How is the fire verification for steel linear elements performed?

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Fire verification requires a particular concern, because in the event of a fire outbreak it is necessary to count on the load bearing resistance of the structure for a specific period of time.

Advance Design can perform a fire verification of steel linear elements according to Chapter §4.2 (simplified method) from EN 1993-1-2.

For example, the steel structure from Figure 1 is considered. The fire resistance verification of steel elements is needed after an exposure time of 15 minutes.

Figure 1. The analyzed structure

The fire verification is performed only if the "fire verification" option, from the calculation assumptions window, is active. The fire exposure time can be set globally for the entire structure (Figure 2).

Figure 2. Fire verification – set the fire exposure time

Some elements can be exposed partially or totally to the fire. This can be set in their properties window (Figure 3). For all elements of the analyzed structure, three fire exposure faces are considered.

Figure 3. Properties window for steel elements – defining the number of the fire exposure faces

The fire verification is performed under the frequent combination of actions. So, at generation of the load combinations, the "Frequent" situation for serviceability limit state (SLS) is chosen (Figure 4).

The other parameters (maximum allowable deflections, buckling lengths and lateral-torsional buckling lengths) will be established in a similar way, as in an ordinary steel analysis.

Figure 4. General parameters of load case combinations

After running the Steel Calculation, the fire verification results are available from the "Analysis – Steel Results" toolbar. Here, the work ratios corresponding to specific efforts can be viewed, as well as a detailed fire verification for a selected element (Shape Sheet > Fire Resistance). Figure 5 and Figure 6 shows the work ratio corresponding to the F_x effort, respective to the Shape Sheet with fire resistance for one of the columns from the analyzed structure.

Figure 5. Fire resistance: work ratio - F_x

Figure 6. Shape sheet: fire resistance