Angle Beam 1

[Plastickmat]

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

 

[JedClampett]

A sketch would help. I can't figure out what you're talking about. But there are smarter people than me on this board.

 

[MiketheEngineer]

Yes - sketch please

 

[BAretired]

Yes, a sketch would be good.

BA

 

[Plastickmat]

Making one at the moment!

 

[Plastickmat]

Just a little insight on me, I'm currently working for a company as a student they give me little projects but don't have much time to help me with them I'm a little stuck on this one help would be very appreciated.

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!

 

[rb1957]

you're looking at the pieces with the red X on them ?

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 ?) ?

 

[Plastickmat]

Here is the "sketch" I made showing where I want to start at the basics!


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!

 

[Plastickmat]

Hi Rb1957,

No I'm analysing the angle beam just above the one with red Xs!

 

[Plastickmat]

And no it is not a motor sitting on it, yes the assembly is a belt tensioner but it is just a pulley, the drive assembly is separate, this part adjusts the tension on the belt by moving the pulley up and downwards a little like some bend pulley's in vehicule driven accessories.

 

[rb1957]

the 1st thing to do is to draw a free body diagram (wiki that if you have to) showing all the belt forces for one position, and calc the reactions at the ends of your beam.

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 ?

 

[Plastickmat]

What were trying to find out in our scenario is the maximum tension this beam will allow before failing. Basically I don't have a value for the tension available, but we need to rate the maximum allowable tension for this ass'y on the plans sent to the company using it.

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.

 

[BAretired]

The beam in the sketch is not "fixed at both ends". The only corner visible on the right appears to be hinged. The left hand boundary conditions are unclear.

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

 

[Plastickmat]

@BAretired,

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.

 

[BAretired]

Plastickmat, you have a different definition of "fixed" than I do. Fixed means the beam is not free to move laterally, vertically and is not free to rotate. I doubt that your beam is prevented from rotating.

BA

 

[Plastickmat]

I might have a bad conception, and please correct me if I do, but the beam is "bolted" onto the lower beam, which I realise is not the same as 'FIXED' in structural terms.

 

[BAretired]

In any event, it is conservative to consider the beam hinged at one end with a roller at the other. Then calculate reactions and find maximum shear and bending moment.

BA

 

[Plastickmat]

After putting some thought (as this is new to me) I agree on the conservative nature of such an approach. But I'm still stuck at the same step, what are the first steps involved in this when you want to work backwards? (Knowing the maximum force the beam can take at anypoint)

 

[Plastickmat]

I did a simple calculation to find a proportion of the moment transfered to the beam with respect to the tension felt ( Set as 1 ) which is why I consider it a proportion.

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

 

[rb1957]

why not use a unit tension, 1000 lbs ? 100 lbs ??, and calc a bending stress in the angle.

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