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A Novel Design Method of Single TMD Exposed to Seismic Effects
(CRC Press, 2023) Cetin, Huseyin; Aydin, Ersin; Ozturk, Baki
A tuned mass damper (TMD) can be an effective passive device for decreasing hazardous vibrations, when it is properly designed. In this chapter, the differential evolution (DE) algorithm is used to suggest an optimal TMD design technique based on transfer functions. Random vibration theory and the probabilistic critical excitation method are used to generate the governing equations in the frequency domain. The process involves optimizing all of a TMD's properties, including mass, stiffness, and damping coefficients. The mean-square of top floor absolute acceleration and top floor displacement have been chosen as objective functions to be minimized with respect to the upper and lower limits of TMD parameters. Shear building models with single and multiple TMD are tested using different earthquake acceleration records in order to understand the performance of the suggested technique. In addition, the findings are compared to those of other studies in the literature. © 2024 selection and editorial matter, Ehsan Noroozinejad Farsangi, Mohammad Noori, Tony T.Y. Yang, Paulo B. Lourenço, Paolo Gardoni, Izuru Takewaki, Eleni Chatzi, and Shaofan Li; individual chapters, the contributors.
An Experimental Study on the Effects of Different Pendulum Damper Designs on Structural Behavior
(Springer International Publishing Ag, 2023) Aydin, Ersin; Ozturk, Baki; Kebeli, Yunus Emre; Gultepe, Gorkem
Pendulum dampers, which are the subject of this study, are a type of tuned mass damper (TMD). In general, TMDs are effective since they are designed according to the first mode behavior of the buildings. In this study, the effects of pendulum dampers on the structural behavior are investigated by performing vibration experiments on a 3-storey shear frame model with reduced dimensions. Harmonic loads are applied to the test models with and without pendulums on a one-way shaking table. Firstly, experiments without dampers were performed on the selected 3-storey reduced building model, and structural responses were found. The mass of pendulum dampers is chosen to be around 3% of the total mass of the structural model. One of the main aims of this study is to reveal the effects of the different placements of the dampers on the dynamic behavior. Accordingly, a single pendulum is independently placed on the top floor, the second floor, and finally on the first floor. In addition, experiments are carried out by establishing double damper models and then a triple damper model. By creating seven different damper models, the experiments are repeated under harmonic loads with different frequencies. Tests under a harmonic load equal to the first mode frequency of the undamped model reveal the behavior of the models in the resonant state. Experiments show that the pendulums used are highly effective in the resonance state. Some models with more than one damper have also been shown to be effective at reducing dynamic response.
Application of numerical analysis for investigation of relationship between slump values and other rheological properties of fresh concrete
(ACADEMIC JOURNALS, 2010) Bilgil, Ahmet; Ozturk, Baki; Samandar, Ayhan
The main concern in working with fresh concrete is the workability during filling of formwork. In this study, the mechanism of segregation during the filling of fresh concrete into formwork is numerically investigated considering the rheological properties of fresh concrete. A mathematical model, which considers fresh concrete as a non-Newtonian fluid that, is used for the investigation of relationship between slump values and rheological properties of fresh concrete. The aggregates are considered as Lagrangian particles whose trajectories determine segregation. This study will provide an insight to the relationships between workability and various rheological parameters of fresh concrete that is, yield stress, segregation, viscosity during filling of fresh concrete into formwork. The relationships between workability and rheological properties during the fill of fresh concrete for both concrete mixtures with no admixtures (MC) and concrete mixtures with admixtures (MCS) are investigated. MCS concrete mixture includes super-plasticizers for the same composition of MC. Cylindrical formworks for three different heights of 50, 100 and 150 cm are employed. It is observed that MCS mixtures have higher slump values and less aggregate segregation (%) compared to MC mixtures for the same compositions of fresh concrete. It is found that, slump values decrease as yield stress increases for both MC and MCS fresh concrete mixtures. When MCS mixtures are used, there is a significant reduction in yield stress compared to MC mixtures.
DESIGN OF VISCO-ELASTIC SUPPORTS FOR TIMOSHENKO CANTILEVER BEAMS
(Konya Teknik Univ, 2023) Aydin, Ersin; Kebeli, Yunus Emre; Cetin, Huseyin; Ozturk, Baki
The appropriate design of supports, upon which beams are usually placed as structural components in many engineering scenarios, has substantial significance in terms of both structural efficacy and cost factors. When beams experience various dynamic vibration effects, it is crucial to contemplate appropriate support systems that will effectively adapt to these vibrations. The present work investigates the most suitable support configuration for a cantilever beam, including viscoelastic supports across different vibration modes. Within this particular framework, a cantilever beam is simulated using beam finite elements. The beam is positioned on viscoelastic supports, which are represented by simple springs and damping elements. These supports are then included in the overall structural model. The equation of motion for the beam is first formulated in the temporal domain and then converted to the frequency domain via the use of the Fourier Transform. The basic equations used in the frequency domain are utilized to establish the dynamic characteristics of the beam by means of transfer functions. The determination of the ideal stiffness and damping coefficients of the viscoelastic components is achieved by minimizing the absolute acceleration at the free end of the beam. In order to minimize the objective function associated with acceleration, the nonlinear equations derived from Lagrange multipliers are solved using a gradient-based technique. The governing equations of the approach need partial derivatives with respect to design variables. Consequently, analytical derivative equations are formulated for both the stiffness and damping parameters. The present work introduces a concurrent optimization approach for both stiffness and damping. Passive constraints are established inside the optimization problem to impose restrictions on the lower and higher boundaries of the stiffness and damping coefficients. On the other hand, active constraints are used to ascertain the specific values of the overall stiffness and damping coefficients. The efficacy of the established approach in estimating the ideal spring and damping coefficients of viscoelastic supports and its ability to provide optimal support solutions for various vibration modes have been shown via comparative experiments with prior research.
Differential quadrature method for frequency analysis of membranes having irregular domains using an eight-node curvilinear element
(TECHNO-PRESS, 2009) Ersoy, Hakan; Ozpolat, Lutfiye; Civalek, Omer; Ozturk, Baki
[Abstract Not Available]
Discrete singular convolution algorithm for non-linear transient response of circular plates resting on Winkler-Pasternak elastic foundations with different types of dynamic loading
(NATL INST SCIENCE COMMUNICATION, 2009) Civalek, Omer; Ozturk, Baki
Nonlinear dynamic analysis of circular plates on two parameter elastic foundations is studied. Winkler and Pasternak models of elastic foundation are used. The nonlinear partial differential equations obtained from von Karman's large deflection plate theory have been solved by using the discrete singular convolution (DSC) in the space domain and the harmonic differential quadrature (HDQ) method in the time domain. The influence of stiffness of Winkler (K) and Pasternak (G) foundation on geometrically nonlinear dynamic response of plates is investigated. The influence of damping on the nonlinear dynamic response has also been studied. Numerical results obtained by the application of present technique compare well with the results available in literature.
Editorial: New Trends and Developments on Structural Control & Health Monitoring
(Frontiers Media Sa, 2020) Aydin, Ersin; Ozturk, Baki; Farsangi, Ehsan Noroozinejad; Bogdanovic, Aleksandra
[Abstract Not Available]
Experiments of tuned liquid damper (TLD) on the reduced shear frame model under harmonic loads
(E D P SCIENCES, 2017) Aydin, Ersin; Ozturk, Baki; Dutkiewicz, Maciej; Cetin, Hseyin; Okkay, Ozan; Ohancan, Ugur; Sirin, Yunus Emre; Dancova, P
In this study shaking table tests which are applied on 3-Storey reduced shear frame models with TLD's subjected to harmonic loadings are presented. Firstly, free vibration experiments are conducted on the structure and 1st free vibration frequency of the structure is determined. The structure is shaken under harmonic loading at a frequency equal to 1st frequency of the structure which provides the resonance condition. Displacements and accelerations are measured at storey levels of the structure. A container in a rectangular prism shape is manufactured as a TLD model. Liquid is poured in the container and the same experiments are repeated at different liquid heights. The effect of TLD application on the structural models considering displacement and acceleration of the structure are investigated. In addition the effect of TLD application and its allocation at different storey levels are calculated experimentally. As a result of the conducted experiments, most convenient TLD models considering both displacement and acceleration behavior are determined. It is observed that all the damping models cause significant levels of reduction in seismic behavior of the structure under harmonic loading.
Free Vibration Analysis of Beam on Elastic Foundation by the Variational Iteration Method
(FREUND PUBLISHING HOUSE LTD, 2009) Ozturk, Baki
This paper applies the variational iteration method (VIM) to analysis of free vibration of a beam on an elastic foundation. Three different axially loaded cases are considered: 1) one end fixed, the other end simply supported; 2) both ends fixed; and 3) both ends simply supported. Analytical solutions and the frequency factors are obtained for different ratios of axial load acting on the beam to Euler buckling load. The VIM results are in excellent agreement with both analytical solutions for all the cases considered in this paper and the differential transform method (DTM) results available in the literature for the fixed-pinned case.
Free vibration analysis of beam on elastic foundation by the variational iteration method
(Freund Publishing House Ltd, 2009) Ozturk, Baki
This paper applies the variational iteration method (VIM) to analysis of free vibration of a beam on an elastic foundation. Three different axially loaded cases are considered: 1) one end fixed, the other end simply supported; 2) both ends fixed; and 3) both ends simply supported. Analytical solutions and the frequency factors are obtained for different ratios of axial load acting on the beam to Euler buckling load. The VIM results are in excellent agreement with both analytical solutions for all the cases considered in this paper and the differential transform method (DTM) results available in the literature for the fixedpinned case. © Freund Publishing House Ltd.
Free vibration analysis of tapered beam-column with pinned ends embedded in Winkler-Pasternak elastic foundation
(TECHNO-PRESS, 2010) Civalek, Omer; Ozturk, Baki
The current study presents a mathematical model and numerical method for free vibration of tapered piles embedded in two-parameter elastic foundations. The method of Discrete Singular Convolution (DSC) is used for numerical simulation. Bernoulli-Euler beam theory is considered. Various numerical applications demonstrate the validity and applicability of the proposed method for free vibration analysis. The results prove that the proposed method is quite easy to implement, accurate and highly efficient for free vibration analysis of tapered beam-columns embedded in Winkler- Pasternak elastic foundations.
Homotopy perturbation method for free vibration analysis of beams on elastic foundation
(IOP PUBLISHING LTD, 2010) Ozturk, Baki; Coskun, Safa Bozkurt; Koc, Mehmet Zahid; Atay, Mehmet Tarik; Khalili, N; Valliappan, S; Li, Q; Russell, A
In this study, the homotopy perturbation method (HPM) is applied for free vibration analysis of beam on elastic foundation. This numerical method is applied on a previously available case study. Analytical solutions and frequency factors are evaluated for different ratios of axial load N acting on the beam to Euler buckling load, N-r. The application of HPM for the particular problem in this study gives results which are in excellent agreement with both analytical solutions and the variational iteration method (VIM) solutions for the case considered in this study and the differential transform method (DTM) results available in the literature.
Influence of soil-structure interaction (SSI) on optimal design of passive damping devices
(Elsevier Science Inc, 2020) Aydin, Ersin; Ozturk, Baki; Bogdanovic, Aleksandra; Farsangi, Ehsan Noroozinejad
Recently, the interest in research for optimization of viscous dampers in design of buildings has been increasing. In this study, the effect of soil-structure interaction has been taken into account for the purpose of optimal design of viscous dampers. A damper optimization method based on a target damping ratio and interstorey drift ratio found in literature has been adapted for a building structure model considering different types of sandy soils. While passive constraints have been taken as upper and lower limits of each damper, active constraints have been considered as a target damping ratio in terms of damping coefficients. The proposed algorithm includes time history analyses that test the designer's optimal design. Interstorey drift ratios under design earthquakes have been checked at each design step. The first and second mode responses have been considered separately. According to the results obtained from this study, the negative impact of sandy soils on the dynamic behavior of superstructures can be overcome by optimal placement of dampers in buildings. The results of the analyses have shown that soil effects should be taken into account in solving damper optimization problems.
On the Efficacy of a Novel Optimized Tuned Mass Damper for Minimizing Dynamic Responses of Cantilever Beams
(Mdpi, 2022) Ozturk, Baki; Cetin, Huseyin; Dutkiewicz, Maciej; Aydin, Ersin; Farsangi, Ehsan Noroozinejad
This study examines the optimal design of a tuned mass damper (TMD) in the frequency domain so that the dynamic response of cantilever beams can be decreased. Random vibration theory is applied to identify the mean square acceleration of the endpoint of a cantilever beam as the objective function to be reduced. In addition, to determine the optimal TMD coefficient of mass, stiffness, and damping, a differential evolution (DE) optimization algorithm is employed. The upper and lower limit values of these parameters are taken into account. A majority of the previous studies have concentrated on determining just the stiffness and damping parameters of TMD. Nonetheless, in this study there is also the optimization of TMD mass parameters to determine the mass quantity. In addition, there has been inefficient use of the stochastic DE optimization algorithm method for the optimization of TMD parameters in previous studies. Hence, to obtain optimal TMD parameters, this algorithm is precisely used on the objective function. Tests are carried out on the cantilever beam with the TMD system following this optimization method with harmonic base excitations that resonate the foremost modes of the beam and white noise excitation. The method proposed here is reasonably practical and successful regarding the optimal TMD design. When a TMD is designed appropriately, the response of the cantilever beam under dynamic interactions undergoes a considerable reduction.
Optimal damper distributions in shear frames considering soil conditions
(European Association for Structural Dynamics, 2020) Aydin, Ersin; Ozturk, Baki; Sivrikaya, Osman
When there is an optimal damper application issue, superstructure models are installed and strongly connected to the ground. However; there is no consideration of the ground influences. Within this current research, the influence of sandy soil relative density upon damper issues has been analysed. Assessment has been carried out upon the optimal distribution of viscous dampers along with the influence of sandy soil relative density on the structural dynamic response for the n-storey shear building model. The soil-structure model governing equation has also been derived and the Fourier Transformation is used to present the frequency domain equations. An optimized procedure, which is the Steepest Direction Search Algorithm (SDSA), is applied. Minimization of the objective function, which is the base moment behaviour of structure stated within the frequency domain, is done. The fundamental mode response of structural model has been considered and the El Centro (NS) earthquake ground acceleration record is used to conduct the time history analyses. Investigation has been carried out for the sandy soil relative density influence upon the optimal design of structure responses along with the total damper capacity variation influence applied within the optimization level. Since the optimal design alters due to the base moment, the sandy soil influences have been assessed thoroughly. As compared to no damper at all case, the damped system has taken place with low base moment. At a rigid level, the structural response is lower as compared to a different sandy soil relative density. The structural response is enhanced after dampers are added based on proposed objective function. Furthermore, the damaging influence created by the poor ground conditions has also been reduced. © 2020 European Association for Structural Dynamics. All rights reserved.
Optimal Design and Distribution of Viscous Dampers for Shear Building Structures Under Seismic Excitations
(Frontiers Media Sa, 2019) Cetin, Huseyin; Aydin, Ersin; Ozturk, Baki
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, optimal design and optimum distribution of VDs method are presented for a shear building under the critical excitation by using random vibration theory in the frequency domain. In the optimization, by using Differential Evolution (DE) algorithm and the 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 the shear building can be determined. In this design, the VDs-shear building system is tested under the 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 the study are both compatible and very successful in reducing the response of the structure under the different ground motions.
Optimal viscous damper placement to prevent pounding of adjacent buildings
(European Association for Structural Dynamics, 2020) Cetin, Huseyin; Ozturk, Baki; Aydin, Ersin
Structural pounding is prevalent in general during earthquake shaking for adjacent structures in earthquake prone cities. In this study, the prevention of pounding effect is targeted by the optimal placement of viscous damping elements within the adjacent buildings. One of the important reasons of the pounding phenomenon is the out of phase vibrations of adjacent structures. A couple of adjacent structures which have different heights are modeled as shear buildings to set the proposed method. The relative displacement, defined as the extraction of horizontal displacements of adjacent structures at the top level of the shorter building, are chosen as the objective function to be minimized. In addition, reduction of relative displacement of the buildings and the effects of various vibration characteristics of each building is investigated based on transfer functions. Equations of motion of a structure, which are uncoupled when each structure is considered alone, become coupled when damping elements are placed in between the adjacent structures. The first mode response of the structures is considered while the transfer function response is derived. Optimal designs are determined for different total damping levels and different vibration characteristics of adjacent structures. The results of numerical analyses reveal that optimal designs effectively decrease the relative displacements between adjacent structures. Optimal designs are compared with the uniform design and without damper cases. The numerical analyses show that the proposed optimal damper design method in this study is vigorously effective for the prevention of pounding of adjacent buildings. © 2020 European Association for Structural Dynamics. All rights reserved.
Optimization of elastic spring supports for cantilever beams
(Springer, 2020) Aydin, Ersin; Dutkiewicz, Maciej; Ozturk, Baki; Sonmez, Mustafa
In this study,a new approach of optimization algorithm is developed. The optimum distribution of elastic springs on which a cantilever Timoshenko beam is seated and minimization of the shear force on the support of the beam is investigated.The Fourier transform is applied to the beam vibration equation in the time domain and transfer function, independent from the external influence, is used to define the structural response. For all translational modes of the beam, the optimum locations and amounts of the springs are investigated so that the transfer function amplitude of the support shear force is minimized. The stiffness coefficients of the springs placed on the nodes of the beam divided into finite elements are considered as design variables. There is an active constraint on the sum of the spring coefficients taken as design variables and passive constraints on each of them as the upper and lower bounds. Optimality criteria are derived using the Lagrange Multipliers method. The gradient information required for solving the optimization problem is analytically derived. Verification of the new approach optimization algorithm was carried out by comparing the results presented in this paper with those ones from analysis of the model of the beam without springs, with springs with uniform stiffness and with optimal distribution of springs which support a cantilever beam to minimize the tip deflection of the beam found in the literature. The numerical results show that the presented method is effective in finding the optimum spring stiffness coefficients and location of springs for all translational modes.The proposed method can give designers an idea of how to support the cantilever beams under different harmonic vibrations.
Optimum vertical location and design of multiple tuned mass dampers under seismic excitations
(Elsevier Science Inc, 2022) Ozturk, Baki; Cetin, Huseyin; Aydin, Ersin
An efficient optimum vertical location and design method of multiple tuned mass dampers (MTMDs) is proposed in order to reduce the response of building structures under seismic excitation. Governing equations are derived in frequency domain in terms of random vibration theory and probabilistic critical excitation method. In order to determine the location and optimum parameters of each tuned mass damper (TMD) which are mass, stiffness and damping coefficient, both top storey mean square absolute acceleration and displacement of shear building are chosen as the objective functions to be minimized via Differential Evolution (DE) optimization method. It is assumed that there is one TMD on each storey at the initial stage of the method. During the optimization, if the mass or stiffness parameters convergence to zero on a specific storey, then TMD is eliminated, so that optimum placement can be achieved. The sum of the critical effects corresponding to the selected bandwidths in the first, second and third frequency peak regions of the structure is taken into account, thus the high mode behaviors are also controlled. In order to understand the performance of proposed method, shear building model with multiple TMD is tested using different earthquake acceleration records and the findings are compared with some other studies available in the literature. The results show that the optimal MTMD design obtained from proposed method is very effective in reducing the dynamic response of building structure.
Optimum Viscous Damper Distribution for Seismic Rehabilitation of Building Structures with Soft Story Irregularity
(Springer Science and Business Media Deutschland GmbH, 2024) Koroglu, Arcan; Ozturk, Baki; Cetin, Huseyin; Aydin, Ersin
Viscous dampers (VDs) are remarkably effective passive energy dissipation devices successfully implemented in building structures to reduce seismic demands during earthquake excitations. Viscous dampers can be utilized to enhance the resilience of structures against earthquake excitations. Besides that, they can be used for seismic rehabilitation of existing structures. Viscous dampers influence the dynamic response of the building structures that they are attached to; therefore, their allocation is vital. Furthermore, the optimum design of viscous dampers is another critical concept since they are expensive devices; thus, their optimum distribution results in a more economical method. This study suggests a methodology to rehabilitate existing building structures with soft story irregularities via optimum viscous damper distribution using the Particle Swarm Optimization (PSO) algorithm. Soft story irregularity causes significantly large peak inter-story drift ratios (IDR) and abrupt changes in peak inter-story drift ratios between adjacent stories. The primary objective of this study is to limit the peak inter-story drift ratios to an allowable limit. In the scope of this study, the suggested procedure was tested on shear buildings with soft story irregularity under different earthquake ground motions. The results of this study show that it is possible to keep peak inter-story drift ratios at an allowable limit with an optimum viscous damper distribution for shear buildings with soft story irregularity. Moreover, this study shows that the Particle Swarm Optimization algorithm can be successfully implemented on optimum viscous damper design problems in building structures. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.

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