Structure and daylighting performance comparisons of Heinz Isler’s roof shell based on variations in parametrically derived multi opening topologies

The Design of building envelopes consists of two major phases in two different disciplines: structural design, and climatic design. Additional performance criteria such as acoustics may also be considered based on the program of the space. In general, a mono-disciplinary approach to design evaluates performance in each discipline detached from other disciplines and sometimes in a hierarchical order. This may be due to disjointed parameters that affect the design and optimization process, as well as different expertise of the designers and engineers in each field. Considering some structures such as post and beam systems, this method seems appropriate since each discipline has little influence on other fields. This provides relatively adequate freedom for the designers to decide about different design variables, such as size and orientation of the apertures, material of the cladding and the structure. However, there are some other building envelopes in which making a design decision in one field largely affects the performance in other fields. These building envelopes which cover the architectural space have a high potential for an interdisciplinary design approach.
Heinz Isler is an engineer who has designed extremely efficient shells with excellent performance over time. Considering his works, there are a few shell structures which have one or multiple apertures, mainly designed to introduce daylighting into the space. But how have these apertures influenced the force flow and structural performance of the shell? What daylighting levels have they provided for the space? And by manipulating the size and number of these apertures, how may the structural and daylighting performance of a shell vary? This paper intends to look at a perforated concrete shell designed by Heinz Isler and assess its structural and daylighting performance. Then, the size, number and location of the openings is altered in order to observe the effect on the structural and daylighting performance of the shell. Rhino and Grasshopper are used as the modelling platform, while Karamba, which is a plugin for Rhino, is employed for assessing the structural performance, and the DIVA plugin for Rhino is employed to assess the daylighting performance. Finally, a comparison between different topologies is made using different numeric indicators. For structural performance, deflection, weight and maximum von Mises stress levels are considered, along with Daylight Autonomy on horizontal and vertical planes as the daylighting numeric indicator. The goal of this comparative study is to demonstrate tradeoffs among various performance criteria, regarding the relation between topology, structural performance and daylighting performance, and may be used by designers who consider multiple performance criteria in early design phases.