Sign convention for ASBD section analysis for Moments
There are two sets of axes to consider when defining a section
The section is defined in the global y z axis plane as shown with the x axis out of the paper.
The red axis is Y and the green axis is Z
When applying moments to the section they are defined about local axes with an origin at the
centroid such that the X axis is perpendicular into the paper as shown. A positive y moment
produces compression at the top fibre and a positive z moment produces compression at the right
most fibre
Positive Z Moment
Positive Y Moment
If a positive My and a positive Mz are applied at the same time then the neutral axis will be as shown
below
The application of shear force is applied in the global geometric axis. So the application of positive
shears is shown below
Positive Z shear
Positive Y shear