Drakkko wrote:
I am modeling some Weak Acid Pipelines, and I have to imposed movement at support, due to movement of the structure wich this Pipes are supported.
As I understand - further answers and suggestions elaborated on the CEASAR-II techniques.
However, it is not matter of proper technique or proper software tool/feature employed; the problem is more profound and cannot be solved solely within Piping-Stress Model - no matter what software is utilized. The flexibility of the supporting structure could be assessed only if this structure is properly modeled - not as a singular post or frame but as a realistic milty-level pipe-rack module or platform. For most projects we deal not with singular posts but with multi-frame structures and hence the flexibility of the simplified structures modeled by Mechanical Engineer in CEASAR or AutoPipe environment is so far from reality that the resulting support displacements are totally irrelevant.
- No Mechanical Engineer would spend time and effort to repeat in his CEASAR-II or AutoPipe Model the relatively complex structure which Structural Engineer has already modeled and analyzed by his respective software (STAAD, RISA, S-Frame or SAP2000).
- It is unrealistic to expect Intergraph or Bentley (at least in foreseeable future)come up with a program for modeling Piping-Stress Systems and Supporting Structures in the same environment and analyze them joint as one system (see my post at the thread775-400131)
The only realistic solution - mutual cooperation with the Structural Engineer and exchange of information between two Disciplines; the more critical the Piping System is - the more iterations of this exchange is expected. With each iteration the Support Reaction Force and the Support Response (presented either as the Displacement Value or as the rigidity of linear spring in the direction of the Force) should converge and become more and more realistic.
The Graphic Navigator I briefly described (as the Second Solution) in thread775-400131 would be instrumental for this cooperation and help greatly to the Mechanical Engineer; especially when the supporting structure is 6 or 8-storey high and exhibits noticeable displacements acceptable by Structural Limits but absolutely unacceptable for the Piping System being supported.
Unlike full-fledged analytical program such Navigator (let's name it StrUNa for Stress/Structural Universal Navigator) would be relatively easy to develop: the 3Dgraphics are limited to work-lines and nodal circles without complex shapes, reading text input and output files from respective Stress and Structural Models is pretty straightforward, associating Piping Support Nodes and underlying beam of the supporting structure also could be done (assuming that all models are built with CAD accuracy)
Probably, the major predicament (aside of modelling accuracy and proper use of Plant Coordinate System) is the serious misunderstanding between the two Engineering Disciplines i.e. how Structural should interpret the Reaction Forces resulting from certain Load-Combinations of Stress Analyses and how to correlate them to the 'Piping' Load Cases (Dead, Operation, Friction, Anchor and alike) stipulated by the Industry Structural Guidelines. A few structural engineers tried to clarify this issue in this Forum without any significant success. Let's hope one day we could compare our Guidelines and come up with a reasonable way(s) to formalize this transition..
Cheers
Len
