equivalent axial load method 13th edition

[jgeng]

I am trying to follow a design example for beam columns. They select a trial size by the equivalent axial load method. I am looking in the 13th ed of aisc and I can't find any reference to this method. Was this method taken out? can someone confirm this? I will look for my lrfd 2nd ed...

 

[ishvaaag]

I made a quite complete port of LRFD 2nd edtion to Mathcad and (not surprisingly) no mention was made that I remember to predimensioning in any way. Predimension something is something that can be more or less accurate depending to the restrictions to the cases and ability of who states the method, so if not having a particular preference or imposition, just design the thing as per the code and that's it.

This is not as difficult today when one has so vast range of programs dimensioning precisely structures as a whole, and spreadsheets aimed to component members as well, as you can find and free at the steeltools website.

On the other hand, it can be that after much repetition work a contractor or a designer's team needs to make an appraisal of some kind of work at which they are expert; then why not use their method of predimension, since except through checks you can't either deny or confirm their approach, and they will be pleased to make a good guess as much as wanting to absorb their error, that will be theirs, and not yours.