Angle Beam
Angle Beam
(OP)
I have to calculate maximum shear for an angle beam of 44W steel.
The setup goes that its actually a sliding bender applying a "moment" onto my beam. The bender has a "Travel" distance I'm trying to find the worst case scenarios where the tension would create the largest stress on it.
Anyone have a few tips of how to start this, thanks.
Mat
The setup goes that its actually a sliding bender applying a "moment" onto my beam. The bender has a "Travel" distance I'm trying to find the worst case scenarios where the tension would create the largest stress on it.
Anyone have a few tips of how to start this, thanks.
Mat






RE: Angle Beam
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BA
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RE: Angle Beam
Ok so this is the "real setup" on the sketch, the pulley has a travel distance it slides on the beam, the beam which it slides on is the one I'm analysing, basically I want to start by analysing it completely horizontal (neglecting the fact its at an angle in reality)
I understand the "sliding" strap bender generates a moment because there is a force going up and a force going down.
I will post another hand made sketch of how I want to start by analysing it to have a basic understanding before going anywhere specific
Thanks guys!
RE: Angle Beam
or the two little angles that attach the slider to this beam ?
that looks like a motor, belt driven ?, sitting on the "slider" (which might function at a belt tensioner ?) ?
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Basically the beam I'm analysing is fixed at both ends, and my understanding has it that we are applying a moment force to it because the bender has tendancy to "spin"
Thanks!
RE: Angle Beam
No I'm analysing the angle beam just above the one with red Xs!
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then do some more positions, look at the two extreme positions and one in the middle, to see how the reactions change.
at each position the loads will be applied to the beam at a different place on the beam, yes?
now you'll have several free bodies, calculate the bending moment, etc in the angle beam for each position, to arrive at the maximums.
are there two of these beams supporting the belt tensioner ass'y ? are they going to be equally loaded ?
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There are two beams yes, but I'm analyzing one side. So how do I go about finding the worst case scenario on the beams.
RE: Angle Beam
The belt force puts a moment on the beam. Is there also a vertical load from the conveyor?
The statics are not too difficult if all of the applied forces are known. Are there two inverted "V" beams, one at each side of the conveyor belt?
BA
RE: Angle Beam
The beam IS fixed at both ends it was hard to represent it as so but the "V" beam or angle beam is bolted onto the beam under it, which is bolted into concrete, the values as I said are for now unknown as the goal is to determine structurally, the maximum load this beam can allow to remain undamaged.
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BA
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BA
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RE: Angle Beam
So when I find the maximum "momentum" that can be applied at different points I can know how much that means in tension. (Correct or no ? )
Still looking for some starts on calculating the angle beam's resistance. Looking at some cases in diffrent books of beam loads. Unsure how to apply them correctly.
Thanks
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if the angle is stable in compression (thick flanges) then your limit belt tension is (fcy/calc'd stress)*(unit tension)/SF,
SF = Safety Factor
RE: Angle Beam
Also : fcy? and how do I calculate the stress your speaking of from your unit tension. These are the steps I'm confused with.
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yes, unit tension = 1kN, max moment in angle = 130kN.mm, reaction = 0.44kN.
ok, good, now wiki "bending stress in beam" or something like, or find a strength of materials text. you're looking for something like stress = My/I.
something to consider is that your applied moment isn't along a principal axis of the section, you should be able to find that too (wiki or texts).
you should be able to determine the principal axes of your angle cross-section (the quick answer is the minor (weak) axis is through the mid pts of the two legs of the angle, the major (strong) axis is normal to this, thru the elbow of the angle (this includes several simplifying assumptions). You applied moment will be broken into two components acting along the principal axes and resultant stress = M1*y1/I1 + M2*y2/I2.
good luck !
RE: Angle Beam
I understand what you mean with the component moments and having the angle in this position was one of the challenges I realised.
Since we're using a unit tension, where does it come together that I have the official 'max value' if my calculations are based on arbitrary values.
Thanks
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Beam moment varies linearly from 0 to -Ra to Rc to 0 at left support, first F, second F and right support respectively. In the above, a is distance from left support to first F and c is distance from second F to right support.
This is elementary statics which you should know if you are making these calculations. I think your employer will require the services of a structural engineer if the results are to be sent out to customers.
BA
RE: Angle Beam
and you know your maximum allowable stress (fty, fcy) and the SF you want in the design.
so you can factor the unit tension up untill the internal stress calculated equals the maximum allowable ... T = Tu*(allowable/stress)/SF
you can calc the maximum moment on the beam, draw a moment diagram. you'll see it starts at zero (pinned ends), increases to a maxmimum, drops where your external moment is applied, and increases again. 1/2ing the external value applies when the load is introduced at the mid-length of the beam; different positions will produce a higher beam moment.
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Ya basic statics I am still learning, I see it becomes very elementary for guys like you which is nice to see. All of you have been very helpful I'll be crunching up some more with your help!
Thanks a lot
Mat
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The sketch including moment calculations only represents the "sliding part" on top of the main beam. Basic statics I guess again, but is it more logical to represent the reactions calculated on the top part in two forces on the main beam or is it "ok" to represent the same moment on the beam as another ponit moment.?
Basically what makes the setup easier to analyse, because on the slider it generates a moment on the "center point" for rotation, but on the main beam the slider's position creates a punctual moment in different points.
Thanks
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it should actually slightly reduce the peak moment, ie using the moment is conservative for the beam bending moment.
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To calculate end reactions on the beam, it makes no difference whether you consider a "point" moment or a force couple. You must use a couple if you want to draw the beam moment diagram correctly.
What is a "punctual" moment? A moment which is on time? So far as end reactions are concerned, the position of the point moment (or couple) makes no difference to the end reactions of the beam but changes the shape of the bending moment diagram.
By the way, you should draw the shear force and bending moment diagrams of the beam for a clearer understanding of the problem.
BA
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Think I've got it nailed down a little better now, thanks for the support guys!