audiences in
considering information about the seismic performance of a given structure. The issues
that have come up in the past concerning communication of PBEE results have revolved
around issues of communicating probabilistic findings (versus scenario as relates to
different earthquake sources and potential impacts) and communicating uncertainties of
analyses (relating to predictive uncertainties of PBEE modeling).
We thought it would be best to use the testbeds as opportunities to show the types of and
different ways in which predictions of seismic performance from the PBEE methodology
can be communicated. This should done for each testbed in consideration of who the
relevant audiences are for that testbed.
Van Nuys Testbed
Two generic audiences are recommended for consideration, each illustrating different
information needs and ability to comprehend information. One, labeled “owner,”
represents those that want the basic information about potential impacts but are not
tolerant of detailed information. The second, labeled “insurance and finance,” represents
the more sophisticated investor for which more detailed information is relevant.
Owner Presentation
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Two different ways of presenting PBEE evaluations are recommended for the
hypothetical owner based upon our discussions:
1. Owner Scenario – This is use of a “scenario earthquake” and the predicted impacts of
that event upon the facility.
a. Scenario chosen to be “modal event” in terms of risk profile [terminology
needs to be refined to provide an appropriate labeling of this event]. The
modal event is defined as the event with magnitude (M) and distance (R)
causing the greatest density of loss, DV. Mathematically, this would be (M,
R) such that d^2DV/(dM*dR) is maximized, for a scalar DV that reflects the
loss given an event in (M±dM/2, R±dR/2), and the probability of the event in
(M±dM/2, R±dR/2). On an x,y,z surface of where z = DV density, x = M and
y = R, the modal earthquake (M,R) would correspond to the highest point on
the surface.
b. For this event, results would be communicated as the expected value (“likely
outcome”) and 90th percentile (“credible worst case” – terminology to be
refined) for:
i. Loss of life
ii. Injuries
iii. Number hours/days of downtime for facility functioning
iv. Costs of repair
c. Separately, it is useful to consider how expected impacts contribute to the
likelihood of “the risk of ruin,” in this case meaning that the hotel would go
out of business.
d. We did not resolve how to convey the level of ambiguity (or for that matter
how to calculate it) associated with uncertainties of the projected scenario
impacts.
2. Owner Multi-Source – This incorporates the multiple potential sources of earthquakes
and their potential effects into a probabilistic like PEER framework. However, the
key difference for this is that a fixed period of time is chosen (the owner planning
horizon) and calculations are presented relative to that time horizon.
a. Planning horizon chose to 20 years, based on an assumption that is represents
the remaining useful life of the building. [An argument could be made for a
5-year horizon as perhaps reflecting the time horizon of an investor, but we
thought that would bias the results too much.]
b. For this planning horizon, results would be communicated as the expected
value (“likely outcome”) and 90th percentile (“credible worst case” –
terminology to be refined) for impacts over the period:
i. Loss of life
ii. Injuries
iii. Number hours/days of downtime for facility functioning
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iv. Costs of repair
c. Separately, it is useful to consider how expected impacts contribute to the
likelihood of “the risk of ruin,” in this case meaning that the hotel would go
out of business over the 20 year period.
d. As with the scenario-based approach, we did not resolve how to convey the
level of ambiguity (or for that matter how to calculate it) associated with
uncertainties of the projected scenario impacts.
Insurer/Investor Presentation
We also discussed two different ways of presenting PBEE evaluations for the
hypothetical insurer or investor:
1. PML-type presentation – This would be the basic equivalent of what insurers seek as
a PML type loss analysis.
a. Calculations based on the occurrence of shaking severity with 10% probability
of being exceeded in 50 years.
b. For this event, results would be communicated as 90th percentile (“credible
worst case” – terminology to be refined) for:
i. Loss of life
ii. Injuries
iii. Number hours/days of downtime for facility functioning
iv. Costs of repair
c. How do uncertainties get communicated for this case? [Jack, Ufuk, others?]
2. Probability-based presentation – This would be a fuller analysis and presentation that
reflects to probabilistic aspects
a. Calculations based on probability distributions of events and impacts,
covering the range of possibilities and their likelihoods
b. Results communicated as both (a) annual expected value, and (b) exceedance
probabilities (with probability yet to be selected – Ufuk??) with respect to:
v. Loss of life
vi. Injuries
vii. Number hours/days of downtime for facility functioning
viii. Costs of repair
d. “Risk of ruin” to be calculated on probabilistic basis – [Jack, Ufuk – how
calculate and how present this?]
e. Uncertainties to be presented as some form of level of confidence or
confidence interval.
Cross-Cutting Testbed Issues
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Issues for Presentation of Results
These relate to the flexibility of the PBEE predictive modeling and the available data:
1. Ability to generate specific scenario-based results (i.e., for scenario event).
2. Ability to generate results for a specific time horizon (i.e. 20-year planning horizon).
3. Ability to calculate specific dv’s (e.g., loss of life, injuries, downtime etc.).
Other Issues
1. Selection of scenario event when presenting for scenario – we discuss this as the
modal event for the risk profile (which is not necessarily the modal event itself).
What is this event called? [see above for calculation]
2. How to quantify life safety, which LSA so far as I understand it has not quantified
and VN desires to quantify. Can death and injuries be predicted?
3. How to quantify uncertainty (ambiguity) and communicate it to relevant audiences as
it relates to inherent unknowns.
4. How to incorporate concepts of “risk of ruin” into predicted impacts.
5. How to move the PBEE framework from an analysis of a single structure as is to an
analysis that considers retrofit options and insurance purchase options. This needs
more attention as to what the PEER direction is for the testbeds. Ufuk’s work takes
us a long ways to considering seismic rehabilitation/investment choices from a
financial perspective.;
6. Details, which are more than minor, of how the above calculations are made and by
whom.
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