Loads

Loads are forces or actions that cause stress, deformation, or displacement in an object or system. In physics, a load can be a weight, gravitational force, or other external influence. In engineering, the term describes external demands placed on structures, machines, or components, which must be analyzed to ensure safety, serviceability, and reliability.

Common categories include dead loads (permanent self-weight of the structure and fixed equipment), live loads (occupants, furniture, vehicles), environmental loads (wind, snow or rain, temperature), and dynamic or impact loads (machinery start-up, seismic events, moving loads). Fatigue and repeated cyclic loads are treated separately when assessing long-term performance.

Loads are quantified as vectors with magnitude, direction, and duration. In design, engineers use load cases and combinations—often multiplying basic loads by factors prescribed by codes—to reflect uncertainties in material properties, construction, and loading conditions. Units are typically newtons (N) in SI for forces, or kilonewtons (kN) as common practice, with occasional references to pounds-force (lbf) in other regions.

Outside structural engineering, the term also appears in electrical and electronics contexts. An electrical load is a device or circuit that consumes power, characterized by its current, voltage, and impedance. Understanding loads in both mechanical and electrical domains is important for performance and safety.