Structuring Biomimicry, Improving Building’s Resiliency
The same way Einstein assumes the speed of light to be a constant of reference for his Theory of Relativity, the philosophy of biomimicry assumes Nature as a constant of reference to a performance-based beauty for design.
Imitating nature has become a meaningful approach for contemporary architects and design futurists to the built environment, especially for those who foster a future that doesn’t compete with nature but coexist with it. At the light of recent natural disasters around the world, especially those geologically associated such as tsunamis and earthquakes, which have proven its destruction power over the current built environment; architects and structural engineers have found in biomimicry an ecological approach in order to improve future building’s disaster resilience.
Bio-Structural Analogues in Architecture, by the Singaporean architect Joseph Lim (2009) emphasize that “central to the idea of a design strategy in developing the architectural concept, is a form of technological thinking which drew inspiration from other forms of knowledge”. Scientific thinking on architecture has leaded a bottom-up approach for resilient structure’s design. As wrote by the biologist D’Arcy W. Thompson, every form in Nature is essentially the product of the diagram of forces acting on it or which have acted on it. That technological feature of the living structures proves to be a resilient parameter of its morphology, basically because its tessellation grows in intrinsic relationship with the ecosystem and its natural flows.
Present built structures are unresponsive to the Earth dynamics and aren’t completely adapted to the ecosystem flows of forces. This fact leads to an important concern of the global building industry about its resiliency capacity toward the future and its potential dangers by natural hazards. Geological associated hazards have caught great attention by the design community at important forums throughout the world. Recent major earthquakes throughout the world have proven the inefficiency of the current building paradigm and have warned building professionals to adapt structures in order to withstand future seismic events. Principles of a BioTectonic Culture master degree thesis takes Puerto Rico as a laboratory for the design of biomimicry-driven structures made of reinforced concrete in order to improve its resilient output.
Puerto Rico is a great case study model due to the active seismic faults around the island, the predominance of heavy materials for construction such as concrete and masonry, some unsustainable approach for structure’s construction and its dangerous vulnerability due to the existence of great percentage of structures designed and constructed following poor seismic regulations or even built without professional assistance. Puerto Rico has a particular environment, it is located at the boundary of two tectonic plates (the Caribbean plate and the North American plate) having the potential to produce a major earthquake with magnitude 8.0 or greater. In fact, according to the US Geological Service (USGS), at least four major earthquakes have been affected the island until 1918. Besides, Puerto Rico vulnerability combines dangerously with the fact that those buildings designed before the implementation of the 1987 Puerto Rico Building Code may be considered as inadequate to resist earthquakes events. Under this premise approximately 70%~80% of existing structures could be under risk.
Although present construction at the island includes all required seismic codes, there are still some design-construction principles that can be optimized in order to improve the building adaptation to a seismic event. Besides, concrete structures in Puerto Rico needs to adapt congruently to the current ecological trends in order to reduce pollution associated with cement fabrication. For the thesis proposal, such kind of resiliency standard was achieved focusing on a structural design concept inspired by the performance and material efficiency of a “state of the art” static model bio-structure: the human skeleton.
The research proposal aims to produce a concrete structure driven by the natural flow of the force generated by an earthquake within the material. Such kind of desired “force-driven form” founds great resemblance with organic bones. The human body and its skeleton adapts according to function and loads that are normally encountered. Because of these loads, for instance, femur bones in legs becomes thicker and bigger than other bone because it has to carry out about 63 percent of the body weight. In result, the compact tissue in each particular bone becomes thicker where it experiments greater loads, and decrease density according to loads declining. That technological feature translates each bone’s diagram of force into its morphology.
The human femur, the longest and strongest skeleton bone, provides optimum technology parameters for the design of structures located in seismic zones. The femur’s hollow shaft design provides maximum strength with minimum weight, ideal design features in order to reduce the seismic intensity on a structure. Using biomimicry principles, the research achieves the architecture of an adapted structural system of reinforced concrete capable to withstand, not only gravity loads, but lateral loads such as earthquake’s loads, in a more efficient way than a conventional structure.
As a matter of fact, reinforced concrete was conceived emulating a bone structural properties where the collagen provides tension resistance such as steel bars, and mineral provides resistance to compression such as concrete. The type of loads which experiments the femur are very similar to those in typical beams and columns: tension, compression and bending. Then, the bio-structural parameters selected from the femur includes the mid-diaphysis (middle-cross section) geometrical properties associated with its maximum stress resistance value (about 4,000 pounds per square inch); and its response to mechanical stress, according to the Wolff’s law, which implies that a bone’s anatomy reflects the common stresses it encounters. The proposal undertakes those biological features of the femur bone to extrapolate morphogenetic parameters to the building structure in order to improve contextual integration and encourage better use of concrete.
Based in the bio-tectonic technological features extrapolated from the femur, the product achieved was a non-prismatic lightweight components deeply related to the bending-moment diagram of the typical frames which is normally generated by the effect of the lateral loads. Hence, the earthquake typical effect on the frame becomes a key parameter to its morphology design. Furthermore, due to the same principles, a lighter frame was obtained which also represents an achievement because implies the decline of the earthquake general intensity on the building. The structure proposal achieves a force-driven morphology implying some grade of mechanical resilience, and ecological adaptation.
According to computational analysis, such proposal becomes highly efficient for seismic vulnerable zones because the total base shear (earthquake force intensity) was reduced due to the effect of lateral loads. Furthermore, the proposed architecture implies a reduction of concrete use for structures which also means a reduction of CO2 emissions. This fact becomes very important considering that concrete is responsible for 7 to 10 percent of global carbon dioxide emissions, making it the third largest contributor to Global Warming after transportation and power generation. Current trends indicate that the future of the building industry would be greatly associated to Nature and the living technologies. Structuring biomimicry is an effort to provide the building’s structures with the capacity to be responsive to environment in real time such as the living structures are. Furthermore, it is the definition of a novel paradigm which adapts current inert materials for construction to its ecosystemic surroundings in order to improve the built environmental resiliency.
Written by Wilfredo Mendez, M.Arch, AIT for IEET.org
Lim, Joseph (2009). Bio-Structural Analogues in Architecture. BIS Publishers.
Thompson, D’Arcy (1961). On Growth and Form. Cambridge University Press.