The potential of gridshells with irregular topologies

Abstract

Gridshells have emerged as an elegant and aesthetic solution for the span of large distances. Their design tends to feature a regular triangular or quadrilateral topology. Recent gridshells akin to the glass roof at the Dutch Maritime Museum, make use of irregular topologies to extend the limits of such structures. Coupled with advancements in technology, irregular gridshells have become more cost efficient, however, research on the subject is still in its infancy. The objective of this study is to investigate gridshells with an irregular topology known as kagome, in comparison to the triangular topology. This dissertation explores the effect of the regularity or lack thereof in the topology of a gridshell with respect to varying section sizes and grid densities. The performance of both topologies was discussed – both in terms of structural and cost efficiency. The structural performance is measured in terms of its buckling load, using a finite element software to carry out an eigenvalue buckling analysis. It is found that the for the same self-weight, the kagome pattern provides comparable buckling loads to the triangular, especially for finer grid densities and larger sections. The buckling shapes exhibit the intrinsic rigidity of the triangular, which cannot be matched to any other topology. Since the kagome pattern features triangular panels, they significantly improve its in-plane shear strength and activate membrane action within the kagome pattern. It is also proven that the main form of buckling was generally shell buckling, at times coupled with other forms of instability. The selection of section size should be compared on the basis of the ratio with respect to the span of the gridshell rather than the length of the member. In terms of overall cost efficiency, it is highly probable that for the same cost, the kagome pattern buckles at a larger buckling load compared to the triangular. This is because the triangular topology is attributed to a high node complexity which governs the total cost of the gridshell. For coarser grid densities, the kagome functions more like a group of beams connected together with rigid joints. In fact, this explains its reliance out-of-plane stiffness. However, it presents new cost-effective and aesthetical possibilities while still performing decently. These results encourage the investigation of new irregular topologies which still feature triangulation to some capacity for in-plane shear strength but outperform the kagome topology.