Fire Spread in U-shaped Facade Structures in High-rise Buildings

U-shaped facade structure exists in a lot of high-rise buildings. A numerical simulation study on vertical fire spread in u-shaped structure was carried out. Influence of area and the width-depth ratio of the u-shaped structure on the fire spread was analyzed through fire spreading speed, stack effect and heat release rate. It was found that the fire spreading speed and stack effect in the u-shaped structure decreased as $A^{\ast}$ increased. When $A^{\ast}$ is larger than 0.0069, the influence of $A^{\ast}$ on the fire spreading speed and stack effect become very small. The maximum HRR was positively related with $A^{\ast}$ except for the case when $A^{\ast}$ is very small. As $K$ increased, the fire spreading speed and the maximum HRR first sharply decreased and then slowly decreased except for the case when K = 1. The relationship between stack effect and $K$ was very similar with the relationship between stack effect and $A^{\ast}$, but in an opposite direction. When $K$ is larger than 2.25, the fire spreading speed, the stack effect and the maximum HRR did not change obviously with K.