Applies To
Product(s):	AutoPIPE
Version(s):	ALL;
Environment:	N/A
Area:	Report
Original Author:	Bentley Technical Support Group
Date Logged & Current Version	July. 2017 11.00.00.22

Problem:

What does LOC mean in the General Stress Report?

Solution:

Total stress is calculated every 15 deg and the zero degree axis for the total stress location angle in a clockwise direction around the pipe. The 0 degree axis is the local axis of the pipe cross-section, i.e. perpendicular to the pipe axis, corresponding to the resultant in-plane bending moment.

For example, if the local bending moments are my and mz, then arctan (my/mz) is the location off the 0 degree reference axis for the general stress location relative to the local y axis.

Note: For straight pipe in-plane bending is arbitrary since no plane of bending like an elbow.

Axial stress: fx/A

in-plane bending stress: my/Z

out-plane bending stress: mz/Z

where,

fx = local axial force

my = local in-plane bending moment

mz = local out-plane bending moment

Question: 1. How does AutoPIPE 2025 define 0-degree axis?

Answer: Total stress is calculated every 15 deg and the zero-degree axis for the total stress location angle in a clockwise direction around the pipe. The 0-degree axis is the local axis of the pipe cross-section, i.e. perpendicular to the pipe axis, corresponding to the resultant in-plane bending moment.

Note: For straight pipe in-plane bending is arbitrary since no plane of bending like an elbow.

Question: 2. How is the LOC angle measured in AutoPIPE 2025?

Answer: To interpret the LOC (Location) value in AutoPIPE’s General Stress Report:

- AutoPIPE calculates stresses every 15° around the pipe circumference and identifies where the maximum total stress occurs.
- The LOC value is the angle (in degrees) measured clockwise from AutoPIPE’s 0° axis to the point on the pipe wall with the highest stress.
- The 0° axis is defined by AutoPIPE as the direction of the resultant in‑plane bending moment, based on the local bending moments My and Mz.
- So, if the report shows LOC = 45°, it means the max stress occurs 45° clockwise from that bending‑moment reference direction.

This helps you understand exactly where around the pipe’s circumference the critical stress is located.

Question: 3. For tee points, AutoPIPE v25 measures the LOC's angle datum from the branch axis, while AutoPIPE v12 uses the local Y-axis as the reference.
Is this update related to correctly accounting for ii (in-plane SIF) and io (out-of-plane SIF) in the transformed moments (My, Mz) before calculating the angle via arctan(My/Mz)?

Answer: This is an Enhancement:1235552 implemented in version 2023.1, the software changed how it defines the local coordinate system for tee junctions in piping.

A tee has three legs, and the software now creates a special coordinate system based on how that tee is actually positioned in space. Here’s how it works:

1. Torsional axis (Twist direction)
  This axis is along the direction of the pipe leg.
2. In‑plane axis (Flat direction)
  This is in direction normal to the plane the junction resides on.
3. Out‑of‑plane axis (Up direction)
  This axis is created by crossing the first two axes.

LOC's angular datum is aligned to the positive out-of-plane axis. Since the tee local coordinate system is strictly dependent on the orientation and geometry of the tee, the LOC is expected to change. See the image below for a visualization.

So, the differences you're seeing are expected — the coordinate system is now smarter and reacts to how the tee is actually arranged.

15. What does LOC mean in the General Stress Report for AutoPIPE?

Problem:

Solution:

See Also