No abstract

This paper investigates both experimentally and theoretically the free rocking of a prismatic block supported by a stationary , horizontal foundation: the block is tilted, almost to the point of overturning, and released from this position. It is shown that the standard mathematical model for this problem is often inaccurate. A critical review of the implicit assumptions behind the standard model reveals that the free-rocking response of short blocks depends crucially on bouncing after each impact; out-of-plane effects are significant in very short blocks. The response of slender blocks is found to be easier to predict. Rocking has been observed during earthquakes in structures that consist of fairly rigid, unbonded elements, e.g. stacks of graphite blocks in nuclear reactors. and ancient Greek columns, and also in slender structures with foundations unable to resist uplift.

This study was inspired by a model of a triangulated cylindrical shell made by C. R. Calladine during an investigation of the mechanics of biological structures. The model consisted of identical triangular panels on a helical strip and had a small-displacement internal inextensional mechanism. It is shown that many triangulated cylinders broadly similar to Calladine’s model can be folded down to a compact stack of plates: only small strains, whose magnitude can be made arbitrarily small by the choice of suitable design parameters, are imposed during folding. A general geometric formulation of the problem is presented and then, assuming that the folding process is uniform, the folding properties of any triangulated cylinder of this generic type are discussed.

This paper presents a new concept for retractable roof structures. The new structures consist of a foldable lattice of beams connected by cylindrical joints, to which covering panels or membranes are attached. These structures fold towards their perimeter and there is practically no limit to their shape. Solutions to the key problems that have to be solved in the course of the kinematic design of this new type of structure are presented, including two different ways of connecting them to fixed foundation points while maintaining their internal degree of mobility, and how to determine the shapes of the covering panels to avoid interference during retraction.

This paper presents a new deployable reflector concept for an Earth observation mission that requires a low-cost L-band Synthetic Aperture Radar (SAR) instrument using an offset parabolic cylinder with a linear feed array. The required reflector shape is an offset parabolic cylinder with arc-length of 7.9 m and width of 3.2 m. A novel "hollow solid" structural concept is proposed that comprises curved surfaces formed from thin sheets of carbon-fiber-reinforced-plastic (CFRP) connected by flexible hinges along the edges. The front surface of the hollow solid has the required shape for the reflector. This proposed structure has very high stiffness-to-mass-ratio, because of its thin-walled boxtype construction. A detailed study of a half-scale technology demonstrator, including design, manufacture and testing is presented in the paper. A preliminary design of the full-scale structure, which has an estimated mass of 33 kg, is also presented.