Fire Resistance of Steel Structures – A Designer’s Guide

Steel is the foundation of modern construction, yet the fire resistance of steel structures is a key parameter that designers must consider to ensure the fire safety of buildings. To precisely select protection systems, it is worth understanding the mechanisms to which steel is subjected at high temperatures. At WOST S.A., we support engineers by providing complete technical data necessary for reliable design calculations.

Principles of Calculating Fire Resistance of Steel Structures

During a fire, steel loses its load-bearing capacity as temperature rises. The material’s yield strength decreases, leading to the exhaustion of the element’s bearing capacity. In accordance with the EN 1993-1-2 standard, a key task is to determine the critical temperature (theta a,cr). For most steel elements, this limit oscillates between 500°C – 650°C. Once this is exceeded, the structure loses stability, which is why proper design of protective measures is so essential.

Section Factor Am/V and Fire Resistance of Steel Structures

In fire protection design, there is no room for guesswork. The basis is the section factor Am/V, which defines the ratio of the surface area of the profile exposed to fire to its volume. How quickly steel heats up depends on its geometry:

• Massive profiles (e.g., tees) have a low Am/V factor, meaning they heat up more slowly.
• Thin-walled profiles (e.g., small angles) have a high Am/V factor and require a more robust protection layer.

To correctly calculate these parameters, you need precise section data. At WOST S.A., we provide full information in our product catalog, which allows for accurate determination of the surface area and mass of each profile without the risk of error.

Fire Resistance of Steel Structures – Effective Protection Methods

To achieve the required fire resistance classes (R30, R60, or R120), intumescent paints are most commonly used. This is an intelligent solution: under the influence of heat, the paint expands, creating an insulating foam that effectively protects the steel from rapid heating. The effectiveness of this method depends on the Dry Film Thickness (DFT). This thickness must be selected individually for each element, based on the Am/V factor. Surface quality is also crucial – that is why it is worth using products with appropriate production parameters, available in our range of hot-rolled profiles.

Supporting Your Design Process

We know that an engineer’s work requires precision. That is why at WOST S.A., we have invested in digital tools that facilitate daily work:

1. Quick summaries: Our steel weight calculator instantly provides the data needed for cost estimation and preliminary analysis.
2. Technical data: Detailed geometric characteristics of profiles in our catalog allow for reliable engineering calculations.
3. Consulting: When a project requires an individual approach, our technical team is at your disposal. We encourage you to contact our technical department.

Thanks to a proper understanding of cross-section geometry and the use of reliable data from the manufacturer, you create safe and economical structures. We invite you to use our resources to ensure every project meets the highest safety standards.