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NOTES : * If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the letter from
the organization with period and reasons for confidentiality or restriction.
DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT
Author’s full name : MUHAMMAD SYAHRUL AMIN BIN SHAEDI
Date of birth : 20th of FEBRUARY 1989
Title : NUMERICAL INVESTIGATION OF ROAD BARRIER IMPACT CRASH
Academic Session : 2011/2012
I declare that this thesis is classified as:
CONFIDENTIAL (Contains confidential information under the Official Secret Act 1972)*
RESTRICTED (Contains restricted information as specified by the organization where research was done)*
OPEN ACCESS I agree that my thesis to be published as online open access (full text)
I acknowledged that Universiti Teknologi Malaysia reserves the right as follows:
1. The thesis is the property of Universiti Teknologi Malaysia. 2. The Library of Universiti Teknologi Malaysia has the right to make copies for the purpose of research only. 3. The Library has the right to make copies of the thesis for academic exchange.
Certified by:
SIGNATURE SIGNATURE OF SUPERVISOR
890220-14-5525 DR. ABD RAHIM ABU BAKAR
(NEW IC NO. /PASSPORT NO.) NAME OF SUPERVISOR
Date: 2nd of JULY 2012 Date: 2nd of JULY 2012
UNIVERSITI TEKNOLOGI MALAYSIA
UTM(PS)-1/02
Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
VALIDATION OF E-THESIS PREPARATION
Title of the thesis: NUMERICAL INVESTIGATION OF ROAD BARRIER IMPACT CRASH
Degree : BACHELOR OF ENGINEERING (MECHANICAL - AUTOMOTIVE)
Faculty : FACULTY OF MECHANICAL ENGINEERING
Year : 2011/2012
I MUHAMMAD SYAHRUL AMIN BIN SHAEDI
(CAPITAL LETTER)
I.C Number 890220-14-5525 declares and verify that the copy of e-thesis submitted is in accordance
to the Electronic Thesis and Dissertation’s Manual, Faculty of Mechanical Engineering, UTM.
______________________ _____________________________
(Signature of the student) (Signature of supervisor as a witness)
Permanent address:
4773-1 BALAI POLIS Name of Supervisor:
SUNGAI BESI DR. ABD RAHIM BIN ABU BAKAR
57000 KUALA LUMPUR. Faculty: MECHANICAL ENGINEERING
Note: This form must be submitted to FKM, UTM together with the CD.
“I hereby declare that I have read this thesis and in my opinion this thesis is
sufficient in terms of scope and quality for the award of the degree of
Bachelor of Engineering (Mechanical - Automotive)”
Signature : ..........................................................
Name of Supervisor : DR. ABD RAHIM ABU BAKAR
Date : 2nd of JULY 2012
NUMERICAL INVESTIGATION OF ROAD BARRIER IMPACT CRASH
MUHAMMAD SYAHRUL AMIN BIN SHAEDI
A thesis submitted in fulfillment of the
requirements for the award of the degree of
Bachelor of Engineering (Mechanical - Automotive)
Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
JULY 2012
ii
I declare that this thesis entitled “Numerical Investigation of Road Barrier Impact
Crash” is the result of my own research except as cited in the references. The thesis
has not been accepted for any degree and is not concurrently submitted in
candidature of any other degree.
Signature : …………………………………………………….
Name : MUHAMMAD SYAHRUL AMIN BIN SHAEDI
Date : 2nd of JULY 2012
iii
Dedicated to
My Parents, Shaedi Yahya and Hasimah Osman,
My Siblings, Mira and Azwan,
All my lecturers and fellow friends
Thanks for their immeasurable support and love
iv
ACKNOWLEDGEMENT
Alhamdulillah, I am grateful to ALLAH S.W.T. on blessing me in
completing this project. I wish to express my sincere appreciation to honorable
Dr. Abd Rahim Abu Bakar my supervisor of this project. Thank you for the
encouragement, guidance and critics. Without his continued support, idea and
knowledge received, this project would not possible to complete.
Besides that, I would like to dedicate my gratitude to my family especially
my mother Hasimah Osman also my father Shaedi Yahya for their love and
support. My sincere expressions also extended to all my colleagues who have
provided assistance at various occasions during completing my project. Their
guidance means a lot to me. Special thanks also to Mr Shauqy Amin and
Muhammad Adib and other staff for their guidance and help during the period of
this project.
Last but not least, thank you to all lecturers who allow me to grasp
valuable knowledge from them throughout a 4-year study in UTM. Those whose
names are not mentioned here, I will always remember your kindness and friendly
support. Thank you.
v
ABSTRACT
The main aim of this report is to predict absorption energy of road barrier and
to investigate the damage level of road barrier system under impact crash. The study
is focusing on the W-beam guardrail system which designed according to the
European standard EN 1317. The guideline of the testing simulation is based on the
NCHRP Report 350. ABAQUS/Explicit v6.10 software is used to simulate the
crashworthiness scenario of the W-beam guardrail systems under vehicular impacts.
Energy absorbing of the guardrail systems is studied for different values of the angle
of the vehicle during crash impact. The damage level of the guardrail systems has
been evaluated based on the maximum deflection during contact between the vehicle
and guardrail with the variation of vehicular speed as well as angles of impact.
vi
ABSTRAK
Laporan ini akan meramalkan jumlah tenaga serapan oleh peghadang jalan
dan menyiasat tahap kerosakan sistem penghadang jalan semasa berlakunya
perlanggaran. Kajian ditumpukan kepada sistem penghadang jenis Rasuk-W yang
dibuat mengikut standard European EN 1317. Garis panduan ujian simulasi adalah
berdasarkan kepada NCHRP report 350. Perisian ABAQUS/Explicit v6.10
digunakan untuk mensimulasikan senario perlanggaran sistem penghadang jalan
jenis Rasuk-W terhadap kesan impak kenderaan. Penyerapan tenaga sistem
penghadang jalan dikaji mengikut nilai-nilai yang berbeza dari segi sudut kenderaan
semasa perlanggaran terjadi. Tahap kerosakan sistem penghadang jalan telah dinilai
berdasarkan jumlah nilai pesongan maksimum semasa perlanggaran antara
kenderaan dan sistem penghadang jalan dengan variasi kepada halaju kenderaan dan
juga sudut perlanggaran.
vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xi
LIST OF ABBREVIATIONS xiii
LIST OF SYMBOLS xiv
1 INTRODUCTION 1
1.1 Background of Study 1
1.2 Statement of the Problem 2
1.3 Objective and Scope of the Study 3
1.4 Research Methodology 4
1.4.1 Description of Methodology 4
1.4.2 Flow Chart of Research Activities 5
1.4.3 Gantt Chart of Research Activities 6
2 LITERATURE REVIEW 8
2.1 Introduction 8
2.2 Overview of Road Accident Cases 8
2.3 Crash Barrier 13
2.4 Road Safety Barrier Types 13
viii
2.4.1 Rigid Barrier 14
2.4.2 Semi-Rigid Barrier 14
2.5.3 Flexible Barrier 15
2.5 Road Safety Barrier Design 15
2.5.1 Concrete Barrier 16
2.5.2 W-beam Guardrail 17
2.5.3 Wire Rope Safety Barrier (WRSB) 18
2.6 Behavior Under Impact 19
2.7 Model Description 20
2.7.1 W-beam 21
2.7.2 Post Model 22
2.7.3 Vehicle Model 24
2.8 Computer Simulation Study 25
3 METHODOLOGY 28
3.1 Introduction 28
3.2 Finite Element Method (FEM) 29
3.3 Tools Required 29
3.4 Development and Verification of an FE Model 30
3.5 Construction of The W-beam Guardrail Model 32
3.6 Parameter Selection 33
3.7 Computer Simulation 34
3.7.1 Part Geometries 36
3.7.2 Material Properties 38
3.7.3 Part Assemblies 38
3.7.4 Step and Field Output Definitions 39
3.7.5 Contact Interaction 39
3.7.6 Constraints 40
3.7.7 Load and Boundary Conditions 42
3.7.8 Mesh Properties 42
3.7.9 Job Analysis 44
3.8 Preliminary Test 44
3.9 Actual Tests 46
ix
3.9.1 Car Impact Crash 47
3.9.2 Bus Impact Crash 49
4 RESULT AND DISCUSSION 50
4.1 Introduction 50
4.2 Preliminary Results 50
4.3 Full Simulation Results 52
4.3.1 Damage Level 58
4.3.2 Energy Absorption 61
5 CONCLUSION AND RECOMMENDATION 66
5.1 Conclusion 66
5.2 Future Work 68
LIST OF REFERENCES 69
x
LIST OF TABLES
TABLE NO. TITLE PAGE
1.1 Gantt Chart UGP 1 6
1.2 Gantt Chart UGP 2 7
3.1 Dimension of Vehicle Model 34
3.2 Parameter Descriptions 34
3.3 Material Selection 34
3.4 Description of Tie Constraint 40
3.5 Detail of Mesh Components 43
3.6 Description of Preliminary Tests 45
3.7 Simulation Test Parameters 46
3.8 Description of Actual Car Tests 47
3.9 Description of Actual Bus Test 49
4.1 Description of the Preliminary Tests 51
xi
LIST OF FIGURES
FIGURE NO. TITLE PAGE
1.1 Flow Chart of Project Methodology 5
2.1 General Road Accident Data in Malaysia (1995-2010) 10
2.2 Road Accident Statistics for The Year 2002-2011
(Jan-May)
11
2.3 Statistics of Accidents, Injuries and Death Based On the
Type of Road in 2011
12
2.4 Statistics of Accidents, Injuries and Death Based On the
Weaknesses of the Road in 2011
12
2.5 Texas constant slope Barrier 17
2.6 New Jersey Type Barrier 17
2.7 W-beam Guardrail 18
2.8 Wire Rope System Using Double Curved Shaped Posts 19
2.9 Section W-beam Profile 21
2.10 Blocked-Out Steel W-Beam Guardrail 22
2.11 W-beam Guardrail System 23
2.12 A complete Bus Model 24
2.13 A complete Car Model 25
2.14 Barrier Deformation Using Simulation and Experiment
Test
27
3.1 A General Analysis Procedure for FEA 30
3.2 Overall Simulation Scheme 31
3.3 Components Model in W-beam Guardrail 33
3.4 Flow of Simulation Step 36
3.5 Components of Car Impact Crash Model 37
3.6 Components of Bus Impact Model 38
xii
4.1 Computational Simulations of Vehicle Impact Crash 55
4.2 Tearing and Twisting at the Guardrail Post 56
4.3 Damage Level at 550Mpa 59
4.4 Displacement of W-beam Guardrail under Impact Crash 60
4.5 Correlation between the Simulation Results and Previous
study 62
4.6 Numerical Analysis of Impact Crash Model of Previous
Study 63
xiii
LIST OF ABBREVIATIONS
RSB Road Safety Barrier
CAD Computer Aided Design
CAE Computer Aided Engineering
MIROS Malaysian Institute of Road Safety Research
PDRM Polis Di Raja Malaysia
JKJR Jabatan Keselamatan Jalan Raya
REAM Road Engineering Association Malaysia
AASHTO American Association of State Highway and
Transportation Officials
WRSB Wire Rope Safety Barrier
NCHRP National Cooperative Highway Research Program
LS-DYNA Dynamic Nonlinear Finite Element Code
FEA Finite Element Analysis
FEM Finite Element Method
RAM Random Access Memory
CPU Central Processing Unit
EN 1317 European Standard Norm of Common Testing and
Certification Procedures for Road Restraint systems
xiv
LIST OF SYMBOLS
km/h Unit of Kilometer per Hour
m/s Unit of Meter per Second
kg/m3 Unit of Kilogram per Meter Cubic
km Kilometer
m Meter
mm Milimeter ○ Unit of Angular
kg Kilogram
J Unit of Energy
s Second
1
CHAPTER 1
INTRODUCTION
1.1 Background of Study
Road barrier is an asset to traffic management and in term of safety, barrier
provides protection and shielded road users from hazard localize near the edge of
travelled way. In fact, road safety barriers play a major role to sign the driver on a
variety of dangers while on the road. For instance, barriers which were installed
along the edge of travelled way is to prevent vehicles from hazardous element such
as having a slope, mounds, a fixed object like tree or light poles and also a ditch.
Meanwhile, it can be used for multifunction like preventing the errant vehicle
entering the work zone and entering the opposing way with different types of barrier.
In most modern technology, manufacturers, nowadays, were producing
various types of safety barrier. The aim is to improve the safety aspect among the
road user. A good design is basically capable to withstand with various types of
vehicle at different impact condition. Furthermore, the safety barrier should deform
appropriately upon impact load conditions to minimize risk of injury to other roads
occupants.
Currently, more researches have been done in order to upgrade the
performance of the road safety barrier to increase the safety of the vehicle occupant.
These include designing and installation with some other significant method which
can maximize the effectiveness of the road safety barrier. This is because, the
existing guardrails do not give the perfect protection to the vehicle occupants from
2
the impact of collision or accident. As a consequence, it increases fatalities and high
severe injuries to the vehicle occupant and other road users. To provide appropriate
safety levels for impacting vehicle occupants, the safety barriers should be designed
in order to fascinate as much high kinetic energy as possible during the crash as well
as maintain the reliability [1]. For instance, the present guardrails were at a lower
level and looking for additional protection that can limit the vehicle from flipping
over [2]. Indeed, the road safety barrier should be improved with installation of more
effective road restraint systems.
For instance, when the vehicle hit the barrier, it will deflect upon impact. The
permanent deflections give the difference value relating to the different impact
conditions such as speed, angle, mass and vehicle type. Furthermore, different
distance spacing between the posts would generally have different performance
characteristics. Indeed, should be carrying out an analysis to discover the main factor
that leads to the failure. The numerical analysis will be conducted to determine the
energy of impact as well as the damage level effect on safety barrier.
1.2 Statement of the Problem
Road safety barrier is a device to separate the motorist from an area outside
of the roadway and is an important component in road and bridge area. From a safety
perspective, the ideal highway has roadsides and median areas that are flat and
unobstructed by hazards such as trees, light and sign posts, rough rock, embankments
and more. It also has potential to prevent the errant vehicle from crossing the barrier
and decelerate it without striking the fixed object or going down an embankment
localized adjacent to the roadway. However, the number of road accidents could not
be reduced. In October 2010, in the 6.40p.m accident, 12 people were killed and
about 40 others injured when a northbound express bus crashed through the guardrail
and turn over into five vehicles heading in the opposite direction. Therefore, the
further study should be implemented to determine the energy absorption and
maximum deformation of the safety barrier.
3
1.3 Objective and Scope of the study
The objectives of the study are as follows:
i. To predict absorption energy of road barrier and
ii. To investigate the damage level of road barrier
The scopes of this research work are to review the followings:
a. Impact crash by different moving vehicles
The simulations were carried out with two different vehicles which
are bus and car. This is to know which give the highest energy
absorbs and deformation to the safety barrier.
b. Road barrier design typically used in the highway
There are several types of safety barrier. In this study the scope is
focused on the W-beam guardrail.
c. Different collision condition
Several parameters need to set in this study. The change in parameters
includes the velocity of the vehicle and the angle of impact.
d. Simulate using FE software
A powerful finite element solver is needed to analyze the simulation
results. In this study, software ABAQUS v6.10 tool is required to
perform the computer simulation.
4
1.4 Research Methodology
1.4.1 Description of Methodology
The methodology consists of three (3) major elements:
a. Review of road safety barrier impact crash
All data related to road barrier likes design standard, material
properties, performance requirement of safety barrier and vehicles
will be reviewed from journals, books and research technical reports.
b. Computer modeling and simulation
Firstly, a model of safety barrier and the vehicles will be modeled
using SolidWorks software and it will be imported to the
ABAQUS/CAE software. The simulation is performed to determine
the impact energy and deflection upon impact of guardrail with
various impact conditions.
c. Evaluation of data results
Results from the analysis will be plotted and the characteristics of the
impact will be discussed. The results also will be compared to the
previous study analysis as well as secondary data in order to verify
whether the trend of deformation is similar to real cases.
5
1.4.2 Flow Chart of Research Activities
Figure 1.1: Flow Chart of Project Methodology
6
1.4.3 Gantt Chart of Research Activities
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
WE
EK
S A
CT
IVIT
IES
Pr
oble
m Id
entif
icat
ion
1.1
Cla
rifyi
ng th
e ob
ject
ive
& sc
ope
1.2
Rea
ding
on
rela
ted
thes
is
1.3
Gat
her r
elat
ed in
form
atio
n &
reso
urce
s
Lite
ratu
re r
evie
w
2.1
over
view
road
acc
iden
t cas
es i
n M
alay
sia
2.2
Stud
y of
the
type
s of R
oad
Safe
ty B
arrie
r 2.
3 St
udy
on th
e si
mul
atio
n m
etho
d of
cra
sh
test
M
odel
Gen
erat
ing
3.1D
evel
op a
Roa
d S
afet
y B
arrie
r C
AD
mod
el u
sing
Sol
idw
orks
201
0 so
ftwar
e 3.
2 le
arn
AB
AQ
US
v6.1
0 3.
3 D
evel
op si
mpl
e m
odel
usi
ng A
BA
QU
S
C
AE
tool
3.
4 G
ener
ate
asse
mbl
y m
odel
from
the
Im
porte
d pa
rt fil
e 3.
5 D
evel
op f
ull
scal
e cr
ash
sim
ulat
ion
test
Pr
elim
inar
y Te
st
4.1
Dev
elop
sim
ple
mod
el o
f th
e cr
ash
test
4.
2 C
ondu
ct si
mul
atio
n on
sim
ple
mod
el
4.3
Con
duct
sim
ulat
ion
of
simpl
ifyin
g m
ode
of
Roa
d B
arrie
r im
pact
cra
sh
Com
plet
ing
Dra
ft 1
5.
1 D
raft
1 Su
bmis
sion
Se
min
ar 1
– P
rese
ntat
ion
1 2 3 4 5 6
Tab
le 1
.1: G
antt
char
t UG
P 1
7
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
WE
EK
S A
CT
IVIT
IES
A
ctua
l Sim
ulat
ion
1.1
Con
duct
a si
mul
atio
n te
st f
or c
ar m
odel
1.
2 C
ondu
ct S
imul
atio
n te
st fo
r bus
mod
el
Dat
a Ev
alua
tion
2.1
Col
lect
the
sim
ulat
ion
resu
lts d
ata
2.2
Eval
uate
the
resu
lt ba
sed
on th
e
dam
age
leve
l 2.
3 Ev
alua
te th
e re
sults
bas
ed o
n th
e
en
ergy
abs
orpt
ion
D
iscus
sion
and
Con
clus
ion
3.1D
iscu
ssio
n on
the
ene
rgy
abs
orpt
ion
3.2
Dis
cuss
ion
on t
he d
amag
e le
vel
3.3
Com
pare
d to
pre
viou
s stu
dy
CA
E l
3.4
Conc
lusi
on a
nd r
ecom
men
datio
n
Com
plet
ing
Dra
ft 2
Se
min
ar 2
– P
rese
ntat
ion
Thes
is S
ubm
issi
ons
1 2 3 5 6 7
Tab
le 1
.2: G
antt
char
t UG
P 2
8
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
This chapter reviews the existing research as it relates to the objectives and
scopes of the study. The main findings cover on road safety barrier, typical impact of
the collision, different types of road safety barrier and vehicles, aspects of design
construction and the methodology for assessment of damage as well as structural
integrity.
2.2 Overview Road Accident Cases
Undeniably, road accident is becoming a serious problem in Malaysia. The
reason is accident claimed many lives besides disability and loss of property. For
many years, the number of vehicles registered has reached almost twenty million
which has been the most preferable, convenient and affordable mode of transport in
Malaysia. Assuming that 1.4 person per vehicle ownership in 2010 compared to 3.0
in 1995 as shown in Figure 2.1. Moreover, the total length of the road in Malaysia
had also increased from 62,221 km in the year 1995 to 111,378 km in the year 2010.
The increases of road accidents are related to the rapid growth in population,
economic in development, industrialization and motorization encountered by the
country.
9
Fatal accidents involving highway users still cannot be averted. Based on
Figure 2.2, it shows that a total of 178,698 of road accidents were reported, and from
that number, 2500 cases of accident involving death in the year 2011 from January to
May. The past few years have seen an increase in traffic accidents. From January to
November last year, a total of 5,753 cases involving fatal accidents recorded (2,464)
motorcycles, cars (1,428), trucks (559), bus (121), other vehicles (787), and
pedestrians (370). Instead of human behavior, the causes of accidents or injury are
also influenced by various factors such as roads, environment, and vehicle.
Moreover, the type of road is one of the contributors to traffic accidents. It is
found that the federal road showed the highest number of accidents which composes
of death and injury accident (See Figure 2.3). This is mainly because most motorists
would tend to drive exceeding the speed limit due to the lack of the speed limit sign
visibility at that particular road.
Road environment had also can be the causes of an accident. This factor
usually relates to the insufficient facilities provided along the road. As shown in
Figure 2.4, it is found that no street lighting, slick road and no guardrail are the
several causes of an accident. Without proper street lighting, this would lead to low
visibility especially at junctions during night times which increase the possibility of
an accident to happen. Besides that, no guardrail would also increase the possibility
of an accident as it exposes the motorist to various road hazards such as trees, light
poles and more.
10
Figure 2.1 : General Road Accident Data in Malaysia (1995-2010) [2]
11
Figure 2.2 : Road Accident Statistics for The Year 2002-2011 (Jan-May) [3]
12
Figure 2.3: Statistics of Accidents, Injuries and Death Based On the Type of Road in
2011[4]
Figure 2.4: Statistics of Accidents, Injuries and Death Based on the Weaknesses of
the Road in 2011[4]
3
42
147
50
36
180
61
29
84
20
20406080
100120140160180200
Urban roads State roads Federal Roads Others
Tota
l of A
ccid
ent,
Dea
th, I
njur
y
Type of Road
Statistics of accidents, injuries and death based on the type of road in 2011
Accident
Death
Injury
2 0 1 6 1 1
27112 0 1 9 0 3
33
147
0 0 0 7 1 012
68
020406080
100120140160
Tota
l of A
ccid
ent,
Dea
th, I
njur
y
Weaknesses of the Road
Statistics of accidents, injuries and death based on the weaknesses of the road in 2011
Accident
Death
Injury
13
2.3 Crash Barrier
Crash barrier is a feature on a road which is primarily designed to avoid
errant vehicle or motorist from leaving the road and protecting them from hazardous
features. These features should be installed where run-off-road accidents are
recorded to be high at each location which would result in the reduction of accident
severity[5]. It is required to provide protection occupants from such objects that may
result in accidents if the object is highly exposed. Thus, crash barriers should be able
to withstand the impact of vehicles of certain weights at a certain angle while
traveling at the specified speed by absorbing the impact energy during the collision
[1].
Ideally, the working principle of a crash barrier is hidden within the long
continuous smooth surface of the structure. Upon impact, the vehicle is redirected,
without overturning, to a path that is nearly parallel to the barrier face and with a
lateral deceleration, which is allowable to the motorist. These features are expected
to guide the vehicle back on the road while keeping the level of damage on the
vehicle as well as to the barriers within acceptable limits [6]. This is in order to
minimize the risks of injury to the passengers inside the vehicle. Also, safety would
be increase if the barrier with high absorption material properties is used for better
energy dissipation during impact of collision [7].
2.4 Road Safety Barrier Types
Generally, the availability of the crash barrier can be divided into three (3) specific
types:
• Rigid Barriers
• Semi- Rigid Barriers
• Flexible Barriers
14
The use of these three different types of barriers is correlated with the
different safety requirements of each particular road which varies in terms of their
deflection and energy absorption properties as well as their suitability for different
road characteristics. Safety and characteristics vary depending on the type of barrier.
2.4.1 Rigid Barrier
Rigid is referring to the deficiencies in or devoid to flexibility which does not
deflect upon impact. Indeed, rigid barrier has the limitation of the energy absorption
and this is accomplished by redirecting a vehicle away from hits it. Therefore, during
a collision, energy dissipation is achieved through deformation of the vehicle and
rising and lowering of the vehicle body [7]. The impact energy controlling by the
feature is able to redirect the colliding vehicle stably without any rolling movement.
These features usually made of reinforced concrete element connected with
deformable steel beam or plates are most suitable in locations where there is a
limited area for barrier deflection and perform optimally in collisions where the
impact angle is 15° or less [7, 8].
2.4.2 Semi- Rigid Barrier
This is partially rigid or not fully rigid where there have a small to moderate
deflection upon impact crash. Generally, this type can be classified into two (2)
specific groups [5]:
i. Strong Beam / Weak Post
The posts near the point of impact are purposely designed to break
away so that the force of the impact is distributed by beam action to a
relatively larger number of posts. Attributes of this system are
15
• Barrier performance is independent of impact point at or
between posts and soil properties, and
• Vehicle snagging on a post is virtually eliminated.
ii. Strong Beam / Strong Post
The posts near the point of impact are purposely designed to only
deflect moderately and the force of the impact is distributed by beam
action to a small number of posts. This is to be considered when:
• Minimal deflection is required
• Transitioning to rigid objects such as bridge parapets.
2.4.3 Flexible Barrier
Flexible barriers have the greatest deflection and energy absorption properties
of the three types of barriers, providing significant lateral deflection and thus
resulting in the lowest deceleration forces on vehicles, such as cars, and their
occupants [7]. It absorbs the impact kinetic energy through the posts, anchors and
pre-tensioned wire ropes and wrap around the colliding vehicle by stretches the
cables and post break. In addition, it guides the collided vehicle forward away with
minimal impact through the barrier rather than redirect the vehicle back to the flow
of traffic thus keep the vehicle to a minimum damage and reduce the risk of injury
[9].
2.5 Road Safety Barrier Design
Basically, there are three (3) different longitudinal traffic safety barriers
which normally install along the road in Malaysia namely:
16
• Concrete Barrier
• W-beam Guardrail
• Wire Rope Safety Fence
2.5.1 Concrete Barrier
A simple definition to describe about the mechanical properties of this barrier
is very strong and rigid. In that case, it does not absorb much kinetic energy.
Concrete barrier is one of the rigid types which do not deflect upon impact.
Generally concrete barrier systems are made up of separate interlocking sections
joined together to make a rigid and continuous smooth surface [7]. The purpose of
this barrier is to redirect collided vehicle to the right flow of traffic without any
rolling movement. Energy is dissipated with the deformation of the sheet metal of
vehicle [10]. However, the impact force can be extremely large if the vehicles itself
is very strong and rigid [11].
Commonly, concrete barrier can be specified into two (2) categories namely:
i. Constant slope barrier e.g. Texas constant slope
ii. Multi slopes barrier e.g. New Jersey Type
17
Figure 2.5: Texas Constant Slope Barrier
Figure 2.6: New Jersey Type Barrier
2.5.2 W-beam Guardrail
Nowadays, a W-beam guardrail type is the most appropriate of longitudinal
safety barrier along the road in every country. This is a semi- rigid barrier system
which can be used for the least to moderate deflection is acceptable likewise almost
1.2 meters (m) deflection [5]. The W-beam guardrail can be used on single shoulder
as well as a median barrier to separate the opposite flow of traffic where high
strength is required but inappropriate for rigid barrier due to limited adequate space.
18
This type of safety barrier can be classified into two (2) groups which are explaining
before. It has to stress that the W-beam guardrail is a relatively rigid object to be
impacted and relatively serious injury to the errant vehicle especially motorcyclists.
Hence it is utmost important that the design guidelines should be followed to
standards guardrail regulation.
Figure 2.7: W-beam Guardrail
2.5.3 Wire Rope Safety Barrier (WRSB)
This longitudinal safety barrier is capable of yielding to large deformation
which has the greatest dynamic deflection by utilizing the energy management
principle. It functions to guide the errant vehicle through forward rather than redirect
the vehicle into the traffic path with due to source of hazard to other motorist [5].
Thus, it keeps the vehicle to the minimum damage and reduces the risk of serious
injury to the motorist. The design of the post in between which combination with the
wire ropes is to prevent crossover of collide vehicle. WRSB with various designs
19
normally have four woven rope which is connected in between to the fixed posts
while the end of wire ropes is fixed into the ground [7]. Currently there are two (2)
types of wire rope safety barrier system used in Malaysia;
i. A wire rope system using double curved shaped posts
ii. A wire rope system using circular posts
Figure 2.8: Wire Rope System Using Double Curved Shaped Posts
2.6 Behavior under Impact
The W-beam guardrail is classified as a semi rigid. It's designed
inappropriately to withstand for higher impact angle [7, 12]. To achieve an optimum
function, the design of the guardrail should behave as follows[5]
20
a) The W-beam barrier must be strong enough to withstand the high
axial tensile and bending stresses that occur in the event of vehicle
impact.
b) The W-beam first bends and then flattens out forming a wide tension
band to contain the impacting vehicle.
c) The posts are initially restrained by passive pressure in the soil,
resulting in local failure of the soil at the ground line and for a short
distance below.
d) The steel posts partially rotate, with their point of rotation some
distance below the ground and also bend near the ground line.
A barrier should be able to dissipate the large amount of kinetic energy from
the impact of a moving vehicle. This is because; a moving vehicle has a kinetic
energy which is proportional to the square of the velocity. (KE= ½ MV2) [11].
Indeed, fastest the vehicle speed creates more kinetic energy that should be overcome
by the barrier.
2.7 Model Description
As the name suggests, W-beam guardrail is widely used in Malaysia
commonly consist of steel beam of ‘W’ shape design with smooth surface attached to
the packer or spacer combining with the post to support the beam. Normally, all
these combinations are fastened using bolts and nuts. In addition this particular
design usually made of galvanized steel which is good in impact performance even
though the higher containment level can be sustained by using concrete blocks [1].
21
2.7.1 W-beam
In this study, the W-beam guardrail meets the AASHTO M180 [13] design
specification. The standard design for this guardrail is about 312 wide with W shaped
profile with lengths of 3180 mm supported using C-channel section 150x76x6 mm
steel posts. These posts are 1810 mm length with 1100 mm rammed into the soil
which is two third of its length. Packer or a C- shaped block with dimensions of 360
x150 x6 mm is placed in between the post and the W-beam rail. The rail consists of
23 x 29 slotted holes for splice bolts and 19 x 64 slotted holes for post bolts. The W-
beam guardrail is designed to 2.67mm thickness. Viewed of the model are provided
in Figures 2.9, 2.10 and 2.11.
Figure 2.9: Section W-beam Profile [5]
22
Figure 2.10: Blocked-Out Steel W-Beam Guardrail [5]
2.7.2 Post Model
The steel post element is installed varying with depth. The depth of the post
element to be installed is about two third of its length [1]. However, the length of the
post element is also considered with the condition of the road environments. For
instance, on median guardrail, the length of the post element is longer than on
shoulder barrier. The aim is to make the median barrier more rigid as a result to
minimize deflection. The distance between posts can be equal to 1, 2 or 4 m depends
23
on the required containment level on the roads [1]. For instance, the guardrails were
located near hazardous such as drainage and slope, the length of the distance spacing
between two post elements is about two meter lengths. The function is to provide the
guardrail stiffest and capable to restraint the heavy vehicle and limiting deflection
impact. However, the shortest distance between posts will require more post element
and increase the costs which is one of the selection criteria need to be considered.
In real case, the installation of post is buried it with two third of its length into
the soil. There are several ways to model soil in the finite element software. One of
the examples is the “soil and crushable foam” model is used in the LS-DYNA [14].
The other way is model the soil by using the spring elements with Elosto-
Viscoplastic characteristic varying with depth [9]. Also, interaction between post and
soil foundation is simulated using spring elements together with frictional contact
[15]. However, in this research, the tie is used as a connection to position the post
into the floor to represent the interaction between the post and the ground.
Figure 2.11: W-beam Guardrail System
24
2.7.3 The Vehicle Model
The vehicle model of the bus in this study used the existing design model from
the previous study [16]. The finite elements (FE) vehicle model was constructed
using ABAQUS CAE tools and was designed with several parts which are chassis,
tire, floor, and body structure. All the parts were assembled and define the property
and required boundary condition. The body of the structure is designed using the
wire frame element (See Figure 2.12). The aim is illustrated as the bus vehicle model
and to reduce the time needed for analysis. More density of finite element mesh will
require a long time to analyze. However, the density mesh elements in the chassis
were increased to make the chassis more rigid and to improve contact behavior
between the vehicle and the barrier model [10].
The design test vehicle model for car is designed based on the Test 11 which
fulfills the EN 1317 standards regulations [10]. A rigid shell element structure is
designed in order to make simplification and the mass of the vehicle also adopted in
order to fulfill the weight regulation in the crashworthiness test [5].
Figure 2.12: A Complete Bus Model
25
Figure 2.13: A Complete Car Model
2.8 Computer Simulation Study
Borovinsˇek, et al [9] presented the results of computer simulation on
European standard En 1317 road safety barrier behavior under impact crash for high
containment level. The studies were running on a multiprocessor computer platform
in order to conduct a simulation using explicit finite element code LS-DYNA. There
are two different studies were conducted to satisfy the capable of computer
simulation under high containment level. Initial study was to determine the most
suitable reinforcement evaluated with different reinforcements of a chosen safety
barrier. Next, the results from the simulation were compared to the large scale
experiment of the same road safety barrier design to illustrate the correlation with.
Comparing the results showed a good relation between the computer simulation and
the experimental of the same road safety design. Indeed, the use of computational
simulation provided good benefits on reducing the cost of expensive full-scale crash
test.
Shen, et al [15] estimated the crashworthiness and optimize the design of the
guardrail system in term of relative vertical distance from the vehicle centroid to the
26
mounting height of W-beam. This study was used ABAQUS/Explicit v6.5 software
to simulate the dynamic response of the safety barrier under impacts. The simulation
was carried out with various heights of centroid of vehicle and the results obtained
that the design with 600mm vertical distance between the centroid of vehicle and
mounting height of W-beam showed the most effective in absorbing energy during
the crush process. From the present study, it is clear that the computer simulation of
the road barrier impact crash can be performed by using ABAQUS/Explicit tools.
In a paper of [12] the impact angle of 5, 10, 15, 20, and 25○ are the
appropriate values in order to simulate the crash barrier test. This is because,
vehicular crashes with angle more than 25○ are rarely happening in the road highway
and the most important thing is the road barrier systems is designed only for redirect
the run- off vehicle to the correct path. It is thought that, the crash with larger impact
angle produce higher absorption energy to the crash barrier. In addition, the most
vehicular velocities under impact crash are 50, 75, 100km/h. It might higher value
than this, but normally it is assumed that there has a possibility of the driver to apply
the brake when oppose to the hazardous situation.
A paper of [10] described the computational modeling of the safety barrier
design and its behavior under vehicle impact conditions according to EN 1317.
Which the full scale impact crash simulations were carried out by using LS-DYNA
code. The test is based on the TL-3 [17] which the barrier is simulate under vehicle
crash impact at 20○ and 100 km/h. In addition, simulation is compared to the full
scale experiment test and the results showed a very good agreement of barrier
deformation and car behavior. Hence, it is proved that, the numerical crash
simulation can be done in order to design the safety barrier systems.
27
Figure 2.14: Barrier Deformation Using Simulation and Experiment Test [10]
Furthermore, the review paper of Crash testing and evaluation of a low speed
W-beam guardrail systems, research were carried out a crash testing simulation of
the lower speed application since currently, the roadside safety features are designed
for high-speed applications [18]. For a rural roadway with low traffic volume and
low operating speed are expected much less severe than for the highway road
condition. Normally, the roadside safety barriers are designed as the same standards
as those intend to the higher impact condition. The cost saving may be affected if the
designing in the road safety features for the lower vehicle occupant as well as lower
operating speed. The test is carried out with a 820kg car impacting at 70km/h and at
an angle of 20○. The results indicate that the guardrail system performs satisfactorily
with the amount of deflection is not excessive and no yield occurs at the rail.
28
CHAPTER 3
METHODOLOGY
3.1 Introduction
This study is to carry out a numerical investigation of the road barrier impact
crash. The purposes of this study are to predict absorption energy and to investigate
the damage level of road barrier after impact crash. The analysis utilizes finite
element software which is widely used in many engineering courses. This is very
useful for problem with complicated geometries, loading, and material properties,
where analytical solutions are not available. Some general purpose finite element
software available in the market includes: ABAQUS, ALGOR, ANSYS, NASTRAN,
LS-DYNA and more.
The computational simulation test for road safety barrier impact crash
consists of the vehicle and the barrier models. The standard W-beam design of road
safety barrier was used in order to determine the effect of the structure after impact.
A model of bus and car was used to represent the vehicle model during the impact
simulation. The simulation was conducted as same as the full scale experiment test to
illustrate the correlation results between the simulation and the real test.
29
3.2 Finite Element Method (FEM)
The FEM, sometimes referred to a finite element analysis (FEA), is a
numerical method for solving lots of problems in engineering and mathematical
physics. The analyze depends on the physical problem including the physical
displacement, temperature, heat flux and fluid velocity [19]. The advantages of FEM
can be used to analyze problems involving:
a. Bodies with complex geometry
b. General loading condition
c. Different material properties
d. Various support condition
e. Variable element type and size
f. Easy modification-reanalyze
g. Dynamic- vibration, shock loading
h. Nonlinear problems
3.3 Tools required
Throughout this study, complete models for the impact crash test were
analyzed using ABAQUS v6.10. In general, there are three phases in any computer
aided engineering task: a) Pre-processing – to defining the finite element model and
environmental factor to be applied to it such as define a geometric property, element
types, constraints and loading to the model. b) Analysis Solver- solution of finite
element model which the software solves for deriving variables, such as reaction
forces, element stresses, and heat flow. c) Post-processing of results- used for
sorting, printing and plotting in evaluating the results using visualization tools. These
three phases were relating together as shown in Figure 3.1
30
Figure 3.1: A General Analysis Procedure for FEA
3.4 Development and Verification of an FE Model
During the course of this research, the development and verification of the
RSB FE model is the most important stage in studying impact crash using the FE
method. The more accurate results will be obtained with an accurate representation
of the RSB FE model to the real model. However, in this current practice, the
development of the model was simplified in a certain aspect in order to reduce the
modeling time as well as the simulation time due to the research time constraint.
Although this simplification may reduce the time in modeling and simulation, the
results obtained cannot give an accurate result but still in the range of predicted
results.
Initially, all the components are modeled using shell element and general
contact interaction is defined between each part for the entire model. Before
Post-processing
ABAQUS/CAE or ABAQUS Viewer
Output Files
job.odb, job.dat, job.res, job.fil
Analysis Solver
ABAQUS/Standard ABAQUS/Explicit
Input file:
Job.inp
Preprocessing
ABAQUS/CAE or other software
31
proceeding to further analysis, the verification of the RSB FE model was made to
determine the capability of general contact as well as the stability of the element in
ABAQUS/Explicit for crashworthiness applications. The developed FE model will
be verified at the assembly level which to determine the contact surface between the
components is like and actual assembly, also to ensure no intersecting between
component occur in that model. This will cause possible errors during performing an
analysis as well as will tend to reduce the results accuracy. The overall simulation
scheme is illustrated in Figure 3.2.
Figure 3.2: Overall Simulation Scheme
32
3.5 Construction of the W-beam Guardrail Model
The main parts of the W-beam guardrail components are modeled carefully
by following to the exact specification in order to represent as the actual model. The
shape and the characteristic of the W-beam are taken into consideration including the
post and packer or sometimes called a spacer.
In this research, two different tools are utilized in order to construct impact
crash models and to simulate the model for obtaining the results. At first, all the main
parts of the W-beam components is generated by using the third party software
namely SolidWorks 2010. The reason why is will easily to generate a model and
changing the parameter related to the model specification. Besides that, this software
also able to generate an input file .SAT that is compatible with ABAQUS v6.10
which then will be used to conduct a test by using Dynamic/Explicit for
crashworthiness simulation. However, instead of utilizing the third party software, all
the components can be modeled directly using the ABAQUS/CAE but might have
some limitations depend on the complexity of a certain model. Figure 3.3 showed all
the main components in the W-beam guardrail model.
33
Figure 3.3: Components Model in W-beam Guardrail
3.6 Parameter Selection
In this study, the model of the W-beam guardrail was design meets the
standard specifications of AASHTO by referring to the several guideline [5, 17]. The
aim is to represent an accurate model and achieve quality and consistency in
34
simulating data with show a relationship to the real model. In order to determine the
impact behavior on the safety barrier, the crashworthiness simulations were
performed considered to the parameter as shown in Tables 3.1, 3.2 and 3.3.
Table 3.1: Dimension of Vehicle Model
Parameter Bus Car Height (m) 3.9 1.42 Width (m) 2.45 1.83 Length (m) 12.5 4.66
Table 3.2: Parameter Descriptions
Variable
Parameter
Speed of Vehicle
70, 80, 110 (km/h)
Angle of Impact
5, 20, 25 (Degree)
Fixed Parameter
Different Moving Vehicle
• Bus • Car
W-beam Guardrail
Material, Thickness,
Length
Table 3.3: Material Selection [20]
Parts Material Young Modulus (GPa)
Density (kg/m3)
Poisson Ratio
W-beam Guardrail
Galvanized Steel 200 7860 0.33
3.7 Computer Simulation
The analysis of road barrier impact crash utilizes ABAQUS v6.10 software
running in Windows 7 Professional Service Pack 1 support by 2.40GHz Intel®
Core™2 Duo CPU with 3GB internal Random Access Memory (RAM)
35
Full scale finite element crashworthiness simulations are performed for two
different vehicles, which test 1-4 is for car and test 5 is for the bus. The vehicle, a
1500-kg model is used to represent a car and a 13000-kg model [16] is used to
represent as a bus respectively. The purposed is to test the performance of the barrier
with both car and bus at the certain speed and angle. The top of the rail is located
710mm above the ground with 4m spacing between the posts along the rail. Only two
continuous W-beams are used in this study to represent as the longitudinal rail.
In order to simulate the dynamic response behavior of the W-beam barrier,
analysis is conducted by using Dynamic/Explicit for crashworthiness simulations.
Crash scenario with different vehicles used the finite element analysis to extract the
results in determining the amount of energy absorption that can be absorbed by the
crash barrier. Also, it can be used to illustrate the damage level behavior of the safety
barrier under impact crash.
In order to carry out an FEA analysis using computer simulation, the models
are simulated by following the step as shown in Figure 3.4.
36
Figure 3.4: Flow of Simulation Step
3.7.1 Part Geometries
The main part of the road barrier impact rash simulation consists of several
components namely W-beam, Post, Packer, Car, Bus, and Floor. All distinct
components have been generated to represent a full scale crash test using finite
element software.
Parts Sketch or Importing CAD model
Property Assigning Material Properties
Assembly Integration of the Parts
Step selecting types of analysis
Interaction Identify and Assigning Contact Properties
Load Assigning Load and Boundary Condition
Mesh selecting and Assigning Seeds and Element types
Job Creating, Checking and Submitting Job
Visualization Extracting Results
37
Every part of the W-beam guardrail is firstly modeled by using third party
software namely SolidWorks 2010. Then, input file .SAT which compatible to the
commercial ABAQUS software is created in order to generate the model in the
ABAQUS/CAE tool. The model is designed carefully based on the dimension
specified in Figure 2.9.
The vehicle model of the car is modeled directly in ABAQUS/CAE with 3D-
discrete rigid shell element by following the standard car dimension. Similarly, a
structure of the bus is generated using ABAQUS/CAE tool and is designed with
consists of several parts such as chassis, tire, residual space and body structure. The
body structure of the bus is modeled using the wire frame element. While the tire,
chassis and residual space are designed by using the shell element. However, in this
research, the model of the bus is used based on the existing design model from the
previous study. Lastly, the floor is modeled to represent as the road surface and it is
designed by using the shell element. (See Figures 3.5 and 3.6)
Figure 3.5: Components of Car Impact Crash Model
38
Figure 3.6: Components of Bus Impact Model
3.7.2 Material Properties
After having imported or generate all the parts, it is required to define the
material for all components that want to analyze except the components that have
been generated as discrete rigid. For the components of W-beam guardrail, the
material property of Galvanized Steel is defined according to the Table 3.3. A
homogeneous shell section named Beam is created with thickness 2.67mm and it is
assigned to the W-beam. Afterwards, the homogeneous shell section named Post and
Packer is created with thickness 6mm are assigned to the both packers and post
respectively. All these components are assigned to the material of Galvanized Steel.
3.7.3 Part Assemblies
Once all the parts have been assigned to its respected properties, the instance
parts are then being imported into the assembly module to assemble the parts
according to the Figures 3.5 and 3.6. All the parts are imported as the dependent type
Residual Space
Tire
Bus Structure
Chassis
39
in order to easily mesh the original parts. This is because dependent parts will shares
the geometry and the mesh of the original parts [21]. As a result, it can provide fewer
memories and reduce the simulation time.
The model of the guardrail system was assembled using the two commands
which are TRANSLATE and ROTATE. The W-beam rail parts were attached
through the offset packer to the posts. The post is assembled to the floor and beam
with spacing between posts is 4m which is consists of three posts in the system.
While the vehicles part is translate above the floor.
3.7.4 Step and Output Definitions
The analysis is about to investigate the impact behavior of the road barrier
under impact crash. Consequently, a single Dynamic, Explicit procedure named as
Step-1 is created in the time period of 0.10s. Stresses, strains, displacement, velocity,
acceleration, force, and contact are requested in the field output while the energy is
requested for the results history output. All the output request for the whole model at
every 0.001 units of time. Field output is basically using the Visualization module to
view field output data using deformed shape, contour, or symbol plots. While the
history output used the Visualization module to display history output using X–Y
plots [21].
3.7.5 Contact Interaction
In this analysis, a General Contact/Explicit is used for the contact interaction
which the ABAQUS will automatically define contact between all regions of the
model with a single contact interaction. This typically used for all exterior surfaces
of the parts and make a simple way in defining the contact interaction for the whole
40
model. Normal behavior with hard surface contact and also tangential behavior with
friction coefficient was set to 0.1 in the contact property.
3.7.6 Constraints
In the crashworthiness simulations, there might have several components
need to be have assigned a constraint in order to ensure the model is similar to the
real cases. The purposed is to constrain the degree of freedom of some interaction
during the analysis. In this research, one of the types of constraint is a tie constraint
which some of the parts required to be tied. This can be represented as the bolted or
welded. The red color represents the combined surface which gives more influence to
the part that wants to attach to it and the purple color represent the slave surface. This
kind of constraint can be illustrated in Table 3.4.
Table 3.4: Description of Tie Constraint
Name of Constraint Types of Constraint
Tie Beam and Packer Master surface : Packer
Slave surface : W-beam
41
Tie Packer and Post Master surface : Post
Slave surface : Packer
Tie Post and Floor Master surface : Floor
Slave surface : Post
Tie Between W-beam Master surface : W-beam
Slave surface : W-beam
42
3.7.7 Load and Boundary Conditions
In the step-1 procedure, the load that has been created is a gravitational load
for the whole model and is assumed to be 9.81ms-2 to represent as a gravitational
force from the ground. Afterwards, the reference point of rigid floor and every single
of post at the bottom region have been requesting for constraint in all directions by
prescribing ENCASTRE which means all the translation and rotation is definitely
equal to zero. This is because, in the real cases, the post is actually rammed into the
soil. So that, by doing this it can represent as soil but did not give an appropriate
result compare to the soil element.
The vehicle's initial velocity of 70km/h (19.44m/s), 80km/h (22.22m/s), and
110km/h (30.56m/s) have been defined in the predefined field tool in order to
simulate the crash test at that particular speed. These all value is created at the initial
step and computed to the step-1 analysis procedure. A point mass of 1500-kg and
13000-kg is created for the inertia to represented as the impact load in the both car
and bus respectively.
3.7.8 Mesh Properties
In order to generate the mesh to every single part, the mesh characteristics of
the parts are firstly defined such as mesh density, element shape and the element type
in the mesh control tool. Reduce integration element method with linear geometric
order is used in generating the mesh properties for every part. Then, a global size
seed is defined according to the appropriate number of nodes and elements before the
mesh is generated. All the detail of the final mesh characteristic is illustrated in Table
3.5.
43
Table 3.5: Detail of Mesh Components
COMPONENTS TYPES OF ELEMENT
NO. OF ELEMENTS
NO. OF NODES
Car S3 S4R 515 547
Bus B31 S3 3630 1903
W-beam S3R S4R 6561 6778
Post S3R S4R
624 679
Packer S3R S4R 371 407
Floor R3D4 100 121
44
3.7.9 Job Analysis
This is the last part in configure the analysis where the job is created to
submit the analysis and monitor its progress. A full analysis is selected for the job
type and the number of multiple processors is set in the parallelization tabled based
on the computer processor. Afterwards, select the Double- analysis + packager for
the ABAQUS/Explicit precision and single nodal output precision is selected in the
precision tabled.
After completing in creating the job, data check is performed in order to
determine any possible error and continue to submit the job analysis once the data
check is completed. The input file has been written and a full analysis is running for
the analysis. Then, the results of the completed analysis can be obtained by using the
ABAQUS/CAE under visualization module or can be directly open using the
ABAQUS/Viewer.
3.8 Preliminary Test
Throughout this research, a preliminary test is conducted in order to ensure
that the crashworthiness scenario is performed as predicted. Besides that, the tested is
to check whether the constraints and the boundary conditions that have been set
before are correct and the model can run successfully without error. There are several
tested that have been done as described in the Table 3.6.
45
Table 3.6: Description of Preliminary Tests
TRY 1
• The test is conducted in order to check whether the constraints
and the boundary conditions that have been set before are correct or not.
• Angle of impact: 30○ • Velocity: 70km/h • Mass: 1500kg
TRY2
.
• The test is conducted to determine the contact interaction between the rigid bus and the wall during impact crash
• Angle of impact: 30○ • Velocity: 70km/h • Mass: 13000kg
46
3.9 Actual Tests
The actual crashworthiness simulations are conducted by preparing the model
as follows the simulation parameters as shown in the Table 3.7.
Table 3.7: Simulation Test Parameters
TEST VEHICLE TYPE
VEHICLE MASS
(kg)
IMPACT ANGLE
(○)
IMPACT VELOCITY
(km/h) T1 CAR 1500 5 80 T2 CAR 1500 20 80 T3 CAR 1500 20 110 T4 CAR 1500 25 80 T5 BUS 13000 20 70
47
3.9.1 Car Impact Crash
Table 3.8 showed the description of the actual car test which related to the
Table 3.7.
Table 3.8: Description of Actual Car Tests
• T1 W-beam guardrail impacted with initial velocity 80km/h at a 5○ impact angle
• T2 W-beam guardrail impacted with initial velocity 80km/h at 20○ impact angle
48
• T3
W-beam guardrail impacted with initial velocity 110km/h at 20○ impact angle
• T4 W-beam guardrail impacted with initial velocity 80km/h at 25○ impact angle
49
3.9.2 Bus Impact Crash
Table 3.9 shows the description of the actual bus test which related to the Table 3.7.
Table 3.9: Description of Actual Bus Test
• T5 W-beam guardrail impacted with initial velocity 70km/h at 20○ impact angle
50
CHAPTER 4
RESULTS AND DISCUSSION
4.1 Introduction
This chapter presents the result value based on the computational simulation
of impact crash using finite element software. In this research, four types of analysis
have been conducted such as preliminary test, impact test under different speed,
impact test under different angle and impact test under different vehicle. The results
of the simulation test are evaluated based on the amount of the absorbed energy and
also the damage level of the roadside barrier. In this research, the simulation analysis
that was conducted by Shen, et al [15] was utilized to verify the outcomes from this
simulation.
4.2 Preliminary Test
It is essential to conduct a preliminary test in order to determine whether the
simulation of the crash test can be done or not. The results of the test showed that
model meets the criteria and able to proceed for the actual test. The description of the
test is shown in Table 4.1.
51
Table 4.1: Description of the Preliminary Tests
TRY 1
• At initial, the job analysis is aborted due to an error • By checking the error in the status file. There have some distorted
element occur in the assembly. This can be done by adjusting the mesh density.
• The results showed that the barrier deform according to the real crash behavior.
TRY 2
.
52
• The first stage of trial, a model of bus have a contact interaction between the structure and the wall. However, after hitting the wall, the bus tends to roll over and penetrate the floor.
• The contact interaction needs to be recheck and proceed with the second trial by adding the plastic property to the wall.
• In this trial, the bus showed a good contact between the walls and also with the floor.
• Once the bus hit the wall, it showed that the bus step over and penetrate the wall. This is due to the shell wall is too thin and lower material properties as assigned in initial.
• The whole model is valid to use and the model of the wall is replaced with the model barrier for the actual test.
4.3 Full Simulation Results
The actual test is conducted based on the European EN 1317 standard which
the vehicle was prescribed to have the initial velocity of 80km/h at an impact angle
of 20○ with 1500kg mass respectively. Then, the test is conducted with the same
mass and various velocities at an impact angle of 5, 20 and 25○. Also, a numerical
simulation of bus impact on guardrail system was then carried out with a 13000kg
mass and initial velocity 70km/h at 20○ angle for W-beam guardrail system. The
overall behaviors of the crash scenario such as the deflected shapes of the guardrail
and the position of the car or bus at different impact conditions are given in Figure
4.1.
53
a) 80km/h at 5○ b) 80km/h at 20○
54
c) 110km/h at 20○ d) 80km/h at 25○
55
e) 70km/h at 20○
Figure 4.1: Computational Simulations of Vehicle Impact Crash
56
Results in Figure 4.1 illustrate the computational simulations of vehicle
impact crash at certain conditions. The crash behavior of W-beam guardrail which
impacted with 110km/h vehicular speed at 20○ impact angle is employed for detail
explanation. At initial, the car position standing start with zero acceleration and no
deformations occur at the barrier since there have no contact interaction between the
car and the beam. Then at time step 0.02s, the car starts to hit the barrier with an
initial velocity of 30.56m/s. It is shown that, there have deformations occur on the
barrier with the deflection at the point of impact. This means that the barrier capable
to deflect upon impact.
Afterwards, the cars continue moving within its direction and hit the barrier
accordingly and tearing (see Figure 4.2) occurs at the post of the barrier where both
two posts which the location is behind to the point of impact capable to pulling while
the post which at the front have been push by the beam. At higher speeds, the
guardrail deforms locally and causes the local posts to yield [12] due to the
connection interaction between the beam and the post which in response of impact.
Figure 4.2: Tearing and Twisting at the Guardrail Post
Furthermore, at time step of 0.08s, the car tends to move towards the barrier
and the post continues experience to tear and twist. In real behavior, the barrier
would tend to redirect back the collide vehicle to the right path guided by the barrier.
However, the results showed that, the car tends to move towards the barrier and does
57
not redirect back. There might have some possibilities that cause of this problem. For
instance, in this simulation there have only two continuous guardrail were assembled.
So that, the barrier will absorb the high impact energy and dissipated the energy
through deformation. Secondly, in this model, rigid car is assumed which restricted
to any deformation. Hence, high energy is fully transferred to the barrier through its
deformation. Besides that, the post attributes less torsional rigidity and cause the
barrier experienced with high deformation. Also, the point mass of inertia is not
located at the true center of gravity of the vehicle and finally cause the possibilities
of the car tend to yaw at the point of rotation.
Then, at the final step of 0.1s the crash behavior showed that the larger
deflection occurs at a higher impact velocity compared to the other. This is because,
at high vehicle speed, the kinetic energy is higher. As a result, the barriers need to
withstand the errant vehicle by dissipating much energy through deformation of its
system. Large impact energy also happens at large impact angle. The high
deformations also resulted from the larger impact of area between the car and the
beam.
By looking the simulation results as illustrated in Figure 4.1, it shows that
only two cases T1 and T5 meets the NCHRP report 350 where the guardrail
effectively contain and capable to redirect the errant vehicle. The other results in T2,
T3, and T4 also capable contain the errant vehicle but cannot effectively redirect the
errant vehicle and cause the vehicle to experienced rotation while hitting the barrier.
For the simulation in T1, the barrier is impacted with a car at a smaller impact angle
compared to the simulations in T2, T3, and T4. Hence, the barrier capable to
effectively redirect the errant vehicle while hitting the barrier. The same behavior
also presents in T5 where a bus with 13000kg mass is redirected effectively by the
barrier although the impact angle is similar to the simulations in T2 and T3. This is
because, the point mass of inertia is not defined correctly in the center of gravity of
the car so that with higher speed, the car hit the barrier and tend to rotate without
redirect back to the correct path. It might the major problem that implements the car
to rotate and failed to redirect back to the correct path.
58
4.3.1 Damage Level
Basically, there are two different methods that have been implemented in this
analysis in order to investigate the damage level of road safety barrier under impact
crash. Firstly, the region of the stress which exceeds the ultimate stress value has
been removed in order to show the damage level of the structure. Hence, the region
with high damage level can be determined. Secondly, the damage level of the barrier
under impact crash is determined by comparing to the maximum deflection value
provided by the standard (see Figure 2.10). 1.2m is benchmark value to determine
whether the deflection of the barrier under various impact conditions exceeds the
maximum value or not. Hence the maximum deflection of the RSB also can be
determined. The results of the damage level can be illustrated in Figure 4.3 and 4.4.
a) Deformation under impact with initial velocity 80km/h at 5○ angle.
b) Deformation under impact with initial velocity 80km/h at 20○ angle.
59
c) Deformation under impact with initial velocity 110km/h at 20○ angle
d) Deformation under impact with initial velocity 80km/h at 25○ angle
e) Deformation under impact with initial velocity 70km/h at 20○ angle
Figure 4.3: Damage Level at 550Mpa
Figure 4.3 illustrated the damage level of the RSB under impact crash at the
step time 0.1s. The element of the barrier that experience higher stress which exceeds
the ultimate stress have been remove in order to indicate the region of the higher
stress also to determine whether the barrier will break or not. By comparison to the
all conditions, it showed that the barrier which experienced higher impact velocity
have a higher damage level comparable to the barrier which experienced lower
impact speed as showed in Figure 4.3 (c). All conditions indicated the high stress
occur at the point of the impact and propagate to its region. However, the barrier
60
does not tend to break way since the force is distributed along the beam and cause
the post to experienced twist and minimize the stress concentration at the point.
Figure 4.4: Displacements of W-beam Guardrail under Impact Crash
Figure 4.4 showed the deflection of the barrier under impact crash in U3
direction which perpendicular direction to the W-beam rail. By comparing the
maximum deflection value to the standards, the barrier still in the acceptable range of
deflection which small to moderate deformation. The maximum deflection that
provided by the standard is approximately 1.2m. The results obtained that, the
maximum deflection of the barrier under impact angle of 20○ with initial velocity
110km/h which prescribe in test three (T3) is about 1.2m followed by the 1.08, 1.04,
0.032 and 0.006m of maximum deflection values corresponding to T2, T4, T5 and
T1 respectively. The force of the impact is distributed by the beam to the post in
order to minimize the deflection. However, the barrier with higher impact angle also
has the higher deflection similar to the higher stress. This is because, at higher speed
and larger impact angle, the barrier will deflect upon impact by absorbing the energy
through the deformation and distribute the force localizing near the post. It also
resulted from the large impact area of the car.
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
1.00E+00
1.20E+00
U3
Dis
plac
emen
t (m
)
Test
Maximum W-beam Displacement
T1
T2
T3
T4
T5
61
4.3.2 Energy Absorption
Energy absorbing properties have been compared for different impact
condition. Also, energy absorption is determined to which portions of energy
dissipated to other kind of energy. Overall simulation results from the previous study
conducted by Shen et al (2008) are utilized for comparison with result obtained.
Numerical results were given below.
a) Comparison of Kinetic Energy Variation of the Whole Model
b) Comparison of Internal Energy of Guardrail System
62
c) Comparison of Plastic Dissipation Energy of the Whole Model
d) Comparison of Frictional Dissipation Energy of the Whole Model
e) Comparison of Viscous Dissipation Energy of the Whole Model
Figure 4.5: Correlation between the simulation results (left) and previous
study (right) [15]
63
By comparing to the previous study, it is found that, the trend for all
particular energy is almost similar to current results. Although the time simulation
for the previous study and this research is quite different, the characteristic of the
simulation parameter is almost similar. Hence, both results present the same trend
line for all particular energy. Nevertheless, the value of energy obtained is slightly
different for certain types of energy. In other words, the difference in the value might
probably arise from different model set up. For instance, the model of the post was
developed using cylindrical shapes (see Figure 4.6) and also distance post spacing
between the two end posts was prescribed to 2m while the distance between two
central posts was prescribed to 4m [15]. This one example might be a good
reasonable to show the differences in the certain value.
Afterwards, kinetic energy presents the energy of motion and it is dependent
on mass and the velocity of an object. Therefore, by changing the value of mass and
velocity, the kinetic energy also change simultaneously. The initial value of the
kinetic energy produced by 30.56m/s vehicular speed and 1500kg mass for the whole
model in T3 is approximately around 700kJ. It is shown that, the kinetic energy in T5
has higher kinetic energy among the others. This is because, high speed as well as
larger mass produces higher kinetic energy.
Figure 4.6: Numerical Analysis of Crash Impact Model of Previous Study [15]
64
The internal energy of the guardrail systems displays the capability of the
barrier to absorb energy from the impact vehicle. At initial, the internal energy of the
barrier is zero and will increase simultaneously as the kinetic energy decreases. This
is because the kinetic energy of the moving vehicle is transferred to the barrier
through deformation when experienced impact crash. The graph in Figure 4.4 (b)
also showed that as much 86.12kJ of absorption energy is transferred through
deformation of the guardrail in T3.
Results in Figure 4.5 (c) indicate the plastic dissipation energy of the whole
model. This kind of energy is also part of the internal energy which represents the
amount of energy dissipated through deformation of the guardrail systems. Initially,
energy is zero since there have no deformation occur but increasing linearly until the
end of impact. This showed that, energy is absorbed through the deformation of the
beam when impacted by a moving vehicle. The results obtained showed that, high
energy is absorbed at high impact velocity and larger impact angle. Approximately,
79.79kJ energy is absorbed through the plastic deformation. Initially, the kinetic
energy of the car is about 700kJ and the kinetic energy which transfer to the beam is
approximately 101.93kJ. Hence, the total percentage of absorption energy is about
78percent which more than half energy is transferred through the deformation of the
beam.
Next, vehicle-barrier friction also resulted to be a significant source of energy
dissipation. Theoretically, frictional forces are calculated as the product of normal
force from vehicle to guardrail and a dynamic frictional coefficient [12]. By
comparing the results in T1, T2, T3 and T4 which present car as the vehicle impact,
it is found that, lower impact velocity generates a lower amount of frictional energy
dissipation. Conversely, the results in T5 produce higher frictional dissipation energy
compare to others. This is because, bus have higher mass as a result, exerted higher
force from the vehicle to the barrier and increasing the frictional losses.
Overall resulted in Figure.4.5 (a) to (e), it is found that the barrier can absorb
higher energy through deformation which 84.49percent of kinetic energy is
dissipated through the guardrail deformations followed by frictional dissipation
65
energy 13.18percent and viscous dissipation energy 0.33percent. The other 2percent
is probably converted to the other kind of energy such as strain energy as well as
artificial strain energy. This value is based on the simulation in test T3 Hence the
requirement of the road barrier systems to absorb as much high kinetic energy meets
the standard. As a result, the severity of accidental injury for the vehicle occupants
can be reduces.
66
CHAPTER 5
CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion
Road barriers are highway features designed primarily to give a protection to
the vehicles from the roadside hazards. There are few types of road barriers currently
widely use along the longitudinal highway. One of them is a W-beam guardrail. Over
the years, many researchers have been involved in the design and development of the
road safety barriers. Therefore, standards for safety barriers also evolved in response
to changing technology and changes in the automotive product characteristics. As a
consequence, many existing safety barriers need to be studied to comply with the
latest design standard which provided by the road and safety organization.
The main objective of this research is to investigate the damage level of the
road barrier under impact crash which to know whether the barriers will fail or not
after impact and to determine the maximum deflection of the barrier. The studied
also examined the amount of energy absorption that can be absorbed by the guardrail
system under impact crash. Hence, improvement can be applied in the future to the
present guardrail and will reduce the severity of injury to vehicle occupants upon
impact in road accidents involving crash barriers.
67
Upon conducting this research, extensive studies have been made to
understand the characteristics of the impact collision such as the point of impact to
the guardrail, impact velocity and also the outcomes that need to be evaluated. To
specify the study, the focus of the investigation was narrowed to several
characteristics. Firstly, the study utilized car and bus as the vehicle impact. It is
found that, the bus has higher kinetic energy than car due to higher mass. Therefore
higher kinetic energy can be transferred to the W-beam guardrail during collision.
Moreover, one of the energy absorption devices currently widely used along the
highway is a W-beam guardrail. Consequently, the study utilized W-beam guardrail
as the crash barrier in crashworthiness scenario. It is also found that, the current
design of the guardrail is acceptable which can absorb higher energy and
consequently reduce the deceleration and thus increase the safety of vehicle
occupants.
Dynamic/Explicit analysis was employed for evaluation of the W-beam
guardrail behaviors under vehicle impact crash. The simulations of the road barrier
impact crash have been done using ABAQUS/Explicit v6.10. It shows that the
barrier capable to deflect upon impact. The barrier will absorb the energy resulted
from the impact of vehicular speed of 110m/h at an angle of 20○ but not very
efficient. The barrier failed to redirect the vehicle back to the roadway. However, the
amount of absorption energy can be predicted. At time 0.1s, the resulted obtained
that the barrier will absorb high energy at high impact angle through permanent
deflections of the guardrail system. Similarly, the behavior of the barrier at high
impact angle produces a high damage level to the barrier. Although the time step is
lower, the energy absorption and the damage level can be determined.
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5.2 Future Work
In order to improve the outcome of this research, several recommendations
can be implemented for the future work. Some of the suggestions for future work are:
1. Model the barrier with solid parts to get more accurate results
2. Simulate with large scale of step time to look the behavior after impact
3. Use a non-rigid structure of the vehicle to get the more accurate crash
behavior so that, the true energy transfer to the beam can be determined. It is
thought that, energy is transferred through deformation of the beam and the
car.
4. Simulate with soil model interaction between the post and the ground. This is
because; energy is also transferred to the post and dissipated through the
deflection of the soil varying with depth.
5. Also, model the barrier with the spring element at the both ends to represent
the continuous rail.
6. Simulate the crash test using software that design mainly for crash test such
as MADYMO and LS-DYNA code.
69
LIST OF REFERENCES
1. Ren, Z. and M. Vesenjak, Computational and experimental crash analysis of
the road safety barrier. Engineering Failure Analysis, 2005. 12(6): p. 963-
973.
2. MIROS. General Road Accident Data in Malaysia (1995 – 2010). [Cited
2011 20/11/2011]; Available from:
http://www.miros.gov.my/web/guest/road.
3. PDRM, Perangkaan Kemalangan Jalan Raya Bagi Tahun 2002-20119JAN-
MEI). 2011, PDRM.
4. JKJR. Statistics of Accidents, Injuries and Death in 2011. [Cited 2011;
Available from:
http://www.jkjr.gov.my/webv2/index.php/en/component/content/article/1007-
laman-blog-jkjr.
5. REAM, Guidelines on Design and Selection of Longitudinal Traffic Safety
Barrier. 2006: Road Engineering Association of Malaysia
6. UTTIPEC, Guideline and Design Specifications for Crash Barriers,
Pedestrian Railings and Dividers. 2010, Unified Traffic and Transportation
Infrastructure (PLG & ENGG) Centre: New Delhi.
7. Chantel Duncan, B.C., Niklas Truedsson and Claes Tingvall, Motorcycle and
safety barrier Crash Testing: Feasibility Study. 2000: p. 61.
8. Guido Bonin, G.C.a.G.L., Computational 3D Models of Vehicles Crash on
Road Safety Systems, in 8th International Symposium on Heavy Vehicle
Weights and Dimensions Loads, Roads and the Information Highway’. 2004,
Document Transformation Technologies: Johannesburg, South Africa.
9. Borovinšek, M., et al., Simulation of crash tests for high containment levels of
road safety barriers. Engineering Failure Analysis, 2007. 14(8): p. 1711-
1718.
70
10. Matej Vesenjak, M.B., Zoran Ren, Computational simulations of road safety
barriers using LS-DYNA. 2007: p. 11-17.
11. Kelkar, R.G.a.A.D., Nonlinear Crash Dynamics Simulation of Novel Airbag
Based Next Generation Energy Absorbing Barrier. 2006.
12. Brian A. Coon, M.A., John D. Reid, Crash Reconstuction Technique for
Longitudinal Barriers. Transportation Engineering © ASCE, 2005.
13. AASHTO, Standard Specifications for Transportation Materials and
Methods of Sampling and Testing, in Guardrail and Fencing. 2010, American
Association of State Highway and Transportation Officials: Washington, DC.
14. Dhafer Marzougui, P.M.a.S.K., Evaluation of Rail Height Effects on the
Safety Performance of W-Beam Barriers. 2007. p. 50.
15. Xinpu Shen, L.G., Lu Yang, Xianhe Du and Peng Cao, Numerical analysis of
impact effect on mechanical behavior of strong guardrail system. Conference
Series 96, 2008.
16. Othman, M.S.A.B., Rollover Test Simulation of Double Decker Bus in
According to UNECE Regulation 66 Imposed the Malaysian Government, in
Manufacturing. 2011, University Teknologi Malaysia: Skudai.
17. H. E. Ross, J., D. L. Sicking, and R. A. Zimmer, J. D. Michie, Recommended
Procedures for the Safety Performance Evaluation of Highway Features, in
National Cooperative Highway Research Program Report 350. 1993,
Transportation Research Board National Research Council.
18. King K. Mak, R.P.B., D. Lance Bullard, Jr., Crash Testing and Evaluation of
a Low Speed W-beam Guardrail System. 1993.
19. Hutton, D.V., Fundamentals of Finite Element Analysis. 2005: McGraw-Hill.
20. Wekezer, O.S.M.a.J.W., Crash Impact Analysis of the G2 Guardrail: A
Validation Study. TRB National Research Council, 1998.
21. Abaqus/CAE User's Manual. 2010; Available from:
https://www.sharcnet.ca/Software/Abaqus610/Documentation/docs/v6.10/boo
ks/usi/default.htm.
