Abstract
Diagonal grids are one of the commonly used structural forms. Roof and floor system bridge ship decks, elevated highway and raft foundations are examples of structures for which diagonal grids may provide suitable solutions. Diagonal grids belong to a family of flat grids and their structural behaviour, like that of all flat grids, is mainly governed by bending. The members of a diagonal grid, therefore, essentially work in bending and their flexural rigidity is the main load resisting agent. Another two types of rigidities affecting the behaviour of flat grids are toroional and shearing rigidities. The nature of the effects of those rigidities, however, have not, in the past, been clearly understood and their importance has boon usually underestimated. This thesis presents an attempt to study the effects of these rigidities on the magnitudes and distribution of internal forces and displacements in diagonal grids. The material of the thesis is arranged in the following manner: The preliminary definitions and relations and the background to the subject are given in chapter one. Chapter two contains a description of the work involved in the analysis and the results of the analysis of a large number of diagonal grids. The conclusions obtained from these analytical, results are given in chapter five. An account of the experimental investigations is given in chapter four. In chapter three, the concept of vector and matrix norms is employed to develop an original technique which is used to estimate the changes in the internal forces and displacements of flat grids due to variations in the torsional or shearing rigidities. Furthermore. it is shown that the scope of this technique is not confined to the matter under consideration and the idea may be applied to many other problems of structural analysis. In particular, subject to the conditions described in the text, the technique will provide a new and powerful means for structural optimization processes and it may even find uses in disciplines other than structural analysis.