## notional loads direct analysis method

## notional loads direct analysis method

(OP)

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

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

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)

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

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

so what I will do in ASD combination with notional load will be as follow

(DL+LL+1.6*(0.002*(DL+LL))...is 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

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.

Note:

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

thanks a lot joshplum