Cs min

[fasboater]

I was working a design example from the 2006 IBC structural/seismic design manual (3) and working through the example I needed to check Cs min for seismic.

My issue with this is, the example is based on 2005 ASCE and ASCE 7-05 gives Cs min as 0.01. In the example it states that Cs min .044(SDS)(I) as in ASCE 7-02. I obviously have an issue and I believe the 2006 IBC structural/seismic design manual (3) is where the problem is, although the Cs min of 0.01 seems very small.


Where does the empirical number of 0.01 for Cs come from?

Thanks

 

[DaveAtkins]

I believe that is for Seismic Design Category A.

DaveAtkins

 

[cessna98j]

Not sure of where the emperical .01 value came from. However, at a recent IBC 2006 seismic design seminar, a speaker with the earthquake engineering committee stated that there was an emergency change in progress to eliminate the .01 value and go back to Cs min = .044 Sds (I). Not sure about other states, but this was to be reflected in the Washington State amendments although I have yet to see this change.

 

[WillisV]

1. The seismic design manual is full of errors - this is one of them.

2. Cs min is 0.01 in ASCE7-05, but cessna98j is correct that the older 0.044SdsI equation was recently re-instated per supplement no. 2 of ASCE7-05 which can be found here:

http://content.seinstitute.org/files/pdf/SupplementNo2ofthe2005EditionofASCE7.pdf

So, the mistake in the seismic design manual actually ended up being correct by complete chance...

 

[fasboater]

Thanks all

 

[JAE]

WillisV,

Where do you find Supplement No. 1?

I assume there is one.

 

[WillisV]

You've already got it - look in the top right corner of your copy of ASCE 7-05 and you will see it has "Including Supplement No. 1" written there.

 

[JAE]

thank you