Papers by eysa salajegheh
Civil Engineering Journal, 2019
A new intelligent hybrid method for inverse modeling (Parameter Identification) of leakage from t... more A new intelligent hybrid method for inverse modeling (Parameter Identification) of leakage from the body and foundation of earth dams considering transient flow model has been presented in this paper. The main objective is to determine the permeability in different parts of the dams using observation data. An objective function which concurrently employs time series of hydraulic heads and flow rates observations has been defined to overcome the ill-posedness issue (nonuniqueness and instability of the identified parameters). A finite element model which considers all construction phases of an earth dam has been generated and then orthogonal design, back propagation artificial neural network and Particle Swarm Optimization algorithm has been used simultaneously to perform inverse modeling. The suggested method has been used for inverse modeling of seepage in Baft dam in Kerman, Iran as a case study. Permeability coefficients of different parts of the dam have been inspected for three...
Geotechnical Research, 2018
A new combined method for the inverse modelling of leakage from the body and foundation of earth ... more A new combined method for the inverse modelling of leakage from the body and foundation of earth dams considering a transient flow model is introduced in this paper. Reaching a unique result, an objective function that simultaneously employs the time series of hydraulic heads and observations of flow rates has been defined. An inclusive finite-element model that considers all the construction stages of an earth dam has been created and then orthogonal design, back-propagation artificial neural networks and a genetic algorithm have been used to do inverse modelling. The proposed method has been employed for the inverse modelling of leakage in Baft dam in Kerman, Iran. Hydraulic conductivities of different parts of the dam have been investigated for two distinct predefined cases, and in both cases satisfactory results have been obtained. The fitting results show the applicability of the suggested method in inverse modelling of real large-scale problems, which not only decreases the co...
The present paper focuses on size optimization of scallop domes subjected to static loading. As t... more The present paper focuses on size optimization of scallop domes subjected to static loading. As this type of space structures includes a large number of the structural elements, optimum design of such structures results in efficient structural configurations. In this paper, an efficient optimization algorithm is proposed by hybridizing particle swarm optimization (PSO) algorithm and cellular automata (CA) computational strategy, denoted as enhanced particle swarm optimization (EPSO) algorithm. In the EPSO, the particles are distributed on a small dimensioned grid and the artificial evolution is evolved by a new velocity updating equation. In the new equation, the difference between the design variable vector of each site and an average vector of its neighboring sites is added to the basic velocity updating equation. This new term decreases the probability of premature convergence and therefore increases the chance of finding the global optimum or near global optima. The optimization task is achieved by taking into account linear and nonlinear responses of the structure. In the optimization process considering nonlinear behaviour, the geometrical and material nonlinearity effects are included. The numerical results demonstrate that the optimization process considering nonlinear behaviour results in more efficient structures compared with the optimization process considering linear behaviour.
Optimum design of plate structures with frequency constraints
Engineering Computations, 1997
Achieves efficient structural optimization of plate structures while the design constraints are m... more Achieves efficient structural optimization of plate structures while the design constraints are multiple frequency constraints. Reduces the computational cost of optimization by approximating the frequencies using the Rayleigh quotient. Uses an optimality criteria method to solve each of the approximate problems. The creation of a high quality approximation is the key to the efficiency of the method. Also, with the great number of design variables, the optimality criteria methods are robust approaches. Thus the combination of approximation concepts and optimality criteria methods forms the basis of an efficient tool for optimum design of plate structures with frequency constraints. Presents examples and compares the results with previous work.
Earthquake Engineering & Structural Dynamics, 2004
Optimum design of structures for earthquake is achieved by simulated annealing. To reduce the com... more Optimum design of structures for earthquake is achieved by simulated annealing. To reduce the computational work, a fast wavelet transform is used by means of which the number of points in the earthquake record is decreased. The record is decomposed into two parts. One part contains the low frequency of the record, and the other contains the high frequency of the record. The low-frequency content is the e ective part, since most of the energy of the record is contained in this part of the record. Thus, the low-frequency part of the record is used for dynamic analysis. Then, using a wavelet neural network, the dynamic responses of the structures are approximated. By such approximation, the dynamic analysis of the structure becomes unnecessary in the process of optimization. The wavelet neural networks have been employed as a general approximation tool for the time history dynamic analysis. A number of structures are designed for optimal weight and the results are compared to those corresponding to the exact dynamic analysis. Copyright ? 2004 John Wiley & Sons, Ltd.
Performance assessment of seismically-designed steel moment-resisting structures against numerically-simulated blast wave propagation
Numerical Methods in Civil Engineering
2-D Discrete Wavelet-Based Crack Detection Using Static and Dynamic Responses in Plate Structures
This paper peresents the 2–D discrete wavelet–based crack detection using static and dynamic resp... more This paper peresents the 2–D discrete wavelet–based crack detection using static and dynamic responses in plate structures. Over the last few decades, the wavelet–based techniques of damage identification methods have been presented and developed in civil and mechanical structures. The techniques are based on a comparison between the current structural responses as damaged structure and those of the previous baseline state, which is considered to be the health structure. To impliment the damage detection of plate structures, in this study the displacement, rotation and stress as the static responses and the mode shapes as the dynamic responses are considered in the crack detection procedure. The numerical results show that the wavelet–based crack detection is sensitive to number of cracks in plate structure. In other words, the existence of a crack can be potentially identified using each of the static or dynamic responses of plate structures. Moreover, if multi–cracks exists in pla...
Engineering with Computers, 2018
In this article, a new hybrid algorithm is proposed which was based on the elephant herding optim... more In this article, a new hybrid algorithm is proposed which was based on the elephant herding optimization (EHO) and cultural algorithm (CA), known as elephant herding optimization cultural (EHOC) algorithm. In this process, the belief space defined by the cultural algorithm was used to improve the standard EHO. EHO is motivated by herding behavior of the elephant groups. These behaviors are modeled into two operators including clan updating operator and separating operator. In EHOC, based on belief space, the separating operator is defined, which is able to create new local optimums in search space, to improve the algorithm search ability and to create an algorithm with an optimal exploration-exploitation balance. The CA, EHO, and EHOC algorithms are applied to eight mathematical optimization problems and four truss weight minimization problems, and to assess the performance of the proposed algorithm, the results are compared. The results clearly indicate that EHOC is capable of accelerating the convergence rate effectively and can develop better solutions compared to the CA and EHO. In addition, it can produce competitive results in comparison with other metaheuristic algorithms in the literature.
KSCE Journal of Civil Engineering, 2018
This paper presents a method for detecting damage in irregular 2D and 3D continuum structures bas... more This paper presents a method for detecting damage in irregular 2D and 3D continuum structures based on combination of wavelet with neural network. The method proposed here only requires the responses (displacements, stresses) of the damaged structures, while most damage detection methods need the structural responses before and after damage. First, the structural responses related to the damaged state are determined at the finite element points having irregular distances. Secondly, the Multiple-Layer Perceptron Neural Network (MLPNN) is used to estimate the responses at points having equal distances by those previously obtained by the finite element. Then, the extended responses are analyzed with the 2D and 3D wavelet transform in order to locate damaged zones. It is shown that detailed matrix coefficients of 2D and 3D wavelet transform can identify the damaged zone of the structure by perturbation in the damaged area. In order to assess the performance of the proposed method, some numerical examples are considered. The results show the high efficiency of the method for damage localization of the structure.
Optimum Shape Design of Space Structures by Genetic Algorithm
International Journal of Space Structures, 2009
Space structures are usually highly indeterminate and therefore have a large number of redundant ... more Space structures are usually highly indeterminate and therefore have a large number of redundant members. It is important to choose the appropriate number of elements and joints for the structure under consideration. Optimum shape design of space structures is the aim of the present work and to achieve an optimal configuration, parameters such as number of joints, number of members, support conditions and the overall shape of the structures are considered. To attain a practical configuration, the presence of the joints of the structures and the locations of the columns are taken as the shape design variables as well as the cross-sectional area of the elements of the structures under considerations. The resulting configurations are very interesting after the removal of unnecessary joints and columns. It was also observed that a part of sphere might not be appropriate for the dome structures as usually chosen by the designers. For different static loading conditions that presented in ...
Proceedings of the Eleventh International Conference on Computational Structures Technology
This paper deals with the evaluation of seismic behaviour of reinforced concrete moment resistant... more This paper deals with the evaluation of seismic behaviour of reinforced concrete moment resistant frames (RC-MRFs) considering soil-structure interaction (SSI) effects. In this study, a three-bay nine-storey RC-MRF is optimally designed based on the design codes recommendations. To investigate the SSI effects on the seismic behaviour of the frame, a direct method is used for the modelling of SSI system. Six ground motion records are used; and the seismic behaviour of the SSI system is compared with those of RC-MRF without the SSI effects. To achieve this purpose, hysteretic energy demand and inelastic inter-story drift ratio over the height of structure are considered as the comparison criterion.
Bridge Health Monitoring Using Two Stage Neural Networks
In this paper a method for damage identification in bridges employing neural networks is presente... more In this paper a method for damage identification in bridges employing neural networks is presented. In this work, in order to increase the speed and reduce the computational error for damage detection a new two stage method is introduced. In the first stage the damages are localized using a radial basis function neural network which has the benefit of high learning speed. In the second stage, the exact location and severity of damaged elements found using a well-trained back propagation neural network which possesses high powerful learning capacity. In order to evaluate the proposed method Louisville truss bridge in United States of America is modeled by a finite element program and then changes in the responses is analyzed using MATLAB neural networks toolbox. Numerical results demonstrate the efficiency of the proposed method for correct damage identification.
Optimal Desigin of Structures with Frequency Constraints Using Wavelet Back Propagation Neural
Asian Journal of Civil Engineering
A combination of improved genetic algorithm and neural networks is proposed to find the optimal w... more A combination of improved genetic algorithm and neural networks is proposed to find the optimal weight of structures subject to multiple natural frequency constraints. The structural optimization is carried out by an evolutionary algorithm employing the discrete design variables. To reduce the computational time of the optimization process, the natural frequencies of structures are evaluated by using properly trained back propagation (BP) and wavelet back propagation (WBP) neural networks. The numerical results reveal the robustness and high performance of the suggested methods for the structural optimization with frequency constraints. It is found that the best results are obtained using WBP network.
Reliability-based seismic assessment of asymetric multi-storey buildings with RC shear walls
ABSTRACT The performance of buildings subjected to earthquake loads has shown that asymmetric str... more ABSTRACT The performance of buildings subjected to earthquake loads has shown that asymmetric structures are caused more extensive damages in comparison with symmetric structures. Hence, the seismic performance of asymmetric structures should be assessed due to future random earthquakes. Reliability-based seismic assessment as one of the tools in performance-based earthquake engineering has been introduced to quantify the seismic reliability for existing structures due to future random earthquakes. This paper deals with the reliability-based seismic assessment of asymmetric multi-storey buildings with RC shear walls with consideration of the angle of ground motion incidence. To implement this purpose, in the first stage, the multi-component incremental dynamic analysis (MIDA) is used for the assessment of asymmetric 6 and 9-storey buildings with RC walls. The MIDA as an efficient procedure can estimate the seismic capacity of a structural system with randomness on incident angle. In the second stage, the mean annual frequency exceeding of a specified level of structural demand is calculated to predict the reliability of these structures. The results show that the effects of earthquake incident angle should be considered in the assessment of the assessment of asymmetric multi-storey building.
International Journal of Space Structures, 2008
Optimum design of a socket type joint for space structures is achieved by numerical optimisation ... more Optimum design of a socket type joint for space structures is achieved by numerical optimisation techniques. The weight of the joint is considered as the objective function and the design variables are the mean radius and thickness of the joint. The design constraints are taken as the applied loads not allowed to exceed the ultimate bearing capacity of the joint as well as some geometric requirements. The structural analysis is carried out by a finite element program employing elasto-plastic analysis. To verify the analysis due to various assumptions, the results are compared with some available experimental results. By incorporating the analysis program with a numerical optimisation method, the optimal values of variables are achieved while all the constrains are satisfied. In order to reduce the computational burden of the optimisation process a number of first and second order approximation concepts are presented. Thus, the lengthy non-linear analysis is not needed for the optimisation process in the specified move limits.
Hybridizing two-stage meta-heuristic optimization model with weighted least squares support vector machine for optimal shape of double-arch dams
Applied Soft Computing, 2015
ABSTRACT A two-stage meta-heuristic optimization model is introduced to find the optimal shape of... more ABSTRACT A two-stage meta-heuristic optimization model is introduced to find the optimal shape of double-arch concrete dams. The main aim is that computational merits of the continuous ant colony optimization (ACOR) and the particle swarm optimization (PSO) be integrated. This proposed method called ACOR–PSO can accelerate the capability of exploitation and convergence of PSO. To achieve this, a preliminary optimization is accomplished using ACOR in the first stage of ACOR–PSO. In the second phase ACOR–PSO, PSO is utilized by using the optimal initial swarm of the first phase results. The weighted least squares support vector machine (WLS-SVM) is considered as the most reliable method for predicting the dynamic responses of dams. To testify the robustness and efficiency of the proposed ACOR–PSO, first, the well-known benchmark functions in literatures are optimized using the proposed ACOR–PSO, and provides comparisons with ACOR and PSO. Then, a real world double-arch dam is presented to demonstrate the effectiveness and practicality of the ACOR–PSO. The numerical results reveal that ACOR–PSO not only converges to better solutions but also provides faster convergence rate in comparison with ACOR and PSO.
Journal of Constructional Steel Research, 2010
The main aim of this study is to propose advanced soft computing techniques for the optimal seism... more The main aim of this study is to propose advanced soft computing techniques for the optimal seismic design of real steel structures subjected to natural ground motion records. For the solution of the optimization problem an efficient combination of the particle swarm optimization (PSO) and adaptive virtual sub-population (AVSP) algorithms is proposed. Also an efficient combination of the adaptive neuro-fuzzy inference system (ANFIS), wavelet transforms (WT) and radial basis function (RBF) neural networks, termed as fuzzy wavelet radial basis function (FWRBF), is proposed to accurately predict the structural responses. The numerical results demonstrate the computational advantages of the proposed methodology.
Efficient Methods for Structural Optimization with Frequency Constraints Using Higher Order Approximations
International Journal of Structural Stability and Dynamics, 2008
Presented herein are four different methods for the optimum design of structures subject to multi... more Presented herein are four different methods for the optimum design of structures subject to multiple natural frequency constraints. During the optimization process the optimum cross-sectional dimensions of elements are determined. These methods are robust and efficient in terms of the number of eigenvalue analyses required, as well as the overall computational time for the optimum design. A new third order approximate function is presented for the structural response quantities, as functions of the cross-sectional properties, and four different methods for the optimum design are defined based on this approximate function. The main features of the proposed function are that only the diagonal terms of higher order derivative matrices are employed, and these derivatives are established by the available first order derivatives. The first order exact derivatives are obtained from a sensitivity analysis at the previous design points. We show that this approximate function creates high qua...
Elaborate Structural Damage Detection Using an Improved Genetic Algorithm and Modal Data
International Journal of Structural Stability and Dynamics, 2013
This paper addresses a proficient strategy for detection of structural damages in details using t... more This paper addresses a proficient strategy for detection of structural damages in details using the variations of eigenvalues and eigenvectors. There are two concerns in this study. First, the severity of damage can vary within the damaged elements; second, it is possible that the damage extents do not exactly match the pre-generated finite element mesh. The first concern forms the motivation for employing the proper damage functions to model the elemental damages, and the second for considering the nodal positions as design variables. To obtain the design variables, an improved genetic algorithm is introduced in which two new operators are embedded. This strategy is applied to a beam and a plate structure as the cases of study. The results demonstrate the applicability and efficiency of the proposed algorithm in elaborate damage detections.
Engineering Optimization, 2009
An efficient methodology is proposed to find the optimum shape of arch dams considering fluid-str... more An efficient methodology is proposed to find the optimum shape of arch dams considering fluid-structure interaction subject to earthquake loading. The earthquake load is considered by time variant ground acceleration applied in the upstream-downstream direction of the arch dam. The optimization is carried out by particle swarm optimization, employing real values of design variables. To reduce the computational cost of the optimization process, two strategies are adopted. In the first strategy, the most influential design variables on arch-dam response from original variables are selected using an adaptive neuro-fuzzy inference system. In the second, arch-dam response is predicted by a properly trained wavelet radial basis function neural network employing the influential design variables as the inputs. In order to assess the effectiveness of the suggested methodology, a real arch dam is considered as a test example. The numerical results demonstrate the computational advantages of the proposed methodology for the optimal design of arch dams.
Uploads
Papers by eysa salajegheh