Design of timber gridded shell structures

Abstract

Engineering and architecture are close disciplines with much overlap. Co-operation between design team partners to combine their experience leads to successful building structures. The paper discusses the key issues in the design of shells, giving methods of categorisation to aid communication within the design team. There has been a recent move towards freeform shells and the paper shows the necessity of working these up from clear rational parameters rather than relying on a computer-generated image alone. It shows the key material parameters that need to be addressed in grid shell design and shows how results from model tests and smaller-scale precedents can inform choice of material and size of structural elements. A review of recent shell structures includes references to timber gridshells (Downland, Savill) comparing their form-finding, modelling and construction techniques with the Pods, Scunthorpe (construction start September 2009)

Gridshells in Recent Research—A Systematic Mapping Study

“…Examples from process are [23][24][25]. Verification contributions are also typically motivated by behaviour (19).…”

“…The review articles, marked red in Figure 8, mainly provide contribu-tions regarding the process and are mainly motivated by the design practice. Examples of review articles are [20,24,34]. The most typical study regarding the gridshell part is on global shape, without mentioning material or type, as seen in Figure 12.…”

“…Furthermore, the studies on bending active gridshells are mostly timber or composite regarding material. Examples from the bending active facet are [21,24,34]. The discrete gridshells, marked in red in Figure 12, typically focus on all parts or the node regarding the gridshell part.…”

Active Bending, a Review on Structures where Bending is Used as a Self-Formation Process

“…The Hooke Park Workshop (1990) [17] (sample G3 in Fig 1) was not a gridshell as such; however, using a set of elastically bent timber arches whose form is based on studies of the hanging model makes the approach similar to that used for the Multihalle Manheim. Both structures were engineered by Buro Happold where an outstanding knowledge in gridshell structures was developed [24]. This led to more recent examples such as the Downland Gridshell from 2002 ( Fig 5 right) [19] and the Savill Garden Gridshell (De Groot, 2007) [22].…”

Form finding and structural analysis of actively bent timber grid shells

“…A 'low-tech' method for building free-form structures using standard (bolted/screwed) connection systems is by bending initially flat elastic rods, such as solid timber planks/laths, to form actual continuous curves. For timber grid shells made of continuous bending members, two sub-10 categories can be defined [1] differentiating on the geometric parameters assigned to generate a grid on a surface: If screwed laminated timber ribs are arranged following geodesic patterns (shortest curve on a surface for two given points) the planks composing the rib will only be subjected to torsion and bending around the weak axis [2] enhancing the 'allowable' width of the the plank's cross section.…”