Most people think of buildings as massive, inanimate objects, like giant rocks. In fact buildings are more aptly compared to living things, complex entities that move (the top floors of a skyscraper may sway many feet with the wind) and "breathe" (buildings exchange gases with the environment). Like living things, buildings are also part of, and intimately affected by, their natural environment. This includes the many physical forces-what engineers refer to as "loads"-that can be destructive either suddenly or over time.

Architects, engineers, and builders are aware of these varied forces and take them into consideration during every stage of a building's life. Loads play a role in how a building is designed, where it is located, what materials and methods are used in its construction, and how it is maintained and used. The concern with safely handling potential physical loads must be...