Fluid Viscous Dampers Research Articles

Theoretical and Experimental Analysis of a Winding Rope Fluid Viscous Damper

This paper investigated a winding rope fluid viscous damper (WRFVD) that uses the frictional amplification mechanism of a winding rope to obtain the operating characteristics of a viscous damper-like device. The WRFVD combined the advantages of fluid viscous dampers and friction dampers. It not only retained the mechanical characteristics of the fluid viscous damper but also reduced manufacturing costs. First, the construction and working principles of the WRFVD were introduced. A theoretical model that could accurately simulate the hysteretic characteristics of the damper was derived. Then, a series of dynamic tests were performed on six prototypes of the WRFVD. The dynamic performance under different displacement amplitudes and device parameters was analyzed based on the test results. In addition, the theoretical model was validated by experimental results. Finally, a series of parametric analyses of the WRFVD were performed. The experimental results showed that the WRFVD is a type of velocity-dependent damper with smooth and plump hysteretic curves under sinusoidal displacement excitation. Fatigue loading tests showed that the WRFVD had excellent fatigue resistance capacity and stable operational performance. The established theoretical model was reasonable and satisfactorily reproduced the hysteretic properties of the WRFVD. The parametric analyses showed that it was not recommended to improve the performance of the WRFVD by the method of adjusting the damping coefficient and pretightening load. It was reasonable to adjust the performance of the WRFVD by setting a smaller velocity exponent, an appropriate winding turn of winding ropes, and a suitable friction coefficient.

Comparative study of buckling restrained braces and fluid viscous damper applied in an RCC structure following pushover analysis

Energy dissipators are widely used to enhance structural performance against wind and seismic activities. Since India is an earthquake-prone country, displacement-dependent (an example: buckling restrained bracing), and velocity-dependent (an example: fluid viscous damper) both types of energy dissipators are becoming more well-known and widely used to lessen the effects of seismic occurrences. Although most of the study about the application and performance evaluation of energy dissipators like buckling restrained braces (BRB) and fluid viscous damper (FVD) were based on steel and composite structure, reinforced cement concrete (RCC) building makes up the majority of structures in India, and a large number of RCC building structure are not capable to resist damage due to seismic activity. Additionally, nonlinear static analysis-based comparative information concerning BRB and FVD is very few. This study focused on a comparison of two energy dissipators- a) buckling restrained bracing (BRB) and b) fluid viscous damper (FVD) used in an RCC structure following pushover analysis to produce a pushover curve and evaluate structural performance. Four Ground floor + 14 (G + 14) storey RCC structures were created according to Indian Standard (IS) provisions in Extended Three-Dimensional Analysis of Building System (ETABS) software and applied BRB and FVD separately in diagonal and inverted V shapes. To compare structural responses with BRB and FVD independently, the results of the diagonal and inverted V systems have been explored. All the data were acquired by utilizing response spectrum sources developed under IS 1893:2016 following ASCE 41–13 NSP graphical display for static pushover curve in ETABS. It has been determined that the sample BRB has performed more admirably than FVD in both circumstances while using a diagonal and inverted V bracing system. But in large displacement FVD tends to increase performance. BRB is stiffer than FVD, allowing it to be used to raise the structure's stiffness as needed. It is essential to consider the seismic weight of BRB and FVD while designing a new building or retrofitting and restoring a structure.

Development of integrated semi-active adaptive vibration control system for bridges subjected to traffic loads

Nowadays, the fluid viscous damper is the most conventional energy dissipation system implemented in bridge structures to control the vibrations due to traffic loads. However, to effectively protect the bridge against frequent and severer vibrations, it is required to adapt the function of the damper according to the variable traffic loads. In this research, an Integrated Semi-Active Adaptive Vibration Control System is developed for the bridge structures. This control system consists of a Semi-Active Bypass Fluid Damper (SABFD), a programmable logic controller (PLC), pressure transducers, and displacement sensors. Semi-Active Bypass Fluid Damper is a hydraulic cylinder with a pair of external bypass pipes with motorized electric flow control valves which are installed in the middle of pipes to control the flow rate of the fluid. A programmable logic controller (PLC) is implemented to manage the operation of motorized valves according to the movement of the bridge.Therefore, the integrated control system is able to function as a real-time controller during its operation. To develop the control system, the performance of the SABFD device has been assessed through analytical model of the various control valve positions. Then, according to the structure response, a fuzzy control algorithm has been adapted in the PLC controller.Afterward, the prototypes of the SABFD and the PLC controller have been fabricated and a series of cyclic load tests have been conducted by using a dynamic actuator. The outcomes of the numerical analysis and results of the experimental tests revealed that the developed device is capable of generating a wide range of forces during device operation. The developed fuzzy control algorithm is then implemented to the finite element model of the bridge equipped with SABFD, and the results proved that the real-time control system effectively limits the bridge displacements according to the pre-defined fuzzy control rules.

Short-horizon acceleration-predictive control for reducing lateral seismic inertia forces of inelastic frame structures using semi-active fluid viscous dampers

Semi-active control systems effectively improve the resilience of civil structures when subject to dynamic vibrations due to their ability to change their damping properties. In the case of semi-active fluid viscous dampers (SAFVD), the damping coefficient quantity varies according to the tradeoff between the need to increase the energy dissipation capabilities (i.e., increasing the damping coefficient) and the need to decrease the applied shear forces (i.e., reducing the damping coefficient). The operation of a SAFVD device is similar to that of a passive fluid viscous damper except that, based on the status of the control valve, it can deliver damping at two distinct levels (two-stage) or over a wide range between an upper and lower bound (continuously adjustable). This paper employs a continuously adjustable SAFVD assembly and develops its optimal command voltage change at each time step, which regulates the valve that determines the fluid passing through the external path. The control strategy uses total acceleration measurement as the system's closed-loop feedback and utilizes the Kalman filter model to predict the sequential acceleration reading to cater to time delays. The solution derives from a short‐horizon problem whose objective is reducing the difference between the lateral seismic inertia forces and the SAFVD forces, thus, mitigating the columns’ resisting forces. The case study presented in this paper showcases the effectiveness of the SAFVDs in improving the inelastic earthquake response of a 10-story frame structure.

Plastic energy evaluation of bilinear SDOF systems with fluid viscous dampers

SummaryCurrent seismic practices are more concerned with dissipating a significant portion of seismic input energy than with lateral load resistance, as well as with determining seismic demands of structures using response spectra. This study aims to improve the knowledge of the plastic energy spectra ( ) of single‐degree‐of‐freedom systems (SDOF) equipped with fluid viscous dampers (FVDs). This type of dampers is characterized by its supplemental damping ratio and velocity power . Using nonlinear dynamic analyses, the and its ratio to the input energy ( ) are determined using near‐field‐pulse, near‐field‐non‐pulse and far‐field ground motions. Parametric studies are conducted to investigate the effect of ground motion types, original system features and FVD characteristics on spectra. The results show that ground motion types have a considerable influence on the for systems with FVDs, while they are not effective for systems without FVDs. Increasing FVD nonlinearity (decreasing α) is more effective to reduce the under near‐field‐non‐pulse and far‐field motions than under near‐field‐pulse ground motions for structures with > 1 s. The paper further developed a prediction equation for estimating for SDOF systems without and with FVDs, which can serve as a useful tool to analyse structural damage for energy‐based seismic design.

Effects of Building Height and Seismic Load on the Optimal Performance of Base Isolation System

AbstractSeismic isolation has been widely accepted as one of the techniques that can be used to protect structures during earthquake ground motions. However, some challenges still exist such as the optimal control of excessive isolator shear strains imposed by some ground motions. The main purpose of this study was to assess the effects of building height variation and earthquake ground motion type on the optimal performance of the seismic isolation using lead core rubber bearing (LCRB). Nonlinear time history analysis for building models of various storeys isolated by LCRB and exposed to different real earthquakes was performed. To achieve this, the equations governing the motion of the isolated three different building models were presented, and an approach for solving the equations while taking into consideration of the optimized mechanical properties of the LCRB was developed. The LCRB performance was measured in terms of elastomer shear strains, derived after an optimal criterion leading to reliable substructure and superstructure responses was reached. The results showed that the combined effects of the earthquake type and building height significantly affect the substructure responses (maximum isolator displacement, energy dissipation capacity, maximum isolator force) and the superstructure responses (storey shear forces, storey drifts, floor displacements, and floor accelerations), which in some cases lead to a need for adding a fluid damper. In this regard, an attempt to couple the LCRB with nonlinear fluid viscous damper was made, and the performance of the hybrid was assessed. It was generally found that the hybrid can positively improve the substructure responses, thereby reducing the unwanted large elastomer shear strains without adversely affecting the superstructure responses.

Anti-seismic Technology in Suspension Bridge Designs: A Review

Suspension bridges are vital transportation infrastructures that support high traffic levels. It is of great importance for suspension bridges to remain operational following hazardous earthquake motions. Seismic devices preserve crucial bridge elements and aid in the control of ground motion response through energy dissipation and damping. This literature review introduces and evaluates the performance of widely-applied anti-seismic technologies such as tuned mass dampers, fluid viscous dampers, and seismic isolators in suspension bridge designs. The paper condenses and compares the results of analytical literature surrounding the effectiveness of seismic devices. Conclusions from current research indicate that the implementation of fluid viscous dampers is optimal for deck displacement damping in suspension bridges. Less effectiveness is found for seismic isolators and almost negligible success is found for tuned mass dampers under high seismic motions. The generalization of the results and the potential performance discrepancies due to spatial variability are noted.

Damage indices of steel moment-resisting frames equipped with fluid viscous dampers

ABSTRACT Deformations, accelerations, shear forces, and energy demands are normally utilized to evaluate the performance of steel frames equipped with fluid viscous dampers (FVDs). This study aims to quantify damage indices (DI) and their distributions along the structural height for steel frames (3, 6, 9, and 20 stories) equipped with FVDs. The damage model incorporating both deformation and hysteretic plastic energy is adopted to quantify damage developed in structures. A set of 20 pairs of ground motions is used to perform nonlinear time history analyses. Influences of structural property and FVD features (supplementary damping ratio and velocity power ) on DI are investigated. The results show that FVDs with lower α would reduce DI. However, nonlinear FVDs lead to higher DI compared to linear ones when >30%, particularly for 9- and 20-story structures. Nonlinear FVDs () are more effective than linear ones in reducing DI during low-intensity earthquakes. The results further demonstrate that the distribution of DI along the structural height is mostly determined by structural properties, FVD characteristics, ground motion intensity, and the type of damage model used.

Risk-based optimization of seismic mitigation devices constrained by user-defined components importance

The system optimization of complex structures is to achieve the overall best behaviour, however, specifications and engineers often pay more attention to the seismic performance of critical components. To comprehensively consider the requirement from theoretical research and practical engineering, a constrained optimization method of seismic mitigation devices for complex structures is proposed in this study, considering the user-defined importance of critical components. The seismic damage probability of individual components is defined as constrained functions (CFs). The overall probabilistic seismic performance of the bridge system is formulated as the objective function (OF) to carry out optimization analysis within the admissible region obtained by CFs. The surrogate functions between the variables and OF/CFs are formulated by the proposed Hazard-related Response Surface Method (H-RSM). A three-dimensional long cable-stayed bridge with a mitigation device of the fluid viscous damper (FVD) is constructed as the case-study model via FEM. Three constrained conditions are imposed by restricting the CFs less than a user-defined threshold to satisfy different safety requirements of the pylon, bearing and FVD. Different protection levels of the pylon are investigated to compare the constrained and unconstrained optimization methods. The influence of the maximum displacement of FVD on the optimal variables is also investigated.

Optimum parameters for adjacent frames coupled by fluid viscous dampers considering soil-structure interaction

In this paper, the optimum conditions which ensure that the resulting minimum base shear force and minimum roof displacement for two adjacent frame structures interconnected by fluid viscous dampers, including soil-structure interaction (SSI) effects under seismic excitation were presented. A two-dimensional (2D) finite element analysis was carried out with the Taguchi method. As non-reflecting boundaries, viscous boundary conditions were used on the edges of finite soil region. An optimization study was carried out for four parameters such as soil type, height ratio of the frames, damping coefficient of viscous damper, and the location of the viscous damper each with four levels. The optimum conditions which minimize maximum roof displacements and the maximum base shear forces have been obtained. The most affecting parameter on the system response was found to be soil type. It was also found that the sufficient damping coefficient of the viscous damper is equal to 1x105 N.s/m for minimum response. The minimum system response can be achieved by using only one damper. It can be drawn that the Taguchi method can be used with the finite element (FE) method for determining optimum conditions of a soil-structure system for minimum system response.

Stochastic Optimization of Dissipation Structures Based on Lyapunov Differential Equations and the Full Stress Design Method

This article presents a Lyapunov precise integral-based analysis method for seismic structures with added viscous fluid dampers. This study uses the full stress algorithm as the optimization method, considering the mean square of interstory drifts as the optimization objective, the position of the damper as the optimization object, and the random vibration analysis method as the calculation method to optimize seismic frame structures with viscous dampers. A precise integral solution is derived for the Lyapunov equation based on the general expression of the Lyapunov differential equation for the damping system under the excitation of a nonstationary stochastic process using two types of modulation functions: g(t)=1 and g(t)=t. Finally, the optimal damping arrangement is achieved using this method with a six-layer non-eccentric planar frame. In addition, the optimization results of this study are verified with those in the literature using time-history analysis, which verifies the feasibility and effectiveness of the proposed method. This study provides a method for the optimal configuration of dampers for seismic response of structures, which is beneficial for engineering applications and the protection of seismic structures.

Seismic performance improvement of continuous rigid-frame bridges with hybrid control system under near-fault ground motions

To improve the seismic performance of continuous rigid-frame bridges (CRFBs) in near-fault earthquakes, this study developed a hybrid seismic control system (HSCS) combining a three-dimensional hybrid seismic isolation bearing (3D-HSIB) with a longitudinal fluid viscous damper (L-FVD). The hybrid numerical model of the HSCS and the nonlinear numerical model of a CRFB prototype were simulated in OpenSees. The study comparatively analyzed the seismic responses of non-controlled bridges and HSCS-controlled bridges under near-fault ground motions, evaluated the seismic control effectiveness of the HSCS, and investigated the effects of vertical excitations on the seismic performance of the CRFB. The numerical results show that the proposed HSCS effectively reduces the three-directional seismic responses of the CRFB. When the PGA is 0.4 g, the seismic isolation ratios of displacement, internal force, and pounding force all exceed 0.4. The hysteresis behavior of the HSCS can be fully utilized under three-directional excitations with pulse-like effects. The girder-end uplift behavior under vertical excitation can be effectively controlled by the proposed 3D-HSIB with a seismic isolation ratio of at least 0.6. When vertical excitation exceeds a certain level, the bearing is tensioned upward while axial tension force may also occur in main piers. Furthermore, the seismic responses under pulse-like near-fault ground motions are significantly larger than those under non-pulse near-fault ground motions. This work may provide a useful reference for the seismic analysis and design of CRFBs.

A three-dimensional refined numerical simulation of cross-flow induced vibration mechanism in the tube bundle

Cross-flow induced vibration causes many accidents in the nuclear steam generator tube bundle. An accurate and refined cross-flow induced vibration numerical simulation can help avoid accidents in the designed bundle for different geometries, and provide insights into flow-induced vibration mechanism. In this paper, a three-dimensional refined numerical simulation model considering the fluid viscous damping was established and validated. First, we validated the simulation of the viscous damping that structure suffered in the fluid, and studied the relationship between the fluid viscous damping and the structural spring damping in tube bundle coupling with fluid. The results showed that fluid viscous damping coefficient and the structural spring damping coefficient can be directly added to equal the total damping coefficient in the coupling system between the tube bundle and fluid. Then, a three-dimensional simulation based on SST-SAS (the Transition SST combined with the Scale Adaptive Simulations (SAS) turbulence model) was used to study flow-induced vibration for the literature experiment tube bundle. Simulation of flow-induced vibration had the same mass-damping parameters with the literature experiment. The vibration amplitude trend and spectra of the simulation were basically consistent with that of the experiment. Simulation accurately captured the onset of the vortex-induced resonance and the transition from the vortex-induced resonance to the fluidelastic instability. And the different mechanisms and their transition were analyzed. Specially, the flow field and structure analysis showed that the local vortex-induced resonance of the front-row tubes caused the synchronous resonance of the whole tube bundle.

An uncoupled damping system for tension-only braced structures: experimental and numerical analysis

The stiffness and damping force are coupled in traditional damping devices for tension-only braced structures resulting in insufficient damping ability. A new asymmetrical viscous damper (AVD) is proposed which carries asymmetrical forces when it is tensed or compressed matching up with the tension-only brace (TOB). An uncoupled damping system of AVD setting in parallel with TOB, namely TOB-AVD is developed accordingly. The TOB-AVD can protect the tension-only braced structures from degraded slackness or straightened impulses under earthquake excitation. In this paper, an asymmetrical dashpot (AD) constitutive model is firstly proposed and implemented to the OpenSees platform. Secondly, based on combined type fluid viscous damper, two AVD samples representing the baseline and the improved one are designed, manufactured and tested. Finally, non-linear time history analysis is conducted on finite element models of a tension-only braced benchmark building with and without AVDs. The results indicate that while adopting TOB-AVD, the inter-story drift ratio, peak floor acceleration and floor acceleration amplification are reduced by 60.7%, 49.0% and 49.0% in average, eliminating the degradation phenomenon happening in TOBs and protecting both structural and non-structural components in tension-only braced structures.

Experimental study on the dynamic performance of a winding rope fluid viscous damper

This study proposed a winding rope fluid viscous damper (WRFVD) using the winding ropes to amplify the damping force of a fluid viscous damper. To investigate the dynamic performance of the WRFVD, four different prototypes were fabricated and tested under a series of sinusoidal loading protocols. Experimental results demonstrated that the WRFVD is a velocity-dependent damping device with significant and stable energy dissipation capacity. The winding rope amplification mechanism can effectively amplify the damping force of the fluid viscous damper by 3 to 6 times, and amplify the energy dissipation of the fluid viscous damper by 3.5 to 6.9 times. After 30 cycles of fatigue loading, the maximum damping force and the energy dissipation capacity of the WRFVD almost not decayed. The damping force of the WRFVD had a linear relationship with the damping force of fluid viscous damper with the coefficient of β, and β was only related to the construction of the WRFVD itself. The theoretical model of damping force based on the Maxwell-β nonlinear model could reflect the mechanical properties of the WRFVD well, and the theoretical and experimental hysteresis curves are in good agreement.

Numerical and experimental investigations on the seismic response of continuous girder bridge using winding rope fluid viscous dampers

Severe damage to the continuous girder bridges (CGB) has been observed in past earthquakes. To decrease the seismic response of CGB, a novel winding rope fluid viscous damper (WRFVD) is proposed. In this paper, theoretical mechanical equations for the WRFVD are derived. In addition, simplified numerical modeling approach on CGB with WRFVD is presented. To verify effectiveness of the WRFVD on CGB, a scaled three-span CGB equipped with WRFVD was tested using the shaking table test. The results showed that WRFVD can effectively reduce the internal force of the fixed pier and the deck displacement. In addition, the experimental results verified that the simplified numerical model can be used effectively to simulate the seismic response of multi-span CGB equipped with WRFVD. The verified numerical model was used in a parameter study to examine the influence of damping coefficient, damping index, number and rope pre-tension of WRFVD on the seismic response of a five-span CGB. The parameter study shows that the seismic response of multi-span CGB equipped with WRFVD decreases with the increasing damping coefficient, the increasing number of WRFVD and the decreasing damping index. The influence of the pre-tension of winding ropes is more efficient for the near-fault ground motions. The results demonstrate WRFVD can be used effectively to reduce the seismic response of CGB.

Seismic assessment and dissipative bracing retrofit-based protection of infills and partitions in RC structures

A balanced performance improvement of the constituting structural members, infills and partitions is a fundamental requirement in seismic retrofit design of frame buildings. In order to pursue this objective, the response of the non-structural elements must be accurately simulated, so as to evaluate their damage evolution and the correlation with the response of the structural skeleton. In the study presented in this article, diagonal no-tension struts with multilinear “pivot”-type hysteretic behaviour are adopted as substitute elements for masonry infill and partition panels. A trilinear axial force–displacement backbone curve is generated for the equivalent struts and transformed in the lateral force-drift curve of the panels. The latter is then scanned in terms of sequential performance limits and ranges. This model is demonstratively applied to a real case study, i.e. a reinforced concrete frame building damaged by the 2016 Central Italy earthquake, although a retrofit intervention had been carried out a few years before. Based on the results of the time-history assessment analyses in its original conditions, an alternative retrofit solution is proposed, consisting in the incorporation of dissipative braces equipped with pressurized fluid viscous dampers. This technology was selected for its high-damping capacity, as well as for the prompt activation of the constituting devices starting from the early stages of the building seismic response. The verification analyses developed in retrofitted configuration for the main shock records of the 2016 earthquake confirm this property, showing slight damage only in a small number of partitions—instead of the diffused moderate-to-irreparable damage actually surveyed in the building partitions and infills—and safe response of all structural members.

Shock Vibration Control of SDOF Systems with Tubular Linear Eddy Current Dampers

The nonlinear dynamic characteristic of a tubular linear eddy current damper (TLECD) and the transient responses to shock excitations of a single-degree-of-freedom (SDOF) system with the TLECD are studied. First, the nonlinear force-velocity relationship of the TLECD is discussed using the finite element simulation and mathematical model fitting. Next, the influences of three forms of shock excitation and various mechanical parameters of the TLECD on shock vibration control of an SDOF system with the TLECD are investigated. Moreover, for the SDOF systems with the TLECD or the nonlinear fluid viscous dampers (FVD) at the same maximum displacement and maximum damper force, the time to reach the maximum displacement, the time to reach one-third of the maximum displacement, the energy input of the external loading, and the energy dissipation of dampers are analyzed and compared. Finally, the shock response spectrums (SRSs) of the SDOF system and the design flowchart for the TLECD are presented to provide a reference for shock vibration control of the SDOF system with the nonlinear TLECD and the design of TLECDs. The results show that there is an optimal dimensionless critical relative velocity that minimizes the dimensionless maximum damping force for reaching the target maximum displacement, and compared to the FVD, the TLECD greatly shortens the time to reach one-third of the maximum displacement.

Optimal Seismic Design of Controlled Coupled Multiple Rocking Systems with Viscous Dampers in Irregular Buildings

The reduced damage and residual deformations of rocking systems make them efficient for designing resilient buildings for earthquakes. This paper presents a design approach for multiple-rocking coupled self-centering concentrically braced frames (SC-CBFs) with linear fluid viscous dampers (FVDs) utilizing an efficient gradient-based optimization procedure. The optimization problem is formulated such that the framing system, the post-tensioning layout, and the location of the rocking sections are simultaneously designed with the FVDs. The constraints of the optimization problem are formulated following performance-based seismic design. These constraints are evaluated based on results obtained from nonlinear time history analyses of the system when subjected to an ensemble of ground motion records. For the first time, a design method suitable for irregular buildings with multiple-rocking coupled SC-CBFs is proposed. A nine-story irregular building was designed using the proposed method. The results show that an efficient design can be achieved with reasonable computational effort. In addition, the results show that the design of these buildings is not intuitive. A multiple-rocking solution was obtained to reduce force demands in the framing elements.

Damping evaluation of an eight-story steel building with nonlinear oil damper under strong earthquakes

Fluid viscous damper has been applied widely for energy dissipation and shock absorption in dynamic structural systems, specifically the oil damper. Nevertheless, there's an issue of precisely incorporating shaft bearings and pressure sealings for oil dampers, which restricts its wide application in new or existing structures. A type of nonlinear oil damper with viscoelastic polymer packing soft links is posed and investigated to allow for easy production. To explore the effectivity and actual performance of the nonlinear oil dampers, vibration monitoring system has been instrumented both on the dampers and the building since it was built in 2003, which accumulated huge amount of precious data. A Bayesian based order selection of auto-regressive exogenous model is exploited to the recorded earthquake responses to extract dynamic properties of the passively-controlled 8-story steel building. Thus, damping characteristics of the whole structure can be identified and analyzed. Besides, an analytical model for the nonlinear oil damper is investigated and estimated by particle filter improved with Metropolis-Hastings algorithm, which can be incorporated into the whole structure model for model updating, reliability as well as response prediction. Furthermore, the calculation formulas of the additional effective damping ratio provided by oil damper are deduced based on above analysis using modal strain energy, and damping ratio of the main steel frame structure are also estimated. Taking a set of actual ground motion monitoring data as an example, the proposed method is then exploited to estimate the effective damping ratio of oil damper for each floor.