OT: platform needs to be put back together

[Sberry]

If I was doing it I would weld it up full pen, grind flush and lay a couple flat bar straps along the bottom flanges just a little wider than the flanges and weld lengthways down each side. Maybe throw another flat across the middle if I got paranoid. Be neat and no one will ever notice it has been repaired. A really good repair isa one you cant tell its been worked on,,, sometimes its a shame to hide our best work,, ha

[aametalmaster]

Right Hawk....Bob

[Pile Buck]

Hey glockdoc, just be careful, and maybe check into buying / renting a harness. Friends of ours, her parents own the local Chevy dealership, and he works there as well, anyway years ago they owned an A frame house, he decides to re-roof it himself. He doesn’t want to rent ladder jacks or anything for that matter! So he ties a rope to the bumper of his Volkswagen bug, climbs up one side of the roof ties the rope around his waste and repels down the other side to work on his roof. This works really well. Now this goes on for a couple weeks and he is very comfortable working like this. One Saturday afternoon his wife comes out of the house, tells him she is headed to town, does he need anything? Nope! Yep you guessed it, she takes the bug, drags him up the roof, with him just screaming, but she doesn’t stop until he has been drug down the driveway a little ways! So be careful!

[glockdoc]

Pile Buck, thanx for the input. i am in the process of getting set up to reside some rental property, a couple are two story. as a slumlord I couldn't afford to pay full price for one of these platforms, don't think OSHA will be a problem, maybe the City that the disgruntled neighbor called because I wouldn't sell her the house. I stopped by the recyling center the other day and asked the guy if he had any scrap al that I could make a platform with and he pulled out this set that he had been saving. Not sure if he was thinking of welding it back together but i sure was when I saw it. So far i am into it for $1 per lb. Hopefully, it it ever fails it will be gradual and the rope around my waist will also save me. Just need to keep the cell with me to call the fire dept to get me down. never did like yelling for help, it's embarrassing and the neighbors laugh at you. Hey, i wish I could say this was a test but I am probably now no more of an engineer than anyone else on this board. kind of sad to go to school for four years and then not use the degree to earn a living, especially when I think of how hard it was for me to get it. But at least I can now work on my own cars.

[Pile Buck]

I am a mechanical engineer.

SO, was this a test! LMAO!

[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.

[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.

[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!

[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

[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.

[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.

[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!

[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]

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?

[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.