Calibrated Modelling of Form-Active Structures ceciliebrandt
Form-active structures are a more rare building type but very eye-catching due to their slenderness, double curvature and overall elegance. From a structural perspective, they are particularly interesting because their shapes cannot be predefined but necessitate a form-finding step before the actual structural analysis. Additionally, their flexibility means that they undergo large deformations when subjected to external loads. This makes them difficult to analyse as finite element software is based on the assumption of small displacements. Some packages have the capability of analysing this more advanced behaviour by storing the stress state from a form-finding step as a separate load case, which are subsequently imposed during the analysis. This modelling set-up is not easily defined when the system becomes sufficiently complex; it is also very time consuming, making an exploration of multiple configurations infeasible. The correlation between the form-finding and analysis requires that both steps are performed within the same software to avoid losing important information, which furthermore has the effect of isolating the architect from the design process.
This research offers the ability to analyse form-active structures in a much more interactive environment, which encourages an informed exploration in the early design stage where both architect and engineer are involved in the process. This is facilitated by the improved stability of the physics constraint solver “Kangaroo2” developed by Daniel Piker, which makes it possible to input real material properties and thereby simulate accurate structural behaviour with meaningful output values. The underlying dynamic relaxation solving technique inherently deals with the large deformations associated with form-active structures. The behaviour of cables, bars, beams (with rotational symmetric cross section) and simple supports have been implemented as a plug-in that builds on top of Kangaroo2. Relevant case studies provided by Format Engineers combined with a collaboration centered around a Smart Geometry workshop have pushed the developments forward and enhanced the applicability of the design tool in practice.