Fluid Viscous Dampers Research Articles

Evaluation of energy-dissipating devices in high-rise RC core wall buildings

Energy-dissipating devices (EDDs) are used to control the dynamic response of high-rise buildings in moderate to severe seismic risk areas. These systems can be effectively analysed using a rigorous non-linear response history analysis (NLRHA) procedure. However, expertise and time is required to perform and interpret the results from this procedure since several trials are required to select the most effective size and location of the dampers. In this study, the validity of the modal strain energy (MSE) method and the logarithmic decrement (LD) method was checked using a case study of a 40-storey reinforced concrete (RC) core wall building equipped with buckling-restrained braces (BRBs) and fluid viscous dampers (FVDs). Linear and non-linear models of the building including dampers were prepared. The elastic dominant modes and their target displacements were then determined using a response-spectrum analysis procedure. The MSE and LD methods were used to determine the equivalent damping ratio and the time period for BRBs and FVDs, respectively. The base shear and roof displacement, determined using modal and spectral parameters against these damping and time = period values, were found to match those determined using NLRHA with an accuracy of 5–10% and 20–30%, respectively. This study is helpful for the preliminary sizing of EDDs.

Effectiveness of fluid viscous damper for steel frame building subjected to earthquake load

Since the appearance of the first modern multistories buildings, besides the demand of ensuring the bearing capacity, one of the urgent problems facing the engineer is to do how to design structure to ensure the requirements of normal use such as displacement, motion acceleration within permissible limits. There exist many methods to reduce these response of structure under lateral load. Among these, using fluid viscous damper (FVD) is one of the most applied equipment because of its simplicity. This paper presents the examination of eight-story steel frame structure subjected to seismic load. The FVD system is defined in Etabs with link properties. In each story, four dampers are located in each direction of plan, with two on each side of the center of stiffness of the story. The time history analysis was conducted to study the structure subjected to seimic load collected from the function library of program Etabs. The effect of FVD system was determined by the dynamic response of the building and displacement indexes such as maximum displacement of roof, story drift ratio. The results show that, all the dynamic response characters of structure were decreased significantly when providing the FVD to it.

Seismic performance of reinforced concrete tall buildings with conventional and non-conventional construction systems

Currently in the city of Lima there is a limited number of high-rise buildings. Therefore, there is not much literature on this type of building in Peru. Peruvian codes focus on medium and low-rise buildings. For this reason, studies are required to analyze and design these tall buildings more appropriately according to the reality of the country. In this article, a pushover modal analysis of 6 types of 35-Story reinforced concrete buildings in the city of Lima will be developed. Three building models with different structural systems and square and rectangular plan are proposed, being the areas of 29m × 29m and 52m × 26m respectively. These structural systems are rigid core and frames with an energy dissipation system (fluid viscous dampers and shear-link-bozzo dissipators SLB) in order to study their behavior against seismic stresses. These buildings were based on the criteria and requirements of the current codes in the country as well as the distribution of the floor plan of buildings commonly used for offices and homes. Natural periods (T) were found to range from 2.6 to 3.3 seconds for rigid core buildings. There is an increase for viscous damping buildings from 4.2 to 5.4 seconds and also for SLB devices to range from 3.7 to 4.6 seconds. In turn, modal static nonlinear analysis was performed to obtain the capacity curves for each type of building, which were compared with the seismic demands according to the design provisions of the Peruvian seismic standard E.030 and an average of design spectra. of acceleration records of severe seismic events in Peru and scaled in a range of 0.2T to 1.5T. The performance points for each building case were determined following the ATC-40 methodologies, finding that tall buildings with a rigid core have approximately twice the stiffness of buildings with SLB dampers, as well as low ductility, unlike buildings with dissipators, that have a high ductility.

Research on nonlinear stiffness and damping of bellows-type fluid viscous damper

Micro-vibrations in satellites mainly originate from the control moment gyroscope because of its mass imbalance, which seriously affect the image accuracy of high-resolution optical payload, so it must be isolated. Bellows-type fluid viscous damper (FVD) can be used to isolate micro-vibrations. In this paper, a simplified model of the damping element in bellows-type FVD under medium- and high-frequency excitation is proposed according to the concept of bellows effective area. Based on this theoretical model, nonlinear stiffness and damping at different design parameters are extracted by nonlinear fitting method. Then, the main cause of nonlinear stiffness and damping is analyzed by the velocity distribution in the cross section of damping orifice. The factors that affect the intensity of nonlinear stiffness and damping are discussed by using the flow resistance. The results show that the velocity term in the corrected hydraulic resistance is the cause of nonlinear damping and stiffness. Damping orifice diameter, length and silicone oil viscosity will affect the intensity of nonlinear characteristics of this damper. At low viscosity, the nonlinear damping is more obvious. The larger the diameter, the more obvious the nonlinear damping. In the frequency domain between 1 and 200 Hz, the velocity index is not a constant, but changes with frequency. Hydraulic stiffness can be divided by linear stiffness and nonlinear stiffness; both of them can affect the elastic force.

Enhancing Seismic Resistance of G+10 MSB by Introducing FVD System

Lateral load resisting systems (LLRS) play a key role in reducing or eliminating the damage of the structure due to the earthquake. The damping system is one of the LLRS which controls the vibrations when an earthquake occurs. Fluid Viscous damping decreases tension and deflection because due to flexing the columns, the energy from the damping is totally out of phase with stresses. This is valid only for viscous fluid damping, where the damping force varies with the velocity of the stroke. Other types of damping do not vary their performance with velocities, such as yielding components, friction devices, plastic hinges, and visco-elastic elastomers; hence, they can increase column stress while reducing deflection, and typically do so. While coming to this work, under the seismic coefficient method for seismic zone-5, G+10 multistoried buildings were modelled and analyzed in ETABS along with limit state of collapse and limit state of serviceability load combinations. The response of the building was examined by introducing viscous dampers to the structure by varying the position of FVD in the building (S-1, S-2, and S-3), which are regular and irregular in plan, and by altering the width of the bay, by inserting the dampers at the four corners of the building in the first stage, by inserting the dampers at the four edges of the building in the second stage (S-2), and by inserting the dampers at the centre of the building in the third stage (S-3). Dampers are introduced from top to bottom storey of the building. Placement of FVD device system plays a key role against earthquake forces which are acting on the structure during the event of an earthquake. After the comparison in between above-defined stages and various parameters, when dampers are inserted at the edges of the building (S-3), the entire building is displaced identically with lesser values of displacement and inter-storey drifts, which are significant parameters in the event of an earthquake.

System-based probabilistic evaluation of longitudinal seismic control for a cable-stayed bridge with three super-tall towers

The system fragility method was used to evaluate the seismic structural systems and seismic mitigation devices for a cable-stayed bridge with three super-tall towers. Firstly, a three-dimensional numerical model of a four-span cable-stayed bridge with middle-tower height of 332 m was simulated using OpenSEES, which accounted for the material and geometric nonlinearities; 80 actual ground motions were chosen for conducting time history analysis. Secondly, the fragility curves of the components and the system were derived using general fragility theory and Product of the Conditional Marginal theory, respectively. Then, three longitudinal seismic structural systems were evaluated. Finally, under the optimal seismic structural system, the optimal parameters of the longitudinal fluid viscous damper and cable restrainer were obtained using the response surface method, and the mitigation effects of the fluid viscous damper and the cable restrainer with optimal parameters were compared using fragility curves. The results show that different structural systems and mitigation devices have significant influence on the damage control of displacement and stay cable force. The super-tall tower cable-stayed bridge with a partial constraint system of the consolidated middle tower and floating side towers has the lowest damage probability; and the longitudinal fluid viscous damper and cable restrainer can achieve a certain mitigation effect, however, the fluid viscous damper has better effect. Therefore, the partial constraint system and fluid viscous damper should be used in the longitudinal direction of the multiple super-tall-tower cable-stayed bridge.

Influence of Nonlinear Fluid Viscous Dampers on Seismic Response of RC Elevated Storage Tanks

The numerical investigation on the seismic response of RC elevated liquid storage tanks installed with viscous dampers is presented. A discrete two-mass model for the liquid and multi-degree of freedom system for staging, installed with the dampers are developed for Reinforced Concrete (RC) elevated liquid storage tanks. The elevated tank is assessed for seismic response reduction when provided with Linear Viscous Damper (LVD) and Nonlinear Viscous Damper (NLVD), installed in the staging. The RC elevated liquid storage tanks are analyzed for two levels of liquid containment in the tank, 100% and 25% of the tank capacity. Three Configurations of placements of dampers viz. dampers at alternate levels (Configuration I and Configuration II) and dampers at all the panels of the staging of the tank (Configuration III) are considered. To study the effect of peak ground acceleration, eight real earthquake time histories with accelerations varying from 0.1 g to 0.93 g are considered. The nonlinearity in the viscous damper is modified by taking force proportional to various velocity exponents. It is found that the nonlinear viscous dampers with lower damping constant result in a comparable reduction in the response of RC elevated liquid storage tank, to that of linear viscous dampers with higher damping constant. A lower damping constant signifies compact the size of the damper. Doi: 10.28991/cej-2020-SP(EMCE)-09 Full Text: PDF

Dissipative Bracing Systems for Seismic Upgrading of New and Existing Timber Structures

ABSTRACT In view of the development of heavy timber seismic-resistant structures, in the context of modern seismic design approach, a possible solution is to allow the timber structure to dissipate a part of the seismic energy. Since timber is a material with an elastic-fragile behaviour, the dissipative function should be delegated to connections, through plastic deformation of steel connectors. However, joints are primary structural elements, with a crucial role in bearing the design loads. Therefore, the role of seismic energy dissipation should be conveniently assumed by ad hoc devices. In this context, the paper deals with the application of fluid viscous dampers (FVD) to timber frames: FVDs dissipate seismic energy, while timber elements and steel connections remain elastic. Specifically, 2D single-storey structures with dissipative bracing systems, equipped with FVDs, in different configurations, are studied, assuming several rates of possible dampings. Non-linear dynamic time history analyses are performed (SAP2000, v18). Results are discussed showing significant reduction of the structural mass compared to the non-dissipative ones, recentering capability of the structures, high dissipative capacity, simpler elastic connections. The reduction of production and maintenance costs follows. All these involve the efficiency of the structural performance and sustainability under earthquakes.

Seismic Control of a Self-Anchored Suspension Bridge Using Fluid Viscous Dampers

A self-anchored suspension bridge balances forces internally without external anchorage requirements, making it suitable for sites where anchorages would be difficult to construct. It often adopts either a full-floating or a semi-floating tower-girder connection system, which may result in large displacement responses along bridge longitudinal direction during earthquakes. This study investigated the efficacy of using the fluid viscous damper (FVD) for seismic control of a single-tower self-anchored suspension bridge. First, the energy dissipation behaviors of the FVD under sinusoidal excitations were studied. It revealed that besides the damper parameters (i.e. damping coefficient and velocity exponent) of an FVD itself, the energy dissipation capacity also relies on the characteristics of external excitations. Therefore, optimum damper parameters added to a structure should be determined on a case-by-case basis. Parametric study was then carried out on the prototype bridge, which indicated a tendency of decreasing the longitudinal deck/tower displacements and tower forces with increasing damping coefficient [Formula: see text] and decreasing velocity exponent [Formula: see text]. Compared with the linear FVD, the nonlinear FVD with a smaller velocity exponent can develop more rectangular force-displacement loops and thus achieve better energy dissipation performance. With selected optimum damper parameters (i.e. [Formula: see text][Formula: see text]kN[Formula: see text]m[Formula: see text][Formula: see text]s[Formula: see text] and [Formula: see text]) for the two FVDs added between the deck and the tower, the longitudinal deck and tower displacements could be reduced by 54%, while the peak bending moment and shear force at the tower base could be reduced by 30% and 19%, respectively. It is concluded that the nonlinear FVD can provide a simple and efficient solution to reduce displacement responses of self-anchored suspension bridges while simultaneously reducing the bending moment and shear force in the tower.

Probability-based evaluation of the effect of fluid viscous dampers on a high-speed railway bridge

One approach for upgrading existing high-speed railway bridges which are susceptible to excessive vibrations is to install damping devices. In this article, a model of a simply supported bridge with supplemental fluid viscous dampers installed between the superstructure and the abutments is derived based on an arbitrary mode of vibration. The aim is to ensure the robustness of the proposed vibration mitigation method by conducting Monte Carlo simulations including uncertainties associated with the bridge-damper system. From this statistical screening, it is possible to evaluate the probability of exceedance of a stipulated acceleration level, as well as studying the sensitivity of the ingoing random variables. This probabilistic evaluation highlights the necessity of conducting a statistical assessment to determine an estimate for the distribution of the acceleration limit and model uncertainty for dynamic analyses. The results show that the required damping coefficient could be multiply reduced, as compared to a deterministic analysis.

Effects of Dissipative Systems on the Seismic Behavior of Irregular Buildings—Two Case Studies

Conservation of heritage buildings has become a very important issue in many countries, as it is in Italy, where a great number of existing buildings of historical–artistic importance are seismically vulnerable. To improve existing building behavior, researchers focus on the design of retrofit interventions. This paper presents the application of energy dissipation devices in the retrofit of two existing Reinforced Concrete (RC) buildings, both irregular in plan and along their heights, designed for gravitational loads only. These buildings are representative of Italian public housing built in the 1960s and early 1970s. Technical information and mechanical properties of materials are presented, and non-linear analyses are carried out to evaluate the buildings’ behavior under earthquake loads. Many of their structural members do not satisfy the verifications required by the Italian Building Code. Retrofit interventions with buckling-restrained axial dampers in one building and viscous fluid dampers in the other are proposed. The verifications of the retrofitted buildings and the amount of the energy absorbed by the devices with respect to that absorbed by the unretrofitted buildings show the effectiveness of the proposed interventions. Moreover, it is demonstrated that adequate dispositions of the dissipative devices in plan and along the height increase the torsional stiffness of the buildings, improving their structural response under seismic action.

Investigating the effects of structural pounding on the seismic performance of adjacent RC and steel MRFs

An insufficient separation distance between adjacent buildings is the main reason for structural pounding during severe earthquakes. The lateral load resistance system, fundamental natural period, mass, and stiffness are important factors having the influence on collisions between two adjacent structures. In this study, 3-, 5- and 9-story adjacent reinforced concrete and steel moment resisting frames (MRFs) were considered to investigate the collision effects and to determine modification factors for new and already existing buildings. For this purpose, incremental dynamic analysis was used to assess the seismic limit state capacity of the structures using a developed algorithm in OpenSees software including two near-field record subsets suggested by FEMA-P695. The results of this paper can help engineers to approximately estimate the performance levels of MRFs due to pounding phenomenon. The results confirm that collisions can lead to the changes in performance levels, which are difficult to be considered during the design process. In addition, the results of the analyses illustrate that providing a fluid viscous damper between adjacent reinforced concrete and steel structures can be effective to eliminate the sudden changes in the lateral force during collision. This approach can be successfully used for retrofitting adjacent structures with insufficient in-between separation distances.

Analytical study on seismic response of RC and steel structures with fluid viscous dampers

This paper presents a comparative study of the performance of Fluid Viscous Damper (FVD) in mitigating the seismic response of both Reinforced Concrete (RC) and Steel structures. The aim of the study is to understand the behavior of the seismic resistant structures and to study the advantages of FVD over other dampers. The study is done to determine the optimum positioning of FVD in order to reduce the storey displacements and storey drifts. G+3, G+5, G+7 RC and steel structures were modeled in SAP2000 software and were subjected to non linear time history analysis under three different earthquake ground motions such as Imperial Valley – 02 (1940), Loma Prieta (1989) and Northridge-01 (1994). The dampers were placed in four different configurations such as alternate (AT), corner (CR), diagonal (DL) and middle (ML). The seismic response parameters such as the storey displacements and the storey drifts were determined for the structures. It is found that the presence of FVD reduces the storey displacement and storey drift values to about 40-70% from the uncontrolled structure. It is also understood that the optimum positioning of the dampers is greatly influenced by the aspect ratio of the building.

An assessment of damper placement methods considering upfront damper cost

Previous studies have shown that earthquake repair costs can be minimised by using large levels of supplemental damping and uniform damper placement. However, it is not always feasible to achieve this damping due to structural or financial restraints. Iterative damper placement methods may be able to achieve higher levels of damping than simple methods such as uniform damping for the same total damper cost. In this work, six damper placement methods were assessed based on structural and non-structural repair costs. The total damper cost was constrained to be the same in each case. The scope of work was limited to linear fluid viscous dampers, concentric braced frames and regular structures. The iterative methods were found to provide a greater total damping coefficient to the structures than the simple methods. This resulted in a higher supplemental damping ratio and lower repair costs. If upfront funds are limited, or if architectural constraints prevent the placement of dampers in lower storeys, then iterative methods provide the most favourable total-building seismic performance. However, the conclusions should be extended cautiously. Although iterative methods are favourable when the upfront damper investment is strictly limited, in terms of total-building seismic performance, it is advantageous to provide a large damping ratio using uniform damping.

Seismic Analysis of Rcc Structure with Different Types of Dampers

In the present Era escalation of multi-storey high rise building is very common because of rapid urbanization in the entire world also innovation in the field of Engineering, science and Technology. Also Engineers have sophisticated designing software. As height of the building increases building response to the wind and seismic load increases. It means that forces and displacement of the structure is directly proportional to the height of the structure. Many research studiesare going on to reduce the structural instability due to high speed winds and earthquakes. During the earthquake the multi-storey high rise structures are failed to resist the seismic loads and it become the catastrophic disaster for human life’s and for the country. It is most important that structure should be able to withstand against external excitation forces. This can be achieved by building structure more flexible.During the time of earthquake multi-storey structures are swing and large deformation is occurred and vibrations are transferred in the structure through the ground which causes instability in structure. Thus the use of damper is resists lateral forces (wind load, earthquake load) and providing stability to the structure. Dampers are the mechanical devices which dissipate energy which is facilitate in multi-storey structure to reduce the displacement, buckling of beams and columns and increases the structural stiffness. There is lot of various types of dampers are used in RC multi-storey building. This study deals with performance and selection of suitable type of damper which will be more resistant to earthquake for the selected multi-storey building and different seismic parameters like time period, story stiffness, story displacement, story drift and base shear are checked out. In this study seismic behavior of multi-story RCC building with various types of dampers like fluid viscous damper, friction damper and tuned mass damper is carried out.

Seismic Retrofitting Strategies for Soft-Ground-Storied Building

During seismic events, high-rise buildings with soft ground storey are vulnerable to damage as there is a sudden change of stiffness along its height. In this study, different types of energy dissipation devices, which include lower toggle bracing, double-bracing fluid viscous damper, single-bracing fluid viscous damper and single-bracing friction damper, and traditional infill wall are implemented in a 12 storied soft-storey building to assess their influences on reduction of building’s responses during seismic events. These retrofitted buildings are analysed bi-directionally with various ground motion time history of Kolkata region, India. It is seen that energy dissipation devices proved to be better than traditional infill wall due to the fact that the devices enhance the damping capacity as well as stiffness strengthening to the building while traditional infill wall enhances only stiffness strengthening to the building.

Research on Longitudinal Collapse Mode and Control of the Continuous Bridge under Strong Seismic Excitations

Bridge collapse events are common in major earthquakes around the world, among which continuous girder bridges are the most involved. In order to explore the collapse mechanism of a continuous girder bridge in an earthquake, the collapse mode of a two-span continuous girder bridge specimen which had been studied by the shaking table test was analyzed. Then, on the basis of the conventional plate rubber bearing system, the collapse control strategies which were high damping rubber bearing, fluid viscous damper, lock-up clutch control methods were discussed. It is found that high damping rubber bearing can delay the collapse time but the collapse mode remains the same; lock-up clutch has the best displacement control effect for the superstructure, but its energy consumption performance is not as good as that of a fluid viscous damper; high damping rubber bearing is quite suitable for protecting the substructure under short-period ground motion to avoid the bridge collapse caused by the failure of piers; fluid viscous damper and lock-up clutch are suitable for protecting the superstructure under long ground seismic motion to avoid the bridge non-use resulted from girder lowering; three collapse control methods can improve the anti-collapse ability of the bridge specimen, although no matter which control method is used, the bridge specimen may still collapse under strong earthquakes, but the target of postponing collapse time can be realized by means of various effective control methods.

A Novel Iterative Linear Matrix Inequality Design Procedure for Passive Inter-Substructure Vibration Control

In vibration control of compound structures, inter-substructure damper (ISSD) systems exploit the out-of-phase response of different substructures to dissipate the kinetic vibrational energy by means of inter-substructure damping links. For seismic protection of multistory buildings, distributed sets of interstory fluid viscous dampers (FVDs) are ISSD systems of particular interest. The connections between distributed FVD systems and decentralized static output-feedback control allow using advanced controller-design methodologies to obtain passive ISSD systems with high-performance characteristics. A major issue of that approach is the computational difficulties associated to the numerical solution of optimization problems with structured bilinear matrix inequality constraints. In this work, we present a novel iterative linear matrix inequality procedure that can be applied to obtain enhanced suboptimal solutions for that kind of optimization problems. To demonstrate the effectiveness of the proposed methodology, we design a system of supplementary interstory FVDs for the seismic protection of a five-story building by synthesizing a decentralized static velocity-feedback H∞ controller. In the performance assessment, we compare the frequency-domain and time-domain responses of the designed FVD system with the behavior of the optimal static state-feedback H∞ controller. The obtained results indicate that the proposed approach allows designing passive ISSD systems that are capable to match the level of performance attained by optimal state-feedback active controllers.

Damping reduction factors for adjacent buildings connected by fluid-viscous dampers

This work investigates the dynamic behaviour of a multi-storey frame building, assumed as the structure to be controlled, connected with an adjacent support structure by means of horizontal fluid viscous dampers. The dampers connection system has two main effects: (i) energy dissipation provided by the viscous dissipative forces, (ii) energy transfer between modes leading to modes coupling effects between the two buildings without a significant dissipation of energy. The relative contribution of the two effects is highly dependent on the main properties of the coupled system. To investigate this complex behaviour, first the minimal coupled dynamic system composed by two Single-Degree-Of-Freedom systems connected by a viscous damper is analysed. The theory of complex damping is used to determine complex frequencies and damping ratios, while analytical expressions of steady state response under harmonic excitation are determined to investigate the influence of the system parameters on the maximum dynamic amplifications. The seismic response is also investigated through a wide parametric study with the aim of evaluating the trends of the damping reduction factors with respect to the main dynamic parameters of the coupled system. Minimum values of the damping reduction factors and corresponding optimal damping coefficients are determined. Then, the analyses are extended to uniform multi-storey structures for which minimum damping reduction factors are provided for a wide range of the key system parameters. Comparisons between one-storey and uniform multi-storey systems are provided. The results can be useful for a preliminary design of the dampers connection system and for the evaluation of its effectiveness based on the fundamental dynamic properties of the connected buildings.

Risk-informed sensitivity analysis and optimization of seismic mitigation strategy using Gaussian process surrogate model

This work aims to develop a method to derive the optimal parameters of seismic mitigation devices for achieving the minimum system seismic risk, which is derived by accounting for the correlation between each individual components risk. Gaussian process surrogate model (GPSM) is used to illustrate the functional relationship between seismic risk and the variables of the mitigation devices, and then both sensitivity analysis and parameter optimization are carried out. Specifically, global sensitivity analysis (GSA), which is powerful for assessing the relative importance of parameters of the isolation devices, is achieved through the use of GPSM; the parameter optimization can be efficiently conducted to find the minimum seismic risk. A cable-stayed bridge model is established to demonstrate the application of the proposed GPSM-based method of sensitivity analysis and optimization of seismic isolation devices. The fluid viscous damper (FVD) which provides additional damper and stiffness is selected to illustrate the procedure of the multi-object optimization of seismic isolation devices on cable-stayed bridges. The seismic risk is calculated by integrating probabilistic seismic hazard analysis (PSHA), probabilistic seismic demand analysis (PADA), and probabilistic damage states, incorporating important sources of nonlinearity and uncertainties. Component-level objectives and one system-level object are considered, and the optimal parameters (damping coefficient Cd and exponent α) are determined. The results demonstrate that the GPSM-based is effective and efficient for sensitivity analysis and optimization of seismic isolation devices.