Hello Stressers!!!

For occasional stress evaluation in ISO 14692 which one of the two load case is correct (assuming U1=seismic load)

1) Load Case 1:

W+T1+P1+U1

or

2) Load Case 2:

Same as ASME B31.3 set-up (Sustained + Occasional Load). I will not write down the details since every stress engineer already familiar with this.


I think it is Load Case 1. If this is the case, then for mix piping (FRP & Steel), the load case for occasional stress is different and must be set-up accordingly. One FRP vendor assume the occasional stress is same for both Code, and they use the load case 1 for both codes which is obviously not in accordance with ASME B31.3.

Please correct me if I'm assuming it wrong.

Thanks & Warm Regards

Unlike B31.3 which breaks stress evaluation into distinct load groups, ISO 14692 evaluates any given state of stress. So while your B31.3 components follow (EXP), (SUS), and (SUS)+(OCC), the FRP components would look at W+P1+T1+D1+U1 (and W+P1+T1+D1-U1 if nonlinear).

Thanks for that very convincing explanation Dave. You're definitely right, since steel can have stress relaxation or stress relieving (except at creep temperatures where they maybe unrelieved stress due to elastic follow-up). This type of behavior is not experienced by FRP/GRE pipes.

Just correct if I made any misleading statement.

Warm Regards,

what about iso 14692-3 (2002) par. 7.6.2.3?

<considered in combination with sustained loads EXCLUDING THERMAL EFFECTS.>>

"excluding thermal effects"... so it should be

W+P1+D1+U1 (without the "T1").

I found related articles, you can find there needed load cases:
https://www.whatispiping.com/grp-gre-frp-piping-system
https://www.whatispiping.com/stress-analysis-of-grp-gre-frp-piping-stress-analysis
https://www.whatispiping.com/stress-analysis-of-grp-gre-frp-piping-system-using-caesar-ii

I must agree with vermaccio.
Stress assesment for occasional loads in ISO 14692-3 (2002) is similar to ASME B31.3 i.e. SUS+OCC (W+P+U for example).

To consider non-linear effects maybe need to follow the usual set-up for ASME B31.3 Occasional assessment.


L1 = W + T1 + P1 (OPE)
L2 = W + T1 + P1 + U1 (OPE)
L3 = W + P1 (SUS)
L4 = L2 - L1 (OCC) (ALGEBRAIC)
L5 = L3 + L4 (OCC) (SCALAR)

Does anyone have a copy of ISO 14692 2017? What's the current statement in the latest code regarding this occasional loads?

Thanks,