Approximate discrete variable optimization of plate structures using dual methods

Salajegheh, Eysa Techno-Press 1995 Structural Engineering and Mechanics, An Int'l Jou Vol.3 No.4

This study presents an efficient method for optimum design of plate and shell structures, when the design variables are continuous or discrete. Both sizing and shape design variables are considered. First the structural responses such as element forces are approximated in terms of some intermediate variables. By substituting these approximate relations into the original design problem, an explicit nonlinear approximate design task with high quality approximation is achieved. This problem with continuous variables, can be solved by means of numerical optimization techniques very efficiently, the results of which are then used for discrete variable optimization. Now, the approximate problem is converted into a sequence of second level approximation problems of separable form and each of which is solved by a dual strategy with discrete design variables. The approach is efficient in terms of the number of required structural analyses, as well as the overall computational cost of optimization. Examples are offered and compared with other methods to demonstrate the features of the proposed method.

Utilizing Fiber Reinforced Concrete as the Concrete Face of Rockfill Dams

Payam Salajegheh,Ghassem Habibagahi,S. Mohammad Sadegh Sahraeian 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.3

Construction of concrete faced rockfill dams (CFRD) includes pouring rock materials as the main body of the dam and compacting the rockfill to an acceptable compaction level. Then, a reinforced concrete slab is constructed on the upstream surface of dam to transfer water pressure to the rockfill materials. Considering the high permeability of rockfill materials, the concrete slab serves as a sealing element on the upstream side. Indeed, the required characteristics of concrete face are adequate flexibility in case of long-term settlement of dam, durability and its sufficiency in waterproofing the dam. In this study, to improve the quality of concrete face, increase its flexibility, optimize the construction cost and enhance the bearing capacity of concrete in tension, developed by bending moment in the face slab, three types of prevalent fibers (polypropylene, MEXO200 and steel) are utilized. The performance of each fiber is compared with the conventional reinforced concrete specimens by conducting some bending tests. Furthermore, carrying out numerical simulation, the efficacy of each fiber on performance of face slab is investigated. Based on the results, the fibers, especially the steel fibers, are suitable to substitute rebars of the conventional reinforced concrete employed as the concrete face of CFRDs. The steel fiber reinforced concrete has adequate capacity and ductility to mitigate the expected deformations from reservoir loading on the upstream face of CFRDs.

Damage detection technique for irregular continuum structures using wavelet transform and fuzzy inference system optimized by particle swarm optimization

Hamidian, Davood,Salajegheh, Eysa,Salajegheh, Javad Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.5

This paper presents a method for detecting damage in irregular 2D and 3D continuum structures based on combination of wavelet transform (WT) with fuzzy inference system (FIS) and particle swarm optimization (PSO). Many damage detection methods study regular structures. This method studies irregular structures and doesn't need response of healthy structures. First the damaged structure is analyzed with finite element methods, and damage response is obtained at the finite element points that have irregular distance, secondly the FIS, which is optimized by PSO is used to obtain responses at points, having equal distance by response at those points that previously obtained by the finite element methods. Then a 2D (for 2D continuum structures) or a 3D (for 3D continuum structures) matrix is performed by equal distance point response. Thirdly, by applying 2D or 3D wavelet transform on 2D or 3D matrix that previously obtained by FIS detail matrix coefficient of WT is obtained. It is shown that detail matrix coefficient can determine the damage zone of the structure by perturbation in the damaged area. In order to illustrate the capability of proposed method some examples are considered.

Irregular Continuum Structures Damage Detection based on Wavelet Transform and Neural Network

Davood Hamidian,Eysa Salajegheh,Javad Salajegheh 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.11

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.

Damage detection technique for irregular continuum structures using wavelet transform and fuzzy inference systemoptimized by particle swarm optimization

Davood Hamidian,Eysa Salajegheh,Javad Salajegheh 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.5

This paper presents a method for detecting damage in irregular 2D and 3D continuum structures based on combination of wavelet transform (WT) with fuzzy inference system (FIS) and particle swarm optimization (PSO). Many damage detection methods study regular structures. This method studies irregular structures and doesn’t need response of healthy structures. First the damaged structure is analyzed with finite element methods, and damage response is obtained at the finite element points that have irregular distance, secondly the FIS, which is optimized by PSO is used to obtain responses at points, having equal distance by response at those points that previously obtained by the finite element methods. Then a 2D (for 2D continuum structures) or a 3D (for 3D continuum structures) matrix is performed by equal distance point response. Thirdly, by applying 2D or 3D wavelet transform on 2D or 3D matrix that previously obtained by FIS detail matrix coefficient of WT is obtained. It is shown that detail matrix coefficient can determine the damage zone of the structure by perturbation in the damaged area. In order to illustrate the capability of proposed method some examples are considered.

Performance evaluation of wavelet and curvelet transforms based-damage detection of defect types in plate structures

Ali R. Hajizadeh,Javad Salajegheh,Eysa Salajegheh 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.60 No.4

This study focuses on the damage detection of defect types in plate structures based on wavelet transform (WT) and curvelet transform (CT). In particular, for damage detection of structures these transforms have been developed since the last few years. In recent years, the CT approach has been also introduced in an attempt to overcome inherent limitations of traditional multi-scale representations such as wavelets. In this study, the performance of CT is compared with WT in order to demonstrate the capability of WT and CT in detection of defect types in plate structures. To achieve this purpose, the damage detection of defect types through defect shape in rectangular plate is investigated. By using the first mode shape of plate structure and the distribution of the coefficients of the transforms, the damage existence, the defect location and the approximate shape of defect are detected. Moreover, the accuracy and performance generality of the transforms are verified through using experimental modal data of a plate.

Optimum design of steel framed structures including determination of the best position of columns

P. Torkzadeh,J. Salajegheh,E. Salajegheh 국제구조공학회 2008 Steel and Composite Structures, An International J Vol.8 No.5

In the present study, an efficient method for the optimum design of three-dimensional (3D) steel framed structures is proposed. In this method, in addition to choosing the best position of columns based on architectural requirements, the optimum cross-sectional dimensions of elements are determined. The preliminary design variables are considered as the number of columns in structural plan, which are determined by a direct optimization method suitable for discrete variables, without requiring the evaluation of derivatives. After forming the geometry of structure, the main variables of the cross-sectional dimensions are evaluated, which satisfy the design constraints and also achieve the least-weight of the structure. To reduce the number of finite element analyses and the overall computational time, a new third order approximate function is introduced which employs only the diagonal elements of the higher order derivatives matrices. This function produces a high quality approximation and also, a robust optimization process. The main feature of the proposed technique is that the higher order derivatives are established by the first order exact derivatives. Several examples are solved and efficiency of the new approximation method and also, the proposed method for the best position of columns in 3D steel framed structures is discussed.

An approach for optimal sensor placement based on principal component analysis and sensitivity analysis under uncertainty conditions

Beygzadeh, Sahar,Torkzadeh, Peyman,Salajegheh, Eysa Techno-Press 2022 Structural monitoring and maintenance Vol.9 No.1

In the present study, the objective is to detect the structural damages using the responses obtained from the sensors at the optimal location under uncertainty conditions. Reducing the error rate in damage detection process due to responses' noise is an important goal in this study. In the proposed algorithm for optimal sensor placement, the noise of responses recorded from the sensors is initially reduced using the principal component analysis. Afterward, the optimal sensor placement is obtained by the damage detection equation based sensitivity analysis. The sensors are placed on degrees of freedom corresponding to the minimum error rate in structural damage detection through this procedure. The efficiency of the proposed method is studied on a truss bridge, a space dome, a double-layer grid as well as a three-story experimental frame structure and the results are compared. Moreover, the performance of the suggested method is compared with three other algorithms of Average Driving Point Residue (ADPR), Effective Independence (EI) method, and a mass weighting version of EI. In the examples, young's modulus, density, and cross-sectional areas of the elements are considered as uncertainty parameters. Ultimately, the results have demonstrated that the presented algorithm under uncertainty conditions represents a high accuracy to obtain the optimal sensor placement in the structures.

Optimum seismic design of reinforced concrete frame structures

Sadjad Gharehbaghi,Abbas Moustafa,Eysa Salajegheh 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.17 No.6

This paper proposes an automated procedure for optimum seismic design of reinforced concrete (RC) frame structures. This procedure combines a smart pre-processing using a Tree Classification Method (TCM) and a nonlinear optimization technique. First, the TCM automatically creates sections database and assigns sections to structural members. Subsequently, a real valued model of Particle Swarm Optimization (PSO) algorithm is employed in solving the optimization problem. Numerical examples on design optimization of three low- to high-rise RC frame structures under earthquake loads are presented with and without considering strong column-weak beam (SCWB) constraint. Results demonstrate the effectiveness of the TCMin seismic design optimization of the structures.

A two-stage structural damage detection method using dynamic responses based on Kalman filter and particle swarm optimization

Sahar Beygzadeh,Peyman Torkzadeh,Eysa Salajegheh 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.5

To solve the problem of detecting structural damage, a two-stage method using the Kalman filter and Particle Swarm Optimization (PSO) is proposed. In this method, the first PSO population is enhanced using the Kalman filter method based on dynamic responses. Due to noise in the sensor responses and errors in the damage detection process, the accuracy of the damage detection process is reduced. This method proposes a novel approach for solve this problem by integrating the Kalman filter and sensitivity analysis. In the Kalman filter, an approximate damage equation is considered as the equation of state and the damage detection equation based on sensitivity analysis is considered as the observation equation. The first population of PSO are the random damage scenarios. These damage scenarios are estimated using a step of the Kalman filter. The results of this stage are then used to detect the exact location of the damage and its severity with the PSO algorithm. The efficiency of the proposed method is investigated using three numerical examples: a 31-element planer truss, a 52-element space dome, and a 56-element space truss. In these examples, damage is detected for several scenarios in two states: using the no noise responses and using the noisy responses. The results show that the precision and efficiency of the proposed method are appropriate in structural damage detection.