Posted by: prakash_26jan
Allowable stress as per ISO 14692 _CAESAR 5.2 - 08/01/10 09:33 AM
Hi
can some body help me how Caesar 5.2 will calculate the allowable stress as per ISO 14692.BECAUSE WHEN WE ARE CALCULATING THE allowable stress by hand using iso14692 part 3(technical corrugandum 1)is not matching with Caesar II 5.2 version calculated value.
Is there any specific file(supporting file) to be installed while installing the Caesar II 5.2 ?
prakash kumar
piping stress engineer
Composite pipes industry
muscat(oman)
Posted by: xlu
Re: Allowable stress as per ISO 14692 _CAESAR 5.2 - 08/02/10 10:30 AM
Kumar:
Could you send us (techsupport@coade.com) your case where the allowables for ISO-14692 from CAESAR II are not matching your hand calculation, please?
Thanks
Posted by: prakash_26jan
Re: Allowable stress as per ISO 14692 _CAESAR 5.2 - 12/21/10 03:56 AM
Dear Sir
We are GRP manufacturer. We are manufacturing the GRP pipes and fitting as well as we are doing full engineering of GRP pipes. When we are performing the stress analysis of any system we found some node allowable stress is not matching with as per ISO 14692. We have two query regarding this
1) The formula mentioned for calculating the allowable stress in ISO 14692 part 3 (Equation 19 to 22) is not matching with the formula mentioned in the Caesar quick guide .please clarify.
2) As per Caesar quick guide some where the allowable stress is matching and some where it is not matching.
As per example: I mention the two scenarios in 1st scenario it is matching where as 2nd scenario it is not matching in the same report.
Input for calculating the allowable stress and code stress
As per our test value
Failure envelope for plain pipe
σ al (0:1) = 25.69 M Pa, σ al (2:1) = 49.67 M Pa, σ al (1:1) = 49.67 M Pa
σ hl (2:1) = 99.34 M Pa, σ hl (1:1) = 49.67 M Pa
Failure envelope for joints and fitting
Qs = 99.340
Biaxial stress ratio (r) =1
A1, A2, A3= 1
Scenario 1:
As per the Caesar extended o/p report
Axial Stress = 27.92 MPa, Bending stress = 0.85 MPa,
Torsion Stress = 0.02 MPa, Hoop Stress = 56.40 MPa
As per the Caesar Quick guide
σ a, sum = ((σ ap+σ ab)^2+ 4ξ^2)^0.5
= 27.93 MPa.
= code stress
σ h, sum = ((σ h)^2+ 4ξ^2)^0.5
= 56.41 MPa.
Also as per Caesar Quick guide
σ h, sum <= f2 *A1 *A2 *A3 *σ hl (2:1)
σ h, sum=56.40<= 82.45
&
σ h, sum >= f2*A1*A2*A3* σ hl (1:1)
56.40>= 41.2261
So use
σ a, sum <= f2*A1*A2*A3* σ al(1:1) + (σ al(2:1)- σ al(1:1))*( σ h, sum – f2*A1*A2*A3* σ h(1:1)) / (σ hl (2:1) - σ hl (1:1) )
= 41.23 MPa
And same allowable stress has mentioned in the extended stress Report.
Where as Scenario 2:
As per the Caesar extended o/p report
Axial Stress = 13.58 MPa, Bending stress = 0.13 MPa,
Torsion Stress = 0.03 MPa, Hoop Stress = 56.40 MPa
As per the Caesar Quick guide
σ a, sum = ((σ ap+σ ab)^2+ 4ξ^2)^0.5
= 13.59 MPa.
= code stress
But as per Caesar extended o/p report
The code Stress = 56.40 MPa
σ a, sum <= f2*A1*A2*A3* σ al(1:1) + (σ al(2:1)- σ al(1:1))*( σ h, sum – f2*A1*A2*A3* σ h(1:1)) / (σ hl (2:1) - σ hl (1:1) )
= 41.23 MPa
= Allowable Stress
But as per Caesar extended o/p report
The Allowable Stress = 82.47 MPa
Please clarify.
Your positive and quick reply is highly appreciated.
Best Regards,
Prakash Kumar,
Piping Stress Engineer,
Posted by: corne
Re: Allowable stress as per ISO 14692 _CAESAR 5.2 - 12/21/10 02:10 PM
C2 checks both the axial and hoop stress against the applicable allowables.
The stresses with the highest stress ratio are displayed.
Scenario 1:
Axial / axial allowable = 27,93 / 41,23 = 67,7 %
Hoop / hoop allowable = 56,40 / 82,45 = 68,4 %
Scenario 2:
Axial / axial allowable = 13,59 / 41,23 = 33 %
Hoop / hoop allowable = 56,40 / 82,47 = 68,4 %
In scenario 2 C2 will display the hoop stress result and allowable and ratio.
In scenario 1, according to the info you gave C2 should give the hoop, but maybe these are rounded figures so C2 actually calculated a higher axial stress ratio in scenario 1.
The above (displaying the highest stress ratio) should be the issue I think.