Sign Conventions for Forces and Moments

Convention for axis orientation

Right hand rule

Ingeania uses a right hand rule for axis orientation. The X, Y and Z axes are coloured using an RGB scheme as this is the most commonly recognized triplex of colors. The X axis is coloured red, the Y axis is coloured green, and the Z axis is coloured blue. This helps provide a convenient mnemonic.

Sign conventions for axial forces, shear forces and bending moments

Ingeania uses the following conventions for forces:

Axial forces: A tensile axial force is positive, while a compressive axial force is negative.

Shear forces: A clockwise shear force is positive, while an anti-clockwise shear force is negative.

Bending moments: A moment that induces compression at the top of a member (i.e. sagging in a beam) is positive. A moment that induces tension at the top of a member (i.e. hogging in a beam) is negative.

Structural engineering force moment sign conventions