Showing 9 results for Vafaei
M. Vafaeian,
Volume 5, Issue 1 (10-1987)
Abstract
M. Vafaeian,
Volume 8, Issue 1 (4-1990)
Abstract
M.e. Eslimi, M.m. Saadatpour, M. Vafaeian,
Volume 13, Issue 1 (7-1993)
Abstract
M.s. Marefat and M. Vafaei,
Volume 18, Issue 2 (7-1999)
Abstract
M. Vafaeian,
Volume 22, Issue 1 (7-2003)
Abstract
A finite element program based on elastic –plastic model of Mohr-Coulomb criterion was used to evaluate the bearing capacity coefficients of soil under shallow strip flexible footing . The results were compared with others’ analytical results and it was found that the present study could offer quite consistent and rather precise values for the bearing capacity coefficients .
The effect of different parameters such as E , υ, φ ,ψ ,γ , type of mesh idealization ,type of elements ,type of load distribution at the footing base have been examined and some new results obtained and discussed. The main conclusion can be summarized as : that the values of bearing capacity coefficients for any particular amount of friction angle should not be expressed as a single number solely dependent on the friction angle ,but the accurate values must be considered as the values dependent on some other effective parameters , which have been mentioned above .
Keywords : soil bearing capacity , finite element , Mohr-Coulomb , shallow footing
M. Vafaeian,
Volume 22, Issue 2 (1-2004)
Abstract
This paper presents the results of a recent study about the following aspects relevant to tunneling in soft grounds:e) The domain of deformations due to tunneling in soft ground can be specified within a boundary of a parabolic shape. This boundary is defined by a parabolic formula as a function of a central angle which depends on the soil type i.e., either cohesive or cohesionless. This parabolic shape can also be verified by a finite element computation.f) A finite element program has been applied to investingate the deformation characteristics around and above circular tunnels and to find the settlement ratio as a function of known variables such as, depth ratio, modulus of elasticity, and the thickness of soil layer beneath the tunnel. The finite element computations were carried out by assuming a given distribution of displacements around the tunnel perimeter, for which reason the method may be called “compulsory displacements”. It was found that although all the variables mentioned affect both the settlement ratio and the type of soil deformations, changing the values of modulus of elasticity affects only on the amount of deformation components, but not the settlement ratio.g) The results of finite element computations for the settlement ratio have been compared to other analytical curves and empirical data from some available case studies from which excellent agreements were found. also the contours of
Equal deformation components from the finite element program and from the simple formulae proposed by the author
were found to be quite similar and in acceptable agreement.h) Because the results obtained from the proposed formulae for the distribution of settlement at the ground surface are in excellent agreement with the relationships recently proposed by Loganathan & Poulos and the empirical data available, it is concluded that the simple analysis proposed here and the finite element computations based on the elasticity assumption can both be used to predict the deformation pattern around excavations in soft ground.
B.ebrahimian and M.vafaeian,
Volume 26, Issue 1 (7-2007)
Abstract
In spite of the fact that the effect of earthquake on earth dams has been widely studied during the past decades, the complicated behavior of such earth structures against different seismological characteristics is still unknown. Such ambiguities necessitate more accurate studies using more comprehensive computation tools to achieve new results describing the behavior of such structures subjected to earthquake loading. In the present study, the simple soil model of elastic, perfectly plastic (based on the Mohr-Coulomb criterion), and Rayleigh damping criterion have been adopted for the soil. First, the numerical model employed was verified by dynamic analysis of real cases such as “Long Valley” and “santa Felecia” earth dams. The computational results were then compared with real recorded data or with those reported by other researchers. In addition to evaluating seismic stability of earth dams, their seismic stability was verified using pseudo-static analyses. Therefore, the “Carsington” dam was analyzed to verify the results of pseudo-static analyses and to check the results of FLAC software in calculating the pseudo-static factor of safety. The values of calculated factors of safety in the present study are in good agreement with the published results in the literature. Furthermore, the failure behavior revealed in the analysis shows the ability of FLAC software in defining the failure surface. In the main part of the analyses, a parametric study was conducted for different selected conditions and specially the effect of dam height and the optimum size of crest width were investigated. The results are presented in relevant diagrams.
F. Yazdanpanah and A. Vafaei,
Volume 26, Issue 2 (1-2008)
Abstract
A systolic serial multiplier for unsigned numbers is presented which operates without zero words inserted between successive data words, outputs the full product and has only one clock cycle latency.
The multiplier is based on a modified serial/parallel scheme with two adjacent multiplier cells. Systolic concept is a well-known means of intensive computational task through replication of functional units and their repetitive use. Digital signal processing applications often involve high-speed sequential data. Bit-serial processing in particular can result in efficient communications, both within and between VLSI chips because of the reduced number of interconnections required. Serial input multipliers have received considerable attention, particularly for hardwired VLSI algorithms used in signal processing application, due to their minimal chip area required for interconnections. Bit-serial architectures are often used in parallel systems with high connectivity to reduce the wiring down to a reasonable level. The conventional add-shift technique for multiplication, which uses a minimum number of gates, is inexpensive to implement, but too slow to achieve the desired result. Iterative array multipliers are needed to satisfy the high speed requirement of systems. With the advantage of high scale integration, the hardware is not regarded as a major obstacle in implementation.
M. H. Musazadeh, R. Vafaei, E. Mohammad Sharifi, Kh. Farmanesh,
Volume 38, Issue 3 (Journal of Advanced Materials-Fall 2019)
Abstract
Finite element (FE) simulations in conjunction with experimental analysis were carried out to characterize the deformation behavior of an AISI 321 austenitic stainless steel (ASS) during cold pilgering process. The effect of process parameters including feed rate (4 and 8 mm) and turn angle (15, 30 and 60°) on damage build-up were also evaluated. The Johnson-cook model was used to simulate the flow behavior of material. By considering compressive stresses, a new revised Latham-Cockcraft damage was calculated and used to determine the optimum process parameters. It was found that the radial and hoop strains in all friction conditions were compressive, while the axial strains were observed to be tensile. The amount of strain (whether it is compressive or tensile strain) was also higher on the outside of the tube compared to its inside. By considering fatigue cycles of a tube element during the process, the feed rate of 8mm, turn angle of 60° and the lowest coefficient of friction were determined as optimum parameters.
