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Determination of design stresses in EN 13480

Determination of design stresses in EN 13480

Determination of design stresses in EN 13480

(OP)
I'm currently developing pipe specs for 800H (1.4958) material designed to EN 13480. I'm having difficulties getting the design stresses right.

Acc. EN13480-3 Ch 5.1, the design stress is the lesser of the time-dependent and time-independent stress values. Determining the
- time-independent stress values is done using EN 13480-3 eq 5.2.2-1 and values from EN 10216-5 table 7 and 9. For example, at T = 550 C, I get a design stress f = 63.3 MPa. This is the result of Rp1.0 = 95 MPa divided by 1.5. This is the 'highest stress I could find', which is for 550 C.
- time-dependent stress values is done using EN 13480-3 eq 5.3.2-1 and values from EN 10216-5 Annex A, table A.1. For example, at T = 560 C, I get a design stress fcr = 138.7 MPa. This is the result of SRTt = 95 MPa divided by Sfcr = 1.5.

Im not sure where EN 13480 defines the onset of creep (i.e. time-dependent stress values). This topic is closely related to this topic

I'm obviously missing the point here somewhere, as design stress values just cant go up like that, esp in the creep regime.
Someone can point what I'm doing wrong?

RE: Determination of design stresses in EN 13480

Hi,
If I read your post correctly you say for the time dependant stress you have SRTt divided by 1.5 and get 138.7 ??? Do the math again!!!

RE: Determination of design stresses in EN 13480

(OP)
Haha, correct, big typo error there dazed. It should have read;

Quote:

For example, at T = 560 C, I get a design stress fcr = 138.7 MPa. This is the result of SRTt = 208 MPa divided by Sfcr = 1.5

PS: for my calculations I use the 10.000 hr creep rupture strength values from EN 10216-5, as we have a reduced plant design life.

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