What kind of checks needs to be peformed on shell cross section

[CivilTanju]

hi all,

As the subject explicitly mean, if I know the stresses or forces acting on shell (s11, s22, s12, F11,f22, f12, m11, m12, m22, v13, v23 ) element (full shell behaviour) what type of checks do I need to perform to prove that shell element is full capable to carry bending, axial and shear forces and buckling as well.

The shell element in question is intended to be used in spherical storage tank.

Any help in advance will be appreciated.

Best Regards,

 

[CivilTanju]

Any idea ?

 

[rb1957]

if the pressure vessel only has +ve pressure, then the skins are unlikely to buckle.

i guess you structures guys have some sort of "code" to comply with ... safety factors, etc. i'd've started with peak stress (membrane + bending).

what about fatigue effects ? again the code may answer this question with a large safety factor.

how much do you know about designing pressure vessels ? i have my suspicions and, if true, would suggest meaningfull discussions with someone who knows more, not just posting here !

 

[CivilTanju]

Actullay I'm trying to design the wheat storage silo(approx. 6mt diam. 18mt tall). It doesn't have only the pressure, at least the analysis show that there are N,S,M in each face of shell. Actually there aren't codes in our country when it comes to the steel bin,silo design and analysis, so I thought I have to rely one way or the other to the foreign codes. But so far I couldn't find any eleborated and sufficient info about the design sequence.

API 650 code: states how to design and construct oil tanks with ASD check, in the ASCE -05/art 15.7.9 specifies the ground supported tanks for granular materials as well. I'm trying to obtain the eurocode 8 part 4 which is not still in hand. But what I'm looking to is the shell, bottom part, nozzle, hopper, oppening etc. bearing and welding bearing capacity.

>what about fatigue effects ? again the code may answer >this question with a large safety factor

If there is not any cycling loading, unless the earthquake loads, why do I have to wory about fatigue? But definitely the loading/unloading and modal combination effect will be taken into consideration, if that's what you trying to point out with fatigue. I'm even planning to apply time history analyse.

Your suspicion is right I have no experience previously about pressure vessels. When I googled around, the projects that I have seen so far which have been analysed and implemented succesfully. Just with dead, live and earthquake loads not took any vacum effect or friction at the shell face. It isn't beyond of my thinking.

 

[CivilTanju]

It may seem that I'm still dancing around the same issue. But Let's say that I have properly and adequately introduced all the requared loading(dead, live, e.quake, wind, modal combinations temperature etc..) conditions/combinations and take into account the previously design approach to eliminate flowing obstacles. For the analyse, I'm planning to use FEM and for the content mass the Jansen formula, apply the stress as area force to the side and bottom shell elements.

Can I solve the max. bearing stress of shell(bottom and side) by biaxial sigma = N/A + (Mx/W)*x/2 + (My/Wy)*y/2 equation and shear force to = T*Sx/(Ix*b)? Of course I'll keep in mind the API 650/Eurocode8/AISC shell design compulsory regulation and take the governing(higher) value for thickness.

 

[kelowna]

CivilTanju

I think do might have cycling loading even if you do not think so. Temperature effects can be very significative in shell desigh (them being so thin) and that is cyclic.

I agree with rb1957, you need to discuss this with somebody with experience on the field. Posting here will not cut it