DIY I-Beam for pergola

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I have a pergola with about a 16' span between posts in one section.  One winter night I went to bed with no snow on the ground, when I woke up 8 hours later we had 18-24" of some heavy snow.  All of the weight transferred to the one beam and it is now bent.  A couple of years ago I tried to straighten it a bit (only straightened it around 1/2"), but it has sagged over time.  Oh, forgot to mention this is a vinyl pergola, that has a steel infrastructure.  The overall sag is probably 3" in the middle.... but there was always about a 3/4" sag in it from the beginning.Anyway, the current beam is composed of 3 pieces.... all C shaped channel... Not meaning standard C-channel, just trying to describe its overall shape. 2 - 8' pieces span the 16' and then there is another 8' piece, slightly smaller, that slips in between the other two pieces, bridging the location where they meet up (basically the weak point).  I would have to look at it, but I think it is 14-16 gauge material (roughly 1"x16" when all placed together).Anyway, I was thinking about pulling out the bent material and replacing it with a homemade steel I beam... or in this case I guess an H-beam.  The material I have to work with is 2' x 4' steel plate (and thinner, IE 3/16, 10 gauge, and thinner).  I though about slicing a 2x4 1/4"sheet up into strips to create the 5.5"x16' web (will have to weld them together end to end of course), and then just using 1/4" x 1" strips as the flanges.  I was thinking about stitch welding them and using that.As this isn't structural (such as holding up a house), other than carrying occasional snow loads, I was wondering what you guys think.  Overkill?  Anything I should be aware of?  I would think the 1/4" beam would be able to take a much heavier load than the 14-16 gauge c-channel.One other thought, since I have a CNC machine, I was thinking about maybe adding a 1/2" curve to its overall length in the other direction (so I wouldn't have a sag in it at all over that distance--at least that is the thought).This pic is about as close as I can find.  Move the center "web" to the right side and get rid of the perpendicular piece in the middle and that is what the steel core looks like in the beam currently.  Of course, this is basing it off of a memory from about 5 years ago when it was installed.  Pics later if I can find the time.The pic of the pergola was taken before the snow storm (probably 5+ years old).  You can  see the slight sag in it as mentioned previously (beam on the far end).  While the beam in the foreground has 3 posts, the one in the background only has the 2 at either end.  Add another 1.5-2" sag in the middle and you can see what I am talking about. Attached ImagesLast edited by jdh239; 05-23-2013 at 07:05 PM.The Lord has declared, "This is my work and my glory--to bring to pass the immortality and eternal life of man"  Moses 1:39Link: My name is John, and I am a member of The Church of Jesus Christ of Latter-Day Saints.-- ColdCreekWorks.com --
Reply:The shape of the beam I'm picturing would be kinda floppy with such small flanges.If it were my project, I'd see if I could slip a few pieces of unistrut inside that PVC sleeve instead.  I think it would be more stiff, and weigh less.
Reply:I'd stick with Ali, Steel inside the plastic will get moisture inside the plastic and rust like crazy.You may be better off doing a double wall I beam meaning two verticle sections and two horizontal sections. with the verticals spaced inside the horizontals to make a ][ shape. Bringing the verticals in from the edges of the horizontals will reduce the friction when you're trying to slip the plastic over the beam. Also, the ][ shape will allow you to stager the joints in the vertical members as well as the horizontal members reducing the possibilty of failure at a joint.There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger
Reply:Add a center support to reduce the span.
Reply:Originally Posted by ezduzitAdd a center support to reduce the span.
Reply:Go buy an 8" or 6" cee purlin and paint it whiteAnd replace the bent "beam"
Reply:Originally Posted by AMC724Go buy an 8" or 6" cee purlin and paint it whiteAnd replace the bent "beam"
Reply:I measured again and the dimensions are closer to 1.5" by 5.5"As the cross beams resting on top of this are all screwed in, I don't think there will be an issue with it being floppy (from side to side).I may give it a shot here soon.  Maybe Monday if I can complete a bike rack project for a neighbor tomorrow.The Lord has declared, "This is my work and my glory--to bring to pass the immortality and eternal life of man"  Moses 1:39Link: My name is John, and I am a member of The Church of Jesus Christ of Latter-Day Saints.-- ColdCreekWorks.com --
Reply:Well, pulled out the old beam today.  Metal was pretty hammered and bend.  Didn't reuse it.  Created the i-beam with a slight convex to it (maybe about 1/2" overall) so that when I reinstall it the beam will hopefully look straight and no curve.I will have to complete the project tomorrow, but here are some pics from today.Cut the web on the CNC.  Plate markered numbers into each section so I assembled it correctly for welding.  If some of the welds look "crooked", it is because of the way I cut the parts.  I cut some notches in the ends to help line things up.  Video on it later... maybe tomorrow. Attached ImagesThe Lord has declared, "This is my work and my glory--to bring to pass the immortality and eternal life of man"  Moses 1:39Link: My name is John, and I am a member of The Church of Jesus Christ of Latter-Day Saints.-- ColdCreekWorks.com --
Reply:Here it is... finished a few days ago but just pulling pics off now.Far beam is the one I fixed.Before fixing it it dipped down in the middle 4-5" Attached ImagesThe Lord has declared, "This is my work and my glory--to bring to pass the immortality and eternal life of man"  Moses 1:39Link: My name is John, and I am a member of The Church of Jesus Christ of Latter-Day Saints.-- ColdCreekWorks.com --