Sources of moment in columns:
Bending moment in column arises due to different reasons:
- Unequal loading on both sides of column.
- Unequal span on both sides of columns.
- Rigid frame action.
- Eccentricity of loads.
- Out-of-plumbness of column.
- Out-of-straightness of column.
1. Unequal loading on both sides of column
If the load is not equal than the total load will produce eccentricity with respect to center of gravity of column and hence moment will be generated.
2. Unequal span on both sides of columns
Due to different lengths of spans on both sides of column net moment will be created.
3. Rigid frame action
Due to monolithic behavior of column it behaves like a rigid joint and end moment of beam is transferred to the vertical strut.
4. Eccentricity of loads
When the load is applied at midpoint of column by means of brackets, moment is generated.
5. Out-of plumbness of column
If the strut is not vertical then at the top produces some moment below it.
6. Out-of-straightness of column
If the strut is not exactly straight then moment will be generated.