Abstract: For several hundred years, the design of railway tracks
has practically remained unchanged. Traditionally, rail tracks are
placed on a ballast layer due to several reasons, including economy,
rapid drainage, and high load bearing capacity. The primary function
of ballast is to distributing dynamic track loads to sub-ballast and
subgrade layers, while also providing lateral resistance and allowing
for rapid drainage. Upon repeated trainloads, the ballast becomes
fouled due to ballast degradation and the intrusion of fines which
adversely affects the strength and deformation behaviour of ballast.
This paper presents the use of three-dimensional discrete element
method (DEM) in studying the shear behaviour of the fouled ballast
subjected to direct shear loading. Irregularly shaped particles of
ballast were modelled by grouping many spherical balls together in
appropriate sizes to simulate representative ballast aggregates. Fouled
ballast was modelled by injecting a specified number of miniature
spherical particles into the void spaces. The DEM simulation
highlights that the peak shear stress of the ballast assembly decreases
and the dilation of fouled ballast increases with an increase level of
fouling. Additionally, the distributions of contact force chain and
particle displacement vectors were captured during shearing progress,
explaining the formation of shear band and the evolutions of
volumetric change of fouled ballast.
Abstract: The early-stage damage detection in offshore
structures requires continuous structural health monitoring and for the
large area the position of sensors will also plays an important role in
the efficient damage detection. Determining the dynamic behavior of
offshore structures requires dense deployment of sensors. The wired
Structural Health Monitoring (SHM) systems are highly expensive
and always needs larger installation space to deploy. Wireless sensor
networks can enhance the SHM system by deployment of scalable
sensor network, which consumes lesser space. This paper presents the
results of wireless sensor network based Structural Health Monitoring
method applied to a scaled experimental model of offshore structure
that underwent wave loading. This method determines the
serviceability of the offshore structure which is subjected to various
environment loads. Wired and wireless sensors were installed in the
model and the response of the scaled BLSRP model under wave
loading was recorded. The wireless system discussed in this study is
the Raspberry pi board with Arm V6 processor which is programmed
to transmit the data acquired by the sensor to the server using Wi-Fi
adapter, the data is then hosted in the webpage. The data acquired
from the wireless and wired SHM systems were compared and the
design of the wireless system is verified.
Abstract: One of the main purposes of designing bucklingrestrained
braces is the fact that the entire lateral load is wasted by
the braces, the entire gravitational load is moved to the foundation
through the beams, and the columns can be moved to the foundation.
In other words, braces are designed for bearing lateral load. In the
implementation of the structure, it should be noted that the
implementation of various parts of the structure must be conducted in
such a way that the buckling-restrained braces would not bear the
gravitational load. Moreover, this type of brace has been investigated
under impact loading, and the design goals of designing method
(direct motion) are controlled under impact loading. The results of
dynamic analysis are shown as the relocation charts of the floors and
switch between the floors. Finally, the results are compared with each
other.
Abstract: Steel extended end plate bolted connections are
recommended to be widely utilized in special moment-resisting frame
subjected to monotonic loading. Improper design of steel beam to
column connection can lead to the collapse and fatality of structures.
Therefore comprehensive research studies of beam to column
connection design should be carried out. Also the performance and
effect of corrugated on the strength of beam column end plate
connection up to failure under monotonic loading in horizontal
direction is presented in this paper. The non-linear elastic–plastic
behavior has been considered through a finite element analysis using
the multi-purpose software package LUSAS. The effect of vertically
and horizontally types of corrugated web was also investigated.
Abstract: The purposes of hydraulic gate are to maintain the
functions of storing and draining water. It bears long-term hydraulic
pressure and earthquake force and is very important for reservoir and
waterpower plant. The high tensile strength of steel plate is used as
constructional material of hydraulic gate. The cracks and rusts,
induced by the defects of material, bad construction and seismic
excitation and under water respectively, thus, the mechanics
phenomena of gate with crack are probing into the cause of stress
concentration, induced high crack increase rate, affect the safety and
usage of hydroelectric power plant. Stress distribution analysis is a
very important and essential surveying technique to analyze
bi-material and singular point problems. The finite difference
infinitely small element method has been demonstrated, suitable for
analyzing the buckling phenomena of welding seam and steel plate
with crack. Especially, this method can easily analyze the singularity
of kink crack. Nevertheless, the construction form and deformation
shape of some gates are three-dimensional system. Therefore, the
three-dimensional Digital Image Correlation (DIC) has been
developed and applied to analyze the strain variation of steel plate with
crack at weld joint. The proposed Digital image correlation (DIC)
technique is an only non-contact method for measuring the variation of
test object. According to rapid development of digital camera, the cost
of this digital image correlation technique has been reduced.
Otherwise, this DIC method provides with the advantages of widely
practical application of indoor test and field test without the restriction
on the size of test object. Thus, the research purpose of this research is
to develop and apply this technique to monitor mechanics crack
variations of weld steel hydraulic gate and its conformation under
action of loading. The imagines can be picked from real time
monitoring process to analyze the strain change of each loading stage.
The proposed 3-Dimensional digital image correlation method,
developed in the study, is applied to analyze the post-buckling
phenomenon and buckling tendency of welded steel plate with crack.
Then, the stress intensity of 3-dimensional analysis of different
materials and enhanced materials in steel plate has been analyzed in
this paper. The test results show that this proposed three-dimensional
DIC method can precisely detect the crack variation of welded steel
plate under different loading stages. Especially, this proposed DIC
method can detect and identify the crack position and the other flaws
of the welded steel plate that the traditional test methods hardly detect
these kind phenomena. Therefore, this proposed three-dimensional
DIC method can apply to observe the mechanics phenomena of
composite materials subjected to loading and operating.
Abstract: The paper aims at investigating the effect of number
of story on different structural components of reinforced concrete
building due to gravity and lateral loading. For the study, three
building models having same building plan of three, six and nine
stories are analyzed and designed using software package. All the
buildings are residential and are located in Dhaka city of Bangladesh.
Lateral load including wind and earthquake loading are applied to the
building along both longitudinal and transverse direction as per
Bangladesh National Building Code (BNBC, 2006). Equivalent static
force method is followed for the applied seismic loading. The present
study investigates as well as compares mainly total steel requirement
in different structural components for those buildings. It has been
found that total longitudinal steel requirement for beams at each floor
is 48.57% for three storied building, 61.36% for six storied building
when the total percentage is taken as 100% in case of nine storied
building. For an exterior column, the steel ratio is 2.1%, 3.06%,
4.55% for three, six and nine storied building respectively for the first
three floors. In addition, it has been noted that total weight of
longitudinal reinforcement of an interior column is 14.02 % for threestoried
building and 43.12% for six storied building when the total
reinforcement is considered 100% for nine storied building for the
first three floors.
Abstract: The current study aims to highlight the loading
characteristics impact on the time evolution (focusing particularly on
long term effects) of the deformation of realized reinforced concrete
beams. Namely the tension stiffening code provisions (i.e. within
Eurocode 2) are reviewed with a clear intention to reassess their
operational value and predicting capacity. In what follows the
experimental programme adopted along with some preliminary
findings and numerical modeling attempts are presented. For a range of long slender reinforced concrete simply supported
beams (4200 mm) constant static sustained and repeated cyclic
loadings were applied mapping the time evolution of deformation.
All experiments were carried out at the Heavy Structures Lab of the
University of Leeds. During tests the mid-span deflection, creep
coefficient and shrinkage strains were monitored for duration of 90
days. The obtained results are set against the values predicted by
Eurocode 2 and the tools within an FE commercial package (i.e.
Midas FEA) to yield that existing knowledge and practise is at times
over-conservative.
Abstract: A sliding door system is used in commercial vehicles
and passenger cars to allow a larger unobstructed access to the
interior for loading and unloading. The movement of a sliding door
on vehicle body is ensured by mechanisms and tracks having special
cross-section which is manufactured by roll forming and stretch
bending process. There are three tracks and three mechanisms which
are called upper, central and lower on a sliding door system. There
are static requirements as strength on different directions, rigidity for
mechanisms, door drop off, door sag; dynamic requirements as high
energy slam opening-closing and durability requirement to validate
these products. In addition, there is a kinematic requirement to find
out force values from door handle during manual operating. In this
study, finite element analysis and physical test results which are
realized for sliding door systems will be shared comparatively.
Abstract: Passive control methods can be utilized to build
earthquake resistant structures, and also to strengthen the vulnerable
ones. In this paper, we studied the effect of this system in increasing
the ductility and energy dissipation and also modeled the behavior of
this type of eccentric bracing, and compared the hysteresis diagram
of the modeled samples with the laboratory samples. We studied
several samples of frames with vertical shear-links in order to assess
the behavior of this type of eccentric bracing. Each of these samples
was modeled in finite element software ANSYS 9.0, and was
analyzed under the static cyclic loading. It was found that vertical
shear-links have a more stable hysteresis loops. Another analysis
showed that using honeycomb beams as the horizontal beam along
with steel reinforcement has no negative effect on the hysteresis
behavior of the sample.
Abstract: A new design of aerostatic thrust bearing is proposed
for high static stiffness. The bearing body, which is mead of polymer
covered with metallic membrane, is held by a circular ring. Such a
support helps form a concave air gap to grasp the air pressure. The
polymer body, which can be made rapidly by either injection or
molding is able to provide extra damping under dynamic loading. The
smooth membrane not only serves as the bearing surface but also
protects the polymer body. The restrictor is a capillary inside a silicone
tube. It can passively compensate the variation of load by expanding
the capillary diameter for more air flux. In the present example, the
stiffness soars from 15.85 N/μm of typical bearing to 349.85 N/μm at
bearing elevation 9.5 μm; meanwhile the load capacity also enhances
from 346.86 N to 704.18 N.
Abstract: In recent years, fire accidents have been steadily
increased and the amount of property damage caused by the accidents
has gradually raised. Damaging building structure, fire incidents bring
about not only such property damage but also strength degradation and
member deformation. As a result, the building structure undermines its
structural ability. Examining the degradation and the deformation is
very important because reusing the building is more economical than
reconstruction. Therefore, engineers need to investigate the strength
degradation and member deformation well, and make sure that they
apply right rehabilitation methods. This study aims at evaluating
deformation characteristics of fire damaged and rehabilitated normal
strength concrete beams through both experiments and finite element
analyses. For the experiments, control beams, fire damaged beams and
rehabilitated beams are tested to examine deformation characteristics.
Ten test beam specimens with compressive strength of 21MPa are
fabricated and main test variables are selected as cover thickness of
40mm and 50mm and fire exposure time of 1 hour or 2 hours. After
heating, fire damaged beams are air-recurred for 2 months and
rehabilitated beams are repaired with polymeric cement mortar after
being removed the fire damaged concrete cover. All beam specimens
are tested under four points loading. FE analyses are executed to
investigate the effects of main parameters applied to experimental
study. Test results show that both maximum load and stiffness of the
rehabilitated beams are higher than those of the fire damaged beams.
In addition, predicted structural behaviors from the analyses also show
good rehabilitation effect and the predicted load-deflection curves are
similar to the experimental results. For the further, the proposed
analytical method can be used to predict deformation characteristics of
fire damaged and rehabilitated concrete beams without suffering from
time and cost consuming of experimental process.
Abstract: It is an established fact that polymers have several
physical limitations such as low stiffness and low resistance to
impact on loading. Hence, polymers do not usually have requisite
mechanical strength for application in various fields. The
reinforcement by high strength fibers provides the polymer
substantially enhanced mechanical properties and makes them more
suitable for a large number of diverse applications. This research
evaluates the effects of particulate Cow bone and Groundnut shell
additions on the mechanical properties and microstructure of cow
bone and groundnut shell reinforced epoxy composite in order to
assess the possibility of using it as a material for engineering
applications. Cow bone and groundnut shell particles reinforced with
epoxy (CBRPC and GSRPC) was prepared by varying the cow bone
and groundnut shell particles from 0-25 wt% with 5 wt% intervals. A
Hybrid of the Cow bone and Groundnut shell (HGSCB) reinforce
with epoxy was also prepared. The mechanical properties of the
developed composites were investigated. Optical microscopy was
used to examine the microstructure of the composites. The results
revealed that mechanical properties did not increase uniformly with
additions in filler but exhibited maximum properties at specific
percentages of filler additions. From the Microscopic evaluation, it
was discovered that homogeneity decreases with increase in % filler,
this could be due to poor interfacial bonding.
Abstract: The fatigue life of tubular joints commonly found in
offshore industry is not only dependent on the value of hot-spot stress
(HSS), but is also significantly influenced by the through-thethickness
stress distribution characterized by the degree of bending
(DoB). The determination of DoB values in a tubular joint is essential
for improving the accuracy of fatigue life estimation using the stresslife
(S–N) method and particularly for predicting the fatigue crack
growth based on the fracture mechanics (FM) approach. In the
present paper, data extracted from finite element (FE) analyses of
tubular KT-joints, verified against experimental data and parametric
equations, was used to investigate the effects of geometrical
parameters on DoB values at the crown 0°, saddle, and crown 180°
positions along the weld toe of central brace in tubular KT-joints
subjected to axial loading. Parametric study was followed by a set of
nonlinear regression analyses to derive DoB parametric formulas for
the fatigue analysis of KT-joints under axial loads. The tubular KTjoint
is a quite common joint type found in steel offshore structures.
However, despite the crucial role of the DoB in evaluating the fatigue
performance of tubular joints, this paper is the first attempt to study
and formulate the DoB values in KT-joints.
Abstract: An experimental and analytical research on shear
buckling of a comparably large polymer composite I-section is
presented. It is known that shear buckling load of a large span
composite beam is difficult to determine experimentally. In order to
sensitively detect shear buckling of the tested I-section, twenty strain
rosettes and eight displacement sensors were applied and attached on
the web and flange surfaces. The tested specimen was a pultruded
composite beam made of vinylester resin, E-glass, carbon fibers and
micro-fillers. Various coupon tests were performed before the shear
buckling test to obtain fundamental material properties of the Isection.
An asymmetric four-point bending loading scheme was
utilized for the shear test. The loading scheme resulted in a high shear
and almost zero moment condition at the center of the web panel. The
shear buckling load was successfully determined after analyzing the
obtained test data from strain rosettes and displacement sensors. An
analytical approach was also performed to verify the experimental
results and to support the discussed experimental program.
Abstract: The main objective of incorporating natural fibers such as Henequen microfibers (NF) into the High Density Polyethylene (HDPE) polymer matrix is to reduce the cost and to enhance the mechanical as well as other properties. The Henequen microfibers were chopped manually to 5-7mm in length and added into the polymer matrix at the optimized concentration of 8 wt %. In order to facilitate the link between Henequen microfibers (NF) and HDPE matrix, coupling agent such as Glycidoxy (Epoxy) Functional Methoxy Silane (GPTS) at various concentrations from 0.1%, 0.3%, 0.5%, 0.7%, 0.9% and 1% by weight to the total fibers were added. The tensile strength of the composite increased marginally while % elongation at break of the composites decreased with increase in silane loading by wt %. Tensile modulus and stiffness observed increased at 0.9 wt % GPTS loading. Flexural as well as impact strength of the composite decreased with increase in GPTS loading by weight %. Dielectric strength of the composite also found increased marginally up to 0.5wt % silane loading and thereafter remained constant.
Abstract: This paper presents experimental investigation and
finite element analysis on buckling behavior of irregular section coldformed
steel columns under axially concentric loading. For the
experimental study, four different sections of columns were tested to
investigate effect of stiffening and width-to-thickness ratio on
buckling behavior. For each of the section, three lengths of 230, 950
and 1900 mm. were studied representing short, intermediate long and
long columns, respectively. Then, nonlinear finite element analyses
of the tested columns were performed. The comparisons in terms of
load-deformation response and buckling mode show good agreement
and hence the FEM models were validated. Parametric study of
stiffening element and thickness of 1.0, 1.15, 1.2, 1.5, 1.6 and 2.0
mm. was analyzed. The test results showed that stiffening effect pays
a large contribution to prevent distortional mode. The increase in wall
thickness enhanced buckling stress beyond the yielding strength in
short and intermediate columns, but not for the long columns.
Abstract: In the present work, the dielectric properties of
Epoxy/MWCNT-muscovite HYBRID and MIXED composites based
on a ratio 30:70 were studied. The multi-wall carbon nanotubes
(MWCNT) were prepared using two methods: (a) MWCNTmuscovite
hybrids were synthesised by chemical vapour deposition
(CVD) and (b) physically mixing muscovite with MWCNT. The
effects of different preparation of the composites and filler loading
were evaluated. It was revealed that the dielectric constants of
HYBRID epoxy composites are slightly higher than MIXED epoxy
composites. It was also indicated that the dielectric constant increased
by increasing the MWCNT filler loading.
Abstract: An experimental study was performed to investigate
the behavior and strength of proposed technique to connect
reinforced concrete (RC) beam to steel or composite columns. This
approach can practically be used in several types of building
construction. In this technique, the main beam of the frame consists
of a transfer part (part of beam; Tr.P) and a common reinforcement
concrete beam. The transfer part of the beam is connected to the
column, whereas the rest of the beam is connected to the transfer part
from each side. Four full-scale beam-column connections were tested
under static loading. The test parameters were the length of the
transfer part and the column properties. The test results show that
using of the transfer part technique leads to modify the deformation
capabilities for the RC beam and hence it increases its resistance
against failure. Increase in length of the transfer part did not
necessarily indicate an enhanced behavior. The test results contribute
to the characterization of the connection behavior between RC beam -
steel column and can be used to calibrate numerical models for the
simulation of this type of connection.
Abstract: Over the past four decades, the fatigue behavior of
nickel-based alloys has been widely studied. However, in recent
years, significant advances in the fabrication process leading to grain
size reduction have been made in order to improve fatigue properties
of aircraft turbine discs. Indeed, a change in particle size affects the
initiation mode of fatigue cracks as well as the fatigue life of the
material. The present study aims to investigate the fatigue behavior of
a newly developed nickel-based superalloy under biaxial-planar
loading. Low Cycle Fatigue (LCF) tests are performed at different
stress ratios so as to study the influence of the multiaxial stress state
on the fatigue life of the material. Full-field displacement and strain
measurements as well as crack initiation detection are obtained using
Digital Image Correlation (DIC) techniques. The aim of this
presentation is first to provide an in-depth description of both the
experimental set-up and protocol: the multiaxial testing machine, the
specific design of the cruciform specimen and performances of the
DIC code are introduced. Second, results for sixteen specimens
related to different load ratios are presented. Crack detection, strain
amplitude and number of cycles to crack initiation vs. triaxial stress
ratio for each loading case are given. Third, from fractographic
investigations by scanning electron microscopy it is found that the
mechanism of fatigue crack initiation does not depend on the triaxial
stress ratio and that most fatigue cracks initiate from subsurface
carbides.
Abstract: Microbial fuel cells (MFCs) represent a promising
technology for simultaneous bioelectricity generation and wastewater
treatment. Catalysts are significant portions of the cost of microbial
fuel cell cathodes. Many materials have been tested as aqueous
cathodes, but air-cathodes are needed to avoid energy demands for
water aeration. The sluggish oxygen reduction reaction (ORR) rate at
air cathode necessitates efficient electrocatalyst such as carbon
supported platinum catalyst (Pt/C) which is very costly. Manganese
oxide (MnO2) was a representative metal oxide which has been
studied as a promising alternative electrocatalyst for ORR and has
been tested in air-cathode MFCs. However the single MnO2 has poor
electric conductivity and low stability. In the present work, the MnO2
catalyst has been modified by doping Pt nanoparticle. The goal of the
work was to improve the performance of the MFC with minimum Pt
loading. MnO2 and Pt nanoparticles were prepared by hydrothermal
and sol gel methods, respectively. Wet impregnation method was
used to synthesize Pt/MnO2 catalyst. The catalysts were further used
as cathode catalysts in air-cathode cubic MFCs, in which anaerobic
sludge was inoculated as biocatalysts and palm oil mill effluent
(POME) was used as the substrate in the anode chamber. The asprepared
Pt/MnO2 was characterized comprehensively through field
emission scanning electron microscope (FESEM), X-Ray diffraction
(XRD), X-ray photoelectron spectroscopy (XPS), and cyclic
voltammetry (CV) where its surface morphology, crystallinity,
oxidation state and electrochemical activity were examined,
respectively. XPS revealed Mn (IV) oxidation state and Pt (0)
nanoparticle metal, indicating the presence of MnO2 and Pt.
Morphology of Pt/MnO2 observed from FESEM shows that the
doping of Pt did not cause change in needle-like shape of MnO2
which provides large contacting surface area. The electrochemical
active area of the Pt/MnO2 catalysts has been increased from 276 to
617 m2/g with the increase in Pt loading from 0.2 to 0.8 wt%. The
CV results in O2 saturated neutral Na2SO4 solution showed that
MnO2 and Pt/MnO2 catalysts could catalyze ORR with different
catalytic activities. MFC with Pt/MnO2 (0.4 wt% Pt) as air cathode
catalyst generates a maximum power density of 165 mW/m3, which
is higher than that of MFC with MnO2 catalyst (95 mW/m3). The
open circuit voltage (OCV) of the MFC operated with MnO2 cathode
gradually decreased during 14 days of operation, whereas the MFC
with Pt/MnO2 cathode remained almost constant throughout the
operation suggesting the higher stability of the Pt/MnO2 catalyst.
Therefore, Pt/MnO2 with 0.4 wt% Pt successfully demonstrated as an
efficient and low cost electrocatalyst for ORR in air cathode MFC with higher electrochemical activity, stability and hence enhanced
performance.