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I need help selecting I beams for a ramp.

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  • I need help selecting I beams for a ramp.

    Ok here is the deal. I've got a building with a narrow dock ramp made of magnesium and it's in dis-repair I want to replace it with a wide ramp using 3 I beams but have no idea what size beams I'll need.

    The total span is 36' and I plan to put legs in the center for added support. The ramp will need to support the weight of a fully loaded 8000lb capacity forklift, but the primary reason for a wider ramp is to pull our sports cars in and out of the building since we are moving the machine shop over there.

    So if I use 3 I beams and a center support so the actual span is 18' on each side of the support what size beams will I need? I've looked in the machinist's handbook as well as searched on google but the math is beyond me at this point. I figure max weight on the ramp to be around 18,000-20,000 lbs. Can anyone help me?

    Also any and all necessary welding will be done by a certified professional welder. I'm not going to trust my skills on this one.

  • #2
    Can anyone help me?
    Sure. Pay a professional engineer.
    Free software for calculating bolt circles and similar: Click Here

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    • #3
      Here you go,follow the link and select the calculator that best fits your application then plug in your numbers.


      http://www.engineersedge.com/beam_calc_menu.shtml
      I just need one more tool,just one!

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      • #4
        Hire a professional engineer... the equations are simple but you have to know how to use them and what their limits are
        Good luck
        John R

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        • #5
          What's on top of the beams? You driving up on the beams alone?

          I can't afford the liability but I can tell ya that 20k over 18' is going to be one big-ass beam!

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          • #6
            20k lbs is 10 tons.. how is that spread? is it a point load, or how many axles.. you woul d need to know that, so you could get some idea as to how much support is needed in certain places. im sure your race car doesnt weigh 10 tons!! 36 feet.. your getting close to building a bridge..

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            • #7
              For me to get away with this I can't hire an engineer. Our forklift has an 8000# capacity, I figure it weighs at least 10000#. I need to be able to drive the fully loaded forklift up the ramp, heck my big lathe is 6000# and it will be moved into that building.

              I'm thinking 3 or 4 beams with cross braces. My brother suggested thinking about planks for a deck, not 2x8's or something he means planks like 4-5" thick bolted to the beams. Something like roughsawn oak.

              The current magnesium ramp is 35' long and in rough shape. I don't know it's capacity but judging from the welded cracks it's not very much. It's basically 2 C-channels with about 18" cross section. I'm thinking 3 12" steel beams with at least a support in the middle would do it. I checked the link that wierdscience provided and I'm not sure I understand the numbers as they are for deflection. There has to be a simpler formula for a load placed in the center of a beam but I can't find it.

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              • #8
                Christian
                It's not that no one can figure out the load, that is fairly simple.
                there are several members of this board that could do that.
                The problem is the span and the load you want to drive. the 10K lift truck with loaded forks, becomes a point load, not a evenly spread load. this usually requires twice the beam capacity.
                But the real issue is human life.. the fact that you are spanning 36 feet signifies not only a long span , but a deep one, or else you would be driving up and down small inclines.
                No one wants to be associated with that level of liability....even though you want to do it yourself.
                Think of what Clint Eastwood said in "Dirty Harry"..
                "A man has to know his limits"
                This 'bridge will not be a cheap item to make...and the best insurance you can have that it will be a sucess is to hire a professional engineer, or a structual engineer.
                If you are short of funds , the other resource is to go to a local college that teaches engineering and talk to the structual design professor.
                Rich

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                • #9
                  Now that I think about it should the beam supplier be able to tell me what size beams I'll need? My brother and father are mechanical engineers but getting them to actually engineer something for me is like pulling teeth. I did use the calculator provided in the link but it doesn't seem to show what size beam I'll need.

                  EDIT:

                  Rich, I do apprecate everyone's input and I know safety is an issue. I just thought it would be easier to figure out than this. The ramp is long so that it's not steep, forklifts don't have the best brakes and they have certain maximum grades they can climb. The total rise is to dock height, about 5 feet or so. Looking at overhead cranes I've seen in local factorys they put 2 tons on what looks like an 8" beam about 30' long. I think I'll search for a wider dock ramp first.
                  Last edited by rsr911; 10-03-2006, 02:05 AM.

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                  • #10
                    If you aren't going to have it engineered then my advice is to build it so freek'in strong that an M1A1 battle tank could drive up it. Build it so that it approximates a poured solid concrete structure. In fact, that isn't a bad idea, at least for a good portion of it.
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      I want to build something like this:

                      http://forkliftramp.com/model1030.html

                      Only I don't need the platform as I can just drive right in the door. Note the one pictured has no supports under the ramp section, it handles 30,000lbs and the I-beams used don't look to be more than 10-12". Looking at the pictures in the gallery they seam to be using 4 beams to handle the load.

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                      • #12
                        Originally posted by Evan
                        If you aren't going to have it engineered then my advice is to build it so freek'in strong that an M1A1 battle tank could drive up it. Build it so that it approximates a poured solid concrete structure. In fact, that isn't a bad idea, at least for a good portion of it.
                        Concrete was the first thing considered however we need to be able to move it to the rear of the building in the future and free up this dock door. The building is a former trucking terminal with 20 bays, all but two have been blocked up by the previous owners (a pallet recycler). At some point we'll need to use both dock doors so we'd move the ramp to the location of one of the blocked up doors and install a new door.

                        That's problem number one. Problem two is I simply don't trust the current dock ramp. And problem three, money. We've just laid out about $600,000 for the a bunch of new equipment as well as this building ($150,000 at 15,000 sq. ft.)

                        The ramp will take an 18,000lb load very rarely, maybe every few years. Most of the time it will be a lightly loaded forklift or our cars. The way I engineer things is to figure out what is needed then multiply by at least 1.5 even if I think a safety factor has already been added. I suppose I could just line up a bunch of 8-10" beams and weld it all together, slap on a deck and be done but what fun is that. I'll ask my metal supplier what he thinks.

                        I do appreciate all the concern for mine and other's safety and I will take it to heart. Perhaps I might get lucky and find a good ramp on the used market.

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                        • #13
                          Go buy a truckload of used railway cross ties and lay steel plate over them.
                          Free software for calculating bolt circles and similar: Click Here

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                          • #14
                            Can you post a sketch of the building and the relationshop of the ramp to the door etc?

                            How is the ramp to be used?

                            Does the ranp slope so that grade level loads can be forklift transported up to an elevated floor?

                            Are you working from a paved surface? What is the safe unit load bearing of the sub soil? The strongest ramp will do you no good if the pavement fails and the end of the ramp slowly sinks 10" into the clay as loads are transported over it.

                            Can the ramp have intermediate support over its span? You save a lot of money on big long beams if you break a long span up into smaller ones.

                            Does it have to be portable and forklift transportable?

                            All these questions arise to me but I find no answers in the discussion. There are many variables associated with these answers. Once your concept of the problem is fixed by statements of fact and accurate depiction, the loads, spans, members, attachments, and construction details follow almost automatically. As it is, you're asking us an open question like "how high is up".

                            The usual way ramps are constucted is the span members are spaced to suit the track of the vehicle using it. The vehicle in traveling over the ramp s directly supported by the span members. Thus the decking and the auxilliary members don't see any but incidental loads. The vehicle load is passed by compression through the decking to the span members. Auxilliary members are spaced across the span ladder fashion like a flat truck bed. They reansfer incidental cantilever load to the span members. Typically they are coped and welded into the structure and a toe rail meeting local code is placed along the outside edges of the ramp. Along this sockets are placed for hand rail stantions. The structure may then be decked with timber, grating, or plate.

                            A quick look at the site by an engineer will do no harm and his remarks and suggestions will be well worth a couple hundred bucks and a coffee shop lunch while a sketch is passed back and forth. Hell, his visit will save you that much in material costs alone in these days of $0.60-0.70/lb for A36 structural steel.
                            Last edited by Forrest Addy; 10-03-2006, 03:30 AM.

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                            • #15
                              Forrest,

                              To answer your questions.

                              "
                              How is the ramp to be used?

                              Does the ranp slope so that grade level loads can be forklift transported up to an elevated floor?"

                              Yes, it will be use to transport loads from ground level up to dock level as the current is being used now.

                              "Are you working from a paved surface? What is the safe unit load bearing of the sub soil? The strongest ramp will do you no good if the pavement fails and the end of the ramp slowly sinks 10" into the clay as loads are transported over it."

                              The ramp will be placed on top of a pre existing reinforced concrete slab. The load bearing capacity of the soil is rather high as the property was a brick yard before it was a shipping terminal. There has been many (60+) years fo tractor trailer and heavy equipment travel over the area.

                              "Can the ramp have intermediate support over its span? You save a lot of money on big long beams if you break a long span up into smaller ones."

                              Yes, my original plan was one set of center supports, others could certainly be added.

                              "Does it have to be portable and forklift transportable?"

                              Sort of, at some point in it's life it will need to be moved sideways about 50 feet. A local rigger would be brought in for this when the time comes, they have the proper equipment for the job.

                              At first I thought this would be simple, it's becoming clear that it is not. I will talk with the ownership about bringing in an engineer. I don't think a hand rail is needed as the current ramp does not have one. This is not a pedestrian ramp.

                              My original idea was to use tamped soil/aggregate and thick concrete until I was told there was plans to move it in the future. I then considered widening the current ramp until I got a good look at it and realized the poor state of repair.

                              I've casually seen ramps like the ones in the link I provided and figured it would be easy to construct my own. My original concern was welding it myself until a friend and certified welder offered his services. Since he is already a structural welder I thought I was well on my way, only needing a good design. I will check into having an engineer look at the problem. Perhaps I may have to wait until funds are more readily available. My company has recently undergone a large growth spurt and cash will be tight until spring as we've had to invest in lots of new and used equipment to handle the new volume. We had hoped to move the machine shop next door to this building but I don't trust the current ramp to carry the load of our forklift and heavy machine tools. I suppose we could drive up to the other door and set the machines on the dock then drive only the forklift up the ramp. Then there is the problem of cars. My cars fit with small tires on them but my brother inlaw's car (he is the owner) is too wide for the current ramp. Maybe he's out of luck for now.

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