Study Of Efficiency Of Occupants’ Evacuation In Escape Route Of Building Under Emergencies

During fires or other emergencies, occupants of buildings or specific areas need to escape from the hazardous location as quickly as possible. Efficient and safe evacuation of these occupants is a core research topic in the public security field. View from the current study, it is still very necessary to understand the evacuation dynamics and interaction between people and built environments in depth. It is found some research results that can improve safety and management of evacuation do not have a detailed description of application yet. Therefore, combined with the evacuation requirements as stated in various codes,research of constructing an optimized building environment to facilitate the evacuation of occupants is of important realistic significance. This study examines the evacuation of occupants through the escape routes of buildings by numerical simulation based on social force model. A scientific guideline for an efficient evacuation can also be implemented in the design of building structures, safe management of dense crowds, and formulation of an emergency evacuation plan.An evacuation model is established and validated through experimental data. Based on the social force algorithm, the model is created using the platform provided by AnylogicTM. As a representative continuous model, the social force model allows people to move in a continuous space that is flexible and accurate for complex scenarios. The social force model in this study is distinguished from the original social force model by including several movement rules. An announced evacuation drill was performed to collect experimental data and validate the model. The experimental results on the relationship between flow and density are generally in accordance with the function from the SFPE Handbook of Fire Protection Engineering. The evacuation was then repeated based on the modified social force model. As a key parameter in the dynamical model that needs to be calibrated, the desired velocities of evacuees, which range from1.4m/s to2.0m/s, are examined. The simulation results are in agreement with the experimental results on the imbalanced door choice pattern and relevant factors.With reference to the provisions in various codes, some requirements are given explicitly, such as the required number of occupants in a room with a single exit, the minimum width of the exit, the angle between two exits in a room, and the minimum width of the corridor and staircase. The evacuation simulation model is employed to investigate the effect of each corresponding building component on clearance (evacuation) time.The relationship between the number of occupants in a room with a single exit and clearance time has been studied. After the desired velocity for the simulation model is examined, the shortest mean evacuation time per person is achieved when30people are inside the room. Therefore, evacuating30people from a room with a single exit is the most efficient during emergency situations. The result is consistent with the requirements prescribed in Hong Kong’s Code of Practice for Fire Safety in Buildings. Moreover, the influence of the width of the single exit has also been investigated. A more intense congestion of people around the exit consumes more time for the evacuation. Given that the occupants in a smaller room can quickly approach the exit and easily cause congestion, an exit with a fixed width may not afford them to evacuate fluently. In general, the minimum width of exits in Hong Kong and Ireland (750mm) can cause an obvious difference compared to other shorter width for Room1(10m×10m). While for the evacuation from Room2(10m x5m), there is a significant improvement when the width of the exit is800mm. In consideration of there are two exits in a room, the exit choice of occupants in evacuation shall be involved and examined. The result indicates that the imbalanced use of exits can negatively affect evacuation efficiency. After investigating the influence of number of people on the clearance time for different angles, it is discovered that the clearance time decreases at33.4°and38.58°when60people and100people are evacuated, respectively.The characteristics of corridors can also significantly affect the evacuation of occupants. It can be found the critical width corresponding to each corridor is not less than2.0m regardless of length. If the building is sufficiently spacious, optimal evacuation efficiency can be achieved with a corridor width of2.0m generally. The simulation data show that for the corridor with three rooms at single side, the width of1.1m is suitable for30-m long corridor to achieve a comparatively short clearance time. This result is consistent with the requirements prescribed in the International Building Code and Life Safety Code. Besides, a wedge design that can be used at the exit doors and joints of corridors is proposed to improve evacuation efficiency. The simulation results show that the clearance time for wedge design is less than that for the rectangular design. Besides, the effect of length of the short side of the wedge on evacuation efficiency has also been investigated. By examining the effect of the angle β of the wedge,it is discovered that the evacuation time saving rate increases and then decreases along with the decrement of the angle. The maximum evacuation time saving rate is achieved when the angle β is between45°and53.13°.Additionally, in the study of occupants’evacuation in staircases, different drifts of direction choice of occupants when walking down staircases has also been investigated. A detailed description of the movement rule is presented and integrated with the social force model. When the drift is2, the corresponding maximum crowd density is the lowest for each flow rate. A numerical computation has also been conducted to identify the minimum width of the staircase. A comparatively more efficient evacuation is achieved when the staircase is1.2m wide, which is in accordance with the requirements of the Code for Fire Protection Design of Buildings.With the purpose of improving relevant requirements stated in various codes and to guarantee an efficient evacuation through the escape routes of buildings during emergencies, this study is expected to provide a scientific basis and an effective reference for achieving a safe evacuation.