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Tensegrity Structure at the Dubrovnik Airport: Idea and Design

The structural design of covering the bus platforms at the parking lot in front of the Dubrovnik Airport terminal (Croatia), required covering of approx. 90 meters of the path from the airport building to the buses. The design was led by the idea not to “smother” the Mediterranean atmosphere with the traditional steel or reinforced concrete structures, such as are very often used for city platforms. Instead, the desired transparency and lightness of the canopy was obtained by the tensegrity structure. The exceptional stillness of the bus terminal plan was put into contrast with the playfulness and voluminosity of the structure, the result of which was also inspiring. It could almost be said that authors’ wish was to construct a tensegrity in form of spine. The “spine” disks consist of compression triangle components – struts, through the center of gravity of which pass the horizontal compression zigzag strut. Three tendons which lie within the triangle connect the strut with their angles. Outside the plane, the triangles have been interconnected with tendons which are parallel with the “spine”. The planes among the triangle components have been additionally stabilized with side bracings. The structure is of modular type, the module having been made of two triangle components repeated along the “spine”. The structure vivacity has also been put into emphasis by skewed columns which have been additionally stabilized by family of cables. The initial shape of the structure (form finding) has been analytically defined. The system is self-equilibrating: the pretensioning forces within the structure are balanced, so there are no horizontal reactions due to vertical loading. The protection against the sun and rain has been realized by the membrane stretched between the side tendons. The membrane does not participate in the global bearing capacity. The structure is very light so the inertial forces during seismic action are very small, which makes this load type not relevant. On the other hand, the wind load is critical for this type of structure. Due to unique form and movement during wind action, each tensegrity structure has complicated pressure distribution. In this phase of the preliminary design, the wind load has been considered only statically, without relevant testing in the wind tunnel having yet been made.

Tensegrity spine; Zigzag strut; Module; Skewed columns; Analytical form finding; Self-equilibrating structure

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