LRFD - ELASTIC–PLASTIC ANALYSIS FOR BOLTED JOINT

[Soave]

Dear All

I'm here again with other question about Elastic-Plastic Analysis.

How should I apply LRFD concepts to bolt pretension for an analysis of bolted joint? Since I will apply the required factored loads to internal pressure...
I think I will apply the same factored loads (for internal pressure) to bolts preloads.


Thank you all again.

Best Regards

 

[TGS4]

Interestingly enough, this is one area that there doesn't seem to be much research on, nor is there much guidance from the Code (the BFJ rules are mostly a mess there).

This is a difficult concept, because in many flanged joints, the initial bolt load will be a large fraction of yield, and most bolt material have high yield-to-ultimate ratios, so applying a load factor on the initial pre-stress may put it well over ultimate.

Not an easy concept.

I would like to open a more generic discussion on the topic, though.

 

[Soave]

Another concept applied to BFJ is Service Criteria.
I suppose If I apply factor on pre-tension I will satisfy the Global and Local Criteria (In cases that bolts do not go over ultimate).
But I think that the service criteria may not have a satisfactory (consistent) results, like flange rotation, gasket initial and operation stress.

Please, let me know your thoughts

 

[TGS4]

Perhaps the relevant question is: are plastic collapse and local failure more relevant/important, or are service criteria?

 

[NRP99]

Link

Analysis in this paper has been done using the elastic properties of bolt and applying bolt pre-load as it is(not explicitly mentioned)for elastic-plastic analysis.
Anyway the bolts are standard components and it is generally used as weak link although it is high strength bolts because bolts can be replaced easily than flange. The limiting factor will always be the flange strength which is always of less strength than bolts. Service criteria is also more important as more amount of flange rotation means there are chances of leakage and gasket crushing will result in replacement of gaskets.

Editlease refer this thread also-thread292-205291