COMSTRUCT
COMSTRUCT was a two-week workshop in summer of 2015 on computational structures as form generators, led by five tutors with 25 participants. The workshop aimed to explore material behaviours and directionality of elements, as well as understanding structural potentiality of complex geometries, utilizing algorithmic design and analysis potentials of Rhino, Grasshopper and Karamba, as well as industrial fabrication techniques to design and construct a one to one scale canopy.
The venue at the Contemporary Architects Association is located in a converted 30-year-old residential house, with an unused and empty swimming pool in the front yard. The task of the workshop was to design and fabricate a canopy covering the 4x10m pool to convert it into a vivid exhibition and public area. To this end, the parametric structural analysis program Karamba was used as the main tool to aid design development, from form-finding stage to optimizing structural shell and elements.
Experiments and studies on truss, shell and other structural elements with physical models and above-mentioned software led the students to the form-finding process for the final product. The goal was to identify an optimal shape for a structure covering the pool - maximize the use of materials while incorporating induced loading. A multi-objective optimization was performed using Octopus. E, where parameters for use of the material was combined with stress analysis calculated with Karamba engine. This resulted in a form of non-trivial nature; a concave shell cantilevered along its length, however still highly optimized concerning Self-weight.
After breeding an optimized shell structure, the surface was discretized into a folded pattern to increase the stiffness. Introducing origami-like principles the thin shell was given inertia while rationalizing the form in terms of fabrication. Among a bunch of rationalization techniques, triangulation was selected due to adaptability with the aluminium material that was chosen and metal laser cutting approach and by converting the doubly-curved canopy into a tessellation of planar surfaces. The structural performance of different tessellation patterns was compared resulting in an optimized folding methodology.
After settling in on a well-performing folding pattern, multiple load cases were introduced to simulate the structural behaviour from snow and wind loads. Analysing the now-folded shape with these loads, the utilization of each triangular panel was found. This utilization was then translated into the differentiation of hole sizes that was cut in the middle of each fold. These triangular holes were laser cut on two sides and bend around the last, rotating the cut material upwards with varying heights reflecting the local utilization, making the global performance of the shape readable in each local panel. The directionality of the folding methodology was such that two adjacent panels’ cut and bend material would meet and form an out-of-plane triangle. Adding a grid of cables to the system by joining out-of-plane points of these bend triangles, converted the shell into a double-layered structure and the outcome was a three-dimensional tension truss. Using Karamba, it was confirmed that all cables were activated –however some only under some load cases. To avoid pre-tensioning each cable segment, a continuous cable pattern was applied connecting all the nodes in a row. As each node connected four cable segments, the cables were weaved in and out with a zig-zag pattern. This method also implied that the cables could be pre-stressed from the ground after the structure had been erected. At the free edges, the cables’ end was hidden in a designed connection that incorporated an edge-beam.
After a two-week practice on the structurally driven design process with an interdisciplinary dialogue between architecture, structural parameters, and fabrication techniques, the structure was finally erected above the unused pool, converting it into an alacritous space for students gathering and public events of the association.