Showing 27 results for Shah
Farhoudi J., Shah Alami H.,
Volume 3, Issue 1 (March 2005)
Abstract
The rectangular broad crested weirs are widely used to measure the water dischargewhich is one of the most popular tools in the irrigation canals particularly, in developingcountries.The present article is trying to demonstrate the results of an experimental work carriedout on rectangular broad crested weir with sloped upstream face to investigate the effect ofupstream slope on discharge efficiency. The upstream slope was varying from 90 to 23 degreeswhile incoming discharge was ranging from 14 to 75 lit/ sec. The experiments were conducted in aflume with a weir of fixed height under the normal downstream water depth .It is revealed that theslope of upstream face in rectangular broad crested weir would smoothen the flow profile havingthe critical depth on the weir crest adjacent and upstream of downstream edge of the weir . Theresults also lead to a novel achievement showing that the weir discharge efficiency is dependenton the slope of upstream face of the weir. As the slope of upstream face of the rectangular broadcrested weir is decreasing from 90 to 23 the weir discharge efficiency is increasing and reachingto its maximum through a parabola function at slope angle of 25 degrees(i.e. 1:2.15). Theinvestigation also showed that the depth of flow over the weir crest, the specific energy head ofthe approaching flow relative to chanel bed and the critical depth would be a pertinent similarityscales to asses the flow behavior over different sloped rectangular broad crested weirs betweenmodel and prototype. However, some broad investigation is recommended to endorse theachievements.
Kaveh A., Shahrouzi M.,
Volume 3, Issue 3 (September & December 2005)
Abstract
Genetic Algorithm is known as a generalized method of stochastic search and has been successfully applied to various types of optimization problems. By GA s it is expected to improve the solution at the expense of additional computational effort. One of the key points which controls the accuracy and convergence rate of such a process is the selected method of coding/decoding of the original problem variables and the discrete feasibility space to be searched by GAS. In this paper, a direct index coding (DIC) is developed and utilized for the discrete sizing optimization of structures. The GA operators are specialized and adopted for this kind of encoded chromosomes and are compared to those of traditional GA S. The well-known lO-bar truss example from literature is treated here as a comparison benchmark, and the outstanding computational efficiency and stability of the proposed method is illustrated. The application of the proposed encoding method is not limited to truss structures and can also be directly applied to frame sizing problems.
A. Kaveh, H.a. Rahimi Bondarabady, L. Shahryari,
Volume 4, Issue 3 (September 2006)
Abstract
The main aim of this paper is to extend the recently developed methods for calculating the
buckling loads of planar symmetric frames to include the effect of semi-rigidity of the joints. This is
achieved by decomposing a symmetric model into two submodels and then healing them in such a
manner that the :::union::: of the eigenvalues of the healed submodels result in the eigenvalues of the
entire model. Thus the critical load of the frame is obtained using the eigenvalues of its submodels.
A.a. Khosroshahi, S.a. Sadrnejad,
Volume 5, Issue 1 (March 2007)
Abstract
A framework for development of constitutive models including damage progress, based on
semi-micromechanical aspects of plasticity is proposed for concrete. The model uses sub-loading
surface with multilaminate framework to provide kinematics and isotropic hardening/softening in
the ascending/descending branches of loading and can be able to keep stress/stain paths histories
for each plane separately. State of stresses on planes is divided to four basic stress patterns i.e. pure
compression, increasing compression-and shear, decreasing compression-shear and tension-shear
and used in derivation of plasticity equations. Under this kind of categorized form the model is
capable of predicting behavior of concrete under any stress/strain path such as uniaxial, biaxial and
triaxial in the monotonic and cyclic loading, Also this model is capable of predicting the effects of
principal stress/strain axes rotations and consequent plastic flow and has the potential to simulate
the behavior of material with anisotropy, fabric pattern, slip/weak planes and crack
opening/closing. The material parameters of model are calibrated by optimum fitting of the basic
test data available in the literature. The model results under both monotonic and cyclic loading
have been compared with experimental results to show capability of model.
M. Heidarzadeh, M. Dolatshahi Pirooz, N. Hadjizadeh Zaker, M. Mokhtari,
Volume 5, Issue 4 (December 2007)
Abstract
Makran Subduction Zone (MSZ) offshore of Iran and Pakistan is one of the most
tsunamigenic sources in the Indian Ocean. Historically, the MSZ has generated some tsunamigenic
earthquakes like that of 28 November 1945 with the death tool of more than 4000 people along the
coasts of Iran, Pakistan, India, and Oman. In this study, the tsunami hazard associated with the
MSZ is investigated. At first, a review of historical tsunamis in the Indian Ocean basin was
performed which reveals the Makran region has experienced al least 4 tsunamis including events of
326 BC, 1897, 1008, and 1945. Consequently, since the pattern and extent of vertical ground
deformation from an earthquake determines whether or not a tsunami is formed, a computer
program is developed to predict the seafloor deformation due to the earthquake occurrence in the
MSZ. The model was verified through run of it on some actual tsunamis so far occurred. Then, using
the data of the 1945 Makran tsunami, the seismic parameters of the MSZ were calibrated. Finally,
we used the developed computer program to calculate seafloor deformation at the location of
Makran subduction zone for several earthquake scenarios with moment magnitudes ranging
between 6.5 and 8.5. The results of this research show that the risk of tsunami generation from MSZ
can be classified into three main categories, as follows: (1) very little risk for tsunami generation
in the case of the occurrence of an earthquake having magnitude up to 7 (2) little to medium risk
for moment magnitudes ranging between 7 and 7.5 and (3) high risk for moment magnitude greater
than 7.5. At the end of the paper, modeling of tsunami propagation is performed for an earthquake
scenario with magnitude of 8 offshore Chabahar, in order to give preliminary information about
tsunami behavior in this region.
Habib Shahnazari, Hosein Salehzadeh, Amin Askarinejad,
Volume 6, Issue 1 (March 2008)
Abstract
Classical soil mechanics involves the study of fully saturated soils. However, many problems encountered in geotechnical engineering practice involve unsaturated soil, in which behavior is significantly different from classical saturated soil. Negative pore pressure and capillary forces develop a virtual cohesion between the grains of semi saturated soils. This kind of cohesion is dependent on different factors such as grain size, saturation degree, soil-water characteristic curve and relative density of the soil. In this research the virtual cohesion of fine silty sand with 5% water content and a saturation degree of 17% is estimated. A vertical slope is constructed and is accelerated in the geotechnical centrifuge until failure. During the test, the model was monitored by a wireless video camera, attached to the strong box. The cohesionless tested sand was unsaturated. Based on the scaling laws and considering parameters such as sample unit weight, failure acceleration and the sample dimensions, a slope stability analysis was performed, and the virtual cohesion generated in the sample was calculated. The factor of safety of the prototype modeled in the centrifuge is calculated either by Finite Element Method and Finite Difference Method by using the resulted virtual cohesion from physical modeling. Results of this research show the validity of physical modeling for calculating the virtual cohesion in unsaturated silty sand.
M.a. Khan, A. Usmani, S.s. Shah, H. Abbas,
Volume 6, Issue 2 (June 2008)
Abstract
In the present investigation, the cyclic load deformation behaviour of soil-fly ash layered system is
studied using different intensities of failure load (I = 25%, 50% and 75%) with varying number of cycles (N =
10, 50 and 100). An attempt has been made to establish the use of fly ash as a fill material for embankments of
Highways and Railways and to examine the effect of cyclic loading on the layered samples of soil and fly ash.
The number of cycles, confining pressures and the intensity of loads at which loading unloading has been
performed were varied. The resilient modulus, permanent strain and cyclic strength factor are evaluated from
the test results and compared to show their variation with varying stress levels. The nature of stress-strain
relationship is initially linear for low stress levels and then turns non-linear for high stress levels. The test
results reveal two types of failure mechanisms that demonstrate the dependency of consolidated undrained
shear strength tests of soil-fly ash matrix on the interface characteristics of the layered soils under cyclic
loading conditions. Data trends indicate greater stability of layered samples of soil-fly ash matrix in terms of
failure load (i) at higher number of loading-unloading cycles, performed at lower intensity of deviatoric stress,
and (ii) at lower number of cycles but at higher intensity of deviatoric stress.
Mahmoud Hassanlourad, Hosein Salehzadeh, Habib Shahnazari,
Volume 6, Issue 2 (June 2008)
Abstract
In this paper shear behavior of two calcareous sands having different physical properties are
investigated using drained and undrained triaxial tests. The investigated sands are obtained from two different
zones located in Persian Gulf, Kish Island and Tonbak region. Analysis based on energy aspects show that
friction angle in these soils, having crushable particles, is formed of three components: substantial internal
friction angle, dilation and particle breakage angle. Dilation component is available in the two investigated
sand. Particle breakage component is a function of grains hardness, structure and geometry shape. Particles
breakage decreases the volume of sample during drained tests and creates positive pore water pressure during
undrained tests. Two investigated sands show different amount of dilation and particle breakage under similar
conditions. Simultaneous dilation and particles crushing and different amount of them result in different shear
behavior of the two studied sands. Energy aspects are used to determine the effect of particle crushing on the
shear strength. There is a suitable compatibility between relative breakage of grains and consumed energy
ratio for particle breakage.
Kourosh Shahverdiani, Ali Reza Rahai, Faramarz Khoshnoudian,
Volume 6, Issue 2 (June 2008)
Abstract
Large capacity cylindrical tanks are used to store a variety of liquids. Their Satisfactory
performance during earthquake is crucial for modern facilities. In present paper, the behavior of cylindrical
concrete tanks under harmonic excitation is studied using the finite element method. Liquid sloshing, liquid
viscosity and wall flexibility are considered and additionally excitation frequency, liquid level and tank
geometry is investigated. The results show a value for wall thickness to tank diameter ratio which may be used
as a guide in the consideration of wall flexibility effects.
Shahram Feizee Masouleh, Kazem Fakharian,
Volume 6, Issue 3 (September 2008)
Abstract
A finite-difference based continuum numerical model is developed for the pile-soil dynamic response
during pile driving. The model is capable of simulating the wave propagation analysis along the pile shaft and
through the soil media. The pile-soil media, loading and boundary conditions are such that axisymmetric
assumption seems to be an optimized choice to substantially reduce the analysis time and effort. The
hydrostatic effect of water is also considered on the effective stresses throughout the soil media and at the pilesoil
interface. The developed model is used for signal matching analysis of a well-documented driven pile. The
results showed very good agreement with field measurements. It is found that the effect of radiation damping
significantly changes the pile-soil stiffness due to the hammer blow. The pile tip response shows substantial
increase in soil stiffness below and around the pile tip due to driving efforts.
Shahriar Afandizadeh, Morteza Araghi,
Volume 6, Issue 4 (December 2008)
Abstract
Shahriar Afandizadeh, Jalil Kianfar,
Volume 7, Issue 1 (March 2009)
Abstract
This paper presents a hybrid approach to developing a short-term traffic flow prediction model. In this
approach a primary model is synthesized based on Neural Networks and then the model structure is optimized through
Genetic Algorithm. The proposed approach is applied to a rural highway, Ghazvin-Rasht Road in Iran. The obtained
results are acceptable and indicate that the proposed approach can improve model accuracy while reducing model
structure complexity. Minimum achieved prediction r2 is 0.73 and number of connection links at least reduced 20%
as a result of optimization.
H. Shahnazari, M. Esmaeili, H. Hosseini Ranjbar,
Volume 8, Issue 2 (6-2010)
Abstract
Considerations on the explosion resistant design of special infrastructures have increased in the recent
years. Amongst the various types of infrastructures, road and railway tunnels have a unique importance due to their
vital role in connection routes in emergency conditions. In this study, the explosion effects of a projectile impacting on
a railway tunnel located in a jointed rock medium has been simulated using 2D DEM code. Primarily, a GP2000
projectile has been considered as a usual projectile and its penetration depth plus its crater diameter were calculated
in rock mass. The blast pressure was, then, calculated via empirical formula and applied on the boundary of crater as
input load. Finally, the wave pressure propagation through the jointed rock medium was investigated. In part of the
study a sensitivity analysis has been carried out on jointed rock parameters such as joint orientation, dynamic modulus
and damping ratio. Their effects on tunnel lining axial force as well as bending moment have also been investigated.
Malik Shoeb Ahmad, S. Salahuddin Shah,
Volume 8, Issue 4 (December 2010)
Abstract
Roadways have a high potential for utilization of large volume of the fly ash stabilized mixes. In this study, an attempt has been made to investigate the use of Class F fly ash mixed with lime precipitated electroplating waste sludge–cement as a base material in highways. A series of tests were performed on specimens prepared with fly ash, cement and lime precipitated waste sludge. California bearing ratio (CBR) tests were conducted for 70%-55%fly ash, 8%cement, and 30%-45%waste sludge combinations. Results show that the load bearing strength of the mix is highly dependent on the waste sludge content, cement as well as curing period. The CBR value of fly ash mixed with electroplating waste sludge and cement has been increased to manifold and results the reduction in the construction cost of the pavement. The study also encourages the use of two potentially hazardous wastes for mass scale utilization without causing danger to the environment, vegetation, human and animal lives.
Mohammad Hassan Baziar, Habib Shahnazari, Hassan Sharafi,
Volume 9, Issue 2 (June 2011)
Abstract
This paper discusses the applicability of a simple model to predict pore water pressure generation in non-plastic silty soil during
cyclic loading. Several Stress-controlled cyclic hollow torsional tests were conducted to directly measure excess pore water pressure
generation at different levels of cyclic stress ratios (CSR) for the specimens prepared with different silt contents (SC=0% to 100%).
The soil specimens were tested under three different confining pressures (&sigmaƉ= 60, 120, 240 kPa) at a constant relative density
(Dr=60%), with different silt contents. Results of these tests were used to investigate the behavior of silty sands under undrained
cyclic hollow torsional loading conditions. In general, beneficial effects of the silt were observed in the form of a decrease in excess
pore water pressure and an increase in the volumetric strain. Modified model for pore water pressure generation model based on
the test results are also presented in this paper. Comparison of the proposed pore pressure build up model with seed’s model
indicates the advantage of proposed model for soil with large amount of silt.
M. Hassanlourad, H. Salehzadeh, H. Shahnazari,
Volume 9, Issue 4 (December 2011)
Abstract
The effects of cementation and the physical properties of grains on the shear behavior of grouted sands are investigated in this
paper. The consolidated-undrained triaxial shear behavior of three grouted carbonate sands with different physical properties,
including particle size distribution, particle shape and void ratio, was studied. Two sands were obtained from the north shores
of the Persian Gulf, south of Iran, called Hormoz and Kish islands sands, and one sand was obtained from the south beaches
of England and called Rock beach sand. The selected sands were grouted using a chemical grout of sodium silicate and tested
after one month of curing. Test results showed that the effect of bonding on the shear behavior and strength depends on the bond
strength and confining pressure. In addition, the shear behavior, yield strength and shear strength of grouted sands under
constant conditions, including the initial relative density, bonds strength, confining pressure and loading, were affected by the
physical properties of the sands. Furthermore, the parameters of the Mohr-Coulomb shear strength failure envelope, including
the cohesion and internal friction angle of grouted sands under constant conditions, were affected by the physical properties
and structure of the soils.
A. R. Majidi, A.a. Mirghasemi, M. Arabshahi,
Volume 9, Issue 4 (December 2011)
Abstract
In the current study, an effort is made to determine three dimensional bearing capacity of rectangular foundations using Discrete
Element Method. The soil mass is modeled as discrete blocks connected with Winkler springs. Different factors affect the geometry
of failure surface. Six independent angles are used to define the failure surface. By trial and error, the optimum shape of failure
surface beneath the foundation can be found. The paper includes the derivation of the governing equations for this DEM based
formulation in three dimensional state as well as parametric sensitivity analyses and comparison with other methods. Moreover,
using the current method, bearing capacity coefficients are presented for various friction angles and foundation aspect ratios.
M. Ameri, J. Shahi, H. Khani Sanij,
Volume 11, Issue 1 (TransactionA: Civil Engineering, March 2013)
Abstract
The use of geotextiles to postpone reflective cracks in asphalt overlay is a popular practice, so researchers are eager to calculate
its structural value. This research study has focused on this issue for geotextiles used in the roads of Iran. Twelve sections from
the Tehran-Qom road were tested each examined before and after construction of the overlay. The tests were of the Falling
Weight Deflectometer type, and at least twelve tests were conducted each time. The data from five sections (four for developing
the model and one for evaluating the output) allowed a new mathematical model to be developed. For the seven remaining
sections, some foreign and Iranian geotextiles were used as interlayers. The mean structural value for all of the geotextiles was
equivalent to that of a 2.92 cm-thick Hot Mix Asphalt overlay, while that for only the Iranian sections was equivalent to 2.28 cm.
Economic evaluations, based on construction costs, showed that in 2011 the use of geotextiles was economical in Iran, because
fuel and bitumen subsidies had been eliminated and different geotextile brands had been brought to market in the country.
P. Vahabkashi, A. R. Rahai, A. Amirshahkarami,
Volume 12, Issue 1 (Transaction A: Civil Engineering March 2014)
Abstract
Piles or drilled shafts used in bridge foundation, waterfronts, and high rise buildings are generally subjected to lateral loads. In order to study the effect of concrete pile geometry on the structural behavior in layered soils, several models with different shapes and dimensions for piles and different properties for two soil layers with variable thickness were selected and analyzed using the finite difference method.
The performance of piles situated in layered granular soil with different compaction and thicknesses were studied in two cycles of lateral loading and unloading. The applied finite difference procedure is also validated based on experimental and published results.
The pile head displacement of different models due to their overall deformation and rotation were calculated under maximum loading. For a comparison of pile head displacement due to their overall deformation and rotation in different models, the "performance index” is defined as the ratio of “displacement due to deformation” to the “total displacement”.
E. Lotfi, S. Delfan, A. Hamidi, H. Shahir, Gh. Fardi,
Volume 12, Issue 1 (Transaction B: Geotechnical Engineering, January 2014)
Abstract
In saturated soils, heating induces thermal expansion of both grains and the pore fluid. Lower thermal expansion
coefficient of aggregates results in the increase of pore pressure and reduction of the effective stress besides subsequent
volume changes due to the dissipation of pore pressure and heat transfer. Dissipation of thermally induced pore pressure with
time is a coupled thermo-hydro-mechanical (THM) phenomenon, involving gradients of pore pressure and temperature,
hydraulic and thermal flows within the mass of soil and changes in the mechanical properties with temperature. The objective
of this paper is presentation of a numerical method to determine the effect of temperature on consolidation of clays. In this
regard, the finite element code, PISA is used for one dimensional THM analysis of porous media. The analysis performed
using both linear elastic and elastoplastic Cam clay models. Modified Cam clay model was applied in elastoplastic analysis.
Variation of temperature, displacements and pore pressure determined with time and compared with numerical solutions of
other researchers. Also it was indicated that implementation of coupled THM analysis yields better results for displacements
compared to the hydro mechanical (HM) one. Application of elastoplastic constitutive model instead of linear elastic one
indicated that preconsolidation pressure has an important effect on results of analysis.