Eect of Anti-Vortex Plates on Critical Submergence at a Vertical Intake
S.M.
Borghei
Department of Civil Engineering,Sharif University of Technology
author
A.R.
KABIRI-SAMANI
Department of Civil Engineering,Isfahan University of Technology
author
text
article
2010
eng
One of the sources of disturbance at intakes is the occurrence of free-surface vortices with
an air core. The most common solution for avoiding air-entrainment is the use of anti-vortex devices
and, especially, plates for large pipe or shaft intakes. If plates are used, then, the geometry and position
of them should be studied experimentally. Since only general guidance for use of plates is available, a
study for the more precise placement of plates is needed. Hence, a comprehensive set of experiments have
been carried out using rectangular plates with dierent dimensions and at various positions with respect
to the vertical outlet pipe intakes and two dierent pipe diameters (D = 75 and 100 mm). The results
of critical submergence with respect to the dimensions and positions of the plates are presented as graphs
and equations. Thus, design guides and recommendations are provided.
Scientia Iranica
Sharif University of Technology
1026-3098
17
v.
2
no.
2010
http://scientiairanica.sharif.edu/article_3123_fdcf929fbc9aec7263c0182a79617e40.pdf
Pseudo-Dynamic Active Earth Pressure Analysis of Inclined Retaining Walls Using Horizontal Slices Method
A.
Ghanbari
Department of Engineering,Tarbiat Modares University
author
M
Ahmadabadi
Department of Engineering,Tarbiat Modares University
author
text
article
2010
eng
Retaining walls may be constructed with an inclination angle of less than 90from the
horizontal axis. In the present study, using the horizontal slices method and limit equilibrium principles,
in addition to assuming variation of the seismic coecient with height, a new formulation is proposed
to calculate the active seismic pressure on retaining walls. The general arrangement of the proposed
pseudo-dynamic formulation allows analysis of inclined or vertical retaining walls in frictional, cohesive
and cohesive-frictional soils. Results from the proposed method were compared with those of previous
researchers under similar conditions and showed a negligible dierence. The horizontal slices method was
able to assess an inclined wall, determine the active earth pressure distribution at dierent points along
the wall height and consider the angle of failure wedge as a variable in the time domain. The ndings show
that despite the accepted assumptions for conventional vertical walls the distribution of earth pressure on
an inclined wall follows a non-linear pattern at each moment.
Scientia Iranica
Sharif University of Technology
1026-3098
17
v.
2
no.
2010
http://scientiairanica.sharif.edu/article_3124_5535e8b191f3aa8501e816341011ff5b.pdf
Analytical Approach for Flow over an Oblique Weir
A.R.
KABIRI-SAMANI
Department of Civil Engineering,Isfahan University of Technology
author
text
article
2010
eng
Flow discharge over an oblique weir is greater than that over a straight or plain weir for
the same water head due to its extra length with respect to the channel width or fully extended plain weir.
In this study, a new theoretical approach is used for the hydraulics of oblique weirs. The main objective
is to investigate the eect of dierent hydraulic and geometric properties of the
ow and the weir on
the
ow de
ection angle and discharge coecients for free and submerged
ow over oblique weirs. This
approach is based on energy, momentum and continuity equations. For improving the performance of this
kind of weir, one approach is to increase the
ow de
ection until it is perpendicular to the oblique weir
for maximum use of the weir length. The submerged guide vanes have also been used and investigated
theoretically. The data for calibration of the models are taken from Borghei et al.(2003). It is shown that
by employing guide vanes, for some cases, the discharge coecient can be increased up to 33%. Finally,
new relations were developed for practical purposes.
Scientia Iranica
Sharif University of Technology
1026-3098
17
v.
2
no.
2010
http://scientiairanica.sharif.edu/article_3125_6bef402f9d8aa4dbdd2d3cbdb5e3bf9c.pdf
Rotation as a General Operation for Conguration Processing
A.
Kaveh
Department of Civil Engineering,Iran University of Science and Technology
author
X.
Jia
School of Material Science,West Virginia University
author
Q.
Weng
Department of Geomatics Engineering,Carleton University
author
text
article
2010
eng
In this paper, a graph theoretical method is used to introduce three basic operations of
conguration processing; rotation, translation and re
ection. The relationships between translation and
rotation, and re
ection and rotation, are established. Examples are then constructed using three dierent
procedures of conguration processing. From the comparison and discussion of the results, it is concluded
that rotation can be considered as a general operation of conguration processing.
Scientia Iranica
Sharif University of Technology
1026-3098
17
v.
2
no.
2010
http://scientiairanica.sharif.edu/article_3126_56d948a19eaecc278b6ee78beaca8c56.pdf
Modeling of Moving Boundaries in Large Plasticity Deformations via an Enriched Arbitrary Lagrangian-Eulerian FE Method
A.R.
Khoei
Department of Civil Engineering,Sharif University of Technology
author
M.
Anahid
Department of Civil Engineering,Sharif University of Technology
author
text
article
2010
eng
In this paper, a new computational technique is presented for the modeling of moving
boundaries in large plastic deformations based on an enriched arbitrary Lagrangian-Eulerian nite element
method. An Arbitrary Lagrangian-Eulerian (ALE) technique is employed to capture the advantages of
both Lagrangian and Eulerian methods and alleviate the drawbacks of mesh distortion in Lagrangian
formulation. An enriched nite element method is implemented based on the extended FEM technique
to capture the arbitrary interfaces independent of element boundaries. The process is accomplished by
performing a splitting operator to separate the material (Lagrangian) phase from the convective (Eulerian)
phase, and partitioning the Lagrangian and relocated meshes with some sub-quadrilaterals whose Gauss
points are used for integration of the domain of elements. In order to demonstrate the eciency of
the enriched ALE nite element model in large deformations, several numerical examples including the
coining problem with horizontal and vertical moving boundaries and a tensile plate with a moving interface
are presented and the results are compared with those of the standard nite element and extended nite
element methods.
Scientia Iranica
Sharif University of Technology
1026-3098
17
v.
2
no.
2010
http://scientiairanica.sharif.edu/article_3127_29ef9b19888cd55d6987c9c80d866716.pdf
Adaptive Behavior of Double Concave Friction Pendulum Bearing and its Advantages over Friction Pendulum Systems
M.
Malekzadeh
Department of Civil Engineering,Amirkabir University of Technology
author
T.
Taghikhany
Department of Civil Engineering,Amirkabir University of Technology
author
text
article
2010
eng
Double Concave Friction Pendulum (DCFP) bearing is a new generation of friction isolator
that contains two separate concave sliding surfaces with dierent properties. Accommodating enhanced
performance, compared to the Friction Pendulum System (FPS), is one of the most important benets
of DCFP. Herein, the seismic behavior of structures isolated by DCFP bearings is compared with the
response of the same buildings using the FPS bearing. Accordingly, a series of nonlinear dynamic
analyses are carried out under ensembles of ground motions at three dierent hazard levels (SLE, DBE and
MCE). Moreover, the adaptive behavior of DCFP and its advantages in protecting secondary systems is
investigated. The probability of exceedance curves of peak roof acceleration, peak inter-story drift and peak
isolator displacement is compared for two types of isolation system. The result supports the advantages
of DCFP isolation systems.
Scientia Iranica
Sharif University of Technology
1026-3098
17
v.
2
no.
2010
http://scientiairanica.sharif.edu/article_3128_5d1d140c4d88ee254423be4ff7df1150.pdf
Evaluation of Energy-Based Modal Pushover Analysis in Reinforced Concrete Frames with Elevation Irregularity
M.
Mofid
Department of Civil Engineering,Sharif University of Technology
author
M. J.
Hashemi
Department of Civil Engineering,Sharif University of Technology
author
text
article
2010
eng
In nonlinear static (pushover) methods of analysis as an alternative to time history
analysis, the capacity curve of the structure is established with respect to the roof displacement.
Disproportionate increases in the roof displacement and even outright reversals of the higher modes can
distort the capacity curve of the equivalent single degree of freedom system in these kinds of method,
including MPA. To overcome this problem, recently, Energy-Based" the Modal Pushover Analysis
(Energy-Based MPA) method has been introduced. In this method, the absorbed energy and/or the external
work in the pushover analysis is considered. Accordingly, the assessment of the Energy-Based MPA
method is important in the seismic analysis of asymmetrical and tall buildings. In this paper, the seismic
demands of concrete structures with irregularity in elevation are determined, using Energy-Based MPA.
For assessment of the presented technique, the results are compared with those from the Non-Linear
Time History Analysis (NL-THA). Seven examples including a 2-D simulation of a 12-story building are
modeled, using the Opensees Code. For each case, dierent types of irregularity, such as mass, geometry
and variations due to the dierence in elevation are considered. Story-drifts and
oor-displacements are
used as the main parameters for assessment of the results. Based on a study of the structural performance
of the models, it has been made clear that dierent types of the above-mentioned irregularity in elevation
do not have any signicant eect on the Energy-Based MPA method. Consequently, this method can be
considered as an accurate alternative technique for NL-THA, to fairly estimate the seismic demands of
structures.
Scientia Iranica
Sharif University of Technology
1026-3098
17
v.
2
no.
2010
http://scientiairanica.sharif.edu/article_3129_f975971c8b804a644a54659966c9b92c.pdf
Simple Assessment Method to Estimate the Remaining Moment Capacity of Corroded I-Beam Sections
R.
Rahgozar
Department of Civil Engineering,Razi Metallurgical Research Center
author
Y.
Sharifi
Department of Civil Engineering,Shahid Bahonar University of Kerman
author
text
article
2010
eng
Corrosion of steel structures is a serious problem throughout the world. The most
signicant consequence of corrosion is reduction of the section size. This, in turn, leads to a reduction in
the carrying capacity and structural safety. The analysis of existing structures may dier from the analysis
of structures under design, especially if there is damage by corrosion. Common examples of corrosion
that have been found in the petro-chemical industry include the loss of sections in
anges and holes in the
web. As there is no clear provision of recommendations for such cases in the present codes, there is a need
for simple assessment methods to deal with them eectively. The overall aim of this paper is to develop
a simple method which can be used to make reliable estimates of the remaining moment capacity, using
thickness loss information provided by visual inspection or measurements. The results of this study can
be used for calculating the remaining service life, such as the moment capacity of deteriorated I-beams.
Scientia Iranica
Sharif University of Technology
1026-3098
17
v.
2
no.
2010
http://scientiairanica.sharif.edu/article_3130_3c5cea3860cf39c407f92ecc3030d3d2.pdf