Sufficient Strength
Strength refers to the ability of a steel member to resist failure (such as fracture or permanent deformation). It is the capacity to function safely and reliably without undergoing yielding or fracture failure under load. Strength is a fundamental requirement for all load-bearing members and is, therefore, a key focus of study.
Sufficient Stiffness
Stiffness refers to the ability of a steel member to resist deformation. If a steel member undergoes excessive deformation under load, it cannot function properly, even if it has not yet failed structurally. Consequently, steel members must possess sufficient stiffness to prevent stiffness-related failure. Stiffness requirements vary depending on the type of member; relevant standards and specifications should be consulted during application.
Stability
Stability refers to the ability of a steel member to maintain its original equilibrium configuration (or state) under the action of external forces. A loss of stability-referred to simply as "instability"-occurs when a steel member suddenly shifts from its original equilibrium configuration as the compressive load increases to a certain level. The buckling (instability) of compression members typically occurs suddenly and is highly destructive; therefore, compression members must possess sufficient stability.
