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|Title: ||Improved social force model for building evacuation simulation|
|Other Titles: ||Gai liang she hui li mo xing yu jian zhu wu shu san mo ni ying yong|
|Authors: ||Yuen, Kit Yan ( 袁潔欣)|
|Department: ||Department of Building and Construction|
|Degree: ||Doctor of Philosophy|
|Issue Date: ||2010|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Pedestrian facilities design.|
Buildings -- Evacuation.
|Notes: ||CityU Call Number: NA2543.P4 Y83 2010|
xviii, 187 leaves : ill. (some col.) 30 cm.
Thesis (Ph.D.)--City University of Hong Kong, 2010.
Includes bibliographical references (leaves 147-155)
|Abstract: ||Over the last few decades, there were numerous model developments in the
field of pedestrian flow simulation. Most of these models try to simulate the
pedestrian's evacuation in buildings in case of fire or emergency situations. They also
look at capacity issues at bottlenecks such as rail interchanges and bi-directional flow.
A number of models for pedestrian movement have been developed in a variety of
disciplines. There are two distinct groups of models in macroscopic and microscopic
perspectives. The macroscopic models focus on the system as a whole, while
microscopic models study the behaviour and decisions of individual pedestrians, their
effect on other pedestrians around them, and the system as a whole.
There is a need to model the pedestrian behaviour for a range of applications
including event planning, resource usage, and urban planning. For instance, the
organizers of a large event in an exhibition hall require information on what areas are
likely to be congested so that management strategies can be developed and tested
before starting the event. Similarly, the designers of a shopping mall might be interested in how people move around their intended design so that they can place
shop entrances and seating in useful locations.
Recently, computer based analysis for pedestrians movement in buildings is
widely adopted by the fire researchers or engineers in performance-based fire
engineering study. However, the pedestrians exhibit different behaviours depending
on their knowledge of the environment and other personal characteristics. Unlike the
rules that govern vehicular traffic, there are few formal procedures or rules that govern
the pedestrian movement, resulting in often complex and chaotic movements.
Pedestrians are not restricted to lanes or specific routes. In general, they are restricted
by the physical boundaries around them such as the width of doorways or presence of
walkways and also the movements of their neighbours. As a consequence, the
modelling of pedestrian movements presents some specific problems not encountered
in other forms of transport modelling.
A full understanding of crowd behaviours normally requires exposing real
people to the specific environment for obtaining empirical data, which is difficult
because of such environments are often dangerous in nature especially in emergency
situations. Moreover, the major deficiency of the existing pedestrians modelling is the
adaptation of crowd behaviour that is extremely difficult to be described by
In addition to studying the crowd behaviour based on the observations and the
historical records, computer simulation may be a useful alternative that can provide
valuable information to evaluate a building design, to help planning process, and for
dealing with emergencies.
In this thesis, a modified computing pedestrian model, namely Improved
Social Force Model, has been developed to simulate the perception and the cognition
of a pedestrian in case of emergency evacuation. The algorithm of the model is
implemented based on the Social Force Model introduced by Helbing and Molnar
(1995). This model examines pedestrian movements as either positive or negative
social fields, in which a pedestrian behaves as if acted upon by external forces.
However, the decisions and interaction between pedestrians is an extremely
flexible and intelligent process. To provide more accurate results in pedestrian
behaviours, the physical features of pedestrian movements such as walking speeds,
acceleration, queuing, and herding behaviour must be accurately reproduced.
The motivation of this research comes from the need to understanding
pedestrian psychology and modelling pedestrian behaviour accurately. Some
parameters involving human behaviours will be introduced into the original Social
Force Model in order to improve the accuracy for the computing modelling.
In summary, two human behaviours will be added into an individual's walking
performance: herding behaviour and visual angle. By adding a herding parameter into
a pedestrian in an evacuation simulation is proved to be obtained a more accurate
result. However, herding behaviour could not be the same in all age of pedestrians. In
an Improved Social Force Model, the younger pedestrian, the larger herding behaviour;
as younger pedestrians have lower judgement in the wayfinding (searching for a
suitable escape route) so that they will follow the actions of others as a guide to
determine how they might act. In addition, under evacuation situation, pedestrians will
more concentrate on finding their destination (e.g. an exit) in order to leave the
building as soon as possible. Therefore, applying a visual angle of ±85° to the
pedestrians can achieve a more accurate simulation result.
Applying the concept into the algorithm of the proposed model, the predicted
values for each pedestrian and time step are calculated. The model consists mainly of
three terms. These terms are the desired velocity of motion of a pedestrian, the
interactions between pedestrians, and the interactions between pedestrian and
boundaries. Human behaviours, herding parameter and visual angle, are applied to the
second term when processing the algorithm. Then the last step in the algorithm is to
update of the position, velocity and acceleration of an individual for the next time step.
In proofing the performance of an Improved Social Force Model, two other
computational pedestrian movement models, Social Force Model and Simulation of
Transient Evacuation and Pedestrian MovementS (STEPS), were applied. Social
Force Model is a well-known pedestrian movement modelling and it was published in
the Journal of Nature in 2000 by Helbing et al.; Improved Social Force Model is
proposed by the author in order to improve the prediction of pedestrian movement
modelling which is based on the Social Force Model; STEPS is a commercial
application of simulation in pedestrian movement and it is well-validated in academic
and well-adopted in industry. Therefore, STEPS is being a benchmarking model in the
research so as to evaluate the performance of the Improved Social Force Model.
From the computational results of the pedestrian simulation for various
scenarios, it was found that the simulated escaping time of pedestrians in the proposed
model from the fire room is longer than the original Social Force Model by comparing
to the results from STEPS. The agreement of the proposed model is not expected to be
perfect since there are important variations among collected by different authors under
different layouts, situations, and cultures. However, an improvement is clearly visible.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b4086408|
|Appears in Collections:||BC - Doctor of Philosophy |
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