Fire & Risk Engineering Award of Excellence: Raffles City Chongqing, Chongqing

Allen Sun
Associate Director
Arup, Shanghai

Comparing Evacuation Analytics & Modeling in Buildings with Skybridges

Due to its connectivity across the “Conservatory” skybridge on top and a shared podium, the eight towers that comprise Raffles City Chongqing presented some distinctive fire and risk engineering challenges. Fire modeling analyses were conducted to assess the evacuation provision for the Conservatory and podium levels. This involved exploring the impact of a fire occurring in various locations (e.g. shops, atrium, and Conservatory) and of different fire sizes/growth rates. A comparative evacuation analysis was conducted, comparing the actual design with a hypothetical design of the five towers without the Conservatory, in order to assess how it might impact the speed of evacuation. Due to the limited global precedent for the design, several conservative assumptions were adopted, including maximum occupancy of people on all levels, pre-evacuation times being accounted for, and a fire blocking the widest exist on the Conservatory level, for all fire scenarios. The evacuation and fire modeling analysis demonstrated that under each fire scenario, people would still have enough time to evacuate, providing extra assurance that the conservatory did not negatively impact fire and risk strategies for the project. Structural fire engineering modeling using finite element analysis was also conducted for the Conservatory roof to optimize the structural fire protection required for the area, which resulted in most structural roof elements not requiring further fire protection.

Ultimately, the proposed design and evacuation strategy for the Conservatory level included 15 egress stairs with a combined width of 20 meters, which merged into 10 stairwells in five towers beneath. A connecting refuge area was proposed below the Conservatory level, which was sized to provide enough space for people to use at each connecting stair, reducing congestion.

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