Digital Design and Fabrication of Surface Structures

Abstract

This paper presents a study in digital design and manufacturing of shells, which are material-efficient systems that generate their load-bearing capacity through curvature. Their complex shapes are chal­lenging to build, and the few current shell projects employ the same shape repetitively in order to reduce the cost of concrete formwork. Can digital design and manufacturing technology make these systems suitable for the needs of the 21st century? The research developed new digitally-driven fabrication processes for Wood-Foam Sandwich Shells and Ferrocement-Concrete Sandwich Shells. These are partially pre-fabricated in order to allow for the application of Computer-Numerically Controlled (CNC) technology. Sandwich systems offer advantages for the digitally-enabled construction of shells, while at the same time improving their structural and thermal performance. The research defines design and manufacturing processes that reduce the need for repetition in order to save costs. Wood-Foam Sandwich shells are made by laminating wood-strips over a CNC-milled foam mold that eventually becomes the structural sandwich core. For Ferrocement-Concrete sandwich shells, a two-stage process is presented: pre-fabricated ferrocement panels become the permanent formwork for a cast-in-place concrete shell. The design and engineering process is facilitated through the use of parametric solid modeling envi­ronments. Modeling macros and integrated Finite-Element Analysis tools streamline the design process. Accuracy in fabrication is maintained by using CNC techniques for the majority of the shaping processes. The digital design and manufacturing parameters for each process are verified through design and fabrication studies that include prototypes, mockups and physical scale models.