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Beam or Bar joist reinforcement.

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  • #16
    Take your pick, which one is stronger?
    I have no idea!
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    • #17
      Forgot this one!
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      • #18
        Originally posted by vin-man welding View Post
        as to the other part of your question, i think it was a question. reinforcing bar joist: I've had to run 5/8 round stock to the four corners of the angel iron this keeps the angle from twisting and letting the bar roll over or bending.
        I've also had to run angle iron top to bottom next to the the center supports to make it handle more load. did i mention 15+years of structural welding.
        Portable Welder: did you miss this one, i gave the answer befor the question.

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        • #19
          Originally posted by Portable Welder View Post
          OK from what it sounds like judging by what Enlpck, S Berry and vin man have said, and correct me if I'm wrong.

          Its stronger to add metal to the top and bottom flange of a beam instead of putting a plate in the webb area.
          Next question, Does a H or I-beam work the same way as a Bar joist.
          Meanining, Is the top flange under compression and the bottom flange under tension.
          And how would you reinforce this, would you add material to the flanges or would you run a plate standing on end betwen the upper & lower flange.

          Keep in mind there would already be proper X bracing installed along with the typical 1" angle running across from joist to joist and the beams are being reinforced to carry the load of a bigger RTU- Roof top unit.

          So what do you do in this situation to reinforce this beam.
          no it's the other way, load is webb and side load is flange. but plating the top or bottom will increase the vertical load at the point of inertia.

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          • #20
            Originally posted by vin-man welding View Post
            but plating the top or bottom will increase the vertical load at the point of inertia.
            Huh?


            Originally posted by vin-man welding View Post
            no it's the other way, load is webb and side load is flange

            v-m, for the vast majority of situations where a horizontal beam carries a vertical load, the web is NOT the limiting factor. Yes, the flange is what provides resistance to bending under side loads, but this is because the flange is the part that has material farthest from the neutral plane in side load (neutral plane: the plane through the material where no stretching or compressing takes place in bending). The material farthest from the neutral plane (the flange for vertical load in the original example) undergoes the most stretch/compression, and is therefore under the most stress, and is most important in carrying load in cases where shear isn't dominant and there is sufficient bracing to prevent buckling.

            Portable-Welder: the load distribution is generally the same with a bar joist and a beam-- the load top is under compression and the bottom under tension in both-- but the bar joist is much less stiff against side load and buckling to the side. I would STRONGLY suggest getting and engineer to evaluate a situation like this and provide details. That is what he is paid for and why he carries insurance. Each situation is different.

            In the first case you described, I would guess that the solution would be a) replace the joist with a heavier one, b) reinforce the joist by adding material at the top and at the bottom, or c) (most likely is the capacity and space are there, as it is easiest and cheapest) run W-beams ACROSS the joists to spread the load over several of them, rather than one or two. Buckling is likely not an issue for any of these solutions if the cross bracing is sufficient in the first case, unless the load is quite large. In the case of an S-section (I-beam), not much is gained by reinforcing between the flanges in most cases, as they are fairly narrow and thick. In a W-section (H-beam; wide flange) the reinforcement greatly reduces the risk of buckling in longer beams, but is only one of several solutions. If the beam isn't too long relative to its size, it is of little use.

            In the second case, lots of options. A simple case: most likely would be a pair of columns, one to each side of the original, and a beam to catch load where the original was, if the column needs to move sideways. If the column needs to move along the beam, it can get quite complicated, in particular because small increases in span (say from 12' to 16', from moving 4') can require a much larger beam. The size of the beam needed goes up much faster then span for a given load, and can change the limiting factor from allowable deflection to load carrying capacity based on yield, shear, or buckling.

            For more information: See (among many others) _Structures_: Schoedek; _Strength_of_materials_: Den Hartog; _Procedure_book_of_arc_welding_: James F. Lincoln foundation; _Design_of_welded_Structures_: Blodgett; AISC_manual_of_Steel_construction_:AISC;

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            • #21
              Enlpck,

              You are correct, I asked the other person at the other message board to come to our miller site to see what some here would say.

              Unfortunately I could not convince the other person that adding to the flanges verses the webb was a much more common way to reinforce a beam or barjoist and to get the most strength for the amount of steel used.

              Sanora thanks for your illustrations, Thats how I have been doing it for the last 20 years.

              Enlpck,
              You are also correct about hireing an engineer.
              I have always done this off engineered sealed drawings.

              Even when I told the member on the other site that I have been doing so with different engineers over the last 20 years he suggested that my engineers were wrong.

              Hopefully when this other member, Which is also a senior member on this site as well will realize that maybe he was incorrect.

              There is also things such as transfering loads to panel points on bar joists that we had discussed.

              Incertain cases I have also had to run additional diagnal bars into the bar joist after adding to the top & bottom chords.

              Whenever pulling a load off a joist its important to grab from a panel point and if you cant I add an angle from the opposite panel point down or up to where the load is being applied to.

              Vin man, Take a look at Sanoras illustrations, All of those ways are how I have always did the reinforcement on joists and beams.

              If the strength was more about the webb verses the flanges a bar joist would never work.

              When ever you look at truck frames you will typically see holes in the webb and hardly ever in a flange except under certain situations.
              Its also important to always use round or oval holes in beams or truck frames.
              Square holes are very suseptable to tearing in the corners.

              Thanks for the input from all.

              I was also hoping to hear Body baggers formula and calculations.
              Last edited by Portable Welder; 02-25-2009, 10:24 AM.

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              • #22
                Originally posted by Portable Welder View Post
                he suggested that my engineers were wrong.
                Engineers?!!!!!!!!!!!
                We don’t need no stinking engineers!!!!!!!!!!!!!!

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                • #23
                  I've done some of the other bar joist reinforcing but mostly picture one is the way the Engineers have us do it.
                  so what can carry more load in the horizontal position?
                  a W-10x14 or a W-12x14 ???

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                  • #24
                    OK not a fare question. I'll give a beam that exists.
                    I beam 10 x 35, or a 12 x 35 ????

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                    • #25
                      All I have is an older book so some of the modern beams aren’t in it.

                      But a W-12x40 is good for 69,000 @ a 10-foot span.
                      A W-10x33 is good for 47,000 @ a 10-foot span.

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                      • #26
                        I like this if I can do it. http://www.millerwelds.com/resources...0&d=1235520223 Same goes for top.

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                        • #27
                          Originally posted by Portable Welder View Post
                          You are also correct about hireing an engineer.
                          I have always done this off engineered sealed drawings.
                          ?????? I generally work off coffee-shop napkins,,,, just gotta know which coffee shops to go to Of course, it is expected you pick up the tab, also

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                          • #28
                            Originally posted by Sberry View Post
                            I like this if I can do it. http://www.millerwelds.com/resources...0&d=1235520223 Same goes for top.
                            I like that one best also. Not to sure about the round stock one! But if an engineer spec it, who am I to argue.

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                            • #29
                              Originally posted by JSFAB View Post
                              ?????? I generally work off coffee-shop napkins,,,, just gotta know which coffee shops to go to Of course, it is expected you pick up the tab, also
                              by far my favorite method

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                              • #30
                                sorry, haven't been here in a while, and don't mean to drag this back up to the top but when it comes to stiffening a simple span beam for load bearing. Adding area - no matter what increases the section modulus thereby increasing it's load bearing capacity. Of course depending on where you add this material can affect it's efficiency. It is important to remember that on a simple span beam (a load bearing beam supported by two fixed end points) that the top flange is always in compression and the bottom is always in tension - this puts the neutral axis at just that - neutral.

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