This paper describes a new erection technique for post-formed timber gridshells which takes advantage of inflatable membrane technology. Consolidated construction techniques for timber gridshells are based either on “pull-up” / “push-up” (i.e. Mannheim Multihalle) or “ease-down” behavior (i.e. Downland Open Air Museum). However, these techniques show shortcomings already at small scale. When applied to large scale, a lack of a standardised, cost-effective erection method implies that techniques have to be reinvented every time. When construction becomes expensive and laborious, gridshells become affordable only for exceptional projects, such as the Downland Museum or the Mannheim Multihalle. These are among the reasons why gridshells are not widely applied, even if they enable covering large spans with a minimum amount of material; they are built from basic technologies though self-construction; they are fast to construct; they are entirely recyclable. In this work, an inflatable membrane is designed and used to erect a gridshell prototype with a footprint of 55m2. Inspiration comes from the work by architect Dante Bini, who realised thousands of inflatable concrete domes worldwide.

The Italian architect Dante Bini began his studies on shell structures during the 1960s. He developed and refined a form-finding and construction technique to erect a finished large-span reinforced concrete (RC) shell structure through the use of an inflatable membrane. This system was patented in 1964 under the name ‘Binishell’ and, over the following decades, it has been applied to construct hundreds of domes throughout the world. Bini’s invention fitted perfectly into the Italian post-war tradition, as he was, at the same time, the architect and builder of his structures. A few experimental tests were initially performed in Italy, and the first binishells that he lifted after the patent was filed were also constructed there. Since 1966, as a result of Mario Salvadori’s interest, Bini has been recognised internationally. In 1974 he moved to Australia after the NSW Department of Public Works asked him to realise a set of school facilities using the binishell technology. The construction of concrete shells has always been a difficult and expensive process – the preparation of formworks, as well as the installation of curved reinforcing rods before the concrete is poured, require experience and increase the construction costs. Such problems are particularly relevant in the Australian context, where the use of simple and rapid construction technologies has always been a priority. Dante Bini’s life and the binishell technology have been well documented from the historical point of view. However, a detailed report and contextualisation of Dante Bini’s Australian experience is still missing. A first attempt to survey the Australian binishells has already been published by the authors.2 The focus was on placing Bini’s early work within the previous research on pneumatic structures which began in the 1920s. The narrative of this paper instead starts in the 1960s, a period of great media success for RC shells. First, the origin of binishells is described as a natural consequence of three preceding inventions/patents. A timeline of the events that defined Bini’s emigration to Australia is then provided. A full list of the Australian binishells is also included, with detailed information on the archival sources, major alterations and current conditions.

Timber gridshell structures, such as the Multihalle for the federal garden festival in Mannheim or the Downland Museum, have been the result of a creative–generative process that indissolubly ‘welded’ the structural contribution to that of form exploration. The challenging design and construction issues have been typically addressed and resolved in several inventive ways. However, still now, form-finding and erection of timber gridshells present many difficulties. In this regard, this paper aims to provide a series of novel steps to address some of the main design and construction issues that are associated with ‘actively-bent’ timber gridshell structures. First, the main characteristics of the construction process of timber gridshells are described and the basic theoretical concepts for its numerical simulation, through Dynamic Relaxation method, are introduced. Second, a practical method for sizing the laths' cross-section is presented. Third, a new erection technique for timber gridshells is proposed and applied to the construction of a full scale (prototype) structure, the Toledo gridshell 2.0. Fourth, a new bracing system for the same structure, which was built at the Faculty of Architecture, University of Naples Federico II in June–July 2014, is explained and discussed. The paper also highlights the need for further application to validate the techniques explained here, with particular attention being paid for the construction of large scale free-form structures.