Large-scale compartment fires to develop a self-extinction design framework for mass timber-Part 2: Results, analysis and design implications
Why this work is in the frame
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Bibliographic record
Abstract
A bstract This paper seeks to provide key fundamental knowledge underpinning the use of self-extinction principles as part of a design framework for buildings with engineered mass timber structures. The results from six compartment fire experiments in a cross-laminated timber (CLT) enclosure with different ratios of exposed timber are presented and analyzed to establish the effects of timber exposure on the dynamics of a fire and on the potential of the fire to self-extinguish. The results show the relevance of four key parameters that need to be considered concurrently when assessing self-extinction in mass timber compartments: (a) the characteristic time for burnout of the movable fuel load, (b) the characteristic time for the occurrence of char fall-off, (c) the characteristic time for the occurrence of encapsulation failure, and (d) the heat exchange within the compartment after consumption of the moveable fuel. Self-extinction was attained only when the characteristic time for the occurrence of char fall-off was longer than the characteristic time for burn-out and the heat exchange after burn-out resulted in a heat flux below a well-defined threshold. The position of the exposed timber surfaces affected the magnitude of the threshold heat flux. If the characteristic time for burn-out was greater than the characteristic time for encapsulation failure, self-extinction was not observed to occur. • Six large-scale CLT compartment fires to establish self-extinction conditions. • Fuel burnout before encapsulation failure or char fall-off was paramount. • Oxidation of charring fuel created thermal feedback loop, hindering self-extinction. • Self-extinction threshold heat flux for timber surfaces dependent on orientation. • Char fall-off occurred in slim range unsuitable for unitary surrogate temperature.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it