Definitions:

Axial Movement:

The dimensional shortening and lengthening of an expansion joint along its longitudinal axis.

Lateral Deflection:

The relative displacement of the tow ends of an expansion joint perpendicular to its longitudinal axis. This has been referred to as lateral offset, lateral movement, parallel misalignment, direct shear, or transverse movement.

Angular Rotation:

The displacement of the longitudinal axis of the expansion joint from its initial straight line position into a circular arc, Angular rotation occasionally referred to as rotational movement. This is not torsional rotation.

Torsional Rotation:

The twisting of one end of the Expansion joint with respect to the other end about its longitudinal axis, this twisting generally produces extremely high shear stresses in the bellows. For this reason it is extremely important that special hardware be used to limit the amount of torsional shear stress in the bellows.