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"Most pipe can deflect 1/2 inch in a 20ft span (even considering simple supports) without experiencing any overstress at all, whereas such a deflection in a structural member, even if not overstressed, would cause unsightly cracks in concrete beams" "in general piping is very flexible in...

nickelkid, thanks for your response, but I have to ask, what was the extent of the "input/support" from your structural folks? For each seismic and wind load case, did you obtain structural displacements for each of those load cases and then apply them to your piping stress model at each pipe...

I'm also a structural engineer. Here are a few important points - pipe stress analyses are almost always nonlinear, so "unfactored" piping loads are unacceptable for structural design since superposition in load combinations is not valid for nonlinear load cases. You must insist that the piping...

edwin, why not use less expensive non-spring support(s) instead of a spring hanger given that deflection is so small? Significant load redistribution can occur before a pipe fully lifts off a support, so the calculated .1 mm deflection is not necessarily a concern.. Your allowable loading seems...

Typical pipe stress load cases commonly used for ASME B31.1/B31.3 code stress calculations seem mathematically inconsistent for nonlinear analyses (+Y supports, gaps, friction), relying on linear algebraic subtractions when dealing with nonlinear (NL) load cases. Superposition doesn’t apply in...

Caesar II is capable of nonlinear static analysis if the nonlinearity is limited to boundary conditions. Gaps, friction, and bi-linear springs are all nonlinear boundary conditions which Caesar handles in static analysis. Caesar cannot consider material nonlinear behavior, geometric nonlinear...

You gave dangerous, incorrect advice to the person who started this thread as has already been explained in detail, whether you care to acknowledge your errors or not. When called out on your misguided advice and wrongheaded understanding of the subject matter, instead of admitting that you...

That has to qualify as one of the most bizarre comments I've ever read in an eng-tips forum.

"Since we started and open discussion, can you please explain here where and why you consider uplift supports with gap and friction if you are supposed to run a dynamic analysis?" You seem quite unwilling to read and comprehend. It DOESN'T MATTER whether the analysis is static or dynamic. If...

"If you read my answers I have never talked about friction or uplift supports with gaps, and the post was not asking for them either. Please do not pull the conversation/discussion into different subjects." Perhaps you missed the title of this post: Pipe lift off in dynamic analysis You...

"ZippyDDoodah, I guess you generalized the problem on all types supports and too far, however missed the concern was for uplift only" saplanti, by definition, the ability for the piping to "uplift" means that the support is nonlinear, and therefore a nonlinear analysis is required if the...

Model the pump as a rigid element using the pump weight just as DSB suggested. Support it with +Y supports with a friction factor for concrete (.6 or .7 ??). Model discharge and suction as DSB suggests, because discharge piping will add to the weight for increased friction resistance.

Actually, DSB's advice was not a "full description" of what to check, but a general word of advice as to what to watch for. If nonlinear supports in the piping system are defined with gaps and friction which is common, dynamic load distribution and reactions cannot be reliably determined with...

Rob, apologies for getting you sidetracked. I think you will get much more from Peng & Peng's book than from Kellogg. In fact, Peng references Kellogg methods often in their book. The B31.3 code has you consider weight and pressure stresses independently from thermal stresses. As you are...

Actually beam element programs, if designed with nonlinear analysis requirements in mind, should be able to handle nonlinear analysis just fine. Not just gaps, friction or multilinear springs either. There's no reason other than limitations with specific software programs as to why beam/line...

Crusader, you misunderstood my point. I never suggested yielding at nozzles. I suggested that yielding in other parts of the piping system could have a significant effect on equipment loads and in calculation of piping loads on supports and possibly dynamic reactions. I have examples where...

prex, thanks for your comments, but I think you may have missed a point. When you say that the B31.3 method has been proven to give safe results, you're referring to stress/fatigue, not piping loads on sensitive equipment right? I agree with your comment that the code stress calculation methods...

As John Breen elaborates in this thread, http://www.eng-tips.com/viewthread.cfm?qid=246231 , the ASME B31 codes calculate an "equivalent stress". If plastic deformation is important enough to be considered for stress, it's important to consider for piping equipment/flange/support loads as...

Since you are more familiar with B31.3, I will cite from that standard: If you continue reading in that section, the code elaborates as to WHY this yielding is acceptable.. because it relieves stresses. We're all trying to learn here, but I think my original question/observation asking why...

biginch, from my perch, your assertions regarding yield are directly contradicted by ASME code commitee member Ron Haupt: http://www.sstusa.com/99janmar.php Relevant quote: "Generally, the flexibility allowable stress-range was permitted to approach two times yield" I could swear that I've...