

مجله ساينتيا ايرانيكا
Scientia Iranica
ISSN 10263098
دوماهنامه داراي رتبه علمي  پژوهشي (فني مهندسي) به زبان انگليسي
سال بيست و ششم، شماره 2 (پياپي 128)Transactions on Civil Engineering (A)




 Strength development of binary cement concrete, using Pulverized Fly Ash (PFA) under various curing conditions Shahab Samad,Attaullah Shah *,M.C. Lambachiya,S.B. Desai Pages 615624 Abstract Full Text [PDF 2025KB]   Binary Cement incorporating Supplementary Cementitious Material (SCM) is widely used in concrete to reduce the cement consumption in construction industry. Cement production is a major source for the emission of Green House Gases (GHG) and there is an increasing pressure to reduce its consumption to avoid further Global Warming and Climate changes etc. In this research، Pulverised Fly Ash was used to partially replace cement in the concrete. Three levels of replacement of cement by PFA were selected and the specimens were cured under summer and winter environments. The strength development characteristics of the blended concrete were compared with the control mix without PFA. The strength gain under winter curing condition was observed as slower. At water cement ratio of 0.35، concrete with 30 % replacement of cement by PFA achieved high early age strength. PFA concrete gained more strength than the PC concrete after the age of 28 days. The 28 days compressive strengths of blended concrete for 30 % of cement replacement by PFA has been observed as nearly the same as that of control concrete mix.
Keywords: Supplementary Cementitious Material, Pulverized Fly Ash, partial replacement, compressive strength, Curing
  
 Investigation of bridge abutment displacements constructed on piles and geogrid reinforced soil using the finite element method Hasan Taherkhani *,Milad Tajdini,Abdolreza Rezaee Arjroodi,Hosein Zartaj Pages 625633 Abstract Full Text [PDF 1260KB]   One of the major problems in highway and railway bridges is the settlement of the bridge abutments، which its reduction has always been set as the research target. Two methods which have been widely used for controlling the settlement are either reinforcing the abutment subsoil with geogrid orconstructing the abutments on piles. This paper describes the application of a twodimensional finite element method (FEM) by using Plaxis2D V8.5 for comparing the performance of these two methods. The effect of the geogrid normal stiffness، length and depth of reinforcement on the horizontal and vertical displacement of abutment is also investigated. Data from an instrumented bridge abutment has been used for the model verification. The reduction of the bridge abutment،the vertical settlement and the horizontal displacement by pile and geogrid have been analysed and compared.It is found that constructing the abutment on piles has a better performance in reducing the vertical settlement of the bridge abutment. However، lower lateral displacement can be obtained by using a geogrid with a higher normal stiffness. It is also found that، while the vertical settlement is not affected by the geogrid stiffness، the horizontal displacement of the abutment decreases with increasing the stiffness.
Keywords: Abutment, pile, geogrid, displacement, FEM
  
 Axial translation of a rigid disc inclusion embedded in a pennyshaped crack in a transversely isotropic solid S. M. Dehghan Manshadi,Ali Khojasteh *,M. Rahimian Pages 678689 Abstract Full Text [PDF 2042KB]   In this paper، an analytical solution for the axisymmetric interaction of a rigid disc inclusion embedded in bondedcontact with the surfaces of a pennyshaped crack and a transversely isotropic medium is investigated. By using amethod of potential functions and treating dual and triple integral equations، the mixed boundary value problem iswritten in the form of two coupled integral equations، which are amenable to numerical treatments. The axial stinessof the inclusion and the shearing stress intensity factor at the tip of the pennyshaped crack for dierent degrees ofmaterial anisotropy are illustrated graphically. Useful limiting cases such as a rigid disc inclusion in an uncrackedmedium and in a completely cracked solid are recovered
Keywords: Pennyshaped crack, Rigid disc, Transversely isotropic, Axial stiness, Stress intensity factor, Integral equation
  
 A COMBINATION OF COMPUTATIONAL FLUID DYNAMICS, ARTIFICIAL NEURAL NETWORK AND SUPPORT VECTORS MACHINES MODEL TO PREDICT FLOW VARIABLES IN CURVED CHANNEL Azadeh Gholami,Hossein Bonakdari *,Ali Akbar Akhtari,Isa Ebtehaj Pages 726741 Abstract Full Text [PDF 1325KB]   This study show the combination of computational fluid dynamics (CFD) and soft computing techniques to make viewpoint for twophase flow modelling and accuracy evaluation of soft computing methods in the threedimensional flow variables prediction in curved channels. Therefore، artificial neural network (ANN) and support vectors machines (SVM) models with CFD is designed to estimate velocity and flow depth variable in 60° sharp bend. Experimental results in 6 different flow discharges of 5، 7.8، 13.6، 19.1، 25.3 and 30.8 l/s to train and test، ANN and SVM models is used. The results of numerical models with experimental values are compared and the models accuracy is confirmed. The results evaluation show that all three models ANN، SVM and CFD perform well in flow velocity prediction، with correlation coefficient (R) of 0.952، o.806، and 0.680، and flow depth (R) of 0.999، 0.696، and 0.614 respectively. ANN model to predict both velocity and flow depth variables with mean absolute relative error (MARE) of 0.055 and 0.004 is the best model. Then SVM and CFD models with MARE of 0.069 and 0.089 in velocity prediction and in flow depth prediction CFD and SVM models with MARE of 0.007 and 0.011 are the best models، respectively.
Keywords: ANN, SVM, CFD, Velocity, Flow Depth, 60° bend
  
تاريخ انتشار: 12/1/98 تلفن: 66005419، 66164090 (021)
تاريخ درج در سايت: 31/1/98
شمار بازديدکنندگان اين شماره: 200




