Plate gussets....

[pilebuck]

Another way to make plate gussetts you may or may not like. Let's say you need to fab and weld some 12" plate gussets for a project.Most times you will see just a regular 12" 90 degree triangle. Another option that can be advantageous in certain applications is to layout a 13" 90 degree triangle and then cut the last inch off square at both outside corners. Still gives you a 12" gusset but it gives you more "meat" especially if doing multiple passes and looks professional. I worked at a shipyard that preffered that all gussets were done in this fashion. Not saying it's better or anything, just another way to make something as simple as a gusset.:)

[4on12]

Where I work we leave a 1/2" "leg" on our gussets. It looks nicer and it is easier to wrap the welds around the ends.

[farmersamm]

Just for sake of discussion

Would a gusset, out of line with the main member, give as much strength. The lap moves the gusset outside of the line of the original member, and offsets the web. The force has to make an "L" because of the lap. I wonder if it would make it more susceptable to buckling because it isn't a straight line force.

I know this isn't a ship, but the theory is the same I think.

In the pic, the force travels thru a unified planar web, no offset.

Welds on either side of the plate make it a sound joint. Lapping the weld/joint would not get anymore weld on the structure.

[lotechman]

Another way to make plate gussetts you may or may not like. Let's say you need to fab and weld some 12" plate gussets for a project.Most times you will see just a regular 12" 90 degree triangle. Another option that can be advantageous in certain applications is to layout a 13" 90 degree triangle and then cut the last inch off square at both outside corners. Still gives you a 12" gusset but it gives you more "meat" especially if doing multiple passes and looks professional. I worked at a shipyard that preffered that all gussets were done in this fashion. Not saying it's better or anything, just another way to make something as simple as a gusset.:)

It IS better than a pointed end on a gusset. The critical ends need a complete weld bead that is closed and wraps around as you mention. In my experience with structural clipped ends on gussets is standard practice and the inspector has a conniption if the ends are not closed properly or there is undercut. Your yard is producing quality.

[denrep]

. . .12" plate gussets for a project.Most times you will see just a regular 12" 90 degree triangle. Another option that can be advantageous in certain applications is to layout a 13" 90 degree triangle and then cut the last inch off square at both outside corners. Still gives you a 12" gusset but it gives you more "meat" . . .

Off square at both outside corners?
I can't quite grasp the concept.

Pilebuck, anybody? :confused:

Thanks

47029

[lotechman]

In your picture the gusset runs to a point. The accepted method is to clip the ends.
The end of the weld is run around the end that stands vertical to the main member. It reduces risk of stress concentration at the end of the gusset.
If you are really fussy like on heavy equipment a series of welds that cascade/ taper off the end of the gusset are done. On large equipment the welds run another couple of inches past the gusset end in a cascade.

[dave powelson]

Off square at both outside corners?
I can't quite grasp the concept.

Pilebuck, anybody? :confused:

Thanks

47029

Albert--see below. The red outline addition describes the clipped gusset profile.

Sam--setting the angled edge of the gusset plate outside the vectored
force line, reduces the tendency of the gusset to deform under stress.


http://weldingweb.com/attachment.php?attachmentid=47030&stc=1&d=1267396427

[ZTFab]

Like this Denrep...

47035

[denrep]

Thanks men. I'm up to speed now.

Sorry, I interpreted cut "off square" to mean cut "not square" rather than "cut square."
I thought Pilebuck was laying out a way to get the larger gusset out of 12" stock.
That's what had me stumped.

Thanks all for the help, and Pilebuck for the tip.

Good Luck

[farmersamm]

Ok, I got it. I was thinking in terms of lap joints, not in terms of removing the far corner of the gusset while still maintaing the full 12" gusset.

[pilebuck]

It IS better than a pointed end on a gusset. The critical ends need a complete weld bead that is closed and wraps around as you mention. In my experience with structural clipped ends on gussets is standard practice and the inspector has a conniption if the ends are not closed properly or there is undercut. Your yard is producing quality.

Thanks Lotechman, I (cough,cough) lean towards clipped ends myself but you always have to give some guys a way out! If they think they came up the idea it it always seems to go a little smoother.:cool: Honestly, If I was repairing a traditional gusset where you could see a bunch of other gussets done in the same fashion I dont know that I would change it cause it might look off. However if I where making something new I would definately try to push that through though. Yes it does use a little bit more material, yes it also is easier to weld. Stronger??...probably, not that the 90 degree one isnt strong enough for the application though. Just thought I'd throw that out there fellas, if you dont like it you can throw it right back:jester:

[farmersamm]

Had to go feed the ladies:laugh:

Ok, so tnat I'll know what you're talking about, let me run this by y'all

Is the pic a correct understanding of the concept? legs equal on both gussets, but extra material beyond the clipped end?

[farmersamm]

Or, just clip the end of the gusset you've made?

[pilebuck]

You got 'er sam.If you clip the ends of a 12 inch gusset one inch you have an 11 inch gusset. So layout a 13 inch, when you buck the ends off you have your desired 12.

[farmersamm]

Does the extra material beyond the clipped end SEE XXXXXXXXXX's, add to tensile and/or compressive strength by virtue of additional material outside the line of force? Like reinforcing a flange on a beam to some extent?

Hard to put into words, but I think I'm seeing a real advantage to this. It's new to me

[pilebuck]

Hey Sam, see Dave Powelson's post above. He said it better than I ever could!

[farmersamm]

I looked at Dave's post, but it doesn't tell me the "why", just the benefits of the design.

Allright, so I'm weird:laugh: I need to visualize what's actually going on in the metal, and why it works

Is the stress moved from the outside edge/chord by clipping it, reducing the possibility of tearing or buckling? The new chord now being inside the bulk of the outer edge.

I wish I was more conversant in this:cry:

[farmersamm]

In laymans terms, I think I'm seeing the equivalent of a strongback

[denrep]

Which brings us back to layout.
With careful layout this can be cut out of 12" stock, or 2 out of 24" and so on - usually much easier to hit on without wasting material than 13".

Pilebuck - With "last inch off square" I thought you were getting at something like shearing on the green line.

Good Luck

47061

[pilebuck]

Denrep, I humbly disagree that you can get a "bucked"12" gusset out of 12" stock. Im not very good at pictures but what is the largest 90 degree triangle that you can draw inside of a bucked ( one inch from both outside corners) 12" gusset?? Answer= 11inches. So to get a "true" 12" gusset that is bucked you need to layout 13.13-1=12.
Just like when you are inspecting or sizing fillet welds, whether it is convex or concave it is still only the size of the largest icoceles(SP?) triangle that can fit inside of it. Ive read many of your posts and you probably have got me beat 99% of the time, but on this I think I am correct.

DISCLAIMER:laugh: If you somehow prove me wrong it wont be the first time!

[William McCormick Jr]

Unless someone did some destructive testing to see which is stronger. I would not do something like that on my own.

The reason is that, it may keep a tear from starting, if you run the gusset hypotenuse all the way to the weld. If you add that little extra, it might cause a sudden tear. Rather then a stretch under destructive testing.

I have seen that type of gusset used. Used it myself. But it was done on a flange that was bolted to another flange. So that there was no real stress on the starting weld on the flange. The bolted flange would give before the weld.

Normally you would want the gusset to be very thin at the edge. So it does bend or give, under severe duress.

Normally if you would like to change up a gusset design, you would then have to create a weakness in the gusset. So that it does not cause a tear on the starting edge. You would make it something like the one in the attached image.

From my experience this is rather important.

Sincerely,


William McCormick

[denrep]

. . .a "bucked"12" gusset out of 12" stock. . . .

The blue line this time:
47065
Wouldn't it?

Why waste the extra inch only to cut it off?
This would give at least two 12" "bucked" gussets per 24" of material. No? And two smaller gussets as drops.

I usually make a cardboard layout template before cutting expensive steel.
Sometimes I'm surprised by the mental block I may have before actually visualizing a cut in several different ways.
Here, rotating the blue pattern counterclockwise might give better nesting and thus more material savings.

Good Luck

[pilebuck]

:)I didnt realize this would be so polorizing. I can see both sides and am really unbiased. I do think the bucked gusset is stronger and easier to weld. I agree that you will not get as many cuts out of a piece of steel. I barely see how it can create a stress riser and if you round the corners a little bit that point would be nullified. My experience mostly is with big (many millions) government jobs, million dollar plus barges, derricks, boats bridges etc. They are not going to be as concerned with a little bit of waste (think relative) as Joe Blow's mom and pop shop making gussets for a swing set. Not talking down to anyone here, just trying to be a little funny. You guys all have somewhat valid points. I never would deviate from a contract or set of prints on my own cause that would be my azz.I keep my mind open and still learn something new some days.:D Im going to step out of this and let you guys hash it out. Im a cwi/weld forman and still do not claim to really know . I mostly work with D1.1 and actually dont ever recall seeing this laid out in any book. Not saying its not in any AWS publication, I just havent seen it and am too lazy to dig out my books to look.I also dont claim to speak on behalf of AWS or any other company for that matter in this instance.

[denrep]

. . . I do think the bucked gusset is stronger and easier to weld. I agree that you will not get as many cuts out of a piece of steel. . . .

Actually, I think that with good layout planning, the "buck" may yield more pieces per plate. And again, that's what I thought the original post was describing.

Good Luck

[Scott Young]

This is all great to read, but in my experience, I have been dictated by an engineer the design of the gussets. They have been bucked and unbucked. Every one was wrapped and sealed. I don't see wrapping a bucked gusset being easier than a pointed end.

[pilebuck]

Actually, I think that with good layout planning, the "buck" may yield more pieces per plate. And again, that's what I thought the original post was describing.

Good Luck
I gotcha now Denrep, I couldnt see the tree's...
Your saying actually layout and cut the bucked gusset instead of bucking the ends off a "regular" one. I'm no mathmetologist ,but I could see how a little carefull layout on the right sized piece of plate...

Well played Sir!

[William McCormick Jr]

Really nice gussets are tapered, arced.

Like you cut a circle in a big square and just used the corners. So they flex before tearing. You have to imagine if something tries to rip the gusset out. It is going to pull most on the ends of the gusset. At the start of the weld. When that happens you want the gusset to flex a bit. So that no tear or fracture starts there. Over time with no flex you will get stress fractures. Or crack the weld.

Sometimes you will see lightning holes as well in high end gussets. Because they make them so large and so tapered. They remove the extra weight by putting holes in them.

Look at any structural beam, "U" channel, or angle. You will see a radius there in every crotch. This relieves the stress right at the corner of the angle. It moves the stress out and away from the crotch. The slow gradual radius, causes the legs to bend farther out. And more evenly. You will never see an inside 45 degree chamfer in the corner. Because it would just tear right next to the chamfer.

If you create your gussets the same way, with a radius. They will do the same thing. Causing a nice even bend upon destruction. Often allowing something to slowly come to the ground. Rather then a quick bang a sudden fall.

I know from tuna towers that a sharp 45 degree gusset will break at the weld all the time. Whether it is pipe or plate. All you have to do is tapper the gusset or pipe, and it will not crack.



Sincerely,


William McCormick

[Metarinka]

where I came from we clipped gusset ends. for the burn back issue. Also you snip the base 90 deg angle as you don't want to tie in welds in 3 plains (Per AWS D1.1)

Thing is on the welds I designed I always left the the last .5" unwelded. Reason being, the bending force of a beam enough to get plastic deformation (usually 2%) was much lower than the buckling strength of a properly sized gusset. Hence the highest concentration of stress was at the middle of a beam. Therefore making the welds any stronger wouldn't add any strength and just put in more heat. We left the ends unwelded to prevent burn back Or under cut.

If the gusset fails before the span deforms, something isn't right, and if the span deforms then it's going outside our design specs.

[MoonRise]

It all depends. :D

If the design and structural details are critical, then that is what the engineers are supposed to figure out. :D

And Samm, regarding your lap-joint gussets, again it depends. :laugh: It depends on the load vectors (direction and magnitude of the forces) and the specific structure and how it resists/reacts to the loads. Again, for critical stuff, that's what the engineers are for. :D

Short answer to 'is the clipped gusset stronger' is "Sort of, but is the rest of the structure able to use that strength increase to any advantage." Again, for critical stuff, that's what the engineers are for.

[jsfab]

Doing mostly repairs, experience also comes into play. Sometimes the clipped off ends are best, sometimes the fully tapered ends are most appropriate. In some cases, rounded ends are better. Sometimes curved gussets are the best fit for the job. There is no one "best fit" for all applications.

[William McCormick Jr]

I destructively test things all the time. The hollow weld, usually done by TIG stands up very well under actual destructive testing. So well that almost all critical welds are TIG welds.

It will never be the weld on steel itself failing, if properly welded. By all my years of testing these things, it is the material next to the weld. Except for ground butt joints on certain alloys.

http://www.rockwelder.com/welding/SteelTIG/SteelTIG.html

It will fail right next to the weld every time.

That under cut or hollow is purposely done in manufacturing, with automated TIG. Because the weld, causes a three dimensional structure to be formed. That is naturally many times stronger then either piece being bonded. So you want that radius or hollow weld, like you see in the crotch of an extrusion, to allow some flex. Instead of a tear.

The weld itself can be much harder then the surrounding material. Causing it to be hollow allows it to flex. Also saving the materiel next to the weld. They test this stuff in factories millions of times. They know.

Having a hollow or radius weld, often saves a weld, or the material next to it. By flexing or giving.

I was taught that not finishing a weld, or not welding out to the end of a gusset is wrong. I was shown a number of examples of failure. That would not have occurred if the part was welded all the way.

If I did not weld that test piece in the movie all the way to the end. It would have torn right up against the weld. And not taken nearly as much pressure to tear.

If you work with aluminum, this becomes very apparent. Most guys work only with steel. And the problem is that steel is just so strong. That you do not get to see it come apart. If you put steel under the load it is designed for, and you do not finish welds. They can let loose too.

Working with aluminum exaggerates the weakness of the weld, especially at the start or stop of a weld. You get to see perhaps a thousand percent more tack failures, then with steel. You get to see short runs of weld fail as well with aluminum. Usually as you go to tear a piece of aluminum extrusion off a plate. Something that will not happen with steel, or stainless steel, without a cutting wheel.
Unless you load the steel up with working pressure. Then it does happen to steel just, when you need it most.

Gussets welded out to the edge that failed, only failed because they are too small for the load, and or they left the gussets straight. You are supposed to arc a gusset. TIG and MIG and Stick welders will sometimes lay a few passes over the end of a straight gusset. So that it mimics an arced gusset.

It does work but falls under the blacksmith trade.

I also know guys that knew we were supposed to weld all the way, and they on their own, decided that we were only going to weld them partially. That plays into a lot of these rules of welding becoming standard operating procedure. Ha-ha. Even on high end jobs. I see these really wild short cuts.

When you are building square frames, a straight gusset is not that bad, because the frame can almost take care of itself. You are really often just putting the gusset in to protect the welded joint of the frame. So there are many considerations. But if your gusset is to sure up a long leg. You really should arc it. When it fails the arced gusset is a great thing.


Sincerely,


William McCormick

[denrep]

William - As has been said, this is much more complex than meets the eye.

I don't believe that a radiused gusset is the end-all answer for every application. Gusset design may have as much to do with practical utilization of steel, as the gusset's optimum strength or weight. For example, as seen in post #27, the "skeleton" left from cutting eight gussets, could possibly have made four more gussets, if all gussets been a simple triangle shape. Also the simple shape can be quickly cut with an ironworker.

Radiused gussets are often a by-product of circle cutting. That may explain some production applications. But in fab work, to arbitrarily cut a radius into a triangle shaped gusset, I don't see how that could be justified.

The corner radius seen on structural steel shapes? Could that just be a side effect of the mill's most practical rolling methods?

Good Luck

[RancherBill]

I'm not an engineer.

Joints are under stress and thus you use gussets. The stress can be either tension or compression.

It looks to me that this type of gusset is used in areas of compression. You have the meaty part that is like a 13" gusset, but you welding much less.

You have 7.5% less welding (2 sides x (12"+12")) = 48" vs (2 sides x (13"+13"))= 52" 4/52. Welding labour inspection etc is where the big cost is in a joint.

That's my thought.

[William McCormick Jr]

No the arc or radius is a very powerful basic tool of engineering. I will be the first to say that it is a dinosaur. Not that it is a bad dinosaur, rather the contrary. It is a good dinosaur.

Either compression or opening of the joint will benefit from the arced gusset. It adds power.

If you look at how the arc is opened or compressed you will see that, because the gusset will give or flex slightly out at the end. It puts a parallel force running along the weld on the weld itself. Rather then focusing all the force on that first or last tack on the two ends of the hypotenuse.

Instead of just the one tack at the end of the gusset holding the weld from tearing. When you put a gusset onto a quarter inch or half inch wall tubing, and that wall flexes. When you open or close that joint with force, a straight triangle gusset will immediately tear the tack at the end of the gusset. The notch will make it worse. All you have to do is break that one tack. There is not much else holding it after the tack breaks.

I know this from a lot of aluminum welding. Where we see failure a thousand times to one over steel. That the gusset that meats at a 45 is inferior and causes tears in the tube wall it is fastened to right away.

Sometimes while fixing the pull of the weld. The tubing will just bend right there at the end of the gusset. Abnormally. Because that spot becomes a pivot point. It also causes collapse of the tube.Or elongation of the tube right there. The rest of the weld cannot help the two end tacks. By the time the rest of the weld is stressed it is too late. The first tack breaks and the tear runs up the weld or along the weld.

I will weld up two or three different styles of gussets and destroy them.

Sincerely,


William McCormick

[farmersamm]

Somebody gave me some material to read

I did my best to understand it, it related to stress risers, and abrupt changes in direction.

Would it be safe to say that a gusset under tension would be better shaped in a convex form, and a gusset under compression be shaped in a concave form?

I'm basing this on the ability of a round shape (ie. a tank, or a bow) to take stress is very good.

Are we "rounding the corner" to take stress off of an otherwise abrupt angle?

[dave powelson]

Somebody gave me some material to read

I did my best to understand it, it related to stress risers, and abrupt changes in direction.

Would it be safe to say that a gusset under tension would be better shaped in a convex form, and a gusset under compression be shaped in a concave form?

I'm basing this on the ability of a round shape (ie. a tank, or a bow) to take stress is very good.

Are we "rounding the corner" to take stress off of an otherwise abrupt angle?

Sam, gussets help to distribute the loading into the members, while the load changes directions.

Blodgett's Basics---a regular column in Welding magazine--this site's sponsor, gives all manner
of real world examples, by a P.E. of real world experience. This is ignored by almost all posters
in this forum.

[farmersamm]

Dave, I gave it a look

Came up with some explanation of incorrect placement of gussets, but no article explaining the mechanics of it.

Point me in the right direction with an article name.

[farmersamm]

Actually, THE MECHANICS OF THE TOPIC WE'RE DISCUSSING

NOT INCORRECT PLACEMENT OF GUSSETS

[farmersamm]

where I came from we clipped gusset ends. for the burn back issue. Also you snip the base 90 deg angle as you don't want to tie in welds in 3 plains (Per AWS D1.1)

Thing is on the welds I designed I always left the the last .5" unwelded. Reason being, the bending force of a beam enough to get plastic deformation (usually 2%) was much lower than the buckling strength of a properly sized gusset. Hence the highest concentration of stress was at the middle of a beam. Therefore making the welds any stronger wouldn't add any strength and just put in more heat. We left the ends unwelded to prevent burn back Or under cut.

If the gusset fails before the span deforms, something isn't right, and if the span deforms then it's going outside our design specs.

If this is simply an issue of burnthrough, or excessive heat I'm sticking my head in the toilet:cry:

I've always clipped the crotch/inside corner of the gusset to clear the welds. Didn't know if it was proper or not, just did it.

Now I'm worrying about the outside corners.

If someone who knows what they're talking about, and can transpose the double speak into laymans terms it would be very beneficial. Best teachers are the ones who can lay it out in simple terms without clouding it with jargon.

On the third reading of your post, I see the logic.

Seems to me that the correct thing is a proper sized gusset, welded in a manner that doesn't destroy the material, and a reduction of heat in the area where there is a directional change in force.

Now, I can pile on gussets and extra steel till the cows come home, but if the basic structure isn't strong enough, the gussets aren't gonna help all that much. Material beyond the gusset has to be properly sized, or it will fail........just beyond the gusseted area:D You can reinforce the joints between two pieces of spaghetti, but ya still got spaghetti. I figure that's mostly common sense.

I would estimate that at least 60-70% of my use of gussets is in areas under tension, not compression. And a goodly number are under both tension and compression.

Behavior under each loading condition must be different.

[farmersamm]

Personally I have never trusted stuff in compression, any slight deviation from plumb, or a straight line, results in buckling.

It seems that stuff in tension is easier to predict

[dave powelson]

Actually, THE MECHANICS OF THE TOPIC WE'RE DISCUSSING

NOT INCORRECT PLACEMENT OF GUSSETS

Sam, my reference to Blodgett's Basics was not a slam towards you.

I don't have any specific reference source for this stuff.
As you and others that have posted here have noted,
gusseting is somewhat of an experience/judgement thing.

(Putting 2 gussets on either side of a thin wall tube structure vs.
a single gusset in the center of the tube walls is a good example.
However even in this, it depends on the design intent!)

Finite Element Analysis (FEA) can give pretty stress distribution pictures.

What I've noticed in recent years, is that too often--designers fail
to recognize that early on in the progression of a structural failure--
as cracking, bending, twisting, torsion, pulling, compression, shearing develops;
then suddenly their computer blessed modeling has no semblance to reality...

....the basic reality being that before things crack, distortion has already come
into play--which can trash the modeling they've done--ASSuming that they
are dealing with a pretty much, static structure--not a dynamic structure
that will 'move around' in normal use...and it just ain't so.

[The Twin Cities Bridge collapse and the Bay Bridge band-aid repairs
are 2 classic, graphic examples.]

[farmersamm]

No trashing even considered Dave, put that out of your mind, this is a free for all. In the time I've been here neither you, or I , have ever slammed each other, and it hasn't happened now

[William McCormick Jr]

Here is a movie of the different types of gussets letting loose.

http://www.rockwelder.com/Flash/Gusset/Gusset.html

This is a very real or true to life test. This is how I would have welded them if anyone had handed them to me to weld.

Except I did not build up the ends like I normally would. Only a few old timers do that. And it would not be done by the average welder today. So I did not do that. It would have helped the straight gusset a lot.

I have been doing this my whole life. My father did this professionally at Grumman Aero Space. Where you became an engineer by the hours you spent actually doing real things. He was also an army welder and blacksmith.

I have been discussing this at diner, before kindergarten. This is the stuff we used to talk about all the time. So the tests were about in line with what I expected. I can assure you that the arced gusset also works equally well under compression too.

It takes away that hard spot, the breaking point or axis right at the end of the straight or nipped gusset. I know if you have never seen an arced gusset get destroyed, you would not believe it works so well. So I made the movie.

I have actually seen arced gussets lay huge objects on the ground gently, as the hoist with the arced gussets, was being accidentally destroyed and pulled apart by heavy equipment. I was amazed at how well the arced gusset worked. That is why I went on an on about it. It is worth every penny.

Sincerely,


William McCormick

[4on12]

Thank you for taking the time to make the video.
I will incorporate what I have learned from this thread into future projects I make.
However, my hands are tied at work. The engineers/draftsman specify 100% welded, wrapped, clipped gussets and that is what they get.

[William McCormick Jr]

Oh you gotta see what they tell me to do sometimes. Ha-ha. I try to sneak some good stuff in. But it is rough.

Sincerely,


William McCormick

[farmersamm]

Thanks for the video, but my anitquated Adobe player, and dialup connection, won't allow me to download more than a few seconds of either video clip.

If you still have them laying around, could you post some still pics of the tears?

Sorry, we're sorta out in the middle of nowhere when it comes to internet service:blush:

[William McCormick Jr]

Farmer Sam do you do "You Tube"?

http://www.youtube.com/watch?v=M-SuV6egdeA

You can download this file. It is a self extracting exe file that will unzip the file and then play it if you answer yes. Of course I get all your credit info and those sexy pictures you have over there. Ha-ha.

http://www.Rockwelder.com/WMV/gussetdestroy.exe

I liked the movie better. But these pics do show some interesting things. But I think they hide some interesting things too.




Sincerely,


William McCormick

[Metarinka]

As an engineer, and working with P.E's from time to time on welding issues, gusset design is pretty low down on the list. They are sized according to the design load+safety factor and then a welding engineer or Me, will size the welds according to the resultant design load+ safety factor as well. Also within the welding code there's an additional safety factor so it would be rare for a gusset weld to fail resulting in a structure collapse if the gusset was properly sized and welded. I can do statics and have done weld sizing calculations before. I'm not a P.E so I can't do primary calculations or sign off on a lot of things.

all that being said. In most cases a rounded gusset won't be used because
A) increase difficulty in fabrication or expense
B) not percieved as neccessary

The whole thing about reducing stress raisers and the like is generally true with rounded shapes, but we don't build too many things like that, because of the difficulty in fabricating and fitting up curved structures.

Personally I design all my gussets with clipped ends and a clipped 90, and I terminate the welds .5" from the ends. because i can hit my design load without the need to overweld everything. On dynamically or cyclically loaded structures we might design to lower notches and stress raisers but static objects like simple frames don't generally fall under this, a triangle gusset will be fine.

[Sandy]

Personally I design all my gussets with clipped ends and a clipped 90, and I terminate the welds .5" from the ends. because i can hit my design load without the need to overweld everything. On dynamically or cyclically loaded structures we might design to lower notches and stress raisers but static objects like simple frames don't generally fall under this, a triangle gusset will be fine.

When you say terminate the welds .5" from the ends, are you saying not to weld clear up to the clipped end? Also back in the tight 90 degree corner, does that corner get clipped off too or does it matter?

Thanks,

[MoonRise]

Sandy,

I think Metarinka showed what he meant back in Post # 28 above. Clipped ends, clipped 90 (clip the 90 degree corner) and hold the welds back from the ends of the gusset.

[Sandy]

Sandy,

I think Metarinka showed what he meant back in Post # 28 above. Clipped ends, clipped 90 (clip the 90 degree corner) and hold the welds back from the ends of the gusset.

Yep by golly he did. That's what I was looking for. Thanks. I have submitted the concept to my memory along with a request for permanent storage. :)

I bet the request gets turned down tho. :laugh:

[farmersamm]

Thanks for the stills, and the Youtube video.

Took a quick look at the pics earlier, and will download the video later tonight (4 minutes takes about 45minutes to download)

No gusset fully failed, the structural stuff failed.

I have one question...........how close to the center, or edge, of the tubing were the gussets welded? Closer it is to center, the greater probability that the gusset will pull out before it fails.

The third pic is really interesting, it seems to show the material going plastic (if that's the right word) before it failed. Would that be a beneficial thing in a seismic zone?

In all cases the fracture was beyond the gusseted area. I wonder if a better example would have been main members that would have been stronger than the gusset. It would show how the gusset tears, instead of the failure in the main members.

I think, if I got it right, the moment was transferred from the corner to the outside edges of the gussets. Been really reading up on this, but still haven't got it down pat yet.

But it shows the power of a gusset. In no instance did the reinforced corner fail. The failure was merely transferred further out on the "beam/column/corner".

Also did some reading on stress raisers. Any discontinuity in the material is a stress raiser. Cracks caused by welding (apparently despite lo hydrogen technology, cracks will occur under the weld, microscopic but still there), notches or cutouts in the material, mill flaws, and even pits in the metal. Abrupt changes in direction are stress raisers too If I understand right. Pure and simple, the stress raiser isn't magical, it's just a likely place that the thing will fail due to some imperfection, or the design of the weldment placing stress on a particular point.

I'll figure this out if it kills me, or y'all kill me:D

[MoonRise]

Samm,

Yup, you seem to be grasping a bit about structures and how they can fail.

As I said way back there somewhere, if the structure itself isn't strong enough then the gusset strength may be 'wasted'.

And tech definition time. Material going "plastic" is when the material yields (stretches, bends, moves permanently) or permanently deforms and will no longer return to its original shape/position even after the load is removed. If the material bends and stays bent even when the load is removed, the material has yielded or exceeded the elastic limit or plastically deformed.

http://en.wikipedia.org/wiki/Tensile_strength

http://en.wikipedia.org/wiki/Yield_%28engineering%29

http://en.wikipedia.org/wiki/Plastic_deformation

What I think you are referring to is more evidence of the ductile nature of the metal. Because the material is ductile, it is able to yield (plastic deformation) before finally failing instead of just snapping like brittle material (such as cast iron or glass). They are all kind of related but not exactly the same thing. :D

And yes, a discontinuity in the material is a stress riser. :drinkup:

[William McCormick Jr]

It is even worse on a solid leg, that will not kink, expand, or bend as easily. As soon as you cause that first tack to break, on a solid leg, with a nipped, or straight gusset, the whole weld tends to let loose in one shot. If I get a chance I will do a solid bar test. The arced gusset really shines on solid bar.

Years ago if we used the straight gussets we would run weld bead up and over the gussets ends. And about an inch out on the leg being held by the gusset. This really made them shine. Today they do not do that. That is bad.

The fact I mounted those gussets in the center of the rectangular tube, allowed the nipped and straight gussets a little time, to let the tubing bend rather then just tear it and break it off instantly.

The arced gusset is a forgiving gusset. It helps to even out pressure and keep everything together.

What happens with the nipped and arced gusset is that, it tears the structural tube early on. In real life there is usually not a slow moving force on the long structure.

So when that first tear occurs, the long tube or channel or "I" beam, just instantly becomes a large baseball bat. And swats people, or things. Or drops things, sometimes on people.

If you turn that whole thing into a mushy glob, by the time the channel, tube or "I" beam rips, there is not enough pressure and force to accelerate it. The angle the force is being applied, has changed. Usually to a less positively accelerating angle.

I saw it actually work in real life. I thought it was make believe. I could not believe nothing had ripped. It just laid a very expensive ocean racer on the floor. No weld tears at all. It had strength, all the way to 45 degrees. It was also being twisted as well as opened.

Then the boat gently silently touched down. That is when the fork lift driver realized that something was wrong. It finally stopped the fork lift.

I know that if I had put a regular gusset in there. The weld would have broke, and the whole thing would have not only come down, but shot sideways as the good leg forced the load over sideways.

I had learned the right way to do it. But never saw an actual large structure fail. My father made me weld small things, and showed how little pressure it takes, to break that first tack.

If that first tack is on a gusset, it will usually pull a hole out of the tubing it is mounted to.

People used to come to argue with my father about this stuff. And my father would take a little hammer, put some pressure on the part they were arguing about, hit it with the hammer and it would fall off the weld. People would never say another word after that.

I watched him bend stuff, with a raw hide mallet, that engineers were calculating the size of the press, they would need to bend it. After they saw him bend it with one hand on a mallet, and a few small "C" clamps applying pressure. They changed the whole design of the part.

A lot of people came to look at my collapsed hoist. Engineers, and business owners. They could not believe the welds did not break. That is partially how I was known as such a good welder. The truth is the 98/2 Argon/Oxygen MAG welds, were welds. It was the gussets that were doing the magic.

I was yelling to the guy operating the fork lift to stop, but he just kept going. Stretched the gusset an inhuman amount. If they were taking bets I would have bet against it. Ha-ha.
I was waiting for the crash. Ha-ha.

It is math though. To stretch a gusset, takes massive amounts of horse power. So while that arced gusset is stretching it is applying many hundreds or thousands of horse power to that leg. Slowly bending the leg. The nipped or straight gusset, gives its all in a fraction of a second. So that you loose all that continued horse power, during destruction.

Power is power.



Sincerely,


William McCormick

[LarryO]

Years ago if we used the straight gussets we would run weld bead up and over the gussets ends. And about an inch out on the leg being held by the gusset. This really made them shine. Today they do not do that. That is bad.


William McCormick


I noticed on heavy machinery that if they fish plate or double sections on the boom or stick that they run their welds out an inch or so as your describing. Usually on sections that end with a point or diamond shaped.

Was told by a welder that it helps reduce stess at the edge of the plate.



Good, interesting thread.:drinkup:

[William McCormick Jr]

I made an error, I stated the nipped and arced gusset tear the tube wall early on. I meant the nipped and straight gusset. Sorry.

Sincerely,


William McCormick

[William McCormick Jr]

This is solid bar, I just chamfered the bars enough to weld them. It is a bit cold. But all are welded the same. But you can see how the gussets hold up. The straight gusset did very well. But I would still prefer an arced gusset. I would make it slightly larger though. I believe if it was the same size in the middle as the straight gusset that it would have protected the joint.

The bars the arced gusset was welded to were toed in a little, on a slightly acute angle. I wanted the worst for the arced gusset. I gave the other ones the best chance. The arced gusset had to stretch more.


http://www.youtube.com/watch?v=SRAh1uDgOwM


Sincerely,


William McCormick

[farmersamm]

THANK YOU MR. McCORMICK:waving::waving:

.................................................. ........................................

From what I've seen, the notched gusset doesn't measure up.

Time to failure......4 seconds
Amount of distortion in bar..........negligable (the gusset failed before any stress was transfered to the bar as indicated by the graph)

.................................................. ........................................

The straight gusset fared much better

Time to failure....7 seconds
Amount of distortion in bar...........greater distortion in the bar indicates the gusset held long enough to cause the bar to bend ie. the gusset was stronger than the bar until point of weld failure

.................................................. ......................................

The arced gusset fared the best

Time to failure.....7 seconds
Amount of distorion in bar...........By far the most distortion. This is the real indication of the strength of the gusset.

.................................................. .....................................


And for those that think the weld failed, I believe you have to look very carefully at a "weld failure". Had the welds cracked at some point in the bead it could have been termed weld failure.

These welds pulled out of the parent metal, which proves, as it does most times, while a weld can be strong the failure is most times in the parent metal. The strength of the joint is limited by the tensile strength of the base metal.

I really appreciate the time you put into this. I believe it proved your point.

[farmersamm]

Now to muddy the water a little bit:laugh:

Would the arced gusset do as well as the bucked gusset when in compression?

I'll be real careful when opening my mail, probably be a letter bomb in there somewhere:laugh::laugh:

[William McCormick Jr]

I Thank You guys.

I have been going around saying this stuff for years. But to be honest, I never stopped to do a total test of the exact same three or four pieces with different gussets. I had doubts, and a lot of unknown information. You guys forced my hand to do the tests. I was totally surprised at how well the straight gusset held on the solid bar.

But after some examination, you can see that, the straight gusset with the unbending solid bar, stretched too, like the arced gusset. So it is very interesting to do these tests, and you guys were the motivation. I can sleep better knowing that some of the stuff I have done is worse then I thought, and some better then I thought. Ha-ha.

If it wasn't for you guys being honest, and sharing what is modern practice, and currently going on. I would never have done it.

Again thank you guys for taking the time.

Sincerely,


William McCormick

[59halfstep]

Thank you Bill.:drinkup:

[Sandy]

William, let me throw this at you. You might be cheating yourself a bit doing an 'equal leg' test between an arched gusset and a straight gusset. I don't believe it is the purpose of the arched gusset to replace or compete with a traight gusset, but rather extend the legs and strength against forces further along the leg of the member towards center and beyond that possible with a straight gusset without encroaching a great deal more on the open area. In short enhance what a straight gusset is capable of by extending the legs not just cutting an arc in any particular gusset.

Knowing the above is terribly muddy, let me try describing it another way. If a 8" straight gusset is proposed with fairly long support members, then perhaps it could make things a bit better by designing an arched gusset with 10", 12" or even 14" legs with the center of the arc extending no more into the open space than the 8" straight would have.

Wish I knew how to draw and post then I would. I'm thinking you should be able to overlay an arched gusset over a straight gusset and it would occupy more overall space, not less, but the diagonal distance from the corner would be no more than the straight. Not the most efficient use of materials, no, but maximizing the use of a gusset while trying to minimize on the encraochment of free space??

Dunno, just my thoughts.

[farmersamm]

Sandy, I think you're talking about a chord.

A line between the innermost part of the arc, and the leg. With the toes of the arc extending beyond the chord. 8" gusset with toes maybe out to 10" to compensate for the chord, and allow a true straight 8" line of force

[Sandy]

Sandy, I think you're talking about a chord.

A line between the innermost part of the arc, and the leg. With the toes of the arc extending beyond the chord. 8" gusset with toes maybe out to 10" to compensate for the chord, and allow a true straight 8" line of force

Thanks Sam, I'll have to do some homework on the terminology for sure. :)

[farmersamm]

Like this I think??

[farmersamm]

Samcad:D

[Sandy]

Like this I think??

Exactly like that. :)

If that was a giant weld bead the diagonal distance (45º) from the corner out would be called the throat? So what is it called in gusset language?

[Sandy]

Sorry about derailing pilebucks original point but just wanted to get this out there then I can let it go. After about a half hour of screwin with visio then paint shop here's some pics of what I was trying to convey.

An arced/arched gusset needn't be used to replace or compete with a straight gusset, but could be used to add strength where it is possible to utilize them:

[farmersamm]

Exactly like that. :)

If that was a giant weld bead the diagonal distance (45º) from the corner out would be called the throat? So what is it called in gusset language?


I dunno:confused:

All this tech crap is causing major malfunctions in my noodle:cry:

Stress vector sounds good:cool: Saw that somewhere. Makes ya sound professional, because nobody on God's Green Earth knows WTF you're talking about:D

[Sandy]

Should do like sam and draw it on paper then snap a pic. It would be a heck of a lot easier and quicker too. This digital drawing sucks.

[farmersamm]

[SIZE="5"I DON'T THINK SHE KNOWS EITHER, BUT SHE SURE LOOKS MAD[/SIZE]:laugh:

[farmersamm]

I better call it a night Sandy

Been really weird since the pup died. Weirder??

[Sandy]

I better call it a night Sandy

Been really weird since the pup died. Weirder??

Have a good one sam. :) You lost a partner. It takes time.

[William McCormick Jr]

I noticed on heavy machinery that if they fish plate or double sections on the boom or stick that they run their welds out an inch or so as your describing. Usually on sections that end with a point or diamond shaped.

Was told by a welder that it helps reduce stess at the edge of the plate.



Good, interesting thread.:drinkup:

That is old welding tech. Some guys that know it today, won't do it on jobs anymore. Because it starts all kinds of questions and debates.

How does the engineer or architect explain some of them like that and others not like that? Ha-ha.

On ships every single weld had to be ground to fresh material years ago. There was no depressions left next to a weld. And no weld not ground to fresh material.




Sincerely,


William McCormick

[pilebuck]

Heard a funny at work the other day made me think of this thread:) "Engineers dont design things to be as strong as possible, they design things to be as strong as they need to be for the least amount of money, otherwise we would still be building pyramids."

Some really good points have been brought up on this thread as well as some excellent videos. Bottom line is in each situation someone has to make a judgement call taking into consideration factors such as intended application, ability to fabricate, ease of instillation, cost of raw materials, cost of labor, shipping, corrosion resistance etc.