فهرست مطالب

Asian journal of civil engineering - Volume:16 Issue:5, 2015
  • Volume:16 Issue:5, 2015
  • تاریخ انتشار: 1394/02/26
  • تعداد عناوین: 8
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  • B. Dizangian, M.R. Ghasemi* Pages 567-585
    Maybe it is reasonable that in optimization problems based on sensitivity analysis one could reach the vicinity of the optimum point with a minor number of analyzes. Besides, it is also fair to accept the fact that the optimum point activates at least one constraint in constrained optimization problems. Based on these concepts a new method is proposed in the present study. It utilizes four well-organized operators to reach the global optimum solution; ordered by first a Subspace Search (SS) operator that transforms the whole design space into a series of subspaces in order to rapidly reach the Feasible-Non-Feasible (FNF) margin at the early stages by doing a few number of analyzes. It is then followed by a Marginal Sensitivity Analysis (MSA) operator that determines the sensitivity degree of each design variable to constraints violation, near the margin of FNF region. Next, the Marginal Search (MS) operator is used to determine a local optimum point near the FNF border in the feasible region. Finally, the roulette wheel (RW) operator is employed to select, in a random manner, only one variable for updating in each iteration. The robustness and effectiveness of the proposed method is verified on several well-known benchmark truss examples. The results show that the proposed method not only speeds up the optimization procedure, but also it ensures the non-violated global optimum design point without a need for multiple runs.
    Keywords: Marginal, feasibility search, size optimization, truss structures
  • A. Kaveh*, S. Pirgholizadeh, O. Khadem Hosseini Pages 587-606
    Structural profitable control is a subject of the recent challenges in designing of various mechanical systems. Recently, semi-active tuned mass dampers (SATMD) developed to attenuate vibration of building structures due to the external disturbances. In this paper, a mass damper that works parallel with a semi-active magneto-rheological (MR) damper employed to reduce a ten story building structure responses in four earthquake excitations. An optimized fuzzy controller by using charged system search (CSS) algorithm calculates proper input voltage of the MR damper to increase performance of the SATMD in reducing vibration of the building structure. The results showed better performance of the optimized fuzzy controller in comparison with conventional fuzzy controllers and passive TMD.
    Keywords: Optimized fuzzy controller, semi, active tuned mass damper, charged system search algorithm (CSS)
  • N. Moshiri*, D. Mostofinejad Pages 607-620
    In the present research, carbon fiber reinforce polymer (CFRP) composite with fibers aligned along the column axis was used to strengthen the RC columns. A newly introduced method named as grooving method (GM) was utilized to improve the compressive behavior of longitudinal FRP and postpone the buckling and delamination of longitudinal composite from concrete substrate. Two techniques of GM, i.e. externally bonded reinforcement on grooves (EBROG, to be pronounced as /ebrΛg/) and externally bonded reinforcement in grooves (EBRIG, to be pronounced as /ebrIg/) was used, as well as EBR method, to strengthen the column specimens. For this purpose, 11 RC column specimens with circular section of 150 mm diameter and height of 500 mm were tested under uniaxial compression. Experimental results showed that using the grooving method in strengthening the column specimen, significantly increased the load carrying capacity of specimens; while the conventional EBR method showed inconsiderable effects on the load capacity. The results demonstrated that utilizing EBROG and EBRIG techniques led to respectively 14.1% and 18.5% increase in the column maximum load. However, the column strengthened with EBR method indicated only 2.6% increase in the load carrying capacity.
    Keywords: Compressive load carrying capacity, CFRP, grooving method (GM), buckling, EBROG, EBRIG
  • K. Laknejadi*, A. Kaveh Pages 621-649
    In this paper a swarm based version of the M-PAES is proposed to solve structural design optimization problems with high number of design variables. The M-PAES is a well-known memetic evolutionary algorithm for multi-objective optimization. In the present algorithm, all the produced individuals in each local search phase of the M-PAES are stored in a swarm and then search process is conducted using the provided information by members of the swarm. In other words, the obtained fitness function of all the individuals in a swarm, gives an approximation of the gradient of that limited area of the search space in which the swarm is located. Then this vector is utilized to guide the next cycle of individual creation in the process of local search. Additionally, in order to escape from getting stuck in local Pareto optimums, a combination of random and directed search is employed. Furthermore, in the present algorithm, the crossover process is performed by differential evolution (DE) algorithm, where each new individual gains its characteristics from three parents, the feature that provides a powerful global search ability for the algorithm. Finally, we present some numerical results on three sets of problems, indicating the strength of the idea employed in the proposed algorithm.
    Keywords: SM, PAES, evolutionary algorithm, multi, objective optimization, large structures
  • N. Ganesan, Ruby Abraham, S. Deepa Raj Pages 651-662
    In this experimental study the strength and behaviour of plain and fibre reinforced Geopolymer concrete (GPC) columns under repeated axial compression were evaluated. A total of fifteen GPC square columns of size 150 mm and length 900 mm were cast and tested to evaluate the performance. The main variable considered in this study is the volume fraction of fibres such as 0.25% (19.62 kg/m3), 0.5% (39.24 kg/m3), 0.75% (58.86 kg/m3) and 1% (78.48 kg/m3). Experimental results revealed that addition of steel fibres slightly improved the axial strength and significantly improved the stress-strain behaviour and ductility of columns. For a better understanding of the stress and strain behaviour of column a finite element model for both plain and fibre reinforced GPC column was developed using standard finite element software (ANSYS 11.) and was found to compare satisfactorily with the experimental results.
    Keywords: Axial strength ratio, geopolymer concrete, ductility, fibre, stress, strain behaviour
  • S. Gholizadeh*, F. Fattahi Pages 663-679
    The main aim of this study is to propose an efficient computational strategy for optimization of steel structures subject to earthquake loading. To achieve the optimization task, two popular metaheuristics and the newly developed grey wolf algorithm (GWA) are employed. To reduce the computational burden of the process, radial basis function (RBF) and back propagation (BP) neural networks are used for evaluation the seismic responses of structures subject to three earthquakes. The numerical results show that GWA incorporating BP neural network provides the best results in comparison with the other ones.
    Keywords: Optimization, metaheuristic, earthquake, time history analysis, steel structure, moment, resisting frame
  • A.R. Khoei*, H. Saffar, M. Eghbalian Pages 681-708
    In this paper, the thermo-dynamic analysis of contact–impact problem is presented in the large deformation of hyperelastic material based on the Taylor-Galerkin method. The technique is applied for the time domain discretization of thermo-dynamic governing equations in the advection-diffusion problems. The impenetrability condition and frictional contact constraints are fulfilled by imposing the augmented-Lagrange technique for non-matching contact surfaces. The Taylor-Galerkin method is employed to describe the advection-diffusion effect in the numerical solution of parabolic equation of unsteady heat transfer condition. The effect of temperature is taken into account in the stress field by satisfying the free energy function. The normal and tangential forces at the contact surface are related to the temperature and heat conductivity. Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed computational algorithm in large deformation thermo-dynamic analysis of contact–impact problems.
    Keywords: Contact–impact, thermo, dynamic model, augmented, Lagrange method, Taylor, Galerkin technique, large deformation
  • M.I. Khodakarami*, M. Fakharian Pages 709-732
    The scaled boundary based methods are commonly known as semi-analytical approaches, which have very good accuracy and efficiency for solving various kinds of problems. In this paper, a new trend for improvement of the decoupled scaled boundary-finite element method (DSBFEM) in order to solve the 2D elastostatic and elastodynamic problems is provided. In this technique, only the boundaries of the problem domain are discretized by specific sub-parametric elements. Mapping functions are employed as a class of higher-order Lagrange polynomials which are set at Gauss-Lobatto-Legendre control points,so, the special shape functions, Gauss-Lobatto-Legendre numerical integration, and the integral form of the weighted residual method lead to the diagonal coefficient matrices in the governing equations. The main differences between the study conducted and the prior researches regarding decoupled scaled boundary-finite element method is that here in, geometry production procedure of the interpolation function, integration of the different is selected, and using this approach, we could reduce the complexity of the DSBFEM. Validity and accuracy of the present method are demonstrated through two benchmark elastostatic problems and three benchmark elastodynamic problems that are successfully modeled using a few numbers of DOFs. The numerical results agree very well with the analytical solutions and the results from other numerical methods.
    Keywords: Decoupled SBFEM, 2D elastic problems, sub, parametric element, Lagrange polynomials, Gauss, Lobatto, Legendre integration