Tarbiat Modares University
Modares Civil Engineering journal
10
1
2010
6
1
Creep of Rock Fill Material in Large Scale
Odometer with Considering Particle Breakage in
Loss Angeles Test
0
0
FA
Ali
Komakpanah1
Mohammad
AghaMajidi2
Abstract
Creep is a time-dependent deformation of soil under constant effective stresses. For investigation on the creep of
rock fill materials, 3 samples from 3 dams of Iran that are already under construction were selected. Normal
effective stresses were applied on the specimens with a large-scale odometer apparatus that is specially designed
for the research. Comparison of creep rate, amount of particle breakage and results of Los Angeles test shows a
relationship between these three parameters. Consequently Los Angeles test that is a simple and accessible test,
can give a prediction and estimation of behavior and properties of rock fill materials. Based on the test results, an
approximate relationship could be found between creep, particle breakage and Los Angeles test results.
Tarbiat Modares University
Modares Civil Engineering journal
10
1
2010
6
1
Analytical Behavior of Brick-Infilled Concrete
Frames Strengthen by FRP
0
0
FA
F.
Nateghi.
A.
Dehghani
Abstract
Due to various deficiencies, inadequate lateral stiffness, weak design and weak construction, many reinforced
concrete buildings are highly damaged during the major earthquakes. One way to retrofit these buildings is to
improve the behavior and to prevent the total collapse of the reinforce masonry infilled walls in order to make
them behave such as structural walls with composite materials.
In this study, the concept of equivalent strut is investigated by finite element modeling and behavior of the
compression strut and tension tie is presented to model unretrofit and retrofit masonry infilled walls. Analytical
pushover results show great accordance with experimental results.
Tarbiat Modares University
Modares Civil Engineering journal
10
1
2010
6
1
3D Numerical Analysis of Bed Topography in 180
Degree Channel Bend
0
0
FA
A. R.
Mansoori
S. A. A.
Salehi Neyshabouri
A.
Honarbakhsh
Abstract
The complex three-dimensional flow characteristics in river bends necessitates the use of a three-dimensional
numerical model. The numerical model used in this paper is called SSIIM (Sediment Simulation In Intakes with
Multiblock option).The 3D model already has showed satisfactory results in related applications. In this study,
SSIIM is applied to study the variation of channel bed under steady flows in a 180 mild curved open-channel
with sandy bed. Bed roughness was calibrated to ks 4.5 d90 6.25d50 . Comparison of results showed good
agreement between the computed and measured bed topography. The model simulated both the point bars near
the inner bank and the scour holes near the outer bank. In addition, the positions of these phenomena are in fair
agreement with the measured data. Numerical results show some dependencies on the grid size. In addition,
deviations of model from the experimental data as well as uncertainties in numerical modeling are discussed.
Tarbiat Modares University
Modares Civil Engineering journal
10
1
2010
6
1
‹‹Research Note››
Determination of Strengths of Construction
Materials Applying the in Situ Twist off Method
0
0
FA
M.
Naderi
S.
Maadani
Abstract
Since for some reasons such as studying the behaviour of old construction materials and proper replacement of
the deteriorated sections, adequate knowledge about the true in situ strength of the construction materials has
become a necessity, many attempts have been made to invent and develop new in situ methods in recent years.
Most of these methods measure the in situ strengths of materials indirectly by measuring properties other than
the strength and relating them to strength by some defined relationships. This paper introduces an innovative
partially destructive method, called “Twist-off”, for the assessment of in situ concrete, mortar, and masonry
strengths of materials used in buildings and structures. In addition to the laboratory results, the results of the
successful application of this method on site are also presented in this paper. Based on the results obtained, the
use of this new in situ method with its advantages of simplicity (no need for experts), low expense, cheap and
simple apparatus, little damage to the surface area, and high accuracy is strongly recommended for the
determination of in situ strengths of construction materials (concrete, mortar, and masonry) used in different
buildings and structures.
Tarbiat Modares University
Modares Civil Engineering journal
10
1
2010
6
1
Research Note››
Determination of Active Earth Pressure for
Reinforced Retaining Walls in c-) Soils
0
0
FA
A.
Ghanbari
S. 2
Shekarian
Abstract
The prediction of active earth pressures is essential to the design of retaining walls in case of reinforced and
unreinforced soils. In this study, a new analytical method is presented to determine the coefficient of earth
pressure. The horizontal slice method is used to compute the active earth pressure behind a rigid retaining wall in
consideration of the granular soils. To verify the correctness of the suggested method, its results were compared
with those of existing studies. Results show that the developed formulation for non-cohesive soils has a good
agreement with the results of software simulations. Also, a new formulation for cohesive soils was presented and
its results were compared with the Rankine method. The effect of parameters such as the cohesion of soil mass,
the angle of internal friction and the angle of wall friction were assessed. In all cases, it is shown that the
horizontal slice method has good capability to predict the active earth pressure.
Tarbiat Modares University
Modares Civil Engineering journal
10
1
2010
6
1
Effect of Random Initial Crookedness of Members
on Reliability of Steel Frames
0
0
FA
M. A.
Lotfollahi-Yaghin
M.
Negin
Abstract
In this paper the effect of two types of common initial geometric imperfections on the reliability of steel frames
is investigated. These imperfections are the coordinates of connection nodes and crookedness of members. Most
finite element reliability analyses in past literature neglect this source of uncertainty. For this purpose static nonlinear
pushover structural analysis is used from which reliabilities are estimated based on FORM and Monte
Carlo sampling methods. Furthermore to investigate the importance of uncertain parameters, reliability
sensitivity analysis is performed by use of the direct differentiation method which has been implemented in the
object oriented software framework Open Sees. It is demonstrated that some of these geometric imperfections
have significant influence on reliability assessment of steel frames.
Tarbiat Modares University
Modares Civil Engineering journal
10
1
2010
6
1
Shear Strength Degradation of Circle Reinforced
Concrete Columns
0
0
FA
M.
Barghi1*
A
Lagzian
Abstract
Earthquake reconnaissance has identified shear failure of reinforced concrete columns as a primary cause of
failure of older existing reinforced concrete columns. Satisfactory seismic response of reinforced concrete
columns requires that brittle failure modes be inhibited. In this research, different factors which affect the shear
failure of columns have been studied, and then by using the results of 103 cyclic loading tests on columns, a new
model for estimation of shear strength degradation under cyclic loading has been developed. The proposed
model can be used to estimate shear strength degradation of reinforced concrete columns with shear, shear
flexural and flexural failure separately. Uncertainty of the results of this model is little because the study has
been concentrated on the three independent groups of the columns with one specified failure mode. The results
of cyclic loading tests used in this study have been taken from the PEER ( Pacific Earthquake Engineering
Research Center) database.
Tarbiat Modares University
Modares Civil Engineering journal
10
1
2010
6
1
Evaluation of Genetic Algorithms for Optimal
Design of Cascade Stilling Basins
0
0
FA
M.H
.Afshar
M.
Daraeikhah
Abstracts
This paper presents how the genetic algorithm (GA) can be applied to design of cascade stilling basins. Genetic
Algorithm is adaptive method, which can be used to solve search and optimization problems over a period of
generations, based upon the principles of natural selection and survival of the fittest ones. The objective of this
research is to minimize total cost of construction effectively which is a function of height of falls and length of
stilling basins, while fulfilling the hydraulic and topographical criteria. The efficiency of GA discussed here has
been tested for a benchmark example and the result for this algorithm is compared with the other method
introduced by Vittal and Porey. The results clearly reveal superiority of the GA algorithm
Tarbiat Modares University
Modares Civil Engineering journal
10
1
2010
6
1
Evaluation and Comparison of Real, Artificial and
Pulse-Like Models Near-Fault Earthquakes
0
0
FA
H.
SHAKIB
S.SH
Hashemi 2*
Abstract
Ground motions close to a ruptured fault can be significantly different from those further away from the seismic
source. In the other hand there are a few real records which include the characteristic of near-fault records.
Hence, simulation of these records is useful in order to study their effects on the behavior of structures which has
been built near the faults. Tehran is a city in the neighboring of several active faults but there aren’t any nearfault
real records in this place. In this paper, according to mechanism and situation of North Tehran Fault (NTF),
seven near-fault real records with forward directivity have been selected and by using selected records a pulselike
decaying sinusoidal model has been proposed as NTF simulated near-fault records. Finite fault method with
specific considerations has been used as a suitable and reliable method for creating near-fault artificial record
and the artificial records for NTF has been generated at 2, 5 and 10 km distances. Finally the results for real and
artificial records and also the pulse-like model have been compared together.
Tarbiat Modares University
Modares Civil Engineering journal
10
1
2010
6
1
Seismic Evaluation of Concrete Moment Frames
with Low Height Beams
0
0
FA
A.
KHEIRODIN
S.
FAMILY
Abstract
Low height beams in concrete moment frames, decrease the ability of beams in controlling lateral displacement
of buildings. Because of that, in the sixth subject from Iranian Regulations of Buildings and its following, in the
3rd edition of Standard 2800, the height of buildings with low height beams has been limited to 3 floors or 10
meters.
According to that, in this study, concrete buildings with different amount of stories and moment frames, with
medium ductility and the height of beams in 30 centimeters, have been analyzed (with linear equivalent static
and spectral dynamic analysis Methods)and designed on the basis of seismic principles in the 2nd and 3rd
edition of Standard 2800. Finally, studies continued with nonlinear static analysis and the performance point of
structures determined (with capacity spectrum and displacement coefficient methods) in 4 levels of different
seismic risks. Studies show that only one or two story buildings that designed with 2nd edition of Standard 2800
have enough safety in design base earthquake level (DBE) and also higher buildings, should go under
rehabilitation.