Abstract: In this paper we present the design of an optical
device based on a Herriott multi-pass cell fabricated on a small sized
acrylic slab for heat flux measurements using the deflection of a laser
beam propagating inside the cell. The beam deflection is produced by
the heat flux conducted to the acrylic slab due to a gradient in the
refractive index. The use of a long path cell as the sensitive element
in this measurement device, gives the possibility of high sensitivity
within a small size device. We present the optical design as well as
some experimental results in order to validate the device’s operation
principle.
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: When high strength reinforced concrete is exposed to
high temperature due to a fire, deteriorations occur such as loss in
strength and elastic modulus, cracking and spalling of the concrete.
Therefore, it is important to understand risk of structural safety in
building structures by studying structural behaviors and rehabilitation
of fire damaged high strength concrete structures. This paper aims at
investigating rehabilitation effect on fire damaged high strength
concrete beams using experimental and analytical methods. In the
experiments, flexural specimens with high strength concrete are
exposed to high temperatures according to ISO 834 standard time
temperature curve. From four-point loading test, results show that
maximum loads of the rehabilitated beams are similar to or higher than
those of the non-fire damaged RC beam. In addition, structural
analyses are performed using ABAQUS 6.10-3 with same conditions
as experiments to provide accurate predictions on structural and
mechanical behaviors of rehabilitated RC beams. The parameters are
the fire cover thickness and strengths of repairing mortar. Analytical
results show good rehabilitation effects, when the results predicted
from the rehabilitated models are compared to structural behaviors of
the non-damaged RC beams. In this study, fire damaged high strength concrete beams are
rehabilitated using polymeric cement mortar. The predictions from the
finite element (FE) models show good agreements with the
experimental results and the modeling approaches can be used to
investigate applicability of various rehabilitation methods for further
study.
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: Concrete is strong in compression however weak in
tension. The tensile strength as well as ductile property of concrete
could be improved by addition of short dispersed fibers. Polyethylene
terephthalate (PET) fiber obtained from hand cutting or mechanical
slitting of plastic sheets generally used as discrete reinforcement in
substitution of steel fiber. PET fiber obtained from the former process
is in the form of straight slit sheet pattern that impart weaker
mechanical bonding behavior in the concrete matrix. To improve the
limitation of straight slit sheet fiber the present study considered two
additional geometry of fiber namely (a) flattened end slit sheet and
(b) deformed slit sheet. The mix for plain concrete was design for a
compressive strength of 25 MPa at 28 days curing time with a watercement
ratio of 0.5. Cylindrical and beam specimens with 0.5% fibers
volume fraction and without fibers were cast to investigate the
influence of geometry on the mechanical properties of concrete. The
performance parameters mainly studied include flexural strength,
splitting tensile strength, compressive strength and ultrasonic pulse
velocity (UPV). Test results show that geometry of fiber has a
marginal effect on the workability of concrete. However, it plays a
significant role in achieving a good compressive and tensile strength
of concrete. Further, significant improvement in term of flexural and
energy dissipation capacity were observed from other fibers as
compared to the straight slit sheet pattern. Also, the inclusion of PET
fiber improved the ability in absorbing energy in the post-cracking
state of the specimen as well as no significant porous structures.
Abstract: In this paper, analysis of an infinite beam resting on
multilayer tensionless extensible geosynthetic reinforced granular
fill-poor soil system overlying soft soil strata under moving load with
constant velocity is presented. The beam is subjected to a
concentrated load moving with constant velocity. The upper
reinforced granular bed is modeled by a rough membrane embedded
in Pasternak shear layer overlying a series of compressible nonlinear
winkler springs representing the underlying the very poor soil. The
multilayer tensionless extensible geosynthetic layer has been
assumed to deform such that at interface the geosynthetic and the soil
have some deformation. Nonlinear behaviour of granular fill and the
very poor soil has been considered in the analysis by means of
hyperbolic constitutive relationships. Governing differential
equations of the soil foundation system have been obtained and
solved with the help of appropriate boundary conditions. The solution
has been obtained by employing finite difference method by means of
Gauss-Siedal iterative scheme. Detailed parametric study has been
conducted to study the influence of various parameters on the
response of soil–foundation system under consideration by means of
deflection and bending moment in the beam and tension mobilized in
the geosynthetic layer. These parameters include magnitude of
applied load, velocity of load, damping, ultimate resistance of poor
soil and granular fill layer. Range of values of parameters has been
considered as per Indian Railway conditions. This study clearly
observed that the comparisons of multilayer tensionless extensible
geosynthetic reinforcement with poor foundation soil and magnitude
of applied load, relative compressibility of granular fill and ultimate
resistance of poor soil has significant influence on the response of
soil–foundation system.
Abstract: The purpose of this project is to propose a quick and
environmentally friendly alternative to measure the quality of oils
used in food industry. There is evidence that repeated and
indiscriminate use of oils in food processing cause physicochemical
changes with formation of potentially toxic compounds that can
affect the health of consumers and cause organoleptic changes. In
order to assess the quality of oils, non-destructive optical techniques
such as Interferometry offer a rapid alternative to the use of reagents,
using only the interaction of light on the oil. Through this project, we
used interferograms of samples of oil placed under different heating
conditions to establish the changes in their quality. These
interferograms were obtained by means of a Mach-Zehnder
Interferometer using a beam of light from a HeNe laser of 10mW at
632.8nm. Each interferogram was captured, analyzed and measured
full width at half-maximum (FWHM) using the software from
Amcap and ImageJ. The total of FWHMs was organized in three
groups. It was observed that the average obtained from each of the
FWHMs of group A shows a behavior that is almost linear, therefore
it is probable that the exposure time is not relevant when the oil is
kept under constant temperature. Group B exhibits a slight
exponential model when temperature raises between 373 K and 393
K. Results of the t-Student show a probability of 95% (0.05) of the
existence of variation in the molecular composition of both samples.
Furthermore, we found a correlation between the Iodine Indexes
(Physicochemical Analysis) and the Interferograms (Optical
Analysis) of group C. Based on these results, this project highlights
the importance of the quality of the oils used in food industry and
shows how Interferometry can be a useful tool for this purpose.
Abstract: This paper presents modeling and simulation of
flexible robot in an underwater environment. The underwater
environment completely contrasts with ground or space environment.
The robot in an underwater situation is subjected to various dynamic
forces like buoyancy forces, hydrostatic and hydrodynamic forces.
The underwater robot is modeled as Rayleigh beam. The developed
model further allows estimating the deflection of tip in two
directions. The complete dynamics of the underwater robot is
analyzed, which is the main focus of this investigation. The control of
robot trajectory is not discussed in this paper. Simulation is
performed using Symbol Shakti software.
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: In recent years, honeycomb fiber reinforced plastic
(FRP) sandwich panels have been increasingly used in various
industries. Low weight, low price and high mechanical strength are
the benefits of these structures. However, their mechanical properties
and behavior have not been fully explored. The objective of this
study is to conduct a combined numerical-statistical investigation of
honeycomb FRP sandwich beams subject to torsion load. In this
paper, the effect of geometric parameters of sandwich panel on
maximum shear strain in both face and core and angle of torsion in a
honeycomb FRP sandwich structures in torsion is investigated. The
effect of Parameters including core thickness, face skin thickness,
cell shape, cell size, and cell thickness on mechanical behavior of the
structure were numerically investigated. Main effects of factors were
considered in this paper and regression equations were derived.
Taguchi method was employed as experimental design and an
optimum parameter combination for the maximum structure stiffness
has been obtained. The results showed that cell size and face skin
thickness have the most significant impacts on torsion angle,
maximum shear strain in face and core.
Abstract: Processing of Al-19.4Si alloy by high intensive
electron beam has been carried out and multiple increases in fatigue
life of the material have been revealed. Investigations of structure and
surface modified layer destruction of Al-19.4Si alloy subjected to
multicycle fatigue tests to fracture have been carried out by methods
of scanning electron microscopy. The factors responsible for the
increase of fatigue life of Al-19.4Si alloy have been revealed and
analyzed.
Abstract: Numerical investigations were conducted to study the
influence of flexural reinforcement ratio on the diagonal cracking
strength and ultimate shear strength of reinforced concrete (RC)
beams without stirrups. Three-dimensional nonlinear finite element
analyses (FEAs) of the beams with flexural reinforcement ratios
ranging from 0.58% to 2.20% subjected to a mid-span concentrated
load were carried out. It is observed that the load-deflection and loadstrain
curves obtained from the numerical analyses agree with those
obtained from the experiments. It is concluded that flexural
reinforcement ratio has a significant effect on the shear strength and
deflection capacity of RC beams without stirrups. The predictions of
diagonal cracking strength and ultimate shear strength of beams
obtained by using the equations defined by a number of codes and
researchers are compared with each other and with the experimental
values.
Abstract: Single angle connections, which are bolted to the beam
web and the column flange, are studied to investigate their
moment-rotation behavior. Elastic–perfectly plastic material behavior
is assumed. ABAQUS software is used to analyze the nonlinear
behavior of a single angle connection. The identical geometric and
material conditions with Lipson’s test are used for verifying finite
element models. Since Kishi and Chen’s Power model and Lee and
Moon’s Log model are accurate only for a limited range of mechanism,
simpler and more accurate hyperbolic function models are proposed.
Abstract: This study suggests the estimation method of stress
distribution for the beam structures based on TLS (Terrestrial Laser
Scanning). The main components of method are the creation of the
lattices of raw data from TLS to satisfy the suitable condition and
application of CSSI (Cubic Smoothing Spline Interpolation) for
estimating stress distribution. Estimation of stress distribution for the
structural member or the whole structure is one of the important
factors for safety evaluation of the structure. Existing sensors which
include ESG (Electric strain gauge) and LVDT (Linear Variable
Differential Transformer) can be categorized as contact type sensor
which should be installed on the structural members and also there are
various limitations such as the need of separate space where the
network cables are installed and the difficulty of access for sensor
installation in real buildings. To overcome these problems inherent in
the contact type sensors, TLS system of LiDAR (light detection and
ranging), which can measure the displacement of a target in a long
range without the influence of surrounding environment and also get
the whole shape of the structure, has been applied to the field of
structural health monitoring. The important characteristic of TLS
measuring is a formation of point clouds which has many points
including the local coordinate. Point clouds are not linear distribution
but dispersed shape. Thus, to analyze point clouds, the interpolation is
needed vitally. Through formation of averaged lattices and CSSI for
the raw data, the method which can estimate the displacement of
simple beam was developed. Also, the developed method can be
extended to calculate the strain and finally applicable to estimate a
stress distribution of a structural member. To verify the validity of the
method, the loading test on a simple beam was conducted and TLS
measured it. Through a comparison of the estimated stress and
reference stress, the validity of the method is confirmed.
Abstract: Si ion implantation was widely used to synthesize
specimens of SiO2 containing supersaturated Si and subsequent high
temperature annealing induces the formation of embedded
luminescent Si nanocrystals. In this work, the potentialities of excimer
UV-light (172 nm, 7.2 eV) irradiation and rapid thermal annealing
(RTA) to enhance the photoluminescence and to achieve low
temperature formation of Si nanocrystals have been investigated. The
Si ions were introduced at acceleration energy of 180 keV to fluence of
7.5 x 1016 ions/cm2. The implanted samples were subsequently
irradiated with an excimer-UV lamp. After the process, the samples
were rapidly thermal annealed before furnace annealing (FA).
Photoluminescence spectra were measured at various stages at the
process. We found that the luminescence intensity is strongly
enhanced with excimer-UV irradiation and RTA. Moreover, effective
visible photoluminescence is found to be observed even after FA at
900 oC, only for specimens treated with excimer-UV lamp and RTA.
We also prepared specimens of Si nanocrystals embedded in a SiO2 by
reactive pulsed laser deposition (PLD) in an oxygen atmosphere. We
will make clear the similarities and differences with the way of
preparation.
Abstract: An Acoustic Micro-Energy Harvester (AMEH) is
developed to convert wasted acoustical energy into useful electrical
energy. AMEH is mathematically modeled using Lumped Element
Modelling (LEM) and Euler-Bernoulli beam (EBB) modelling. An
experiment is designed to validate the mathematical model and assess
the feasibility of AMEH. Comparison of theoretical and experimental
data on critical parameter value such as Mm, Cms, dm and Ceb showed
the variances are within 1% to 6%, which is reasonably acceptable.
Then, AMEH undergoes bandwidth tuning for performance
optimization. The AMEH successfully produces 0.9V/(m/s^2) and
1.79μW/(m^2/s^4) at 60Hz and 400kΩ resistive load which only
show variances about 7% compared to theoretical data. At 1g and
60Hz resonance frequency, the averaged power output is about
2.2mW which fulfilled a range of wireless sensors and
communication peripherals power requirements. Finally, the design
for AMEH is assessed, validated and deemed as a feasible design.
Abstract: In this study free vibration analysis of aluminum
honeycomb sandwich structures were carried out experimentally and
numerically. The natural frequencies and mode shapes of sandwich
structures fabricated with different configurations for clamped-free
boundary condition were determined. The effects of lower and upper
face sheet thickness, the core material thickness, cell diameter, cell
angle and foil thickness on the vibration characteristics were
examined. The numerical studies were performed with ANSYS
package. While the sandwich structures were modeled in ANSYS the
continuum model was used. Later, the numerical results were
compared with the experimental findings.
Abstract: We investigate experimentally and theoretically the
dynamics of a capacitive resonator under mixed frequency excitation
of two AC harmonic signals. The resonator is composed of a proof
mass suspended by two cantilever beams. Experimental
measurements are conducted using a laser Doppler Vibrometer to
reveal the interesting dynamics of the system when subjected to twosource
excitation. A nonlinear single-degree-of-freedom model is
used for the theoretical investigation. The results reveal combination
resonances of additive and subtractive type, which are shown to be
promising to increase the bandwidth of the resonator near primary
resonance frequency. Our results also demonstrate the ability to shift
the combination resonances to much lower or much higher frequency
ranges. We also demonstrate the dynamic pull-in instability under
mixed frequency excitation.
Abstract: Metal thin-walled members have been widely used in
building industry. Usually they are utilized as purlins, girts or ceiling
beams. Due to slenderness of thin-walled cross-sections these
structural members are prone to stability problems (e.g. flexural
buckling, lateral torsional buckling). If buckling is not
constructionally prevented their resistance is limited by buckling
strength. In practice planar members of roof or wall cladding can be
attached to thin-walled members. These elements reduce
displacement of thin-walled members and therefore increase their
buckling strength. If this effect is taken into static assessment more
economical sections of thin-walled members might be utilized and
certain savings of material might be achieved. This paper focuses on
problem of determination of critical load of steel thin-walled beams
with lateral continuous restraint which is crucial for lateral torsional
buckling assessment.
Abstract: The 5th generation of mobile networks is term used in
various research papers and projects to identify the next major phase
of mobile telecommunications standards. 5G wireless networks will
support higher peak data rate, lower latency and provide best
connections with QoS guarantees.
In this article, we discuss various promising technologies for 5G
wireless communication systems, such as IPv6 support, World Wide
Wireless Web (WWWW), Dynamic Adhoc Wireless Networks
(DAWN), BEAM DIVISION MULTIPLE ACCESS (BDMA), Cloud
Computing, cognitive radio technology and FBMC/OQAM.
This paper is organized as follows: First, we will give introduction
to 5G systems, present some goals and requirements of 5G. In the
next, basic differences between 4G and 5G are given, after we talk
about key technology innovations of 5G systems and finally we will
conclude in last Section.