The transversal force is the force which works perpendicular to the centre line of the truss.
The important situations for the transversal forces are as follows:
1. A heavy load on a short span.
2. A heavy load near to the suspension point.
3. Truss constructions underneath a stage floor.
The transversal force acts as a normal force in the bracing and as shear force in the main tubes of a truss. The normal force in the bracing can be either compression or tension force. The shear force on the main tube tries to "cut" the main tube.
The allowable transversal force can be increased by increasing the diameter of the bracing or by increasing the wall thickness of the main tube.