Effects of column grid spacing and beam grid configuration on consequences of hydrogen leakage accidents in underground parking garages

This study numerically investigated the effects of column grid spacing and beam-grid configuration on high-pressure hydrogen leakage, dispersion, and jet-fire accidents in underground parking garages. Results indicated that smaller column grid spacing strengthened confinement by top beams and enlarged the horizontal spread of flammable gas clouds (FGCs). The personnel burn radius was approximately twice the lethal radius, and smaller column grid spacing limited the spread of thermal radiation. Increasing secondary-beam density substantially expanded the FGC dispersion range and thermal radiation hazard zones. Among all configurations examined, the waffle slab exhibits the largest FGC volume, the fastest dissipation rate, and the most severe fire consequences. Its lethal radius reaches 1.8 times that of the other cases, with a maximum steel structural damage radius of 13.8 m . These findings provide a quantitative basis for fire-resistant structural design and accident prevention in underground parking garages.