SIF's For Oblique Reinforced Tees: B31.3

This has probably been raised on may occassions but I would appreciate some guidance on establishing SIF's for reinforced tees where the angle between the branch and header is less than 90 deg. If the most appropriate answer is that we have to do an FEA to establish the SIF's, are they established by ratio of maximum peak stress in the header and branch compared to the peak stress in a butt welded joint in each? Whilst this approach is defendable it remains a subjective assessment since the magnitude of peak stresses depend on issues such as final weld profile and the geometry tolerances to which any reinforcing pad is made.

There seems to be no guidance available in ASME III Div 1 NB-3680 and ASME VIII Div 2 App 4 Article 4-6 does not cover laterals with external reinforcement (pads).

Any feedback/recommendations would be appreciated. Merry Christmas to all readers!

Dear Mr. Baldwin,

we have been working on a project two years ago where the following guidlines for the SIF's of lateral branch connection have been used:

1. In-Plane SIF

For every degree deviating from 90° the SIF(i) had to be increased by 0,5%.

2. Out-Plan SIF

Branch connections d/D <= 0,7 with re-pad had to be treated as unreinforced tees.

For those branch conections without re-pads, with a d/D ratio > 0,7 or operating
at the creep temperatures special analysis or FEA had to be performed.

Hope this helps a bit,

Veit Bockemühl
esn GmbH
Hamburg, Germany

P.S.: Best Wishes for Christmas and the New Year for all readers. vb@esn-gmbh.com

Using the <em>link</em> above, perform a search of this discussion forum for SIF. There are a number of discussion threads on this topic.

The short answer is that there is nothing officially published by the codes (except for the French code, CODETI) on anything other than 90 deg tees. Your best bet is FE analysis, unless you find something else in the literature (such as PVP or ASME), as mentioned in the above posts.