Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
11
1
2011
4
1
A New Instrument for Measuring the Bed Profile
0
0
FA
M
Vaghefi
N
M
Ghodsian
Y
M
Behnam Taghadosi3
N
Abstract:
The measurement of bed profile in a mobile bed is very important for hydraulic engineers.
The traditional instrument for this purpose is point gage. Working with a point gage is a
difficult task, especially when bed topography of large size scales has to be recorded. In this
paper, a new instrument for measuring the bed profile in a mobile bed called "Laser Bed
Profiler" is introduced. The developed instrument uses the laser beam and without touching
the bed records the data.
The laser bed profiler instrument has been designed with the purpose of analyzing the scoring
pattern in laboratory channels. This instrument is capable of measuring the changes of the bed
profile in straight and bend channels. Moreover, the instrument is capable of recording the
bed profile around various hydraulic structures (such as bridge piers, abutment, spur dike and
lateral intake). Amongst the main advantages of the developed instrument are: 1) recording
the data without touching the bed surface and 2) its high speed and precision. This paper gives
an overview of the design and advantages of the developed instrument. The developed
software and hardware are also introduced. Moreover, a typical applications of the instrument
and its comparison with a digital point gage in laboratory channel (straight path, 90 degree
bend and around a spur dike) are also presented.
Laser bed profile,Point gage,Bed topography,scour
http://mcej.modares.ac.ir/article-16-9809-en.html
http://mcej.modares.ac.ir/article-16-9809-en.pdf
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
11
1
2011
4
1
Geometrical Inclusion - Matrix Modeling of Concrete
0
0
FA
I.
Rasoolan
Y
A
Sadrnejhad
N
A
Bagheri
N
Abstract:
Recent experiments and analytical investigations have shown that the mechanical behavior of
concrete is strongly dependent on its microstructure. However, the concrete behavior is
composed of three phases as grains, cement paste and interfacial transition zone. The grains
type, size and distribution of aggregate affect the concrete's characteristics. Because of the
random distribution and size variation of aggregate in concrete, the modeling of concrete's
behavior based on component in meso structure is difficult and so we must use simple
assumption.
In this paper, through mixing design and grading curve, a simple method was developed to
replace real aggregate with equivalent sphere aggregate with effective diameter.
So we can use simple methods instead of complex numeral and randomness or X ray methods
to find effective diameter and to determine two arrangements with maximum and minimum
aggregate volume as a repeatable basical element. As a result, we can use this element for
modeling the behavior of sample concrete in meso scale and three phases.
Aggregates,Equale shape,concrete,Interfacial zone,Grading,Specific surface
http://mcej.modares.ac.ir/article-16-10551-en.html
http://mcej.modares.ac.ir/article-16-10551-en.pdf
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
11
1
2011
4
1
Evaluation of Marun Dam Behavior During the
Construction and Operation Period Using Instrumentation-
0
0
FA
A.R.
Tabibnejad
N
R
Mahin Roosta
Y
Abstract:
Marun dam with a height of 170m is one of the largest embankment dams in Iran. The dam is
a zoned rockfill dam with a central clay core. Due to the importance of safety and stability
control of the dam body, a complete monitoring network including different instrumentation
systems, has been designed and installed in the dam body.
In this paper, the data obtained from the instruments, installed in the clay core, were
processed and interpreted. Based on the outcomes, the behavior of the dam body during the
construction in the impounding stage and operation period was evaluated and discussed. This
study consists of three major parts including: the pore pressure distributions, stress states
conditions in the clay core and evaluation of its settlements and deformations in the dam
body.
Marun dam,Embankment dam,Clay core,Monitoring network and
instrumentation,Stability control
http://mcej.modares.ac.ir/article-16-4890-en.html
http://mcej.modares.ac.ir/article-16-4890-en.pdf
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
11
1
2011
4
1
Importance of Joint Geomerical Parameters on the Safety
of Concrete Arch Dam Abutments
0
0
FA
saeed
yazdany
N
mahmood
yazdany
Y
mohamad
ahmady
N
Abstract:
Concrete arch dams often need sound and strong foundation and abutments due to the usually
large hydrostatic pressure imposed on the abutments. Moreover, it is required to limit the
water leakage through the abutments and foundation. On the other hand, a hard rock mass
often contains joints and discontinuuites, wich are partially created during the thermal and
techtonical activities. Several researches have shown that in most cases, the stability and
permeability of rock masses are governed by the joints. Therefore, it is necessary to consider
the joint roles for preliminary evaluation of a rock mass as abutment and foundation of a
concrete arch dam. In addition, the interaction of hydraulic and mechanical behaviour of
joints causes the saturated rock masses to act more complicated, hence, it must be considered
in the estimation of stability and leakage. In this paper, the effects of geometrical parameters
of joints including joint orientations and initial apertures on the safety of a concrete arch dam
were evaluated using UDEC software. A two-dimentional model including the waterflow
through the joints and a loading from dam and the reservoir was simulated in the analyses. In
this study, the dam stresses imposed on the abutment were applied instead of dam body
modeling. In all analyses, the hydromechanical interaction effects were considered. The
values of maximum sliding, maximum opening and the maximum resulting waterflow along
the discontinuities were adopted as criteria for estimating the dam abutment safety. The
results demonstrate that the joint sets pattern and initial hydraulic aperture of joints dominate
the stability of arch dam abutments.
Jointed rock mass,concrete arch dam,Abutment,Hydromechanical
http://mcej.modares.ac.ir/article-16-6642-en.html
http://mcej.modares.ac.ir/article-16-6642-en.pdf
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
11
1
2011
4
1
A Seismic Analysis Model for the Evaluation of
Retrofitted Old RC Buildings
0
0
FA
M
Zeinoddini
Y
A
Dabiri
N
J.
Fakheri
N
Abstract:
In seismic areas, a majority of old RC buildings have only been designed for gravity loads or
according to outdated seismic codes. Before1970s, smooth rebars were also extensively used
in RC structures. As these buildings are still functioning, they need to be reassessed against
seismic demands. Load bearing behaviour of concrete structures reinforced with smooth
rebars is considerably affected by the slip deformation of the plain rebars. In this study, a
specific finite element model has been proposed for evaluating the seismic performance of
these structures. The slipping characteristics of smooth rebars have been incorporated in this
model. For this purpose, a tailored stress-strain property has been assigned to the steel fibers
in tension. The model has then been calibrated/verified against several sets of experimental
results from others. In general, satisfactory correlations have been noticed between the
experimental results and the predictions from the proposed fiber element model. The model
has also been used for a full seismic assessment of an existing RC building, having smooth
rebars. In addition, the structure has been retrofitted with steel bracing, viscose dampers and
base isolators' schemes and their nonlinear seismic performance has been evaluated using the
proposed model.
Old RC structures,Smooth rebars,Modified fiber element model,Seismic Retrofitting
http://mcej.modares.ac.ir/article-16-8426-en.html
http://mcej.modares.ac.ir/article-16-8426-en.pdf
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
11
1
2011
4
1
The Influence of Aggregate Gradation on the Permeability
and Mechanical Properties of Porous Concrete
0
0
FA
B
Shirgir
N
A
HASANY
Y
H
Alizadeh Goodarzi3
N
Abstract:
The influence of aggregate gradation on the permeability and mechanical properties of porous
concrete was investigated. A standard mix and five standard aggregate gradations were
selected. Since porous concrete contains no or little fine aggregate, its structure is formed by
the interlocking of the coarse aggregates. So the aggregate gradation is a very important
characteristic as it influences such properties of porous concrete as strength and permeability.
There was statistically significant difference between the results from the strength and water
permeability of porous concrete with different aggregate gradations. For example, the
difference between minimum and maximum compressive strength was 33%, and a 20%
difference was obtained for flexural strength. It was found that the uniformity coefficient has
influence on the flexural strength of porous concrete. In order to develop the flexural bending
strength prediction model, the two parameters of compressive and uniformity coefficient were
explained using linear regression model. The obtained Goodness of fit (R2) for this model was
0.879. The results of the current investigation showed how fine aggregate influenced the
compressive and permeability of porous concrete.
Porous concrete,permeability,strength,uniformity coefficient
http://mcej.modares.ac.ir/article-16-5590-en.html
http://mcej.modares.ac.ir/article-16-5590-en.pdf
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
11
1
2011
4
1
Investigation of Park-Ang Damage Index Model
for Flexural Behavior of Reinforced Concrete Columns
0
0
FA
R
Rajabi
N
M
Barghi
Y
Abstract:
Damage assessment of bearing members before rehabilitation is necessary. If the damage state
of a member is expressed by a number called "damage index". One of the most popular
damage indexes for reinforced concrete (RC) members is Park-Ang Damage Index model.
This model has been established based on the experimental results of RC beams and columns
with different modes of damage. It has considerable uncertainty based on its authors’ remarks.
In this study, the precision of Park-Ang model for RC columns was improved by using some
experimental results from the Peer's (Pacific Earthquake Engineering Research) data bank.
The proposed model focuses on RC columns with specific sections and collapse modes.
Damage index,reinforced concrete columns,Park-Ang model,Strengthening
http://mcej.modares.ac.ir/article-16-5024-en.html
http://mcej.modares.ac.ir/article-16-5024-en.pdf
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
11
1
2011
4
1
Applying Time-to-Collision to Enhance the Coefficient of
Determination for GHR Car-Following Model in
Deceleration Mode
0
0
FA
S.S
alavi
Y
M
SAFFARZADEH
N
N
Nadimi
N
A.R
MAMDOOHI
N
Abstract:
Car-Following models are integral parts of capacity analysis, safety research, traffic
simulation, and developing advanced vehicle control systems. During the past six decades,
various car following models have been developed. GHR is the most well-known stimulus
based model, in which the stimulus is the relative velocity of vehicles. In this research, timeto-
collision (TTC), as the stimulus, is proposed as a substitute for relative velocity in the
GHR model. GHR model is calibrated based on the comprehensive and detailed data gathered
in the NGSIM project on I-80 freeway. The Results of GHR model calibration based on the
data obtained for the two stimuli indicated that coefficient of determination (R2) increased
from 0.233 in the base model to 0.638 in the proposed model. In all, the results indicated that
the application of TTC as the stimulus in the GHR model would improve the model's
outcome.
Time-to-collision indicator,Car-following model,NGSIM project,GHR model,Model calibration
http://mcej.modares.ac.ir/article-16-8753-en.html
http://mcej.modares.ac.ir/article-16-8753-en.pdf
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
11
1
2011
4
1
Applicability of Particle-Matrix Model for
Determination of Proportions of Lightweight Concrete
Aggregates\' Contained LECA
0
0
FA
amir maziar
raees ghasemi
Y
T
parhizkar
N
H
family
N
Abstract
In general, methods of lightweight aggregate concrete mix design are not much different with
the ordinary concrete mix designs, except that in LWAC, volumetric method must be used for
determining the amount of aggregates (normal and lightweight). In some countries, the same
mix design of conventional concrete (normal weight) is also used for this purpose. Due to the
specific restrictions of these methods, it is difficult to use them in certain cases where
concrete slump is specified, or high strength concrete is needed.
In this paper, a new method for the mix design of lightweight aggregate concrete has been
proposed using a type of artificial lightweight aggregate (expanded clay, Leca). This approach
is based on two-phased model (particle and matrix), and has better performance compared to
other methods, due to the possibility of considering the properties of cement paste and particle
in terms of access to consistency (slump) and the required strength of the concrete made. Also
in this method, the percentage composition of normal and lightweight aggregates is chosen to
achieve minimum space (porosity), so, the minimum amount of cement paste will be used to
achieve the above requirements, and the economic saving.
lightweight aggregate concrete,Expanded clay,Lightweight aggregate,Flow
cyl,Cement paste
http://mcej.modares.ac.ir/article-16-2754-en.html
http://mcej.modares.ac.ir/article-16-2754-en.pdf
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
11
1
2011
4
1
Influence of Cement Content Increase on
Chloride Diffusion and Microstructure of Concretes
Containing Nano-Sio2
0
0
FA
m
Khanzadi1
Y
G
Khazaeni
N
H
Sepehri Kahrizi
N
Abstract:
The influence of cement content increase on corrosion resistant behavior in concretes
containing nano-SiO2 was experimentally studied. For comparison, the chloride diffusion of
plain concrete and the concrete containing nano-SiO2 was also experimentally studied. The
test results indicated that the corrosion resistance of concretes containing nano-particles is
significantly improved. However, the index of diffusion chloride ion in the concretes
containing nano-SiO2 is directly related to cement content in the mix. The SEM oservations
revealed that the microstructure of concrete with nano-SiO2 is more uniform and compact
than that of normal concrete, but higher pore size distribution was observed when cement
content is increased, which in turn leads to the increase in the diffusion of choloride ion.
Nano concrete,Nano-SiO2,corrosion,Chloride diffusion,Microstructure
http://mcej.modares.ac.ir/article-16-7061-en.html
http://mcej.modares.ac.ir/article-16-7061-en.pdf