Self Weight
The Self Weight feature automatically calculates the weight of structural members based on their material density and cross-sectional area. This ensures you don't have to manually calculate and apply gravity loads for the structure itself.
How it Works
Self weight is calculated using the formula:
Where:
- Area: Cross-sectional area from the assigned Section.
- Density: Material density from the assigned Material.
- Gravity Multiplier: A factor defining the direction and magnitude of gravity (typically -1 in Y).
Enabling Self Weight
Self weight is managed via the Self-Weight Settings dialog, accessible from the Ribbon.
- Click the Self-Weight button (weight icon) in the Ribbon.
- In the dialog, you will see a list of your Load Cases.
- For each Load Case where you want self-weight effectively applied, enter the Gravity Multipliers (g's).
Gravity Multipliers
You can define the acceleration due to gravity as a vector (X, Y, Z) for each load case. This allows you to apply gravity in any direction or scale it.
- Standard Gravity (Vertical Down): Set Y = -1, X = 0, Z = 0.
- Horizontal Acceleration (Seismic approximation): Set X or Z to a non-zero value (e.g., 0.1).
- No Self Weight: Set all values to 0 or leave the row empty/disabled.
Usually, you only apply self-weight to a specific "Dead Load" or "Self Weight" load case, not to Live Loads or Wind Loads.
Requirements
For self weight to be calculated correctly, every member must have:
- A valid Section Property (defines Area)
- A valid Material Property (defines Density)
If a member is missing either of these, its self weight will be zero.
Visual Validation
When self weight is enabled for the active load case, you won't see explicit arrows on every member (to avoid clutter), but the analysis will include these forces. To verify:
- Run the analysis with only self weight enabled.
- Check the Reaction Y forces. They should equal the total weight of your structure.