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<p>This study investigates smoke dispersion and toxic gas distribution in lower-deck vehicle fires on double-decker bridges through 27 sets of scaled experiments (1:8 model). Key findings reveal: windless conditions form stable ceiling jets, while crosswinds (&gt; 3.3&#xa0;m/s inward) disrupt stratification, creating hazardous turbulent smoke layers that reduce visibility to critical levels (e.g., 1.2&#xa0;m thickness at 200&#xa0;MW). CO<sub>2</sub> concentrations peak at 0.82% (16 × safe limit), CO reaches 13,352&#xa0;ppm (267 × threshold), with vertical concentration gradients showing 3 × higher toxicity near upper decks. Gas concentrations scale proportionally with heat release rate (200&#xa0;MW fires yield 1.5 × 100&#xa0;MW levels). Most adverse conditions occur at 2&#xa0;m/s outward and 4.4&#xa0;m/s inward winds, where flame attachment to structural members exacerbates gas accumulation. The empirical evidence substantiates restricting tanker trucks from lower decks to mitigate catastrophic fire risks.</p>

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Study on the Smoke and Toxic Gas from Vehicle Fires on the Lower Lane of a Double Deck Steel Bridge

  • 期刊论文

  • 发表日期：

    2026年3月17日

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  • Zhenchao Chai,
  • Jun Xu,
  • He Huang,
  • Ya Ni,
  • Jiqiu Qi,
  • Fangchang Shi,
  • Bolong Xu

摘要

This study investigates smoke dispersion and toxic gas distribution in lower-deck vehicle fires on double-decker bridges through 27 sets of scaled experiments (1:8 model). Key findings reveal: windless conditions form stable ceiling jets, while crosswinds (> 3.3 m/s inward) disrupt stratification, creating hazardous turbulent smoke layers that reduce visibility to critical levels (e.g., 1.2 m thickness at 200 MW). CO2 concentrations peak at 0.82% (16 × safe limit), CO reaches 13,352 ppm (267 × threshold), with vertical concentration gradients showing 3 × higher toxicity near upper decks. Gas concentrations scale proportionally with heat release rate (200 MW fires yield 1.5 × 100 MW levels). Most adverse conditions occur at 2 m/s outward and 4.4 m/s inward winds, where flame attachment to structural members exacerbates gas accumulation. The empirical evidence substantiates restricting tanker trucks from lower decks to mitigate catastrophic fire risks.