Chapter 16 - Analysis of Statically Indeterminate Structures

Abstract

This chapter examines methods of analysis of different forms of statically indeterminate structures. In the analysis of statically indeterminate structures two basic methods are employed. In the first method—flexibility or force method—the structure is reduced to a statically determinate state by employing releases. The alternative procedure, known as the stiffness or displacement method, is analogous to the flexibility method, the major difference being that the unknowns are the displacements at specific points in the structure. Generally the procedure requires a structure to be divided into a number of elements for each of which load-displacement relationships are known. Equations of equilibrium are then written in terms of the displacements at the element junctions and are solved for the required displacements. Both the flexibility and stiffness methods, for practical structures having a high degree of statical indeterminacy, generally result in a large number of simultaneous equations that are most readily solved by computer-based techniques. However, the flexibility method requires the structure to be reduced to a statically determinate state by inserting releases, a procedure requiring some judgment on the part of the analyst. But, the stiffness method requires no such judgment to be made and is therefore particularly suitable for automatic computation.