1. Project 17 Report to Provisions Update Committee April 12, 2017
Ronald O. Hamburger, SE
Project 17 Chair

2. Project Goal Work jointly with USGS
Review present basis for development of design value maps
Evaluate issues
Recommend improvement and an updated basis for development of maps suitable for adoption into the 2020 NEHRP Provisions, ASCE and IBC 2024

3. Key Work Areas
Update site class definitions (add more) to better align with modern ground motion prediction equations
Re-evaluate risk basis for maps
Attempt to provide stability in mapped ground motions and their effects on design

4. Fa & Fv and Design Response Spectra
Issue resolved
Eliminate Fa and Fv site coefficients from the Provisions
Site class effects (as well as basin effects, where possible) will be directly included in the hazard analysis
USGS will publish spectral acceleration values for:
Multiple site classes
Multiple natural periods (0.01,…., 5 or 10 sec)

5. Re-evaluate Risk Basis for Maps
Options-
Stay with Risk Targeted MCER (1% collapse in 50 years) and deterministic caps (ASCE 7-10 & 7-16)
Revert to Uniform Hazard MCE (2% exceedance probability in 50 years) w/ deterministic caps (ASCE 7-05)
Revert to Uniform Hazard with lower return period (~1,000 years) & eliminate deterministic caps (new)
Resolution
None yet but slight preference for #1 followed by #3

6. Provide stability in mapped values
Stability in ground-motion maps from code cycle to cycle not as important as stability in Seismic Design Categories (SDC)
Currently being studied by NEHRP PUC (IT-01)
The number of SDCs (currently 4 SDCs)
The things SDCs determine
The triggering ground motion levels for each
Resolution
Go to separate SDC Map, computed for a “conservative” default site class in each region
Eliminate ability to adjust SDC based on site class