Architects almost can’t help drawing inspiration from nature. The outside spiral of Frank Lloyd Wright’s Guggenheim Museum resembles a nautilus shell; the light dappled ceiling of Antoni Gaudi’s Sagrada Familia cathedral recalls a forest canopy; and the Beijing National Stadium, built for the 2008 Olympics, is actually named the Bird’s Nest.
Those are aesthetic decisions, but nature can find its way into structural design as well. Human bones make great architectural models, and they could also inspire the next renaissance in sustainable architecture.
If you're designing a building, a lot depends on the materials you choose. Human bones are made from a composite, a fifty-fifty combination of calcium and collagen. Hydroxyapatite, the calcium compound, is incredibly strong but brittle---alone, it snaps as soon as it reaches its weight limit. Think of a bridge of diamond, another brittle material. “We would never build a bridge out of diamond, not because it's expensive but because it's so brittle,” says Ahmed Elbanna, a civil engineer at University of Illinois Urbana-Champaign. “It can carry a tremendous load, but if the load exceeds its strength, it will shatter without warning.” In your bones, the malleable collagen adds a flexible strength to the calcium, protecting your bones from shattering every time you do vigorous physical activity.
Bone gains strength and flexibility from that core material, but also from the way it cleverly layers its structural elements. That calcium-collagen composite actually forms long, tough fibers, and a glue-like substance cements those fibrils together into thick layers of parallel cylinders, like a bundle of fiberoptic cables. Those arrays criss-cross and finally radiate outward to build concentric cylinders called osteons---which combine with interconnected canals to make the smooth, white layer of bone. That's a lot of engineering to go into what looks like a solid material, but all that weaving and organizing makes bone resilient. A slender crack in a fibril won’t damage the fibril array because it has a bunch of other fibrils to back it up.
In addition to structural hierarchy and super strong composition, bones can evolve with your body. They have a natural tendency to grow in the direction of stress. As you develop, your bones strengthen and harden in the direction of weight while making voids in places where there’s no need for resistance. Even under uniform conditions, you don’t get the exact same bone design by default. Two femur bones in a regular person’s body have slightly different shapes, sizes and angles. They’ve grown resistance to weight in a number of directions---vertical, horizontal, and diagonal---and this built-in variability makes bones more resilient when accidents happen.
Traditional architecture with straight lines and boxy designs can be simple, easy, and cheap to build. But it's not as resilient in the face of disasters---and designing a new generation of buildings based on the performance of biological materials like bones could make them safer. “With the interest in biomimicry, it’s time to recognize that defects and disorder will be useful in construction,” says Elbanna. She wants to see more calculated irregularity in designs, following bones' bio-logic.
