Pneu and Shell: Constructing Free-Form Concrete Shells with a Pneumatic Formwork

This paper presents a computationally driven form-finding methodology for the creation of surface-active structural systems. The case study outlines a feasible construction technique that uses fabric formwork and textile reinforcement as an innovative integrated solution for the fabrication of free-form concrete shells. Extensive developments in mineral and polymer materials such as ultra-high performance concrete (UHPC) and carbon fiber reinforcement may facilitate larger spans of composite shells in future. The research focuses on the aesthetic and structural potentials of the transforming from tension based inflatable structures into compression based thin shells. Pneumatic formwork allows for large span structures by a minimal material use and is less laborious due to prefabrication and on site casting, hereby offering critical advantages to conventional casting procedures. The presented physical prototype demonstrates that the shape of an inflated formwork can be manipulated in order to improve the aesthetical and structural behavior of the casted shell. With the use of a network of restraining ropes a ribbed shell can be built in order to utilize the shell for freeform geometry and prevent buckling. This method of a pneumatic restraint cast (PneuReCa) is effective for fabricating complex geometries at low cost while taking advantage of a digitally-driven, topologically-optimized design process.