Lamella structures are formed of discrete structural elements that combine in two-way spanning grid systems. By arranging members in a grid pattern, long freeform spans can be achieved from relatively short members, and complex forms from geometrically simple components.
Reciprocal systems enable structural continuity within lamella structures through patterns in which beams mutually support each other. This is achieved by having elements typically twice the length of grid cell dimension and alternating the elements so that each one is mutually supported by its neighbours – so that the elements ends are carried at the mid-points of its neighbours. Reciprocal frames can similarly be created with a circular loop of mutual support, such as used on the Lake Bunyonyi theatre project.
A more complex variant of the reciprocal structure is the ‘nexorade’ in which elements meet eccentrically at connection points, forming pinwheel-like arrangements within the overall structure. Varying offsets of each connection can introduce curvatures into the grid, allowing freeform shapes to be created from relatively simple elements.
The reciprocal logic has historic precedent – as sketched by da Vinci and developed by Friedrich Zollinger in the 1920s into a roof construction system in which short elements are arranged in a diamond pattern as a regular reciprocal grid. Typically, the Zollinger system uses standardised lamellas that are arrayed to form singly-curved surfaces in barrel-like roof configurations. The system is very strong for its weight and can be assembled with minimal lifting equipment.
Contemporary CNC and robotic machining technologies allow the creation of different unique geometries for each element, enabling variation in element lengths and connection angles according to each member’s position within the system. A particular benefit of the reciprocal pattern is that end connections do not need to transmit bending moments.
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