Reciprocal-Framed Grid Shell

Reusable, Adaptable and Rapidly-Assembled Structures

This project proposes a parametric workflow for the design of reusable, adaptable, reciprocal-framed grid shell, which can be used to cover large spaces, such as archaeological sites, temporary accommodation or services etc. This workflow has been applied for the case study of the Ancient Ships Archaeological Site free-form shelter in Pisa (88x48 meters).

With a thesis entitled: An innovative sail-shaped shelter for the Ancient Ships Archaeological Site of Pisa", Elena Corio has been awarded best thesis award from the Eurographics Italian Chapter as 2017 best Computer Graphics Master Thesis


Main Idea

Reciprocal structures, or nexorade, are composed by the assembling of groups (three or more) straight beams mutually connected by mono-lateral T joints. This kind of structures can be easily built in relatively unprepared sites, dismantled, transported and re-used even by not specialized hand-craft. The main load-bearing elements are derived from a polygonal-based mesh with large faces for achieving visual and structural lightness, and triangulated frames for structural indeterminacy and stability.

We developed a parametric workflow for both the form finding and the digital fabrication processes, which includes site requirements and fabrication constraints. Moreover, we introduced a novel, modular, accommodative, steel T-joint for timber reciprocal beams to be used for each connection to account for different elements lengths and various mutual angles between the components.

Reciprocal-Framed Grid Shell Design

The structure must protect excavations and archaeologists from the weather and provide an easy access to visitors at the Ancient Ships Archaeological Site of Pisa. Additionally, it must allow for an easy dismantling and moving to another site. A timber double-curved nexorade grid shell fits the design purposes, and optimizes structural efficiency, fabrication requirements and aesthetic qualities. Timber allows for modular design and prefabrication, it is renewable and capable of satisfying the architectural demand. With simple instructions, parts can be produced in different shapes and lengths using widely available fabrication tools, and assembled efficiently.

Indeed, contrary to traditional grid shells, the connection between nexors can be achieved simply and quickly, with no need for any sophisticated equipment. This feature, combined with the manageable size of structural elements and relatively low use of scaffolding, makes this structure very suitable to satisfy the different requirements of a quick and temporary shelter of a large archeological area. The form finding process was oriented towards a funicular surface (simply compressed under its self-weight) through a particle-spring algorithm. The shell presents openings along all the edges to allow visual continuity from the outside to the inside, along with necessary aeration.


The workflow includes a component for the digital fabrication and labelling of the pices to be used for large scale prototypes. For the purpose of testing the feasibility of our design approach laser-cut MDF prototypes have been fabricated.

Work Group

Elena Corio

Francesco Laccone

Nico Pietroni

Paolo Cignoni

Maurizio Froli (University of Pisa)