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Re: SPAM-LOW: IBC 2003 Seismic

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Title: IBC 2003 Seismic
The vertical load effects are vector added to horizontal loads. In other words, you not only apply a horizontal force, you also apply a vertical force at the same time to account for Earth Quake vertical component.
This can be implemented simply by modifying your load combinations, so that instead of D+E as you would normally do, you end up doing something like 0.94D+E and 1.4D+E gets replaced by 1.46D+E
Syed Masroor
----- Original Message -----
Sent: Thursday, March 09, 2006 7:21 PM
Subject: SPAM-LOW: IBC 2003 Seismic

Any insight at all on this topic would be greatly appreciated! 

1. 1615.2.1 defines S(aM) as the maximum spectral response.  1615.2.4 defines S(aM) as the median spectral response.  Which is it?  Is there a relationship

between the S(a) given in the general section and the S(aM) given in the site specific section?

2. 1615.2.5 defines S(DS) and S(D1) in terms of S(a).  It?s my understanding that S(DS) and S(D1) would be used in the tables to pick a design category.

My question is: what is the purpose of the statement S(MS) and S(M1) shall be taken as 1.5 times S(DS) and S(D1) respectively?  In 1615.1.2 S(MS) and S(M1)

Are calculated and then multiplied by .667 to get S(DS) and S(D1).  The ?flow? seems to be, ?find S(MS) and S(M1) and then calculate S(DS) and S(D1)?, not the other

Way around.

3. 1617.1.1.1 talks about the effect of gravity and seismic being additive or counteracting on another.  Please explain how you add or subtract a horizontal load and a

vertical load.  Is there a simple example of what these equations are trying to convey?