Timber Gridshell Reverse Hanging Method
Precedent Study - Weald & Downland Open Air Museum
Reverse hanging experiment is an effective method of generating gridshell of shell forms. The method is to invert the hanging chains, or the web network based on the principle of mechanical equilibrium. This method was wildly used by innovative architect when designing and form finding the shell structures such as the roof of Multihalle in Mannheim (Figure 1) and Lath Dome at the German Building Exhibition (Figure 2) by Frei Otto. (Li, Wu, & Borgart, 2015)
The Downland Gridshell Building was a n a c t i ve b e n d i n g t i m b e r g r i d s h e l l structure which is the first timber gridshell constructed in UK using slender oak laths. (Downland gridshell, n.d.) The construction of the gridshell was firstly assemble the gridshell as flat surface at the top part, using the scaffolding to support. Then the edge of the gridshell was lowered gradually to its final position. (Figure 3) The structure is interesting as its edges are straight when the grid is flat (Figure 4), but the final form have curved edge beam to provide better structural stability. (Figure 5)
Figure 1. Final Hanging chain model for Mannheim.
Figure 2. Lath Dome at the German Building Exhibition.
Note. From Case Studies in Structural Engineering, Frei Otto and the development of gridshells, Vol.4, p.41, by I.Liddell, 2015, Copyright 2015 by I.Liddell.
Note. From Form-finding of gridshells generated from hangingchain models by using the Dynamic Relaxation method and the NURBS technique, Proceedings of IASS Annual Symposia, Vol.17, p. 2, by Q. Li, Y.Wu. & A.Borgart, 2015, Copyright 2015 by IASS.
Figure 3. The Gridshell from the North. Note. From Downland gridshell by The Gridshell from the North, n.d., Wealddown. (https://www.wealddown.co.uk/explore/ buildings/further-reading/assembling-grid/?building=301). Copyright by Wealddown.
Gridshell Structure ‘The grid shell is a spatially curved framework of rods and rigid joints. The rod elements form a planar grid with rectangular meshes and constant spacing between the knots [nodes]. The form of a grid shell is determined by inverting the form of a flexible hanging net. To invert the catenary so that it becomes the thrust line of an arch free of moments is an idealisation. Analogously, inverting the form of a hanging net yields the support surface of a grid shell free of moments.’ (Hennicke & Schaur, 1974)
Figure 4. Downland Gridshell lath arrangement.
Figure 5. Downland Gridshell final form.
Note. From Downland gridshell by Downland Gridshell lath arrangement, n.d., Wealddown. (https://www.wealddown. co.uk/explore/buildings/further-reading/assemblinggrid/?building=301). Copyright by Wealddown.
Note. From Downland gridshell by Downland Gridshell final form, n.d., Wealddown. (https://www.wealddown.co.uk/explore/ buildings/further-reading/assembling-grid/?building=301). Copyright by Wealddown.
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