AISC Seismic Design Manual: eccentric weld groups

[hairpin]

So throughout this book they typically show you how to do a calc by hand and then show you a quick way to look up the same value in a table. But I'm having problems understanding some choices made for braced frame connections.

In Ex. 3.11, p. 3-72 and 73, the long calc shows 5/8" weld is needed. The boxed calc using eccentric weld group tables shows 3/8" weld is needed. 5/8" weld is chosen.

This continues throughout this example and also Ex. 3.10, p. 3-59 to 60, where long calc shows 1/2" weld is needed and the boxed calc shows 3/8" weld is needed. They actually chose the smaller size weld.

What is the point of doing these calcs if they don't match? From the book it seems they don't expect us to do both calcs and then chose the larger weld size. What gives?

Also where in the steel construction manual does it specify fr=1.25 favg for weld stresses. Makes sense. I just can't find it.

Help?

 

[Greenaqua]

I saw the same issue with the two different methods to calculate weld size. I don't know the answer to that but perhaps it is worth emailing AISC?

The location in the steel manual (13th edition) for the discussion of 1.25 avg stress is on page 13-11 under the section "Available Strength".

 

[hairpin]

I saw the same issue with the two different methods to calculate weld size. I don't know the answer to that but perhaps it is worth emailing AISC?The location in the steel manual (13th edition) for the discussion of 1.25 avg stress is on page 13-11 under the section "Available Strength".

I did submit this is a technical question to AISC. For my exam I'll probably just end up doing calcs without any tables if I don't get this issue resolved.

And thanks for page location on the avg stress.

 

[Greenaqua]

Let us know if you hear anything from AISC. I plan on doing hand calcs. also if it comes up on the exam but either way will probably be ok.

 

[hairpin]

Let us know if you hear anything from AISC. I plan on doing hand calcs. also if it comes up on the exam but either way will probably be ok.

So I emailed AISC and got a response which summed up is "either hand calc or from table is fine". But there was nothing there explaining the differences I got in calculations and why one hand calc would be less than the table and then in another calc the hand calc would be more than the table lookup.

I've found lots more errors along the way. So, I've promised myself I'm going to scan the sheets and send them the errors on the pages. Darnit, I paid $175 for this book and it has more errors than I like. And while it's still a great resource, I'm disappointed and think AISC could have done a better job.