2020-11-28T04:01:46Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=156
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2014
21
3
Effects OF OPENINGS ONLATERAL STIFFNESS AND STRENGTH OF CONFINED MASONRY WALLS
Sassan
Eshghi
Behrang
Sarrafi
Confined masonry construction is made up of masonry walls and confining ties, which are built on all four sides of each wall. This system is a conventional form for constructing houses as well as a good alternative for post-disaster reconstruction of the seismically damaged and/or collapsed buildings in many countries. Window and door openings appear in many panels of confined masonry buildings, but many codes do not consider the effect of these openings in the strength and the stiffness of confined masonry panels.In this study, the influence of the masonry panel opening on the stiffness and the strength of confined masonry walls is investigated. A finite element program, DIANA, is used for finite element modeling of fully grouted confined masonry walls, walls with unfilled head joints, two-story walls, walls with lintel band and walls with added vertical ties on opening sides. All specimens have openings and are constructed according to the Iranian seismic code (Standard No. 2800-05). Models are validated by the results of the tests performed on two fully grouted one-story one-bay confined masonry walls and a two-story one-bay confined masonry wall constructed in Iran. Simple equations are proposed that predict the effect of central openings on the stiffness of different types of confined masonry walls and the cracking strength of fully grouted walls with openings.
Confined Masonry
Central Opening
Lateral stiffness
Cracking Strength
Seismic design
Reinforced Concrete Ties
2014
06
01
457
486
http://scientiairanica.sharif.edu/article_1647_672463566f020499061b6b8b6f181b18.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2014
21
3
Multi-period aerobic groundwater bioremediation system design; ACO approach
M.
Saeedi
A.
Afshar
H.
Hosseinzadeh
The optimal groundwater bioremediation design problem is complex, nonlinear, and computationally expensive. In this paper, an improved Ant Colony Optimization (ACO) algorithm is employed for optimizing a groundwater bioremediation problem, and the BIOPLUMEII model is used to simulate aquifer hydraulics and the bioremediation process. Injection and extraction pumping rates and well locations are treated as decision variables. Optimization results show that the proposed approach performs better than the Genetic Algorithm (GA), Simulated Annealing (SA) and the hybrid SA-GA algorithm, called Parallel Recombinative Simulated Annealing (PRSA), and reduces the computational time of a number of function evaluations compared with the mentioned algorithms. Applying the optimal dynamic pumping strategy in the second stage reduces bioremediation costs by 13:3%.
Groundwater
Contamination
Bioremediation
optimization
Ant colony
Dynamic pumping
2014
06
01
479
469
http://scientiairanica.sharif.edu/article_1648_3ca0aa1df44b6de1c5260217b98f1ac5.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2014
21
3
Dynamic Behavior of a Tension Leg Platform Offshore Wind Turbine under Environmental Loads
Alireza
Ebrahimi
Madjid
Abbaspour
Rasoul
Mohammadi Nasiri
In order to evaluate dynamic behaviors of floating offshore wind turbine, the authors consider two approaches. A numericalmethod is used to investigate a tension leg platform (TLP) offshore wind turbine response behavior in a parked condition. This code considers nonlinearities due to changes in the tension of tethers. The off-diagonal components of stiffness, damping and mass matrices are considered to calculate coupling. This code solves nonlinear equation of motion in each time step. However, in order to validate the data generated by the code, a scaled-down model was fully tested in the marine laboratory. The importance of these series of experiments is due to the fact that this model possesses a unique design and specification to which no other model can be compared. Measurement of three degrees of freedom under environmental loads is the goal of the experiments.[AE1]. Also, the results clearly show that direction of encountering waves is such an important factor. It can be concluded that wind loads can dampen oscillation of the model and it can prevent the impact of large loads on the tethers. The results show the discrepancy between experimental and numerical results in different degrees of freedom are acceptable enough
Offshore Wind Turbine
Floating Platform
Tension Leg Platform
numerical solution
Model test
Sea Wave Load
Wind Load
Fluid Structure Interaction
2014
06
01
480
491
http://scientiairanica.sharif.edu/article_1649_03f0fe7f5593956d2219815f237da7ff.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2014
21
3
Mixed discrete least square meshless method for solution of quadratic partial differential equations
S.
Faraji
M.H.
Afshar
J.
Amani
In this paper, the Mixed Discrete Least Squared Meshless (MDLSM) method is used for solving the quadratic partial differential equations (PDEs). In MDLSM method the domain is discretized only with nodes and a minimization of a least squares functional is carried out. The least square functional is defined as the sum of the residuals of the governing differential equation and its boundary condition at the nodal points. In MDLSM, the main unknown parameter and its first derivatives are approximated independently with the same Moving Least Squares (MLS) shape functions. The solution of the quadraticPDE does not, therefore, require the calculation of the complex second order derivatives of MLS shape functions. Furthermore, both the Neumann and Dirichlet boundary conditions can be treated and imposed as a Dirichlet type boundary condition which is applied using a penalty method. The accuracy and efficiency of the MDLSM method are tested against three numerical benchmark examples from one-dimensional and two-dimensional PDEs. The results are produced and compared with the irreducible DLSM method and exact analytical solutions indicating the ability and efficiency of the MDLSM method for the efficient and effective solution of quadratic PDEs.
Discrete least squares meshless
Quadratic partial differential equations
Moving least squares
Mixed meshless
Irreducible meshless
2014
06
01
492
504
http://scientiairanica.sharif.edu/article_1650_977cbd48f82ca43762f3a2584d46dadb.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2014
21
3
Estimation on bearing capacity of shallow foundations in heterogeneous deposits using analytical and numerical methods
R.
Jamshidi Chenari
N.
Zhalehjoo
A.
Karimian
In situ soil properties are spatially variable parameters causing soil deposits to be heterogeneous. Heterogeneity consists of two components: (i) A deterministic trend and (ii) The residual component. This paper presents the eect of dierent components of soil heterogeneity on the ultimate bearing capacity of a vertically loaded shallow foundation resting on clay deposits. The numerical model used in this study is based on nite dierence simulations, employing FLAC 5.0. Results of numerical analysis are compared with other simple and analytical solutions. For heterogeneous soil deposits, considering both linear and bi-linear deterministic trends, nite dierence tools were found to be able to reffect salient features of heterogeneity in bearing capacity estimation. An equivalent homogeneous analysis solution is introduced, in order to allow for heterogeneity, by adopting a representative depth for shear strength measurements. Stochastic variationof shear strength is shown to induce under conservatism by solely relying upon deterministic estimations.
shear strength
Shallow foundations
Bearing capacity
Finite dierencemethod
Heterogeneity
Equivalent homogeneity
2014
06
01
515
505
http://scientiairanica.sharif.edu/article_1651_3911e7b5984f5ccf952fa54368ad162d.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2014
21
3
Rotation capacity improvement of long link beams in Eccentrically Braced Frames
Behrouz
Chegeni
Amin
Mohebkhah
Short link beams in Eccentrically Braced Frames (EBFs) are generally preferred to long ones mainly due to their high rotation capacity and energy dissipation under cyclic loadings. However, long links have the advantage of providing openings in the braced spans of EBFs. Based on few tests conducted on long links’ behavior in the literature, the Seismic Provisions (AISC-341-05) limits their rotation capacity to a small value of 0.02 rad. In this paper, a three dimensional finite-element model using ABAQUS is developed for the inelastic nonlinear analysis of long linksto investigate their rotation capacity. It was found that, using some new intermediate stiffeners in addition to those specified in the Seismic Provisions, large rotation capacity for long links can be achieved.
Eccentrically Braced Frame
Long Link Beam
Inelastic Rotation Capacity
Seismically Compact Sections
Stiffener
2014
06
01
516
524
http://scientiairanica.sharif.edu/article_1652_c8cc6fe7e23315798e18a127997280d7.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2014
21
3
Investigating Climate Change Impact on Extreme Rainfall Events (Case Study: Chenar-Rahdar Basin, Fars, Iran)
Amir
Pourtouiserkani
In this research,the impact of climate change on extreme rainfall events in Chenar-Rahdar Basin, Shiraz, Iran, was investigated utilizing three statistical downscaling methods; namely change factor, LARS-WG, and SDSM. Daily precipitations with different recurrence periods were projected for the future period of 2011-2040 (2020s) based on two AOGCM output data (HadCM3 and CGCM3) under A2 emission scenario.In summary, HadCM3 (for three downscaling methods) projected an increasing trend (of up to 21.8%) in extreme rainfall events for 2011-2040 period with respect to the base period. On the other hand, CGCM3 showed an increasing trend for extreme rainfall events for the first two methods (up to 24.7%), while SDSM method resulted in an increasing trend (up to 3.6%) for recurrence periods of 20- and 25-yr and a very small decreasing trend (down to -2%) for recurrence periods of 50- and 100-yr. Relatively low correlation coefficients in multiple regressions obtained for both AOGCMs reflect limitations of SDSM in downscaling precipitation data in the study area. Comparing three downscaling techniques utilized in this study, it is concluded that using change factor or LARS-WG downscaling methods would be conservative enough in climate change impact assessment for the next 30 years.
Climate change
Extreme Events
Downscaling
Change Factor
LARS-WG
SDSM
2014
06
01
525
533
http://scientiairanica.sharif.edu/article_1653_253c5d3f97f7fc53e08df43d9126a49c.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2014
21
3
A novel force-based approach for designing armor blocks of high-crested breakwaters
A.
Pak
M.
Sarfaraz
Rubble-mound breakwaters are common marine structures that provide a safe area for human coastal activities. The stability of these structures against sea-waves requires their seaward slope to be protected by an armor layer consisting of natural rock or concrete units. To provide a safe breakwater, it is reasonable to establish a relation between the exerted wave loads and the stability of the armor units. However, up to now,the empirical design equations, derived from model tests, relate wave parameters to armor weight, and keeps the eect of wave loads in a black box. In this paper, a new approach, based on numerically-derived wave loads on the armor, is presented to evaluate the stability of these protective units. Results indicate that by increasing wave height, the weight of the armor units does not necessarily increase. Wave breaking type strongly inuences the applied loads and stability of the armor units. New dimensionless numbers are introduced to provide relationships between wave parameters and stability indices of reakwater armor units at dierent locations. This approach claries the ambiguities of the design process caused by the complex flow eld, especially the wave breaking type near the breakwater.
Wave forces
Breakwaters
Armor units stability
Numerical Modeling
2014
06
01
534
547
http://scientiairanica.sharif.edu/article_1654_b07f751c5c3451bd877197513285e654.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2014
21
3
Dispersion around a circular cylinder in surface wave motion
M.A.
Toghi
M.
Jamali
In this paper, we examine fluid flow and associated dispersion around a circular cylinder under progressive surface wave motion. The ow eld and vortex shedding patterns were studied using ow visualization and Particle Image Velocimetry (PIV). Several patterns of vortex shedding were identied around a single cylinder. The vortex shedding patterns under progressive wave motion are similar to those observed in planar oscillatory flow, except in the way the vortices form and in the orientation they take. The observed vortex patterns in progressive wave motion are more unstable than those in planar oscillatory flow. Using particle tracking and the Lagrangian dispersion method, the dispersion coecients were calculated for various flow regimes. The observations conrm the calculations in general. It was also found that wave steepness can aect the shedding pattern. The vortices tend to shed more frequently in a wave direction at low wave steepness.
Water waves
Flow visualization
Particle imagevelocimetry
Lagrangian dispersion
2014
06
01
556
548
http://scientiairanica.sharif.edu/article_1655_6f9e4cf511bab1936889cab8dc81b1b7.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2014
21
3
Applicability of a numerical model to predict distribution of suspended sediment concentration in Dithmarschen Bight
Maryam
Rahbani
The main concern of this investigation is to evaluate the ability of Delft3D-flow package to study distribution of suspended sediment concentration (SSC) over the depth in the Dithmarschen Bight. The area consists of tidal channels and tidal flats with prevailing semi-diurnal tide and is tidally dominated. Required field data was prepared using the data collected by transmissometer and mechanical sampler. Factor of two of measured SSC were used to evaluate the performance of the model. Some dissimilarity was found between the modeled and measured SSC. To verify the reason, two comparing procedures were carried out. First the evolution of the vertical profile of the SSC from the model and the field were prepared and compared. In another procedure the snapshot of distribution of SSC during different phases of a tidal cycle were prepared for both model results and field data. It was found that the predicted SSC values are in good agreement with the field data during the periods of flood phase and low slack water. However, spatial dissimilarities are observed during the periods of high slack water and the ebb phase. An insufficient supply of sediment from the tidal flat predicted by the model was considered to be responsible.
suspended
sediment
Concentration
model
critical
Shear
Stress
tide
2014
06
01
557
567
http://scientiairanica.sharif.edu/article_1656_5981ee28d2b24a7e1e0f9bfbe9ffb1c1.pdf