stress due to external loads of truck accelerative force

[ZHWIL28]

I am conducting the stress calc for vessels on highway truck. Is there someone know how to deal with the external loads by accelerative force applied at the support of vessel. Can I apply the WRC 297 or 107 on this case?
Thanks a lot!

 

[ZHWIL28]

Why there is nobody reply to this spread? Should I explain more detailedly? Give me an idea, please.

 

[arto]

Maybe look in the CFR's?
There's a lot of info on Railroad tank car design in the DOT sections

http://www.access.gpo.gov/nara/cfr/waisidx_02/49cfr179_02.html

Maybe there's something similar for trucks somewhere?

 

[ZHWIL28]

Thanks for arto's direction. The problem is that I know the code requirement and each of external loadings applied at the support of vessel, but I do not know if I can apply the stress calculation methods in WRC 107 to analyse this case?

 

[hockchong]

WRC107 only apply on cylinder or sphere. You can use it to check the load from your support acting to the shell but not on the support itself (for example saddle). Transportation load has to be considered in the support calculation as additional load acting on horizontal and vertical direction. Make sure the saddle can withstand the load. Further more, the acceleration also add more external stress to the shell (L.P.Zick analysis). If your shell is not sufficient thick, maybe it required stiffener ring.

 

[ZHWIL28]

Thanks for hockchong's suggestion. Is there some zick's technical paper as you mentioned " the acceleration also add more external stress to the shell (L.P.Zick analysis)"?
Can you give more detail information about this methods?

 

[hockchong]

For my design, I considered the load per unit length increase due to vertical acceleration. For example, the vessel weight is 5000kg. For normal case, we only considered 5000 x g but for transportation, we times with the vertical acceleration. e.i
Fv = 1.4g (or maybe in m/s²) then the equation should be 5000kg x 1.4g. For better understanding, you have to refer to pressure vessel handbook regarding saddle design or any L.P Zick reference. Hope this will help.

 

[ZHWIL28]

                               ^ Q/2=33137 lbf weight reaction                       |                       
                               ^ Fv= 0.35*(Q/2)=11598 lbf
                     saddle---|||  vertical accelerative Force                         |||  
 Fa= 0.35*(Q/2)=11598  <-------|
  accelerative force          /
                             /
                            /
      Fv= 0.2*(Q/2)=6627   <
        lateral force

 

[ZHWIL28]

The draft I draw above is the each force applied at the pedestal of vessel. All material I have found now are the case only consider the static weight loading on the two saddle for horizontal vessel. I need to know the best stress calculation method for this special case. Thanks!

 

[hockchong]

For your case, what I will do is convert the acceleration to static load acting on three direction. It depend on client requirement whether to consider it separately or other wise. Do normal static calculation e.i. force acting vertical (acceleration + g), force acting horizontal and lateral.

 

[chicopee]

I can not imagine a truck having such high acceleration that additional g's in excess of .1 are needed. On the other hand, I would strongly consider g's from deccelartion resulting from accidents or from centrifugal forces when a truck is traveling at 70 mph and going around a curve w/o super elevation.

 

[ZHWIL28]

In the code of CSA620.98 and CFR 49 178, there are excat definition of each direction equivalent static forces due to dynamic loadings.
-horizontal accelerative force=0.35 times vertical reaction
-vertical accelerative force=0.35 times vertical reaction
-lateral accelerative force=0.2 times vertical reaction

I conducted the approximate stress calculation at the midspan of vessel and the area near the support, there are some high stress points. I am not sure if my calculation methods are valid. Is there some persons know the exact solution of shell stress calculation for this case? Please contact with me at wzhang@arneng.ab.ca ,Thanks!