Eurocode 5 design in comparison with fire resistance tests of unprotected timber beams

It is generally recognized that heavy timber in fire conditions demonstrates high structural performance. Exposed timber chars which functions as an isolative layer which protects the inner material from heat and loss of load bearing capacity. Char has no significant strength, and therefore, as the char layer grows, the load bearing capacity of the timber member reduces under sustained fire conditions. For predictions of the load bearing capacity in a standard fire, Eurocode 5 (EN 1995-1-2, 2012) provides a reduced cross-section method (RCSM), in which a char layer and an additional zero strength layer are simply deducted from the cross-section for structural calculations. Furthermore, using the RCSM, the design strength of timber under fire conditions is assumed to be higher than that under ambient conditions.