OVERVIEW

Safety and serviceability constitute the two primary requirements in structural design. For a structure to be safe, it must have adequate strength and ductility when resisting occasional extreme loads. To ensure that a structure will perform satisfactorily at working loads, functional or serviceability requirements also must be met. An accurate prediction of the behavior of a structure subjected to these loads is indispensable in designing new structures and evaluating existing ones.

The behavior of a structure is defined by the displacements and forces produced within the structure as a result of external influences. In general, structural theory consists of the essential concepts and methods for determining these effects. The process of determining them is known as structural analysis. If the assumptions inherent in the applied structural theory are in close agreement with actual conditions, such an analysis can often produce results that are in reasonable agreement with performance in service.

3.1 FUNDAMENTALS OF STRUCTURAL THEORY

Structural theory is based primarily on the following set of laws and properties. These principles often provide sufficient relations for analysis of structures.

Laws of mechanics These consist of the rules for static equilibrium and dynamic behavior.

Properties of materials The material used in a structure has a significant influence on its behavior. Strength and stiffness are two important material properties. These properties are obtained from experimental tests and may be used in the analysis either directly or...