Bio-inspired, Flexible Structures and Materials - Biotechnologies and Biomimetics for Civil Engineering - page 280

• Light Materials: Materials of low density combined with high mechanical
strength
• Light Structures: Following the flow of forces on minimal paths
• Light Systems: Integration of multiple functions into a single element
In Table 12.2 the engineering classifications of lightweight structure and nat-
ural design principals are compared, to identify natural construction principles
which may be consulted to find new engineering solutions for lightweight struc-
tures. Such a comparison may be used as a starting point in architectural design
and engineering when aiming to include biomimetic principles in the working
process.
12.4 Case Study Projects
The following two case study projects exemplify a typical direct top-down
approach (Flectofin ) and an indirect approach (M1).
12.4.1 Flectofin
The first case study followed a direct biomimetic approach. In this project, the
Bird-Of-Paradise flower, also known as Strelitzia reginae (Fig. 12.2 ), was chosen
as a role model because it features a sophisticated externally actuated pollination
mechanism. The motion is part of an elastic and reversible valvular pollination
mechanism, which is driven by the direct application of an external force. This
mechanism was intensively studied in order to reveal the underlying principles that
are responsible for the plant's mechanical performance. The plant's distinct form-
structure-function relationship was then further abstracted and inspired the
development of an elastic flapping mechanism called Flectofin . Exemplarily, it is
used for the conceptualisation of an adaptive façade shading system (Fig. 12.8 ), in
which the fins allow for opening angles ranging from -90 to +90.
12.4.1.1 Biomimetic Approach
As an adjustment to its relatively large and heavy pollinators (mainly birds), S.
reginae has developed a protruding perch of two adnate petals that act as a landing
platform. When a bird lands on this structure to reach for nectar, its weight causes
the perch to bend downwards, as shown in Fig. 12.2 . This initial deformation
triggers a secondary sideways flapping of two thick petal wings. As a result, the
previously enclosed stamens are exposed and pollen is transferred to the bird's
feet. When the bird flies away, the open perch resets to a protective closed state