Tarbiat Modares University
Modares Civil Engineering journal
10
2
2010
6
1
Linear Homogenization of Brick
Masonry Stuctures
0
0
FA
Iman
Salehi D.
Masoud
Soltani M.
Abaas Ali
Tasnimi
bstract
The average behavior of composite material like masonry can be described in terms
of the relation average stresses and strains (macro model) if the material is assumed to
be homogeneous. The average stress-strain relationship can be determined generally
using two approaches. A possible approach is experimental investigation from the
available experimental data. Another approach, adopted in this resedrch, is to develop
a linear homogenization technique, which describes the behavior of the masonry from
the geometry and the behavior of the representative basic cell. In this research, the
elastic properties of a basic cell in masonry with a periodic arrangement of blocks
were obtained based on a local stress field approach (micro-modeling of the mortar
and blocks).Two different methods were used for computing the equivalent
orthotropic elastic properties of the basic cell as a continuum, the approximate energy
method (a closed form solution) and the finite element based method. The finite
element method was used to approximately find the orthotropic yield curves of the
homogenous element. The similarity of the general behavior of these gied curves with
regard to the experimental facts was considerable.
Tarbiat Modares University
Modares Civil Engineering journal
10
2
2010
6
1
Stydying the effect of weight on Time- Dependent
Behavior of Gotvand dam Foundation
0
0
FA
H.D.N.,
Mahmoodi1
M.
Farogh Hossieini
M.
Ahmadi
m.s
.Jalali
Abstract
Gotvand rock fill dam is being constrcted on Karun river located in Khoozestan province south of
Iran. The dam is foung on Aghagari formation which is consisted of mudstone and sandstone layers.
These layers are intermittent of weak to medium strength with uniaxial compressive strength 15 and
25 MPa respectibely. Some regional factors as continuous unloading caused by river flood washed off
and horizontal tectonic loading have created a local anticline in the foundation of dam. According to
previous analyses, results have shown that this folding will continue over the time. In this research
effect of the dam weight on time d- dependant deformation of the dam foundation has been studied.
Ration of horizontal to vertical stresses (K) was estimated to be 0.4 to 0.7 by in-situ tests, so dam site
numerical models were executed (numerical analysis wity the FLAC3D code) with K equal to 0.4,0.55
and 0.7. First, the models were executed statically. Maximun settlement of foundation due to the dam
weight was estimated a bout 37cm. Ihen for time dependent analysis, the behavior of rocks is assumed
to obeay Maxwell creep viscousplastic rheological model and the models were executed for 100 years
equal to the dam life time. The results of numerical analysis show that upward deformations of the
foundation with K=0.55 and 0.7 is continuously, even in the central region of dam where the dam
weight is maximum. But in the model with K=0.4, in the first 60 years after the construction, creep
deformation are downward and after this time, directions of deformation were changed to upward.
Tarbiat Modares University
Modares Civil Engineering journal
10
2
2010
6
1
Evaluation of Stripping in Asphalt Pavements Using
Abrasion Test
0
0
FA
Amir
Kavussi1
Ali
Abdi
Abstract
The main purpose of this research is studying stripping of asphalt mixtures. Key factors were
the aggregate properties and the suitable methods to control and assess the stripping distress in
laboratory conditions. Our case study was the "Zanjan-Qazvin" freeway in which this distress
is manifested extensively. The aggregates for the tests were selected from the sections in
which stripping were more serius. stripping was found to be caused by excess values of
siliceous minerals. This resul were obtained using XRF & XRD analyses. Primary estimation
of stripping was determined using boiling test over the loose mix specimens. Specimens were
tested under theWTAT. Hydrated lime was utilized as the antistripping agent.
It is concluded that if hydrated lime is utilized as an additives, not only stripping is reduced
but also the stability and durability of the asphalt pavement is increased. The presented
approach ultimately resulted in improving mix properties.
Tarbiat Modares University
Modares Civil Engineering journal
10
2
2010
6
1
Study of Seismic Behavior of Buckling Restrained
Braced Frames
0
0
FA
A.H.
Salmanpour
F.
Arbabi
Abstract
This work aimed to identify the seismic behavior of buckling restrained braced frames
(BRBFs). A six-story frame with buckling restrained braces was analyzed at different
hazard levels. After the discussion of some aspects of BRBs, the results of detailed
nonlinear dynamic analyses are examined to characterize the seismic behavior of the
model building. Also the effect of near-field ground motions on the behavior of the
model was studied. The results indicate that BRBFs behave quite well under seismic loads.
However, there are some concerns about the performance of this system under more
frequent lower intensity ground motions.
Tarbiat Modares University
Modares Civil Engineering journal
10
2
2010
6
1
Comparison of Accordion Metallic Dampers
with Filled Accordion Metallic Dampers Using
Polymeric Foam under Axial Cyclic Loading
0
0
FA
E.
Izadi Zaman Abadi1
F.
.Nateghi-Alahi
M.
Motamedi
During the last decades, many researches have been carried out on development of
supplemental passive energy absorption devices especially hysteretic metallic
dampers and different types of them with different capacities and potentials have
been developed. The idea of buckling of thin-walled tubes and the use of this
property was led to develop an accordion metallic damper (AMD) [Motamedi,
Nateghi-Alahi-2007]. This damper utilizes the capability of accordion thin-walled
tube for excitation of axisymmetric concertina buckling mode as a damping
mechanism which in turn increases the amount of dissipated energy.
In this paper filled accordion metallic damper (FAMD) is suggested and
analytically and experimentally the behavior of AMD's and FAMD's under axial
cyclic loading are investigated and compared. For this purpose, Firstly analytical
studies based on Finite element method and nonlinear dynamic analysis was
performed on FAMD's for the determination of the approximate preliminary
specifications of different polymers for potential use. After specifying the
preliminary material properties, 4 specimens include 2 FAMD's filled by polymeric
foam and 2 AMD's were subjected to dynamic tension and compression actuator
and the effect of filling AMD's by this polymeric foam on the some of important
specifications of damper studied and try to use this method for improving and
developing of AMD's. Based on the results obtained using the appropriate filling
inside the AMD's is a suitable technique for the purpose of improvement the some
of important specifications such as the number of cycles before failure, amount of
dissipated energy and plastic capacity. The effect of interaction between foam and
accordion thin walled tubes play an important role for this purpose especially in
low capacity AMD's.
Tarbiat Modares University
Modares Civil Engineering journal
10
2
2010
6
1
Expermental Investigation on the Effect of Relative
Channel Radius on bed scour in a 90 degree
0
0
FA
S.K.
Maosavi,
M.
Ghodsian,
Abstract
The problem of scour and variations of bed topography, which is influenced by different
parameters is very important in river engineering. In order to study the influence of
discharge, relative flow depth and relative channel radius on dimensions of scour hole,
experiments were conducted. The results are given in this paper.
Tarbiat Modares University
Modares Civil Engineering journal
10
2
2010
6
1
Numerical Analysis of Ground Reinforced with a
Stone Column Group
0
0
FA
Abbas
Soroush
Saeedeh
Tabarsaz
154
Abstract
Numerical Analysis of Ground Reinforced with a
Stone Column Group
Saeedeh Tabarsaz and Abbas Soroush
School of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran,
Iran
soroush@aut.ac.ir
Abstract
This paper presents the numerical analyses of a group of stone columns penetrated in
a 10 m deep soft clay stratum. A rigid raft transfers the super-structure's loading to
the stone columns and the parent ground. The columns group comprises of five
columns with a symmetric configuration. The numerical analyses are performed on a
plane strain idealization of the structure, using an elasto plastic constitutive behavior
for both the stone columns and the soft clay layer. Additional numerical analyses
with different range of parameter, like number of columns, space of columns,
column’s length, foundation’s size, Poison ratio of soil and stone columns’ material
and modulus of elasticity ratio of the stone columns’ material were conducted. The
results of analyses showed that lateral displacements (bulging) occur in the upper
parts of the columns (between 2D and 4D from the top; D is the column diameter)
and the lateral displacements are comparatively higher for the side columns. The
major result of the analyses is that for a group of stone columns supporting a rigid
raft under spread loading, the lengths of the stone columns could be designed
unequal, i.e., inside the columns can be shorter, without significantly increasing of
the settlements of the column group.
Tarbiat Modares University
Modares Civil Engineering journal
10
2
2010
6
1
Geo-Environmental Behaviour of Montmorillonite
Treated with Cations in Retention of Pb
0
0
FA
V.R.
Ouhadi1
S. I.
Choobchian
The behauiours of clay minerals and the extent of clay-heavy metals interactions are
functions of CEC and the exposed SSA of the clay minerals. The type and the
quantity of double layer cations have an essential impact on this process. This work
aimed to investigate the behaviour of Na-montmorillonite and Ca-montmorillonite in
interaction with Pb as a heavy metal ion. The results showed that although the
buffering capacity pattern of montmorillonite and different concentrations of NaCl is
relatively similar, the contaminant retention property of montmorillonite is a function
of the quantity of sodium ions with which the soil is treated. In Ca-montmorillonite,
in spite of very small change in its buffering capacity in comparison with that of
montmorillonite, a noticeable change in contaminant retention was observed. This
emphasizes the limitation of buffering capacity experiment to determine the extent of
soil-contaminant interaction. On the other hand, retention experiment was able to
differentiate between the behaviour of these two samples. Finally, the results of the
interaction process of sodium- and calcium- montmorillonite with heavy metal
contaminant were compared using the XRD experiments.
Tarbiat Modares University
Modares Civil Engineering journal
10
2
2010
6
1
Retrofit of Typical Rigid Steel Connection
Using Reduced Beam Flange Section
0
0
FA
M.
Gerami
A.
Ghaznavi Oskuei
Abstract
The moment connections sustained by many steel buildings were damaged during the
recent earthquakes due to brittle fractures in the special moment resistant frames.
Previous studies showed that although the top beam flange resisted due to the interaction
of concrete slab, many damages are created because of weld cracking between the bottom
beam flange and the column flange. Different methods of retrofit and rehabilitation could
be used to prevent weld cracking and brittle fracture of the joints. The reduction of the
bottom flanges of steel beams near the beam-column joints in the special moment resistant
frames is currently an acceptable alteration of a connection because the top flange is
located in the concrete slab and removing of concrete slab has financial and technical
problems. RBS connection is one of the different kinds of Post-Northridge connections in
which by cutting some parts of the flange near the end of the beam (where the possibility
of making plastic hinges is high), the plastic hinge moves by the side of the column into
the area within the beam. By using this method, the connection is altered from the special
moment frame into a more ductile connection that has more ability to endure in plastic
rotation, and generally ductility increases. The ductility of the panel zone is one of the
parameters, which undoubtedly affects the manner of the yield of beams with RBS
connection. Our findings in this work showed that new method causes the beam plastic
rotation to increase by 30%. In addition, the applied force at the panel zone (according to
the capacity of panel zone) is decreased. When compared to the frames without cuts, these
reductions result in a 52% decrease in the plastic rotation of the panel zone, we also
investigated the amount of dissipated energy by beams in the conditions before and after
retrofitting. ANSYS software was used to study and analyze the non-linear behavior in the
area of connections.
Tarbiat Modares University
Modares Civil Engineering journal
10
2
2010
6
1
Introducing New Humped Slab Track
Superstructure for Obviating the Problems of
0
0
FA
J. A.
Zakeri
M.
Esmaieli
M.
Fathali
Abstract
The movement of sand dunes in desert railways has various harmful effects, which reduces
operational safety and speed and causes great maintenance and renewal costs. To
encounter the movement of sand dunes, different traditional and modern methods are
implemented, none of which covers completely the problems, especially the ballast
solidification and line closuring as the major ones. In this paper, a new system called
"humped slab track" is introduced, in which the ballast solidification problem is obviated
with the application of ballast-less superstructure. The problem of track closuring with
sand dunes is also mitigated by means of elevating the rails higher, using uncases
reinforced concrete called "humps", and letting the sands traverse from the generated
superstructure space between the humps and beneath the rails, just like fluid. To show the
efficiency of the proposed system, the simulation of sand movements from the track
section was performed using two-phase analysis in the FLUENT finite element software.