Unified LRFD/ASD AISC Manual

[bjb]

I exchanged emails with AISC the other day about why they did not include W8's in the beam and column selection tables in the third edition LRFD manual. The email is as follows:

A good question. The elimination of W8 and smaller beams in the 3rd edition LRFD Design Manual occurred because smaller beams often result in geometric (clearance) and constructability problems with connections.

The AISC Manual Committee deliberated on this quite a bit. It was decided that W8 and smaller members would be dropped from the manual. However, this does not mean you cannot use them. It just means we did not provide tabulated values for those sizes.

This caused a lot of people to complain about the missing tables. Like you, many designers are involved in single-story and light-weight structures that utilize these smaller wide-flange shapes. AISC is considering bringing these sizes back in the upcoming Unified Manual, slated for release in November of 2005.


If you want the W8's back in the upcoming steel manual, I suggest you email AISC and tell them you hope they bring them back. Most of my work is in lowrise relatively light weight structures and W8 columns are very common sections. I have not experienced clearance problems with these sections.

 

[HgTX]

How frowned-upon is crossposting on Eng-Tips? I'm wondering if maybe this should go to the AISC forum (forum172). (Red-flag this post if I'm speaking heresy.)

Hg

 

[bjb]

You're right, that forum would be a good place for this posting, but I think this forum gets more traffic, and it is a structural issue.

 

[apetr26542]

I have the new LRFD third and I can't stand those tables, they also took away alot of the smaller beams and channels from the beam load tables, and since they are LRFD the deflection is not published. I learned LRFD in college but I honestly cannot stand it. I don't have the time to design every member with painstakeingly long equations.

I ended up ripping out the beam load tables from my 9th edition manual and stapleing it together, I mean I know how to design a beam for god's sake. I just don't want to reinvent the wheel for every new structure.

Believe me, I can go on and on about LRFD.

 

[UcfSE]

My my, it isn't THAT hard to use LRFD lol. I would have just kept the 9th next the the 3rd, as I do now. The 3rd Ed is missing things just so you don't have to buy 2 books everytime the thing comes out. Since the 4th will now include ASD and LRFD, superseding previous editions including the 9th, how long do you think it will take for the adjustments to the new procedure to be made? Looking at draft copies of the 4th, the new ASD procedure will be similar in nature to that of the AISI code: find Mn for instance, then use resistance factor for LRFD or factor of safety for ASD. The equations look like the same or almost the same as those in the 3rd LRFD manual. That's a big change from the old 9th procedure.

 

[apetr26542]

LOL, I'm trying to come back to it after 8 years. When I first started out as an Engineer, the more "experienced engineers" couldn't relate to me with Mn and phiPu. They would always ask me what my "working stresses" were. I didn't know what the working stresses were because I was using Factored loads. Oh well, I don't know if ASD will ever go away, I suppose on jobs where I have "time" I can give LRFD more of a shot. I think I need another LRFD refresher.

 

[UcfSE]

I know exactly what you mean. When I first graduated I had never heard of ASD and my first boss would not allow LRFD because he didn't know it. So, back to the books. I've moved on from that place but even now if I say Mn or phi*Mn they don't get it. Sigh... what can you do?

 

[bjb]

I just want to encourage everyone to email AISC and let them know what your concerns are for the new manual. I for one was very unhappy that they removed W8's from the beam and column tables. I typically deisgn with the 9th Edition ASD Manual, but the writing is on the wall for that form of ASD. From what I have seen, the new allowable stress will have more in common with LRFD than the 9th. edition ASD. At some point the IBC will probably stop referencing the 9th edition ASD, and we will have to live with the latest and greatest from AISC.

I learned LRFD in college too, but when I got out my boss (and everyone else I ran into) was using ASD, so I taught myself ASD, which wasn't that hard. I think the 2nd. and 3rd. edition LRFD Manuals are too close to being text books instead of design manuals.

 

[apetr26542]

The problem I have with LRFD is having to convert from factored loads to service loads, it gets to be an extra step I find that I don't have the ambition to keep on doing throughout a job.