A structure's ability to resist compressive stress without compromising its load-carrying capacity. When a structure is subjected to a sufficiently high compressive force (or stress), it has a tendency to lose its stiffness, experience a noticeable change in geometry, and become unstable. Examples of structural instability include the buckling of a column under a compressive axial force, the lateral torsional buckling of a beam under a transverse load, the sideways buckling of an unbraced frame under a set of concentric column forces, and the buckling of a plate under a set of in-plane forces.