Ersin Aydin

Bio: Ersin Aydin is an academic researcher from Niğde University. The author has contributed to research in topics: Damper & Stiffness. The author has an hindex of 7, co-authored 21 publications receiving 295 citations. Previous affiliations of Ersin Aydin include Istanbul Technical University.

Optimal damper distribution for seismic rehabilitation of planar building structures

Abstract: In this study, the variations of optimal damper placement using different objective functions are presented. Instead of the usual choice of transfer function amplitude of the top displacement of the structure, the transfer function amplitude of the base shear force evaluated at the undamped fundamental natural frequency of the structure is chosen as an objective function. In the optimization procedure, the damping coefficients of the added dampers are treated as design variables. An active constraint on the sum of the damping coefficients of added dampers and the upper and lower bounds for each damper are taken into consideration. The new objective function based on transfer function amplitude of the base shear force is compared with the transfer function amplitudes of top displacement. The response of the structure is investigated for both of the objective functions in terms of the transfer function. The time history analysis is performed using the Kobe earthquake ground motion records to demonstrate the validity of the proposed design method. The results of the numerical procedure show that the proposed procedure based on the transfer function of the base shear force can also be beneficial in the rehabilitation of seismic response of the structures.

Using an artificial bee colony algorithm for the optimal placement of viscous dampers in planar building frames

Abstract: In this study, an Artificial Bee Colony Algorithm (ABCA) is used to obtain the optimal size and location of viscous dampers in planar buildings to reduce the damage to the frame systems during an earthquake. The transfer function amplitude of the top displacement and the elastic base shear force evaluated at the first natural circular frequency of structures are chosen as objective functions. The damper coefficients of the added viscous dampers are taken into consideration as design variables in a planar building frame. Transfer function amplitude of the top displacement and the amplitude of the elastic base shear force at the fundamental natural frequency are minimized under an active constraint on sum of the damper coefficients of the added dampers. According to two specified objective functions, an optimization algorithm based on the ABCA is proposed. The proposed method is verified by a gradient-based algorithm; steepest direction search algorithm (SDSA). The proposed ABCA and the SDSA are applied to find the optimal damper distribution for a nine-storey planar building then the optimal damper allocation obtained from the ABCA is investigated to rehabilitate models of irregular planar buildings. The validity of the proposed method was demonstrated through a time history analysis of the optimal damper designs, which were determined based on the frequency domain using the ABCA. The numerical results of the proposed optimal damper design method show that the use of the ABCA can be a practical and powerful tool to determine the optimal damper allocation in planar building structures.

Optimal damper placement based on base moment in steel building frames

Abstract: A new damper optimization method for finding optimal size and location of the added viscous dampers is proposed based on the elastic base moment in planar steel building frames A Fourier Transform is applied to the equation of the motion and the transfer function in terms of the fundamental natural frequency of the structures is defined The transfer function amplitude of the elastic base moment evaluated at the first natural circular frequency of the structure is chosen as a new objective function in the minimization problem The damper coefficients of the added viscous dampers are taken into consideration as design variables in a steel planar building frame The transfer function amplitude of the elastic base moment is minimized under an active constraint on the sum of the damper coefficients of the added dampers and the passive constraints on the upper and lower bounds of the added dampers The optimal damper design presented in this paper is compared with other optimal damper methods based on top displacement, top absolute acceleration and base shear A ten-storey steel planar building frame is chosen to be rehabilitated with the optimal dampers The optimal damper allocation is obtained for the transfer function amplitude of the elastic base moment then compared with the other damper optimization methods in terms of the transfer function response The results of the proposed method show that the method can also be beneficial to decrease both the base moment and the interstorey drift ratios in some frequency regions

Analysis of efficiency of passive dampers in multistorey buildings

Abstract: In this study, optimum design of viscous dampers under different mode behaviors are investigated for structures exposed to earthquakes The structure is modeled as a shear frame and considered as linear The upper and lower limit values of the dampers are defined as passive constraints, while the damping coefficients of the dampers placed in each storey are considered as the design variables The use of these technological tools in construction has caused a serious cost increase It is therefore important to use minimum of these elements For this reason, the sum of the damping coefficients of the dampers is regarded as the objective function and is minimized as an indication of the capacities of the dampers placed in the building stories and thus their costs It is well known that the addition of dampers to the structure increases the damping ratio of the structure A new active constraint is included in the optimization problem as the target damping ratio The equation required for the calculation of the value of the target damping ratio corresponding to any mode is also derived The simple optimization problem is solved using three different optimization algorithms: Simulated Annealing, Nelder Mead and Differential Evolution algorithms Optimum designs are found to minimize the cost function and provide all constraints In the shown numerical example, the effect of the variation of the building period and the changes of the target damping ratio on the optimization is investigated Furthermore, earthquake behavior of the structure corresponding to these optimum designs is investigated using El Centro Earthquake (NS) record and examined in terms of period and additional damping ratios of the maximum displacements to the floors In addition, the proposed method finds the optimum damper distribution considering the first two modes The proposed optimum damper design method is very simple and it is a method which reaches the optimum designs in different mode behaviors As a result, it has been shown in the numerical examples that the optimum damper design can be changed according to the variations of the designer’s constraints

Optimal Design and Distribution of Viscous Dampers for Shear Building Structures Under Seismic Excitations

Abstract: Viscous dampers (VDs) are effective and widely used passive devices for the protection of civil structures, provided that appropriate design is carried out For this purpose, an optimal design and optimum distribution of VDs method is presented for a shear building under the critical excitation by using random vibration theory in frequency domain In the optimization, by using Differential Evolution (DE) algorithm, the and top floor displacement are evaluated as objective functions taking into consideration upper and lower limits of VDs damping coefficients, so that optimal damper placement and properties of shear building can be determined In this design, VDs-shear building system is tested under three different ground motions being compared to some methods in the literature and uniformly distributed VDs placed at each story It is shown that, the results of study are both compatible and very successful in reducing the response of structure under the different ground motions

Design strategies of viscous dampers for seismic protection of building structures: A review

Abstract: Fluid viscous dampers (FVDs) are well-established supplemental energy dissipation devices that have been widely used for earthquake protection of structures. Optimal design, placement and sizing of FVDs have been extensively investigated in the last four decades. In this review paper, an overview of the most popular methodologies from the abundant literature in the field is presented. Key aspects and main characteristics of the different strategies to identify the optimal damping coefficients and the optimal placement of FVDs are scrutinized in a comparative manner. The optimal design problem is often solved through a numerical approach to a constrained optimization problem, by minimizing some performance criteria that are representative measures of the system response. With reference to two simple benchmark six-story shear-type structures subject to both a stochastic earthquake excitation and 44 natural ground motions extracted from the FEMA P695 record set, comparison of the seismic performance is carried out considering FVDs designed according to different methods — an overall number of 138 different design scenarios are incorporated in this comparative study. These methods are based either on a desired (target) damping ratio constraint or on a fixed total cost, here roughly related to the sum of the damping coefficients of the added FVDs. Some energy-based perspectives are also given in this review paper in order to interpret the seismic performance in terms of the amount of energy dissipated by the FVDs, out of the total input energy from the earthquake excitation.

Closure of "Seismic Soil-Structure Interaction in Buildings. II: Empirical Findings"

Abstract: System identification analyses are used to evaluate soil-structure interaction effects for 77 strong motion data sets at 57 building sites that encompass a wide range of structural and geotechnical conditions. Kinematic interaction effects on the \"input\" motion at the bases of structures are found to be relatively modest in many cases, whereas inertial interaction effects on the structural response to these motions can be significant. To quantify inertial interaction effects, fixed- and flexible-base modal vibration parameters are used to evaluate first-mode period lengthening

Developed comparative analysis of metaheuristic optimization algorithms for optimal active control of structures

Abstract: A developed comparative analysis of metaheuristic optimization algorithms has been used for optimal active control of structures. The linear quadratic regulator (LQR) has ignored the external excitation in solving the Riccati equation with no sufficient optimal results. To enhance the efficiency of LQR and overcome the non-optimality problem, six intelligent optimization methods including BAT, BEE, differential evolution, firefly, harmony search and imperialist competitive algorithm have been discretely added to wavelet-based LQR to seek the attained optimum feedback gains. The proposed approach has not required the solution of Riccati equation enabling the excitation effect in controlling process. Employing this advantage by each of six mentioned algorithms to three-story and eight-story structures under different earthquakes led to define (1) the best solution, (2) convergence rate and (3) computational effort of all methods. The purpose of this research is to study the aforementioned methods besides the superiority of ICA in finding the optimal responses for active control problem. Numerical simulations have confirmed that the proposed controller is enabling to significantly reduce the structural responses using less control energy compared to LQR.

A European Association for the Control of Structures joint perspective. Recent studies in civil structural control across Europe

Abstract: SUMMARY Structural control has been comprehensively studied over the world as a multidisciplinary research field. The present work is motivated by an attempt to give a common frame to the recent research and applications of structural control technology in civil engineering across Europe. They include novel passive dampers, functional materials and semi-active dampers, active control systems, and their performance investigations. Design methods for the vibrations reduction of buildings, bridges, and wind turbines are discussed with reference to case studies. Control algorithms and dimension reduction techniques are also studied. Adaptation strategies and techniques based on the potential offered by piezoelectricity are reviewed. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.

Effectiveness of distributed tuned mass dampers for multi-mode control of chimney under earthquakes

Abstract: Effectiveness of distributed tuned mass dampers (d-TMDs) designed according to the mode shapes for multi-mode control of chimneys as against the TMDs placed arbitrarily (ad-TMDs) and single TMD (STMD) under earthquake ground motions is investigated. The investigation includes geometrically regular and irregular chimneys under un-cracked and cracked conditions. A reinforced concrete (RC) chimney is considered as an assemblage of beam elements, each assumed to have constant diameter over the element length. The coupled differential equations of motion for the chimney and TMDs are derived and solved using Newmark’s integration method. Best possible locations of the TMDs are identified based on the mode shapes of the uncontrolled (NC) chimney. A TMD is placed where the mode shape amplitude of the chimney is the largest or larger in a particular mode and is tuned with the corresponding modal frequency. The number of modes to be controlled is decided according to total modal mass participation being ninety percent. In order to achieve the objective of the study, the performance of the d-TMDs used in the present method is compared with the STMD and ad-TMDs cases. A parametric study is conducted to find the most suitable mass ratio and damping ratio for all cases. It is observed that the d-TMDs are more effective than the STMD and ad-TMDs for the same total mass of the TMD/TMDs.