Conveners: Nico Luco and Tom Jordan
Dates: April 3, 2013 (GMSV Workshop 08:00-15:00 | UGMS Meeting 15:00-17:00)
Location: SCEC Boardroom, USC, Los Angeles

BACKGROUND & OBJECTIVES: The SCEC Ground Motion Simulation Validation (GMSV) Technical Activity Group (TAG) focuses on developing and implementing, via collaboration between ground motion modelers and engineering users, testing/rating methodologies for the use of ground motion simulations in engineering applications.

The two main purposes of this small workshop are 1) to coordinate the 2013 GMSV TAG projects with their 2012 counterparts and other related SCEC projects, namely the Software Environment for Integrated Seismic Modeling (SEISM) project, the Broadband Platform Validation Project, and the Committee for Utilization of Ground Motion Simulations (UGMS); and 2) to discuss a plan for future GMSV TAG projects.

The workshop will be followed by a two-hour meeting of the aforementioned UGMS committee, chaired by C.B. Crouse. The UGMS is initiating a pilot study with the objective of using 3-D numerical simulations, together with traditional empirical approaches, to develop long period ground motion maps for Los Angeles. These maps eventually may be introduced in a future edition of the NEHRP seismic provisions. Consequently, the UGMS committee consists of both seismologists and structural engineers.

UGMS SUMMARY: The SCEC Committee for Utilization of Ground Motion Simulations (or "UGMS Committee") is tasked to develop long-period response spectral acceleration maps for Los Angeles region for inclusion in NEHRP and ASCE 7 Seismic Provisions and in Los Angeles City Building Code. The maps would be based on 3-D numerical ground-motion simulations, and ground motions computed using latest empirical ground-motion prediction equations from the PEER NGA project. This project is coordinated with (1) the SCEC Ground Motion Simulation Validation Technical Activity Group (GMSV-TAG), (2) other SCEC projects, such as CyberShake and UCERF, and (3) the USGS national seismic hazard mapping project.

Presentation slides may be downloaded by clicking the links following the title. PLEASE NOTE: Files are the author’s property. They may contain unpublished or preliminary information and should only be used while viewing the talk.

Wednesday, April 3, 2013

PARTICIPANTS

*Remote Participants
†UGMS Committee Members

Summary of Outcomes

• The validation efforts of the SEISM project can be thought of as development of validation "gauntlets" of ground motion simulation tests for 1) inelastic SDoF oscillators, 2) geotechnical systems, and 3) nonlinear MDoF buildings.
• All of the validation gauntlets will be developed and demonstrated using the simulated ground motion time series from the Broadband Platform Validation Project that will be available in June (2013). As explained in a bullet below, the validation gauntlets will be automated in order to facilitate tests of future/other ground motion simulations.
• The principal engineering applications for which the validation gauntlets will be developed are nonlinear response history analysis (NRHA) of MDoF buildings and nonlinear site response analysis (SRA) in building codes. Note that the Broadband Platform Validation Project is currently focused on the use of ground motion simulations in developing the median part of ground motion prediction equations for elastic spectral acceleration.
• In addition to SRA, parallel validation gauntlets for the use of simulated ground motions in geotechnical analysis of slope displacements and/or liquefaction might be developed.
• In addition to NRHA of buildings, a parallel validation gauntlet might be developed for NHRA of bridges.
• Mainly to compare against the results of the other validation gauntlets, a parallel gauntlet will also be developed for inelastic SDoF oscillator responses.
• The first of two types of tests in each validation gauntlet will compare the geotechnical or structural analysis responses to the simulated ground motions against those to recorded ground motions that have substantially similar response spectra (elastic or inelastic). This type of validation test will isolate any discrepancies between the simulated and recorded ground motions beyond those in response spectra. They can also serve as tests of the use of simulated ground motions from an archive/database for building code NRHA and SRA applications. Currently, recorded ground motions selected from a database and scaled/modified to approximately match a target elastic response spectrum are, for the most part, used in these applications.
• The second type of validation test in each gauntlet will compare against the geotechnical or structural analysis responses to recorded ground motions from corresponding historical earthquake and station locations. This type of test will convolve any discrepancies in the response spectra of the simulated and recorded ground motions with any discrepancies isolated in the preceding bullet. Note that for these validation tests the simulated ground motion time series from the Broadband Platform Validation Project, or their recorded counterparts, will need to be adjusted for the site profile at each station location.
• In the validation gauntlet for inelastic SDoF oscillator responses, a third test against existing ground motion prediction equations (e.g., Tothong & Cornell, 2006) will be included.
• As mentioned in a bullet above, the validation gauntlets will be automated in the Broadband Platform in order to facilitate tests of future ground motion simulations. Part of this automation will be the computation of the geotechnical and structural analysis responses, which will be accomplished via a user-friendly interface to the OpenSees (Open System for Earthquake Engineering Simulations) software framework. The OpenSees interface will also facilitate running other simulated ground motions (not necessarily from the Broadband Platform) through the developed validation gauntlets.