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    Numerical assessment of new compound restrainer for seismic retrofit of bridges

    , Article Structure and Infrastructure Engineering ; 2017 , Pages 1-20 ; 15732479 (ISSN) Joghataie, A ; Pahlavan Yali, A ; Sharif University of Technology
    2017
    Abstract
    This paper studies through numerical simulation a practical compound restrainer to use for the improvement of seismic performance of bridges. A mechanical model has been introduced for the restrainer and a basic optimisation approach has been conducted to evaluate the performance of the restrainer to changes in the properties of its components. A real 2-span simply supported plate girder bridge has been selected for case study. Using a detailed three-dimensional model, several non-linear time history analyses were performed under seismic excitations in order to assess the performance of the bridge retrofitted by conventional restrainers including linear and non-linear viscous dampers on one... 

    Numerical assessment of new compound restrainer for seismic retrofit of bridges

    , Article Structure and Infrastructure Engineering ; Volume 14, Issue 5 , 2018 , Pages 652-671 ; 15732479 (ISSN) Joghataie, A ; Pahlavan Yali, A ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    Abstract
    This paper studies through numerical simulation a practical compound restrainer to use for the improvement of seismic performance of bridges. A mechanical model has been introduced for the restrainer and a basic optimisation approach has been conducted to evaluate the performance of the restrainer to changes in the properties of its components. A real 2-span simply supported plate girder bridge has been selected for case study. Using a detailed three-dimensional model, several non-linear time history analyses were performed under seismic excitations in order to assess the performance of the bridge retrofitted by conventional restrainers including linear and non-linear viscous dampers on one... 

    Shape optimization of concrete arch dams considering stage construction

    , Article Scientia Iranica ; Volume 23, Issue 1 , 2016 , Pages 21-35 ; 10263098 (ISSN) Pourbakhshian, S ; Ghaemian, M ; Joghataie, A ; Sharif University of Technology
    Sharif University of Technology  2016
    Abstract
    This paper describes a methodology to develop the interface between a finite element software and optimization algorithm for optimization of concrete high arch dams. The objective function is the volume of the dam. The numbers of design variables are 31 including the thickness and upstream profile of crown cantilever, thickness of the left and right abutments, radius of curvature of water and air faces left and right by use of polynomial curve fitting and cubic spline function. The constraint conditions are the geometric shape, stress, and the stability against sliding. Initially, a program is developed in MATLAB in order to generate the coordinates of nodes; then, finite element software... 

    Extending concepts of mapping of human brain to artificial intelligence and neural networks

    , Article Scientia Iranica ; Volume 28, Issue 3 D , 2021 , Pages 1529-1534 ; 10263098 (ISSN) Joghataie, A ; Sharif University of Technology
    Sharif University of Technology  2021
    Abstract
    This paper introduces the concept of mapping of Artificially Intelligent (AI) computational systems. The concept of homunculus from human neurophysiology is extended to AI systems. It is assumed that an AI system behaves similarly to a mini-column or ganglion in the natural animal brain that comprises a layer of afferent (input) neurons, a number of interconnecting processing cells, and a layer of efferent (output) neurons or organs. The objective of the present study was to identify the correlation between the stimulus to each afferent neuron and the corresponding response from each efferent organ when the intelligent system is subjected to certain stimuli. To clarify the general concept, a... 

    λ-universe: Introduction and preliminary study

    , Article Advances in Neural Networks and Applications ; 2001 , Pages 140-145 ; 9608052262 (ISBN) Joghataie, A ; Sharif University of Technology
    World Scientific and Engineering Academy and Society  2001
    Abstract
    Interactions between the members of an imaginary universe, where all the members are adaptive and have learning capability, is simulated numerically by using artificial neural networks. The universe is called λ-universe for brevity. It is shown here that in such a universe, rules governing the behavior of the members might be formed inside the universe by its own members and the randomness which is observed in the behavior of its members is a direct result of the learning capability of the members. Although this is not a simulation of the real universe, some fundamental concepts of astrophysics have been implemented in it  

    Active control of trusses under heavy static loads

    , Article Neural Network World ; Volume 11, Issue 3 , 2001 , Pages 285-292 ; 12100552 (ISSN) Joghataie, A ; Sharif University of Technology
    2001
    Abstract
    Trusses are suitable load-bearing structural systems for heavy concentrated loads. In this paper, it is shown that it is possible to use active control mechanisms to enhance the load-bearing capacity of the trusses. Under heavy loading, some elements of a truss might experience high stresses and show non-linear behavior, resulting in large deformations in the truss. Under such a condition, some elements of the truss might damage which can lead to the collapse of the truss. Application of control forces on some of the degrees of freedom of the truss can render help the truss tolerate larger forces before its collapse. A neural network can then be trained to learn the relationship between the... 

    Discrete Hardware Neural Networks for Civil Engineering Application

    , M.Sc. Thesis Sharif University of Technology Avestakh, Saber (Author) ; Joghataie, Abdolreza (Supervisor)
    Abstract
    In recent years considerable effort has been made to advance the hardware Artificial Neural Networks where in most cases, many neurons are placed on a VLSI chip. This research attempts to build individual neurons and connect them to build a hybrid of analog and digital neural network. In fact, every neuron is an AVR microcontroller which has a number of inputs and outputs. The data transfer between neurons are done by both analog (PWM- ADC) and digital (UART). In the first part, the necessary voltage source and programmer and how to build are discussed. Next A\D convertor, PWM technique, UART and their usage in this project are demonstrated. After that, the neurons are calibrated to improve... 

    Damage Detection and Evaluation of Repair Materials and Techniques for Concrete Bridges

    , M.Sc. Thesis Sharif University of Technology Karimi, Roya (Author) ; Joghataie, Abdoreza (Supervisor)
    Abstract
    Poor maintenance of concrete bridges in the past years in Iran, caused serious damages, so most of them need rehabilitation. The majority of repaired members are exposed to repeated damage because compatibility of repair material to substrate concrete not considered as well as weather and loading conditions. This study attempts to improve the repair achievement and durability of concrete bridges. This investigation contains two phases: preliminary study and experimental phase. Preliminary study attends to detect different types of damages of concrete bridges and their causes along with their propagation. The next part of this study discusses about various types of repair materials. In... 

    Experimental Verification of Nonlinear Analysis of Planar Truss under Static Loading by Neuro-modelers

    , M.Sc. Thesis Sharif University of Technology Pashoutani, Sepehr (Author) ; Joghataie, Abdolreza (Supervisor)
    Abstract
    In the recent years, neural networks have been used to solve many problems in different fields, specifically in engineering problems. Neural networks have different applications in material science and structures including modeling stress-strain relationship of composite materials and static and dynamic analysis of structures. Recently, a new method called neuro-finite element has been developed for nonlinear static analysis of structures manufactured by one-dimensional elements. In this method, by investigating the load-deflection diagram of each element, it is possible to analyze and produce a load-deflection diagram for the whole structure using neural networks. This experimental study... 

    Development and Assessment of Meshfree Neural Network Based Methods for Linear and Nonlinear Static Analysis of Structures

    , M.Sc. Thesis Sharif University of Technology Ara, Kiarash (Author) ; Joghataie, Abdolreza (Supervisor)
    Abstract
    Modeling, static and dynamic analyses of structures are main subject of research and application in structural engineering. Also innovative methods gradually substitute for conventional methods in any field of science and technology. Nowadays neural networks have attracted special attention in any branch of science and engineering. Some structural engineering researchers have utilized neural networks as expert systems in field of material modeling, static and dynamic analysis, active control and etc. The neuro-finite element method is a neural network based method for linear and nonlinear static and dynamic analysis of structures with one-dimensional members. In this method neural networks... 

    Optimal control of nonlinear frames by Newmark and distributed genetic algorithms

    , Article Structural Design of Tall and Special Buildings ; Volume 21, Issue 2 , 2012 , Pages 77-95 ; 15417794 (ISSN) Joghataie, A ; Mohebbi, M ; Sharif University of Technology
    2012
    Abstract
    Active control of multi-storey frame structures with nonlinear hysteretic response has been studied in this paper. A new nonlinear optimal control algorithm based on nonlinear Newmark integration method and distributed genetic algorithm (DGA) has been developed. The objective has been to reduce the response to below any desired level. In this study, DGA has been used to determine the weights in the control law corresponding to displacement, velocity and acceleration. The capabilities of the method has been assessed through simulation where an eight-storey frame with bilinear hysteretic behaviour has been subjected to a white noise ground acceleration and controlled by the controllers... 

    Assessment of a practical technique for active control of sound using microphone and speaker

    , Article Scientia Iranica ; Volume 19, Issue 4 , 2012 , Pages 1005-1012 ; 10263098 (ISSN) Joghataie, A ; Raoufi, M ; Sharif University of Technology
    Elsevier  2012
    Abstract
    In this analytical study, it has been desired to develop a practical and simple control mechanism to control, at a given point and its neighborhood, the sound arriving from a distant source, assuming that a primary pure-tone sound pressure is propagated from a relatively far distance. The control model consists of a microphone as a sensor for measuring the sound pressure and a loud speaker for applying the control force. Corresponding equations have been developed to determine an optimum control force, and afterwards a parametric study on the factors affecting the control results has been performed. The results show that the control system can significantly reduce low frequency sound... 

    Matrix analysis of nonlinear trusses using Prandtl-2 neural networks

    , Article Journal of Sound and Vibration ; Volume 330, Issue 20 , 2011 , Pages 4813-4826 ; 0022460X (ISSN) Joghataie, A ; Farrokh, M ; Sharif University of Technology
    2011
    Abstract
    A new method, based on the concepts of matrix analysis as well as the learning capabilities of neural networks, for the analysis of nonlinear trusses under dynamic loading is presented. The method can be applied to static trusses too. While there have been attempts in the past to use neural networks to identify and model different structures based on data measured on structural response directly, the main feature and advantage of this new method is in its capability to model a nonlinear truss by assembling the data collected on the response of its members. The basics of the method are: (1) for each truss member, a neural network is trained to learn and simulate its loadresponse behavior, (2)... 

    Designing optimal controllers for nonlinear frames by considering the effect of response feedback

    , Article Scientia Iranica ; Volume 18, Issue 6 , 2011 , Pages 1170-1178 ; 10263098 (ISSN) Joghataie, A ; Mohebbi, M ; Sharif University of Technology
    2011
    Abstract
    The effect of response feedback on designing optimal controllers for nonlinear frames has been studied. Different combinations of response feedback have been used in the performance index. The Newmark based nonlinear instantaneous optimal control algorithm has been used as the control algorithm in controlling the response of an eight-story bilinear hysteretic frame subjected to white noise excitation and real earthquakes, and controlled by either eight actuators or a single actuator. While the objective has been to minimize the maximum control force for reducing the maximum drift to below the yielding level, the distributed genetic algorithm (DGA) has been used to determine the proper set of... 

    Shear Capacity of Ultra-High Performance Concrete Rectangular Beams

    , Ph.D. Dissertation Sharif University of Technology Pourbaba, Masoud (Author) ; Joghataie, Abdolreza (Supervisor)
    Abstract
    The application of ultra-high performance concrete (UHPC) as an alternative to conventional/ normal concrete (NC) has grown rapidly in recent years. However, there is limited knowledge on its shear behavior, which is essential for developing design guidelines for structural applications. A detailed parametric study was conducted on 38 beam specimens, half of which were made of UHPC and the other half made of NC. To ensure applicability of findings, two types of UHPC mixes were used, a proprietary and a generic mix. Eighteen of the beams were prepared and tested in Tabriz, Iran, while the other 20 were made and tested in Miami, FL. Test parameters included type of concrete (UHPC and NC),... 

    Improving penalty functions for structural optimization

    , Article Scientia Iranica ; Volume 16, Issue 4 A , 2009 , Pages 308-320 ; 10263098 (ISSN) Joghataie, A ; Takalloozadeh, M ; Sharif University of Technology
    2009
    Abstract
    New penalty functions, which have better convergence properties, as compared to the commonly used exterior and interior penalty functions, have been proposed in this paper. The convergence behavior and accuracy of ordinary penalty functions depend on the selection of appropriate penalty parameters. The optimization of ordinary penalty functions is accomplished after several rounds of optimization where, at each round a different but fixed value of penalty parameter is used. While some useful hints and rules for the selection of suitable penalty parameter values have been provided by different authors, the objective of this paper has been to improve this procedure by including the penalty... 

    Experimental Investigations into Damage Detection Techniques in Concrete Beams

    , M.Sc. Thesis Sharif University of Technology Shafieyoon, Amirhossein (Author) ; Joghataie, Abdolreza (Supervisor)
    Abstract
    A simply supported reinforced concrete beam has been built at the concrete laboratory of Sharif University of Technology. The cross section of the beam has been rectangular and all the reinforcing steel bars have been placed at the bottom of the beam. A progressive damage has been applied to the beam first by cutting the concrete cover and then by cutting the reinforcing bars one at a time. The beam has been tested using forced vibration test where an impact hammer has been used to apply the external load. The acceleration of the beam has been recorded based on which the FRFs and then the corresponding modal parameters have been determined. Finally natural frequencies, MAC, COMAC and mode... 

    Using Vibration Behavior Sensitivity of Beams to Damage for Detection of Damage Location and Extent

    , Ph.D. Dissertation Sharif University of Technology Banihashem, Alireza (Author) ; Joghataie, Abdolreza (Supervisor)
    Abstract
    This research is on damage detection in beams using changes in their vibration behavior with respect to damage. The aim of this research is to investigate the sensitivity of strain mode shapes to damage and the feasibility of their using in damage detection. Comparison with displacement mode shapes is another main subject of this research. For this aim, at first an experimental study has been conducted at the structures lab of Sharif University of Technology, to investigate the sensitivity of modal parameters of an Aluminum beam to progressive damage. Then a beam has been modeled numerically sing shell elements. Also a new frequency response function (FRF), here called the strain frequency... 

    Simulating dynamic plastic continuous neural networks by finite elements

    , Article IEEE Transactions on Neural Networks and Learning Systems ; Volume 25, Issue 8 , August , 2014 , Pages 1583-1587 ; ISSN: 2162237X Joghataie, A ; Torghabehi, O. O ; Sharif University of Technology
    2014
    Abstract
    We introduce dynamic plastic continuous neural network (DPCNN), which is comprised of neurons distributed in a nonlinear plastic medium where wire-like connections of neural networks are replaced with the continuous medium. We use finite element method to model the dynamic phenomenon of information processing within the DPCNNs. During the training, instead of weights, the properties of the continuous material at its different locations and some properties of neurons are modified. Input and output can be vectors and/or continuous functions over lines and/or areas. Delay and feedback from neurons to themselves and from outputs occur in the DPCNNs. We model a simple form of the DPCNN where the... 

    Reducing extent of cracks and increasing time to failure of concrete gravity dams by optimization of properties of layers of concrete

    , Article Scientia Iranica ; Vol. 21, issue. 1 , 2014 , pp. 67-81 ; ISSN: 10263098 ; e-ISSN :2345-3605 Joghataie, A ; Dizaji, M. S ; Sharif University of Technology
    2014
    Abstract
    The objective of this paper is to study the improvement in the seismic behavior of concrete gravity dams by optimization of concrete mechanical properties. The criteria to measure the improvement have been: 1) reduction in the extent of cracks and 2) increase in the amount of time dams are able to tolerate earthquakes before failure. The mechanical properties considered have included the density and modulus of elasticity of concrete. The Pine Flat Dam has been selected for this numerical study. During a high intensity earthquake, dams enter a nonlinear phase, where the cracks open and close repeatedly. A smeared crack model has been used for simulation of nonlinearity. For the purpose of...