Shadowing Effect in Fire Resistance Design According to EN 1993-1-2

Tips & Tricks

For unprotected I‑sections, the standard provides the correction factor ksh according to Equation 4.26a in Chapter 4.2.5.1 (2) to consider the shadowing effect. A term [Am/V]b is used there. This section factor includes Am, which represents the box enclosing the cross‑section (Index b = boxed). In the case of a three‑sided fire exposure (a girder with massive ceiling), the flange surface unexposed to fire is not taken into account when determining [Am/V]b.

Examples

Three-sided:
AmVb = h + h +bV

Four-sided:
AmVb = h + h +b + bV

h and b are outer dimensions of the cross-section.

There is no information in the standard regarding the determination of the correction factor ksh for three-sided fire exposure. In the RF‑/STEEL EC3 add‑on module, the correction factor ksh is always considered.

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RFEM Steel and Aluminum Structures
RF-STEEL EC3 5.xx

Add-on Module

Design of steel members according to Eurocode 3