Beam Web Stiffener Locations

[eit09]

I’m currently checking a Wide flange for required stiffeners per 13th Ed sect J10. I have attached a sketch of the current web stiffener layout. Usually I place the web stiffener directly under the load but in this case the load is split between the two angles and instead of placing a stiffener under each angle I placed it in-between the loaded angles. Is there any where in the code or design references concerning stiffener placement?

 

[trainguy]

eit09,

How is this beam loaded?

tg

 

[eit09]

There is a 2" pin that runs between each pair of angles loaded by a single plate bearing on the pin.

 

[msquared48]

Placement looks good to me considering the need to have an easy installation of the bolts, plus the short gap between the angles for the flange to span, which should be no problem.

No worries here.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[csd72]

Two things that need to be checked for this type of connection:

1. the bending capacity of the flanges to take the eccentric load
2. the capacity of the welds to take the stress concentrations at the stiffer areas of support.

 

[eit09]

csd72,

The load is pretty much centered on the web so I don't believe your #1 statement would apply unless I misunderstand.

 

[dhengr]

Eit09:
I don’t mean to hurt feelings, but rather to suggest or make you think. I think there are many things wrong with your detail, the least of which are the exact locations of the 3/8" web stiffener plates. Is this little structure loaded in tension (lifting bm.) or compression (gravity load support), are there any lateral loads at the upper pin, you need to give much more info. about how it is used and loaded, as Trainguy suggests. I don’t have a copy of AISC, 13th Ed. Sect. J10, it’s certainly a good general guide regarding web stiffeners on std. structural members, but not the final word on your kind of structural system and its details. These little structures are not cook book problems, they require more engineering judgement and imagination, and finding a clear load path, understand how the structure really acts, not just following the formulas of today’s codes. This is a pretty expensive little fabrication to do the way you have it detailed, and will be tough to do properly. And the load path from the top pins to the bottom bolts looks awful complicated to me.

What are loads, magnitude and direction, what dimensions are critical, controlled by what? 8x6x1" angles and 2" pins suggest a fairly heavy load, but then how do you attach the angles practically to an 8x7/16" bm. flg.? Can you get a good weld at their heel in the 2.5" spacing btwn. them? Don’t you get a hard spot (very high weld stress) right under the pin holes, where this weld crosses the web of the beam, particularly if in tension? What are the little triangular stiffeners on the end of the angles for? You don’t want the fab’er. to have to fit them to the angle radius (corner clips), and how do you weld them to the angles? You need two 1" pls. and a 2" pin, then these loads pass through a 7/16" web and 3/8" stiff. pls.? The same problems exist with the 3/8" stiff. pls. in question, fitting to bm. radius and exactly btwn. flgs. in height. These stiff. pls. and their welds to the flg. will be very highly stressed at the edge of the bm. flg., by the loads in the 1" bot. pl., not a good detail, (again, particularly if in tension, and we shouldn’t have to guess this when you ask your question, thus Csd72's questions) . Is the 18x18x1" bot. pl. a base pl., bearing pl. or loaded in tension? What does the W8 really do except get in the way of aa good clean load path?

Give us more details, not one at a time, and don’t make us work so hard to be helpful. Answer the above questions, I have a few ideas. Why not make this whole thing out of 1" pl. with a 3" pipe spacer 33.5" long btwn. the inner pin pls.?

 

[eit09]

dhengr,

Sorry for the misunderstanding I should of stated my question more clearly. I was initially just looking for a reference or guide if there is one out there on stiffener placement. The max tension load is only about 9kips while the compression load is around 41k. The shear load parallel with the beam web is about 9k and perpendicular is 19k. Again thanks for your input I am goin to take a look at the details and also figure out what you mean by 3" pipe spacers.

 

[dhengr]

Eit09:
Being short of meaningful loads and other info., I look and think pretty big loads with 2" dia. pin and 1" side pls., has he checked pin bearing stresses, and what sets the 2.5" spacing, he can’t get btwn. the angles to do a good weld to the WF. The W8 looks like a spacer (4' centers) to me, a 3" pipe 43.5" long (sorry about the 33.5" typo) with 1" side pls. (pin pls.) and 2.5" spaces would give us 48" centers. But, he’s trying to take his large loads from 1" side pls. through a skimpy WF flg. and web, which don’t line up nicely with the loads in the side pls., then needs light web stiff. pls. too, which just complicate the fab’ing., all to get the loads to the brg. pls. The fab’er. will tear his hair out; three different pl. thicknesses, an angle size we may not have in stock, and a short length of W8, do we have any crops that size, or do we have to cut that out of a 40' er. All this comes from different locations in their warehouse and must be restocked. Also, note that without the loads and their directions, we were left to guess at whether this was acting primarily in tension (lifting bm.) or compression as you now indicate; two very different design problems. Simple, clean design and details, even at the cost of a few pounds of mat’ls. almost always saves you time and money in the shop and field, and usually in calcs. too.

Can we assume that the loads you give are evenly divided btwn. the two sets of pin plates, you gotta say that or again, you are leaving out a big complication? That is: 4.5k up; 20.5k down; and 19k/2 = 9.5k applied at the centerline of the 2" pin and parallel to the plane of the pin pls.; to each pair of pin pls.? The 9k lateral load, parallel to the axis of the 2" pins and applied at their centerline; I would make each set of side plates carry because of tolerancing issues btwn. your support structure and the equip. above. By the way what does their pin connection detail look like? Is the 13" high pin axis critical or just 8+5"? Is the 18" sq. base pl. size critical and the 12x12 bolt pattern? More when you chew on this, and provide answers.

 

[trainguy]

One original post, and 8 responses, and still no free-body diagram.

eit09, if you want useful help, you have to send a free-body diagram, or stop wasting our time.

dhengr - your patience is very impressive...

tg

 

[eit09]

Sorry Guys! Is there a way to Withdraw this thread?

 

[csd72]

No, it will be in cyberspace for eternity!

You could try redflagging it yourself, or you could give the information requested.

 

[dhengr]

Eit09:
Damit! Don’t quit now, after the time we’ve spent; read my posts again, think about them, word for word, draw some sketches that they suggest, and answer the questions, for yourself if no one else, they must be answered to do this design properly. You should be getting this kind of help from your boss or a senior engineer in house, a mentor who you can work with, grow to trust, learn from and develop a working relationship with. Do you have access to those experienced people at your work, if not say so, so at least we know where to start. Your original question was a simple one, but it was the wrong one, because of an over complicated design and design thinking process. Again, look for clean and simple in your design, direct load path, etc. Google, Rube Goldberg, what he does is funny and fun, but all too true in many cases. Simple, clean design isn’t always simple, it just looks that way when your are done; and thus, sometimes you don’t get the same credit, from the inexperienced people, as the guy who came up with the complicated solution. His must be better, it looks so complex and difficult, has so many parts, etc.; but his almost always costs more and has many more details that can go wrong.

Now, read my posts again, answer all the questions, and give us another post here, don’t quit now. I’m sure this little structure is not the most complicated design problem you have worked on, but it is really a good one on which to hone your design thinking and approach. A good one on which to let engineering judgement, intuition, feel for how a structure really works, come into play, rather than following the ever thicker, more complex, cook books and recipes that we call codes and hope cover every condition, so we don’t really have to think any more, just follow the recipe, pug in numbers and grind.

 

[trainguy]

eit09,

Now I feel bad...

FYI, the reason I kept asking for the Free-body diagram was to evaluate if the standards that you refer to are applicable, as well as to provide advice.

Standards which dictate stiffener location (or anything else) are very specifically tuned to the provision and integrity of load path.

As far as removing your post from the site, don't bother, because I believe it has already been forwarded to your Facebook and Twitter accounts, with a copy to your boss.
(just kidding...)

tg

 

[eit09]

Ok I have limited access while in training but I will provide all the information requested in the previous posts when im out.

 

[dhengr]

These forums are fun, but a horribly inefficient way to have a very deep and meaningful exchange of info. and thinking process. The reason we want sketches and free body diagrams is because they cover thousands of words (saved typing), if they show all the critical info. required to solve the design problem. The thing that busts my hump here, and this is not directed specifically at you Eit09, it’s just my daily rant, is that most of the questions are asked in a ‘twitter fashion,’ and the people who are trying to help are left to waste their time and effort trying to guess at what the OP’er really wants, or what the loads and their directions are. And, this makes a hell of a difference in the response one should give. I’m not trying to be a smart ass, know-it-all, or to make life difficult for anyone, but with this little structure as an example; does it act in tension or compression, makes a great difference in anything I would say about it. Without any other info. but the first sketch, I see 1" side plates (angles) and then, grudgingly later, 2" dia. pins, but no other useful info., I think pretty big loads; and then thin flanges and webs and stiffeners, a load path that looks like a maze, all to use rolled shapes; and I immediately think there is a bigger issue here than locating a stiff. pl. on a WF that probably shouldn’t be there in the first place.

Some considerable share of the people who come here to Eng-Tips don’t understand their problem well enough to ask an intelligent question about it. And, I’d even be fine with that, if they would admit that situation, and their true experience level, so we at least knew at what level to answer their OP, and not waste our time with a detailed answer that they wouldn’t understand anyway. It does make me angry that some OP’ers pretend to be engineers or good technical people, when they so obviously are not by the nature of their question, then their argument at the answers they get or their sheer puffery. They should post on twitter, were they can hold their own, and the level of exchange isn’t over their heads or wasting any productive time. Csd72 & Traingy, I sure would like to have a beer with you two, I think we talk about the same language. Eit09 this is not a tirade against you, it just came up on your thread, you come along too, you’re buyin.

For what it’s worth, maybe nothing... My design..., and I’ve not run any numbers, that’s for you to do. 18x18x1" base pls.; 4 - 16x16x1" side pls., with the sides sloped up to a 4-5" rad. circular arc over the 2" dia. pin holes; a 3-4" x 43.5" long pipe spacer btwn. the inner side pls., up as close to the 2" pin hole as your upper equip. will allow, this could pierce and be welded from the outside to both side pls. if needed, and exact size is shop’s option if they have a good crop in this size range; a triangular stiff. pl. outside, the outer side pl., to take the 9k parallel to the pin axis; as a function of the tolerances on the equip. pin pls. from above (a big secret) I would see if I could adjust the 2.5" spacing btwn. pin pls. so that this force was always taken by the side pl. I want to react it; and, on second thought, as I type, maybe I want the inner side pls. to react this load and take it into the pipe and a light stiff. pl. btwn. the pipe and the base pls., forget the outside stiff. pl.

 

[a2mfk]

The real question is how to build a steel-plated soap box tall enough for Dave to shout his message loud enough for everyone to hear it. Just joking, I am with you. Dave, if you want to really go nuts, go to Yahoo help boards or something like that and read those maintenance or DIY questions. Literally, "Can I put this hot tub on my wood deck?" or "How do I fix this 12 ft tall concrete retaining wall?", you almost want to tell them to go for it and let Darwin take care of it.

So, Mr. EIT who graduated about a year ago, we see you are trying to learn here. I just turned 36 and dangit I remember being you like yesterday, and it was awesome, so enjoy it. Don't get me wrong, I am still learning here everyday. But like your statics or structures professor required, sketch up a FBD and put some loads on there, then sketch up your idea of how that may work, and tell us what the structure is for and what you want to accomplish. You'd be surprised at the quality responses, some with sketches most likely, that would follow. If that is some sort of spreader beam or lifting device, maybe an HSS section with no stiffeners, lots of axial and torsional rigidity, would have worked great. And don't leave us hanging now, too curious and too much time spent!

There are lots of PEs on the board whose billable rate is well over $100/hr, and by asking a question you are asking them to donate that time. So, since time is money, and you have no way of repaying anybody (unless you buy us that beer Dave is talking about, and I prefer steins of expensive stuff), just try to save us all as much time as possible. And I will follow my own advice the next time I post a question.

And we are not piling on, I just joined this list a couple of months ago and love it so far. But there are a lot of posters that don't bother to help themselves by providing basic info so we fully understand the problem, "informationally indeterminate structural problems"...

Like weirdo Tom Cruise said in Jerry Maguire (I had to google it), "Help me... help you.."

Good luck and hang in there!

Andrew Kester, PE
Florida

 

[slickdeals]

I really like the spirit of this thread. Kudos to dhengr.

Dhengr: If I may, (absolutely kidding here []), how come no one is posting sketches of their proposed solution, yet giving poor ol' EIT09 a hard time for not posting one?

I agree with all you guys, a sketch is always the easiest way to explain a problem. Sketching different views of a connection helps you comprehend the load path and by drawing the various elements, you end up tracing the load path yourself

 

[csd72]

slickdeals,

That is because we help those who help themselves (like some important being whos name I cannot put my finger on...)

dhengr,

ditto, if I wasnt on the other side of the pond I may have taken you up on that.

 

[eit09]

Thanks for all the comments from now on I will be more thorough on my postings!! Minus this thread eng-tips site is great! It has given me a lot of insight on approaching different situation/topics. There are several MVPs that I enjoy following on the threads that they chime in on (Their Knowledge is inspiring!). All that being said I have attached the sketch I should have originally posted. Following the provisions of J10 of the 13th Ed. I was able to show that placing the stiffeners between the 29k loads is sufficient (vs placing a stiffner under each load). No need to spend any more time on this jumbled thread I just wanted to close the thread letting you all know your posting weren’t a complete waste of time.

On a side note if you’re being billed @ $100+/hour you boys are buying :-D