2024-03-28T16:13:12Z
https://ijstc.shirazu.ac.ir/?_action=export&rf=summon&issue=375
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
ON THE PERFORMANCE OF A MODIFIED MULTIPLE-DEME GENETIC
ALGORITHM IN LRFD DESIGN OF STEEL FRAMES
This paper investigates the performance of a multiple-deme genetic algorithm (GA)with modified reproduction operators, in optimal design of planar steel frames according to theAISC-LRFD specification. The design objective is to minimise the weight of frame subject tostrength, displacement and constructability constraints. A number of new crossover and mutationoperators, used alongside the standard operators are utilised in optimum design of a number ofsteel frames subjected to the constraints of the AISC-LRFD specification, with and withoutconsidering the second order effects, as set out by the code requirements. This modified GA(MGA) is shown to have a very fast convergence and to produce relatively high-quality designs.This paper also utilizes the concept of multiple-deme in the GA, as it has been used successfullyfor other metaheuristic population-based methods. The multiple-deme GA is used alongside themodified GA operators and the algorithm is named the modified multiple-deme GA (MMDGA).The modified GA (MGA) and modified multiple-deme GA (MMDGA) are applied to threebenchmark problems and the results are compared to those obtained by other metaheuristicmethods. In the majority of cases, the results of comparisons suggest the superiority of theMMDGA in terms of the quality of final design and the total number of performed finite elementsanalyses.
Optimum design
multiple-deme genetic algorithm
steel frames
AISC-LRFD
2013
08
01
169
190
https://ijstc.shirazu.ac.ir/article_1610_6b28ea97606178cbe320c7cde9db0c35.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
APPLICATION OF KRONECKER PRODUCT TO THE ANALYSIS
OF MODIFIED REGULAR STRUCTURES
In this paper, structures transformable to regular forms are studied. Here, two cases areinvestigated. In the first case, the effect of different boundary conditions on these structures areexplored, and in the second case the effect of adding or removing members and nodes are studied.In some structures the graph model is regular and different boundary conditions change thecorresponding block matrices into non-regular ones. In some other structures the addition orremoval of nodes and/or members changes the structure into a regular one. Here an efficientmethod is presented for dealing with the above-mentioned irregularities.The main idea steams from the fact that on the one hand there exist simple relationships forfinding the inverse of some block matrices related to regular structures, and on the other hand wewant to find out how to obtain the inverse of matrices corresponding to structures which becomeregular by the addition or removal of some members and/or nodes.One of the applications of the present method is related to the finite difference (FD) methodfor the analysis of plates with some irregularities in their boundary or having different supportconditions.
Kronecker product
graphs
regular structures
plates
finite difference method
2013
08
01
191
202
https://ijstc.shirazu.ac.ir/article_1611_c240d735b0423e1c4b1ee3949f1c621c.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
HAZARD MITIGATION AND EXTERNALLY FRP RETROFITTING OF
RC BUILDINGS SUBJECTED TO NEAR-FAULT GROUND
MOTIONS HAVING FORWARD DIRECTIVITY
Ground motions in the near field of a rupturing fault differ from ordinary groundmotions, as they contain a large energy, or “directivity” pulse. This pulse can cause considerabledamage during an earthquake. Failures of modern engineered structures observed within the nearfaultregion in the recent earthquakes have revealed the vulnerability of existing RC buildingsagainst pulse-type ground motions. This may be due to the fact that these modern structures hadbeen designed primarily using the design spectra of available standards which was developedusing stochastic processes with relatively long duration that characterizes more distant groundmotions. Many recently designed and constructed buildings may therefore require strengthening inorder to perform well when subjected to near-fault ground motions. This paper presents the resultsof a study of the response of typical existing RC buildings to near-fault ground motions and thepotential improvements achievable after FRP retrofitting of the buildings. Results show that incase of near-fault records, they impose higher demands in comparison to far-fault records, thoughthe maximum drift is generally concentrated at the middle story levels. It is demonstrated thatstrengthening with FRP is very effective in reducing drift demands for structures for a wide rangeof natural periods. The rehabilitated buildings possess an elastic stiffness 1.4 times that of theoriginal buildings and have a total shear force capacity, 1.5 times that of the original buildings.The cumulative energy dissipation for rehabilitated specimens is 2.3 times that of the originalbuilding, on average.
Forward directivity
near-fault ground motion
rehabilitation
FRP
dynamic analysis
2013
08
01
203
218
https://ijstc.shirazu.ac.ir/article_1612_5c1083a9432a764071154108103cc29c.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
EFFECT OF CONCRETE STRENGTH AND GROOVE DIMENSION ON
PERFORMANCE OF GROOVING METHOD TO POSTPONE
DEBONDING OF FRP SHEETS IN STRENGTHENED
CONCRETE BEAMS
A major obstacle in using FRP sheets for flexural and shear strengthening has beendebonding failure, which leads to premature and noneconomic failure of the strengthened element.Surface preparation of concrete member has been widely used to provide good bonding of thecomposite sheet onto concrete surface; however, it is found to be only partially effective indelaying debonding. Recently, Grooving Method (GM) has been introduced as a novel substitutefor conventional surface preparation in Externally Bonded Reinforcement (EBR) strengthening ofconcrete beams. Although the previous experiments have shown that grooving method canpostpone or even eliminate the debonding of FRP sheets from concrete substrate, the method isstill in its early stages of development and awaits further research for maturation. The presentstudy is an attempt to examine the effectiveness of grooving method for beams with differentconcrete compressive strength; also, to investigate the effects of groove depth and width oncontrolling FRP debonding for concrete specimens with different compression strengths.The experimental specimens included 44 concrete beams, which with three samples per beamresulted in a total of 132 specimens. Initially, two grooves of varying widths and depths were madein each specimen. The grooves were then filled with an appropriate epoxy resin and the FRP sheetswere bonded onto the concrete surface. After the resin had hardened, the specimens were subjectedto the four-point flexural test. The experimental results showed the superiority of grooving methodon conventional surface preparation for all four experimental categories with different compressivestrength of concrete. The results also showed that a depth of 10 mm may be the optimum groovedepth for all four experimental categories.
Debonding, fiber reinforced polymer (FRP), grooving
RC beams, strengthening, surface preparation
2013
08
01
219
232
https://ijstc.shirazu.ac.ir/article_1613_8ba6078c1779e639c401f4e0b3010cf6.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
EFFECTS OF DIFFERENT FREQUENCY CONTENT OF MULTI-SUPPORT
EXCITATIONS ON SEISMIC RESPONSE OF
A LARGE EMBANKMENT DAM
This paper focuses on examining the combined effects of frequency content and spatialvariability of the ground motion on the response of a large embankment dam. A series of nonuniformground motion time histories are generated using spectral representation method. Theinfluence of frequency content of seismic excitation is taken into account by using three differenttypes of target response spectra selected from Uniform Building Code (UBC 1994). It is found thatthe use of identical ground motions compatible with the Types 1 and 2 response spectraoverestimates the acceleration responses by up to 15% and 30% higher than those of multi-supportexcitations, respectively. The above trend is qualitatively valid for Type 3 input motions at lowerelevations of the dam, but not at the crest of the dam where the uniform excitation yields slightlylower acceleration response. By comparing the displacement responses, it is demonstrated that theuniform input motions compatible with Types 1, 2 and 3 response spectra result in 10%, 35% and40% larger crest settlements, respectively, than those predicted under multi-support excitations.
Embankment dam
multi-support excitation
frequency content
response spectra
2013
08
01
243
256
https://ijstc.shirazu.ac.ir/article_1615_6ff699354c6cb812103b084d4b6d9505.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
BEARING CAPACITY OF FOOTINGS ON PILE-STABILIZED SLOPES
The present paper reveals the results of an analytical method to calculate the bearingcapacity of a footing supported on one or two rows of piles stabilizing slope. The variedparameters here include pile diameter, pile length, location of pile rows, location of footingrelative to the slope crest, foundation width, center to center spacing of piles in a row, and fixity ofthe pile head. Passive pile resistance is determined based on normal and shear resistance of the soilsurrounding the pile considering plastic deformation of soil between piles. The Pile resistanceobtained through the present method is compared with other analytical as well as 3D numericalones. The results indicate acceptable agreement. The footing bearing capacity is calculatedaccording to both the limit equilibrium slope stability analysis and soil stability beneath thefooting. The predicted results were compared with those reported from other experiments andindicated an acceptable agreement with increasing pile spacing. The results indicate that stabilizingthe earth slope with rows of piles has a significant effect on the footing of bearing capacityimprovement.
Slope stability
passive pile
footing
Bearing capacity
limit equilibrium
2013
08
01
257
269
https://ijstc.shirazu.ac.ir/article_1616_109364640e3761178ac817c0a07b9c19.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
HYDRODYNAMICS OF RIGHT-ANGLED CHANNEL
CONFLUENCES BY A 2D NUMERICAL MODEL
Hydrodynamics of open channel confluences is very complicated. Simulation of rightangledchannel confluences using a recently-developed 2D high-resolution model is presented inthis paper. Finite-volume discretization of governing equations is adopted and fourth-order Runge-Kutta time integration is used. The effects of three different and most influential parameters,including discharge ratio, width ratio and downstream Froude number on hydrodynamics of rightangledconfluences are studied. Standard Cartesian grids are employed and a single-block strategyis used for modeling the confluence. Turbulence shear stresses are included within the numericalmodel based on an eddy-viscosity approach. The results are compared with experimental data andshow satisfactory agreement, particularly in cases when 3D features of flow are negligible. Despitehaving 3D characteristics in most cases, the results of this study show that a much simpler andcomputationally effective 2D numerical model is also capable of detecting most important featuresof flow in confluences, including separation zone and zone of high-velocity.
Confluence
two-dimensional flow
finite volume method
high-resolution scheme
2013
08
01
271
283
https://ijstc.shirazu.ac.ir/article_1617_860e598a5afcb8d47335a7643037a0c1.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
ON VARIOUS DISPERSION MODELS FOR SIMULATING
FLOW AT CHANNEL BENDS
In this paper, by using depth-averaged equations, three different dispersion models forsimulating flow at channel bends are presented and compared. Two of these models employ powerlaw velocity distributions for longitudinal velocity components and linear distributions fortransverse component, and the last model employs logarithmic velocity distributions in transverseand longitudinal directions. The first two models differ in how the effect of secondary flow isevaluated. Boundary-fitted curvilinear coordinates in conjunction with finite-volume method havebeen used for discretization of the governing equations. The numerical results are compared withavailable experimental data of a 270o bend. The study shows that a power law distribution forstreamwise velocity with a suitable estimation of secondary flow intensity gives the best results forsimulation of two-dimensional depth-averaged flow in open channel bends among the modelsstudied. This model can successfully predict the most important characteristics of flow in curvedchannels.
Open channel flow
channel bends
momentum dispersion
secondary flow
depth-averaged flow
2013
08
01
285
299
https://ijstc.shirazu.ac.ir/article_1618_63b3e82ce464dfb1ce2c007c177af1d4.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
PREDICTING DOROODZAN DAM HYDRAULIC BEHAVIOR
DURING RAPID DRAWDOWN
Doroodzan dam is a 57m high earth dam with rip-rap cover constructed on Kor River inBakhtegan Basin. The dam is located at 30° 12' 2'' north latitude and 52°25' 5'' east longitude~70km north of Shiraz, Iran. The dam reservoir supports a large amount of agricultural, industrial,and urban demands in the region. The reservoir volume is 993 M.C.M at the normal pool level andthe dam crest length is ~700m. In this paper, a 3-D finite element model of the dam wasconstructed and analyzed for steady and transient conditions. Transient pore water pressurefluctuations were predicted at different piezometer locations for a 21-day rapid drawdown of23.9m. It was found that seepage through the dam is not sensitive to hydraulic conductivity ofdownstream dam body, apparently due to the effective hydraulic behavior of the chimney drainagethere. Under rapid drown down conditions, a maximum of 11.8m excess pore water pressure onupstream part of the dam was observed (compared to the steady state conditions) while nosignificant excess pressure was seen at the downstream part of the dam. Dynamics of the phreaticline location during the 21-day rapid drawdown was monitored in four 5.25-day time steps. Agradual phreatic line change at time steps ending at the 21-day period was predicted. Phreatic lineat the upstream face of the dam closely followed the reservoir level rapid drawdown. However,phreatic line at the interior sections of the dam did not drop as fast. As a result, a gradient towardsupstream face of the dam was developed after ~10 days which might jeopardize slope stabilitythere. It is recommended that the excess pore water pressure be carefully considered in damanalysis researches, especially during the transient periods. In general, rapid drawdown should becautiously analyzed in dams, especially those with short emptying times, as it may reverse theseepage direction, endanger the slope stability, and not allow excess pore water pressure todissipate in an acceptable manner.
Doroodzan dam
rapid drawdown
pore water pressure
transient analysis
hydraulic behavior
2013
08
01
301
310
https://ijstc.shirazu.ac.ir/article_1619_1a05805ec945c3efb88018e18be08495.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
LABORATORY MODELING OF TWO-DIMENSIONAL DIFFUSIVE
AND ADVECTIVE-DIFFUSIVE CHLORIDE TRANSPORT
THROUGH SILT AND CLAY
Two-dimensional diffusive and advective-diffusive chloride transport through clay andsilt, respectively, was investigated using laboratory models. The observed chloride concentrationplumes in the soil samples as well as the chloride concentration-versus-time profiles in the sourcereservoirs were predicted using the computer code MIGRATEv9. Equivalent horizontal andvertical chloride diffusion coefficients reasonably predicted the observed concentration plumesand concentration-versus-time indicating that soils were homogeneous and isotropic. The predicteddiffusion coefficients were in the range of the reported values for similar soils. The effect ofdownward Darcy flux in the advection-diffusion tests on the chloride concentration plumes wasassessed by comparing the shapes of the plumes with those in the pure diffusion tests. Thedownward Darcy flux caused the concentration plumes in the advection-diffusion tests to migratefurther in the vertical direction compared to that in the horizontal direction. All plumes spreadsymmetrically with respect to the vertical axis of symmetry of the silt samples, and the appliedhorizontal base flow had no significant effect on the symmetrical shape of the plumes in theadvection-diffusion tests. Overall, the existing two-dimensional advective-diffusive-dispersivecontaminant transport theory as implemented in the computer code MIGRATEv9 reasonablypredicted the chloride migration through silt and clay.
2-D laboratory modeling
diffusion
advection-diffusion
clay
silt
2013
08
01
311
324
https://ijstc.shirazu.ac.ir/article_1620_ff1c637f3ffb39192bee54420bbdcd2d.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
APPLICATION OF ARTIFICIAL NEURAL NETWORKS FOR PREDICTING
COD REMOVAL EFFICIENCIES OF ROTATING DISKS AND
PACKED-CAGE RBCS IN TREATING HYDROQUINONE
In this study, an artificial neural network (ANN) was applied to predict the performanceof two rotating biological contactor (RBC) systems in removal of hydroquinone (a toxic aromaticcompound). The first system was a two-staged conventional RBC and the second one was a onestagedpacked-cage RBC with bee-cell 2000 biofilm carriers. Both systems had a total area ofabout 2 m2 for biofilm attachment. The main aim is to predict COD removal efficiencies in bothsystems using ANN. Efficiency evaluation of the reactors was obtained at different influent CODfrom 200 to 5000 mg/L. Exploratory data analysis was used to detect relationships between thedata and the evaluated dependents. The appropriate architecture of the neural network models wasdetermined using several steps of training and testing the models. The modeling results showedthat there is a good agreement between the experimental data and the predicted values with acorrelation coefficient (R2) of 0.998 and 0.997 for RBC with rotating disks and packed-cage RBC,respectively.
Hydroquinone
COD
rotating biological contactor
Neural Networks
2013
08
01
325
326
https://ijstc.shirazu.ac.ir/article_1621_196d9dcebba8c9e043965608b7a70f66.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
NUMERICAL ANALYSIS OF FAULT BEHAVIOR NEAR
UNDERGROUND EXCAVATIONS
In this paper, the behavior of a fault is studied using a constant strain joint model. Acombination of slider and spring is used to simulate the shear behavior of faults in the plasticregion in contrast to the previous models that have only used an elastic shear spring. Furthermore,the proposed joint element was used to study the behavior of a fault crossing a tunnel regarding therepresented shear plastic and dilation behavior of this joint element, and for this purpose a Matlabbased program called FEAFB (Finite element analysis of fault behavior) has been developed. Thecorresponding normal and shear stresses, shear strengths and the factors of safety, for differenthorizontal to vertical stress ratios and shear stiffness are analyzed and compared to the results of asimilar modeling in UDEC program. The analysis indicates that the normal and shear stresses, andthe shear strength are increased in the fault elements near the tunnel, and they are decreased in theelements becoming far from the tunnel surface. However, the safety factor can either increase ordecrease as it becomes closer to the tunnel surface, depending on the horizontal to vertical stressratio. Moreover, it is also shown that safety factor depends upon the shear stiffness, i.e., as shearstiffness increases, shear stress increases, and as a result, the safety factor decreases.
fault
joint element
dilation
finite element
tunnel
2013
08
01
337
343
https://ijstc.shirazu.ac.ir/article_1622_66ea3c1d8b2a39b36b5db5c9d83340d5.pdf
Iranian Journal of Science and Technology Transactions of Civil Engineering
2228-6160
2228-6160
2013
37
2
INELASTIC DAMAGE ANALYSIS OF RCMRFS
USING PUSHOVER METHOD
The main objective of this research is to develop a practical damage criterion based onpushover analysis. For this purpose, damage analysis is performed on several Reinforced ConcreteMoment Resisting Frames (RCMRFs). In the static method, performance point of structures isfirstly determined using capacity spectrum method and then values of several different damageindices are calculated at these points. By comparing the results of two methods and evaluatingcorrelation between two sets, explicit damage relations are derived based on the static results.
Damage index
nonlinear dynamic analysis
pushover
Performance
capacity spectrum
2013
08
01
345
352
https://ijstc.shirazu.ac.ir/article_1623_6fdaa72c5269a18662fa7d9e8e8e9730.pdf