huangyhg

2006 ibc conc. load factors
1. did aci 318-05 change the live load factor from 1.7 to 1.6?
2. when designing reinf. concrete retaining walls for a seismic load, e, in addition to the lateral soil loads does the e get a load factor? since e comes from asce 7-05 and is a strength level load it seems to be overkill to tack on a load factor.
i suspect that the commentary of chapter 9 of aci 318-05 answers this question. i only have aci 318-99.
thanks for your thinking on this subject.
with 05, you have different load factors which are now consistent with asce7 and with aisc. also - and very important, the φ factors have changed as well.
so no more 1.4d and 1.7l....now 1.2d + 1.6l
1) technically, the change was made in aci 318-02. note that the strength reduction factor, phi, also changed appropriately. there's an appendix c that still has the old load factors and phi factors.
2) i don't have aci with me at home, but i'm used to putting a 1.1 factor on seismic loads. as far as that being an overkill, i'll leave that to some of my california brethern to answer.
jedc - not sure where you got the 1.1 factor on e. i always use 1.0.
jae & jedclampett,
thanks for the update. i have noticed that at least since the 97 ubc that the strength design & lrfd factors were 1.2d + 1.6l but the aci 318-99 was still 1.4d +1.7l. i guess that it makes sense to "effect alignment" between ibc, asce 7, aci & aisc.
jae,
i think that the 1.1e was called for in paragraph 9.2.3 of the aci 318-99 & i don't know what happened to this in aci 318-05.
oldpapermaker
please also note that to officially use the new load factors and resistance factors, you have to perform a compatibility analysis, not the old balanced reinforcing analysis. the determination of whether a member is compression or tension controlled will affect your choice of factors.

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