3.1 Equilibrium of Structures
3.2 External and Internal Forces
3.3 Types of Supports for Plane Structures
3.4 Static Determinacy, Indeterminacy, and Instability
3.5 Computation of Reactions
3.5.1 Computation of Reactions Problems and Solutions
3.6 Principle of Superposition
3.7 Reactions of Simply Supported Structures Using Proportions
The objective of this chapter is to review the basic concept of equilibrium of structures under the action of forces and to develop the analysis of reactions exerted by supports on plane (two-dimensional) structures subjected to coplanar force systems.
We first review the concept of equilibrium and develop the equations of equilibrium of structures. Next we discuss the external and internal forces. We then describe the common types of supports used to restrict movements of plane structures. Structures can be classified as externally statically determinate, indeterminate, or unstable. We discuss how this classification can be made for plane structures. We then develop a procedure for determining reactions at supports for plane statically determinate structures. Finally, we define the principle of superposition and show how to use proportions in the computation of reactions of simply supported structures.