Suspension bridges, overhead power lines and some modern buildings all use catenary wire structures. But what exactly is a catenary curve, and what principle of physics makes this ubiquitous structure so useful?
In pure mathematical terms, a wire or string describes a sphere that hangs freely between two points. The word comes from the Latin “catēna” meaning chain. The parabola curves up symmetrically like an arch, but the catenary curve is asymmetric with a dipping profile.
This signature is created by the continuous pull of gravity on the suspended wire. The stress is evenly distributed along the length of the wire. This uniform tension produces a smooth and gently curved catenary when the wire is tightened.
The natural physics phenomenon at work is that the catenary curve distributes the weight of the wire so that the tension is uniform at each point. This makes a catenary an ideal structure for a suspension bridge. Uniform pressure prevents the bending force at the bridge.
Catenary curves have a minimum wall area for a given span length and wire diameter. This gives them physical strength. Fewer materials are required to create a catenary arch as opposed to a flat-width parabolic arch.
Considering the limited number of materials used, catenary structures also exhibit very high strength and stability. This combination of performance and strength makes catenary curves ideal for lightweight yet strong suspension bridges. Long lines distribute the weight evenly.
Overhead power and telecommunications cables use catenary curves to account for thermal expansion and line shrinkage. This catenary sag factor helps prevent overstressing and damage from temperature changes.
Modern flat masonry structures of steel and concrete are designed on the basis of catenary suspension principles. Catenary concrete shells enable the expansion of a horizontal roof using minimal materials through careful structural pressure.
The gates of the Sagrada Familia Basilica, designed by Antoni Gaudi, are an example of a rotating catenary entrance that falls right into the supporting columns
In summary, the natural physics behind hanging catenary wire systems enables efficient physical design with remarkable strength. Harnessing the effect of gravity on cables has enabled less labor-intensive design of bridges, power lines, and roofing systems through cognitive technology The catenary curve continues to inspire innovation . . . .