Connection design using major detailing software?

[SteelPE]

I know this subject has been beat to death but here goes again.

Depending on how busy I am, I dabble helping fabricators out with their connection design woes. Every once in a while we will have a fabricator say "The detailing software will produce the calculations for the connections for us. Can you just review those designs to see if they are correct?". This always makes me cringe as the purpose of detailing software is not to design connections but rather detail the building. Also, when it comes to a project, I want to be out in front not playing from behind (telling them what to use for connections rather than having them dictate to me what they used). I know that one of the major detail software companies just recently linked with a famous engineering software provider to start designing their connections in their software.

Has anyone dealt with reviewing simple connections this way? I realize that the software would be capable of designing about 90% of the connections in a building..... and that the last 10% would need manual calculations due to their complexity.

 

[BAretired]

Standard connections are detailed in the CISC manual, so those don't really have to be checked. My practice was to review the standard connections for compliance without calculation and to do only the calculations for the 10% non standard connections.

BA

 

[SteelPE]

BA,

I like your method.... however some EOR's require that calculations be submitted on the connections (kind of a vague statement). I get the feeling that the EOR is basically having someone else take a good look the design of the connections so they can reduce the time it takes to do their shop drawing review. Some things are covered.... but not really in the AISC. Things like block shear on the beam web, bolt bearing on the beam web, bolt bearing on the column web, net shear on the beam web etc... are covered but require minor calculations.

I have always approached the EOR's statement as meaning every connection needs to be look at and calculations provided. We do the best can to group the connections into some standard types (W12, W14, W16 etc...) figure the worst loading condition for the group and design 1 connection. However in this instance the client is asking us to review calculations produced directly from the detailing software. I'm not sure if other people utilize the connection design performed by the detailing software.

 

[dhengr]

SteelPE:
So, what’s new? You are not the EOR, but have been asked to check their connection designs for conformance with the contract documents. Your liability should be different as a checker and sub-consultant than if you were the EOR, hopefully covered under the fab’ers. umbrella policy for the job. And, they are trying to save outside engineering costs by using the detailing software to do the calcs. on the easy 80-90% of the connections. That’s more or less what we’ve always done, the old std. AISC connection tables stored within the software or done for each new different connection, but complexified for the fun of it, per the latest codes and stds. Why those even need calcs. is beyond me, except plan reviewers and AHJ like to collect stacks of paper. They must all have stock in the paper mills or printer ink suppliers. The fab’er. will have/may have tweaked these calcs. a bit, to conform with their favorite details or way of doing things or to work with their fab’ing. equip. and methods. They want your engineering eye to check and see that the detailers have interpreted the EOR’s intentions correctly, what with all the load combinations, load factors, etc. Then, you also do the few connection details which really do require some serious engineering consideration. My approach was always the same as BS’s approach. You don’t get to cringe or be out front on these jobs, they’re not your plans, you’re just adding some engineering expertise to part of the job which has been foisted on the fab’er. by another engineer trying to save some time, or not knowing how to do it in the first place.

Once you’ve worked with a fab’er. or a detailer a couple times, the simple connection part should go pretty quickly because you know how they think, what they like, and how their software works. On the tougher 10% they need your engineering expertise, since the software sellers haven’t conquered that mountain yet. But, those are the fun details too, if the Arch. & Engr. haven’t made a mess of things. If you like this kind of work, and get in good with a half dozen fab’ers. this might be a more steady work flow than chasing small Architects and Contractors for individual jobs.

 

[SteelPE]

dhengr.

Interesting. The problems I have revolve around the fact that the EOR wants to see the connection calculations. I have approached my bids and prepared my calculations accordingly. I figured my liability coverage would come into play if necessary. A lot of the problems I deal with have to do with the EOR messing everything up. When they want 1/2 the uniform load capacity on a 10' long beam or when they want to frame a brace into a W10 beam and an HSS6x6x1/4 column with 250kips in the brace connection or when they want to develop the full moment capacity of a 21x68 which frames into a W12x58 column. I could go on and on.

I just don't seem comfortable sealing a bunch of calculations w/o going through them to make sure there were correct.

 

[dhengr]

BA:
Sorry about that..., in the fifth line up from the bottom in my first para. @ 17:58. BS is a completely different guy than you. I think the A & S keys on my keyboard must have switched places for one key stroke there.

SteelPE... I agree with you, that if you are signing off on all of the connections and their calcs., then you certainly better review them and be confident in their quality and accuracy. And, I can imagine that it is a real pain in the butt when the engineer designs something for which you can’t design a practical connection in less than two days; and all the more maddening when they don’t know the difference, and then argue with you about it. But, that is why the fab’er. needs you, to find those absurdities and fix them before they become serious problems. But, this does seem to be what we are doing to each other these days, in our business world. Why should I spend and hour and my fee, if I can ignore a potential problem, shove the responsibility off on someone else and save that work, and then bitch at them for calling me to task for my mediocre work and lack of real engineering knowledge and know-how. The attorneys and insurance companies seem to love it too, twice as many premiums and twice as many people to sue, and really no body in a position to assume primary responsibility.

 

[UcfSE]

I'm dealing with using detailing software to design connections. I'm finding it reasonable, for reasonable connections. The key I've found so far is understanding the capabilities of the software for what it can handle and what it will not do. For example, what we're using will provide all the calculations for a beam with a shear tab, but it will not calculate anything if that beam with shear tab has an axial load on the connection. I have to do those myself. The next key I've noted is make sure to input the actual loads if you have them. It seems to do brace connections pretty well, particularly if you have actual loads instead of using the brace tension capacity. The software retains the ability to calculate half the uniform load beam capacity, but that's too much in most cases for shear, not enough in others, and still ignores cases like axial loads. So you have to be careful with what it can do, and provide back up hand calculations or calculations in a connection software that can do what the detailing software cannot.

 

[SteelPE]

UcfSE

Are you using the program to design connections for your win projects or are you using the software because you are trying to design connections for a fabricator?

 

[connectegr]

The primary detailing software I see with connection design is SDS. The software does a very good job for most connections. However, the quality of the software is limited to the understanding of the detailer. +/- axial loaded or gravity/lateral moments are not something most detailers understand. Therefore, they can make incorrect inputs, that result in a "Connection OK" result. In most cases these calculations do not even consider important design concerns. But, the calculations and checked limit states all pass simple inspection. You must also look out for "Graphically Connection", which provide no calculations. All of these issue are only found with a thorough review of the mountains of paper generated by the software. And no indication or warning of potential issues are highlighted on the shop or erection drawings.

We have reviewed and sealed piles of SDS calculations at my customer's request.

1. The time required to adequately review the calculations, typically takes longer than providing my own connection details and calculations, which have been previously reviewed by hundreds of engineers.

2. We are ultimately accepting the same responsibility for the adequacy of the connection design and details, whether we seal the SDS calculations or our own. So there is no discount in our fee.

In most cases, I suggest that the detailer use our details and calculations. If they are using SDS, I suggest that the use the software to generate the connection and check the detail using the information we provide. In most cases these details should be very similar. And this avoids input errors by the detailer. When complete the shop drawings are submitted with our sealed calculations. If sealed shop drawings are required we review the shop drawings for conformance to our calculations. We save rainforests by never printing the volumes of SDS calculations.

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[UcfSE]

I'm using the software because I'm working for a firm trying to get into detailing, so we're producing shop drawings directly and skipping the construction drawings (we are the SEOR also). I can't convince my boss to buy proper connection engineering software so I'm doing what I can do by hand and with the detailing software. For what works its easier to have the detailing software design and detail the connection directly. For what it can't do I have to give the detailers direction on producing a graphical connection or otherwise modifying the detailing to that it is what it needs to be.