Abstract
The lamella structural systems consists of a number of interconnecting units forming a lozenge-shaped grid pattern. Each unit which is twice the length of the side of a diamond is called a "lamella". Theoretically lamella construction may have any geometric surface. The lamella roofs have been used frequently for structures where a wide clear span, freedom of movement, and attractive ceiling are required. Lamella roofs are ideal for prefabricated construction, as all the units are of standard size. Lamella structures can be constructed in steel, timber, aluminium, and reinforced concrete. The stress distribution in a lamella system is remarkably consistent, since the numerous lamella units mutually brace each other at the joints. In the theoretical analysis six degrees of freedom are assumed for each joint. The method which was selected for the theoretical analysis was the "Stiffness Method"; employing the "F.T. Compiler Technique" for the solution of a large number of simultaneous equations. Computer programs were written for the most general case of a space structure (pin or rigidly connected) in ALGOL 60. The lamella barrel vault, Fig.(1), is considered as a rigidly connected structure, and theoretical analysis of its stress distribution was carried out to investigate: 1. The influence of longitudinal supports: for this purpose two cases of longitudinal support were taken into accounts a) Boundary joints fixed in position, b) Boundary joints fixed in position and direction and for both cases (a & b) two systems of symmetrical and anti-symmetrical loading were considered; 2. The influence of gable-stiffening: for this investigation six types of gable-stiffening, which represent the different kinds of gable-boundaries were studied; 3. A short-cut solution. For a long barrel vault two approaches were considered, which gave similar results: (i) - Analysis of central arch along the lamellas? (ii) - Analysis of half diamonds between two transverse sections over the entire span. Finally, an approximate method was used. The results for each of the above cases are discussed individually. Experimental investigations were carried out on the lamella barrel vault model, Fig (1), employing the "direct method of testing". The theoretical and experimental results were compared and certain conclusions drawn. Finally, general conclusions and the possibilities for future research were expounded.