Question
Why is the Sagging Moment Shown as Negative in FEA NX?
Answer
The sign depends on the local axis orientation at the cutting section of the beam.
To better understand sign notation in LDFS, let’s go step by step with a simple example:
Beam Details
- Beam Type: Simply Supported Beam
- Cross-section: Rectangular (0.5m × 0.5m)
- Span Length: 5 meters
- Loading: Self-weight (SW) considering material density of 25 kN/m³
Through manual calculation, we can obtain the values :
Ra = Rb = +15.625 kN
Mmax = +19.53125 kNm
FEA NX – LDFS Text output
For End A (Near to Left support)
The FBD of the block for face with normal along +X.
Shear Force (FZ): Acts along the -Z direction
Bending Moment (MY): Acts anti-clockwise, which FEA NX represents as acting in the -Y direction
Text Output by FEA NX with appropriate sign.
Attachments