Applies To
Product(s):	AutoPIPE
Version(s):	ALL;
Area:	Report
Date Logged & Current Version	Oct 2025 25.00.00.299

Problem:

In AutoPIPE's Support Forces Report, why doesn't the local axis displacement match the global displacement?

For example, in Gravity (1), the global support deformation differs from the local deformation. However, the global and local forces are consistent.

Solution:

To help clarify the concept of global and local support deformation as presented in the support report, we created five distinct scenarios using a cantilever pipe model. In each scenario, one end of the pipe is anchored while the other end features a guide support. We applied imposed displacements and concentrated forces at the guide with varying configurations to demonstrate how these inputs influence the reported deformation values.

Scenario -1

Guide Condition	Gap at Guide	Imposed Displacement	Displacement Direction	Global Deformation in Z axis	Local Deformation	Local Deformation direction
Guided	0 inch	1 inch	+Z-axis	1	0	Left

Explanation

Global Support Deformation:
The global support deformation in the Z direction is 1 inch, which corresponds to the imposed displacement applied at the guide support. Since the support has a zero-inch gap, it moves 1 inch in the +Z direction, carrying the pipe along with it.

Local Support Deformation: In contrast, the local support deformation is 0 inch. This is because, from the pipe's perspective, there is no relative movement between the pipe and the support—their reference lines remain aligned, indicating that the support and pipe move together as a rigid system.

Scenario -2

Guide Condition	Gap at Guide	Imposed Displacement	Displacement Direction	Global Deformation in Z axis	Local Deformation	Local Deformation direction
Guided	2 inch	1 inch	Z-axis	0	1	Left

Explanation:

Global Support Deformation:
Global support deformation in Z direction is 0 inch because the support movement is 1inch the guide gap is 2inch , the pipe does not touches the support plates. Hence , we can see no pipe movement and no forces /moment generated.

Local Support Deformation:
In local deformation we can see 1 inch because the there is a relative movement of support of 1inch from the reference line.
Direction Interpretation:

Direction Interpretation:
To understand why the direction is considered left, imagine sitting on the pipe and looking downstream. You'll notice that the pipe has shifted 1 inch to the left of the reference line

Scenario -3

Guide Condition	Gap at Guide	Imposed Displacement	Displacement Direction	Global Deformation in Z axis	Local Deformation	Local Deformation direction
Guided	2 inch	3 inch	Z-axis	1	2	Left

Explanation:

Global Support Deformation:

The global deformation in the Z direction is 1 inch. This occurs because the support initially moves 2 inches to close the guide gap, and then carries the pipe along with it for an additional 1 inch in the positive Z direction.

Local Support Deformation:

In local support deformation we can see in screenshot below that pipe has moved 2 inch and touched the guide plates due to imposed support displacement of 3 inches so, if we take the relative movement of the pipe with respect to initial location of pipe it will be 2 inch.

Direction Interpretation:
To understand why the direction is considered left, imagine sitting on the pipe and looking downstream. You'll notice that the pipe has shifted 2 inch to the left of the reference line

Scenario -4

Guide Condition	Gap at Guide	Concentrated force	Displacement Direction	Global Deformation in Z axis	Local Deformation	Local Deformation direction
Guided	1 inch	100000 lbf	+Z-axis	1	1	Right

Explanation:

Global Support Deformation:
The global support deformation in the Z direction is 1 inch. This is because the pipe has shifted 1 inch along the +Z axis due to the applied concentrated forces on the pipe.

Local Support Deformation:
As shown in the screenshot below, the pipe has experienced a 1-inch displacement caused by concentrated forces. When we consider the relative movement of the pipe from its original position, the total displacement is 1 inch.

Direction Interpretation:
To understand why the movement appears to be towards the right, imagine sitting on the pipe and looking downstream. From this perspective, the pipe has moved 1 inch to the right of the reference line, indicating a positive Z-direction displacement.

Scenario -5

Guide Condition	Gap at Guide	Concentrated force	Displacement Direction	Imposed Displacement	Displacement Direction	Global Deformation in Z axis	Local Deformation	Local Deformation direction
Guided	2 inch	10000 lbf	+Z-axis	1	+Z	0.681	0.319	Left

Explanation:

Global Support Deformation:

The global support deformation in the Z-direction is measured at 0.681 inches, which corresponds to the pipe's movement in the +Z axis due to the applied forces.

Local Support Deformation:
In the local support deformation, as shown in the screenshot below, the pipe has also shifted 0.681 inches due to concentrated forces. However, when considering the relative movement of the pipe from its initial position, the displacement is 0.319 inches.

Direction Interpretation:
To understand why the direction appears to be towards the left, imagine sitting on the pipe and looking downstream along the direction of flow. From that perspective, the pipe has shifted 0.319 inches to the left of the reference line.

16. Displacement mismatch in global vs local coordinates (Support report)

Problem:

Solution:

See Also