Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleYalnız künye2022A comparative study to determine seismic response of the box culvert wing wall under influence of soil-structure interaction considering different ground motions
Ozturk, Kasif Furkan; Cakir, Tufan; Araz, Onur
The present study deals with evaluation of the effects of different ground motions, backfill-structure interaction (BSI) and soil-structure interaction (SSI) on dynamic response of a box culvert wing wall. In obtaining numerical results, five different earthquake records with different frequency contents, five different backfill types and four different subsoil types are taken into account. Firstly, a finite element model (FEM) and three analytical models are proposed for analysis of the wing wall-backfill system under fixed-base case, and these fixed-base models are compared with each other through both modal analysis and displacement time-history analysis under the assumption of linear-elasticity. After validating the ability of the FEM approach, by extending the fixed-base FEM to take account of elastoplastic behavior of soil and SSI, a three dimensional (3-D) model has been described, and 3-D nonlinear analyses have been carried out in time domain. The numerical results show that the seismic response of the wing walls are affected remarkably by the SSI, BSI and frequency content of the earthquake.
- MakaleAçık Erişim2022Optimization of three-element tuned mass damper based on minimization of the acceleration transfer function for seismically excited structures
Araz, Onur
The three-element tuned mass damper (T-TMD) is an effective passive control device for single-degree of freedom structures due to harmonic external force. Unlike previous studies, this study aims at proposing a methodology for optimization of T-TMD positioned at the top floor of multi-degree of freedom structures under seismic loads. The equations of motion for a multi-story building controlled by a T-TMD are derived, and the T-TMD is then optimized using an advanced firefly algorithm (AFA) in the frequency domain. The aim of the optimization is to minimize the amplitude of the acceleration transfer function of the top floor of the building. The proposed methodology is implemented in two different shear buildings, and the optimum parameters are then verified by using benchmark earthquakes with different frequency components. The comparisons with the available works illustrate the availability of the AFA. The effect of the mass ratio on the optimum parameters of the T-TMD is also discussed in detail. Numerical results show that the use of the optimum T-TMD is an effective strategy to minimize the maximum structural responses of the multi-story buildings under seismic excitations. In particular, the optimum T-TMD is very effective when the maximum story responses (i.e., displacement and acceleration) occur at the top floor of the building.
- MakaleYalnız künye2022Optimization of multiple tuned mass dampers for a two-span continuous railway bridge via differential evolution algorithm
Araz, Onur; Kahya, Volkan
The study aims at proposing a methodology for optimization of multiple tuned mass dampers (MTMD) in reducing the multi-resonance vibrations of continuous bridges due to moving train loads. The equations of motion for time-domain analysis are derived for obtaining train-induced vibrations of a two-span continuous railway bridge with equipped MTMD-1 and MTMD-2 devices when the vehicle-bridge interaction (VBI) is considered. The bridge and the train are modeled as a Bernoulli-Euler beam with constant section and a series of moving sprung masses of identical length, respectively. To reduce the multiple resonance vibrations of a two-span continuous railway bridge, the MTMD-1 and MTMD-2 are tuned to the first mode and the second mode of the bridge, and they are attached to the midspan of each span, respectively. The optimum parameters of the both MTMD systems are investigated using the differential evolution (DE) method. The criterion chosen to obtain the optimum parameters is the minimization of the first two resonance peaks of the bridge. The influence of the different mass ratios and the number of TMD units in the MTMD system on the optimum parameters of the both MTMD systems and corresponding displacement responses of the bridge are also investigated. The results show that the VBI effect does not have much effect on the resonant train speeds and the control performance of TMDs. Therefore, the optimum parameters of TMDs can be obtained quickly by modeling the train as a series of moving forces for the vibration control of railway bridges.
- MakaleYalnız künye2022Effect of different objective functions on control performance of tuned mass damper for a high-rise building considering soil–structure interaction
Araz, Onur; Ozturk, Kasif Furkan; Cakir, Tufan
This paper deals with the optimization of the tuned mass damper (TMD) with different objective functions for high-rise building under earthquake motions considering soil–structure interaction (SSI). A study is conducted to search for the TMD that outperforms five objective functions (i.e., OF-1–OF-5) containing combinations of the structural responses and foundation responses. The main goal of the present study is to evaluate and compare the control performance of these five objective functions. The optimum parameters of TMD are obtained by particle swarm algorithm (PSA) to minimize the acceleration transfer function. To determine the dynamic response of a 40-story building under the influence of SSI, six different foundation soil conditions and eight different earthquake records are considered. The results show that the SSI effects on the dynamic response of the high-rise building resting on relatively soft soil types such as SD and SE are of critical importance. It is shown that the effectiveness of the optimum TMD designed by OF-1 is better than the others in suppressing the peak response values for all soil types. After OF-1, the best performances are obtained for OF-3 and OF-5 which yield approximately the same effectiveness. It is also found that different earthquake records, soil types and objective functions are very effective on the effectiveness of TMD.
- MakaleAçık Erişim2021Optimum passive tuned mass damper systems for main structures under harmonic excitation
Araz, Onur
To increase the effectiveness and robustness of a single Tuned mass damper (TMD), TMDs are connected in series or parallel to the main system. Unlike parallel TMDs (PTMD), series TMDs (STMD) consist of only two different TMD units, each of which is connected to the main structure in series. The optimum parameters of series and parallel TMDs are obtained by using the simulated annealing (SA) algorithm in this study. It is aimed to minimize the displacement in the main system in obtaining the optimum parameters. Also, the explicit formulas that can be easily used for the optimum design of both TMD devices are derived using the curve-fitting technique. The control performance of the optimum STMD device is confirmed through numerical analyses and compared with classical TMD and PTMD.
- MakaleAçık Erişim2021Effect of Vehicle-Bridge Interaction on the Dynamic Behavior of Bridges
Araz, Onur
In this study, dynamic behavior of single span bridges under moving sprung mass is investigated. The equation of motion of the problem under consideration is obtained as a partial differential equation with variable coefficients and solved numerically by Newmark method. In dynamic analyzes, the effects of the speed parameter, mass ratio, frequency ratio and damping ratio of the bridge on the dynamic behavior of the bridge and the vehicle are investigated. The results obtained from the analysis are presented in figures and tables. The results have shown that the parameters taken into account have a significant influence on the dynamic behavior of the bridge.
- MakaleAçık Erişim2021Optimization of non-traditional tuned mass damper for damped structures under harmonic excitation
Kahya, Volkan; Araz, Onur
Tuned mass dampers (TMDs) are used to reduce dynamic vibrations of structures under environmental loads such as wind or seismic excitation. In this paper, the optimum design of nontraditional tuned mass dampers (NT-TMD) attached to a damped main structure under harmonic excitation was investigated. Unlike the traditional TMD, the damping element in NT-TMD is directly connected to the ground. In this study, the effectiveness of NT-TMD on the attenuation of vibrations on the damped main system under harmonic load is investigated. The optimum parameters of the NT-TMD are obtained by using the hybrid pattern search (HPS) technique. According to numerical results, it is seen that non-traditional TMD is more effective than traditional TMD in reducing vibration.
- MakaleAçık Erişim2021Optimization of three-element tuned mass damper for single degree of freedom structures under ground acceleration; [Yer ivmesi etkisi altındaki tek serbestlik dereceli yapılar için üç elemanlı ayarlı kütle sönümleyicinin optimizasyonu]
Araz, Onur
Passive control devices have been used for a long time to reduce unwanted vibrations. The most commonly used of these devices are tuned mass dampers. The optimum parameters of the three-element tuned mass damper for damped main structures due to ground acceleration are investigated in this paper. Unlike the traditional tuned mass damper, the three-element tuned mass damper contains two spring elements and one of them is connected in series with the damping element. The optimum parameters are obtained by simulated annealing algorithm. Numerical results show that the three-element tuned mass damper is very effective in reducing dynamic vibrations of the damped structures.
- MakaleYalnız künye2021Design of series tuned mass dampers for seismic control of structures using simulated annealing algorithm
Araz, Onur; Kahya, Volkan
The effectiveness of the series tuned mass dampers (STMDs) in reducing the dynamic vibrations of the structures under the ground motion is investigated, and their optimum parameters are obtained based on the simulated annealing (SA) optimization. The STMD is one of the most well-known passive control devices which consists of two TMD units arranged in series. However, only a few studies are available on the control performance and optimum parameters of the STMDs for structural systems subjected to ground motion. Thus, the goal of this study is to carry out a thorough optimization analysis based on the SA algorithm for the structures equipped with an STMD under the effect of ground motion. The objective function is selected as the reduction of the displacement response of the structure. It is proved that the optimum STMD has better effectiveness than the optimum TMD in suppressing the maximum story displacement of the structure. Further, the effect of the frequency shift on the effectiveness of the optimally designed STMD is investigated.
- MakaleYalnız künye2020Series tuned mass dampers in vibration control of continuous railway bridges
Araz, Onur; Kahya, Volkan
This paper presents the applicability of series tuned mass dampers (STMDs) to reduce the multiple resonant responses of continuous railway bridges under high-speed train. The bridge is modeled by two-span Bernoulli-Euler beam with uniform cross-section, and a STMD device consisting of two TMD units installed on the bridge to reduce its multiple resonant vibrations. The system is assumed to be under the action of a high-speed train passage which is modeled as a series of moving forces. Sequential Programming Technique (SQP) is carried out to find the optimal parameters of the STMD that minimizes the maximum peak responses of the bridge. Comparisons with the results available in the literature are presented to demonstrate the effectiveness and robustness of STMD system in reducing the multiple resonant responses of the continuous railway bridges under high-speed trains.
- MakaleAçık Erişim2020A simple design method for multiple tuned mass dampers in reduction of excessive vibrations of high-speed railway bridges; [Yüksek hızlı demiryolu köprülerinde aşırı titreşimlerin azaltılmasında paralel bağlı ayarlı kütle sönümleyiciler için basit bir tasarım yöntemi]
Kahya, Volkan; Araz, Onur
In this study, a simple method is proposed to obtain the optimum design parameters of vibration absorbers consisting of several tuned mass damper units connected each other in parallel. The method is essentially the extension of the formulas proposed by Den Hartog for single degree-of-freedom tuned mass dampers to multiple tuned mass dampers. To demonstrate the effectiveness of the proposed method, an application to high-speed rail bridges are made. The bridge is modeled as a simple Euler-Bernoulli beam, and the train is modeled as a series of moving loads. The equations of motion are solved numerically by the Newmark method. The results of the study showed that multiple tuned mass dampers designed by the proposed method show good performance in reducing the resonance vibrations in high-speed rail bridges.
- MakaleYalnız künye2020Effect of detuning conditions on the performance of non-traditional tuned mass dampers under external excitation
Araz, Onur
The tuned mass damper (TMD) is a widely used passive control device which is attached to a main system to suppress undesired vibration. In this paper, a non-traditional form of TMD system is investigated. Unlike the traditional TMD configuration, the considered TMD system has a linear viscous damper connecting the absorber mass directly to the ground instead of the main mass. There have been some studies on the optimization design of the non-traditional TMD (NT-TMD) for undamped main structures. Those studies have indicated that the NT-TMD provides better performance than the traditional TMD does. When there is a frequency shifting in the structural frequency or tuning frequency of TMD, to the best knowledge of the authors, there has been no study on the performance of the NT-TMD. The main idea of the study is to investigate the effect of frequency detuning on the control performance of the NT-TMD. The optimum parameters of the NT-TMD system and corresponding effectiveness are obtained for different mass ratios of the NT-TMD system. The numerical results indicate that the NT-TMD with high mass ratio provides better robustness to the changes in the target frequency ratio than the traditional TMD.
- MakaleYalnız künye2019A SEQUENTIAL APPROACH BASED DESIGN OF MULTIPLE TUNED MASS DAMPERS UNDER HARMONIC EXCITATION
Kahya, Volkan; Araz, Onur
This study evaluates the response reduction effect of single-degree-of-freedom (SDOF) primary systems with multiple tuned mass dampers (MTMDs) under harmonic excitation. To design MTMD, TMD properties are re-calibrated based on the natural frequencies of the system on which the number of TMDs is one less than the current system. This is a sequential approach that does not require any iteration for each step. Instead it requires starting from the case with single TMD, and then increasing the numbers of TMDs one more at a time until the desired number is reached. Using the obtained design parameters, the effectiveness and robustness of the MTMDs are studied in comparison to MTMDs designed by previous works available in the literature. As a result, the proposed design procedure produces an effective multiple tuned mass damper to be utilized in a SDOF system under harmonic excitation. Additionally, the proposed approach provides a simple way to design the MTMD system than the traditional optimization methods, thus it significantly reduces the computation effort in the design process.
- MakaleYalnız künye2017Series tuned mass dampers in train-induced vibration control of railway bridges
Kahya, Volkan; Araz, Onur
This paper presents the series multiple tuned mass dampers (STMDs) to suppress the resonant vibrations of railway bridges under the passage of high-speed trains (HSTs). A STMD device consisting of two spring-mass-damper units connected each other in series is installed on the bridge. In solution, bridge is modeled as a simply-supported Euler-Bernoulli beam with constant cross-section, and vehicle is simulated as a series of moving forces with constant speed. By the assumed mode method, the governing equations of motion of the beam-TMD device coupled system traversed by a moving train are obtained. The optimum values for the parameters of the STMD device are obtained for the criterion based on the minimization of the maximum dynamic displacement of the beam at its midspan. Single TMD and multiple TMDs in parallel are also considered for demonstration of the STMD device's performance. The results show that STMDs are effective in bridge vibration suppression and robust to parameters' change in the main system and the absorber itself.
- MakaleYalnız künye2015RESONANT VIBRATIONS OF TWO-SPAN RAILWAY BRIDGES UNDER HIGH-SPEED TRAINS
Kahya, Volkan; Araz, Onur; Turan, Muhittin
In this study, resonant vibrations of two-span railway bridges subjected to high-speed trains (HSTs) are studied. The continuous beam is modelled by using Bernoulli-Euler beam theory, and the train is considered as a series of moving concentrated loads. The dynamic response is obtained analytically by using the assumed mode method. Effects of the speed parameter and the span to car length ratio on the response are examined. Numerical results show that the above mentioned parameters play very important role on the dynamic behavior of two-span bridges.