Review and analysis of fire resistance tests of timber members in bending, tension and compression with respect to the Reduced Cross-Section Method

Abstract

The Reduced Cross-Section Method (RCSM) provides a popular method for the design of timber members exposed to fire, using an effective cross-section and mechanical properties at normal temperature. The RCSM was adopted from a single publication and was originally developed for single-span beams exposed to bending load. It has been introduced in Eurocode 5 for a large range of timber members, including columns under compression and members under tension. Recently, the applicability of the method and its extended applications were called into question on the basis of limitations and contradictions found by advanced simulations. This paper analyses a total of 153 fire resistance tests (117 members in bending, six members in compression and 30 members in tension) with respect to the RCSM. The analysis shows that (i) most of the references are of too poor quality, or are incomplete, to validate a design model, (ii) results with adequate information content showed a significant deviation from the RCSM, and (iii) that the RCSM may lead to a non-conservative design. For members in tension, results fit well with the RCSM, while significant deviations were found for members in compression. Members in bending show very large scatter. It is therefore recommended that the existing design approach in Eurocode 5 should be revised in order to include the results of advanced calculations and appropriate tests.