Normale spanning

Consider a rod subjected to an axial force; as a result, a resistive force is developed across the cross-sectional area, which is termed as stress. The SI unit of stress is Newton per square meter.

Now, consider a bridge truss member subjected to an axial force. It develops internal forces and stress normal to the cross-sectional plane, called the normal stress.

The resultant normal stress represents an average stress over the cross-section, rather than at a specific point.

According to the conditions for equilibrium, the internal forces equals the applied force, implying that stress distribution is uniform, except near the point of application.

However, this uniform distribution is only possible if the line of action of the loads passes through the centroid of the section, termed centric loading.

When axial loading is applied eccentrically, the distribution of forces and stresses cannot be uniform or symmetric due to the additional moment created.

So, the actual stress distribution in an axially loaded member is statically indeterminate and depends on the specific mode of load application.