OT: platform needs to be put back together

[glockdoc]

Picked up an aluminum platform (used on scaffolding) from a local scrap dealer. Looks like it has seen little use, my problem is that Bubba cut it in half to get it on the truck before he sold it by the pound. It's a Werner model 2020, 20' long by 12" wide, rated for 250lbs. Each I-beam is 5" deep, flanges are 1.25" wide, all 1/8" thick, I'm guessing 6061. I was thinking of tigging it back together but will need to do more to get the full strength back. The top flange will be in compression, so tig might be good enough for it. The bottom flange will be in tension, thinking maybe steel angle that's bolted or maybe al angle and then skip weld it. Anybody have any better ideas on how to get this thing serviceable again? thanx

[aametalmaster]

I would weld it with a spoolgun if you have one, but you have a tig that will work. Also i would make a plate to fit inside the flanges and bolt or weld it to stiffen it up. I would not use it anywhere there are OSHA regs on scaffold planks. Our company would frown on such use. But home use thats another story. Just be safe...Bob

[migmaniac70]

I think i would tig it,then grind it smooth on the inside,weld in a plate that goes over the weld on the flat then tig the plate all the way around,Then box in the beam on the bottom about 4 inches to each side. Probably over kill but thats what i would do and feel secure in using it,Because the middle of these walk boards is where all the flexing usually occurs. 20ft is a long span.So i would want to support the center where the cut was the best i could.
We bioth know those boards arnt cheap.So i would try to fix it too.

[glockdoc]

Thanx for the ideas, the boxed beam should work well. I'll only be able to box in the outsides of the i-beams as the rungs are fairly close together where it was cut, not much room on the insides. Also thinking of maybe some 3/16x1.5 flat on top of the bottom flange and then plug welding it in a few places. My only concern is the welding will soften the metal in the HAZ areas, plug welds may help that. Guess when I'm done I can set it up between two cinder blocks and then do the scientifically proven test of "jumping on it"

[dyn88]

you are right welding it will "soften" it or aneal it. bevel all joints to achieve 100% penetration then grind smooth to avoid stress risers. you should then bolt a plate that is 60% longer than high the same thicknes as the thinnest cross section. To load test place a weight three times the amount that the unit is rated for(this is an industry standard for shop union work)( I make platforms and similar irems for pratt and sikorski, and all the products are load tested at three times the rated load for one hour).use one bolt for evey 100% of the height and two at each end. Make sure to use locktight or lock washers.

[HAWK]

I think i would tig it,then grind it smooth on the inside,weld in a plate that goes over the weld on the flat then tig the plate all the way around,Then box in the beam on the bottom about 4 inches to each side. Probably over kill but thats what i would do and feel secure in using it,Because the middle of these walk boards is where all the flexing usually occurs. 20ft is a long span.So i would want to support the center where the cut was the best i could.
We bioth know those boards arnt cheap.So i would try to fix it too.

I think that's a great idea except for tigging the plate all the way around. It seems there would be less stress on the vertical run of the board if the plate is welded on two opposite sides running perpendicular to the original seam to be welded initially.

When dealing with reactive forces the final calcs can become confusing. What do the professional engineers think?

[INTP]

I keep thinking that in an I-beam that is over a span, the top piece is in compression, and the bottom piece is in tension. The webbing is just there to hold the top and bottom together. I like the idea of bracing the webbing, but I'd really focus on making sure the bottom can handle the tension force.

And for the record, I'm not an engineer, nor do I play one on the internet.

[HAWK]

glockdoc,

As INTP stated he is not an engineer nor will "play one on the internet". I am not an engineer either. My statement regarding the plate is a question rather than a recommendation. I am in no way saying to do this. That is why I am asking what the professional engineers think? Surely somebody on this forum does this type work for a living. aametalmaster has the best idea: be safe!

[dyn88]

I like HAWK and INTP am also not an engineer, I do build and repair a fair amount of this type of product. We make our repairs from prints supplied by the customer.

[INTP]

I dug out my copy of "Welding Fabrication and Repair" by Frank Marlow (who as it turns out, IS an engineer ), and it had something similar but not exactly the same. On p. 145, it covers a repair to a c-channel, as in a vehicle chassis. I encourage you to take a peek, but he shows a plate bolted to the webbing, and a lengthwise bar added to the bottom part of the channel. Instead of a plate, it is a flat piece that hangs from the bottom of the channel, and welded lengthwise (on both sides) to avoid a horizontal weld.

I know this probably makes no sense. He's better at explaining than me, and he has a cool illustration to show what he's talking about.

Anyway, if you can get hold of a copy, I think you'll find it useful.

[aametalmaster]

Hi guys, I don't want to speak for my dad but he is a mech. engineer and when i was working for him, i was taught never weld a vertical keep all the welds horizontal with the part. I never knew why but i didn't go to school either...Bob

[Pile Buck]

Hi glockdoc. I take it, as this plank is thicker in the middle than out at the ends? If so around here they call those banana boards. I agree with aametalmaster if you are going to use this board in any location where OSHA, either state or fed has jurisdiction, you will be on thin ice. If I were going to splice this thing back together, I would worry more about the flanges, top and bottom. If at all possible double up on the flanges. Then maybe add a diamond shape splice plate to the web <>. I worked side be side hand n hand with engineers. An example I was taught for a situation like this is. Take a yardstick, stand it up vertically, place a 2 x 4 under it at each end. Push down on the yardstick in the middle with your pointer finger, (real slow) What happens? The yardstick will roll off to one side, before it buckles! The trick is to keep things like this from rolling off to the side. So either box it, or build a horizontal truss, but don’t let it move to the side. Just my opinion!

[glockdoc]

How's this for a joke, I am a mechanical engineer. Only problem is I graduated 26 yrs ago and spent a grand total of 9 mo working as an engineer at a power plant right after school. Seems like these days I'm doing good to remember my name everytime I wake up in the morning. I was hoping to get the practical, real world experience input versus the "book answer" which I do remember is sometimes very different. The I-beams are extruded so 6061 would be a good guess, could call Werner to ask, wonder what they would say if I told them I was going to weld it back together. Didn't look it up yet but hard 6061 is maybe around 60k psi and the soft around 25k psi. Worst case, I should be able to double the thickness to get it back close to what it used to be. The top flange will be in compression and the bottom one will be in tension with the web keepimg them apart. The problem child I figure will be the bottom flange and it's approx 1/8 x 1 3/8. I plan on first jigging it up straight and square then tig it together to make it easier to work with. Then I was first thinking of bolting the bracing, maybe even using steel. Now I"m looking at using al maybe around 3/16 x 1.5 flat or even angle and then plug welding it along the bottom flange. i have always thought of plug welds as "welded bolts". Then box in the outside of the beams for a short section. I believe the al comes in 10' lengths so why not use a full piece on each side just to beef up the whole thing for the day that it will be overloaded. My next question is: for the plug welds, using 5/16 holes what would my HAZ be around each plug weld? Trying to get an idea of how far out the annealing will reach. Would throwing a wet rag on each weld get some of the strength back? I know that hardening 6061 is a different process/theory than hardening carbon steel, 6061 is heated, chilled, then age hardened. I've played with heating/bending some round 6061 and throwing them in a bucket of water, seemed to have some affect on rehardening. Thanx for everyone's input.

[HAWK]

Hi guys, I don't want to speak for my dad but he is a mech. engineer and when i was working for him, i was taught never weld a vertical keep all the welds horizontal with the part. I never knew why but i didn't go to school either...Bob

BOB,

SO WHAT YOU ARE SAYING IS BASICALLY THE SAME THING I WAS ASKING ABOUT AS FAR AS THE WELDS ON THE PLATE 2 SIDES ONLY PERPENDICULAR TO THE VERTICAL SEAM?

I HELPED A GUY BUILD SOME OVER HEAD RUNNERS FROM "H" BEAMS FOR AN INDOOR OVERHEAD CRANE ASSEMBLY. HE SAID WE HAD TO WELD THE SEAMS, THEN APPLY A "FISH-PLATE" OVER THE WELDED SEAM. HE SAID THE "FISH PLATE" COULD ONLY BE WELDED ON 2 SIDES KEEPING HORIZONTAL WITH THE PART. I LIKE YOU DID NO KNOW WHY. HE SAID IT HAD SOMETHING TO DO WITH OPPOSSING FORCES PULLING AT THE PLATE IF WELDED ALL THE WAY AROUND. I WAS HOPING SOMEONE COULD ELABORATE FURTHER.

[Pile Buck]

I am a mechanical engineer.

SO, was this a test! LMAO!