FEMA-NIBS BSSC PROJECT 17 COMMITTEE
Burlingame, CA
July 18, 2016
Summary Minutes
Participants
Project 17 Committee
Ron Hamburger, Simpson Gumpertz & Heger (Chair)
Norm Abrahamson, University of California Berkeley (absent)
David Bonneville, Degenkolb Engineers
C.B. Crouse, AECOM
Dan Dolan, Washington State University
Julie Furr, Chad Stewart & Associates
Jim Harris, James Harris & Associates
John Heintz, Applied technology Council
William Holmes, Rutherford & Chekene
John Hooper, Magnusson Klemencic Associates (absent)
Charles Kircher, Charles Kircher & Associates
Robert Pekelnicky, Degenkolb Engineers
John Siu, City of Seattle, Washington
Jonathan Stewart, University of California Los Angeles
BSSC Members and Guests
Pete Carrato, Bechtel Corporation
Greg Soules, CB&I
Philip Caldwell, SE, ([email protected])
Jennifer Goupil, ASCE, P17AC chair (by telephone)
USGS
Nicolas Luco
Sanaz Rezaeian
NIST
Steve McCabe
Siamak Sattar
FEMA/NIST/NIBS
Mai Tong, FEMA
Michael Mahoney, FEMA
Andrew Herseth, FEMA
Robert Hanson, University of Michigan
Philip Schneider, NIBS/BSSC
JQ Yuan, NIBS/BSSC
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1. CALL TO ORDER:
Ron Hamburger started the meeting at 8:00 am, with introductions, a reading of the anti-trust
statement, and a review of the agenda (attachment 1).
Mai Tong welcomed everyone to the 2nd Project 17 meeting.
2. P17 VISION, GOALS AND SCHEDULE
Ron Hamburger presented a brief history of the effort to review the seismic design maps every
10 years, starting in 1997. Project 17 (P17) for the 2020 NEHRP Provisions kicked off in 2015.
Among many possible topics, four work groups were formed in the last meeting, addressing
acceptable risk, precision and uncertainty, multi-period spectra, and deterministic caps. Ron
stated P17 will develop rules for USGS to use in developing seismic maps, as well as develop
proposals to update the Provisions. P17 is expected to conclude its work by the end of 2017.
John Heintz updated the P17C on parallel ATC efforts and stated the ATC is working on the
duration issues, which is led by John Hooper. The study should conclude around the same time
as the P17C’s work.
3. WORK GROUP REPORTS
3.1 Acceptable Risk (Chair: Bob Pekelnicky)
Bob Pekelnicky updated P17C on the work from the Acceptable Risk Work Group (presentationattachment 2 and excel sheet-attachment 3). The main goal of the work group is to evaluate “. . .
the appropriate ground intensities to use in design to prevent a catastrophic event such as
Leninakan.” Two fundamental questions were discussed:
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Is there anywhere in the country where we are currently providing designs with an
unacceptable risk of collapse?
Is there anywhere in the country where our current ground motion intensities are
providing too much safety?
Bob presented a worksheet (prepared by Bob Pekelnicky and Nico Luco) providing the values of
ss and s1 and associated risk of collapse in 50 years for different scenarios. (note: the ss and s1
values on the spreadsheet are derived from the scenarios listed below, and the return period and
risk values are based on current hazard analysis).
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Current ASCE 7-16 MCER
2%/50 year using ASCE 7-16 ground motion information
Deterministic cap with and without the 1.5Fa/0.6Fv floor using ASCE 7-16 ground motion
information
The 5%/50 year using ASCE 7-16 ground motion information
ASCE 7-10 MCER
ASCE 7-05 MCE
ASCE 7-98 MCE
1976, 1994, and 1997 UBC values converted to equivalent Ss and S1
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The analysis demonstrates near uniform risk (around 2% in 50 years) with a 975-year return
period.
Charlie Kircher brought up the concept of “uniform protection.” The concept was explained in
an example comparing designs for Riverside and Memphis. Basically, these two places have
very similar ground motion, but Riverside has higher frequency of reoccurrence than for
Memphis, and consequently, a building in Riverside is designed for more recurrences of the
same event, and consequently a smaller probability of exceedance given the occurrence of an
event than a similar building in Memphis. Therefore, when the next big earthquake event
happens, the building in Riverside is less likely to experience higher than anticipated shaking
than a building in Memphis, and is more likely to perform adequately. A uniform protection
approach would provide the same probability of seeing excessive ground motion and failing, at
both sites.
The possibility of decoupling seismic design categories was discussed. It was noted that much of
the engineering community’s dissatisfaction with map instability is associated with changing
requirements associated with SDCs as map values go up and down.
3.2 Precision and Uncertainty (Chair: Dan Dolan)_attachment 3
The Work Group is trying to balance precision and uncertainty with the yo-yo effect of design
values. The main points discussed are summarized below:
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The number of significant figures used to portray mapped ground motions does not much
effect on the design acceleration (different cities),
The number of significant figures used to portray mapped ground motions does not have
much effect on the seismic design category.
Oscillation of mapped values (data from 34 cities by Nico Luco): Historically, the maps
have portrayed mean values, which oscillate as fault characterization and GMPEs evolve.
Nico proposed using the uncertainty distributions (plus minus 10% of the mean value) for
damping out the oscillation. The P17C suggested other options: (1) use the average value
over the past few cycles (and always recommend site-specific analysis), or (2) provide no
change for two cycles.
Treat design maps differently from science maps.
Uncertainty for soil factors is more significant than the uncertainty of the hazard function.
Triggers for moving from one seismic design category to the next.
Dan suggested looking at the fundamental question of the change in acceleration that will
significantly change the final design.
Hamburger suggested “averaged” mapped values from the past series of maps together
with those generated for the new series of maps as a way of “damping out the yo yo
effect.” Hamburger noted that if there is a constant trend in values at a location, either
upward or downward, this is understood as the effect of improved knowledge, however,
when a value goes up one cycle and down the next, it creates the impression that the
maps are not based on sound knowledge or theory. By averaging the mapped values over
a series of map editions, reversals in direction would be minimized and over the longer
term, confirmed knowledge and theory would be picked up.
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3.3 Deterministic Caps (Chair C.B. Crouse):
CB stated that for arriving at deterministic caps, there is a general method and concept to get
there, based on the disaggregation of the hazard, return period, and natural period.
Nico Luco stated that USGS has done some disaggreation in California (21 locations of 34
cities), at 0.2, 1, 4, and 5 sec; for different soil types, at the DC and DE boundaries; and, at return
periods, 475, 975, and 2475 years.
For going forward, this Work Group is dependent on the definition of acceptable risk, and
whether it is necessary to “cap” probabilistic motions.
3.4 Multi-period spectra (Chair: Charlie Kircher)
Charlie Kircher delivered the presentation shown in attachment 4. The main purpose of the Work
Group is to evaluate the use of multi-period spectra, as a supplement or replacement of the
present 3-parameter definition. Its main conclusions are summarized below by Charlie Kircher:
“In essence, WG recommendations rely on the USGS to develop multi-period spectra for all
possible site conditions and all U.S. regions and territories of interest (which appears to be
feasible). It is recommended that the simple 3-domain shape of the design response spectrum
(Figure 11.4-1) be retained, but based on values of Sms and Sm1 (derived from site-specific
multi-period spectra using the criteria of Section 21.4) that directly incorporate site effects,
eliminating the need for site coefficient tables (which the WG recommends be deleted). The
WG envisions that a web-based application will provide values of Sms and Sm1 for userdefined values of site location (lat/long) and site class of the site of interest. The WG also
recommends adding three new site classes to Table 20.3-1 (BC, CD and DE) to more
accurately define site effects (a short-coming of current site classes at longer periods).”
The availability and readability (and potential web-based application) of the USGS maps were
discussed during the meeting. At minimum, the raw data (Sds, Sd1, TL) should be available, and
USGS will potentially expand the number of site classes.
Recommendations by the Work Group are summarized below (page 30 of attachment 4):
(1) Chapter 11 (Section 11.4)
–Retain 3-domain definition of the Design Response Spectrum (Figure 11.4-1) defined by sitespecific values of SDS, SD1and TL (developed by USGS and provided via a web-based app)
–Delete site coefficient tables assuming values of SMS (SDS) and SM1 (SD1) developed by the
USGS include site (and spectrum shape) effects
–Revise site-specific ground motion procedures (Section 11.4.7) to be the same as those of
ASCE 7-10 (i.e., remove “band-aide”)
(2) Chapter 20 (Table 20.3-1)
–Revise definitions/criteria to include new site classes at boundaries
(3) Chapter 21 (Sections 21.2.2, Figure 21.2-1 and Section 21.3)
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–Revise Deterministic MCERfloor (Section 21.2.2 and Figure 21.2-1), if still required, to be
based on SMS/SM1
–Revise 80% lower-bound limit (Section 21.3) to be based on SDS/SD1(or multi-period design
spectrum)
(4) Chapter 22
–Provide mapped values of SDS and SD1for “default site” conditions only (provide all mapped
parameters/site conditions via a web-based app.)
In a straw vote (In favor 12, 0 oppose, 0 abstaining) the P17C endorsed the recommendations by
the Work Group. A formal proposal to guide map development will be developed within P17, as
well as the related design procedures. The actual proposal will be developed after the work of
other P17 work groups conclude.
4. P17 ADVISORY COMMITTEE (P17AC) INPUT
Jennifer Goupil (P17AC chair, by telephone) and Greg Soules and Philip Caldwell (present at the
meeting) presented the comments from the Advisory Group.
The P17AC has met twice since the last P17 meeting in March. The P17AC does not intend to
be a technical peer reviewer of P17 work; instead the AC would like to provide value by
collecting opinions or providing feedback based on the following questions:
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What is the role of the maps for the seismic engineer?
What do practitioners need from the maps versus the database?
What are the political or functional ramifications for the maps/database?
The P17C posed two questions to the AC that it could provide using additional feedback from a
larger user/stakeholder group:
Q: Would there be a benefit to ONE “zone” value for each jurisdiction? What are benefits
and challenges?
Q: How amenable do you think the design committee and jurisdictions would be to a
radical change from current format in how data is presented or what is based upon?
A detailed discussion of the comments from P17AC is provided in attachment 5 (by Jenifer
Goupil).
5. P17 AND IT1 COORDINATION:
David Bonneville updated the P17 on the PUC, where the nine ITs (Issue Teams), including
work scope and membership, will be finalized in a meeting on the following day PUC meeting.
IT1 will coordinate with P17 work.
The coordination between P17 and IT1 was discussed. During the last cycle, the PUC provided
inputs to Project 07 work, which did not actually work on the proposals. The P07 proposals
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were proved by the PUC. For the 2020 cycle, David commented that PUC members, who are
also P17 members, can bring proposals to the PUC. The P17C concluded that both the seismic
map related work and procedures-related proposals from Multi-Period Spectra Work Group
could be initiated from P17 and get dual-approval from both the P17C and PUC. Mai Tong
commented that there will be separate funding for the PUC and P17 for FY2017.
6. ADDITIONAL STUDIES
(1) System collapse based on FEMA P-695 – considered a very expensive study.
Based on the morning discussions, members suggested expanding the number of Seismic Design
Categories, and possibly the effects of duration. A new work group was formed with the
following members:
Chair: Julie Furr
Members: Bob Pekelnicky (to coordinate with IT1), Jim Harris, Bill Holmes, Jon Siu, Dan
Dolan, John Hooper, and Paul Timko (Ed. note: Paul was recommended by Julie later on).
(2) Irregularities based on FEMA P-695
John Heintz updated the Committee on the ATC 123 study on the impact of irregularities. The
first phase is about reinforced concrete shear wall and moment frames, which should be
completed by this September. The entire study is due to be completed in a year.
(3) collapse given MCE shaking, 10% vs 5%, for buildings designed at a minimum code level
Bob Pekelnicky will ask his group members to look at developing additional commentary for this
issue, but no action is needed at this point.
(4) Adoptability of the dramatic changes to ground motion by different parties.
The P17C will consider the issues of enforceability vs adoptability, how to justify; the ability of
engineers to follow the changes; and, the public reaction to changes. If the 1000-year event is
adopted as recommended by the P17C, it will be difficult to raise values afterward.
7. WRAPUP AND NEXT MEETING
Only the Acceptable Risk Work group will stage an in-person meeting before 9/28/16. The
Uncertainty vs. Precision Work Group will meet only by web meeting. (Ed. note: The group had
a meeting on 7/19/16 during the PUC meeting, with some members participating by telephone.)
Next P17 meeting will be in Burlingame on 11/29/16.
8. ADJOURNMENT
The meeting adjourned at 5:00 p.m.
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