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Whenever a static analysis load set includes Gaps/Friction/Soil it is calculated using a non-linear analysis. As a non-linear analysis, individual load cases (i.e. Gr, T1, P1, E1, W1, etc..) are applied one at a time in a sequence. This specific sequence does affect the calculated combination results (see AutoPIPE online help for more details).
For example, by default, occasional load cases like Earthquake or Wind are analyzed after Pressure cases, that are applied after Thermal loads, that are applied after the initial load case Gravity.
Wind hitting the operating position of the piping may calculate different support loads than earthquake or wind loads calculated just after GR (wind hitting the ambient position of piping).
When perfoming a nonlinear analysis, select Loads > Static Analysis Sets and check boxes in the "Non-Linear" columm or enable Gaps/Friction/Soil inside of an analysis set
.
To define all non-linear options, modify the analysis set, and check the option "Gaps/Friction/Soil", Click OK and the next screen appears, see online help for details on this dialog screen.
Note: Why does NonLinear Analysis provide the following options on the dialog above:
“Ignore friction GR”
"Ignore friction E”
For more complicated load sequence, uncheck the "Use Default Sequence" box to modify the Load sequence and press OK button as shown below:
1. Please see the following AutoPIPE help section:
Help > Contents> Search Tab> enter "Understanding Load Sequencing" (include the quotes), press List Topics button, double click on the selected topic from the list provided to see more information select the hyper link for "Understanding Load Sequencing".
2. Open the PDF file directly from the AutoPIPE folder, search for "Load_Sequencing.pdf" or "Non_Linear_Load_Sequencing.pdf" on your computer.
3. Additional documents found on the WIKI sites:
a. Non-linear_Guide_explained
b. Understanding Non-Linear Load Sequencing
c. Treatment of Support Friction in Pipe Stress Analysis
d. Nonlinear Effects in Piping System Analysis
e. Improved Iteration Strategy for Nonlinear Structures
f. Discussion of AutoPIPE Advanced Non-Linear Analysis Engine
g.Advanced Nonlinear Analysis - Linear vs. Non-Linear analysis in AutoPIPE
Note:
V-stop lift-off message is displayed by AutoPIPE when a pipe is resting on a V-stop in sustained/dead load condition i.e. gravity (which means that the support force displayed in the grid in the Global vertical axis would be negative, meaning that force is acting downward on the v-stop), but the pipe lifts-off from the support (Zero force acting on the support in global vertical axis, displacement of the point would be positive in global vertical axis) under operating loads i.e. Pressure or temperature.
The maximum possible frictional force that can be developed for a support depends on the bearing (vertical) force applied to that support point, forces applied in the orthogonal direction to bearing and the friction coefficient.
01. Non-Linear Analysis - Gap Support
02. Non-Linear Guide vs Inclined Supports Explained in AutoPIPE
03. Non-Linear Analysis - Wind Load
04. Non-Linear Analysis - Pipe / Support Friction Force
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