CLT Layer Fall-Off under Fire: Numerical Models and Probabilistic Analysis

Abstract This paper proposes an integrated framework for numerical modeling and probabilistic assessment of cross-laminated timber (CLT) layer fall-off under fire. First, a heat transfer modeling approach is developed to explicitly account for layer fall-off under standard fire exposure, where layer fall-off initiation is governed by a critical bond line temperature (CBLT) criterion. The developed numerical models are calibrated with published experimental data for CLT panels with varying configurations. Then, probabilistic models are established based on CBLT with an assumed probability distribution. The probabilistic layer fall-off time, temperature evolutions, and charring profiles of models are quantified. The variations of the section’s mechanical properties against exposure time are calculated, and a sequential thermal-mechanical analysis is performed. Subsequently, a surrogate model is trained to capture the relationship between the layer fall-off time and CBLT, and is coupled with Monte Carlo simulation (MCS) to evaluate the reliability of the post-protection factor, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="k 3" display="inline" overflow="scroll"> <mml:msub> <mml:mi>k</mml:mi> <mml:mn>3</mml:mn> </mml:msub> </mml:math> . Finally, the performance of the numerical model is tested on natural fire scenarios in terms of charring profiles and temperature histories.