Need to find the length and deflection of bending element (pipe) 1

[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 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 size 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.

 

[LittleInch]

Ask your tutor or look in your text book. This is a student question.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Mantas777]

I get this task in my work and I forgot how to do that, because I got these works only on my studies before some years ago.

 

[LittleInch]

Maybe, but textbooks still exist. Your description though makes no sense at all.

200m of 12" pipe??, Installing from the bottom??, Steel ST37?? Design code??

I appreciate English might not be your first language, which is where a proper sketch, drawing or photo can make the difference between understanding your issue and not. The diagram you post is not good enough.

Most of this will be covered in your design code. How to work out the bending stress and other static stresses you can find easily via toolbox or even wiki.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[rb1957]

is your sketch showing a cantilever or a guided cantilever ? it looks like there's some rotation restraint on the RH end ?

some better sketch of what you mean by "we install it from bottom", and "And from bottom we connect new pipe with old".

your running load, q, includes weight (440N/m ?) ?

another day in paradise, or is paradise one day closer ?

 

[Mantas777]

Sorry for my English, I try to do my best. I add the better picture of my task. I need to find the length of bending (L). The deflection could 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.

 

[rb1957]

a little better sketch ...

is the purple line (the new pipe) deliberately bent ? or is this showing the deflection from load ?

are you cutting out the old pipe and replacing with the new ? or are both pipes still working ? (does the new pipe replace or add onto the old pipe?)

part of the answer is going to be where are the existing pipe supports ? is the 200m is only the new piece of pipe ?

another day in paradise, or is paradise one day closer ?

 

[rb1957]

what does the 1.2m mean ? is this the amount of off-set you need, to clear an obstruction ?

if the pipe is supported at the ends, ie spanning 200m, then the deflection and the stress is easy to calculate ...
the moment for a uniformly distributed load is easy (wL/8)
the stress in the pipe is easy (MR/I)
the deflection is slightly tricky (from Roark, 5/384*wL^4/(EI)
assuming a simply supported span.

another day in paradise, or is paradise one day closer ?

 

[msquared48]

Rb1957...

M = wl^2/8



Mike McCann, PE, SE (WA)

 

[Mantas777]

The purple line it's just the principal scheme how we connect the new and old pipes together. But perhaps we can also to say, that it's showing the deflection from load. Because the real deflection should also look similar.
The new pipe replace the old pipe. The old pipe lenght is very large, because it's long pipeline. And we replace only 200m distance.
The 1,2m is the distance between old and new pipe. In other words it mean, that the new pipe it's about 1,2m lower than old pipe on the all 200m distance.
And the main question is the length (L) of the deflection at the both side of pipe. (At connection place of both pipe). It's have to be enough to calculate one side, because the both size is similar.
I have to choose the Length and to keep stresses allowable. The stresses of bending pipe have not to reach allowable stresses.
The distance between the both pipes (1,2m) could change a little bit. Because, when we taking smaller length it could be smaller deflection (than 1,2m) and when we take bigger length, it could be bigger deflection (than 1,2m).
So I have to find the right Length and to keep allowable stresses.
(The man, who give me this task, said, that it calls "parameter study", when we take different length and check the stresses).

 

[desertfox]

Hi

From your description and post I'm not sure what your trying to do but I suggest you have a discussion with the man who gave you the job in the first place and get some guidance from him.

 

[Mantas777]

I had a discussion. 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.