Engineers built bridges heavy and solid for decades, usually in the simplest way possible: by adding more and more material. That is to say, the idea was to build them heavy and solid enough that they would not buckle under pressure. There is a catch to this method, though. It's a tremendous quantity of costly, heavy stuff that will make buildings difficult to enter in one manner but susceptible to another.
There is a new method in the works to take the place of this outdated tactic, and it doesn't stem from an engineer's manual, but from the human body. Looking at the architecture of our own body, engineers are figuring out how to design bridges that not only must be lighter and stronger, but also efficient and beautiful. Such a work of art, termed biomimicry, is transforming architecture by mimicking nature's genius.
The human skeleton is an engineering marvel. It must be incredibly lightweight to allow us to move around freely, but also heavy enough to support hundreds of pounds of force per step. It must be firm to give us shape, but also slightly yielding to dampen impacts and not break. A bone is not a mass of solid stuff; it is a highly developed, clever structure. Even inside some bones is hollowed out, a hollowed-out marrow cavity.
Beyond that, a web-like, sponge-like trabecular bone. The web is not arbitrary; its fine struts and beams just exactly fill out the direction of maximum stress, the same way forces pass through the bone. Beyond that, a hard, compact cortical bone. It is this combination of a hard, hollow center surrounded by a reinforced shell that is ideal for the job. It is as rigid as it can be with the barest amount of material used, and it is this that the engineers would like to "borrow" when building bridges.
Material placement optimisation is the greatest thing that bones have to teach. In a rigid beam, all material in the center does no or minimal work; the top and bottom surfaces must support most of the load.
Bones understand this and eliminate the excess material in the center, similar to a steel I-beam. Bones do much more than that.
Using computer modeling and 3D laser scanning technology, the engineers are now able to simulate testing the actual trabecular web material of bone. They can visualize how it is denser where there are loads of stress and where it is thinner where there are not so many forces. This can be fed into the computer and utilized to create entirely new, organically shaped bridge supports and trusses. While in the past, designers would have been forced to design using rudimentary linear beams, essentially hollow tubes with no inner framework, it is now possible to design supports to resemble the interior of a bone—a sophisticated, intricate lattice that mimics the way forces try to dissipate naturally. It's like having no excess material. All the inch of steel or concrete is performing as required.
This forms much lighter bridges. A light bridge has the snowball effect of advantages. It only needs fewer heavy foundations, saving the cost and environmental impact of construction. It's earthquake-proofed as it doesn't have so much dead weight around. Saved material can be massive, saving time and the carbon footprint of the project. Additionally, this bone structure forms a construction that is not heavier but typically stronger.
By matching the material and forces on it with mere accuracy, the structure enjoys superior load distribution. It prevents the stress concentrations and points of weakness that will make cracks begin and develop. This bridge is strong and will withstand sudden stresses because its structure follows the natural rules of load-carrying that took millions of years to evolve.
Constructing such a bridge is high-tech and natural. They start with computer simulations. There are computer programs specialized in performing "topology optimization." These computer programs are used by engineers. The machine is programmed by the engineers as to how the bridge will be braced and where loads will be applied.
And then there is a computer-simulated evolution, stripping the material away from the low-stress regions step by step until only the most effective shape is left. The final product is eerily biological-looking—a form that has grown, not constructed, in lovely, curved branching that appears to replicate the form of a femur or hip socket. Those fragile pieces, crafted from bone, would never have been possible to construct traditionally. But with robotic 3D printing and robot production now available, we can craft such bizarre pieces to precise specifications. Robots can build intricate formwork or weld specially designed steel members, interpreting the bone-based computer model.
It also creates more stunning and iconic buildings. The natural, curving shape of a bone-inspired bridge is a contrast to the functional, box-like shape of most contemporary bridges. They have the appearance of having grown directly out of the ground, with lines evoking nature.
The French Millau Viaduct, not at all truly bone-inspired, demonstrates this principle. Its tall, elegant piers rise, looking like the legs of a great beast, radiating an atmosphere of unimaginable lightness and loveliness in spite of its titanic size. Coming bridges that don't waste money on the lattice motif that mimics bones will look even more beautiful, being both art and functional utility. They illustrate how structure and function can stride hand in hand as one; the most logical design can be the most sensational. The mechanics of the bone material and even the shape itself are inventing new composites.
Bone is a composite material itself, consisting of hard mineral crystals and tough collagen fibers. It is the combination that provides strength (resistance to bending) and toughness (resistance to fracturing). Scientists are developing new cement and polymer materials based on this idea, with fibers in the material that suppress catastrophically growing cracks. It is a damage-tolerant material, deforming and signaling impending fracture, like a bone forming small hairline cracks without a complete fracture. This can result in safer bridges with enough time for engineers to repair flaws before they become catastrophes. Lastly, plagiarism from human bones is a matter of humility.
It is an acknowledgement that nature, after trying and failing for a billion years, has already solved many of the engineering problems we are still struggling to solve. Bone's strength-to-weight ratio is one that engineers have long dreamed about mimicking in designing grand, large buildings for decades.
As we look at its porous, optimally-ordered state, we're getting better at building not only more solid bridges, but also more elegant ones. They'll be fewer in resource terms, cheaper, more resilient against the forces of nature, and find their niche in the world in a new form of organic beauty. They are those in which our infrastructure is harmonized with the natural laws, and shows that the blueprint to the next great era of engineering wonders has been within us the whole time.