I am trying to figure out my governing load cases for the roof (joists, etc.) of a warehouse I am designing and am getting hung up on the E factor. I just graduated and was never required to determine E in school (it was always a given). I am working my way through the code and am getting hung up on my QE factor. I am stuck here because all of the other factors that I am using in my basic load cases are in units of psf. If I use V or Fp as the code suggests to determine QE, my units  are inconsistent (lb vs. psf). How do I translate these factors so I can use them to determine my governing basic load case for roof design?  

E and Qe are "effects" in load combinations.  In other words, for a given set of basic loads applied to the structure, each load case (such as dead, live, seismic) create effects in structural elements.

Effects are things like moment, shear, axial tension, etc.

So you obviously don't mix psf with lbs.  

You would calculate the applied force on each member (such as your joist) for each load case.  These in turn create various effects and you combine them per ASCE 7 in the given load combinations.

 

Thank you. I think that my head is getting in the way and that I am over-complicating things.  

sklev,
Here's a couple of older posts of similar topic:

thread507-237438: Seismic Load Effects

thread176-98527: ASCE 7-02 Seismic Load effects

thread487-121459: Seismic Load Effect E (IBC 2003)



 

I had seen thread507-237438: Seismic Load Effects but still didn't quite understand. What does the A represent?

Which "A" are you talking about?  I looked at the thread and didn't see it.

 

Sorry, I copied the wrong link.

thread176-98527: ASCE 7-02 Seismic Load effects

(A(dead) + A(live)) + rho x A(seismic) + (0.2)(SDS) x A(dead)

In that post I was using Axial (A) as an example of an effect.