filip silov dissertation

An investigation into the impact of obstacles during evacuation of shopping centre in case of fire using

Pathfinder.

A dissertation submitted to the

University of Central Lancashire

In partial fulfilment of the requirements for the degree of

Bachelor of Science with Honours

In

Fire Safety Engineering

By

Filip Silov (G20596595)

School of Forensic and Investigative Science

Supervised by

Dr. Paul Caurrie

August, 2016

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Table of ContentsAbstract............................................................................................................................................2

Chapter 1: General introduction...................................................................................................4

1.1 Introduction.................................................................................................................5

1.2 Aim..............................................................................................................................5

1.3 Objectives...................................................................................................................5

1.4 Research methodology...............................................................................................5

1.5 Summary of dissertation.............................................................................................6

1.6 Main Achievements....................................................................................................6

Chapter 2: Literature review..........................................................................................................6

2.1 Introduction.................................................................................................................7

2.2 Standards and Regulations........................................................................................7

2.3 Simulation Program Basics (Pathfinder).....................................................................8

2.4 Performance Based Design (Behaviours of occupants).............................................9

2.5 Summary..................................................................................................................13

Chapter 3: Research....................................................................................................................14

3.1 Introduction...............................................................................................................14

3.2 Methodology.............................................................................................................15

3.3 Data..........................................................................................................................16

3.4 Analysis and Discussion...........................................................................................21

3.5 Summary..................................................................................................................23

Chapter 4: Conclusion and Recommendation..........................................................................23

4.1 Introduction...............................................................................................................23

4.2 Conclusion................................................................................................................24

4.3 Recommendations for Further Research.................................................................25

Annex A..........................................................................................................................26

References:...................................................................................................................................28

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Abstract

Abstract of a dissertation entitled an investigation into the obstacles during evacuation of shopping

centres in case of fire using Pathfinder submitted by Filip Silov for BSc (Hons) in Fire Safety

Engineering at University of Central Lancashire in April, 2016.

For the purpose of this research, the basic industry standard BS9999:2008 “Code of practice for

fire safety in the design, management and use of buildings” is analysed.

Specific related subjects are treated in normative annexes:

- Annex E (normative) Recommendations for shopping complexes;

- Annex B (normative) Recommendations for atria.

While the Atria definition more closely describes modern shopping centre design trends, it excludes

Shopping complexes. Annex E, on the other hand, determines basic recommendations for widths

of corridors only (no open space considerations), where dimensions should be increased according

to the size of obstructions. The whole subject obviously requires improvement in the regulatory

part. The aim of this paper is to conduct series of experiments, where influence of obstacles will be

researched and analysed. For the purpose of proper modelling, and focusing on the impact of

obstructions, a section of a typical shopping mall corridor was designed. The initial dimensions

comply with BS9999 recommendations. Different scenarios were created by changing of the

following variables: number, position and size of obstacles. Position means preserving of the

obstructions along the corridor centre line, but placing them away are adjacent to shop exit doors.

In addition, the software allows application of two occupant behaviour modes: Steering and SFPE.

Both were tested in order to understand the aspects of crowd evacuation theories in the designed

conditions.

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The outcome of the work has clearly shown that neither the number of obstacles in a same row nor

their position have any influence on the egress time, for any of the tested obstacle sizes.

It was expected, that decrease of escape route widths shall increase the evacuation time. The

previous expectation was confirmed for Steering mode, where paths are determined by current and

next point in the grid. The path determines the escape route, allowing occupants to make new

decision whenever they reach the next point. In SFPE calculation, which is described as flow

model, where walking speeds and flow rates through doors and corridors are the only limitations,

there was no increase of RSET regardless even for extreme obstacle sizes. Therefore, it is

concluded that prior to any simulation, the available evacuation models need to be carefully

considered and the right one applied for specific purpose. In addition, application of specific design

solutions in regards of evacuation management (positions of emergency signs, shifting of exit

doors from corridor centre lines, etc.) could encourage occupants to escape in a manner which is

defined as the SFPE mode. This of course only after further studies which need to be conducted.

Acknowledgments

First of all I would like to thank my family for their support during my work on this dissertation

because without them and away from them I was able to complete all points asked in dissertation

brief. However main part in completing this dissertation is of course my supervisor Dr. Paul Currie

who gave me a clear vision of what is fire safety engineering, and last but not least my housemates

who always supported me to study hard and become a Fire Safety Engineers.

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Chapter 1: General introduction

1.1 IntroductionNowadays, evacuation problem is critical since it is used in many applications. These applications

include sites where masses of people gather such as commercial shopping centres, sporting

events, transportation centres, and concerts. A relevant objective is how to consider the mobility of

pedestrians in an area in order to improve evacuation times. Focus of this research will be the

simulation analysis of evacuation of a large commercial shopping district, where particular attention

will be on impact of obstacles during evacuation. The aim of this paper is to consider the effects of

the obstacles and crowd distribution in evacuation process, to provide the occupants safety in

enclosed environments, avoiding and reducing the number of fatalities. Also, research objectives

will be to identify information that might be useful in building designing in regards of the existing

construction and safety regulations.

1.2 Aim The aim of this project is to investigate impact of obstacles during evacuation of shopping centres

in case of fire. Egress simulation will be conducted in the agent based evacuation simulation

program in order to improve evacuation standards in shopping mall.

1.3 Objectives To analyse are current standards and regulations in accordance of new tendencies of

shopping mall designs, particularly various types of obstacles being installed

To determine impact of size and location of obstacles on egress time, using Pathfinder

modelling software.

To investigate the impact of different models of human behaviour based on simulation experiment results.

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1.4 Research methodologyThe methodology of this project relies on simulation program (Pathfinder) which can help in

answering the aim and objectives together with literature review that can contribute in building up

fire and safety standards and evacuation procedures with efficient results on evacuation in

shopping centres with obstacles available. A simulation of evacuation was chosen as a

methodology based on interest and deep understanding how obstacles can impact evacuation in

shopping centres.

1.5 Summary of dissertationThis dissertation which is divided in four chapters is consisted of multiple investigations of how size

and location of obstacles are having impact during the evacuation. In first chapter general

information are written to explain to reader what is the main aim and objectives in order to achieve

results for this topic. Beside aim and objectives, research methodology and main achievements are

collected to answer all the important questions regarding the topic. Second chapter is consisted of

literature review from the British Standards to have knowledge about designing and modelling of

shopping centres which this topic is about. To achieve real designs and models of shopping

centres and to have as close as possible results, simulation of evacuation of occupants has been

conducted in program Pathfinder. All data together with results and explanation of each simulation

can be found in chapter three. Last chapter of this dissertation is about the conclusion and

recommendations for the future work where data from the previous chapter is collected to suggest

points that are important for the researchers who will have research on the similar topic. At last

annex can be found to show basic layouts of the shopping centre simulation which is conducted in

program for simulation of evacuation of occupants.

1.6 Main AchievementsSeries of simulations on how size and location of obstacles have an impact on time for evacuation

has been conducted in this research order to investigate the topic of this dissertation. Simulations

have clearly shown that number and location of obstacles didn`t result with significant delay in

evacuation. Indeed the most important factor in evacuation of occupants from the shopping centre

is their own behaviour in the set and circumstances. In conclusion investigation on influence of

obstacles should be further investigated, particular for shopping centre design as per modern

trends. Ultimately, this could be finalized with improvements in standards and design

recommendation.

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Chapter 2: Literature review

2.1 IntroductionIn shopping centres, any emergency situations may involve even thousands of persons. Design of

buildings, escape routes, emergency signs and location of exits are amongst main factors which

have effect on evacuation progress. In stressed behaviours while occupants are pushing each

other to get out of rooms in compartments, location of obstacles may affect time required for

occupant’s safe rescue. On the other side it is obvious that any obstacle or barrier placed on the

escape route of the occupants will reduce the time of traveling due to reducing occupant density

which gives increasing rate of flow (Parisi, D and G. Dorso, C. 2011). Dozens of papers argued that

obstacles may be a reason of reducing the time of evacuation and having a stable flow (Helbing, D

et al 2005), (Krichner, A et al 2003).

2.2 Standards and RegulationsThe most important thing during emergency situations in shopping centres is motivation to escape.

In researches of many fatal fires and evacuations, it was observed that occupants are likely to

underestimate how fire can quickly spread, and in combination with other factors such as usual late

warnings, the evacuation starts with delay. Instead of single level shops, multilevel covered

shopping centres came into use, with much different varieties of sizes of units, and more free

space between shoppers and barriers, which are not created for occupants. Old shopping centres

were likely planned to be designed in straight axial lines, where todays shopping centres are

designed with more complex circulation patterns, to have better and bigger pedestrian flow.

Structure material choice has become important factor in designing. Lightness in structure became

main aim in order to have a good design of shopping centre. Places where people gather such as

large open spaces or atria are more common. Accent on lifts and escalators are pointed in

shopping centres in order to make easy and fast circulation. As per entertainment part, fountains

and large displays are set in order to increase occupant shopping time together with facilities for

children and other uses that can be interesting to add in order to develop and improve existing

shopping centres (BS9999, paragraph E.1.1, page 332, 2008).

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The source of upper descriptions is found in BS9999:2008, Annex E (normative):

“Recommendations for shopping complexes”. Although this Annex is giving particular

recommendations for shopping centres, in section E.3. “Planning of escape”, only corridor type

areas are analysed. When obstacles are planned along the evacuation routes, it is recommended

to calculate the required width and substantiate the corridor width (BS999:2008, clause E.3.1.3.,

p.339-340 and figure E.5., p.341).

For atrium type of areas (cause E.1.4, p.333), reference is made to Annex B (normative)”:

Recommendations for atria”. In Section B “General” of this Annex, it is clearly stated that “The

principles presented in this annex are applicable to all building types containing atria other than: 1)

…3) malls in shopping complexes” (p. 262). Clause (B.4.2. “Escape routes” p.265) emphasizes the

specifics and difficulties of designing such areas, without any reference to obstructions in Atria

spaces.

In lack of specific recommendations, it is obvious that for the purpose of safety planning, one

should conduct evacuation simulations for areas designed with obstacles.

In order to get better understanding of the subject, the author searched for similar researches.

Several published papers of similar nature are found, such as: Public Evacuation Process

Modelling and Simulation Based on Cellular Automata (Zhikun Wang, 2013). Simulation of

Optimized Evacuation Processes in Complex Buildings Using Cellular Automata Model (Rong Xie,

2014). Simulation of Optimized Evacuation Processes in Complex Buildings Using Cellular

Automata Model (Rong Xie, 2011) etc. By rule, publications are focused on evacuation theories,

evacuation modelling and testing of specific software. Impact of obstacles is not analysed in

details, instead one can find standard statements that obstructions surely reduce egress time and /

or should be excluded from evacuation routes.

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2.3 Simulation Program Basics (Pathfinder)Pathfinder uses a 3D geometry model. Within this geometric model is a navigation mesh defined as

a continuous 2D triangulated surface referred to as a "navigation mesh." Occupant motion takes

place on this navigation mesh. The navigation mesh is an irregular one‐sided surface represented

by adjacent triangles. Pathfinder supports drawing or automatic generation of a navigation mesh

from imported geometry – including Fire Dynamics Simulator files [McGrattan et al., 2007],

PyroSim files, and Autodesk’s Drawing Exchange Format (DXF) files. Since occupants can only

travel on the navigation mesh, this technique prevents the overhead of any solid object

representation from affecting the simulator. When the navigation mesh is generated by importing

geometry, any region of the mesh blocked by a solid object is automatically removed. For overhead

obstructions, the mesh generator considers any obstruction within 1.8 meters (6 feet) of the floor to

be an obstacle. The navigation geometry is organized into rooms of irregular shape. Each room

has a boundary that cannot be crossed by an occupant. Travel between two adjacent rooms is

through doors. A door that does not connect two rooms and is defined on the exterior boundary of

a room is an Exit door. There can be multiple exit doors. When an occupant enters an exit door in

SFPE mode, they are queued at the door and removed at the flow rate defined by

SFPE. Occupants that enter an exit door in reactive steering mode are removed from the

simulation immediately (Pathfinder Technical References, page 3). Occupants are defined by

physical condition of the occupant and collection of parameters for visualization of the occupant.

Occupant properties are various, with speed, delay and size as most important Pathfinder

Technical References, page 6). Path is generated as motion between two waypoints: “current” and

“next” (Pathfinder Technical References, page 7).

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2.4 Performance Based Design (Behaviours of occupants)Path planning, steering mechanisms and collision handling are combinations which Pathfinder as a

program uses to control occupant motion. Each occupant is making a path to connect their present

position to the goal point, somewhere on the navigation mesh. This path takes charge in controlling

the route of occupants during the simulation. Occupants can change their route, if some other

factors such as collision with other occupants, but the motion of the occupants is always lead to

their chosen path. When the distance between occupant and nearest point on the path exceed a

threshold value, new path is generated in order to accommodate new situation. The main key to

behavioural modelling in Pathfinder is the path generation algorithm. In the present version of

Pathfinder, occupants can make their own course to the nearest or use specified exit, however the

framework can generate path to other goals such as preferred exits, other occupants and specific

rooms, so different behavioural options can be explored furthermore (Pathfinder Technical

Reference, page 9).

Steering Behaviour mode:

In steering system pathfinder moves occupants along their calculated paths and allows them to

respond with a change of environment. Inverse steering requires a set of projected points where

cost relative of each steering behaviour is calculated. In each second occupant is turning towards

the lowest cost steering point. Pathfinder in these situations uses a set of five vectors projecting

forward in order to divide occupants and calculate these points. Pathfinder uses three types of

steering behaviours which are seek behaviour, avoid walls behaviour and avoid occupant’s

behaviour (Pathfinder Technical References, page 9-10).

The Seek Behaviour:

Seek behaviour forces occupants to travel along the seek curve that is set, giving the location of

occupants pt0, one of the projected points pt 1 and the present seek curve (sc). The seek

behaviour is calculated by two vectors; vector leading from point pt0 to pt1 and the tangent vector

of sc. However, magnitude of the angle between these two vector is equal to the cost of seek

behaviour for pt1 (Pathfinder Technical References, page 10).

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The avoid walls behaviour:

In this type of steering behaviour occupant detects walls and steers to avoid collision with the walls.

This type of behaviour projects a moving sphere in front of the occupant in direction of the

projected point. The outlay of this behaviour is based on distance of the occupants that can travel

in direction of the projected point where occupant makes free zone away from any wall (Pathfinder

Technical References, page 10).

The avoid occupant’s behaviour:

During the simulations, this type of steering behaviour keeps comfort zone between occupant and

other surroundings simulated occupants. This behaviour first creates a list of occupants within a

frustum whose size is controlled by the velocity of the occupant. Then the behaviour projects a

moving sphere ahead of the occupant in the direction of the projected point. This sphere is tested

against another moving sphere for each nearby occupant. If none of the moving spheres collide the

cost is zero, otherwise the cost is based on how far the occupant can travel prior to the collision.

The closer this collision point, the higher the cost of the steering behaviour (Pathfinder Technical

References, page 10).

Collision Avoidance/Response

Wall and occupant behaviour will always pursuit to steer around obstacles but in some cases this

may not be always with perfect result. This issue can occur in crowded situation when occupants

cannot avoid pressure that is given from the other occupants and it will result by pressed tightly to

the walls or other occupants. When this situation occurs, additional collision is important in order to

prevent simulation to become in invalid state. Two collision handling situations can be occurred,

one of them is when more occupants collide, where second can be when occupant collide with and

obstruction set on the navigation mesh, for example wall, obstacles etc.

When collision handling is turned on, the occupant will stop at the earliest collision with either a wall

or another occupant for a given time step. If collision handling is off, the occupant will stop only at

the earliest collision with a wall (Pathfinder Technical References, page 11).

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SFPE Behaviour mode:

Pathfinder provides the option to calculate motion in an SFPE Mode. This mode implements the

flow‐based egress modelling techniques presented in the SFPE Handbook of Fire Protection

Engineering [Nelson and Mowrer, 2002] and the SFPE Engineering Guide: Human Behaviour in

Fire [SFPE, 2003]. SFPE calculations are described as a flow model, where walking speed and

flow rates of doors and corridors are defined. Three types of components can be defined in

navigation geometry of pathfinder simulator; doors, rooms and stairs. The place where occupants

walk is defined as room or open space. Stairs are defined as special rooms where speed of

occupants is limited by slopes. Doors are limitation of flow that connects rooms and stairs. In

Pathfinder corridors are not specialized type as per SFPE guide. However, corridors are modelled

as rooms with a door at the end. In this case corridors are taken into account as rooms with the

flow, controlled by doors (Pathfinder Technical References, page 13).

Collision Handling/Response

In this type of behaviour mode, there might be a chance that in scenario occupants will collide with

other occupants or walls. When collision handling is on, occupants have chance to control

collisions with walls and occupants, if it is off they will collide with walls only. Collision handling in

SFPE model is applied in two steps.

First step can occur before any movement is made for a time of step, and second occur during

movement. In pre movement step, travel velocity is pointed to force occupants to travel along the

obstructions. When there is obstruction as a wall, new velocity will make occupants to travel along

the wall. In case when obstruction is another occupant velocity will make occupant slide around the

occupant next to it. When the velocity has been adjusted around obstructions, occupants will have

new velocity for traveling. In case of moving stage, collisions are possible, but occupant in this

stage will stop at the nearest collision (Pathfinder Technical References, page 15).

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Solution Procedure

Pathfinder runs in a simulation loop that calculates movement at discrete time steps:

1. Update each occupant’s current target point.

2. Calculate each occupant’s steering velocity. .

3. Increment the current time step.

4. Move each occupant. This involves several sub‐steps:

a. Calculate the velocity for the current time.

b. If collision avoidance is turned on, detect potential collisions, and modify the desired velocity to

avoid the collisions.

c. Integrate the final velocity to find the maximum travel distance, and travel along the mesh until

this distance is reached or until the earliest collision.

5. Update output files.

(Pathfinder Technical References, page 17)

2.5 SummaryContent of the literature review is consisted from the part of the British Standards, Annex E where

designing of the shopping centres is explained in details. The same standards are used in

providing the basic layout for the simulations for this project in program Pathfinder. Standards for

designing the obstacles are also implemented in order for simulations to be as real as possible.

Beside standards and regulations, Pathfinder`s technical references are used to explain closely

how this program for simulation of evacuation of people works and it is also explained in details the

behaviours modes which are available in this program. Each behaviour mode is explained during

the literature review, from the small parts of what is the behaviour consisted of until the solution

procedures for this mode to be improved. Also, in both of the behaviour modes collision handling

and response is explained to have clear idea of how occupants are moving on the navigation mesh

of the simulator of evacuation of occupants.

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Chapter 3: Research

3.1 IntroductionThe research methodology on this topic is conducted by using an agent based program simulator

in order to research the issue of impact of obstacles inside shopping centre while evacuating the

occupants including all important perimeters for evacuation that must be done in order to reduce

evacuation time and loss of life first of all, and then other perimeters which are less important in

egress process in shopping centres. In this chapter main point that will be shown are how did the

simulation of egress is represented in simulation program together with how obstacles with their

number, size and location have an impact of evacuating of occupants in shopping centre. Beside

main points, evacuation path and time will be investigated in order to take all possible information

which will be important in further investigation. Also aim of this dissertation is explained and defined

during the simulation which is used in this work.

Many productive research designs can’t be achieved without hard and tiring research strategy

which can conduct experiments, case studies or even archival analysis (Margaret, 2009). To

respond to the planned aim and objectives, and hence to explore in detail on how obstacles have

an impact during evacuation in shopping centres and what factors are affecting egress time and

behaviour of occupants a simulation has been conducted in simulation program named Pathfinder

which is used in the world as a leading egress simulator. In fact, data produced in this simulation is

fundamental for success of this research and it is important academic study of field of Fire Safety

Engineering.

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3.2 MethodologyFor the purpose of this research, a layout has been designed, consisting of central corridor with its

length of 54 m, and width of 9 m (6m plus width of smallest obstacle of 3m) as required by British

Standards for designing of shopping centres (BS999, paragraph E.1.3.1, page 340). Along the

corridor, shops are set to increase reality of simulations with a number of people inside these

shops. The space is designed with loading of 600 occupants which are present at the moment of

evacuation. In order to investigate impact of obstacles, different numbers of obstacles are set in the

middle of the corridor with different sizes. Basic layout of shopping centre investigation is made

with no obstacles in order to set the initial time for safe evacuation. Considering modern tendencies

in designing of shopping centres, this investigation started with setting obstacles sized 3m x 3m,

leaving at least 6m of free space as per British Standards (BS999, paragraph E.1.3.1, page 340).

In order to find out the size of obstacles impacts occupant evacuation time, dimensions of

obstacles are raised from 3m x3m, to 4m x 4m and finally to 5m x 5m. Number of obstacles with

proposed sizes has been increased to 2, 4 and 6 and their position shifted (away and front of shop

exits) to investigate whether the density and location of obstacles has an impact during the

evacuation. As explained in Chapter 2, there are two types of occupant behaviour modes, Steering

mode and SFPE mode, and both are applied simultaneously through all simulations.

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3.3 DataBefore investigating the time for evacuation in presence of obstacles, two simulations were

conducted without obstacles in both behaviour modes just to investigate total time of egress. In

steering mode total time for evacuating with no presence of obstacles is 1 min 45 seconds, where

in SFPE behaviour mode time for evacuating 600 occupants without any obstacles is 1 min 42

seconds.

Simulation experiment no. 1: Obstacle size 3m x 3m

Investigation when obstacles are 3m x 3m, for 600 people, in Steering behaviour mode, when

obstacles are away from the exit of the shop maximum egress time for 2 obstacles available is 1

min 46 second, where if obstacles are in front of the shop egress time raises to 1 min 49 seconds.

When there are 4 obstacles, time to evacuate is 1 min 47 seconds, where if the obstacles are

positioned in front of the shop entrance time is significantly longer, so 600 occupants will need 2

min and 5 seconds to evacuate if there is 4 obstacles available. With total of 6 obstacles with same

width time to evacuate when the obstacles is away from the shop exit is 1 min 50 seconds, and if

the obstacles are in front of the shop evacuation time will be 1 min 51 seconds, which does not

have any big difference. Table 1 shows more clearly evacuation time and how much is increase or

decrease of egress time. In Annex A basic layout for this size of obstacles is show.

Table 1: Corridor width – 9m; Obstacle size – 3 x 3 m; Behaviour - Steering

No. of obstacles

Egress time (s)

Position - away from shop doors

Position – in front of shop doors

Increase (s)

2 1 min 46 s 1 min 49 s 34 1 min 47 s 2 min 5 s 186 1 min 50 s 1 min 51 s 1

As it is shown from table 1, number and position of obstacles has no significant influence on the

evacuation time.

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Using SFPE behaviour mode, with obstacles 3m x 3m with the same number of occupants,

evacuation time for 2 obstacles available is 1 min 42 seconds when the obstacles are away from

the shop exits, and if the obstacles are in front of the shop the evacuation time will be same when

the obstacles are away from the shop which gives us 1 min 42 seconds. When there are 4

obstacles time for evacuation is 1 min 42 seconds when obstacles are away from the shop, where

when obstacles are in front of the shop time for evacuation is 1 min 45 seconds. With 6 obstacles

available time for evacuation when obstacles are away from the exit door is 1 min 42 seconds, and

when the obstacles are in front of shop time will stay the same which is 1 min 42 seconds. Table 2

shows complete evacuation time for this occasion when obstacles are 3m x 3m in SFPE mode.

Table 2: Corridor width – 9m; Obstacle size – 3 x 3 m; Behaviour - SFPE

No. of obstacles

Egress time (s)



Increase (s)


As it is shown form table 2, there is no significant difference in evacuation times in SFPE mode,

regardless of size, location and number of obstacles, because in SFPE mode way out for

evacuation is represented as when each occupant follows the one in front of him.

From table 1 and table 2 it is clear that number, size and location of obstacles does not have any

impact in evacuation, but only the behaviour modes which are available in pathfinder simulation

program.

Simulation experiment no. 1: neither number nor location of obstacles in both steering and SFPE

modes has no significant impact on evacuation time. This result was expected, since the layout

was set as per directives of (BS9999, paragraph E.3.1.3, page 339-340, 2008). Minor increase of

evacuation time for case set in Table 1, 4 obstacles in different positions is due to the nature of

Steering mode. Neither there is significant difference between the two modes for similar sizes of

obstructions.

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Simulation experiment no. 2: Obstacle size 4m x 4m

Although it is recommended to conduct the designs with a pre-set size and location of obstructions,

in real life the tenants of shopping malls are expected to allow placing of larger sized mobile

console type sale units, despite the original and approved plans. Therefore, the author decided to

investigate what would be the impact on egress time in this situation. In Annex A basic layout for

this size of obstacles is show.

As clearly shown in Table 3, in steering mode, the egress time has increased compared to the

initial size of 3mx3m. However, there is still no influence of number or position of the obstructions.


No. of obstacles

Egress time (s)



Increase (s)

2 2 min 7 s 2 min 4 s -34 2 min 5 s 2 min 6 s 16 2 min 8 s 2 min 5 s -3

So far it can be concluded that 1 meter increase of obstacle size (or 16.6% decrease of free

movement corridor) resulted with prolonged egress of 15 seconds.

In case of SFPE behaviour mode, increase of obstacle dimensions did not influence the egress

time compared to the 3 x 3 m obstructions in experiment no. 1, Table 1 (difference of +/- 2s is

insignificant). It was expected that this experiment would show increase of the RSET, The author is

of the opinion that the simulation outcome is due to the basics of the SFPE mode: evacuation is set

as a flow, where occupants follow each other with a delay required for pass of the predecessor.


No. of obstacles

Egress time (s)



Increase (s)


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Simulation experiment no. 2: increase of egress time was measurable only in Steering mode. It can

be assumed that this type of behaviour is expected as more realistic in a real case scenario. Since

the occupants of a shopping mall, by definition, are not familiar with the occupied space and it

could be expected that instead of leaving the alarmed area following the row of people ahead, they

would pass on the opposite side of the corridor which is free in the moment (or as described in

chapter 2 for Steering mode, in order to avoid collision, their waypoint of lowest cost steering point

is located on the other free side of the exit passage.

Simulation experiment no. 3: Obstacle size 5m x 5mThe last set of simulations has been done with the same number of people and the same

dimensions of shopping centre but obstacles size has been raised to 5m x 5m which means that

there will be only 4 m of free space to evacuate. Two types of behaviour mode are set as in

previous simulations.

In steering mode, extreme under sizing of freeways (4m exit corridor width is 33% decrease

compared to 6m as specified in (BS9999, paragraph E.3.1.3, page 340, 2008), resulted with

additional 30s of egress time. The change of egress time has doubled for an additional 1m of

obstacle increase. In Annex A basic layout for this size of obstacles is shown.


No. of obstacles

Egress time (s)



Increase (s)

2 2 min 36 s 2 min 29 s -74 2 min 36 s 2 min 34 s -26 2 min 43 s 2 min 43 s 0

Similar to the outcome of experiment no.2, for SFPE mode there were only minor changes of the

egress time. It is clear that due to the initial theoretical settings of the SFPE mode, the simulation

results would repeat even for further expand of the obstructions. This means that SFPE mode will

possibly deviate from an expected outcome in a real situation, despite of the experiment results

(assuming that all other fire safety items remain unchanged).

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No. of obstacles

Egress time (s)



Increase (s)

2 1 min 44 s 1 min 45 s 14 1 min 46 s 1 min 45 s -16 1 min 49 s 1 min 49 s 0

3.4 Analysis and DiscussionMain purpose of this study is to investigate impact of different sizes of obstacles in shopping centre

and how obstacles have an impact on evacuation time. This study was conducted in program

which is used for simulation software for evacuation of occupants in any designed object. In this

research one area of an imaginary shopping centre (main corridor and adjacent shopping units)

was designed, applying basic British Standards (BS: 9999. Appendix E, page 339, 2008)

recommendations for width of corridors in similar areas and utilities Choosing to create one specific

area, allowed the Author to achieve most realistic scenario and to eliminate those space factors

which are not relevant to the subject of the Research. Simulations experiments were conducted by

creating multiple scenarios, where number, position and size of the obstacles were subject of

variations. In addition, two types of occupant behaviour modes were applied Steering & SFPE.

In steering mode, the calculations and path generation are calculated based on the choice of the

“lowest cost steering point

Tables’ 1 – 6 show results of different simulation scenarios, where each table shows calculated

egress times with respectively increased obstacle dimensions and behaviour modes.

It is obvious that for the designed size of shops and corridor, changes in number and distribution of

obstacles do not result with significant differences. This proves that occupants shall use the

available free space between the shops and obstacles, and that density and location do not

influence the ASET. However, it has to be noted that the density in particular shops is predefined

as per recommendation of the Approved Document B (ADB, Appendix C, Methods of

measurement, page 135, 2006), and further simulations could be done with overloading with

occupants.

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For the purpose of the results’ analysis, the author found that comparison of results by behaviour

modes and obstacle sizes would be of interest.

Table 7 below shows the comparison of the simulation outcome:

Table 7: Egress time comparison for different behaviour modes, Corridor width – 9m; 4 nos. of obstacles, position away from shop doors

Size of obstacles

Egress time (s)

Steering mode SFPE mode3 x 3 m 1 min 47 s 1 min 42 s4 x 4 m 2 min 05 s 1 min 44 s5 x 5 m 2 min 36 s 1 min 46 s

For same design, number and location of obstacles, the simulation is showing different results for

each of the modes. In further researches, choice of options for occupant motion should be carefully

considered.

In SFPE mode (Thunderhead Technical reference, page 13) the only obstacle are the doors, and

occupants are evacuated to the predefined exits (as designed and in evacuation plans) in a flow.

There are no restrictions on overlapping occupants.

In steering mode (Thunderhead Technical reference, page 9), occupants are allowed to make a

choice for their next waypoint, where the software model calculates waypoints of “lowest cost” and

next points are recalculated each time. Lowest cost is calculation is predetermined by the: seek,

avoid walls and avoid occupant’s modes behaviours, where each takes into consideration size of

physical comfort zones (which can be adjusted for the purpose of simulations).

Pathfinder’s typical case (IMO Test 10, Technical reference, Thunderhead, p. 1-2) is set to show

only the basics of the two available options for occupant motions. There are no obstacles in the

typical case. When placing obstacles in high density areas, where the occupants are not familiar

with the building and escape plans / routes. Steering mode allows each occupant to recalculate his

route after passing by any of the obstructions. The previous results with an (expected) occupant

behaviour, where people shall each time choose between two available sides of escape corridors,

and by shifting eventually increasing the length of their escape route (similar behaviour is common

in vehicle transport, lane shifting on congested roads).

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During the design phase, it is of ultimate importance to predetermine the real expected occupancy

in peak periods (e.g. weekends, holidays, etc.), as well as sizes, numbers and positions of the

obstacles. These must be clearly marked as fixed items in emergency and evacuation plans, and

further enlargement of any parameters must be prohibited.

For such areas (predetermined obstructions), one could consider specific application and design

for positions of warnings, exit route lights, emergency lights, floor exit indicators etc. None of these

items are included in the evacuation software occupant motion models, but they could direct the

occupants to enter in the SFPE mode. For example, one set of exit lights are usually installed in the

middle of the corridor, where placing two parallel sets over each of free escape lanes would have

an effect. Bottom of obstacles (mobile or fixed) could be equipped with emergency lights, arrows

showing towards lanes.

3.5 Summary Present designed partial area of a shopping mall (simple corridor with adjacent shops and one

escape route, assumed number of occupants) is used for the simulations investigating influence of

obstacles on the egress time form the area.

Several scenarios each with different number, position and size of obstructions were tested in both

Steering and SFPE mode of occupant motions.

Number and position of obstacles have shown no influence on the egress time. On the other hand,

as expected, increased evacuation time is proportional to the size of obstacles.

Simulation results have shown that for different for behaviour modes, egress time differs

significantly for different sizes of obstacles. These points to the importance of proper choice and

application of human behaviour assumptions for the occupancies subject of experiments.

The results also indicate the importance of determining of size, location and nature of obstacles

during the design phase and evacuation plans, without allowance of latter increase.

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Chapter 4: Conclusion and Recommendation

4.1 IntroductionThe aim of this dissertation was to investigate impact of obstacles in shopping centre in case of fire

using the program for evacuation Pathfinder. Different methods were conducted during the

research about the impact of obstacles in shopping centres, but the method which gave the most

results was a program for simulation of evacuation. The objectives were to analyse if current

standards and regulations in accordance of new tendencies of shopping centres designs, to

determine impact of size and location of obstacles on egress time using Pathfinder modelling

software and to investigate the impact of different models of human behaviour based on simulation

experiment results.

Current applicable standards recognize standard shopping centre areas, where the single corridor,

single level designs is considered as a dominant choice of the architects. In this case, the corridor

is often an escape route at the same time and the basic recommendations are either to eliminate

any obstacles, or if this is not the case, to widen the corridors for the width of the expected

obstruction. New trends of large multilevel open areas are not recognized nor standardised. The

author created one layout, which is initially in accordance with BS9999:2008 recommendations and

represents partial are a typical shopping centre corridor, occupied with obstructions and serving at

the same time as evacuation route. Subject of simulation experiments were different number,

location and sizes of the obstacles, as well as comparison of two different behaviour modes

available in the software modelling.

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4.2 ConclusionBased on the research conducted in this study, main conclusion may be as follows:

Current standards recognize obstruction in shopping centres only in corridor areas, and no

regulations are developed for the modern trended open areas with the variety of different

types of obstacles. The conducted simulations did not comply with the recommendations given

for corridor type of shopping centres.

Recommendations for Atrium areas escape route design are general and do take into

consideration any obstruction. Atrium areas (BS9999, Annex B, page 262), exclude malls in

shopping centres.

Many of the previous similar researches deal mostly with different behaviour models/software

algorithms, where obstacles are only part of the scenarios. It seems that particular influence of

obstruction located on the escape routes is not studied. Usually is just stated that the

obstacles do have influence on evacuation time, but the levels of this influence are not

calculated or investigated.

This research used a corridor type escape route and simulations have shown the following:

Number of obstacles doesn’t not have any influence on the RSET.

Location of obstacles (as long as they are distributed in one line) does not increase the

evacuation time (even when all obstructions are located in front of the shops).

Different behaviour modes do provide largely different results, confirming that proper choice of

escape algorithm needs to be careful selected prior to simulation experiments.

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4.3 Recommendations for Further ResearchThis research has involved conducting an investigation of impact of obstacles in shopping centre

during the fire using Pathfinder with a literature review that supported designing of corridor in

shopping centre to establish the background of investigation. The conducted Pathfinder simulations

were efficient in solving the aim of this investigation. Based on the conclusion given in point 4.2 the

following is recommended in further research of this area of interest:

to investigate expected human behaviour during evacuation from shopping complexes, where

current occupants are not familiar with the escape plans

Following modern design trends, development of legislative for “atrium” type shopping centres

(congested with series of various obstructions) should be considered

Investigate and determine specific recommendations for emergency evacuation signs (e.g.

shifting of warnings, exit route lights, emergency lights, floor exit indicators from centre line of

corridors to both escape passages; not allowing obstacles and exit doors to remain in the

same axis line)

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Annex A

Basic layout for shopping centre with obstacles size 3m x 3m.


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References:

1. “The Building regulations 2010, Fire Safety, Approved Document B, Volume 2, Buildings other

than dwelling houses, 2013”

2. BS9999 “Code of practice for fire safety in the design, management and use of buildings”,

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