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Quickstart Tutorial: The Buried L-Bend

Welcome to the Pipe Stress FEA Engine. In this 10-minute guide, we will model a simple L-bend pipeline transitioning from above-ground to underground, assign a geotechnical soil profile, and evaluate the thermal expansion stresses.

Step 1: Project Settings​

Before we draw any pipe, we need to establish the environmental conditions for our pipeline.

  1. Open the Design Palette (Sidebar) and navigate to the Settings (⚙️) tab.
  2. Set the Design Code to ASME B31.3.
  3. Set the Unit System to Metric.
  4. Under the Temperatures section:
    • Set Install (Amb) to 21°C
    • Set Design Max to 85°C
    • Set Design Min to -10°C
The Thermal Load Case

By setting a temperature differential, the solver will automatically generate an EXP (Expansion) load case to calculate thermal fatigue stresses.

Step 2: Defining the Soil Profile​

We are going to bury half of this pipeline. Let's tell the engine what kind of dirt we are digging through.

  1. Navigate to the Soil tab.
  2. Under Soil Profiles, enter the name Medium Sand.
  3. Set the Soil Type to SAND.
  4. Set the Depth to Centerline to 1.5 m.
  5. Click + Add Soil Profile.

Step 3: Drawing the Pipeline​

Now we will plot our nodes in 3D space. Navigate to the Nodes tab.

Node 10 (The Anchor)

  1. Leave coordinates at [0, 0, 0].
  2. Set Component Type to Straight Pipe / Free Node.
  3. Set Boundary Restraint to Full Anchor (Fixed).
  4. Click + Save Node.

Node 20 (The Bend)

  1. Set coordinates to [10, 0, 0]. (This pipe runs 10 meters along the X-axis).
  2. Set Component Type to Elbow / Bend.
  3. Leave Boundary Restraint as No Restraint.
  4. Click + Save Node.

Node 30 (The Underground Terminus)

  1. Set coordinates to [10, 0, -5]. (The pipe drops 5 meters down the Y-axis).
  2. Set Component Type to Straight Pipe / Free Node.
  3. Set Boundary Restraint to Full Anchor (Fixed).
  4. Click + Save Node.

Step 4: Assigning Properties & Soil​

We have our geometry, but the engine needs to know which pipes are buried.

  1. Navigate to the Assign tab.
  2. You will see two elements listed: e1 (Node 10 ➝ 20) and e2 (Node 20 ➝ 30).
  3. Under Section e2, check the box labeled Buried Pipe (Soil Restrained).
  4. Ensure the dropdown below it selects the Medium Sand profile you created earlier.
Automated Soil Springs

When you run the analysis, the engine will automatically discretize Element e2 and attach non-linear, multi-directional soil springs (Axial, Transverse, Upward, and Downward Bearing) along its length based on ASCE/ALA guidelines.

Step 5: Running the Analysis​

Look at the Analysis Controls panel floating over the 3D viewer.

  1. Ensure the Load Case is set to Operating (All Loads Combined).
  2. Click the blue Run Analysis button.
  3. The solver will calculate the stiffness matrix, apply the thermal expansion forces against the soil friction, and return the Maximum Deflection.

Step 6: Reviewing the Results​

At the bottom of your screen, click ▲ Expand Table to open the Results pane.

  • Pipe Stresses: Check the Max Code Ratio column. If any value exceeds 100%, the text will turn red, indicating the pipe has failed ASME B31.3 compliance.
  • Displacements: Switch to this tab to see exactly how much Node 20 pushed into the soil as it expanded.
  • Reactions: Switch to this tab to view the extreme forces generated at your Anchors (Node 10 and 30) due to the restricted thermal growth.

Congratulations! You have successfully modeled a soil-structure interaction.