A primer on the form and behaviour of gridshell structures

First steps towards understanding gridshells

In this article, we’ll begin our exploration of gridshell structures. This will be the first of several such gridshell explorations we’ll make over the coming months here on EngineeringSkills.

In some respects, this article can be considered a review of the landscape, where we identify the main features to provide a suitable context for further study.

With a good map of the landscape, we can make better decisions about where to explore next. Before too long, we’ll be moving from a narrative discussion into coding and analysis!

What is a gridshell?

A gridshell is a 3-dimensional shell structure similar to a solid shell, wherein the structure is discretised into linear or approximately linear elements meeting at nodal points, Fig 1.

Gridshells share the same load-resisting mechanism as solid shells in that they derive their ability to resist transverse loads from their double curvature. In this way, the (grid)shell’s ability to and efficiency in resisting load is inextricably linked to its form or shape.

Therefore, gridshell design is a two-step process: first, a suitable form is established through physical or numerical modelling. Then, service loads are applied to this form to determine its ability to resist these loads in service.

Membrane Action and Bending

Under theoretically ideal conditions, a gridshell will develop exclusively axial stresses through membrane action. However, practically speaking, this is not achieved since variations in applied service loading, the need to provide edge restraint and aesthetic considerations will almost always give rise to localised bending and shear within the gridshell. Having said this, the design objective should be to utilise membrane action to the greatest extent possible.