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Structural design by analysis

Structural design by analysis

Structural design by analysis

In pressure vessel codes stresses are classified as primary, secondary and peak where, for example, the limit for secondary stress range is twice yield. Can these same classifications and limits be applied to other structures that are not pressure vessels, as such, and are there examples of such in design standards?


RE: Structural design by analysis

Hi Corus,
Yes, for a very quick answer. Have a look at how conical transitions for offshore structures are designed for example (see API RP2A).

Come back if you wanted a fuller reply.


RE: Structural design by analysis

Thanks JWB, yes was good enough but the example provided is even better.
Without having a copy of the offshore structures design code handy, does this include the assessment of thermal loads on a structure which are classed as secondary? These stresses don't seem to be considered in any structural standards I've seen. The reason for asking is that someone will point out that the particular structure I'm working on isn't a pressure vessel and that that design code isn't applicable.


RE: Structural design by analysis

Hi again Corus. Well yes, API RP2A does include thermal stresses 'in principle' in that if they were significant on a particular structure you'd have to take them into account in accordance with the code. But generally they're not that important. The obvious exception is a flare tower or boom which might well have significant temperature stresses, and would very likely include conical transitions.

The other area 'peak stresses' are taken into account is in design of welds for fatigue. I can't remember a good reference offhand but if I do remember it I'll let you know. (I have an idea it's in the old Dept of Energy guidance notes on fatigue. I think there is an OTC paper by Peter Marshall on the subject as well.)

Just in passing,the UK pressure vessel code (BS 59??? I can't remember the number), for example, is very frequently used by structural engineers for guidance on structural components not adequately covered elsewhere in structural codes (eg the formulae/charts relating attachments to vessels, local stresses etc). It's not at all unusual for this code to be referenced in structural design specifications, even though it is for pressure vessels. I occasionally come across the sort of individual who raises silly objections, so you have my sympathies on you last point!.

RE: Structural design by analysis

Thanks again JWB. It's BS 5500 I was in fact referring to although ASME VIII or III (I forget) uses the same principles. I'll use their procedures and refer objectors to your post on being silly. Perfect!


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