ASCE 7-05 Seismic Provision
ASCE 7-05 Seismic Provision
(OP)
I don't understand the thought process of splitting the seismic load effect "E" into two components (Eh and Ev). I have calculated the Eh and Ev components but am trying to grasp how to use them in the load combinations.
In my structure, I have assumed the Ev to be negative (uplift). No particular reason, just the way I chose to think about it. The Eh is also negative due to customer sign conventions. With all that said....
Section 12.4.2 states:
E = Eh + Ev in ASD load combinations 5 and 6
E = Eh - Ev in ASD load combination 8
In my case, looking at E = Eh + Ev. Do I add the two loads and then substitute the E into the load combination or should I use Eh and Ev in the load combination so that the result is additive? If I add the two loads, which direction is E applied.
Any help would be great.
Ryan
In my structure, I have assumed the Ev to be negative (uplift). No particular reason, just the way I chose to think about it. The Eh is also negative due to customer sign conventions. With all that said....
Section 12.4.2 states:
E = Eh + Ev in ASD load combinations 5 and 6
E = Eh - Ev in ASD load combination 8
In my case, looking at E = Eh + Ev. Do I add the two loads and then substitute the E into the load combination or should I use Eh and Ev in the load combination so that the result is additive? If I add the two loads, which direction is E applied.
Any help would be great.
Ryan






RE: ASCE 7-05 Seismic Provision
Dik
RE: ASCE 7-05 Seismic Provision
Check out these threads that discuss the vertical component effect from seismic:
thread176-98527
thread487-121459
RE: ASCE 7-05 Seismic Provision
You don't add the forces since they may have different vectors, you add the results of those forces.
Hope this clears it up.
RE: ASCE 7-05 Seismic Provision
Thanks for the information. I believe I understand it. Let me recap my thinking now.
Considering E = Eh + Ev:
load comb 5 - D + H + F + 0.7Eh + 0.7Ev
load comb 6 - D + H + F + 0.75(0.7Eh + 0.7Ev) + 0.75L + 0.75(Lr or S or R)
Considering E = Eh - Ev:
load comb 8 - 0.6D + 0.7Eh + H
In load combination 8, I wouldn't considered the load effects from the vertical seismic Ev.
Does this make sense?
Ryan
RE: ASCE 7-05 Seismic Provision