In this paper, a computational morphogenesis process is applied to the design and the optimization of the shell roof of a large music hall. The architectural concept is based on the folded plate technique: a set of reinforced concrete plates, connected to each other on the edges, forms the global shape of the roof. The dimensions of each plate are different, so that the structure is not regular; moreover each plate is not plane but slightly curved to form hypars. Starting from the geometric concept of the roof, a process of optimization and form finding has been applied, in order to obtain the best acoustic performance, in terms of distribution of the acoustic pressure level in the hall. The folded plate surface has been described mathematically by using a NURBS representation and the control point positions has been assumed as the design variables. The acoustic performance has been evaluated by means of an algorithm able to calculate the acoustic pressure level in all the points of the hall, considering the reflection of the roof. The uniformity of acoustic pressure level in all the points of the hall has been assumed as the target of the optimization process. A genetic algorithm, i.e. an evolutionary iterative population-based scheme, has been adopted in the optimization procedure. The evolution of the shape towards the optimal solution is controlled interactively by the designer, in order to avoid the convergence to unexpected configurations.

In the paper the application of a GA evolutionary algorithm to the structural optimisation of free-form architectural shell structures, as large concrete roofs, is shown. The attention is focused on the need of different computational tools and on the problems involved in multidisciplinary design, as the communication and information exchange. The procedure herein described can be applied to more general problems, involving not only the structural performance, but even functional and constructive requirements. The proposed implementation of the algorithm is efficient, robust and particularly capable to avoid local minimum convergence.