How Bridge Steelwork Can Achieve a 120-Year Design Life

When it comes to bridge construction, longevity isn’t just desirable—it’s essential. At Bison Bridges, we take durability seriously, especially when working with steel. For inland installations, such as those in non-coastal areas of the UK, achieving a 120-year design life for bridge steelwork is both realistic and cost-effective with the right approach to materials and maintenance.

Using Hot-Dip Galvanised Steel for Long-Term Performance

A key component in achieving long-term durability is the use of hot-dip galvanised steel, which provides a protective coating that significantly slows down corrosion. Our standard specification includes galvanised steel bridge beams with an 85-micron zinc coating. This protective layer is the first line of defence against rust and environmental wear.

Expected Lifespan of Bridge Components

In typical inland locations within the UK, such as central counties, the average corrosion rate is around 1.5 microns per year, based on data from the Galvanisers Association. Using this as a baseline, steel beams have an approximate lifespan of 56 years before any major treatment is needed. This assumes the bridge is not subject to chemical exposure, de-icing salts or full submersion—factors which can accelerate deterioration.

How to Extend Steel Bridge Life to 120 Years

While hot-dip galvanising offers excellent initial protection, a proactive inspection and maintenance programme is key to reaching that century-plus lifespan. Here’s a proven strategy:

Steel Beams

• First Inspection: At 25 years, carry out a visual inspection to check for any surface corrosion or damage to the galvanising.
• First Maintenance: At 50 years, clean the entire steel surface and apply a protective coating such as ZINGA Film Galvanising System, or a commercially equivalent product, following the manufacturer's guidance.
• Ongoing Maintenance: Every 20 years, inspect and reapply the coating as needed. ZINGA and similar products typically carry a 20-year warranty, making this an ideal maintenance cycle.

Bolts, Nuts & Washers

• First Inspection: At 25 years, visually inspect for deterioration.
• Maintenance Cycle: Every 25 years, replace these components as necessary using galvanised equivalents to ensure continued protection and structural integrity.

Adapting for Other Environments

It’s important to note that this approach is tailored for inland, non-coastal areas. In marine or high-salinity environments, corrosion rates are significantly higher. In such cases, enhanced protective coatings, more frequent inspections, or alternative materials may be recommended to maintain performance and safety standards.

Why This Matters

By combining quality materials with a strategic maintenance plan, a steel bridge can serve its purpose for well over a century. For public infrastructure, private developments, and civil engineering projects alike, this approach supports sustainability, reduces long-term costs, and minimises disruption from future replacements.

Looking to install a long-lasting steel bridge? At Bison Bridges, we build with the future in mind. Get in touch today to discuss how we can deliver a structure designed to stand strong for generations.