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Abstract
The applications of active control is being more popular nowadays. Several control algorithms have been developed to determine optimum control force. In this paper, a Chaotic Particle Swarm Optimization (CPSO) technique, based on Logistic map, is used to compute the optimum control force of active tendon system. A chaotic exploration is used to search the solution space for optimum control force. The response control of Multi-Degree of Freedom (MDOF) shear buildings, equipped with active tendons, is introduced as an optimization problem, based on Instantaneous Optimal Active Control algorithm. Three MDOFs are simulated in this paper. Two examples out of three, which have been previously controlled using Lattice type Probabilistic Neural Network (LPNN) and Block Pulse Functions (BPFs), are taken from prior works in order to compare the efficiency of the current method. In the present study, a maximum allowable value of control force is added to the original problem. Later, a twenty-story shear building, as the third and more realistic example, is considered and controlled. Besides, the required Central Processing Unit (CPU) time of CPSO control algorithm is investigated. Although the CPU time of LPNN and BPFs methods of prior works is not available, the results show that a full state measurement is necessary, especially when there are more than three control devices. The results show that CPSO algorithm has a good performance, especially in the presence of the cut-off limit of tendon force; therefore, can widely be used in the field of optimum active control of actual buildings.

Key Words
Chaotic Particle Swarm optimization; logistic map; instantaneous optimal active control; active tendon system; shear buildings; LPNN; BPFs

Address
Saeed Asil Gharebaghi and Ehsan Zangooei : Civil Engineering Faculty, K. N. Toosi University of Technology, Tehran, Iran

Abstract
This study presents a particle swarm optimization algorithm integrated with weighted particle concept and improved fly-back technique. The rationale behind this integration is to utilize the affirmative properties of these new terms to improve the search capability of the standard particle swarm optimizer. Improved fly-back technique introduced in this study can be a proper alternative for widely used penalty functions to handle existing constraints. This technique emphasizes the role of the weighted particle on escaping from trapping into local optimum(s) by utilizing a recursive procedure. On the other hand, it guaranties the feasibility of the final solution by rejecting infeasible solutions throughout the optimization process. Additionally, in contrast with penalty method, the improved fly-back technique does not contain any adjustable terms, thus it does not inflict any extra ad hoc parameters to the main optimizer algorithm. The improved fly-back approach, as independent unit, can easily be integrated with other optimizers to handle the constraints. Consequently, to evaluate the performance of the proposed method on solving the truss weight minimization problems with discrete variables, several benchmark examples taken from the technical literature are examined using the presented method. The results obtained are comparatively reported through proper graphs and tables. Based on the results acquired in this study, it can be stated that the proposed method (integrated particle swarm optimizer, iPSO) is competitive with other metaheuristic algorithms in solving this class of truss optimization problems.

Key Words
optimization; truss structures; particle swarm optimization, weighted particle, constraint handling

Address
Ali Mortazavi and Ayhan Nuhoglu : Department of Civil Engineering, Ege University, 35100 İzmir, Turkey Vedat Togan : Department of Civil Engineering, Karadeniz Technical University, 61080 Trabzon, Turkey

Abstract
An overhead travelling crane structure of two doubly symmetric welded box beams is designed for minimum cost. The rails are placed over the inner webs of box beams. The following design constraints are considered: local buckling of web and flange plates, fatigue of the butt K weld under rail and fatigue of fillet welds joining the transverse diaphragms to the box beams, fatigue of CFRP (carbon fibre reinforced plastic) laminate, deflection constraint. For the formulation of constraints the relatively new standard for cranes EN 13001-3-1 (2010) is used. To fulfill the deflection constraint CFRP strengthening should be used. The application of CFRP materials in strengthening of steel and concrete structures are widely used in civil engineering applications due to their unique advantages. In our study, we wanted to show how the mechanical properties of traditional materials can be improved by the application of composite materials and how advanced materials and new production technologies can be applied. In the optimization the following cost parts are considered: material, assembly and welding of the steel structure, material and fabrication cost of CFRP strengthening. The optimization is performed by systematic search using a MathCAD program.

Key Words
FRP strengthening; crane; welded box beam; fatigue; cost calculation; optimization

Address
Gyorgy Kovacs and Jozsef Farkas : Institute of Logistics, University of Miskolc, Miskolc-Egyetemvaros, Hungary

Abstract
An effective design approach for Multiple Tuned Mass Dampers (MTMDs) in pedestrian bridges was proposed by utilizing the transfer function to obtain each TMD\'s optimum stiffness and damping. A systematic simulation of pedestrian excitations was described. The motion equation of a typical MTMD system attached to a Multi-degree-of-freedom (MDOF) system was presented, and the transfer function from the input pedestrian excitations to the output acceleration responses was defined. By solving the minimum norm of the transfer function, the parameters of the MTMD which resulted in the minimum overall responses can be obtained. Two applications of lightly damped pedestrian bridges attached with MTMD showed that MTMDs designed through this method can significantly reduce the structural responses when subjected to pedestrian excitations, and the vibration control effects were better than the MTMD when it was considered as being composed of equal number and mass ratios of TMDs designed by classical Den Hartog method.

Key Words
multiple tuned mass dampers; pedestrian bridge; optimization design; vibration control; pedestrian excitation

Address
Zheng Lu, Peizhen Li: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China; Research Institute of Structural Engineering and Disaster Reduction, Tongji University, Shanghai 200092, China Xiaoyi Chen: Research Institute of Structural Engineering and Disaster Reduction, Tongji University, Shanghai 200092, China Xiaowei Li: Research Institute of Structural Engineering and Disaster Reduction, Tongji University, Shanghai 200092, China; Tongji Architectural Design (Group) Co., Ltd (TJAD), Shanghai 200092, China

Abstract
This paper deals with critical buckling load optimization of symmetric angle-ply laminated stepped flat columns under axial compression load. The design objective is the maximization of the critical buckling load and the design variable is the fiber orientations in the layers of the laminates. The classical laminate plate theory is used for the finite element solution of the laminated stepped flat columns. The modified feasible direction (MFD) method is used for the optimization routine. For this purpose, a program based on FORTRAN is exploited. Finally, the optimization results are presented for width ratios (b/B), ratios of fillet radius (r1/r2), aspect ratios (L/B) and boundary conditions. The results are presented in graphical and tabular forms and the results are compared.

Key Words
laminated stepped columns; critical buckling load; modified feasible direction method; optimization

Address
Umut Topal: Department of Civil Engineering, Karadeniz Technical University, Faculty of Technology, 61830, Trabzon, Turkey

Abstract
In this study, recently developed swarm intelligence algorithm called Social Spider Optimization (SSO) approach and its enhanced version of SSO algorithm with spider jump techniques is used to develop a structural optimization technique for steel space structures. The improved version of SSO uses adaptive randomness probability in generating new solutions. The objective function of the design optimization problem is taken as the weight of a steel space structure. Constraints\' functions are implemented from American Institute of Steel Construction-Load Resistance factor design (AISC-LRFD) and Ad Hoc Committee report and practice which cover strength, serviceability and geometric requirements. Three steel space structures are optimized using both standard SSO and SSO with spider jump (SSO_SJ) algorithms and the results are compared with those available in the literature in order to investigate the performance of the proposed algorithms.

Key Words
optimization; swarm intelligence; metaheuristic; social spider optimization; space frame; space truss

Address
Ibrahim Aydogdu: Department of Civil Engineering, Akdeniz University, Dumlupinar Bvld., 07058, Antalya, Turkey Perihan Efe, Metin Yetkin: Department of Civil Engineering, Balikesir University, Balikesir, Turkey Alper Akin: Trinity Meyer Utility Structures, Memphis, TN, USA

Abstract
Photovoltaic (PV) panels are used in high-rise buildings to convert solar energy to electricity. Due to the considerable energy consumption of high-rise buildings, applying PV technology is of great significance to energy saving. In the application of PV panels, one of the most important construction issues is the connection of the PV panel with the main structures. One major difficulty of the connection design is that the PV panel connection consists of two separate components with coupling and indeterminate dimension. In this paper, the gap element is employed in these two separated but coupled components, i.e., hook and catch. Topology optimization is applied to optimize and design the cross-section of the PV panel connection. Pareto optimization is conducted to operate the optimization subject to multiple load scenarios. The initial design for the topology optimization is determined by the common design specified by the Technical Code for Glass Curtain Wall Engineering (JGJ 102-2003). Gravity and wind load scenarios are considered for the optimization and numerical analysis. Post analysis is conducted for the optimal design obtained by the topology optimization due to the manufactory requirements. Generally, compared with the conventional design, the optimized connector reduces material use with improved structural characteristics.

Key Words
photovoltaic panel connector; topology optimization; SIMP; high-rise building; numerical analysis

Address
Xilin Lu, Jiaqi Xu, Hongmei Zhang: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, 1239 Siping Rd, Yangpu, Shanghai, China Peng Wei: State Key Laboratory of Subtropical Building Science, School of Civil Engineering and Transportation, South China University of Technology, 381 Wushan Rd, Tianhe, Guangzhou, Guangdong, China

Abstract
Structural sizing is a rewarding task due to its non-convex constrained nature in the design space. In order to provide both global exploration and proper search refinement, a hybrid method is developed here based on outstanding features of Evolutionary Computing and Teaching-Learning-Based Optimization. The new method introduces an observer phase for memory exploitation in addition to vector-sum movements in the original teacher and learner phases. Proper integer coding is suited and applied for structural size optimization together with a fly-to-boundary technique and an elitism strategy. Performance of the proposed method is further evaluated treating a number of truss examples compared with teaching-learning-based optimization. The results show enhanced capability of the method in efficient and stable convergence toward the optimum and effective capturing of high quality solutions in discrete structural sizing problems.

Key Words
discrete optimization; constrained structural sizing, hybrid evolutionary computing

Address
Department of Engineering, Kharazmi University, 43 Shahid-Mofatteh, Tehran, Iran

Abstract
This paper develops a two-stage method for structural damage identification by using modal data. First, the Residual Force Vector (RFV) is introduced to detect any potentially damaged elements of structures. Second, data of the frequency domain are used to build up the objective function, and then the Imperialist Competitive Algorithm (ICA) is utilized to estimate damaged extents. ICA is a heuristic algorithm with simple structure, which is easy to be implemented and it is effective to deal with high-dimension nonlinear optimization problem. The advantages of this present method are: (1) Calculation complexity can be decreased greatly after eliminating many intact elements in the first step. (2) Robustness, ICA ensures the robustness of the proposed method. Various damaged cases and different structures are investigated in numerical simulations. From these results, anyone can point out that the present algorithm is effective and robust for structural damage identification and is also better than many other heuristic algorithms.

Key Words
structural damage identification; residual force vector; optimization problem; ICA; heuristic algorithm

Address
Z.H. Ding, R.Z. Yao, J.L. Huang, M. Huang and Z.R. Lu: School of Engineering, Sun Yat-sen University, Guangzhou, Guangdong Province, 510006, P.R. China Z.H. Ding: Center for Infrastructural Monitoring and Protection, Curtin University, Bentley, WA6102, Australia

Abstract
In this study, the optimum parameters of Tuned Mass Dampers (TMDs) are proposed using Gravity Search Algorithm (GSA) and Particle Swarm Optimization (PSO) to reduce the responses of the structures. A MATLAB program is developed to apply the new approach to the benchmark 10 and 40-story structures. The obtained results are compared to those of other optimization methods used in the literature to verify the developed code. To show the efficiency and accuracy of the proposed methods, nine far-field and near-field worldwide earthquakes are applied to the structures. The results reveal that in the 40-story structure, GSA algorithm can reduce the Relative Displacement (RD) and Absolute Acceleration (AA) up to 43% and 21%, respectively while the PSO decreases them by 50% and 25%, respectively. In contrast, both GSA and PSO algorithms reduce the RD and AA about 29% and 21% for the 10-story structure. Furthermore, using the proposed approach the required TMD parameters reduce by 47% and 63% in the 40 and 10-story buildings in comparison with the referenced ones. Result evaluation and related comparison indicate that these methods are more effective even by using smaller TMD parameters resulting in the reduction of acting force from TMD, having smaller stiffness and damping factors while being more cost effective due to its decreased parameters. In other words, the TMD with optimum parameters can play a positive role in both tall and typical structures.

Key Words
GSA algorithm; PSO algorithm; TMD; optimization; vibration reduction

Address
Nadia M. Mirzai : School of Civil Engineering, College of Engineering, the University of Tehran, Tehran, Iran Seyed Mehdi Zahrai : Center of Excellence for Engineering and Management of Civil Infrastructures, School of Civil Engineering, College of Engineering, the University of Tehran, Tehran, Iran Fatemeh Bozorgi : School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran

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