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RE: IBC 1617.1.1 D=?

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Note that the definition of E is "the combined effect of horizontal and
vertical earthquake-induced forces."  Each term of Eq. 16-28 is capable of
inducing both vertical and horizontal forces in the members, depending on
the structural system.

D is not the dead load; it is the EFFECT of the dead load.  It is not
necessarily a vertical load.  For example, the dead load on a moment frame
will cause horizontal loads in the columns as well as moments in the beams
and columns.

Similarly Q-sub-E is not the horizontal seismic force; it is the EFFECT of
the horizontal seismic force.  It is not necessarily a horizontal load.
For example, the horizontal earthquake force in a braced frame will cause
axial forces with vertical components in the bracing, and vertical forces
at the column bases.

The point is that you can't just think in terms of applied forces, you need
to consider the EFFECT that the design seismic loads have on the members of
the structural system.  That is why the terms are defined as they are.

Rick Drake, SE
Fluor Daniel, Aliso Viejo, CA


                    "Haan, Scott M."                                                                                 
                    <HaanSM@ci.anchor      To:     "'seaint(--nospam--at)'" <seaint(--nospam--at)>                         
                    03/18/02 02:48 PM      cc:                                                                       
                    Please respond to                                                                                
                    seaint                 Subject:     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)

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