Galvanized Steel Boosts Fire Resistance in Construction Safety

Imagine a sudden fire outbreak, with raging flames consuming everything in their path. In such critical moments, the fire resistance of building structures becomes paramount. The solution to enhancing fire safety while maintaining structural integrity may lie in an unexpected material: galvanized steel.

For decades, galvanizing technology has been primarily valued for its corrosion protection properties on steel components—from small bolts and nuts to large structural sections. However, recent research has uncovered an additional benefit: galvanized coatings reduce the surface emissivity of steel, slowing its temperature rise during fire exposure. This discovery opens new possibilities for fire-resistant building design.

The primary challenge in designing steel structures for fire resistance lies in accurately predicting component temperatures at specific time intervals—a process typically requiring extensive iterative calculations. To address this, the Galvanizers Association and the Steel Construction Institute (SCI) have collaborated to publish design guidelines that simplify fire engineering for galvanized steel components.

The guidelines include:

• Fire design tables based on Eurocodes: Covering galvanized steel beams, composite beams, columns, and tension members with reference to UK and Irish national annexes.
• BS 5950 compliant design tables: Expanding applicability across different regional standards.
• Detailed calculation examples: Demonstrating practical application of the design tables.

The data reveals that galvanized steel can significantly improve fire resistance, particularly in structures requiring shorter protection periods (15-30 minutes). During these exposure times, galvanized components typically maintain temperatures around 500°C—preserving structural load-bearing capacity.

Building types that benefit most include parking structures, single-story residences, office buildings, and industrial facilities. Structures with automatic sprinkler systems may also utilize galvanized steel, as the fire suppression reduces required protection times.

The fire resistance improvement stems from galvanized steel's lower surface emissivity (0.35 vs. 0.70 for bare steel below 500°C). This property enables better reflection of radiant heat, slowing temperature rise. Since steel strength degrades rapidly above 500°C, even modest temperature reductions yield significant structural benefits.

Section factor—defined as the fire-exposed surface area (A) per unit volume (V) in EN 1993-1-2—also influences heating rates. Higher section factors accelerate temperature rise regardless of galvanization. For optimal performance, engineers must consider both material properties and geometric factors when selecting galvanized components.

Experimental data demonstrates that galvanized beams with section factors between 75-170 m ^-1 gain 2-3.5 minutes of additional fire resistance during 15-minute exposures. At 30 minutes, benefits persist for lower-section-factor beams (75 m ^-1 showing 3 minutes' advantage).

Load capacity analysis reveals more striking advantages. For restrained beams with section factors of 105-182 m ^-1 , galvanized steel provides over 30% greater load capacity after 15-minute fire exposure. Similar improvements occur for columns with section factors of 81-190 m ^-1 .

Multiple studies confirm galvanized steel's consistent emissivity of 0.35 across modern structural steel grades. Research by Sala, Heinisuo, and Czech Technical University established this value through calorimeter tests and full-scale furnace experiments. French studies at CTICM further validated these findings through standardized fire tests on various structural sections.

These comprehensive tests demonstrate that galvanized steel's temperature behavior can be reliably predicted using the 0.35 emissivity value, providing engineers with a robust tool for fire-safe design.