2020-11-25T11:48:03Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=272
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
6
Passive Devices for Wave Induced Vibration Control in Oshore Steel Jacket Platforms
A.A.
Golafshani
A.
GHOLIZADEH
Performances of tuned mass dampers and friction dampers to mitigate the wave induced
vibrations in jacket type oshore platforms have been compared in this study. Due to the random nature
of ocean waves, a full stochastic analysis method has been used to evaluate the response of the structures
equipped with these devices. A stochastic linearization technique has been used to take the nonlinear
behavior of friction dampers into account. The developed mathematical formulation has been applied to
evaluate the response of realistic models, and to nd out the optimal values for the adjustable parameters
of friction dampers. The results have been veried in comparison with time domain nonlinear analyses
results. Also, a computer utility has been provided in FORTRAN to perform the spectral fatigue analysis
of platforms and together with a Genetic Algorithm utility, it has been used to nd out the optimal
parameters of a tuned mass damper to dissipate the wave induced vibrations of the platforms. Although
the eciency of both dissipative systems increases for more
exible platforms due to the dominancy of the
dynamic response, the functionality of TMD devices is more dependent on the dynamic characteristics of
the platform; friction dampers seem to be more ecient for xed steel jacket platforms.
Steel jacket platforms
Power spectral analysis
friction damper
Stochastic linearization
Tuned Mass Damper
Genetic Algorithm
2009
12
01
http://scientiairanica.sharif.edu/article_3257_1edf50f9b81d94cc13cdf635fc239567.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
6
Nonlinear Cyclic Analysis of Reinforced Concrete Frames, Utilizing New Joint Element
A.A.
Tasnimi
S. SH.
Hashemi
M.
Soltani
In this article, a numerical model based on the layer approach is introduced for nonlinear
cyclic analysis of two-dimensional reinforced concrete frames. The advantage of the proposed analytical
procedure is that it takes the bond-slip, shear-slip and pull-out eects and, also, shears deformation in
the joints into account. Bar and concrete stress-strain relations, the bond stress-slip relation and the
shear stress-strain relation and, also, their cyclic behaviors are adopted as known specications. In the
modeling, each frame is divided into two types of joint element and beam-column element. The eect
of bond-slip has been considered in the formulation of a beam-column element by replacing the perfect
bond assumption from the ber analysis method. Joint elements are formulated upon major behaviors
including the pull-out of embedded longitudinal bars, shear and
exural deformation of joint panels and
shear slip in interface sections between joints and neighboring elements. The reliability of the method
has been assessed through a comparison of numerical and experimental results for a variety of specimens
tested under cyclic loading. A good agreement between experimental and analytical results is obtained for
both cases of strength and stiness during the analysis.
Nonlinear Analysis
RC frames
Bond-slip
Joint element
Pull-out eect
2009
12
01
http://scientiairanica.sharif.edu/article_3258_5910c2cfb850ed93d566b94468d8e6af.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
6
Development of Management Schemes in Irrigation Planning: Economic and Crop Pattern Consideration
A.
Ahmadi
S.
Nazif
M.
Karamouz
Increasing population has dramatically increased the request for agricultural products. In
addition, lands and water resources with suitable quality are limited. Therefore, optimal allocation of
limited resources to different demands has become very important in recent years. In this study, a model
is developed to optimize a water resources allocation scheme considering the conjunctive use of surface
water and groundwater resources, as well as determining a suitable crop pattern. The economic objective
function of the optimization model is to maximize the net benet, considering the water pumping cost,
crop cultivation cost and the benet of total crop production during the study time horizon. The eect
of a marginal water decit in the reduction of crop yield and water table
uctuations are considered. A
genetic algorithm is used to solve the optimization model. The proposed model is applied to the Varamin
plain to determine the optimal crop mix and water allocation from surface and groundwater. In order to
evaluate the results of the model, the performance indices are calculated. The eect of imposed policies
on the crop pattern is investigated through the denition of two scenarios and the results are compared.
Also, the potential of the study area, for applying decit irrigation strategies using economic analysis, is
investigated.
Conjunctive use
Water allocation
optimization model
Crop pattern
Genetic Algorithm
Water pricing
2009
12
01
http://scientiairanica.sharif.edu/article_3259_7ea80ed7eb3876b4a690ac07f9871a74.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
6
Eigensolution for Adjacency and Laplacian Matrices of Large Repetitive Structural Models
A.
Kaveh
M.
Nouri
N.
Taghizadieh
Many structural models such as grids, barrel vaults, trusses and frames with repetitive
units, known as regular structures, have structural matrices in the form of M = F(B; A;BT ). In this
paper, a simple and efficient method is presented for calculating the eigenvalues of the adjacency and
Laplacian matrices of regular structures. These eigenvalues can be used in studying the combinatorial
properties of these structures. Examples are included to show the accuracy of the presented approach.
Canonical forms
Tri-diagonal
Eigensolution
Adjacency matrices
Laplacian matrices
Repetitive structural models
2009
12
01
http://scientiairanica.sharif.edu/article_3260_6c78582f7956a95caf21db846512d2e4.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
6
Eigenproblems of Symmetric Planar Frames
A.
Kaveh
B.
Salimbahrami
In this paper, the graph models of planar frame structures with dierent symmetries are
decomposed and appropriate processes are designed for their healing in order to form the corresponding
factors. The eigenvalues and eigenvectors of the entire structure are then obtained by evaluating those
of its factors. The methods developed in this article simplify calculation of the natural frequencies and
natural modes of the planar frames with dierent types of symmetry.
Symmetry
Planar frames
Decomposition
Graph factors
Eigenvalues
Natural frequencies
2009
12
01
http://scientiairanica.sharif.edu/article_3261_0e8e484e3b8f44ec945ffa4302fea434.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
6
Response of Pure-Friction Sliding Structures to Three Components of Earthquake Excitation Considering Variations in the Coecient of Friction
F.
Khoshnoudian
V.
Rezai Hagdoust
In the present study, the in
uence of the coecient of friction on the seismic response
of sliding base isolated structures is investigated. The building is modeled as a simplied single-story
structure resting on a group of sliding supports. The frictional forces mobilized at the sliding supports
are assumed to have a hysteretic plasticity behavior. Bilateral interaction between the stiness of the
two horizontal orthogonal directions of the isolators has been taken into consideration. The results show
that the variations of the coecient of friction in
uence the response of a sliding base isolated building.
Eects of vertical excitation on the normal and frictional forces are considered too. The in
uence of
the bi-directional interaction of frictional forces and vertical excitation on the response is investigated by
comparing the response of the system to mono-directional (excluding vertical component and no interaction
between the two horizontal orthogonal directions), bi-directional (excluding vertical component) and tridirectional
earthquake excitations. It is demonstrated that the response of the sliding isolated structures
is in
uenced signicantly by the bi-directional interaction of frictional forces and by incorporation of the
vertical component. Further, the base shear response may be underestimated if the eects of the vertical
component are neglected and the sliding structures are designed merely on the basis of single-component
or two-component excitation.
Frictional base isolated structure
Three-component earthquake
Velocity-pressure dependent friction coecient
Bi-directional interaction
Vertical component
2009
12
01
http://scientiairanica.sharif.edu/article_3262_608ad4d22efcb0c341b329c224c6be53.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
6
Nonlinear FE Analysis of Reinforced Concrete Structures Using a Tresca-Type Yield Surface
M.
Rezaee-Pajand
I.
Rahmani
M.
Nazem
This paper presents a nonlinear analysis of reinforced concrete structures. Various yield
surfaces of concrete are reviewed in the beginning and then a recently proposed yield surface for concrete is
introduced. The yield surface considers the behavior of concrete in a three-dimensional stress state. Based
on the yield surface, a nonlinear nite element formulation is provided to facilitate a three-dimensional
analysis of reinforced concrete structures. An eight-node brick element is used in the analysis. Several
numerical examples are given to show the ability of the yield surface in solving nonlinear reinforced
concrete problems.
Finite Element Method
Yield surface
Nonlinear Analysis
Reinforced concrete
2009
12
01
http://scientiairanica.sharif.edu/article_3263_0ba614c2a900201a83016ee108db9848.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
6
Failure Criteria of Unreinforced Grouted Brick Masonry Based on a Biaxial Compression Test
A.A.
Tasnimi
M.S.
Mohammadi
B.
Badarloo
To dene failure under biaxial stress, a three-dimensional surface in terms of two principal
stresses and their orientation to the bed joints is required. This article describes a series of biaxial
compression tests on full-scale brick specimens. Tests were performed on square unreinforced grouted
brick masonry specimens with the principal compressive stresses oriented at 0 and 90 degree angles to
the bed joints, and a failure surface was obtained in terms of these parameters. Test results indicated
that the masonry strength under equal biaxial compression is higher by about 36% on average than that
under uniaxial compression; the in
uence of joint orientation is very insignicant and negligible for these
models.
Failure criteria
Masonry panel
Principal stress
Biaxial stresses
Bed joints
2009
12
01
http://scientiairanica.sharif.edu/article_3264_9842ce196bad2080518da1d9d98e61e1.pdf