huangyhg

seismic calculations per asce 7-05
we build mostly r1 and r2 for the new england area and therefore aren't usually concerned about seismic calculations, but now i have a daycare center going into massachusetts. i'm trying to correlate the mass. 780cmr code values with those obtained from asce 7-05. my question: in asce 7-05, equation 12.8-7, what is the definition of the upper limit of hn, the highest level? is it to the top of the roof ridge or is it to the uppermost diaphragm at which a seismic lateral force is to be applied? and is this the same height required for 780cmr, section 1612.5.1.2.1?
my take on this is that hn is taken to the center of mass of the highest diaphragm. in your case, a pitched roof, would be about mid height between eave and ridge.
ssweetland,
thanks for your reply.
are you familiar with 780cmr? my thinking is that hn is to the highest connection of the vertical elements of the seismic resisting system to the diaphragms that comprise and transmit the inertial loads to those vertical elements. a lot of 780cmr looks like it was lifted directly from asce7, with some differences on percentage of snow load to be used, and they give values for effective peak velocity-related ground acceleration (av) and effective peak acceleration (aa) both equal to 0.12g. are these the same quantities as ss and s1 used in asce7?
sorry, not familiar with 780cmr.

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