Dissipative Damping Research Articles

Propagation of eigenwaves in plane three-layer media

The paper considers the problem of propagation of natural stress waves in a strip that is in contact with an unbounded isotropic viscoelastic medium made of another material. It is assumed that there are no external influences during the propagation of natural waves. In some cases, the physical properties of viscoelastic materials are described by linear hereditary Boltzmann–Voltaire relations with integral differences of heredity kernels. Some of the layers can be elastic. In this case, the heredity kernels describing the rheological properties of the layers are identically zero. A system in which the rheological properties of the layers are identical (the nuclei of heredity of elements are equal to each other) will be called dissipatively homogeneous. In the particular case, when there are no external influences, the propagation of damped waves of the system is considered; — in the presence of external influences — forced. The main problem is the study of the dissipative (damping) properties of the system as a whole, as well as its stress-strain state.

Seismic Response Characteristics of a Utility Tunnel Crossing a River Considering Hydrodynamic Pressure Effects

As a long lifeline system of buried structures, the utility tunnel (UT) is vulnerable to earthquake invasion. For utility tunnels with inverted siphon arrangements crossing rivers, the seismic response is more complex due to the basin effect of acceleration in the topography and the influence of fluctuating hydrodynamic pressure, but there is currently a gap in targeted seismic response analyses and references. Based on a UT project in Haikou, this paper studied seismic responses of a cast-in-place UT considering the coupled model of water–soil–tunnel structure on ABAQUS software. Herein, the dynamic fluctuation of hydrodynamic pressure is simulated using an acoustic–solid interaction model. A viscoelastic artificial boundary was used to simulate the soil boundary effect, and seismic loads were equivalent to nodal forces. Considering seismic invading direction and varying water elevation, this paper investigates the dynamic response characteristics and damage mechanisms of river-crossing utility tunnels. This study shows that the basin effect causes the soil acceleration around the UT to show variability in different sections, and the amplification factor of the peak acceleration at the central location is almost doubled. The damage and dynamic water pressure of the UT are intensified under bidirectional seismic excitation, and the damage location is concentrated at the junction of the horizontal section and the vertical section. Bending moments and axial forces are the main mechanical behaviors along the axial direction. Changes in river levels have a certain positive effect on the UT peak MISES, DAMAGEC, and SDEG, and it exhibits a certain degree of energy dissipation and seismic damping effect. For the aseismic design of cross-river cast-in-place utility tunnels, bidirectional seismic calculations should be performed, and the influence of river hydrodynamic pressure should not be neglected.

Local and global integrative retrofitting of reinforced concrete frames using in‐plane buckling steel braces

AbstractTwo large‐scale, single‐storey, single‐bay reinforced concrete (RC) moment frames, designed as per an outdated seismic code to represent a typical framing detail of a four‐storey building, have been tested under displacement‐controlled quasi‐static loading protocol as per ACI 374.1‐05. The RC frames include a plinth beam with brick infill underneath, a slab monolithically cast with the top beam and provision for applying axial load to the column to simulate real construction scenario. One of the frames has been tested as a bare frame, and the second one has been retrofitted with conventional steel braces designed to undergo in‐plane buckling. The size of the brace has been selected based on the result of a nonlinear time history analysis of representative low‐ to mid‐rise open‐ground storey RC buildings. Post‐installed chemical anchors have been utilized to connect the steel braces to the narrow RC frame members following the outcomes of an experimental investigation by the same authors. Local‐level retrofitting by steel jacketing using adhesives has been designed and utilized on columns and beams to achieve the desired seismic response. The seismic performance of the retrofitted frame has been compared with the bare frame in terms of strength, stiffness, ductility, energy dissipation and hysteretic damping. The tests provide insight into the role of the plinth beam, effect of RC slab on the strong‐column weak‐beam aspect and the achievement of the desirable hinge mechanism through a precise design and detailing of global and local level retrofitting technique.

Two-dimensional viscous study of coupled nonlinear fluid resonances in two narrow gaps

The wave-induced hydrodynamics of coupled nonlinear piston-mode fluid resonances within two narrow gaps between three barges are numerically investigated using a two-dimensional viscous wave flume. This study aims to explore the time-dependent nonlinear interactions between fluid oscillations in the two gaps. The coupled synchronous dynamic behaviors of fluid oscillations during the transient evolution stage are first examined in terms of amplitude and frequency modulation. It is shown that phase dynamics, including phase slipping, trapping, and locking, play significant roles in establishing the coupled synchronous dynamic evolutions of fluid oscillations in the two gaps. The quasi-steady state of the amplitude- and phase-frequency responses of fluid oscillations within the gaps, along with the reflection and transmission waves in front of and behind the three-barge system, are further analyzed. This analysis clarifies the significance of viscous damping energy dissipation and radiation damping energy transfer involved in gap resonance problems. This clarification also explains the performance of fully nonlinear potential flow solvers in predicting fluid resonances in the two narrow gaps. Finally, the nonlinear dynamic features of fluid oscillations are examined. The effects of incident wave nonlinearity, i.e., wave steepness, on resonant frequencies, response amplitudes, energy dissipation, and reflection and transmission coefficients are investigated. Harmonic analysis via Fourier transformation reveals the contributions of first-, second-, and third-order harmonics to the overall response amplitudes. The physical insights gained from this study provide a deeper understanding of the coupled nonlinear dynamics of piston-mode fluid resonances in multiple narrow gaps.

Experimental study and multi‐scale refinement model of high damping acrylic polymer matrix VEDs for civil structural seismic retrofit

AbstractThe viscoelastic dampers (VEDs), which can provide both stiffness and damping, have been recently introduced into the field of structural vibration control for seismic enhancement of civil engineering structures. In this study, a kind of high damping acrylic polymer matrix VEDs (HDPVED) is developed independently, and this innovative HDPVED can solve the significant problem of service performance under medium‐high temperature environments, as well as low‐frequency vibration control under earthquake actions for civil engineering structures. To systematically investigate the influencing rules of frequency, temperature, and displacement amplitude on the mechanical properties and damping dissipation performance of HDPVEDs, a series of dynamic mechanical performance tests of the developed HDPVEDs are carried out at different frequencies, temperatures, and displacement amplitudes. The research results show that HDPVED exhibits excellent damping dissipation capability and adaptability under medium‐high temperature environments and low‐frequency excitations. The mechanical properties and energy dissipation performance present a strong correlation with frequency, temperature and displacement amplitude, and there is an obvious coupling effect between the three influencing factors. Based on the macroscopic mechanical property research of HDPVED, the microscopic damping mechanism and microscopic mechanical properties of HDPVED are then investigated. High‐order fractional derivative fraction Voigt and Maxwell model in parallel (FVMP) models are preferred to characterize the combined hyper‐elasticity and viscoelasticity owned by networked molecular chains and free molecular chains. The breaking and reconstruction theory of microphysical bonds is used to assess the effect of packing particles, and the time‐temperature equivalence principle is introduced to assess the effect of temperature. The multi‐scale refinement model is proposed, and the validity and accuracy of this model are verified by testing data of HDPVED. The study results show that the proposed model can accurately describe the effects of frequency, temperature, displacement amplitude, and microstructure on the multi‐scale mechanical properties of HDPVED. It provides a theoretical basis for the multi‐scale design and development of high damping VEDs.

Development and characterization of self-centering friction dampers with confined shape memory alloy bars

This study proposes a new self-centering, shape memory alloy bar-based device to address the tension-compression asymmetry and limited energy dissipation capacity of similar SMA bar-based devices. The proposed device, named the Confined Superelastic Friction Damper (CSFD), employs buckling-restrained SMA bars to maintain symmetry in force-displacement responses and enhance effectiveness in both tension and compression. The device also integrates a frictional damping mechanism, contributing to increased energy dissipation capacity. First, an optimal annealing condition is investigated for as-received SMA bars to achieve a satisfactory superelastic response. Then, the working and design principles of the CSFD are outlined. The experimental characterization of CSFD devices in various configurations is conducted under an increasing amplitude loading protocol. The devices are tested with different levels of frictional damping to assess the effects of the added frictional forces on device characteristics. Analysis of test results considers parameters such as hysteresis curves, maximum force, equivalent viscous damping, and self-centering efficiency to provide a comprehensive performance evaluation of each device. Findings reveal that while a single buckling-restrained SMA bar device exhibits up to 90 % higher forces in compression than in tension, a CSFD device with two such bars nearly eliminates this asymmetry. Compared to tension-only SMA devices, capable of symmetric response, the proposed CSFD device demonstrates a 2.6 times higher force-resisting capacity. For all devices, the addition of some frictional damping improves the energy dissipation and equivalent viscous damping capacity, while leading to some reduction in self-centering efficiency.

Cyclic behavior and shear strength of exterior reinforced concrete beam-column joints with inclined columns

The adoption of inclined columns results in inclined beam-column joints (BCJs). Although the behavior of regular BCJs have been widely investigated, researches on the cyclic behavior and shear strength of inclined BCJs are limited, and further investigations are required to ensure seismic safety of the frames adopting inclined columns. In this work, cyclic behavior of inclined BCJs was first experimentally studied by testing 3 exterior BCJ specimens. After that, a finite element model was developed and validated by the experimental results. The model was subsequently used for parametric study to reveal the effects of key parameters on the joint shear strength. In the end, a theoretical model based on the softened strut and tie model was proposed to estimate the joint shear strength of inclined BCJs. Results showed that the inclination caused an initial joint shear force under column axial load, leading to different joint behavior in positive and negative loading directions. The joint shear strength was increased in the inclination direction but declined in the other direction, while the ductility showed an opposite trend. Meanwhile, regardless of the inclination direction, energy dissipation and equivalent viscous damping of BCJs were reduced and stiffness degradation was slowed. The parametric study revealed that the inclination effect was amplified with higher inclinations. The overall joint shear strength can be effectively enhanced by adopting higher concrete strength and column axial load. Increasing the joint stirrup ratio was also beneficial for the shear strength, but its efficiency was relatively lower. Based on the comparison of the predicted joint shear strengths and those from experimental and numerical programs, it was proved that the modified strut and tie model was advantageous over the formulas in GB 50010 in capturing the shear strengths. This work contributes to understanding the cyclic behavior and shear strength of inclined BCJs to improve seismic safety of frames adopting inclined columns.

Meta-barriers for ventilated sound reduction via transformation acoustics

Resolving the trade-off problem between wave obstructing and flow transport is an intriguing but challenging task that may find potential applications in many noise control scenarios. Herein, we present a meta-barrier for achieving broadband sound reduction yet keeping efficient ventilation based on transformation acoustics. The proposed meta-barrier consists of an internal core and a coating made of double-negative acoustic metamaterial with high damping dissipation. Unlike conventional barriers, the meta-barrier has a magnified scattering cross-section far beyond its actual size, allowing it to provide the coherent interference effect in addition to the enhanced blocking effect. The coherent interference effect can directly reduce the sound radiation efficiency of sound waves radiating from an aperture. Moreover, the inherent material loss in the coating has a positive effect on the sound reduction performance of the meta-barrier over a wide frequency range. The robust sound reduction performance of the meta-barrier is demonstrated numerically for the cases of large placed distances and wide-range incident angles. Experiments were conducted to confirm the effectiveness of a meta-barrier sample constructed of a plate-type double-negative acoustic metamaterial with multiple constituent layers for sound reduction and ventilation. The fabricated meta-barrier sample, with the wind-speed ratio of 75 %, can achieve superior sound attenuation in the frequency range of 500–1000 Hz. This work may inspire the design and development of passive acoustic devices to suppress low-frequency airborne noise while supporting large-area ventilation.

Seismic performance test of bolted U-shaped steel assembled shear wall

A new type of assembled shear wall with energy dissipation and seismic damping function was proposed for the damage mechanism and weak points of typical assembled shear wall structures under strong earthquake effects. Using a combination of model tests and numerical simulations, four new assembled shear wall specimens with a scaling ratio of 1:1.54 and a shear-to-span ratio of 1.52 were designed and fabricated. The corresponding seismic performance tests were carried out. The effects of the number of bolts, axial compression ratio and longitudinal reinforcement ratio of edge members on the damage mode, hysteresis performance, bearing capacity, deformation performance, stiffness degradation and energy dissipation capacity of the specimens were systematically analyzed. The test results show that the damage mode of each specimen is basically the same as that of the common shear wall with the same shear-to-span ratio, which is bending-shear type damage However, the new assembled shear wall has more excellent hysteresis performance and energy dissipation capacity. Friction between the steel plates of the horizontal joints consumes a lot of energy and further inhibits wall damage. The energy dissipation value at the point of destruction of the wall is significantly higher than that of ordinary cast-in-place wall. The energy consumption value of the specimen PFSW is about 6 times that of a cast-in-place wall. When the number of bolts decreases, hysteresis performance decreases and wall deformation increases. The decrease of axial pressure ratio or longitudinal reinforcement ratio of edge members leads to the decrease of bearing capacity and increase of ultimate displacement of shear wall. Finally, the finite element model of the corresponding specimens was established by ABAQUS software. The simulation results were in good agreement with the test results, which indicated the correctness of the proposed model. And it can be applied to the analysis of new assembled shear walls.

Global solution of 3D MHD-Boussinesq system with mixed partial dissipation and thermal damping

Global solution of 3D MHD-Boussinesq system with mixed partial dissipation and thermal damping

Dynamic principle analysis of reinforced concrete replaceable coupling beam energy dissipation structure

Reinforced concrete shear wall is one of the most common structures in tall buildings. As an effective means to control structural vibration response, energy dissipation damping is widely applied to reinforced concrete shear wall structures. Replaceable steel coupling beams (RSCB) is a new technology in the energy dissipation damping field, and are being gradually adopted by construction projects since their introduction. However, current research on RSCB damping performance and space optimization has some shortcomings. This paper discusses RSCB working principles based on structural dynamics theory and derives damping performance curves of corresponding structures, and a primary evaluation of seismic response method for RSCB structures is proposed. Finally, the energy dissipation performance of a typical reinforced concrete shear wall structure is analyzed based on performance curves and formula of structural dynamics constructed by this paper. Relevant outcomes of this paper will provide theoretical support and technical guidance for construction design and in-depth research of RSCB.

Polynomial Mixing of a Stochastic Wave Equation with Dissipative Damping

Polynomial Mixing of a Stochastic Wave Equation with Dissipative Damping

Metamaterial-based absorbers for simultaneous absorption of air-borne sound and structural vibration

In this work, the idea of metamaterial-based absorbers is further extended to develop the concept of sound and vibration absorbers (SVA) capable of simultaneously absorbing sound waves propagating in air and structure. Each SVA unit cell consists of an outer coating and an inner core. The outer coating is a resilient closed-cell foam, superseding the commonly used open-cell porous materials to significantly improve the structural integrity and service endurance. The inner core embedded in the outer coating provides multidirectional inertia to introduce multi-modal interferences with the outer coating. Utilizing a combination of analytic and numerical techniques, we reveal the underlying physics of the SVA for the simultaneous absorption of sound and vibration. A proof-of-concept SVA sample was fabricated using an expanded polyethylene foam as the outer coating and a polylactide hollow cylinder as the inner core. Good agreements are observed between the simulated and experimental results in terms of the normal incident sound absorption coefficients and the frequency response functions. We find that the SVA exhibits two nearly-perfect sound absorption peaks at 850 Hz and 1210 Hz owing to the resonant-induced impedance matching. Meanwhile, the SVA can effectively attenuate structural vibration across an ultra-wide frequency range relying on the effects of the locally-resonant bandgap and the structural damping dissipation. Finally, the noise reduction feasibility of the SVA sample applied in a plate-cavity coupled system was demonstrated. Our reported findings open alternative perspectives for the construction of practical metamaterial-based absorbers to attenuate noise propagating in complex transmission paths.

Nonlinear enhanced dissipation and inviscid damping for the 2D Couette flow

Nonlinear enhanced dissipation and inviscid damping for the 2D Couette flow

A Light-Powered Liquid Crystal Elastomer Roller.

Achieving and controlling the desired movements of active machines is generally accomplished through precise control of artificial muscles in a distributed and serialized manner, which is a significant challenge. The emerging motion control strategy based on self-oscillation in active machines has unique advantages, including directly harvesting energy from constant ambient light, and it has no need for complex controllers. Inspired by the roller, we have innovatively developed a self-rolling roller that consists of a roller and a liquid crystal elastomer (LCE) fiber. By utilizing a well-established dynamic LCE model and subjecting it to constant illumination, we have investigated the dynamic behavior of the self-rolling roller. Based on numerical calculations, it has been discovered that the roller, when subjected to steady illumination, exhibits two distinct motion regimes: the static regime and the self-rolling regime. The self-rolling regime, characterized by continuous periodic rolling, is sustained by the interaction between light energy and damping dissipation. The continuous periodic rolling observed in the self-rolling regime is maintained through the interplay between the dissipation of damping and the absorption of light energy. In the static state, the rolling angle of the roller begins to decrease rapidly and then converges to zero. Detailed investigations have been conducted to determine the critical conditions required to initiate self-rolling, as well as the essential system parameters that influence its frequency and amplitude. The proposed self-rolling roller has superiorities in its simple structure, light weight, alternative to manual labor, and speediness. This advancement is expected to inspire greater design diversity in micromachines, soft robotics, energy harvesters, and similar areas.

Quasi-static, cyclic loading tests of RAC brick masonry walls strengthened by basalt textile reinforced concrete

This study experimentally evaluated the performance of unreinforced masonry (URM) walls, with and without basalt textile reinforced concrete (BTRC) strengthening, under quasi-static in-plane lateral loading tests. Five half-scaled specimens were constructed using recycled aggregate concrete (RAC) bricks, including unreinforced and BTRC reinforced walls. The first URM wall served as a control specimen, while the remaining four specimens featured varying strengthening configurations, achieved by changing the number of textile layers (two and four) in the BTRC overlay and the strengthening patterns (single and double side). The failure modes, axial deformation behavior, lateral resistance, deformability, stiffness degradation, energy dissipation, and equivalent viscous damping of the tested walls were examined. BTRC strengthening altered the failure mode of URM walls from diagonal cracking accompanied by rocking to rocking and slight shear sliding, thereby maintaining the integrity of the wall at large lateral displacements. Increasing the textile layer enhanced lateral resistance and deformability. Applying a BTRC overlay to a single side of the URM wall yielded satisfactory improvements, with even greater efficiency observed when an equal amount of textiles was evenly applied on both sides. Finally, by taking the contributions of vertical and horizontal fiber yarns into account, a new model involving different failure modes was proposed to estimate the ultimate lateral resistance of BTRC-strengthened masonry walls, showing good agreement with experimental results.

WELL-POSEDNESS AND ASYMPTOTIC BEHAVIOR FOR THE DISSIPATIVE P-BIHARMONIC WAVE EQUATION WITH LOGARITHMIC NONLINEARITY AND DAMPING TERMS

This paper concerns with the initial and boundary value problem for a p-biharmonic wave equation with logarithmic nonlinearity and damping terms. We establish the well-posedness of the global solution by combining Faedo–Galerkin approximation and the potential well method, and derive both the polynomial and exponential energy decay by introducing an appropriate Lyapunov functional. Moreover, we use the technique of differential inequality to obtain the blow-up conditions and deduce the life-span of the blow-up solution.

Stability and decay rate of smooth solutions for the 3D Boussinesq equation with partial horizontal dissipation and thermal damping

In this paper, we investigate the stability and large time behavior of some three dimensional Boussinesq equations with the horizontal dissipation in the horizontal velocity components and thermal damping. Due to the lack of vertical dissipation in the horizontal velocity components and full dissipation in the vertical velocity component, these problems becomes very challenging. Combining the higher order Sobolev norm of the velocity and the temperature and decay estimates of the lower order Sobolev norm of the velocity and the temperature, the stability issue and precise decay rates have been built. The most difficulty is to estimate L1-norm of ‖∇hu‖L∞ in time variable t.

Scientific mechanism of bamboo acoustic vibration performance from structure-chemical perspective

The special melodious timbre of bamboo musical instruments is closely related to the multi-level, multi-scale, delicate structure of bamboo. In this study, the influence of different excitation surfaces, bamboo height, and bamboo age on acoustic vibration performance was investigated. The mechanism of the influence of the bamboo tissue structure on its acoustic properties was further investigated. The results show that the acoustic conversion efficiency (ACE) of the bamboo-green side is 1307.42 m4/kg·s, which is higher than that of the bamboo-yellow side (1218.60 m4/kg·s). The E'/G' ratio from the bamboo-green side is 8.21, lower than that of the bamboo-yellow side (8.45). The comprehensive acoustic performance near the root (0–1.6 m) of the plant is optimal and has the maximum ACE value; ACE value decreases gradually from root to tip. The comprehensive acoustic properties of 8-year-old bamboo are the best compared to other ages. The ACE values of 2-year-old, 5-year-old, and 8-year-old bamboo are 997.37 m4/kg·s, 1284.19 m4/kg·s, and 1355.82 m4/kg·s with E'/G' of 8.34, 8.64, and 9.49, respectively. A highly oriented vascular fiber is conductive to the vibrational efficiency of bamboo, while loose and porous parenchyma cells play a resonant and tonal role. Highly oriented microfibrils and a large number of pores with diameter > 50 nm create a sound transmission channel and resonance cavity, which is the structural basis of the clear timbre of bamboo. However, a damping dissipation effect is produced affecting the vibration capacity and vibration energy transfer of the cellulose microfibril when abundant pores < 50 nm in size are located in lignin and between hemicellulose and cellulose skeletons. The content of the matrix composed of hemicellulose and lignin in the cell wall creates a chemical material basis that affects the acoustic performance of bamboo. The structural characteristics of bamboo, including directional gradient structure, fiber-parenchyma two-phase composite structure, and muli-scale pore structure, as well as key chemical “rebar-cement-sand” components of the rigid cellulose macromolecular chain, viscoelastic hemicellulose, and lignin have synergistic effects on bamboo acoustic vibration performance.

Cyclic Behavior of Beam–Column Pocket Connections in GFRP-Reinforced Precast Concrete Assemblages

This paper presents details of an experimental program evaluating the behavior of six half-scale glass fiber–reinforced polymer (GFRP) reinforced concrete beam–column precast members connected together through pocket connections, which are subjected to cyclic loading. The novel beam–column connection was constructed by incorporating either epoxy resin or tensioned or untensioned GFRP rock bolts in conjunction with different-sized pocket connections. The effects of an additional connection bar between the column and beam components in the connection, as well as the confinement of the concrete around the pocket region, were also investigated. An innovative test setup was designed so that the beam–column joint could rotate without restraint provided by the supports. All specimens were tested under an incrementally increasing cyclic load. The load-carrying capacity, deformational behavior, failure modes, energy dissipation, and hysteretic damping were all recorded and evaluated. All specimens failed as a result of column failure within the pocket connection region. This was attributed to the relative rotational flexibility of the column with respect to the beam, owing to the low elasticity of the epoxy resin used in the pocket region, and hence the stress concentration at the column ends within the pocket area. According to the results, a pocket connection containing GFRP reinforcement providing confinement around the embedded area yielded the highest capacity, ductility, and energy dissipation under cyclic loading. The connection containing a GFRP bolt, regardless of whether or not the bolt was prestressed, did not significantly improve the performance of the connection. The findings presented here can be used for the design of precast elements reinforced with GFRP bars. Of particular relevance is application to jetties and other offshore concrete infrastructure where steel reinforcement (because of corrosion issues) needs to be replaced with GFRP reinforcement.