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Fwd: fema 178 Aa values

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        our firm is involved in some retrofit work in the Portland, OR area.
We are comparing upgrades requirements between UBC zone III and FEMA
FEMA base shear values are signifigantly lower than UBC. (approx 75% lower!!)

realizing FEMA 178 is for life safety only, and UBC has serviceability etc.,
built-in to
its values to some extent, i am still amazed at how 'lite' the FEMA forces

I read the FEMA 178/1992 seismic maps for Portland as  Aa=0.05 & Av=0.05

Do the geophysicist for 'fema' have that drastic of a different opinion
about the Portland area
seismicity than ICBO? - Or are is FEMA 178/1992 that much 'lighter'?

I would be interested to hear opinions/comments/experiences.


Tim Terich

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Richard Lewis, P.E.
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