EN 13480 : sustained Allowable stress

Hi everyone,

i saw in EN 13480 (ed 2012) that the allowable stress for sustained loads is defined as "ff" (and not fh ?!)

sustained :
sigma 1 < ff (formula 12.3.2-1)
with ff = min {Rp0.2t/1.5 ; Rm/2.4} (formula 5.2.1-1)

it's the same for occasionnal loads ("sigma2 < k.ff"), and even for liberal stress (sigma4 < "fa+ff")

does Caesar take this into account ??? what version ?

it seems to me that it doesn't, does anybody knows why ?

thx by advance for your help,
Alcor.

I'm going to answer your question "yes" (in all versions that support EN-13480). Note that the C2 Material Database has one table column of allowable stresses verses temperature. That table essentially contains "fh". However, since "fc" is defined at room temperature, and the "f" and "fcr" are at the metal temperature, "fc" should not govern (as the minimum value).

Hi Richard,

thank you for your quick answer.
I'm ok to say that fh is the minimum value, and seems to be the value taken by CII as primary allowable stress.

More precisely, my question is that the code doesn't design "fh" as sustained allowable stress, unless i'm missing something in the code ?

taking "ff" leads in some cases to higher allowable stress that fh, for example : with P235GH at T = 50°C
Rm = 360 MPa
Rp0.2t = 235 MPa

by section 5.2 :
ff = min {f; fcr} = f = Min {Rp0.2t/1.5 ; Rm/2.4} = 150 Mpa

by section 12.1.3.2
fc = fh = min{ f ; Rm/3 } = Min {Rp0.2t/1.5 ; Rm/2.4 ; Rm/3} = 120 Mpa

if you follow the code formulas :
- sustained allowable stress : ff = 150 Mpa
- displacement stress range : fa = 1.25fc + 0.25fh = 120*1.5 = 180 Mpa
- with libéral stress : fa + ff = 330 Mpa

does CII comply with that ?

c2 has one column of allowable stresses versus temperature. All allowable values come from that table. Depending on the material and temperature, a specific value could be governed by yield, tensile, or creep.

Hi again,

I did a quick test Under CII 7.00 : if I define EN 13480 as code and select P235GH material, the primary stress allowable in CII is 120MPa and not 150MPa.

that value leads me to think that CII considers fh as primary allowable, instead of ff demanded by the code.

not compliant ?

Alcor,

As per EN-13480 part-12, Fc will be minimum of (Rm/3; F)

and Fh will be min of (Fc; F; Fcr)

So the case you had explained above the value of 120Mpa will be same for Fc and Fh. It's not Caesar-II but it suggested by code and Caesar-II follows the code.

Regards,
R.K.

for what temperature You calculate this ??

I think I can confirm Alcor thesys: CaesarII is not in compliance with EN13480: CaesarII use Fc (or Fh, is the same in the game of minimum values) instead of Ff for allowable stress in the sustained load cases (out of creep zone Ff = F).

I think that CaesarII can not handle two different sets of "basic" stress required by EN13480: one based on Rm/2.4 for the evaluation of F, the other based on Rm/3 for the evaluation of Fc/Fh. When Rm/3 "dominates" the calculation, Fc is lower than F therefore Fh is lower than F.

In these cases, EN13480 requires F but CaesarII uses Fh (I can say ... conservatively but not correctly).

Not simple to solve for Intergraph...