On The Use Of Simulation Models To Study Elevator Evacuation Planning For Super High-rise Buildings

The emergency evacuation of ultra-tall buildings has attracted considerable attention from researchers worldwide. Ultra-tall buildings possess a complicated structure and a large number of occupants. Thus, evacuating all occupants using stairways in an emergency would result in serious congestion, thus reducing evacuation efficiency significantly. Moreover, evacuation through stairways to the ground floor for occupants on top floors as well as children and those who are disabled, old, and pregnant would very difficult. Thus, elevator-aided evacuation is necessary and important for ultra-tall buildings. The idea of using elevators as a fire escape is not new. For example, during the evacuation process of the 911 event, some occupants used elevators to escape safely in the early disaster stages.The International Code Council Building and Fire Codes and the National Fire Protection Association Building and Fire Codes have recently permitted the use of elevators for occupant evacuation during fires and other emergencies for all buildings as an alternative to the required additional exit stairway for high-rise buildings. However, the warning "In case of fire, do not use the Lift" or similar statements appear at each elevator landing in high-rise buildings. In accordance with this statement, people are educated and trained to use staircases for egress in case of fire. This concept has been in the human mind for many years. Considering this fact, when using elevators for fire escape, we should undoubtedly build a safe elevator system. Meanwhile, evacuees are required to be cooperative following the elevator evacuation plan. Thus, people’s attitude toward using elevators for evacuation should be explored. A survey is performed to investigate people’s attitude toward the use of elevators for emergency escape in ultra-tall buildings. The results indicate that most people are willing to consider using elevators as a fire escape when they are on high floors, especially with the guidance of firefighters. Further analysis indicates that the attitude toward the use of elevators as fire escape vary among people with different characteristics, including education background and experience in using elevators. Moreover, evacuation elevators of ultra-tall building have to meet requirements by the building codes and address a series of technology issues including driving system, air resistance, piston effect and smoke proof, vibration suppression of high-speed elevator, heat and wear resistance, smoke and water resistance.Elevator evacuation in ultra-tall buildings is affected by a number of factors such as building height, floor area, number of occupants on each floor, number of refuge floors, number of stairways and elevators, speed and capacity of elevators, door width of elevators, and the percentage of elevator users. Based on these considerations, an elevator evacuation model (EE model) consisting of geometric, stairwell, and elevator modules is developed. The geometric model defines the building structures of each floor where occupants are positioned. Pedestrian movement actually occurs in the stairwell and elevators. Pedestrian movement in the stairwell is described in the stairwell module, in which each pedestrian is simplified as a moving particle with social forces from the walls and other occupants. On the other hand, the movement of people in the elevator, as modeled in the elevator module, employs an elevator flow chart to describe the mechanical characteristics of elevator movement.To verify and validate the EE model, simulation results are compared with the experimental and survey results. Stairwell evacuation time from the simulation results is very close to that from the experimental results of an evacuation drill performed in Shanghai World Financial Center. The flow rate of an elevator door from the simulation results is close to that from the results of a survey conducted in the City University of Hong Kong. The EE model is verified and validated to be reliable and can be used to analyze elevator evacuation in ultra-tall buildings.With the validated EE model, theoretical and simulation analyses are further performed to deepen our understanding of the dynamics of high-rise building evacuation with the aid of elevators. Stairwell evacuation time is given by the total number of evacuated occupants per unit stair width. Elevator evacuation time is determined by the number of occupants evacuating per elevator, the single trip time of elevator, as well as the capacity and door width of elevator, among others. The percentage of elevator users has to be considered when occupants evacuate using both stairs and elevators. Furthermore, flow rate of an elevator door is found to be evidently lower than that of normal doors or passenger ways. The capacity drop of elevator door is attributed to the limited enclosure space, where occupants already inside will hinder other occupants from entering the elevator.Guidelines for elevator evacuation planning based on the capability required for normal use exist, but guidance for elevator evacuation planning in ultra-tall buildings remains lacking. A large number of simulation experiments have been performed using the EE model to explore the capability required for ultra-tall building evacuation with the aid of elevators. Guidance is established for elevator evacuation planning in ultra-tall buildings using a series of tables. These tables can determine the number of elevators required for refuge floors of different heights, the speed and door width required for elevators, the percentage of occupants that should be evacuated by elevators, as well as the number of stairways required to aid elevators in evacuation within a certain available evacuation time. It is found that by employing elevators in evacuation the number of required stairways can be significantly reduced, thus saving building space for commercial use.