Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.


notional loads direct analysis method

notional loads direct analysis method

dear experts,
I want to ask about notional loads
first in direct analysis method according to AISC360-05 or AISC360-10 I have to used notional loads which equal 0.002 from gravity loads and apply it for each story level ,but there is condition in code where the ratio of maximum second-order drift to
maximum first-order drift (both determined for LRFD load combinations or 1.6
times ASD load combinations, equal to or less than (1.7 in aisc 360-10) &(1.5 in aisc 360-05)

my question is when I add the notional load to asd combination I must multiply the combinations with 1.6 or not
thx in advance

RE: notional loads direct analysis method

Yes, your notional loads would also be increased. The idea here is to amplify the second order effects (i.e. P-Delta) so that it is on the level with what you would get if you were using LRFD load combinations.

Just don't do it TWICE. Meaning, you do the following 1.6*(0.002*(DL+LL)), not 1.6*(0.002*1.6*(DL+LL)).

RE: notional loads direct analysis method

Joshplum, thanks a lot for your helpful reply
so what I will do in ASD combination with notional load will be as follow
(DL+LL+1.6*(0.002*(DL+LL)) this ok or not?

also i have another question
i always use ASD in my design but i don't know which will be more economic in our design ASD or LRFD ?
thanks in advance.

RE: notional loads direct analysis method

Actually, you have to factor up BOTH the gravity load and the lateral loads. So, it would be something like the following:

Gravity load = 1.6*(DL+LL)
Lateral / Notional Load = 1.6*0.002*(DL+LL)

Then your total results can get divided by 1.6.

If you're using an analysis program then check to see whether this is automatically accounted for. I can speak for others, but in RISA (the analysis company I work for), if you request a P-Delta analysis and your steel code check is set to AISC 13th or 14th editions, then the program will automatically handle the 1.6 factors internally. I would imagine that most of the other commercially successful programs would do basically the same thing.

RE: notional loads direct analysis method

I really appreciate your help
thanks a lot joshplum

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close