Showing 10 results for Bagheri
A.r. Khaloo, and P. Bagheri,
Volume 18, Issue 1 (4-1999)
Abstract
In this paper, moment-curvature behavior and ductility of prestressed concrete members based on nonlinear analysis is investigated. Influence of various design parameters on ductility of flexural members is determined according to appropriate materials models for stress-strain curves of concrete, prestressing steel and conventional reinforcements. Parameters studied include reinforcing index (ω ̅), compressive steel ratio, type of prestressing steel and cross-sectional shape of members. The reinforcing index is the most influential parameter on ductility of prestressed members. This variable contains the influence of several other parameters, such as compressive strength of concrete and reinforcing ratio, and links prestressed, ordinary reinforced and partially prestressed concrete sections. For maximum permissible reinforcing index of 0.36β1 based on ACI design code, curvature ductility is between 1.5 to 3.0 and for ω ̅=0.2, which is the maximum value allowed for moment redistribution, ductility is greater than 4.0, and for ω ̅ less than 0.1, a ductility of greater than 10.0 is achievable. Influence of magnitude of ultimate strength of prestressing steel and cross-sectional shape on ductility is insignificant. Confinement has considerable effect on ductility.
M. A. Golozar and R. Bagheri,
Volume 19, Issue 1 (7-2000)
Abstract
In this paper
, the effect of curing time and temperature as well as various primers on durability of high density polyethylene on plain carbon steel have been investigated. The aim is to increase adhesion, improve durability and also to produce a defect-free in order to improve the corrosion resistance of steel substrate. For this purpose, after surface preparation and applying a primer (zinc phosphate, polyvinylalcohol, resol, stearic acid, and polyurethane) polymer coating was applied using electrostatic powder coating system. Coatings having 300 µ thickness were produced and then subjected to primary and secondary curing treatments. In addition to adhesion, ductility, and corrosion tests, quality of coatings were studied using scanning electron microscopy. The results obtained revealed that, surface porosity and uniformity of metal/coating interface is a function of curing time and temperature, as well as of the primers used. The best results obtained after curing for 45 min at 230˚C. The effects of primers were as following: no primers
M. H. Bagheripour, E. Shasavandi, and S. M. Marandi,
Volume 25, Issue 2 (1-2007)
Abstract
This paper introduces an accurate, fast, and applicable method for optimization of slip surfaces in earth slopes. Using Genetic Algorithm (GA), which is one of the modern and non-classic optimization methods, in conjunction with the
well -known Bishop applied method, the optimum slip surface in an earth slope is investigated and its corresponding lowest safety factor is determined. Investigations have shown that selection of appropriate variables to define and to solve the problem and determination of a good range for these variables have a profound effect on the speed of convergence in the problem. In the present study, appropriate variables have been defined for solving the problem in a way that the number of repetitions required to reach convergence are considerably reduced by up to 50% compared with other approaches. This has led to a drastic reduction in time and the memory required. The accuracy of the method is shown first by solving examples related to search for optimum failure surfaces of some homogenous, non-homogenous, and earth dam slopes and then by comparison of the results with those of other optimization techniques. In order to show the application of the present method in modern geotechnical engineering, a reinforced earth slope is studied and its failure surface is finally optimized
R. Bagheri and M.a. Golozar,
Volume 25, Issue 2 (1-2007)
Abstract
Using Electrostatic Spray Coating Technique, Polypropylene Powder (EPD 60R) was applied on carbon steel substrates at room temperature. In order to obtain a uniform coating, steel substrates with powder coatings were heated in a vacuum oven at various temperatures up to 250° C for various periods of time up to 45 min and a pressure of 200 mb. The coatings produced had thicknesses of around 470 microns. In order to modify the chemical structure of this polymer, the powder coatings containing various weight percentages of maleic (anhydride (MA) and a peroxide (TBHP or DCP) were also applied onto the steel substrates under the above conditions. Adhesion strength, wear resistance, and ductility of polymer coatings produced were assessed using ASTM standard methods. Results obtained revealed that the polymer coating containing 5 wt%. MA and 0.1 wt% TBHP had the best mechanical properties. Adhesive strength and wear resistance of this coating were 14.3 kgf and 250.3 cm, at 6 kgf, respectively, under the applied load of 6kg. Results obtained from DSC thermographs and IR Spectroscopy also proved the chemical bond formation (grafting) between the polymer and MA. The mechanical properties of coatings on steel substrate stem from such graftings.
H. Khabbazi, R. Bagheri, and M.a Golozar,
Volume 26, Issue 1 (7-2007)
Abstract
Polypropylene (PP) has poor adhesion to metals and other surfaces for its chemical structure. Hence, chemical modification of PP is necessary for metal surface coating application. In this research, grafting of maleic anhydride (MA) onto co(propylene-b-ethylene) in the presence of a dicumyl peroxide (DCP) was accomplished in a single screw extruder. Characteristics of the modified polymer were determined by Infra-red Spectroscopy (IR), Scanning Electron Microscopy (SEM), and adhesion test. Maximum grafting of MA was found to be 1.2832% for 1.5 pph of MA. Adhesion test showed that the samples containing 1 pph of MA (degree of grafting is 0.5816%) had better adhesion to steel surface (17.25 kgf).
A.r. Bagheri and S. Hashemi,
Volume 26, Issue 2 (1-2008)
Abstract
S. Sookhtehsaraee, S.m.h Mirbagheri, and P. Davami,
Volume 27, Issue 2 (1-2009)
Abstract
Y. Mirbagheri, H. Nahvi, J. Parvizian,
Volume 34, Issue 2 (1-2016)
Abstract
Grid dispersion is one of the criteria of validating the finite element method (FEM) in simulating acoustic or elastic wave propagation. The difficulty usually arisen when using this method for simulation of wave propagation problems, roots in the discontinuous field which causes the magnitude and the direction of the wave speed vector, to vary from one element to the adjacent one. To solve this problem and improve the response accuracy, two approaches are usually suggested: changing the integration method and changing shape functions. The Finite Element iso-geometric analysis (IGA) is used in this research. In the IGA, the B-spline or non-uniform rational B-spline (NURBS) functions are used which improve the response accuracy, especially in one-dimensional structural dynamics problems. At the boundary of two adjacent elements, the degree of continuity of the shape functions used in IGA can be higher than zero. In this research, for the first time, a two dimensional grid dispersion analysis has been used for wave propagation in plane strain problems using B-spline FEM is presented. Results indicate that, for the same degree of freedom, the grid dispersion of B-spline FEM is about half of the grid dispersion of the classic FEM.
M. Moradi, M. Bagheri Nouri,
Volume 36, Issue 1 (9-2017)
Abstract
In order to obtain transmission spectra through a phononic crystal as well as its waveguide, a new algorithm is presented in this paper. By extracting displacement-based forms of elastic wave equations and their discretization, Displacement- Based Finite Difference Time Domain (DBFDTD) algorithm is presented. Two numerical examples are solvcd with this method and the results are compared with the conventional Finite Difference Time Domain (FDTD) method. In addition, the computational cost of the new approach has been compared with the conventional FDTD method. This comparison showed that the computation time of the DBFDTD method is 40 percent less than that of the conventional FDTD method.
M. Bagheri, B. Keshtegar,
Volume 37, Issue 1 (9-2018)
Abstract
In this paper, a new method is proposed for fuzzy structural reliability analysis; it considers epistemic uncertainty arising from the statistical ambiguity of random variables. The proposed method, namely, fuzzy dynamic-directional stability transformation method, includes two iterative loops. An internal algorithm performs the reliability analysis using the dynamic-directional stability transformation method and an external algorithm performs the fuzzy analysis by applying the alpha-cut level optimization method based on the genetic algorithm. Implementation of the proposed method, which solves some nonlinear performance functions, indicates the efficiency and robustness of the dynamic-directional stability transformation method, as compared to other first order reliability methods.
