For today’s topic I want to consider biomimicry in relation to high-rise structural engineering. But first, what is biomimicry?
As defined by the Biomimicry Institute,
Biomimicry is an approach to innovation that seeks sustainable solutions to human challenges by emulating nature’s time-tested patterns and strategies.
The fundamental idea is that nature has the answers to many of our urban problems today; animals, plants, and microbes are the master engineers and we look to them for design inspiration in developing the world’s tallest structures.
After billions of years of research and development, failures are fossils, and what surrounds us is the secret to survival.
By combining structural system design and biology, engineers led by Mark Sarkisian at SOM San Francisco Structural Design Studio investigated the growth patterns of bamboo and the fractal geometry of the chambered nautilus shell for clues on how to design more resilient high-rise structures using fewer materials and increasing the inherent strength of the structural integrity.
They discovered that high strength-to-weight ratio, elasticity, long-term endurance, and a highly efficient form that resists loads and maximizes stability answered many of their design requirements and the results are truly captivating. Here is a synopsis of what they found:
Now let’s take this information and investigate a project to see just how nature’s mathematical formulas benefit the overall design process of high-rise buildings.
Below you see SOM’s entry into the Transbay Tower & Transit Center Competition for the City of San Francisco. Though not selected for the final design, it dynamically demonstrates “an inherent organic symbolism” and “creates a unique design derived from the forces experienced in San Francisco [wind & seismic activity].”
The structural grid, based on the derivation of the perfect cantilever by Anthony Mitchell in 1904, creates a bulbous shape with radial force flow lines modeled after the Fibonacci Sequence. Mimicking the spiral patterns of a nautilus shell and a hurricane, the following description by Sarkisian of the proposed structural grid discusses the culmination of force distribution through radial transmission:
“The spiral, which has the greatest resistance at the center and the least resistance at the outer arms, was translated into bracing that would resist the lateral loads where they were naturally the highest with the tightest part of the spiral and lowest where the bracing was more open. The diagonals radiate from the corners of the tower where forces are the highest and transform to more open geometries near the top where forces are lowest. The applied wind load increases with height, therefore it is best to reduce the building plan size to reduce the surface area that will be subjected to wind. integral forces generated by ground motions during an earthquake are collected within the superstructure and transmitted back into the ground. They too are attracted to supports in a radial fashion.”
This is an exceptional representation of how structural engineers are turning to the natural world to aid in solving today’s pressing urban design issues [including wind forces, seismic activity, economy of materials, efficiency of structural resisting systems and optimizing the balance between structures and environment].
SOM & others continue to pursue biomimicry as a tool for creating unique solutions to client’s demanding high-rise structural needs. It is truly awe-inspiring and tugs at my engineering heart-strings!