Brooklyn Bridge Engineering: Catenary Curve, Not Triangulation

Brooklyn Bridge's Structural Genius

The Brooklyn Bridge (completed 1883) uses a catenary curve for its main cables—not triangulation/trussing as the primary structural principle.

How It Works

• Main cables: Four cables, each 15.75 inches diameter, composed of 5,434 galvanized steel wires. They follow a natural catenary (hyperbolic cosine) shape under uniform load.
• Suspenders: Vertical wire ropes transfer deck load to main cables.
• Stiffening trusses: The deck incorporates a deep truss (triangulated!) to distribute live loads and resist wind—but the primary support is the catenary cable system.

Designers

• John A. Roebling: Designed, calculated all forces by hand (died 1869 from tetanus after site accident).
• Washington Roebling: Son, chief engineer (disabled by caisson disease).
• Emily Warren Roebling: De facto field engineer, liaison.

Innovation

First steel-wire suspension bridge. Longest span (1,595 ft) at opening. Combined catenary cables + stiffening truss = hybrid system.