Viscous Damping Research Articles

Negative stiffness device for seismic protection of MDOF yielding fixed base structures: Experimental and analytical study

Shake table tests of single degree of freedom elastic/inelastic structures have confirmed that by adding a negative stiffness device (NSD), capable of exhibiting nonlinear elastic negative stiffness, in conjunction with a viscous damper, the acceleration, inter-story drifts, and base shear can be reduced significantly. However, little is known about how the presence of NSD/damper in the first story influences the response of higher stories of a multistory structure. In this paper, shake table test results are presented that demonstrate the advantages of NSD/damper in the first story of a multidegree of freedom, three-story, fixed-base structure (MDOF-3SFS). Results confirm that deployment of NSD/damper at the first story leads to significant reductions of acceleration as well as base shear and inter-story deformations in the MDOF-3SFS. Essentially, an NSD and a damper in the first floor prevents the transmission of the input energy from the ground motion to the second and third story of the multistory structure by deflecting and dissipating energy. If the first-story displacements become excessive, NSD stiffens and prevents collapse. The efficacy of the NSD/damper system is further demonstrated by comparing it with the performance of a structure with passive viscous dampers deployed in the first story. In addition to the reduction of base shear and maximum accelerations, the NSD/damper system also restricts large deformations to the first story only, leading to minimal damage to the whole structure. Finally, an NSD-based bracing system is introduced that can be deployed in new and existing structures.

Behavior of laminated bamboo columns under low cyclic reversed loading

Laminated bamboo, a type of eco-friendly engineered bamboo product, is increasingly gaining attention in the field of civil engineering. Although there has been considerable research on the material properties of laminated bamboo, studies focusing on the seismic performance of laminated bamboo columns are still relatively scarce. This paper discusses in detail the behavior of laminated bamboo columns and BFRP (Basalt fiber reinforced polymer) reinforced laminated bamboo columns under low cyclic reversed loading. In particular, the effects of slenderness ratio and axial compression ratio on laminated bamboo columns and BFRP reinforced laminated bamboo columns are studied. The hysteresis behavior of the column specimens is first tested through experiments. The results show that under low cyclic reverse loading, the failure of laminated bamboo columns is due to the tensile fracture and compressive bending of bamboo strips, as well as the tensile fracture of BFRP. To quantify the mechanical performance of laminated bamboo columns, parameters of interest are defined and discussed, including load-bearing capacity, stiffness, energy dissipation, and equivalent viscous damping. The load-bearing capacity and stiffness of laminated bamboo columns and BFRP reinforced laminated bamboo columns are significantly affected by the slenderness ratio and axial compression ratio. The yield loads for the column specimens with slenderness ratios of 37.0, 63.4, and 77.5 are within the ranges of 2.08–7.64 kN, 1.63–5.15 kN, and 1.82–7.51 kN, respectively. Laminated bamboo columns exhibit a satisfactory energy dissipation, with the maximum observed equivalent viscous damping exceeding 50 %. Furthermore, combining theoretical calculations and fitting analysis, bilinear skeleton curve models for both laminated bamboo columns and BFRP reinforced laminated bamboo columns are presented, showing a good agreement with experimental results. This research aims to provide some references for the design of laminated bamboo structures in future practical engineering.

Measurement of Steam-Generator-Tube Vibration Damping Caused by Anti-Vibration-Bar Supports

Abstract In 2013, Atomic Energy of Canada Limited (now Canadian Nuclear Laboratories) experimentally measured the damping of a straight tube with a variety of tube supports to examine low-frequency damping. These tests were motivated by the discovery of severe tube damage caused by in-plane fluidelastic instability (FEI) in the U-bend regions of new replacement recirculating steam generators (SG). The measurements were intended to assess the applicability of existing design guidelines for estimating the support-related damping of a tube. In the tests, the damping ratios of a single steam generator tube were measured using both log-decrement and power-based methods. Noncontacting excitation and position-sensing techniques were employed to improve accuracy. Initial baseline tests explored configurations with no support and drilled-hole supports of different hole sizes, and these results were compared with previously published work. Subsequent tests were performed to measure damping of tube vibration parallel to flat-bar supports. Most of the tests were performed with the tube fully submerged in still water. The tests examined the effects of fluid (water or air), natural frequency, gap width, preload, and vibration normal to the bars. This paper describes the test apparatus, methods, and analysis techniques. A summary of the results is presented. The initial baseline results showed that the damping ratios measured without any supports and with a drilled-hole support were consistent with previously published data. However, the subsequent measurements showed that, contrary to a published design guideline, the anti-vibration bars resulted in no significant additional viscous or squeeze-film damping when the vibration was parallel to the bars. On the other hand, the results did show that anti-vibration bars could introduce significant in-plane Coulomb-type damping if there was sufficient tube-to-support preload or impacting.

Exact Solution of Nonlinear TVMD Based on Maximizing Damping Enhancement Effect for Acceleration Response Control

The tuned viscous mass damper (TVMD) exhibits superior control effect and energy dissipation capability compared to the viscous damper (VD). Existing literature has primarily focused on the control of absolute acceleration response in structures by linear TVMD, with limited research on nonlinear damper for controlling structural performance and efficiency. This study proposes a methodology for determining the optimal parameters of linear TVMD. The closed-form solution of the nonlinear TVMD is derived through stochastic linearization based on the linear TVMD, aiming to minimize the damping ratio of TVMD by utilizing the damping enhancement effect of the system. For lightly damped structures, the closed-form solution remains a reliable method for accurately approximating TVMD design parameters. Compared to traditional fixed-point theory, the TVMD developed through the proposed methodology demonstrates superior control performance, especially in terms of absolute acceleration, with a smaller damping ratio and minimal deviation from the optimal state of the TVMD. Additionally, the study investigated the influence of the damping index on the optimal parameters and the efficacy of the TVMD in vibration control. It is observed that reducing the damping index can improve structural performance, particularly in long-period structures with small mass ratios, although it may reduce the efficiency of the TVMD. Notably, TVMDs with lower mass ratios maintain higher efficiency regardless of the structural natural period. The damping index does not affect the optimal frequency ratio or the mean square response. Ultimately, the effectiveness of the optimization method is displayed through the examination of response spectra following 22 real seismic events, showcasing its adaptability across various structural types. The comparison of the root-mean-square response between the VD and TVMD across different periods shows consistent results, with a maximum deviation of only 10%. The TVMD is highly effective at regulating the structural response, excelling particularly in controlling the absolute acceleration of long-period structures, where it reduces maximum absolute acceleration by 20% more than displacement. The proposed exact solution rapidly and precisely identifies the design parameters of nonlinear TVMD by the desired specifications, thereby offering theoretical guidance for practical engineering applications.

Analyzing the chaotic and stability behavior of a duffing oscillator excited by a sinusoidal external force

This paper delves into the dynamical, chaotic, and stability aspects of the Duffing oscillator (DO) under sinusoidal external excitation, underscoring its relevance in various scientific and engineering applications. The DO, with its complex behavior, poses a significant challenge to our understanding. A unique perturbation technique, the multiple-scales (MS), is harnessed to tackle this challenge and enrich our knowledge. The analysis entails determining third-order expansions, exploring resonant cases, and factoring in the influence of viscous damping. The accuracy of the analytical solution is cross-validated with numerical results using the Runge–Kutta fourth-order (RK4). The paper also employs effective methods to assess the obtained results qualitatively. As a result, Visual figures, such as bifurcation diagrams and Lyapunov exponents’ spectra (LES), have been presented to illustrate diverse system motions and demonstrate Poincaré diagrams. Moreover, stability analysis has been investigated via resonance curves showing the stable and unstable regions. These aids facilitate our comprehension of the system’s complex behavior and its variations under different conditions. The results are elucidated through displayed curves, offering insights into the dynamics of the DO under sinusoidal excitation and damping effects. The influence of excitation and the quadratic parameter on bifurcation diagrams, LES, and Poincaré maps helps us understand the intricate behavior of nonlinear oscillatory systems, such as DO. The presented oscillator is a compelling example of elucidating the nonlinear behavior observed in numerous engineering and physics phenomena.

Optimization and evaluation of tuned inerter-based dampers for mitigating coupled responses of offshore wind turbines

To achieve lightweight vibration control in offshore wind turbines (OWTs), this study proposes the utilization of two types of tuned inerter-based dampers (TIBDs), namely, the tuned viscous mass damper (TVMD) and tuned inerter damper (TID), to mitigate the coupled responses of an OWT induced by wind and wave loads. First, a multi-degree-of-freedom (MDOF) lumped mass model is established to represent an OWT equipped with a TIBD. Then, a novel structural control module for TIBDs is developed and seamlessly integrated into the modular numerical analysis code OpenFAST. This enables fully coupled aero-hydro-servo-elastic simulations of the OWT-TIBD system. Using the established MDOF model, a TIBD parameter optimization design method is proposed to minimize the peak of the non-dimensional displacement frequency response function. Additionally, a parametric study is performed to investigate the effect of inertance and span height on the control performance. Finally, the performance of the TIBD in attenuating both fatigue and extreme loads is evaluated through nonlinear fully coupled time-domain simulations using OpenFAST and compared to traditional tuned mass dampers (TMDs). The results showed that a lightweight and small damper displacement TIBD is capable of effectively dampening OWT vibrations, yielding a better mitigation effect than that provided by a bulky TMD. Overall, the reduced installation requirements and the commendable control efficiency of a TIBD highlight its potential as a promising candidate for passive control devices in OWT applications.

Investigation of an Impact-buffered Viscous Damper: a New Mechanical Model, Experiments, and Numerical Simulations

Investigation of an Impact-buffered Viscous Damper: a New Mechanical Model, Experiments, and Numerical Simulations

Theoretical and numerical study of the thermo-mechanical coupling effect on the fluid viscous damper

Theoretical and numerical study of the thermo-mechanical coupling effect on the fluid viscous damper

Review Paper on Seismic Analysis of Multi-Storied Reinforced Concrete Building with Fluid Viscous Dampers

Abstract: Frequent earthquakes around the world and the large number of buildings at risk have made it essential to focus on controlling how structures respond to these events. This demand has driven the increased use of structural response control methods globally. This study investigates the seismic performance of multi-storied Reinforced Concrete (RC) Buildings, distinguishing between Regular and Irregular Plan , with a focus on the role of Fluid Viscous Dampers (FVDs). The study aims to quantify the improvements in seismic resilience provided by these damping devices in mitigating the adverse effects of seismic events. Buildings having Regular and Irregular Plans are analyzed, with and without FVD using ETABS2018. The story responses in terms of Pseudo Spectral Accelerations, Maximum Displacement, Story Drift and Story Shear have been compared. The results of the Time History Analysis represent the effectiveness of dampers in improving the structural response and the damping demand on structural systems

Study on seismic response of flexure-shear critical RC columns wrapped with TRC shells

Quasi-static tests were conducted on sixteen specimens to study the seismic response of flexure-shear columns wrapped with textile reinforced concrete (TRC) shells. Two RC square columns served as controls, while the remaining columns were wrapped with TRC shells. Three types of treatment methods were applied to TRC-wrapped columns herein to study the impact of different interfacial treatments on seismic behaviours. This study also analyzed the impacts of shear span ratios, axial load ratios, and number of textile layers on the seismic response of test columns. Results revealed that the TRC confinement layers could mitigate crack development, transforming RC columns' failure modes from flexure-shear to flexure. Due to greater confinement to the concrete core, TRC-wrapped columns exhibited enhanced performances compared to control columns, with peak loads, ductility, and cumulative energy dissipation increasing by up to 49.9%, 195.3%, and 5.7 times, respectively. TRC confinement layers could mitigate the shear effects in column specimens. TRC wrapping could improve the shear capacities of flexure-shear columns, with growth rates ranging from 25.2% to 60.4%. Eventually, an equivalent viscous damping model was proposed to assess the energy dissipation capacity of flexure-shear columns wrapped with TRC shells.

Performance Evaluation of Inerter and Negative Stiffness-Based Dampers for Seismic-Induced Vibration Response Control of a Cable-Stayed Bridge: A Comparative Study

The excessive main girder displacement responses of the large-span cable-stayed bridges during seismic events may precipitate collisions between the main girder and the approach bridge. The viscous dampers (VDs) have been extensively employed in the seismic response control of long-span bridges, yet their effectiveness is limited. To augment the seismic-induced vibration control performance of the VD, inerter element, negative stiffness (NS) element, and spring element have been incorporated into the VD to achieve energy dissipation capacity enhancement. The equations of motion for the simplified cable-stayed bridge-damper systems are established under stochastic seismic excitation, and the design parameters of inerter and NS-based damper are optimized by using the genetic algorithm. The seismic control performance of the VD and five types of dampers are systematically compared, demonstrating that these dampers can substantially enhance the main girder displacement mitigation performance in cable-stayed bridges. Owing to the NS characteristics attributes of the inerter element and NS element and the tuning effect of the spring element, the tuned viscous mass damper (TVMD) with NS achieves a 24.56% higher efficiency in control performance compared to the VD.

Understanding the Inherently Self-Adjusting Mechanism and Load Adaptability of the Mem-Damper

The tapered dashpot (damper) has been the earliest memristor found in the mechanical engineering domain, named mem-dashpot (mem-damper), since the missing memristor was postulated by Leon Chua. In this paper, a displacement-dependent viscous damper device with internal channels is investigated and recognized as a physical realization of the mem-damper by analyzing the mathematical and dynamic relationships of the device’s complementary port variables theoretically and experimentally. A vehicle suspension equipped with a mem-damper is taken as a carrier for presenting load adaptability of the mem-damper. An investigation reveals the inherently self-adjusting mechanism behind load adaptability from the viewpoint of energy storage, that is, a mem-damper with different initial displacement values can be equivalent to a semi-active damper performing an initial-position-dependent damping control strategy. Finally, the load adaptability of the mem-damper is demonstrated through both simulation and experiment of the suspension system with the mem-damper prototype. Due to such load adaptability, the suspension equipped with the mem-damper can offer more constant and smoother ride comfort than the one with the linear damper.

Investigating the behavior of vertical trapezoidal CSSWs stiffened with flat steel plate

Steel shear wall (SSW) is an efficient system used to construct and improve many structures over the past decades. The main weakness of the traditional flat plate SSW is the premature buckling of the plate, for which the corrugated steel shear wall (CSSW) is a suitable alternative. However, the reduced resistance of CSSW compared to flat SSWs is a disadvantage. In this research, their reinforcement by flat steel plates with different dimensions and thicknesses has been used to improve the behavior of vertical trapezoidal steel shear walls (VTSSW). The samples studied in this research were subjected to cyclic loading after verification in Abaqus finite element software. The outcomes showed that reinforcing CSSWs with flat plates increased strength and energy absorption between 6 to 63% and 16 to 92%, respectively. Also, the equivalent viscous damping has increased between 5 and 82%. Also, due to strengthening the CSSWs, the pinching phenomenon in the hysteresis curves has been reduced, and the sudden decrease in strength after buckling in the CSSWs without stiffener has been significantly reduced.

Proportional distribution pattern and modal principle of tuned viscous mass dampers for multi-degree-of-freedom structures

A tuned viscous mass damper (TVMD) is an inerter-based damper that has been adopted in several high-rise buildings in earthquake-prone Japan recently to protect the structures from seismic-induced vibrations. However, as a TVMD contains a mass element, it adds degrees of freedom to the controlled structure, making the system’s eigenmodes complex. Inspired by the Rayleigh damping matrix, this study proposes a mass-proportionally distributed TVMD (MPD-TVMD) system, which enhances the efficiency of TVMD utilization compared to the previously proposed stiffness-proportionally distributed TVMD (SPD-TVMD) system. It is theoretically proven in this study that when the arrangements of the TVMDs are proportional to the stiffness or mass distribution of the primary structure, the equations of motion of a TVMD controlled shear building can be decomposed into the eigenmodes of the uncontrolled structure. This modal principle allows structural engineers to estimate the response of the controlled structure by understanding the modal characteristics of the uncontrolled system, which is highly beneficial for preliminary design decisions and the retrofitting of existing structures. Furthermore, given that the damping properties at each story level are typically adjusted by the number of dampers installed, it is often unrealistic in practical design to maintain strict proportionality in damper distribution. Through numerical examples, this study demonstrates that TVMD systems with realistic distribution patterns that are slightly different from a strictly proportional distribution can still perform as effectively as strictly proportional systems, providing a comprehensive design basis for the application of inerter-based damper in practical engineering.

Closed-form solutions for the optimal parameters of three inerter-enhanced dampers (IEDs) equipped on a ground acceleration-excited structure

Replacing the viscous damper of tuned mass damper (TMD) with the proposed inerter-enhanced dampers (IEDs), novel vibration mitigation methods, namely the IED-TMDs, are proposed. Unlike the TMD, which brings only one additional freedom into the system, the proposed IED-TMDs introduce more freedoms into the considered dynamic system. As a result, the traditional fixed-point theory cannot be used. To address this issue, this paper develops an extended fixed-point theory. Firstly, the inerter and the springs of the IED-TMDs are optimized considering that all four fixed points are of the same height. The closed-form solutions for the optimal inerter and springs of the IED-TMDs are obtained. Secondly, to obtain the optimal damping ratio for the IED-TMDs with multi-fixed points, a new optimization criterion is introduced. Different from the traditional fixed-point theory which controls the slope of the transfer function at the fixed points, the new optimization criterion assumes that the local peaks of the transfer function in between the four fixed points have the same height as the fixed points. And, a flat plateau is achieved in the transfer function. Further, the closed-form solutions for the optimal damping ratio are simplified in consideration of actual applications. Finally, the vibration mitigation performance of the IED-TMDs is evaluated. Results show that the vibration mitigation performance of IED-TMDs is superior to that of the conventional TMD. This superior vibration mitigation performance is more significant for the IED-TMDs with a smaller mass ratio.

Singular viscoelastic perturbation to soft lubrication

Soft lubrication has been shown to drastically affect the mobility of an object immersed in a viscous fluid in the vicinity of a purely elastic wall. In this theoretical article, we develop a minimal model incorporating viscoelasticity, carrying out a perturbation analysis in both the elastic deformation of the wall and its viscous damping. Our approach reveals the singular-perturbation nature of viscoelasticity to soft lubrication. Numerical resolution of the resulting nonlinear, singular, and coupled equations of motion reveals peculiar effects of viscoelasticity on confined colloidal mobility, opening the way towards the description of complex migration scenarios near realistic polymeric substrates and biological membranes. Published by the American Physical Society 2024

Analysis of G+20 Horizontally Connected Buildings with and Without Fluid Viscous Dampers

As urban populations continue to grow globally, the demand for new cities and high-rise structures is increasing due to limited land resources and expanding social and commercial activities. To address these challenges, this study investigates the seismic performance of G+20 horizontally connected buildings, focusing on the effects of fluid viscous dampers (FVDs) on structural response. A 3D model of two G+20 buildings, one with and one without FVDs, was developed using ETABS software, and seismic analysis was conducted for a Zone V seismic region in India. The study evaluates key performance parameters, including storey displacement, storey drift, and storey shear, to assess the effectiveness of the dampers. Results showed that adding FVDs significantly reduced overall building displacement, particularly in the X-direction at the top storey, with a reduction of approximately 40%. The Y-direction saw a more modest 5% reduction, attributed to geometric and stiffness irregularities. Additionally, storey drifts in the X-direction were higher than in the Y-direction but were significantly reduced after installing dampers. The findings highlight the importance of FVDs in improving the seismic resilience of horizontally connected high-rise buildings and offer valuable insights for future structural design in earthquake prone areas.

Application of pole allocation to optimize passive viscous dampers represented by the Maxwell model

The Maxwell model is used to understand the realistic effectiveness of vibration reduction in the building structures. The model consists of a dashpot and spring in series. The dashpot and spring represent a viscous damper and joint between the damper and the structural frame, respectively. However, few studies have investigated the optimal damper capacity and the corresponding spring stiffness in the practical parameter ranges. Additionally, the optimal damper derived using the fixed-point theory has no relationships with that derived via pole allocation. Therefore, in this study, to examine the effects of the joint spring, the pole allocation method was used to design a structural system wherein the Maxwell model was incorporated into a single-degree-of-freedom damped model. We introduced a closed-form expression, which explicitly described the relationships between the target structural damping ratio, damper capacity, and joint spring. The Maxwell model constrained the control effectiveness using damper parameters and simultaneously suggested an optimal and realistic joint spring for the damper. Pole allocation was also applied to a multi-degree-of-freedom (M-DOF) damped structural system employing multiple Maxwell models. The newly proposed optimized joint spring could easily control the additional damping effect on the M-DOF system. The Maxwell model can be optimized almost manually. The scheme is more useful in the preliminary design stage than the previous numerical optimizations. This study extended the mathematical equation governing the building vibrations to the Maxwell model. The extended equation served as a unified description for considering structural passive control.

Spectro-spatial analysis of van der Pol-type phononic crystals

Abstract The application of phononic chains as metamaterials demonstrates their remarkable capability to manipulate the propagation of waves. These periodic structures yield frequency-dependent behavior of material comprising characteristics with many possible engineering applications. In this paper, we investigate the weak and general nonlinear behaviors of the van der Pol-type damped phononic chains. The analysis of wave propagation is initially conducted for a one-dimensional structure, and subsequently, is extended to consider the wave motion through two-dimensional and three-dimensional lattices. Results are obtained using the method of multiple scales and a Spectro-spatial analysis by employing the numerical method of the 4th-order Runge–Kutta. A new phase-diagram relation within the chain’s unit cell is also introduced aiming to enhance the numerical findings. Our results indicate that in the weakly nonlinear regime, the van der Pol-type damping closely follows the linear dispersion curve, regardless of the initial amplitude. This suggests a symmetry between energy pumping and dissipation modes, where hardening and softening behaviors align with linear characteristics of common damping mechanisms, such as viscous damping. Additionally, the formulation demonstrates the existence of limit-cycle stability in the motion of each mass. For the general damped system, it is observed that a special frequency exists where the system converges, for all wave numbers similar to the synchronization effect. Hence, the motion and the frequency of all masses are synced. Additionally, non-reciprocal wave propagation is observed, resulting in a bandgap structure with a symmetry breaking occurring near the limit cycle. These results are promising in the fields of wave emitters, wave filters, and signal encryption.

Investigation of Seismic Behavior of Slope Supported by Pile-Anchor Structure with Dampers

ABSTRACT The pile-anchor structure has been widely studied by global researchers. However, there is still little research on seismic optimization measures considering energy dissipation. In this research, the seismic performance of the pile-anchor structure is optimized by setting viscous dampers on the anchor cables. Shaking table tests are conducted to compare the seismic response of this new structure with that of the ordinary structure. Meanwhile, an analysis of the seismic energy dissipation law under the support of both structures was conducted. Those results show that the seismic performance of the pile-anchor structure can be greatly improved by setting dampers.