Bending Flat Stock To Form Polygon Then Weld

[meadow street]

This is an interesting decision I have to make regarding the bending and welding of this polygon (attached).

100-130 mm flat stock x 6-10mm thick mild.

Where would you weld it shut? where would you start? Does it really matter?,

and as an aside, are welded joints (properly executed one or two pass both sides) stronger or less than a bend around?

We could go into a lot of detail about fitness for purpose etc but just wanted an opinion as a starter if someone had the time.

It's a component from a shed design which I will show a struct engineer ( maybe someone on this site if they are interested enough ?) can you guess where it will go?

cheers for now!

edit: those measurements are mm (courtesy of my cad loving surveyor friend)

backbround: furniture maker, developing welder, budding shed maker.

[simonl]

Hi there,

Wouldn't really know about the strengths of welds V's bends but I'm guessing it would depend on the nature of the forces applied & directions oh and the intended end use (which I equally have no idea of). I'm just impressed with your intended dimensional tolerances! :U

Simon

[Steamwhisperer]

Just off the cuff I would say weld at the 120 deg. It's easier to weld from both sides at that point.
Strength should be the same if done properly. Strength also shouldn't be an issue if this has been designed without any gussets.
Yup, that's about all I got :D
Oh, and welcome to the forum :)

Phil

[simonl]

How rude of me! It's your first post.
A BIG WELCOME FROM ME TOO! :B

Simon

[meadow street]

cheers,

i live in the country where sheds are practically everywhere.

Some of the designs i see for truss to column connections for tubular pipe frames are attached below.

my slightly modified treatment of the juncture (pictured also) allows for eaves overhang and fascia attachment via cleats.

i would like to add stub locators to the faces and then weld on the ends once aligned.

after looking at buying a bender etc, i will probably have the prototype bent at an engineering shop, unless someone here wants a project? hint hint.

gussets may have to be welded yet, not sure....any retired engineers want to get involved? :;

the connections will be seen by anyone who comes to the shed /showroom so like to have it neat but still old school if you get my drift. there were so many great sheds built strong and not "blow away" that I'd like to carry on the tradition.

anyhow great site......been lurking for a few months z

[RayG]

I'm assuming the bends are on the flat, so in that case I'd just heat and bend to the angles, layout the shape on a flat surface and fix in position while establishing the angles.

If you had to make a number of them, it would be worth making a jig. Only one corner needs to be welded, doesn't matter too much which one, but as Phil suggests the 120 corner is a bit easier to get welds on both sides..

I'm curious as to where this fits into a shed construction? The shape won't have much rigidity, triangles are the key to rigidity... :)

Oh, and welcome to the forum!

Regards
Ray

[nearnexus]

This is an interesting decision I have to make regarding the bending and welding of this polygon (attached).

100-130 mm flat stock x 6-10mm thick mild.

Where would you weld it shut? where would you start? Does it really matter?,



Yes it matters a lot.

For starters you should not be joining or welding the polygon at a corner.

To avoid distortion you should butt weld (double sided) at a neutral position midway between two corners.


Cheers

Rob

[Grahame Collins]

Welcome to the mob Meadow Street.

As a metal fabricator I can't picture the item being bent as a single unit in a fabrication sense. It is not really practical to bend in one piece with any standard equipment found in the average engineering shop. Possibly with a special purpose made bender,though economy of scale might change that.

What about 2 bent pieces welded at 120 and 60 degrees. Much easier and quicker to fabricate. If gusseted, these need to be welded anyway.

With 2 pieces or more it lends it self to tacked and /or welded in a jig/fixture.

[nearnexus]

I'm not an engineer, but just looking at the design, a polygon is not very rigid, as there is no diagonal support.

That's why triangulation is used,

You could in essence just use a triangle with a vertical riser comming off of the lower left corner , using the roof bearer as a stressed member and have a stronger, easier to make unit.

The whole poygon idea is not great engineering in my view.

Rob

[Oldneweng]

I'm with you on this one Rob. What size shed are we looking at here? There are easier and cheaper ways to do it. Do I hear an echo somewhere?

You could just as easily extend the top pole as per the last picture, with the design in the first picture. I cannot see any difference with doing this except for the better structural method of picture one.

Dean

[meadow street]

thanks for all the responses

i have lots and lots of 48mm od black pipe at my disposal.

shed will be:

10-12 m span

3-4m bays over 28-30 m.

perhaps Dean the pic below might be something for me to focus on ?

i guess I liked the angles of the polygon because the pipe ends would weld at 90 degrees...

I am adaptable though:U

[nearnexus]

How well the shed is designed ultimately depends upon the planning and inspection process in your area.

It varies between country/city/various states.

If you require approval and inspection then you will need to use an approved design and dimension specification.

So best to run the end design past the local council engineer to see if it is acceptable.

Even some of the older designs (eg series angle braced between twin bearers is no longer approved in the original dimensions - ridiculous.

The fact that the sheds have stood for near on a century seems to be irrelevant. So even buying secondhand trusses can be bad news.

Cheers

Rob

[bob ward]

Meadow street, that last pic you sent is a much better way to do the connection than your polygon idea. Its a far stiffer joint, and you do need maximum stiffness at that point.

[Oldneweng]

thanks for all the responses

i have lots and lots of 48mm od black pipe at my disposal.

shed will be:

10-12 m span

3-4m bays over 28-30 m.

perhaps Dean the pic below might be something for me to focus on ?

i guess I liked the angles of the polygon because the pipe ends would weld at 90 degrees...

I am adaptable though:U

You must have lots of pipe to build that big. :o Wish I had that much. :~

That pic looks good to me but then I am not an engineer. :no:

What are you cutting the pipe with? A dropsaw or bandsaw could be set for the angle and used to cut all pieces needed at that angle in one go then have the angle reset.

Dean

[BobL]

In your latest design the roof will push the walls out.
Structures are usually stronger, especially in corners, if the forces push the building together.

This is one way of doing it, also it's very simple.

http://www.woodworkforums.com/attachment.php?attachmentid=286241&stc=1

[.RC.]

Here is how I connected the truss to the leg on my latest extension..

[GTVi]

When designing these types of shapes, I make my angles either 120 or 60 never 90 degrees....that way you can insert 60 degree triangles neatly within your shape. Giving you the triangle structural support that you need. It also means that you can then use pieces of steel of various lengths bent at 60 degrees to weld your shape together.

[Karl Robbers]

In your latest design the roof will push the walls out.
Structures are usually stronger, especially in corners, if the forces push the building together.

This is one way of doing it, also it's very simple.

http://www.woodworkforums.com/attachment.php?attachmentid=286241&stc=1
Really only an issue while assembling the portal frame, many portals are assembled using that mitre type joint.
On that subject, do not paint the faces of the mounting plates that will mate together, you actually want rust to occur at this interface as it increases the joint strength.
For ease of construction, I would construct a column with a 90 degree top plate angle and bolt your truss between the columns. Your fascia purlin and girts are then all mounted off the column.
The flat bar polygon connection design would best be committed to the round file in my opinion.
By the way, a 30 degree pitch as the original design suggests is damn steep, you may want to have a look at that.

[Oldneweng]

That is a new idea to me Bob, but then as I said I am not an engineer. My shed is built to your design but there are joints like Meadow Streets designs on sheds at work. These are made from about 600mm I beam tho. I remember the design because it is in a section that has a higher centre section and can be seen easily from the next section which is full height and width all the way up. Very obvious construction.

286248

All done with only I beams as per the drawing design from Meadow Street. The centre section would be about 12m, similar to MSs span.

Now back to the reality of 48mm black pipe. Its all a learning process.

Dean

[meadow street]

this is part of my respose:

Hoping to get the planning and inspection people on side with the heritage ticket. Recycle reuse and repurpose being another. might work?

Nundle is a gold mining town and many of the original building have high pitches, some to 45 degrees or more and I would like to go with 30 degrees if possible. maximum solar gain here is 30.0263 degrees or something. great for solar on the north side !

getting the aged hardwood loading dock, verandah posts and exterior visible gable supports through might also test this theory, but we'll see.

a supportive struct engineer is a must.

thanks Rob for your warning of new standards for old designs.

[meadow street]

thanks for encouragement bob ward and bobl I will consider your tweak on the plate angles.


I was very happy when I stumbled across 30 degree pitch GTVI.

Took me a while to realise that I didn't have to set my drop,saw at 60 degrees (impossible) but rather at 30 degrees off 90.


Karl robbers, thanks for the no paint tip ! I had that written in the journal from another reading/researching jaunt i had a while back.......in fact a boiler maker from Newcastle reinforced that one too when he dropped into my shop.


love you to explain this though -


"For ease of construction, I would construct a column with a 90 degree top plate angle and bolt your truss between the columns. Your fascia purlin and girts are then all mounted off the columns"

can't quite picture it, but sounds good.


I,ve got about 100 pieces of the pipe in question.....eight per bay for the truss and column chords over seven or eight bays = 64 accounted for.


36 to bend up some heritage looking driveway double gates and a single entry gate and another entry gate.........leaving a few for ????.?.


and we are only of the knee joint ........with apex joint and haunches, base plate connections, diagonal bracing and plenty of other things to consider !


thanks for the diagrams and pictures too guys makes it very interesting!,,

[meadow street]

this is where the building will sit

[nearnexus]

In South Australia roofing trusses didn't have to be inspected after erection, but under new law changes they now do.

The standards/rules are always being changed and it's ridiculous to think you can pull down a shed with old specification purlins and beams, and not be able to put it up again under the new regs.

Council inspectors are not very flexible from my observations, and they will refuse to approve plans with a one inch difference from the current standards.

Rob

[Oldneweng]

this is where the building will sit

Very nice. Lovely backdrop in the distance. I have a lovely location as well but it is all flat around here. Your location is a bit too close to the road for my liking tho. We are about 100m away and shielded by bushy wattle trees etc. Heaven. Are you going to have access to 3 ph power? Not available for me.

Dean

[meadow street]

just dug the hole for the 3ph power pole to go in Dean.....lucky in that department so far (fingers crossed).

we'll test'em out Rob.

there's always colour bond and pre engineered flatpacks to fall back on: )

F know's what I'll do with all the rods (pipes)....we'll see.

more sketching for me to do now.

regards

[Karl Robbers]

Karl robbers, thanks for the no paint tip ! I had that written in the journal from another reading/researching jaunt i had a while back.......in fact a boiler maker from Newcastle reinforced that one too when he dropped into my shop.


love you to explain this though -


"For ease of construction, I would construct a column with a 90 degree top plate angle and bolt your truss between the columns. Your fascia purlin and girts are then all mounted off the columns"

I was assuming, perhaps incorrectly, that you were using steel columns.
What I was suggesting was to have the column/truss interface in a vertical plane, with the truss fitting between the columns. This means that your purlins, with the exception of the fascia purlin are all mounted on the truss top chord and your girts, assuming an enclosed shed, mount on the columns, with the fascia purlin, (this has both the roofing and the wall sheets fastened to it).
You could place the truss on top of the post, but this method requires some mechanism to prevent the truss wanting to flex side to side.
At a 30 degree pitch, you may need to cut the top of the post at an angle to gain the required clearances, the more typical lower roof pitches usually don't require this. I would also recommend some horizontal tension bracing in the gable, due to the fact that any deflection will cause quite a length increase in a gable truss @30 degrees, far more than a lower pitched roof.
How are you going to assemble your portals? IE can you bolt the truss and columns together and erect them as a unit? Or will you need to erect and plumb the two posts and then assemble the truss between them? Both have advantages and disadvantages.
Don't over weld your trusses either. Too much weld will cause more trouble than it solves and make sure you tack all the web in before you start to weld off the truss. Stagger the joins in your top and bottom chords to prevent potential failure points.

[meadow street]

you are reinforcing many of my other ideas, thanks!

i drew this sketch before you explained it again......pretty close?

cheers mate

[.RC.]

If the design has to be engineer approved, then probably you will have to go with what she/he says...

Hell I am surprised in this day and age the person doing the welding does not have to be approved as well... And the steel it is made from certified.. And as well the person building it has to be trade ticketed..

And you have to do a full environment impact study, a carbon emissions study donate $50 000 to the local council so they can give themselves a pay rise sign off on all your plans and studies and make sure no one within 500km is offended by your new shed...

Here it is a bit simpler... Anything 200m or more off the road used primarily for primary production is exempt from all the regulations...

In the real world does not matter what you do here, being so far away from the powers that be, they leave us alone...

[Karl Robbers]

Yep, that's the one. I tend to turn the connector plates 90 degrees, (so the bolt holes run along the truss, rather than across like you show, but that's no biggie). I would usually tend to mount my facia purlin (eaves) off the column rather than the truss, again no biggie. Yous seem to prefer quite an overhang on your eaves in your sketches. Is that to fit in with the general style of the area?

[nearnexus]

The other thing to consider is don't build your shed under/too close to an ETSA power line.

They are very strict about access issues in SA.

My Bro in law put a car port/open extension on the side of one of his sheds and ETSA made hime take it down as it was too close to an overhead power line.

Lots of rules/regs/snags these days.

Rob

[Oldneweng]

The other thing to consider is don't build your shed under/too close to an ETSA power line.

They are very strict about access issues in SA.

My Bro in law put a car port/open extension on the side of one of his sheds and ETSA made hime take it down as it was too close to an overhead power line.

Lots of rules/regs/snags these days.

Rob

They were obviously concerned about it growing up and interfering with the lines.:D What annoys me is when they cut down or trim trees that were planted or grew before they put the line in without thinking about it.

Dean

[Ueee]

What amazes me is what the pre-fab sheds get away with. Mine was as soggy as a wet wheetbix until it was all braced and had some sheeting on. Several of the frames tried to fold in half at the peak as we stood them up, as they only have a plate bolted on one side of the c section trusses. I had to add collar ties in as every time i got on the roof the trusses would sag and i'd have to jack them up again....

Cheers,
Ew

[gallegos]

Hell I am surprised in this day and age the person doing the welding does not have to be approved as well... And the steel it is made from certified.. And as well the person building it has to be trade ticketed..

...

Here it is a bit simpler... Anything 200m or more off the road used primarily for primary production is exempt from all the regulations...

In the real world does not matter what you do here, being so far away from the powers that be, they leave us alone...

If it needs to be engineered find an engineer who can sign it off and ask them to do the design based on your materials, then do the drawings yourself and get them to sign them off.

My understanding is that generally materials need to be new and the welding done by someone with a trade... but i wouldn't ask the council if this is the case directly instead find out what the general requirements are for building a shed and see what comes up.

I'm on a rural block a long way from town and no approvals at all required for sheds.. its great.

It has always amazed me how much the regulations vary between states and even different councils within the same state.

[nearnexus]

[QUOTE=gallegos;1699396

It has always amazed me how much the regulations vary between states and even different councils within the same state.[/QUOTE]

Very much tightened up in SA - seems to be ever since a (new) major golf clubhouse collapsed and killed a woman a while back.

Had timber beams/trusses that were badly engineered and made - from what I read. The large open/unsupported roof fell in.

Getting back to ETSA - in SA they inspect all country powerlines with a helicopter once a year according to the Bro in law (full on farmer), so any buildings and trees etc that are too close get the chop, one way or another.

I am not aware of a ban on using recycled materials, and the recycled building supplies do a roaring trade in SA. Once it's painted how would you know ?

Rob

[meadow street]

Thanks for all your thoughtful comments and words of caution and senses of humour.

If welding qualifications are required then I am happy to do the yards at "school" and sit the tests. Hopefully it won't be a waste of time since a lot of the theory is already instilled in the memory banks and a sound weld is something I can recognise and produce.

other regs will be followed too.

know any retired engineers/draftsmen who want a project?


regards and happy metalworking !

:cool:

[meadow street]

Karl ....like this you mean?

the overrun of the top chord in my sketches do give a more "building" look rather than a shed look in my opinion.

the other reason being that if the overhang is carefully considered it can allow northern winter solar gain and the higher elevation summer sun streams excluded through the building openings ( sliders or windows, clerestory etc).

there are some formulae for window placement and eaves overhangs with regard to latitude/longitude.

onwards and upwards through the red tap jungle I climb :)

[Michael G]

Hell I am surprised in this day and age the person doing the welding does not have to be approved as well... And the steel it is made from certified.. And as well the person building it has to be trade ticketed..


However, there will probably be a note on the engineer's drawings saying that all welds are to be to AS15xx (structural steel welding code). The person with the best chance of being able to weld to that standard is...?

Michael

[meadow street]

interesting reading the standard from Scribd (http://www.scribd.com/)

guess I should do that course.......

might see if there are any qualified inspectors in tamworth too who might come on board :wink:

[Karl Robbers]

Karl ....like this you mean?

the overrun of the top chord in my sketches do give a more "building" look rather than a shed look in my opinion.

the other reason being that if the overhang is carefully considered it can allow northern winter solar gain and the higher elevation summer sun streams excluded through the building openings ( sliders or windows, clerestory etc).

there are some formulae for window placement and eaves overhangs with regard to latitude/longitude.

onwards and upwards through the red tap jungle I climb :)
That's the one.
As regards AS 1554. It's been a sore point with me for some time that "all welds to AS AS 1554" is put on every drawing, yet so few people actually work to it. I have seen some atrocious welding on structural beams, don't even get me started on the welding seen on many kit sheds.
AS 1554 is a useless standard unless you comply with it, half the engineers don't even know what it means, they just know that you cut and paste AS 1554 in a little box on your drawings.
There are some really good engineers out there, but there seem to be a large number who couldn't spell engineer last week, but now they is one. Apologies to any decent engineers reading this, but I have come up against some real idiots, I could nearly write a book on them.

[meadow street]

I like your style Karl.

Thank goodness for local libraries!

The kind librarian just downloaded the standard, albeit a contentious one, to a memory stick for me.

At least I can read it and makes some notes.

btw as you can appreciate, I am doing all this to educate myself and hopefully save some money or at least spend heaps of money and educate myself : ) haha

do you want to hear some other questions I have?

do you want to see some other details, or is it too boring?

regards to all


meadow street.

[Karl Robbers]

Keep on plugging away Meadow, always good to see new ideas.

[meadow street]

How about adding a channel or two angles to the vertical connector plate before welding it to the pipe column ?


see atattached


Getting a good weld in the radius has always bothered me :C

Worth the extra effort for piece of mind?

ie fillets on the side of the pipe rather than in the tight radius which I find needs building up a lot .


i,ll attach the apex for consideration too while I,m at it

see below.

regards

meadow

[WelderMick]

How about adding a channel or two angles to the vertical connector plate before welding it to the pipe column ?
Getting a good weld in the radius has always bothered me :C

You can also use some reinforcing bar or just some steel rod - tuck that lengthways along the radius and weld stringers over the top.
286557

[Karl Robbers]

Round bar works well as Welder Mick posted, some also use a couple of pieces of flat bar each side. I definitely would not use channel for cost reasons plus you would find it hard to source a channel that would suit as a standard item.
I actually think that you may be a bit over braced with your trusses. This won't hurt but will add time and cost to your project.
If not for the fact that you have the pipe, I would always suggest other sections such as SHS or RHS. They are much easier to fabricate with and are a higher tensile steel while being cheaper into the bargain. Just a bit of info to put away for the next project.