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Struggling to solve this problem without FEA

  1. Jul 30, 2015 #1
    I have been given a structure to verify but I personally don't see a way of calculating the reactions & capacity of the parts without delving into a FEA analysis. I welcome any suggestions & help that you can give or insight, i am only trying to confirm the capacity & efficient sections & sizing is not absolutely critical.

    The project involves a double pipe clamp, i am not concerned by the deformation of the pipe as it is large bore & suitably think no prevent any deflections. the proposed weight is estimated at a tonne per pipe. The construction method is a combination of bolting & welding. (Not shown in the pictures) Each pipe clamp is bolted to the top & bottom of the pipe & again additional plate is bolted to the centre connecting piece along the top & bottom pipe clamp flange. The section around the clamp is a tee-section, selected for stiffness with a bolted end joint at the connecting positions of the top & bottom pipe clamp sections. (These are horizontal along the x axis)

    Tee-section prying will occur at the joint as 2 no. bolts will be situated either side of the t-section flange.

    What might not be apparent from the images is that the pipe below is offset approximately 200mm along the y axis, from the top pipe.

    The connecting plates along the top of the model (shows 3 offset plates, at varied angles) have changed from 3 to 2 plates at 60 degree angles from the horizontal (for simplicity). These are again bolted to the flange of the t-section & eye plates above.

    The design is purely static & no dynamic loads are present & the tee-section construction method involves cutting plate to circumference & welding to the equivalent rolled plate in contact with the pipe. I have assumed that the pipe load occurs at the CoM.

    diameter of pipe = 600mm (Fixed)
    thickness all around = 10mm can be altered
    All other dimensions can be altered to suit if required.

    What i'm struggling to calculate at this stage is the reaction at the pipe clamp joint (crudely drawing Red line) & then the reactions at the connecting members (Crudely drawing red circles) but all recommendations are appreciated. This is the first time i've used a forum for a engineering question so please be kind, ha. Thanks in advance.

    upload_2015-7-30_10-43-59.png
     

    Attached Files:

  2. jcsd
  3. Jul 30, 2015 #2

    Nidum

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    The best that you can do is to use simple statics . If calculated stresses and deflections come out as very safe values then that's ok . If not then you need a more complete analysis .

    Loads on upper horizontal joint : Weight of two pipes and the moment of weight of one pipe times its offset .

    Similar idea for other locations .

    Those struts look very weak compared to rest of structure .
     
  4. Aug 2, 2015 #3
    Is this a one /few off bracket, or are you looking at producing 1000's of them (say as a supplier)?
    Is the pipe offset along the x axis actually?
    You say that the system is static. Can we assume then that the pipes cannot swing clockwise due to the two pinned supports? If free, the two pipes will try to go into a vertical line.
     
  5. Aug 2, 2015 #4
    Thinking about this a little more, do we have to proceed on the assumption that standard pipe hanger methods can't be used, e.g. some threaded rods and RSJs?
     
  6. Aug 3, 2015 #5
    Nidum - I'm currently going down the simple static method, with the 2nd pipe's offset as the lever arm. Struts are double plates since the minor changes & not shown.

    Paul Uszak - This is a one off piece thats why im hesitant to go into too much detail with the FEA analysis. The reason I'm keen to try it in Abaqus is really to practice more than anything but only if i can justify it at a later stage. This pipe is offset & cannot rotate around to line up with the pipe above. I'm not 100% on how i can find out the compression & tension loads on the plate struts as there are only 2 x plates now in place unlike the image posted. Due to the location & build it will have to be plate & the tee-section was proposed for buckling effects.

    Thanks for the imput guys & i'm glad that i
    hadn't missed something obvious that was an easy answer.
     
  7. Aug 3, 2015 #6

    Nidum

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    Not entirely clear which struts are remaining .

    There are a few ways of dealing with loads/stress/deflection/design .

    (1) Assume the struts are very stiff in bending , then statics again , then use forces and moments to design struts that are very stiff in bending .

    (2) Use plastic hinge method as for portal frame type structures .

    (3) Change design as far as possible so that struts are not separate strips . A single piece of plate replacing the two separate struts would be much stronger and stiffer anyway . Need not be solid - could have large cut aways to go around things . Could actually be more than one piece of plate but the parts bolted firmly together .

    (4) If (3) not practical then try for some approximation to same - for instance using big triangulated reinforcers at connection to clamps .

    (5) Relocation of the strut to clamp connections is probably worth exploring .
    nb: With the single plate or triangulated foot designs struts don't have to be radial .
     
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