huangyhg

probabilistic mce
aawk this new code! cbc2007/asce 7-05
the ibc/cbc section 1802.2.7 has an exception that allows a design in sdc d without a soils report if the peak ground acceleration of sds/2.5 is used and sds is determined per asce 7 section 21.2.1. this section refers to a probabilistic mce (2% in 50 yrs). looking on the usgs seismic hazard map web site,
you mean "seismic site class" instead of sdc (seismic design catagory)?
sms=ssxfa
sm1=s1xfv
sds=sms x 2/3
s1=sm1 x 2/3
also, pga is not necessarily the "max value"
there's other threads on the topic under "seismology engineering" probably "geotechnical engineering other topics". do a search...
check your equation for cs, again.
thank you both for taking the time to address this tedious issue.
to msucog: thank you for your direction - i guess i should have posted this in the geotech section.
i did mean sdc=d. starting with an assumed site class d, i end up in sdc=d which per ibc/cbc 1802.2.7 requires a soils investigation except if pga=sds/2.5 is used.
to galambos: yes, my formula for cs contains 2.5 in the denominator. this is precisely my point (or dilemma). how is pga=sds/2.5 to be applied? it seems convoluted to me that using the provisions to side step the soils report would result in a lower base shear.
there is nothing in the acse 7-05 commentary on this provision. i've searched google books for comments and found nothing. perhaps i can try another angle and contact someone in my seaoc chapter who was on the asce seismic task committee.
-alanna

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