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This paper describes the construction of a thin shell concrete roof with a novel cable-net and fabric formwork system [1, 2]. The construction of the shell was a proof-of-concept demonstration of the formwork system, showing that through appropriate cable-net component design and an on-site shape control system [3], concrete shells with complex doubly-curved geometry can be built efficiently and with minimal material waste. The formwork system works by installing a fabric shuttering on a cablenet structure, that is tensioned from stiff boundary beams supported by standard scaffolding props. Starting from the lower supports, the concrete was sprayed on the flexible formwork from two aerial platforms in a carefully planned sequence. The cable-net was designed to deflect into the designed shape of the shell structure under the self-weight of the wet concrete. The cable-net nodes were specifically designed to accommodate the required geometric degrees of freedom; to restrain the fabric shuttering and to fix the carbon-fibre reinforcement at the correct level in the concrete section. They

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Focusing on the issues of sound propagation in a free field condition and on the concept of uniform sound energy in an outdoor performance environment, our research aimed to develop a computer-aided process for the generation of reflective acoustic surfaces to be used as concert-shells, a computational design tool for acoustic form-finding. The project is ultimately aimed to investigate the acoustic potential of complex and doublycurved surfaces through the analysis of the Total Relative Sound Level / Strength parameter (G), with reference to the proposed values set by M.Barron, based upon the source-receiver distance and the subsequent subjective judgments on loudness. A simplified and fast ray-tracing acoustic simulation algorithm was developed in combination with parametrically controlled shape variations of the reflective surfaces. Sound energy uniformity evaluation function considering the direct and reflected sound components was written in order to define and evaluate the rate of distribution uniformity of sonic energy over an audience. This evaluation function was used in a genetic algorithm that enabled us to explore a wide set of surface morphologies which allowed us to isolate the fittest one to our specific uniformity requirements. At the end of the genetic search, an acoustic simulation plug-in called Pachyderm was employed with both NURBS and mesh-based acoustic simulations in order to validate the genetically selected surfaces with specific reference to G values. A further step of resultant data visualization and human selection was necessary to compare the output data and to evaluate the final surfaces from an architectural perspective. 32 Sound-Strength Driven Parametric Design of an Acoustic Shell in a Free Field Environment