Why Steel and Concrete Built the Golden Gate Bridge

Material Choices for a Record-Setting Span

Steel — The Skeleton

• High strength-to-weight ratio: Supports the 4,200-ft span with slender towers and cables.
• Tensile strength: Main cables (80,000 mi of wire) carry the entire deck load in tension—steel's forte.
• Malleability & fabricability: Rolled into plates, forged into eyebars, spun into cables on-site.
• Corrosion resistance (with maintenance): Paint system (zinc primer + International Orange topcoats) protects in marine salt fog. Regular repainting is a permanent job.

Concrete — The Foundations & Anchorages

• Compressive strength: Tower foundations and massive anchorages (each 60,000 tons) resist the cables' inward pull—concrete excels in compression.
• Mass & stability: Gravity anchorages use sheer weight to hold cables; concrete is cheap mass.
• Fire resistance: Critical for anchorages housing equipment; concrete doesn't burn.
• Cost-effectiveness: Local aggregates + cement = economical for huge volumes.
• Durability in seawater: Proper mix design (low w/c, pozzolans) resists sulfate attack.

Synergy

Steel takes tension; concrete takes compression. The towers are steel (flexible, light) on concrete piers (stiff, heavy). The deck is a steel truss (light, stiff) on steel suspenders. This composite approach—standard today—was cutting-edge in the 1930s.