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RE: IBC 1617.1.1 D=?

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Equation 16-28 and 16-29 say E=rho*Qe -+.2*Sds*D. E is the earthquake force to be used in load combinations. Qe is the effect from horizontal seismic  forces. .2*Sds*D is the vertical component of seismic force.  The dead load still needs to be used in code load combinations.
Alternative ASD load combinations:
(Eq 16-17)     D+L+S+E/1.4 =  D+L+S+[rho*Qe + -.2*Sds*D]/1.4
(Eq 16-19)     .9*D+E/1.4 =  .9*D+[rho*Qe + -.2*Sds*D]/1.4
-----Original Message-----
From: Raul Labbé [mailto:rlabbe(--nospam--at)]
Sent: Monday, March 18, 2002 8:26 PM
To: seaint(--nospam--at)
Subject: RE: IBC 1617.1.1 D=?

What is the rationale underlying this diminished portion of D to
take account for the vertical components of seismic force, regardless
the structural type, and regardless the seismic zone ( crustal or
subductive earthquakes ) ?
-----Mensaje original-----
De: Haan, Scott M. <HaanSM(--nospam--at)>
Para: 'seaint(--nospam--at)' <seaint(--nospam--at)>
Fecha: Lunes, 18 de Marzo de 2002 04:55 p.m.
Asunto: RE: IBC 1617.1.1 D=?

D=dead load.  The .2*Sds*D is the vertical component of seismic force.  The .2*Sds is supposed to be multiplied by the weight and the force is applied in the up-down direction.
 -----Original Message-----
From: Ken Peoples [mailto:kspeoples(--nospam--at)]
Sent: Monday, March 18, 2002 11:03 AM
To: Seaint
Subject: IBC 1617.1.1 D=?

I am trying to go through a design using the new IBC 2000 and I have a question regarding Equation 16-28 (page 357).  I thought I understood what they were doing until I read "D = The effect of dead load".  Is this correct or was it meant to be "The effective dead load"?  I guess it is a similar question for "QE = The effect of horizontal seismic forces".  If it is correct as written, I don't think I understand the formulas.
Thanks in advance for your help,
Kenneth S. Peoples, P. E.
Lehigh Valley Technical Associates
1584 Weaversville Road
Northampton, PA 18067-9039
Phone: (610) 262-6345
Fax: (610) 262-8188
e-mail: kpeoples(--nospam--at)