Universal sacrificial-layer thickness independent of designed fire-resistance time for wooden fireproof-structural-elements bench-scale tests using fire-retardant Japanese cedar laminated-lumber in barrier

Universal design thickness of the sacrificial layer for wooden fireproof structural elements is studied to minimize necessary fire performance of the barrier to be inserted between the sacrificial layer and the load-bearing timber. It is necessary for the universal design thickness to prevent post-fire glowing combustion within the sacrificial layer against any fire exposure time shorter than the designed fire resistance time. Based on bench-scale tests on partial models of the sacrificial layer, the barrier and the near-sacrificial part of the load-bearing timber, the study recommends 25mm as the universal thickness of sacrificial layer for Japanese cedar.