viscous dampers

Viscous dampers are one of the passive control systems that reduce the seismic demand of the structural elements of a building and minimize the building damage. However, the proper arrangement of viscous dampers greatly affects their increased performance, and it is not economical to use viscous dampers in all floors. In this study, the viscous dampers are designed according to four distribution methods based on FEMA 356: uniform damping coefficient distribution, distribution proportional to shear force of floors, distribution based on shear strain energy of floors and distribution based on shear strain energy of effective floors. In order to find the optimal distribution method, the seismic responses of the structure including the maximum drift ratio, maximum relative acceleration of floors, and strain energy are extracted and the results obtained from the rehabilitation in the four methods are compared with the proposed performance indices. Considering the effect of each method of damping coefficient distribution on the structural performance indices, it can be argued that the damping coefficient distribution based on the effective floors has a more appropriate performance compared to other methods of damping coefficient distribution. The results of time history analysis show that the viscous dampers used in the benchmark buildings cause a 50% improvement in the performance index of mid- and high-rise structures and also a 40% improvement in the force index of mid- and high-rise structures under the far-field acceleration.

During the recent two decades, many structures have become in need for seismic retrofit due to changes in either requirements of relevant seismic codes or the building usage. Viscous dampers are increasingly employed for seismically retrofitting various structures thanks to their easy installation and minimum intervention into the existing structure while significantly improving the seismic performance of the building. The main objective of this paper is to present a new design procedure for the evaluation of probabilistic seismicity of steel structures equipped with nonlinear viscous dampers. For this purpose, numerical investigation was conducted on, as benchmark structures, three steel-made moment-resistant frames with 3, 9, and 20 stories. Due to significant differences in their dynamic characteristics, these three structures represented low-rise, mid-rise, and high-rise buildings, respectively. Nonlinear time history analysis was performed using two near-field and two far-field accelerograms at various intensities (making up a total of 10 accelerograms). Moreover, nondimensional analysis was done to evaluate the uncertainties associated with velocity exponent of the nonlinear viscous dampers. Next, probabilistic estimation of damages occurred to the benchmark structures was performed and the effect of the uncertainty associated with the dimensionless power intensity of the damper on the seismic response of the structure. Investigating the results of the seismic analysis for viscous dampers at power intensities of 0.2, 0.3, and 0.4, it was found that although the seismic retrofit had significantly improved the seismic performance in all model structures but the proposed design procedure was more effective in the retrofitted high-rise structures at the power intensity of 0.4.

Using control devices to enhance system identification and damage detection in a structure requiring both vibration control and structural health monitoring is an interesting yet practical topic. In recent decades several independent research studies have been conducted on the semi-active vibration control and health monitoring of the civil structures subjected to earthquakes, whereas both require similar software. Therefore, where there is a need for both vibration control and health monitoring systems in a building structure, integrating both systems using common equipment would be economical. Application of the viscous dampers for control of buildings, due to their proper seismic performance, lack of significant increase in the structural mass, and least interference with the present situation of the building is rapidly increasing. For this reason, the main goal of this research is to present a new integrated procedure for simultaneous health monitoring and semi-active control of the building structure using the viscous dampers with variable damping coefficients. Next, a scheme is presented for updating the building characteristic matrices and identifying the structural parameters. Finally, according to the updated system matrices, the efficiency of semi-active viscous dampers is investigated. For this purpose, a linear quadratic regulator optimal control algorithm is used for a building subjected to seismic excitations. The results show that the structural parameters are accurately identified; and, at the same time, the building structural vibration is significantly reduced.

Nowadays, the use of control systems in buildings has been increased and the importance of vibration reduction of structures is considered more than ever. In addition to improve the dynamic behavior of buildings, control systems can be installed between adjacent buildings as activated, semi-active and inactivated systems. Fluid viscous dampers are one of the most important approaches for inactivated control systems in which the dynamic response of two adjacent buildings reduces according to the high resistance of the viscous fluid. The main purpose of this study is the use of control systems in two similar adjacent buildings to reduce the entire system response which will be the analytical study of the impact of viscous dampers to control system performance. In order to provide the analysis and to study the dynamic behavior improvement of different adjacent buildings connected with dampers, two models of the original sample was investigated. All examples are different from each other and response analysis and time history was provided using SAP 2000 software. According to the acquired results, the effect of fluid viscous dampers for tall buildings is less than the shorter ones. Moreover, these dampers are more efficiently working for adjacent buildings with different heights rather than buildings with the same height.

The fragility curves are used to indicate the probability of damage to buildings during the earthquakes with different intensities. The main objective of this study is to present a new design procedure for exploring the effectiveness of using viscous dampers in the seismic rehabilitation of steel structures using the seismic fragility analysis. In addition, a straightforward formula is presented to determine the effectiveness of seismic rehabilitation of steel structures with viscous dampers. The inter-story drift as one of the effective parameters for assessing the safety of buildings after an earthquake is used in this study as a damage index. To compare the damage probability of buildings with and without damper, three 3, 9 and 20-story benchmark buildings are used. Furthermore, the earthquake records corresponding to three levels of seismic hazard are used for the nonlinear dynamic analysis. Comparison of the fragility curves between the steel structures controlled and the buildings without the damper shows a significant decrease in the damage probability after the rehabilitation with the viscous dampers. The results of numerical analysis showed that although seismic rehabilitation in all benchmark buildings led to the improved seismic performance, the decrease in the response of the 9-story structure is higher compared to the other buildings.