# Need to find the length and deflection of bending element

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1. Mar 2, 2015

### Mantas777

Hi,
I have a task and don't know the good solution. (I add the picture of my task.) I need to find the right lenght and deflection and to check if the results didn't exceed the allowable stress. I know the value of "q" (force). Also I could choose myself the lenght, but I need to check, if my choice didn't exceed the allowable stress. (The value of allowable stress I also know). But I don't know exactly, which stresses I need to find to compare them with allowable stress? (I hope I explain understandable)

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2. Mar 2, 2015

### PhanthomJay

Is this task homework related or job related or other? You apparently have a given beam material and size and end conditions and loading, and need to determine max length to keep stresses within allowable?

3. Mar 3, 2015

### Mantas777

This task is job related. I have a pipeline and I need to find the lenght and the deflection to keep stresses allowable. My pipe material is Steel ST 37,0. There is one old straight pipe, and we project 200m distance new pipe, and we install it from bottom. And from bottom we connect new pipe with old. We do the same at both side of 200m distance. So I need to find the lenght of that bending and deflection to keep stresses allowable. Pipe dimensions: Diameter DN 300 323,9mm, wall thickness 5.6mm. Also I had calculated already that one metre of pipe weight 43.94kg.

Last edited: Mar 3, 2015
4. Mar 3, 2015

### PhanthomJay

I am unsure of your particular task, but if you are just looking for moments and deflections associated with a uniformly loaded beam fixed at one end and free to deflect but not rotate at the other, then look it up in beam tables like
www.engineersedge.com/beam_bending/beam_bending13.htm
since you know loading and allowable stress and can look up properties of pipe, solve for L max. Deflection is what it is, presumably not controlling your design? I don't know if I understand the problem correctly. I certainly don't want to do your design.

5. Mar 3, 2015

### Mantas777

I add the better picture of my task. I need to find the length of bending (L). The deflection is about 1,2m, but it may change when we have bigger lenght or smaller. So I need to find the lenght (L) and to keep stresses allowable. I could do that by the 1 or 2 scheme, because it have to give me the same results. But I don't know exactly how should I calculate that.

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6. Mar 4, 2015

### Mantas777

I had the discussion with the man who gives me this task. I could explain now everything better.
I marked the places on the picture, where I have to calculate the stress (red colour). I have to choose myself different length (L) till I will get the maximal stresses. I have to check, what the maximal lenght (L) could be till I don't exceed allowable stress. (Also I will get to know what is the deflection, because 1.2m it's just preliminary value, after the calculations I will get exact value). But I can't find the formulas which I could use in this situation.

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7. Mar 4, 2015

### PhanthomJay

Sorry, but i still don't understand what you are trying to do. Are you trying to replace an old 200 m length of pipe with a new one? How is it supported along its length? How will the new one be supported? It is not clear to me what the task is.