Modeling the emergency evacuation of the high rise building based on the control volume model.

Simulation modelSeven scenarios are analyzed by using the various values of the parameters which influenced the evacuation process in the high rise building including walking speed, coefficient of flow rate and merge flow ratio.

Computer based simulation  (control volume model)

Walking speed, coefficient of flow rate and merge flow ratio.

Stage 1: the occupants evacuate the rooms and arrive at the exit of the floor. The  evacuation time is obtained by dividing the distance between the floor exit and the nearest room exit by the walking speed.Stage 2: the exit flow enters the stairwell and the stagnation occurs at the floor exit when the summed flow rates of all room exits in a single floor exceed the flow rate of that floor exit. The evacuation time is not measured until the occupants descended to the next floor.Stage 3: when the stair entry flow arrives at the lower floor and meets with the sources of exiting occupants, it is called ‘‘merge flow’’ (i.e. merge stage). This stage is assumed that the summed merge flow capacity of the n + 1th floor’s stair flow and the nth floor’s exit flow islarger than the maximum stair capacity. Stage 4: the simulation entered stage 4 when the number of the occupants of a single floor approaches the floor capacity. The maximum number of the occupants a floor can be obtained by two components: stair landing area (m2) multiplied by maximum crowd density of the stair landing (people/m2), and stairwell area (m2) multiplied by maximum crowd density of the stairwell (people/m2). The descending flow is consisted of both stair entry flow and the outflow of the floor. When the occupants fully load the stairwell, the stair entry flow between ground floor and second floor will keep the maximum stair flow.Stage 5: Formula 5 and 6 demonstrate that the higher the floor the smaller the flow rate of the floor when the value of the merge flow ratio is lower than a certain constant and the number of the stagnating occupants in the stairwell reaches the maximum. As a result, the occupants on the second floor take the lead in arriving at the ground floor and yet finish the escape behind others. On the contrary, when the value of the merge flow ratio exceeds a certain constant, the occupants of the roof floor take the lead in entering the stairwell.

Simulation

Simulate the dynamics of the evacuees and derive the evacuation times of the high rise building by using the control volume mode

In order to better align to the real-world evacuation process and understand the dynamics of the evacuees in time scale, it is expected that recent experimental studies on how walking speed and coefficient of flow rate changed can be built in this model in the foreseeable future.

To sum, it is found that the merge flow ratio influences sequence of floors to be evacuated and time required for complete evacuation when coefficient of flow rate and velocity of walking remained a constant. It consumes least time for total evacuation when merge flow ratio R is equal to 1. The occupants of the lower floors finish evacuation sooner when R is less than 1. The occupants of the higher floors arrive at safe areas sooner when R is more than 1, which is similar to NFPA method. The simulation results are also illustrated that with same walking speed value, the influence of coefficient of specific exit flow and specific stair flow is obvious. The higher the coefficient value, the shorter the total evacuation time is. When stagnation happened in the floors, increasing walking speed do not influence much in shortening the evacuation time.

Simulate the dynamic change of the evacuation occupants of the mass rapid transit station.The evacuation simulation process is divided into five stages and based on the assumptions of homogeneous flow with merge flow ratio where the exit flows from different floors meet and merge.