Proposing an Error Estimator for Collocated Discreet Least Square (CDLS) Meshless Method
M.H
Afshar
author
M.
Lashckarbolok
author
text
article
2011
per
The error estimation should be a main tool in every adaptivity process. This is the reason for
the great importance of the estimation. It allows us to know the quality of the solution, and
hence, if it is acceptable or not. Moreover, it provides some information about the changes
that are necessary to be made in the mathematical model to reach, in an economic way, the
desired solution. In this paper, a new error estimator for solving the hyperbolic problems to be
used in conjunction with the Collocated Discreet Least Square Meshless (CDLS) method is
presented. The error estimator is shown to be naturally related to the least-squares method,
providing a suitable measure of the errors in the solution. The estimator is easily calculated by
the use of already existing matrices of the least-squares computation, hence, it is very cheap.
The proposed error estimator was implemented with CDLS method to solve three benchmark
examples from the literature and the effect of collocation points on them was investigated.
These examples are nonlinear burgers equation, dam break problem and the problem of
shoaling a wave on sloping shallow waters. The results showed that the error estimator works
very well in all numerical examples.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
11
v.
2
no.
2011
1
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http://mcej.modares.ac.ir/article_1786_b475ae6df24d4517edb0b1a3cc32d02e.pdf
Comparison between Epoxy and Waterproof Sealers in
TiO2 Immobilization on Concrete Surface for Treating
Phenolic Wastewater by Photocatalytic Process
M.
Delnavaz
author
B.
Ayati
author
H.
Ganjidoust
author
S.
Sanjabi
author
text
article
2011
per
Abstract:
Two kinds of concrete sealers including epoxy and waterproof were used to immobilize TiO2
nano-particles on concrete surfaces for treating 25-500 mg/L synthetic phenolic wastewater
using photocatalytic process. The reactor consisted of contaminated tank, photocatalytic and
aeration zones. Irradiation of TiO2 was performed by UV-A lamps at different intensity (4.42-
8.9 mW.cm-2) placed 10 cm above the concrete surfaces. SEM and EDX analys is showed a
uniform appearance of TiO2 catalyst on the concrete. In influent phenol concentration (100
mg/L), pH=7 and retention time (4 hr), the removal efficiency by epoxy sealer was more than
20% compared to the waterproof sealer because of hydrophobic effects. Reduction of removal
efficiency was less than 2% for the epoxy sealer after several iterations of the process. Finally,
the effects of intensity and wavelength of UV lamp and system pH in removal efficiency were
evaluated.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
11
v.
2
no.
2011
http://mcej.modares.ac.ir/article_1787_0ea86ec1f043b4287cde46a765d5c9e3.pdf
Considering the Effect of Six Component of Near-Fault
Earthquake Ground Motions on the Three Dimensional Systems
H.
Shakib
author
M.
Alirezaie
author
text
article
2011
per
Abstract:
The rotational components of seismic strong-motion are attracting attention since it is
becoming evident that it may contribute considerably to the overall response of structures to
earthquake motions. Also, it is clear that the effects of near-fault ground motions with large
velocity pulses, large amplitude, long period, and pulse type of excitation can create critical
working conditions. In the near-field of an earthquake the effects of the rotational components
of ground motion may not be negligible specially for important structures. In this paper, an
improved method for calculating the time histories of torsional and rocking components of
ground motion corresponding to a set of three recorded orthogonal translational components
is presented. The current processing of earthquake records provide information only about the
three translational (two horizontal and one vertical) components of the ground motion,
primarily because these are the only components that can be directly instrumentally measured.
However, the translational components during a seismic event are always accompanied by
rotational components because of the traveling wave effects. Several studies have shown the
importance of rotational components in the seismic analysis and design of structures. The
seismic design codes also prescribe “accidental eccentricity” in the design force calculations
to account for the unknown torsional inputs and unintended eccentricity in the design of a
building. One of the reasons why this input is not explicitly taken into account in the seismic
design codes is the lack of reliable information on torsional ground spectra. In this study the
three rotational components of earthquakes records is generated artificial by three
translational components. The torsional motions in terms of time derivative of translational
components and shear wave velocity of site are derived. Seven translational earthquake
records of far fault and seven translational earthquake records from near-fault have been
selected. The rotational components of far fault and near fault are generated the response
spectral for translational as well as rotational components are presented and compare to each
other in other to verify the characteristic of the near fault response spectral compare to the far
fault response spectral. Furthermore, the effect of rotational motion on structural response is
investigated. Therefore the six components of earthquakes records of far fault and near fault
applied to the idealized system model and the response of the system are determine.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
11
v.
2
no.
2011
http://mcej.modares.ac.ir/article_1788_81749d2615e0e75e3b0ccbf3173ba377.pdf
Seismic Response and Free Vibration of Rectangular
Liquid Storage Tanks
A.S
Ghods
author
M.R
Esfahani
author
text
article
2011
per
Abstract:
The experimental study of structural vibration is often performed to determine the modal
parameters of a structure or to verify the theoretical models and predictions. The first phase of
this research involved the experimental determination of the modal properties of a rectangular
steel tank with different levels of water. The natural frequencies obtained from the
experiments were compared to those calculated by the analytical models.
In the second phase, a procedure for computing hydrodynamic pressures in rectangular tanks
is proposed. This procedure considers the effect of tank wall flexibility in determining the
hydrodynamic pressures produced by the impulsive response. Based on a two-dimensional
model of the tank wall, a dynamic time-history analysis was carried out. The results were
compared with other models based on the current design practice codes and standards, which
use a lumped mass approach. The comparison shows that, in most cases, the lumped mass
approach overestimates the base shear. The effect of wall flexibility on wall displacements
and base shears are also discussed.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
11
v.
2
no.
2011
http://mcej.modares.ac.ir/article_1789_c757bee329067346416d2bf27c709c72.pdf
dx.doi.org/-
A Study on the Effect of Section Shape of RC Columns on
the Loss of Load-Carrying Capacity in Fire
M.A
Lotfollahi Yaghin1
author
P.
Najafi
author
text
article
2011
per
Abstract:
In the present article, the effect of fire on the axial compressive strength of reinforced
concrete (RC) columns was studied. Method of research was laboratory investigation. The
axial compressive strength of RC columns was measured by applying variable heat in
different time intervals in the process of experiment.
Thirty two samples of fine-scale RC columns with square and circular cross sections, the
gross cross section area of 225 cm² (for both sections), longitudinal reinforcement area of 3.1
cm², general height of 30 cm for all samples and other uniform structural characteristics
( 25 c f MPa , 300 y f MPa ) were exposed to fire and different temperatures (300°C to 700°C)
were applied in the time intervals of 30, 60 and 90 minutes. Then they were exposed to axial
loading by hydraulic jack with 200 ton capacity, and their strengths were measured. It is
worth noting that, in the heating stage of samples, caps with thermal insulation were used in
order to prevent instantaneous strain at the two ends of the samples. By carrying out the
experiments, it became clear that at the time of fire, two factors, i.e., the "period of fire" and
"temperature of fire" resulted in the loss of strength in RC columns. Of course, the "period of
fire" factor was more effective than temperature of fire. It also became clear that RC columns
with circular cross section fail faster in comparison with the columns with square cross
sections at the time of fire. In order to evaluate and measure the results obtained, a relative
factor called "Fire Factor" was utilized. The results indicated that the amount of axial
compressive strength loss resulting from fire is approximately 3-5% greater in circular RC
columns in comparison with square columns.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
11
v.
2
no.
2011
http://mcej.modares.ac.ir/article_1790_503c8b106e7104c00da907bd240c167e.pdf
The Experimental Study of the Effect of FRP Laminates
on Shear Strength of RC Fixed Ended Deep Beams
A
Arabzade
author
H.
Mahanpoor
author
text
article
2011
per
Abstract:
Very little researches hasbeen performed about strengthening and repairing of deep beams. In
this paper, shear strength of Reinforced Concrete (RC) deep beams in two cases of repair and
strengthening with Carbon Fiber Reinforced Polymer (CFRP) is evaluated. To achieve the
objective of the research, six deep beams were constructed in three coupling groups with
constant reinforcement arrangement and concrete strength and clear span-to-depth ratio of 2.
In each group, one beam without strengthening was used as reference beam. This beam was
loaded up to failure and then reinforced by CFRP and reloaded again. The other one was
reinforced before loading, similar to the first one. The results indicated that repair and
strengthening the beams would increase the ultimate load. In general, when one directional
CFRP strip is attached to the face of the beams perpendicular to crack with the angle of 45o
(SS45), the ultimate strength is increased by 7 and 61%, respectively. Therefore it can be
conclude that SS45 system because of uniform distribution of CFRP perpendicular to the
direction of shear cracks, could be the best method for repair and strengthening of tested fixed
ended deep beams and in comparison with reference beam, if it used to repair the damaged
beam, the ultimate load would increase up to 7 percent.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
11
v.
2
no.
2011
http://mcej.modares.ac.ir/article_1791_9cf8b75b902e8896df17329d36c7271e.pdf
dx.doi.org/-
Numerical Modeling of Confinement Effects on Failure
Pattern of Brittle Rocks in Triaxial Tests
A
Golshani
author
H
Rajabi
author
text
article
2011
per
Abstract:
One of the most important goals of the experiments is to determine deformation and strength
of the rock specimen under applying triaxial load. The status of failure condition is one of the
subjects, which can be used in soil mechanic and foundation engineering applications. To
investigate the effect of confining pressure on the triaxial test, the rock was considered as
bonded-particles method and simulated by PFC3D program. To compare the mechanical
behavior and failure pattern of the numerical and experimental results at uniaxial and triaxial
tests at the same conditions, the Young's modulus, Poisson's ratio and maximum axial stress
were considered. On the other hand, the microcracks growth and change of failure pattern at
the modeling of the uniaxial and triaxial tests with different confining pressures up to failure
point were reported. According to the experimental work, the number density of microcracks
decreases from starting value and remains almost constant up to the failure beyond that point.
Comparison of the numerical and experimental results of maximum axial stress and the
Poisson's ratio revealed a good accordance. The simulated Young's modulus was smaller in
comparison with the experimental ones and the difference was about 36%, which seems to be
due to absence of the pre-existing microcracks on the model. The initial number density of
microcracks at the model was zero and increased while microcracking. Also the sudden
increment around the maximum stress was observed, which is because of unstable growing of
microcracks near the maximum stress. In all uniaxial and triaxial tests with different confining
stresses, the number density of microcracks during the failure remained almost constant,
which can be considered as a proof of failure occurring in the model. The experimental results
indicated a similar trend as well.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
11
v.
2
no.
2011
http://mcej.modares.ac.ir/article_1792_47a310d7c475440d97bf4baaaf6f848a.pdf
Effect of Rail Corrugation on the Pressure between
Sleeper and Ballast
J.A
Zakeri
author
M
Gharouninik
author
M.
Moazami
author
text
article
2011
per
Abstract:
Because of the complicated nature of track and train, investigation of interactions between
them has been always an complex problem in railway engineering. Perceiving of this
interaction is an complex problem only in track with various defects but also in the track
without defects. Estimating of the forces exerted on track and train will be much difficult
when a defect such as rail corrugation is added to this interaction. If an accurate computer
model is available, we can have a good forecast of these forces. However, precise estimating
of them is only reached field measurement.
In this study, we tried to present a good estimation of passenger and freight wagon forces on
track with rail corrugation defect. The pressure between sleeper and ballast was calculated by
these forces. Afterwards pressure (on ballast surface)-rail corrugation wavelength diagrams
was determined. By using these diagrams, the rail corrugation wavelength where ballast
stresses were beyond the permissible limit for each type of operation, was determined (it was
named critical corrugation wavelength). A computer model was developed in ADAMS/Rail
software for passenger and freight wagons with various speeds to estimate the forces exerted
on the ballasted track with corrugation defect.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
11
v.
2
no.
2011
http://mcej.modares.ac.ir/article_1793_562de81c5a3fab0c53254a3dda873f20.pdf
The Use of Dynamic Probing For Investigation of Fine
Soils and Evaluation of Undrained Shear Strength
M.
Khodaparast
author
A.
Fakher
author
text
article
2011
per
Abstract:
The Dynamic Probe is an effective and efficient tool used in site investigation. It is more
economic than the use of boring equipment particularly when the depth of exploration is
moderate. The paper covers the design and development of a dynamic probing rig and a new
soil sampler to increase the efficiency of conventional dynamic probes. The repeatability of
the results are considered and correlations between dynamic probing results and undrained
shear strength identified. A new equation relating dynamic resistance to undrained shear
strength is proposed. The paper encourages the wider application of dynamic probing for site
investigation in fine soils.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
11
v.
2
no.
2011
http://mcej.modares.ac.ir/article_1794_0f61bfa535bf7a03b04c7db1cff1dfde.pdf
Investigation of Seismic Behavior of Frame-Panel Systems
M.
Gerami
author
S.A.R
Kaboli
author
text
article
2011
per
Abstract:
Implementation of 3D panels in buildings is increasing due to the importance of lightening,
optimizing and reduction of fuel consumption. These panels are used as interior, outer, load
bearing and partitioning walls beside the structural frame without considering the frame-panel
interaction. Steel frames act in shear mode and panel frames act in flexure; hence, combining
the two systems will change the structural behavior of each system. So, investigation of the
seismic behavior of combined systems using nonlinear dynamic methods seems to be
mandatory.
In this article, frames with 3, 5 and 10 stories (filled in different bays by panel) were modeled
in ANSYS. These frames were then analyzed under Elcentro, Tabas and Naghan seismic
records. The results illustrated that using panel not only results in more acceptable drifts, but
also it lets the system to have a better seismic behavior and more energy dissipation. For
example, the displacements of the structures in the highest level decrease more than 35% by
using one bay panel for filling steel frames. This amount of filling also leads to more than
100% increase in the area under the base shear-displacement diagram of a steel frame.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
11
v.
2
no.
2011
http://mcej.modares.ac.ir/article_1795_e1f0077b36e1fd80b988da6524ea3e7e.pdf