What allows something as delicate as leaf or seashell to withstand something as relentless as wind or waves? These natural forms and their durability have been the subject of in-depth research by Professor Wanda Lewis at the UK’s University of Warwick as the School of Engineering looks to mimic nature in pursuit of urban infrastructure that doesn’t need repairs. Studying the design principles of ‘form-finding’ – which enables the design of rigid structures that “are sustained by a force of pure compression or tension, with no bending stresses, which are the main points of weakness in other structures,” – Lewis has been developing the mathematical models needed to replicate the strength found in nature in the urban world’s most precarious structure, bridges.
By using man-made materials that are form-finding, such as a piece of material or a metal chain, Lewis would suspend a piece of fabric, for example, and let it settle into its “natural, gravitational, minimum energy shape.” Then it would be made into to a rigid, physical object and inverted, and its coordinates are found through computation by simulating gravitational forces. This produces a natural form that can withstand pressure and force with ease.
The debate on how to build an optimal arch is one as old as engineering itself, but “nature’s design principles cannot be matched by conventional engineering design,” argues Lewis. While familiar models we see in bridges across the world are aesthetically pleasing, “we often build them regardless of the fact that they generate complex stresses, and are, therefore, structurally inefficient,” the professor explains. “The question of structural form is viewed mainly as an architectural matter concerned with aesthetics and function. In practice, the shape of an arch is imposed at the conceptual design stage,” reads the very first line of the potentially groundbreaking study published in June 2016 in Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science by the Royal Society, which goes on to detail Lewis’ mathematical models that respond to the failings of the only two existing attempts to crack the optimal arch dilemma; the inverted parabola and the catenary form.
Experts hope that Lewis’ nature-inspired model could usher in a new wave of disaster-proof design that help engineers build bridges that can withstand not heavy traffic and natural disasters with equal success.