RC shells background introduction

'Bubble' Shell by Heinz Isler

The inflated concrete shell was light, can span a long distance without column in between compared with concrete structure in the past. The origin of ‘bubble’ shells was firstly discovered by Heinz Isler with the observation of his pillow shape. (Figure 6) His thought about how to achieve the shell artificially was start from the framework. (Chilton & Isler, 2000) The wooden frame was used to anchor the boundary of the shell which fixed at a timber board, then he drilled a hole at the middle and sealed the connection to allow the air pumped in. (Figure 7) He also marked the mesh grid on the surface so that the inflation effect is easy to observe. However, the structure that he achieved for now have the negative curvature at the corner which will result in the reversal line of thrust. (Chilton & Isler, 2000) What Isler did was to round off the corner which allows the curved boundary at plan view and solved this problem.

Precedent Study - Deitingen gas station

Figure 6. Plumped up pillow - the inspiration for Isler's Bubble shells

Note. From Heinz Isler: The Engineer's Contribution to Contemporary Architecture.(p. 34), by J. C. Chilton and H. Isler. 2000, Telford. Copyright 2000 by Thomas Telford.

Figure 8. Square demostration inflated membrance model, with a square grid marked on the surface so that the effect of inflation is easily discernible. Figure 7. The original rectangular wooden frame inflated membrance model used by Isler to investigate his bubble shells.

Note. From Heinz Isler: The Engineer's Contribution to Contemporary Architecture.(p. 35), by J. C. Chilton and H. Isler. 2000, Telford. Copyright 2000 by Thomas Telford.

Figure 9. Acquiring the form by inflation of the membrance just as the plaster mixture is setting.

Note. From Heinz Isler: The Engineer's Contribution to Contemporary Architecture.(p. 36), by J. C. Chilton and H. Isler. 2000, Telford. Copyright 2000 by Thomas Telford.

Figure 10. Service station in Deitingen ́68, Switzerland by Heinz Isler – Form passive and compressive only structure.

Note. From Structural Implementation of Slender Concrete Shells with Prefabricated Elements, Journal of the International Association for Shell and Spatial Structures, 51-64. by P. Eisenbach and M. Grohmann 2017, Telford. Copyright 2017 by Philipp Eisenbach and Manfred Grohmann.

The cover of service station in Deitingen by Heinz Isler is an concrete shell structure designed by hanging membrane reversed. The structure is pure compressive structure and has a long span covering above the building, which is really effective in relation to the shell thickness. (Eisenbach & Grohmann, 2017) The minimal connection between the shell and the landscape makes the structure ‘floating’ above the ground, and become a part of the nature.