On the design of masonry shell structures

Abstract

This thesis investigates the design of masonry shell structures. Design is understood to involve two main processes ; the first one is the specification of shape, form, and thickness and the second is the justification of such choices through the analysis of its behaviour. The thesis is therefore introduced by an extensive literature review of. first of all. the relevant material properties, such as strength, stiffness, anisotropy, and bi-axial stress states. as well as of some interesting construction techniques, based on minimal or no form work the premise being that the contemporary adoption, or otherwise, of masonry shells as a feasible structural solution depends on the "economics" of the construction process. The analysis of the strength of masonry arches and shells is reviewed extensively, with considerable emphasis given to the validity of the application of limit analysis to masonry shells. in view of the presence of finite friction. Techniques for the form-finding of shells and for the optimisation of such forms, are then finite element technique developed for studied. and a the finding of membrane thrust surfaces for shells incapable of carrying tension (as properties) . The technique is based on the solution of having possibly orthotropic the partial differential equation relating shape, stress and loading, given a specific loading regime, and specific boundary conditions. The stress distribution, satisfying the given boundary and material conditions, is obtained, not on the basis of a trial-and-error approach, as is often the case, but on a plane stress analysis of the horizontal projection of the shell. The resultant shape hence automatically satisfies the boundary conditions. Various examples of the results of such method are given.