• Structural Engineering and Mechanics
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• v.56 no.4
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• pp.569-588
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• 2015

A comprehensive methodology is proposed for design of metallic dampers in seismic retrofit of earthquake-damaged frame structures. It is assumed that the metallic dampers remain elastic and only provide stiffness during frequent earthquake (i.e., earthquake with a 63% probability of exceedance in 50-year service period), while in precautionary earthquake (i.e., earthquake with a 10% probability of exceedance in 50-year service period), the metallic dampers yield before the main frame and dissipate most of the seismic energy to either prevent or minimize structural damages. Therefore by converting multi-story frame to an equivalent single-degree-of-freedom system, the added stiffness provided by metallic dampers is designed to control elastic story drifts within code-based demand under frequent earthquake, and the added damping with the combination of added stiffness influences is obtained to control structural stress within performance-based target under precautionary earthquake. With the equivalent added damping ratio, the expected damping forces provided by metallic dampers can be calculated to carry out the configuration and design of metallic dampers along with supporting braces. Based on a detailed example for retrofit of an earthquake-damaged reinforced concrete frame by using metallic dampers, the proposed design procedure is demonstrated to be simple and practical, which can not only meet current China's design codes but also be used in retrofit design of earthquake-damaged frame with metallic damper for reaching desirable performance objective.

• Earthquakes and Structures
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• v.13 no.4
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• pp.397-407
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• 2017

With the growing demand for metallic dampers in engineering practice, it is urgent to establish a reasonable approach to evaluating the mechanical performance of metallic dampers under seismic excitations. This paper introduces an effective method for parameter identification of the modified Bouc-Wen model and its application to evaluating the fatigue performance of metallic dampers (MDs). The modified Bouc-Wen model which eliminates the redundant parameter is used to describe the hysteresis behavior of MDs. Relations between the parameters of the modified Bouc-Wen model and the mechanical performance parameters of MDs are studied first. A modified Genetic Algorithm using real-integer hybrid coding with relative fitness as well as adaptive crossover and mutation rates (called RFAGA) is then proposed to identify the parameters of the modified Bouc-Wen model. A reliable approach to evaluating the fatigue performance of the MDs with respect to the Chinese Code for Seismic Design of Buildings (GB 50011-2010) is finally proposed based on the research results. Experimental data are employed to demonstrate the process and verify the effectiveness of the proposed approach. It is shown that the RFAGA is able to converge quickly in the identification process, and the simulation curves based on the identification results fit well with the experimental hysteresis curves. Furthermore, the proposed approach is shown to be a useful tool for evaluating the fatigue performance of MDs with respect to the Chinese Code for Seismic Design of Buildings (GB 50011-2010).

• Structural Engineering and Mechanics
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• v.17 no.2
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• pp.187-201
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• 2004

A shaking table test on a three-story one-bay steel frame model with metallic yield dampers and their parallel connection with oil dampers is carried out to study the dynamic characteristics and seismic performance of the energy dissipation system. It is found from the test that the combined energy dissipation system has favorable reducing vibration effects on structural displacement, and the structural peak acceleration can not evidently be reduced under small intensity seismic excitations, but in most cases the vibration reduction effect is very good under large intensity seismic excitations. Test results also show that stiffness of the energy dissipation devices should match their damping. Dynamic analysis method and mechanics models of these two dampers are proposed. In the analysis method, the force-displacement relationship of the metallic yield damper is represented by an elastic perfectly plastic model, and the behavior of the oil damper is simulated by a velocity and displacement relative model in which the contributions of the oil damper to the damping force and stiffness of the system are considered. Validity of the analytical model and the method is verified through comparison between the results of the shaking table test and numerical analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.254-262
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• 2011

The purpose of this study is the development of V shaped metallic damper, which is superior than slit damper in energy dissipation capacity. For this purpose, 9 metallic damper specimens were prepared and shear testing were performed. According to test results, the V shaped metallic damper with strut height of 270mm and strut angle of $60^{\circ}$ shows a better seismic performance than any other specimens. The result of comparison with the yield strength of the dampers using the existing strength formula shows that V type metal dampers were highly evaluated than others within analyzing existing experimental result.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.2
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• pp.82-88
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• 2010

The purpose of this research is a seismic capacity evaluation and strengthening of existing railway station buildings, which were constructed before the seismic design code activated. The seismic capacity of 2nd story RC station building is evaluated by using nonlinear time-history analysis. Analysis results are checked by story drift ratio and story shear, which are described in design code. As a result, the story shears are exceeding the base shear of the design code, the appropriate seismic strengthening methods are needed. To improve the seismic capacity, metallic dampers are used. Evaluation parameters are metallic damper shape and damper installation methods. Dampers are installed in four places in X and Y directions of station buildings. By reviewing of time-history analysis results, the metallic damper, which is installed inverted K-brace type, shows a better seismic performance than other damper shape and installation methods.

• International journal of steel structures
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• v.18 no.5
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• pp.1741-1753
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• 2018

Metallic dampers are sacrificial devices (fuses) that dissipate significant energy during earthquakes while protecting other parts of structures from possible damage. In addition to numerous implementation opportunities of other base isolation systems, U-shaped dampers (UD) are one of the widely investigated and used devices in practice especially in Japan. The present study focuses on enhancing seismic performance of these types of dampers by changing their geometric properties. UDs with perforated (i.e. with holes) and/or nonparallel arms are developed for this purpose. For a better comparison, the criterion of equal material volume (or mass) has been utilized. Three dimensional finite element models of the new type of UDs are formed and investigated numerically under selected displacement histories. Based on the obtained hysteretic curves; dissipated energy intensities, effective stiffness ratios, reaction forces, effective damping ratios are evaluated in this parametric study. It is found that both damper types have merits in use of seismic applications and that the selection of the damper configuration is dependent on the design specific issues.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.199-208
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• 2011

The purpose of this study is to evaluate of the strength and deformation capacity of metallic dampers with the variable slit shape. For this purpose, 12 metallic damper specimens were prepared and shear testing was performed. According to the test results, the S shaped metallic damper with the strut height of 200mm and angle of $60^{\circ}$ shows better hysteretic performance than any other specimens. By making a comparison between the yield strength in test and the proposed strength formula, test results shows larger yield strength than calculation method.

• Earthquakes and Structures
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• v.14 no.1
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• pp.1-10
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• 2018

Seismic retrofitting of existing buildings and design of earth-quake resistant buildings are important issues associated with earthquake-prone zones. Use of metallic-yielding dampers as an energy dissipation system is an acceptable method for controlling damages in structures and improving their seismic performance. In this study, the optimal distribution of dampers for reducing the seismic response of steel frames with multi-degrees freedom is presented utilizing the uniform distribution of deformations. This has been done in a way that, the final configuration of dampers in the frames lead to minimum weight while satisfying the performance criteria. It is shown that such a structure has an optimum seismic performance, in which the maximum structure capacity is used. Then the genetic algorithm which is an evolutionary optimization method is used for optimal arrangement of the steel dampers in the structure. In continuation for specifying the optimal accurate response, the local search algorithm based on the gradient concept has been selected. In this research the introduced optimization methods are used for optimal retrofitting in the moment-resisting frame with inelastic behavior and initial weakness in design. Ultimately the optimal configuration of dampers over the height of building specified and by comparing the results of the uniform deformation method with those of the genetic algorithm, the validity of the uniform deformation method in terms of accuracy, Time Speed Optimization and the simplicity of the theory have been proven.

• Steel and Composite Structures
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• v.53 no.1
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• pp.29-43
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• 2024

In this paper, the behavior of an innovative metallic a butterfly-shaped link as damper with shear and flexural mechanism was investigated experimentally and numerically. The damper is directly attached to the diagonal member of the Concentrically Braced Frame (CBF) to prevent buckling of the braces. Since it is expected that nonlinear behavior of the system is limited to the dampers, the other parts of structures remind elastic that the damper can replaced easily after a severe earthquake. The experimental outcomes indicated that both types of dampers (with shear or flexural mechanism) pertain to stable hysteresis loops without any significant degradation in stiffness or strength. Comparing the dampers indicated that the shear damper has a greater ultimate strength (4.59 times) and stiffness (3.58 times) than flexural damper but a lower ductility (16%) and ultimate displacement (60%). Also, the shear damper has a considerable dissipation energy 14.56 times greater than flexural dampers where dissipating energy are affected by ultimate strength, stiffness and ultimate displacement. Also, based on the numerical study, the effect of main plate slenderness on the behavior of the damper was considered and the allowable slenderness was suggested to the design of the dampers. Numerical results confirmed that the flexural damper is more sensitive to the slenderness than shear damper. Accordingly, as the slenderness is less than 50 and 30, respectively, for, shear and flexural damper, no degradation in ultimate strength is realized. By increasing the slenderness, the maximum reduction of the ultimate strength, stiffness, and energy dissipation capacity reached by 16%, 7%, and 17% for SDB dampers whereas it is 3%, 33%, 20%, and 45% for MDB.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.123-130
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• 2010

The aim of this paper is a seismic performance evaluation of metallic damper devices which are efficient in workability and installation process. For this V shape and S shape dampers is considered. The strut figures of dampers are V shape and S shape and, the research parameters are strut height and angle of the dampers. ABAQUS program is used for nonlinear finite element analysis. The analysis is performed with the hysteretic curve that has maximum displacement with 50mm and has increased progressive. As a results of evaluating the yield strength, maximum strength and energy dissipation capacity of each device, V and S shape have a good strength capacity and the devices with strut angle $60^{\circ}$ and strut height 140 and 200mm are evaluated stable in seismic behaviors. The response of S shape is more efficient than that of V shape. In the yield strength estimation process, proposed formula can not estimate the yield strength of V and S shape dampers. Even though, the formula can not consider the variation of strut heights and strut angles. Finally the S shape damper is recommended in seismic performance than V shape damper.