Mark Donohue
I like to ask questions through the work I am doing. Questions of space, form, structure, light and geometry seem to persist as lines of inquiry. Being an architect and educator gives me a chance to explore these things with a diverse set of collaborators equally obsessed with making things. I am an Associate Professor at CCA as well as Building Technology coordinator. I write and lecture on issues of representation and digital technology. I am principal and cofounder of Visible Research Office, a multidisciplinary firm based in San Francisco. Through VRO I research new fabrication techniques and innovative materials and their application in the construction process testing out the research at varying scales.
This model depicts the inner geometry of a suspended helical stair (See above). An ascending spiral hyperboloid wraps around a double helicoid. The model was made to clarify the design of the suspended helical stair and to ensure that the geometries of the suspension cable system did not conflict with one another in supporting the stair structurally.
A unique cable system to suspend a stair was developed in collaboration with a leading structural engineer. The suspended cables form a double helicoid nested within an ascending spiral hyperboloid to create the necessary points of support for the gravity loads and lateral bracing for the seismic loads. Each concrete stair tread was designed as an independent element that is strung together with the stairs above and below it to form a single spiral stair when the steel cables that run through them are post tensioned. The entire stair tread and suspension cable system can be understood as a play of ruled surfaces with each part related to the other through their shared geometric lineage.