PLAN TO SELECT PEER INTENSITY MEASURE, 3RD DRAFT
Keith Porter 1/15/02
The intensity measure(s) (IMs) of PEER’s PBEE framing equation have yet to be defined. In the testbed
kickoff meeting, we stated the selection of the IM or IMs to be a goal of the year-5 research. This memo
presents a draft plan to achieve this objective. The plan will be revised or further detailed at or shortly
after the annual meeting on 1/17/02.

Procedure & schedule. The IM committee will shortlist IMs and prepare a reporting form on
1/17/02. Committee members will discuss IMs, EDPs, and a reporting form with researchers during
the 11 AM – 3 PM testbed breakout sessions at the 1/17/02 annual meeting, and finalize them in the
3-6 PM topic breakout session on IMs. Each loss modeler will be asked to calculate the efficiency and
sufficiency parameters (discussed below) for each short-listed candidate IM and each hazard level,
and report by August 1, 2002. Researchers are free to evaluate and report on any other IM of interest.
The IM committee will meet on August 15 to identify the IMs that best meet the selection criteria.

IM scenarios. Different IMs may be appropriate in different situations, depending on the number,
type, and size of structure under consideration, fault proximity, and potential for ground failure, as
shown in Table 1. The table will be completed at or shortly after the 1/17/02 annual meeting.
Table 1. IM scenarios
Structure
Peril
Testbeds
Building or
short bridge
Shaking
Van Nuys
Near-fault shaking
LSA
Long-span
bridge
Shaking
Humboldt
Near-fault shaking
I-880
Multiple
Shaking
Highway
Near-fault shaking
Highway, campus
Liquefaction
Humboldt?
Slope stability
Humboldt?
Any
Candidate IMs
Candidate EDPs

IM committee. The committee initially comprises the following people, who will participate in the
IM breakout discussion on 1/17/02: Cornell and Bray (who will lead the discussion), Stojadinovic,
Stewart, Somerville, Conte, Makris, and Abrahamson.

Candidate IMs. There are many candidate IMs, perhaps too many to ask modelers to consider all of
them. During the 2002 PEER annual meeting, we will finalize a short-list of IMs that the modelers
should evaluate. Candidate IMs proposed so far include the following, in no particular order.
1.
2.
3.
4.
5.
Spectral pseudoacceleration response at the small-amplitude fundamental period of the structure,
Sa(T1), or equivalently, spectral pseudovelocity response, Sv(T1), or spectral displacement
response, Sd(T1).
Peak ground displacement.
Significant peak ground acceleration (SPGA), by Sasani et al., ND.
IM by Cordova et al., 2000: Sa(T1)R, where R = Sa(2T1)/Sa(T1) and  = 0.5
Conte’s Vector 1: [Sa(T1), Feh=50], where Feh=50 has to do with strength required of a SDOF elasticperfectly-plastic (EPP) system to achieve 50 times the elastic strain energy at yield, normalized by
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3rd Draft IM Plan
Keith Porter, 1/15/02 P. 2 of 2
the strength required to remain elastic. (Conte will provide a detailed definition that will be
posted to the Yahoo groups by January 17, 2002).
6. Conte’s Vector 2: [Sa(T1), F=8, FNy,rev=25], where F=8 has to do with the strength required of an
SDOF EPP system to have displacement ductility demand of 8, normalized by the strength
required to remain elastic; and FNy,rev=25 has to do with the strength required of an SDOF EPP
system to produce 25 yield reversals, normalized by the strength required to remain elastic.
Again, a detailed definition of this vector will be posted by January 17, 2002.
7. IM1I&2E by Luco and Cornell 2001 (see ref. for definition)
8. A vector in development by Krawinkler: [Sa, pulse period, PGV]
9. A vector of elastic spectral displacements proposed by Hutchinson et al. (2001): ∆IM = {∆e, ∆µ1mean,
∆µ2mean}, where ∆e = Sd(Te), Te = elastic fundamental period of the structure, ∆µ1mean = mean elastic
Sd between Te and T1, ∆µ2mean = mean elastic Sd between Te and T2, and T1 and T2 are taken as
secant periods evaluated at ductility demand values µ1 and µ2, respectively, which are tentatively
proposed as 3.0 and 8.0. See Hutchinson et al. (2001, 2002) for further detail.
10. Arias intensity Ia.
11. Duration (e.g., bracketed duration with 0.05g threshold).
12. Floor spectra, presumably Sd by floor, which can be used to calculate Sv or Sa at floor levels.

IM reporting and evaluation criteria. Modelers will be asked to report each short-listed IM as well
as one or more output variable(s) of interest (EDPs yet to be determined) for each analysis performed,
using a standard table that is yet to be designed. The committee will identify IM(s) that produce the
minimum residual coefficient of variation on the output variable, conditioned on the occurrence of
50%/50 yr, 10%/50-year, and 2%/50 yr ground shaking. It will consider the use of different IMs for
different hazard levels and scenarios. It will examine the issue of sufficiency: i.e., whether the EDP is
independent of other parameters (e.g., magnitude, distance, and perhaps others), conditioned on IM.
This test determines whether a trend exists between the output variable and M, R, etc. See Luco and
Cornell (2001) for a discussion of sufficiency, or a text on linear regression for tests of the significance
of regression. The committee will also consider the practicality of evaluating the IMs’ seismic hazard.
References
Cordova, P.P., G.G. Deierlein, S.S.F. Mehanny, and C.A. Cornell, 2001, “Development of a two-parameter
seismic intensity measure and probabilistic assessment procedure,” 2nd U.S.-Japan Workshop on
Performance-Based Earthquake Engineering for Reinforced Concrete Building Structures 11–13 September
2000 in Sapporo, Japan (?), Pacific Earthquake Engineering Research Center, Richmond, CA, on file
at http://groups.yahoo.com/group/peertestbeds in the Files/References subdirectory
Hutchinson, T.C., R.W., Boulanger, and Y.H. Chai, 2002, “Displacement-based Intensity Measure (IM),”
http://groups.yahoo.com/group/peertestbeds in the Files/References subdirectory. This is a
summary of Hutchinson et al., 2001 (see below).
Hutchinson, T.C., Y.H., Chai, R.W. Boulanger, and I.M. Idriss, 2001, “Inelastic Seismic Response of
Extended Pile Shaft Supported Bridge Structures.” Paper submitted to Earthquake Spectra –
December 2001 – posted version at: http://gram.eng.uci.edu/~thutchin/Spectra2001Paper.pdf
Luco, N., and C.A. Cornell, 2001, “Structure-Specific Scalar Intensity Measures for Near-Source and
Ordinary Earthquake Ground Motions,” Submitted for Publication: Earthquake Spectra, April
2001, http://pitch.stanford.edu/rmsweb/RMS_Papers/pdf/nico/EQ_Spectra01.pdf
Sasani, M., A. Der Kiureghian, and V.V. Bertero, no date, “Seismic fragility of short period reinforced
concrete structural walls under near-source ground motions,” submitted to Structural Safety;
http://groups.yahoo.com/group/peertestbeds in the Files/References subdirectory.