Structural behavior of timber columns in wood crib compartment fire tests

Abstract

Timber framing is increasingly used as a load-bearing structural system in mid-rise and high-rise buildings. While extensive data exists from standard furnace tests, there is a lack of data on the fire performance of loaded timber members in full-scale compartment fires. Compartment fire tests are crucial to investigate a structure's performance under conditions where the fire is let to grow naturally with the fuel and oxygen present in the room and then let to cool down as the fuel burns out. This paper presents the findings from six fire tests performed on glue laminated timber columns in a custom-built compartment. Wood cribs are used as fuel. The columns, 3680 mm long with a 280 × 280 mm² section, are subjected to constant axial loading during the whole fire duration. Column design and loading are based on a 60-min fire resistance. The tests vary in opening factor, fire load, and wood crib size. Column failure was observed in the six tests, with failure times ranging from 35 to 71 min. In four of the tests, failure occurred after the gas temperature had started to cool down. Comparisons with tests on similar columns made in a fire resistance furnace allow comparing charring rates observed in standard conditions and in natural fires.