Equilibrium Analysis

There are occasional opportunities for the design of masonry—of a new vault, for example, or of a highway bridge. However, the structural analysis of masonry is concerned in the main with the determination of the state of an existing structure. Analysis is of great theoretical interest, but it is also of practical importance. In repair work it may be necessary to replace a major structural element, and it is clear that estimates must be made of the structural forces. Indeed, the main objective of a structural analysis is the determination of such forces. It is only rarely that deformations of a masonry structure need to be computed; deformations arise, almost without exception, from displacements imposed by movements of the environment (sinking of foundations, spread of abutments), and such deformations, notably cracking, do not depend on the elastic properties of the masonry. An elastic analysis will, in fact, shed no light on the deformation of a masonry structure. Equally, the magnitudes and distribution of the internal structural forces are determined by the (in general, unknown) movements imposed by the environment, and again an elastic analysis will be of no help in estimating these forces. It is fortunate that an “equilibrium” analysis, making no reference to elastic properties of the masonry, can nevertheless be made to give reliable values for the key structural quantities.