| Applies To | |||
| Product: | AutoPIPE | ||
| First Affected Version: | 9.1.0 | ||
| Found in Version: | 10.00.00 | ||
| Fixed and Released in Version: | 11.01 | ||
| Area: | All | ||
| Severity: | Critical | ||
| Backlog Issue Number: | 354776 |
Problem Description
The moment sign for signed load combinations (Gravity, Thermal, Pressure) reported under “Tee local axis moments” report and used in stress calculations may be incorrect for ASME tees. When performing tee header moment summation between such a signed load combination and an unsigned load combination (Zero moment case, Earthquake, Wind, User, Time history, Response spectrum, Harmonic, Force spectrum, and SAM), the reported stress value may be lower than the correct stress value, which can be unconservative. This defect impacts all editions of ASME NB piping code.
Steps to Repeat
To illustrate this defect, the following scenario can be considered:
Step 1: Create a new ASME NB Nuclear 2010 edition model with English units
Step 2: Define a new pipe identifier with the following data:
Pipe Identifier: PIP12
Nominal Diameter: 12.000
Schedule: STD
Pipe Material: SA106-B
Step 3: On the Operating Pressure & Temperature, leave the pressure value at 0.0 psi and temperature value at 70.0 deg F
Step 4: On the Design Pres & Temp dialog, leave the Design pressure at 0.0 psi and Design temperature at 70.0 deg F
Step 5: Starting with node A00, insert a tee point at A01 and enter the following data on the Tee point dialog:
Add point [B]efore/[A]fter: After
Name of point: A01
Offset from which point (O=Origin): A00
DX = 5.0 ft., DY = 0.0 ft., DZ = 0.0 ft.
Tee component: Tee
From point orientation: 1-Header
Use same segment name along header: Checked
Type of tee: Welding
Step 6: Continue the header from point A01 to A02 another 5 ft. in the Global +X direction using pipe identifier PIP12
Step 7: Insert a branch run from tee point A01, running 5 feet in Global +Y direction towards B01 using pipe identifier PIP12
Step 8: Insert an anchor at the tee point A01
Step 9: Insert a concentrated moment of 10000 ft-lb about each global axis at nodes A00 and B01 under T1 load case
Step 10: Create a new static earthquake load, leaving default accelerations (1.0, 0.5, 1.0) g
Step 11: Analyze the model with GR, T1 and E1 enabled
Step 12: Invoke Result Model Options dialog (Result > Result Options > Model) and change “Force (Global/Local)” option to “L”
Step 13: Create a new Service Level A stress summary
Step 13a: Set equation index 2 (Equation 10) combinations to Zero Moment and Thermal 1{1}
Step 13b: Set equation index 3 (Equation 10) combinations to Zero Moment and Static Seismic 1{1}
Step 14: Take out “Forces & Moments”, “Stress Summary”, and “Tee Local Moments” report
Note that the Tee Local Axis Moments have the incorrect signs for Thermal 1{1} in the Z direction. Further, the stress summary results for the following equations are unconservative due to this sign error: eq. 10, eq. 11, eq. 14 and Leakage.
Evaluation Criteria
The following considerations are provided to assist in your evaluation of the potential impact of this defect on the results:
1. Evaluate whether this defect has affected any existing models by considering the criteria below:
a. Was the model created or updated in program version 9.1.0 or later?
b. Was the piping code for the model ASME NB Nuclear 1972 + 1972 W addenda edition or later?
c. Was there any tee placed in the model?
d. Was there a stress summary in the model containing a signed load case and an unsigned load case in separate equation indices?
A 'No' to one or more of the above criteria means that this defect does not affect the model’s results. No further consideration for this model is necessary.
Workaround
Change the tee component so that the header segment direction for both the headers is directed away from the tee point
Solution
Program shall report and use the correct moment sign for tee local axis moment report and stress calculations.
Additionally, to assist in the screening of the models created in previous program versions for any potential impact by this defect, the program shall automatically examine the model database after opening the model and generate a report (model name + "_D354776.TXT"), listing the tee points which are potentially impacted by this defect:
“Stress value when combining a signed combination with an unsigned combination at tee points may be incorrect due to a previous program defect #354776. Would you like to review the evaluation report?”
The contents of the critical error report shall be like the following sample critical error report:
Defect #354776 Evaluation Report
---------------------------------
Model Name: 354776-CriticalErrorReport_V10
Model Version: 11.00.00.22
Program Version: 11.01.00.09
Report Filename: 354776-CriticalErrorReport_V10_D354776.TXT
---------------------------------
The moment sign for signed load combinations reported under “Tee local axis moments” report and used in stress calculations may be incorrect for ASME NB tees. Additionally, when performing tee header moment summation between a signed load combination and an unsigned or reversing dynamic load combination, the reported stress value may be lower than the correct stress value, which can be unconservative. Please refer to the published defect report for more details, mitigation conditions and instructions. To assist in the screening of this model for any potential impact by this defect, the program has examined the model database and has found that the stress values for the tee points mentioned should be re-computed using this program version.
After saving this model or running any analysis in this version or later commercial release versions, this screening will no longer be performed.
Tee(s) potentially impacted by this defect:
-------------------------------------------
A01
Stress Summaries potentially impacted by this defect:
-----------------------------------------------------
Stress Summary #1