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As a first attempt, finite element (FE), genetic algorithm (GA) and particle swarm optimization (PSO) methods are mixed to maximize buckling load of stiffened laminated composite plate via finding optimum fibers orientation of the plate. The FE method is used to solve the higher-order shear deformation based equations of the plate. To improve the performance of genetic algorithms for solving the problem, the particle swarm optimization technique is added as an operator of the GA. Accuracy, convergence and applicability of the proposed approach are shown. Effects of the dimensions of the plate, the cross section shapes of the stiffener(s), number of layers of the plate and boundary conditions on the optimum results are investigated. [ABSTRACT FROM AUTHOR]

As a first attempt, optimum stacking sequences of thick laminated composite plate is obtained to maximize its buckling load via employing the finite element (FE), genetic algorithms (GAs) and particle swarm optimization (PSO) methods. The higher-order shear deformation theory (HSDT) is used to obtain governing equations of the plate. The finite element method (FEM) is employed to solve these equations and to gain buckling load of the plate. The FEM solution is linked with a developed optimization algorithm which is a mix of genetic algorithms (GAs) and particle swarm optimization (PSO) techniques. Some examples are solved to show applicability and usefulness of the proposed hybrid method for maximizing buckling load of the plate via finding optimum stacking sequences of the plate. Also, influences of different parameters on the optimum stacking sequences of the thick plate are studied. [ABSTRACT FROM AUTHOR]

As a first attempt, a combined method is introduced to obtain maximum fundamental frequency of thick laminated composite plates via finding optimum fibers orientation. The governing equations are obtained based on the higher order shear deformation theory (HSDT). The robust and accurate finite element method (FEM) is used to discretize the governing equations. The transferred form of the equations in frequency domain is obtained and the fundamental frequency of the plate is achieved. High sensitivity of the problem with the fibers orientations is shown. To find the optimum fibers orientation of the thick plate a mixed implementable evolutionary algorithm is used. In the proposed genetic algorithms (GAs) base method, particle swarm optimization (PSO) method is added to improve specified percent of GAs population. Applicability and usefulness of the method is demonstrated by solving different examples. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid method for simultaneously maximizing fundamental natural frequency and thermal buckling temperature of laminated composite plates is developed. This method is a new combination of the differential quadrature method (DQM), non-dominated sorting genetic algorithm II (NSGA-II) and Young bargaining model. The governing equations are obtained within the framework of the first-order shear deformation theory (FSDT) of plates and are discretized using the DQM. Then, the DQM is linked with the NSGA-II optimization model and the trade-off between the objectives with respect to fibers orientations is obtained. Finally, by applying Young bargaining model the best fibers orientations which maximize the objectives of laminated composite plates with different boundary conditions, thickness-to-length and aspect ratios are obtained. [ABSTRACT FROM AUTHOR]

A new hybrid method for damage detection of laminated composite beams is presented. Based on first-order shear deformation theory (FSDT) the governing equations of the beam are obtained. Finite element method is adopted to discretize the equations. Considering damaged element(s) frequencies of the damaged beam are calculated. Considering the frequencies as a measured data, the proposed optimization technique is applied to detect the element(s). In the method, a continuous genetic algorithm (CGA) is improved by sensitivity modal analysis and particle swarm optimization (PSO) techniques. The added PSO and the sensitivity analysis operators improve the generated population before and after CGA, respectively in conjunction with an embedded micro search operation in genetic algorithm to reduce the search space. Applicability, efficiency and robustness of the proposed algorithm in detecting the location and extent of damages in presence and absence of the PSO optimization method for different examples are demonstrated. [ABSTRACT FROM AUTHOR]

Thermal buckling and postbuckling analysis of functionally graded (FG) beams is presented. The governing equations are based on the first-order shear deformation beam theory (FSDT) and the geometrical nonlinearity is modeled using Green's strain tensor in conjunction with the von Karman assumptions. For discretizing the governing equations and the related boundary conditions differential quadrature method (DQM) as a simple and computationally efficient numerical tool is used. Based on displacement control method, a direct iterative method is employed to obtain thermal postbuckling behavior of FG beams with different boundary conditions and geometrical parameters. [ABSTRACT FROM AUTHOR]

Abstract: As a first endeavor, a hybrid finite element (FE)–incremental differential quadrature (IDQ) method together with the discrepancy principle and the conjugate gradient method (CGM) is used to develop an inverse algorithm for the parameters estimation of the axisymmetric multilayered half-spaces. The approach is based on the measurement of the dynamic transverse displacement at some boundary points of the half-space to estimate the unknown parameters of its layers. Using the accuracy and unconditional stability of the hybrid FE–IDQ method, the direct problem is solved to get the dynamic transverse displacements. After adding some random errors to the obtained results, they are considered as the measured responses by sensors. Then, the conjugate gradient method as a general and robustness optimization technique is employed to minimize the error between the measured and calculated dynamic surface responses at sensor locations. The sensitivity analysis of the displacement field is performed using a semi-analytical method. The applicability and correctness of the proposed hybrid algorithm is demonstrated through different examples by considering the influence of the layers arrangement, the measurement errors and sensor numbers. [Copyright &y& Elsevier]

Abstract: Dynamic response of moderately thick antisymmetric cross-ply laminated rectangular plates on elastic foundation is investigated. The governing equations are based on the higher order shear deformation theory (HSDT). Two-parameter elastic foundation (Pasternak type) is considered. Modal analysis in conjunction with the incremental differential quadrature method (IDQM), as an efficient and stable numerical tool for temporal domain discretization, are employed to solve the governing differential equations. Much lower computational time of the DQM with respect to Newmark’s method is exhibited. The convergence of the method is demonstrated and its accuracy is shown by comparing the results with those of exact solution for thin plate obtained using the classical plate theory (CPT). Also, comparison between the results of different theories, i.e. the classical thin plate theory (CPT), the first order shear deformation theory (FSDT) and the higher order shear deformation theory (HSDT), is made. The effects of different parameters on dynamic response of the antisymmetric cross-ply plates are studied. The results can be used as benchmark solution for future works. [Copyright &y& Elsevier]

Abstract: The thermal buckling and postbuckling analysis of laminated composite beams with temperature-dependent material properties is presented. The governing equations are based on the first-order shear deformation beam theory (FSDT) and the geometrical nonlinearity is modeled using Green''s strain tensor in conjunction with the von Karman assumptions. The differential quadrature method (DQM) as an accurate, simple and computationally efficient numerical tool is adopted to discretize the governing equations and the related boundary conditions. A direct iterative method is employed to obtain the critical temperature (bifurcation point) as well as the nonlinear equilibrium path (the postbuckling behavior) of symmetrically laminated beams. The applicability, rapid rate of convergence and high accuracy of the method are established via different examples and by comparing the results with those of existing in literature. Then, the effects of temperature dependence of the material properties, boundary conditions, length-to-thickness ratios, number of layers and ply angle on the thermal buckling and postbuckling characteristic of symmetrically laminated beams are investigated. [Copyright &y& Elsevier]

Abstract: Thermal postbuckling and consequently, the role of temperature dependence of material properties on the thermal postbuckling behavior of laminated composite skew plates have not been addressed in literature. Hence, this problem is investigated here. The plate governing equations are based on the first-order shear deformation theory (FSDT) and the geometrical nonlinearity is modeled using Green’s strain tensor in conjunction with the von Karman assumptions. Since the problem is geometrically and physically nonlinear, the differential quadrature method (DQM) as an accurate, simple and computationally efficient numerical tool is adopted to discretize the governing equations and the related boundary conditions. Then, a direct iterative method is employed to obtain the critical temperature (bifurcation point) and consequently the nonlinear equilibrium path (the postbuckling behavior) of symmetrically laminated skew plates. After validating the formulation and the method of solution, the effects of temperature dependence of the material properties on the postbuckling characteristic of laminated skew plates with different skew angle, boundary conditions, length-to-thickness ratio, number of layers and ply layout are investigated. [Copyright &y& Elsevier]

A new strategy is proposed to find optimal fibers orientation of stiffened laminated composite panels to reach their maximum buckling load. To do so, buckling analysis of laminated stiffened composite panel is performed by using the ABAQUS software. A new hybrid algorithm based on the particle swarm optimization (PSO) and genetic algorithm (GA) is introduced for the optimization purpose. The conventional PSO method is improved by introducing a new inertia weight of velocity in the formulation. The validity of the proposed modeling technique is controlled by comparing the modeling results with that of experiment, and other previously published models and a satisfactory result has been achieved. Also, it has been found that the proposed optimization method has better performance than the existing methods, in terms of convergence speed and the accuracy of the algorithm. Moreover, the effects of shape of stiffeners, number of panel layers, curvature of panel, and boundary conditions on the optimal design are investigated. • Buckling load optimization of stiffened laminated composite panels is studied. • An improved PSO-GA optimization technique is introduced. • A new inertia weight for the PSO is proposed. • Mix of the FEM and developed evolutionary optimization technique is proposed. • Influences of different parameters on the optimal results are investigated. [ABSTRACT FROM AUTHOR]

Design optimization of moderately thick hexagonal honeycomb sandwich plate has been investigated via employing an improved multi-objective particle swarm optimization with genetic algorithm (MOPSOGA). Based on the first-order shear deformation theory (FSDT), governing equations of the plate are obtained. The equations are solved analytically. Total weight and maximum deflection of the plate under static gravity loads are considered to be objective functions of the problem. Core height, faces thickness, cell walls thickness, vertical and inclined cell wall length and the angle between inclined cell wall and horizontal line are set to be design variables of the problem. The geometrical and failure constrains are chosen to have desirable performance and stability of the sandwich plate. In the used multi-objective optimization technique, the optimum velocity parameter, inertia weight and acceleration coefficients for next iteration of the MOPSO are obtained by employing the genetic algorithm via minimizing generational distance between the sets of dominated and non-dominated particles in the previous iteration. Efficiency and accuracy of the proposed solution procedure are demonstrated and effects of different parameters on design optimization of the plate are studied. Also, TOPSIS multi-criteria decision-making method has been selected to report appreciate results from the Pareto-front curve of the MOPSOGA. [ABSTRACT FROM AUTHOR]

Curved steel damper is an innovative energy dissipation device for seismic application. The performance of the curved steel damper has been well studied and experimentally tested. In addition, the behavior of one story curved damper semi-rigid frame (CDSRMF) has been studied extensively. In this study, the seismic performance of multi-story (3 story, 6 story and 9 story) CDSRMFs are extensively examined using nonlinear static (pushover analysis) and nonlinear dynamic analysis. The results show that the addition of the curved damper has significantly improved the stiffness, strengths and energy dissipation of the CDSRMFs. The formation and distribution of plastic hinges in CDSRMFs show that the significant part of nonlinear deformations is concentrated in curved damper elements instead of the primary elements. The curved damper can be used as a robust structural fuse which can be efficiently inspected and replaced as needed. The results demonstrate that multistory CDSRMF can be used as a reliable and resilient seismic force resisting systems. [Display omitted] • The numerical investigation of the curved damper on multi-story steel structures has been done. • 2 different design approaches have been considered in design and implementation of the curved dampers to get the best outcome. • The curved damper, as well as the CDSRMF system, were validated with experimental results in OpenSees. • The propsoed element can behave as a resilient passive damper for building structures in the regions of moderate to high seismicity. [ABSTRACT FROM AUTHOR]

• Introduction of a new structural system called curved damper truss moment frame. • Benefiting from a two-phased energy dissipation system, primary and secondary fuses. • The Equivalent energy design procedure is used to design three- and nine-story prototypes. • The performance of the CDTMF system is evaluated via Pushover, NTHA and IDA. Curved damper truss moment frame (CDTMF) system is a novel seismic force-resisting structural system which utilizes the curved dampers integrated into a semi-rigid moment frame to dissipate the earthquake input energy. To ensure the CDTMF has high performance, the state-of the art equivalent energy design procedure (EEDP) is applied to its design. EEDP allows engineers to design CDTMF to achieve different performance objectives at different levels of earthquake shaking intensities. In this study, two different prototype buildings (three and nine-story) were designed using EEDP. The seismic performance of the buildings was assessed using nonlinear time history analysis (NTHA) and incremental dynamic analysis (IDA). The results of the nonlinear dynamic analyses demonstrate that the CDTMFs can achieve the predefined performance targets (selected by the designer) at different earthquake intensity levels. The results of the IDA also show that the EEDP designed CDTMF has a sufficient margin against collapse. The results of this study in general confirm that CDTMF can be used as an effective seismic force-resisting system. [ABSTRACT FROM AUTHOR]