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Steel Angle Bending/Splitting

Steel Angle Bending/Splitting

Steel Angle Bending/Splitting

(OP)
Hi all,

I'm reviewing some drawings from a steel manufacturer for some steel framing around a roof opening in a metal deck roof. The metal frame will rest on OWSJ's, and support the roof deck around the opening. What they've submitted doesn't match our details, but I do think it's a much easier construction, and could work in some situations. Our detail: https://files.engineering.com/getfile.aspx?folder=... Their drawing: https://files.engineering.com/getfile.aspx?folder=...

My main concern is the point where the flat steel angle portion meets the vertical web of the angle. The flat plate has enough bending capacity without the vertical, but what resistance does the member have to splitting where they join together. I think an easy fix is to simply add in a gusset plate where the vertical starts (or revert completely to our detail), but I think their detail is nice for constructability and I would like to use it in certain low load applications if I can prove it works.

What are your thoughts? Am I missing something, or is there a straightforward check I can complete? Typically when members like this are coped the shear resisting vertical web is what remains...

RE: Steel Angle Bending/Splitting

I'd be inclined to stick with your original detail. Things I don't like about the alternate:

1) Support reaction is irrevocably eccentric from the shear center of the angles. So torsion until you hit the rectifying cross members which is yucky to deal with analytically.

2) As you've surmised, at higher loads, shear and plate bending will overcome the capacity of the horizontal angle leg. Evaluating this is tricky as well because of the torsion mentioned in #1. How much of that leg is effective in resisting shear?

3) I'm surprised that this saves $$$. I've been under the impression that coping out the heel/fillet area to a flat plate is very expensive. Or maybe they are cutting that part away and leaving only a partial horizontal leg?

4) Hopefully you get paid too much to justify the time that you'll spend trying to save someone else a few pennies.

I agree that the alternate certainly would work for some range of loading. And I'm sure that we could dream up some, rational evaluation procedure if you really feel that it's worth the time to do so.

RE: Steel Angle Bending/Splitting

Is splitting really a thing? I generally see their detail in practice.

RE: Steel Angle Bending/Splitting

Quote (KootK)

heel/fillet area to a flat plate is very expensive
Would be quick in the shop with a plasma cutter and not too bad in the field with a 7" cut-off wheel. I imagine it is also a lot easier to erect.

RE: Steel Angle Bending/Splitting

Quote (XR250)

I imagine it is also a lot easier to erect.

Why?

Quote (XR250)

Would be quick in the shop with a plasma cutter and not too bad in the field with a 7" cut-off wheel.

Whenever I've tried to do similar things with other kinds of members, I seem to get spanked for it. Maybe the smallness of the angles alleviates that.

RE: Steel Angle Bending/Splitting

Quote (KootK)

Why?

In a retrofit, there could be more leeway in being able to slip the angles in with 6" of vertical leg removed.

RE: Steel Angle Bending/Splitting

Quote (XR250)

In a retrofit, there could be more leeway in being able to slip the angles in with 6" of vertical leg removed.

Oh come on... that's only 2" more than than would be "vertical angle free" with the mechanically better detail. In two decades of practicing, I can't say that I've ever encountered a situation where that would have mattered. If anything, it would be more about the vertical legs of the clips running the other way and I feel that the odds of those being deal breakers is equally remote.

RE: Steel Angle Bending/Splitting

(OP)
Thanks for the initial thoughts. I do think their detail is easier to fabricate, though not really any easier or harder to install (unless it's a retrofit like XR250 mentioned).

Quote (XR250)

Is splitting really a thing? I generally see their detail in practice.

I guess splitting isn't a technical term for the stresses at that location, but I do think that is a real experience for the member. There's a sharp change in stiffness properties and that would try to pull apart the horizontal and vertical legs at the extreme corner.

Quote (KootK)

4) Hopefully you get paid too much to justify the time that you'll spend trying to save someone else a few pennies.

Probably paid too much to spend a lot of time on one single job, but if I can improve the detailing on many jobs (and keep the steel guys happy) I believe that's good for business.

RE: Steel Angle Bending/Splitting

For light loading the proposed one is workable and likely less costly. The load capacity (reaction x the eccentricity of the reaction) is limited by the capacity of the leg thickness x the width of the angle. Your detail can accommodate loads and is limited the thickness of the supporting clip x the length of the supporting clip which can be 6" or 8" or more. Your approach is so common that I've written a couple of SMath programs because I encounter it so often. The programs stipulate the supporting eccentricity which I usually limit to 1" and also if the support angle if fully welded the support. One the support is pinned for the eccentricity and the other the support is fixed, which 'halfs' the eccentricity. I'll dig up a copy of the SMath and post it later... up to my neck in 'gators, currently.

One of the programs determines the max capacity of the L based on max UDL for section capacity... another of the programs does the same for a C Section.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

RE: Steel Angle Bending/Splitting

Quote (ryaneng)

I guess splitting isn't a technical term for the stresses at that location, but I do think that is a real experience for the member. There's a sharp change in stiffness properties and that would try to pull apart the horizontal and vertical legs at the extreme corner.

I got your drift even if "splitting" might not have been the best descriptor. Maybe "tearing" at a stress concertation that you sure hope is yielding rather than splitting. Your spot on with the basic mechanics of it though.

Quote (ryaneng)

Probably paid too much to spend a lot of time on one single job, but if I can improve the detailing on many jobs (and keep the steel guys happy) I believe that's good for business.

I don't see that making much of a business development impact unless the fabricator is actually is your client here or in the future. I can't see a contractor objecting to using you as the EOR for a new project just because a steel fabricator doesn't like that you insisted on doing what is commonly done on some dinky roof opening frames. Steel supply contracts are way to cost driven for that to be the case.

Quote (dik)

The load capacity (reaction x the eccentricity of the reaction) is limited by the capacity of the leg thickness x the width of the angle.

I suspect that it's really quite a bit worse than that. I'll check it out in the Smath.

Obviously, the fabricator preferred setup has some capacity and I'd be happy to use it for ceiling fans etc. That said, if I had it in my standard details, I'd worry that it would be just a matter of time before I found that setup under a moderately sized RTU. I'd need three versions:

1) Channels for the big stuff.

2) Angles without the clips for the truly little stuff.

3) Angles with the clips for the in between stuff.

That would be getting too fancy / error prone for my liking. If I were to have angles w/o clips on the roster, I'd need to be confident that the suitably replaced all instances of angles w/clips.

RE: Steel Angle Bending/Splitting

Quote (KootK)

Oh come on... that's only 2" more than than would be "vertical angle free" with the mechanically better detail. In two decades of practicing, I can't say that I've ever encountered a situation where that would have mattered. If anything, it would be more about the vertical legs of the clips running the other way and I feel that the odds of those being deal breakers is equally remote.

Looks like I got your panties in a wad :)

These are overhead welds (in retrofits) - which suck in general. I would argue without the vertical leg of your clip angle in the way, it is an easier weld.

RE: Steel Angle Bending/Splitting

KootK... what I do is calc the section properties of the supporting angle or channel and calculate the max UDL for the span and take 1/2 the total UDL as the reaction. I then calculate the moment based on the eccentricity of the support condition to determine the moment in the 'clip angle' at the end. Using the clip angle thickness and the length, I calculate the moment resistance of the clip angle... I can override the max reaction calculated to imput a real load, change the eccentricity, and change the length and thickness of the clip angle to suit... I do the same thing with C Sections and end clip angle supports... I can even change the weld size or electrodes... I may have a dozen of these support conditions in a week. If the clip angle is fixed at the support, I basically half the eccentricity, assuming it is fixed at each end. I append the summary printout for several conditions to a single project file... no rocket science...

Often loads aren't specified, except based on UDL max for the span... sometimes they spec angles and other times they spec channels. I forgot to add that I can also change the grade of steel for the main member or for the clips. I don't check deflections.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

RE: Steel Angle Bending/Splitting

This is a schematic...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

RE: Steel Angle Bending/Splitting

(OP)
Thanks for the diagram Dik. Do you consider it any differently if it's just the horizontal piece of an angle that extends over the OWSJ, without a discrete plate where it transitions to the full angle?

I can calc the moment in the flat plate based on the UDL and check it works for bending as a plate, I'm more interested in how it behaves (and what I can count on) when the vertical leg is reintroduced.

RE: Steel Angle Bending/Splitting

As I noted earlier, "For light loading the proposed one is workable and likely less costly. The load capacity (reaction x the eccentricity of the reaction) is limited by the capacity of the leg thickness x the width of the angle. Your detail can accommodate loads and is limited the thickness of the supporting clip x the length of the supporting clip which can be 6" or 8" or more." for light loading removal of part of the leg of the angle can accommodate light loads. If they are for trimming out openings in a roof and not used for supporting significant loads, they are likely much less costly.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

RE: Steel Angle Bending/Splitting

I would be hard pressed to criticize the manufacturer's detail, as I have detailed opening frames that way for many years.

RE: Steel Angle Bending/Splitting

Quote (XR250)

These are overhead welds (in retrofits) - which suck in general. I would argue without the vertical leg of your clip angle in the way, it is an easier weld.

Speaking of retrofits I have been doing a few of these this year (as the metal sub) due to HVAC upgrading in schools and the like as a result of Covid. Every time I cut open the roof deck to weld the angles to the joists from above as I can't really see a CWB position approved way to access that weld otherwise (like the one Dik shows in his schematic just above).

Also, every time, the roofer gets up in arms that I'm cutting outside the curb extents to perform that weld and say they never see that done. But to date, not one of them has been able to tell me how that weld gets done in a retrofit without opening the roof deck. What typically happens in a retrofit in your experience? How does that weld get performed (from angle that sits on top of OWSJ to the OWSJ at the sides) or do we think that weld just DOES NOT get done in a lot of cases (and angles just hang there) and that's why the roofers are saying they never cut open the deck?

RE: Steel Angle Bending/Splitting

RE: Steel Angle Bending/Splitting

Yes I agree if the EOR allows welds there (the thickness of top chord can be a bit of a problem for small angles so not all are agreeable to this). But I'm talking about welds on-top of the OWSJ like Dik's sheet, which is all I have been seeing and EOR's have been unrelenting about doing something different. How does this get done without opening the deck? I just need to know I'm not crazy!

RE: Steel Angle Bending/Splitting

Quote (XR250)

Looks like I got your panties in a wad :)

Please... when it comes to structural engineering, I know no panties but wadded panties.

Quote (XR250)

These are overhead welds (in retrofits) - which suck in general. I would argue without the vertical leg of your clip angle in the way, it is an easier weld.

Okay, I see what you're getting at now and I agree. When you'd mentioned the 6" absence of the angle leg parallels to the clip, I thought you were trying to clear existing services or something which sounded ridonculous.

I've not done angle frames for retrofits. When I've done retrofits, I've used a detail using two piece channels that get lap spliced and tried to slot the clips in through the deck flutes without having to lift the deck at all. It's complex and never seems to work out as well as I want it to. My version of your weld happens on the far side of the OWSJ chord with this setup, however, which is why weld access has not been an issue for me.

Can you describe how your retrofit system works in more detail? Do you assemble the frame in the field, angle by angle? Do you attempt to slot the coped, horizontal angle leg into the deck flutes or just lift the deck locally and put it wherever it needs to be? With a single piece angle, I feel like you'd need to come into a flute skewed at one end and then swing the other end into place, lifting the deck as you go.

RE: Steel Angle Bending/Splitting

Quote (Enable)

...or do we think that weld just DOES NOT get done in a lot of cases (and angles just hang there) and that's why the roofers are saying they never cut open the deck?

That's my suspicion when the clip angle setup is used.

RE: Steel Angle Bending/Splitting

Quote (dik)

I then calculate the moment based on the eccentricity of the support condition to determine the moment in the 'clip angle' at the end.

Firstly, the detail that you've shown is not the alternate one that OP's been asking about.

Secondly, the calculation method that you've described glosses over some important stuff in my opinion. See the sketches below. Just running the numbers of flat plate flexure of the clip strikes me as pretty optimistic.



RE: Steel Angle Bending/Splitting

Quote (OP)

I can calc the moment in the flat plate based on the UDL and check it works for bending as a plate, I'm more interested in how it behaves (and what I can count on) when the vertical leg is reintroduced.

In my opinion, this is the fundamental difference between the two setups. The view is from the top.

RE: Steel Angle Bending/Splitting

For retrofit jobs, we don't necessarily weld the angle clips to the joists. We make them put the angle clips in place, and then field cut the angle to fit tight between the clips. weld the angle to the clips. if fastening of the clips to the joists is necessary for uplift requirements, we may look at changing the detail to more easily allow connections. I, like Koot, am not a huge fan of just coping the vertical leg off the angle. the unzipping/splitting failure is what concerns me as well.

RE: Steel Angle Bending/Splitting

Quote (KootK)

Do you assemble the frame in the field, angle by angle? Do you attempt to slot the coped, horizontal angle leg into the deck flutes or just lift the deck locally and put it wherever it needs to be? With a single piece angle, I feel like you'd need to come into a flute skewed at one end and then swing the other end into place, lifting the deck as you go.

Never done it myself. What you are saying is likely how things go down.
I wonder how many of these actually get welded.

RE: Steel Angle Bending/Splitting

I just let it yield... a tad. I'm more concerned about the force on the OWSJ if that's the support. If the loads were major, I'd design different connections.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

RE: Steel Angle Bending/Splitting

Quote (as I can't really see a CWB position approved way to access that weld otherwise)


It's illustrative only... I don't know how the contractor will pry up the deck locally (the deck should be cut at the opening), or slip it into a flute if the supporting angle is short enough. Unless there is movement, the connection is independent of the weld to the OWSJ, or however they secure it... not my circus, not my monkeys... the connection works and they seem to build it.

I just revised the detail, the attachment weld at the top will be a teks without calling it up.


Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

RE: Steel Angle Bending/Splitting

Quote (Firstly, the detail that you've shown is not the alternate one that OP's been asking about.)


I've already explained to the OP that for light loads, there is no problem with the proposed connection. My detail does not accommodate the proposed condition. I don't use the single clipped leg for anything other than picking up deck for a roof perforation... I don't use it for real loads, but you can design for it, if you have to. If you clip the leg from an L8x8x0.5, then you can pick up some 'heavier loads', but you can design for it. No rocket science.

Regarding your marked up comments. I treat the reaction from the flexural angle at the face lf the clip angle... as pure shear; I don't consider a moment. The clip angle is flexible enough that any moment resistance would be small. I then add the thickness of the clip angle to the e1 dimension to get the eccentricity of the moment in the clip angle. I compare the factored moment to the resisting moment. Again, no rocket science.

You've confused me regarding the supporting conditions. The reaction on the clip angle might be near the centroid of the length and the shear centre of the flexural angle might be near the mid thickness of the vertical leg. Moment is relatively small. I don't know where you are getting your assumed centre of reaction from... it's nothing like that. Any 'tipping' would cause the centre of reaction to move closer to the shear centre. I'm not concerned about minor variations... If I have a major load, then I address it... for smaller loads... I sleep sound. Again, no rocket science.

As far as welding the clip angle to the OWSJ, I've modified the SMath sheet to show a Teks, but have left the calcs alone (It defaults to a pinned connection). I've left the weld calculations in place in case I need to develop moment (assuming whatever is supporting the clip can take it.) I still check the weld if applied for half the moment assuming it fixed, in case I need it. The program defaults to a pinned connection, anyway.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

RE: Steel Angle Bending/Splitting

Quote (dik)

I don't use it for real loads, but you can design for it, if you have to. If you clip the leg from an L8x8x0.5, then you can pick up some 'heavier loads', but you can design for it. No rocket science.

Torsion in an angle is about as close as we get to "rocket science" in steel member design. Design Guide 09??

Quote (dik)

Regarding your marked up comments. I treat the reaction from the flexural angle at the face lf the clip angle... as pure shear; I don't consider a moment....I then add the thickness of the clip angle to the e1 dimension to get the eccentricity of the moment in the clip angle. I compare the factored moment to the resisting moment. Again, no rocket science.

No matter how you slice it, there is moment being transferred from the vertical face of the clip angle to the end of the flexural angle. It's the beam reaction times the distance from the centroid of that reaction to the connection interface.

Quote (dik)

The clip angle is flexible enough that any moment resistance would be small.

The clip angle's flexibility is irrelevant as it is the only path available for moment resistance as a matter of equilibrium. The stiffness of the angle only affects the degree to which the prying issue is amplified.

Quote (dik)

I don't know where you are getting your assumed centre of reaction from... it's nothing like that.

The center of the shear reaction at the support is perfectly reasonable where I've shown it assuming a short length of the flexural angle in torsion and a stiff, rectifying cross member as I described previously. Moreover, it's the location that is consistent with the flexural yield line that you propose checking for the design.

Quote (dik)

Any 'tipping' would cause the centre of reaction to move closer to the shear centre.

That's just what I meant by in the highlighted statement below. The center of reaction will be somewhere between the location that I showed in my sketch and the shear center of the flexural angle depending on how stiff the torsion path is within the system.





RE: Steel Angle Bending/Splitting

Quote (dik)
I don't use it for real loads, but you can design for it, if you have to. If you clip the leg from an L8x8x0.5, then you can pick up some 'heavier loads', but you can design for it. No rocket science.

Torsion in an angle is about as close as we get to "rocket science" in steel member design. Design Guide 09??


Torsion is complicated, but you don't have a lot of it here! I think you are looking for problems that aren't there.

Quote (dik)
Regarding your marked up comments. I treat the reaction from the flexural angle at the face lf the clip angle... as pure shear; I don't consider a moment....I then add the thickness of the clip angle to the e1 dimension to get the eccentricity of the moment in the clip angle. I compare the factored moment to the resisting moment. Again, no rocket science.

No matter how you slice it, there is moment being transferred from the vertical face of the clip angle to the end of the flexural angle. It's the beam reaction times the distance from the centroid of that reaction to the connection interface..


You are still only transferring the moment caused by the reaction times the thickness of the clip angle leg + e1 (I generally set e1 as 1" max, for fitup), and this moment is taken by length of the clip angle. The stiffness and strength of the thickness of the clip angle leg pales in comparison to the stiffness and strength of the flexural angle. To be conservative, I don't reduce the moment in the flexural angle by this small end moment. pipe

Quote (dik)
The clip angle is flexible enough that any moment resistance would be small.

The clip angle's flexibility is irrelevant as it is the only path available for moment resistance as a matter of equilibrium. The stiffness of the angle only affects the degree to which the prying issue is amplified.


The clip angle's flexibility is what allows you to treat it as fixed at the flexural angle and use an eccentricity of the angle thickness + e1.

Quote (dik)
I don't know where you are getting your assumed centre of reaction from... it's nothing like that.

The load on the flexural angle is approx the shear centre of the angle or maybe near the centroid. The 'reaction' on the clip angle is approximately have the length of the clip angle. The distance is small.

The center of the shear reaction at the support is perfectly reasonable where I've shown it assuming a short length of the flexural angle in torsion and a stiff, rectifying cross member as I described previously. Moreover, it's the location that is consistent with the flexural yield line that you propose checking for the design.


Unless we're talking about different things, the reaction on the clip angle would be in the middle, and not at the end as you have shown. With any deformation this would move towards the shear centre or centroid of the flexural angle. Any torsion generated is negligible, IMHO.

Quote (dik)
Any 'tipping' would cause the centre of reaction to move closer to the shear centre.

That's just what I meant by in the highlighted statement below. The center of reaction will be somewhere between the location that I showed in my sketch and the shear center of the flexural angle depending on how stiff the torsion path is within the system.


... and much closer to the shear centre, but definitely between the mid point of the clip angle and the shear centre. I think it's time to drop this. pipe

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

RE: Steel Angle Bending/Splitting

Quote (dik)

Torsion is complicated, but you don't have a lot of it here! I think you are looking for problems that aren't there.

And I think that you are entirely ignoring one of the most important aspects of the design of these systems.

Quote (dik)

The stiffness and strength of the thickness of the clip angle leg pales in comparison to the stiffness and strength of the flexural angle. To be conservative, I don't reduce the moment in the flexural angle by this small end moment.

The issue is not the moment in the flexural angle but, rather, the moment in the connection between the clip angle and flexural angle. And the relative stiffness between the clip angle and the flexural angle does not affect the load distribution within the connection at all. This is because the connection is made to the web of the flexural angle which is, for the purpose of the connection design, effectively rigid.

Quote (dik)

Unless we're talking about different things, the reaction on the clip angle would be in the middle, and not at the end as you have shown.

How about a sketch? Heck, take mine just add a dot and an arrow to it or something.

Quote (dik)

Any torsion generated is negligible, IMHO.

And in my opinion, it's the dominant design issue for the alternate scheme proposed by OP's fabricator. Moreover, since you're obviously not checking the torsion, it would seem that your opinion in this is based on qualitative judgement at best.

Quote (dik)

I think it's time to drop this.

Then drop it. You can't expect to terminate the conversation and have the last word all in one post.

RE: Steel Angle Bending/Splitting

I prepared the sketch below to further explain my belief that there is no way to do these two things simultaneously:

1) Utilize a weak axis, flexural yield line that is the full width of the horizontal angle leg and;

2) Reduce or eliminate the torsion in the stringer angle.

Fundamentally, I believe that this is because, once a full width uniform flexural yield line is chosen by the designer, a commensurate full width shear field is necessary on that line in order to satisfy equilibrium. So the only path to reduced angle torsion, then, is to assume a flexural yield line width shorter than the full angle width.

RE: Steel Angle Bending/Splitting

Jeez guys! It is just a small roof support! Go have a beer! upsidedown (Though even the smallest design challenges can have deep engineering/learning.)

Well I have had a couple beers now and because I was politely asked to stick my head in here, I have done so and had a read. This whole approach for roof penetrations is unfamiliar for me so it has taken a fair bit of brain power just to get my head around what is happening. Not to mention the different terminology and roof framing approaches. Oh and to add to all that you guys are much more adept at using appropriate engineering terminology, I just try go with my gut and then try to manipulate the mathematics or the computer to align with my gut rednose.

Kootk dragged me in here to have a look at his sketch above, so I have done so. To me it makes sense, as did his previous comment on this matter. There is no way the full width of the horizontal angle leg can be engaged. (I'm sure this can be adequately demonstrated with FEA which I am known to lean heavily on, but I don't think it is necessary here.)

In my mind I'd treat the connection to the OWSJ as a bearing connection as though the weld isn't even present. In which case the angle would rotate until it bears mostly about the "R" shown in Kootk's drawing. If weld IS present the the result is mostly the same just with more torsion in the angle and an greater reaction at "R" and tension at the toe of the angle.


Going back to the start. I agree there is plenty of reasons not to like the alternative approach. I don't agree that the original approach is more difficult/expensive to fabricate but it is more difficult to retrofit as exhibited by the good drawings from XR250.

RE: Steel Angle Bending/Splitting

Quote (human909)

Kootk dragged me in here to have a look at his sketch above, so I have done so.

The intent of my summons was not to get your input on our little deck angle discussion although your comments are, of course, welcome. I believe that I'm on to something much deeper than that which, I hope, might answer a long standing question that I have regarding concrete flat plate design.

If you consider the sketch below in the context of this thread, you'll agree that we have two, competing wishes for this:

1) We would like to be able to use the full width of the flange in flexure, ala yield line voodoo.

2) We would like the center of shear in the cross section to stay close to the shear center of the cross section in order to limit torsion on the member.

I hypothesize that those two wishes are incompatible. I believe that, once you lay claim to the full flange width in bending, that locks you into spreading the shear out uniformly as well. And I believe that I can prove this, somewhat, via hand sketched physical reasoning which is, as you, my preference with most things.

Ideally, what I would also like to do is model the setup in a way that would confirm or refute my hypothesis. However, the model would have to incorporate flexural plastification along the bend line and the associated redistribution of internal forces. Is this something that you would have the ability to do if you had a mind to take it on?

Should you be feeling super keen, please don't run off and model the angle. I would want to test a similar, easier, more strategic setup.

RE: Steel Angle Bending/Splitting

I can crank the handle and run a model of your choosing. I can model the whole setup here without too much difficulty. But I cannot model "flexural plastification", I did have a quick check of Nastran InCAD which I use, but no plastic modelling that I can see. Scratch that I can deal with plastic deformation... Give me the idealised model you want and I'll run it. Honestly I think modelling the full angle setup is workable and not difficult.

Quote (Kootk)

I hypothesize that those two wishes are incompatible. I believe that, once you lay claim to the full flange width in bending, that locks you into spreading the shear out uniformly as well. And I believe that I can prove this, somewhat, via hand sketched physical reasoning which is, as you, my preference with most things.
I agree they are soley incompatible for the reasons you stated.

RE: Steel Angle Bending/Splitting

I modelled it up.

The model (half model using symmetry)


Without plastic deformation:


With plastic deformation:


Nothing amazing or surprising to see here IMO. But if you want me to do more just ask.

RE: Steel Angle Bending/Splitting

Quote (human909)

I modelled it up.

Dude, what did I just say?

Quote (KootK)

Should you be feeling super keen, please don't run off and model the angle. I would want to test a similar, easier, more strategic setup.

Kidding, obviously your at liberty to model whatever you want to model. That said, I have a very different model in mind that will be designed to strategically tease out the things that may be "amazing or surprising". That stuff tends to get lost in the noise of unnecessarily complex modelling exercises.

As far as what you've modelled so far goes:

1) If the plasticity has been modelled as we discussed, there would pretty much have to be an interesting result in there somewhere. Either the shear at the bend line is uniform or it is not. Either way, I for one would find the result interesting.

2) I feel that the interesting things to see from a reporting perspective will not be the Von Mises stresses but, rather, the principle bending and shear stresses at the plastified bend lines. If the plastification has been modelled as we wish, there really shouldn't be a flexural stress hot spot as shown below.

Again, though, I would recommend holding off for the more strategic modelling setup.

RE: Steel Angle Bending/Splitting

This is what I want to model. I mean to make this exercise it's own thread but, since your patience wanes, I figured it best to get this in front of you sooner than later.

RE: Steel Angle Bending/Splitting

Also, if there is some way to make the yield line bend line a boundary condition such that the plate elements butt up cleanly and squarely to it, that would be helpful.

RE: Steel Angle Bending/Splitting

Ok I'm modelling it now. I am not quite clear on the right hand support condition and where you want the loading. Also I'll need you address to send my invoice. auto

(oh and I charge double when somebody gives me non metric units!, but for time I've got I'll do inches)

RE: Steel Angle Bending/Splitting

Quote (human909)

I am not quite clear on the right hand support condition and where you want the loading.

It doesn't really matter. All of the action will be at the left support and and the first few beam depth worth of length into the beam proper. Whatever's easiest for you really. If you'd prefer to do an 8' beam with the right end sitting on a column and a point load in the middle, then so be it. As I mentioned previously, I'm just trying to pare it down to the bare minium to make it easier to separate the wheat from the chaff.

RE: Steel Angle Bending/Splitting

Quote (human909)

Ok I'm modelling it now.

Truly, there's no rush. Take days, weeks, months... I still have to sketch my my "proof".

RE: Steel Angle Bending/Splitting

I'm not feeling rushed. But if I don't get it done now, I will lose my enthusiasm and it won't get done. I'll do it now. I'll keep you updated as a quick back and forth is much more efficient.

Quote (Kootk)

As I mentioned previously, I'm just trying to pare it down to the bare minium to make it easier to separate the wheat from the chaff.
Got it.

And it is good practice for me to help get my head around some of the finer aspects of the FEA modelling and interpreting the results.

RE: Steel Angle Bending/Splitting

Principle bending stress:

RE: Steel Angle Bending/Splitting

I can't figure out the suitable shear stress. It could be my use of the software, but more likely it is my poor conceptual understanding of stress planes/tensors/mohrs circles. It makes my head hurt. I figured I need ZY shear stress but I don't have that choice.

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