Friction Damper Research Articles

A self-centering hybrid braced precast wall with replaceable U-shaped flexural plates: Experimental and theoretical analysis

A self-centering hybrid-braced precast wall with replaceable U-shaped flexural plates (UFPs), which is composed of a hybrid braced wall, post-tensioned (PT) strands, and steel wall toes, is proposed. The UFPs bolted inside the steel wall toes, which yield at the same thickness outside the plane of the steel plate when wall rocking, providing plastic bending energy dissipation. The steel wall toe made of H-shaped steel provided increased compressive strength and space for the installation of the UFPs. Four wall specimens with varying initial PT forces, UFPs of different thicknesses, and different dampers were investigated using low-cyclic loading tests. After replacing the UFPs, one wall was retested to assess its performance. The precast walls sustained significantly low damage and showed large self-centering capabilities. The maximum drift was up to 4.5%, which far exceeded the specified requirements, and the lateral load still maintained an increasing trend. When the initial PT force was increased, the bearing capacity, initial stiffness, and self-centering capacity of the precast wall increased. When the thicknesses of the UFPs were increased, the energy-dissipation capacity and self-centering capacity of the wall increased and decreased, respectively. The self-centering and bearing capacities of the repaired wall met the seismic requirements but were slightly lower than those of the original wall. The wall with UFPs performed better bearing capacity and stiffness than the wall with variable friction dampers (VFDs) before 1.5% drift. Additionally, the opening load of the wall, the load at the yield of UFPs, and the load at different compression sections were calculated and compared against the test results. The analysis method was able to predict the behavior of the walls reasonably well.

Wave equation with viscoelastic acoustic boundary conditions and supercritical source term

This paper is concerning with the study of Hadamard well-posedness for a wave equation with nonlinear internal damping and acoustic boundary conditions for non-locally reacting boundary. On the boundary we consider the action of viscoelastic and frictional damping and also a supercritical source term. To prove the existence of solution we use semigroup theory. We also study the asymptotic behavior of the functional energy associated to the problem.

Seismic Performance of Steel Moment Frame with Side-Plate Connections Combined with Friction Dampers

With the gradual change in the design method of structures from resistance-based methods to performance-based methods, existing common building frames do not respond to the criteria of these methods, and if these frames are designed with new performance criteria, the design will be uneconomical. The basic problem of the existing types of frames is the imbalance between hardness and plasticity in them. A structure must have sufficient hardness in order not to be displaced in an earthquake, and it must have high ductility in order to dissipate the energy of the earthquake well. In this article, the purpose of the structure's performance in the combination of friction dampers and side-pleat joints in the steel structure of the bending frame is according to the constraints in solving the problem such as architectural, executive and design limitations and considering the uncertainties inherent in the system. This problem is solved in such a way that all three conditions are estimated, and for this purpose, three structures, 6, 10, 15 stories, have been modeled in three dimensions and have been analyzed under time history analysis. In examining the arrangement of dampers in the frames, the amount of energy in the 3x3 structures in the second frame is more than the first frame, which has increased by about 15%. But in 5x5 structures, the amount of energy when the frame damper is 3 is more than other frames. In these structures, when the damper is in the third frame, the energy of the structure has increased by about 10% compared to other states. Also, the effect of side plate connection in increasing the hardness is also important. that the above connection will reduce displacement by creating hardness at the connection point, and as a result, it will absorb more energy.

An optical method to monitor transparent contact interfaces during high frequency shear vibration cycles

Contacting interfaces provide frictional damping in jointed structures subjected to high dynamic loads. Predicting this frictional damping during vibration cycles is highly important since it strongly affects the dynamic response of the assembly and hence the lifetime of parts. Since frictional damping is heavily influenced by the contact condition at the interface, the most direct and insightful approach is thereby to actively monitor the contact interface. Although several methods have already been proposed to monitor the contact interfaces quasi-statically or in pre-sliding, such as digital image correlation, X-Ray and ultrasound, only limited data is available of the frictional interface behaviour during high frequency vibration.To provide a better insight into the contact interface behaviour during high frequency cyclic motion, an optical method is here developed based on transparent friction specimens and total internal reflection, and applied to an existing friction test rig. The resulting measurements across the whole interface show a large variation in the real area of contact during each vibration cycle, which could be linked to the kinematics of the contact interface. This large variation is observed for the first time in high frequency oscillating contacts and is attributed to ageing effect and fracture of asperities. These two effects dominate the contact mechanism at different sliding velocities and induce variations in the real area of contact during each vibration cycle. These results suggest that the mechanisms behind high frequency contact behaviour are more complex than what commonly assumed in dynamics simulations.

A State-of-the-Art Review of Passive Energy Dissipation Systems in Steel Braces

An extensive investigation of the international literature is carried out regarding the passive energy dissipation systems and more specifically the dampers that can be positioned in steel braces to increase the absorption of seismic energy and to protect them from buckling, such as Friction (FDs), Metallic (MDs), and Viscous dampers (VDs). This review paper systematically reviews/refers to 196 publications from the literature; it presents a brief overview of the steel braces frames and their problems. The efficacy of all of these types of dampers has been proved, as they have been used all around the world, and their comparison in experimental or numerical studies, applications, and optimization shows that there is no unilateral solution, as the appropriate selection of effective retrofit strategies takes into account parameters such as cost, duration, technical aspects, architectural needs, etc. Finally, the aim of this review paper is to systematically present an overview of passive energy dampers that can be installed on steel braces, summarize the advantages and the disadvantages of each one, compare global parameters such as the relation of velocity and damper force, economic details, and type of study, and facilitate future researchers working in the related field, for its better understanding and development.

Influence of gravity connections and damper activation forces on the seismic behavior of steel CBF buildings with dissipative floor connectors

AbstractThis paper investigates the influence of typical gravity connections on the seismic demands of steel concentrically braced frame (CBF) buildings with friction dampers as dissipative floor connectors. The investigated connections include (i) typical shear tab, (ii) clip angle, (iii) flush end‐plate and (iv) shear tab connections with bottom T‐stub. It is shown that the seismic behavior of the gravity framing system (GFS) is practically insensitive to the gravity connection type because the supplemental damping provided by the dissipative floor connectors dominates the seismic response of the GFS. While flush end‐plate and shear tab connections with bottom T‐stub generally exhibit smaller rotational demands than more flexible gravity connections, the resultant lateral drift demands in the GFS are more‐or‐less identical in all cases due to the elastic contribution of the gravity columns. A simplified method is proposed to evaluate the influence of the damper activation forces on the seismic response of multi‐story CBF buildings equipped with floor sliding friction dampers. First, the building is transformed into an equivalent single‐degree‐of‐freedom system. Subsequently, dual graphics called P‐spectra are generated through nonlinear response history analysis. These graphics allow to estimate the peak floor absolute acceleration demands and peak/residual roof displacements of the GFS as a function of the activation forces of the sliding friction dampers. An application example demonstrates that the proposed method can be reliably employed in a pre‐design phase to identify the range of damper activation forces through which an optimal performance of the steel CBF building may be anticipated.

Performance-based optimization of nonlinear Friction-Folded PTMDs of structures subjected to stochastic excitation

Alternative Tuned Mass Damper (TMD) configurations have been proposed in the literature for performance improvement and maintenance, mainly modifying their restoring force or dissipation mechanisms. In this context, Folded-Pendulum TMDs (FPTMDs) are appealing for tuning low-frequency structures because they are compact and easy to retune while avoiding sliding mechanisms. In turn, Friction Dampers (FDs) are equally attractive due to their minimal maintenance and easy desired capacity adjustment. Nevertheless, despite recent advances in integrating FDs with PTMDs, a comprehensive literature survey reveals that Reliability-Based Design Optimization (RBDO) studies for PTMDs or Folded-PTMDs with FDs cannot be found to the best of the authors’ knowledge. Hence, the present paper aims at performing an original RBDO of single and multiple Friction-Folded-PTMDs in buildings subjected to stochastic excitation. Unlike the existing optimization studies in this field, a complete nonlinear description (dry friction plus large rotations) is employed because the considered applications involve high-intensity excitations, like wind and seismic loading. Finally, scenarios with multiple absorbers are included due to their associated performance and constructional advantages. Optimal design of multiple Folded-PTMDs with FDs has not yet been addressed, as they increase the optimization problem complexity leading to multimodal and convex objective functions. Accordingly, an active-learning Kriging-based Efficient Global Optimization (EGO) procedure is used, which allows for finding the optimum solutions with only a few objective function evaluations. The application cases to two distinct buildings subject to wind and seismic loadings show that using Friction-FPTMDs allows for obtaining a control strategy with an appropriate performance while ensuring practical advantages over classical TMDs.

P-bifurcation phenomena of the non-smooth modified rayleigh-duffing oscillator under the combined action of harmonic excitation and noise perturbation

In this paper, the stochastic dynamics of a modified Rayleigh-Duffing oscillator with Coulomb frictional damping and elastic impact is investigated under combined harmonic and noise excitations. On the premise of retaining the non-smooth properties, a non-smooth steady-state probability density response numerical calculation method is introduced by taking advantage of Markov process. Utilizing this method, the stochastic P-bifurcation phenomena of oscillators without and with externally excitation are discussed in detail by inscribing changes in the topology of the steady-state probability density function. It is displayed that certain nonlinear damping coefficient and external excitation amplitude change the structure of the response, and that both the friction coefficient and the elastic coefficient of the contact surface induce stochastic P-bifurcation phenomena in systems without and with harmonic excitation, respectively. This study reveals the effect of non-smooth factors on the stability of the Rayleigh-Duffing oscillator.

Seismic Analysis of RC Buildings Using X-Braced and Inverted V-Braced Friction Dampers

Seismic Analysis of RC Buildings Using X-Braced and Inverted V-Braced Friction Dampers

Proof of Concept and Preliminary Validation of an Analytical Model of an Energy Dissipator for Tension Loads with Self-Centering Capacity

A novel energy dissipation device is proposed to protect structures against dynamic loads. A conceptual model of the device is presented, describing the fundamental components of its operation. This model has a linear elastic element and a frictional damper. The equilibrium equations that lead to the relationship that governs its behavior are proposed. A functional model of the device was built on a 3D printer with PLA filament. Experimental trials were carried out to characterize its elastic component and the coefficient of friction of the damping parts. Proofs of concept load-unload tests were also carried out on the device, subjecting it to cyclical movement sequences. The results of the first two types of tests allowed the parameters of the previously developed analytical model to be calibrated. The results of the load-unload tests were compared with the predictions of the analytical model using the calibrated parameters. Consistency was observed between the experimental and analytical results, demonstrating the basic attributes of the device: self-centering capacity, dissipation capacity and force proportional to the displacement demand. It is concluded that the proposed device has the potential to be used effectively in the protection of structures under dynamic loads.

Effectiveness of High-Damping Rubber (HDR) Damper and Tuned Mass—HDR Damper in Suppressing Stay-Cable Vibration

High-damping rubber (HDR) dampers have the advantages of convenience for various shapes of pressure blocks, aesthetic installation, easy maintenance, temperature stability, etc.; thus, they present good application prospects in the vibration reduction of stay cables. Hence, a model of a taut cable equipped with two types of HDR damper—i.e., HDR damper and tuned mass–high-damping rubber damper (TM-HDR-D)—is established herein. Then, based on this theoretical model, the effect of each damper acting alone and in combination on the cable’s additional modal damping is studied. Finally, an actual cable of a cable-stayed bridge is used to study the effectiveness of two dampers for practical engineering. The results show that, when the TM-HDR-D has a small mass, the total additional modal damping of the cable approximates the superposition of the respective effects of the two dampers. The damping effect of HDR mainly depends on its stiffness and installation position; meanwhile, the damping contribution of TM-HDR-D is mainly related to its tuning frequency and installation position. In practical engineering, the smaller installation mass of TM-HDR-D can make up for the lack of damping enhancement of the cable-end HDR damper.

Seismic Behavior of Multi-Storey Structure Using Different Energy Dissipation Devices A-review

Earthquake is a most disaster event, responsible a lot of structural damage and casualties worldwide on the earth’s surface without any early warning. The trends in using dampers in buildings and tall buildings, increasing yearly based on their outstanding feature during an earthquake event. Typically, there are four types of energy dissipation device system such as friction damper, viscous damper, viscoelastic damper and metallic damper. The theoretical and experimental study results indicate that all fourth types of dampers can be able to minimize the structural damages and cracking during an earthquake occurrence event. But only viscous damper device has an acceptable feature against of earthquake forces as compare to other kinds of damper devices in symmetric and asymmetric building plan configurations as well. Based on the reviews, a viscous damper device system plays major role in reducing the lateral displacement of buildings about 30% to 85%, inter-storey drift of building about 60% to 80% and 1487.82KN drop in base shear of structural components in symmetric and asymmetric building plan configurations upward as compared to friction dampers, viscoelastic dampers and metallic dampers. Contradictory, dampers can decrease the construction cost limitation of multi-storey structures economically rather than conventional buildings.

Hysteretic model for bending-type frictional steel truss coupling beams

As a novel coupling beam for coupled shear wall structures, the bending-type frictional steel truss coupling beam (BFTCB) concentrates the deformation and energy dissipation in friction dampers at the bottom chord, allowing the main body to remain elastic during earthquakes. As the preparatory work for resilient structure design based on the BFTCB, this work concentrates on developing the hysteretic model for BFTCB. Firstly, the BFTCB stiffness-strength decoupling mechanism was introduced, i.e., the shear strength is provided by friction dampers while webs control its initial stiffness. Secondly, a hysteretic model that reflects the BFTCB two-stage sliding characteristic was proposed. The model consists of a trilinear backbone curve and the unloading and reverse loading rules. The model has eight control parameters, of which two core parameters (initial stiffness and limiting shear strength) are derived from the BFTCB stiffness-strength decoupling mechanism, whereas the remaining parameters are obtained by theoretical analysis and empirical calibration. The hysteretic model was then compared with the test curves and demonstrated good accuracy. Finally, a series of FE prototypes of BFTCB with different design stiffnesses and strengths was adopted to verify the hysteretic model. The results showed that the proposed model fitted well with the FE prototypes, indicating its applicability to BFTCB with varying core design parameters. Therefore, the hysteretic model can be adopted for BFTCB to support the resilient shear wall structure design.

Tunable Impact and Vibration Absorbing Neck for Robust Visual-Inertial State Estimation for Dynamic Legged Robots

We propose a new neck design for legged robots to achieve robust visual-inertial state estimation in dynamic locomotion. While visual-inertial state estimation is widely used in robotics, it has a problem of being disturbed by the impacts and vibration generated when legged robots move dynamically. The use of rubber dampers may be a solution, but even if the dampers are proper for some gaits, they may be excessively deformed or resonated at certain frequencies during other gait locomotion since they are not tunable. To address this problem, we develop a tunable neck system that absorbs the impacts and vibration during diverse gait locomotions. This neck system consists of two components: 1) a suspension mechanism that compensates for the weight of the head equipped with a camera and IMU (inertial measurement unit), absorbs the impacts and the head motion of high frequencies including vibration as a fixed low-pass filter; and 2) a dynamic vibration absorber (DVA) that can be reactively-adjusted to diverse gait frequencies to alleviate excessive head movements. We present a dynamics analysis of the neck system and show how to adjust the target frequency of the system. Simulation and experimental validation are performed to verify the effect of the proposed neck design, manifesting superior estimation performance and robustness across diverse gaits.

Experimental study of precast self-centering concrete shear walls with external friction dampers

Self-centering walls perform relatively well in reducing structural damage and residual deformation owing to the joint rocking mechanism. Nevertheless, drawbacks of the self-centering walls were limited robustness and redundancy, thus sufficient dissipating capacity is essential for improving stiffness, reducing seismic response, and controlling structural collapse. Among all these dampers used in self-centering systems in previous studies, slip-friction dampers are highly preferred because of their simplicity, perfect rigid-plastic hysteresis characteristic, large stroke, and stable dissipating capacity. After the earthquake ceases, friction force can be eliminated by loosening the tightening bolts to help facilitate post-earthquake recovery, and it is convenient to be replaced or repaired. In the present study, experiments of asymmetric friction dampers with brass-steel interfaces were conducted. To obtain the optimal characteristics for stable dissipating, different configurations of slip-friction dampers were designed and tested. The friction dampers were further installed vertically at the base rocking joint of the self-centering shear walls, and the performance of the walls was studied under horizontal quasi-static cyclic loading. Application of the friction dampers significantly increases the energy dissipating capacity and the post-yield stiffness. The energy dissipating ratio improved up to 81.2% compared to rocking walls with no additional damping. Damage was limited to the brass shims in friction dampers, while wall specimens were able to exhibit up to 3.0% horizontal drift without cracks, degradation, and significant concrete damage at the boundary elements. An average maximum residual drift of both positive and negative directions observed at the end of the test was 0.415% at 3.0% horizontal drift, that major structural realignment is not required, and repair of the structure is practically feasible.

Experimental Characterization, Modeling, and Numerical Evaluation of a Novel Friction Damper for the Seismic Upgrade of Existing Buildings

The paper presents the experimental characterization, the formulation of a numerical model, and the evaluation, by means of non-linear analyses, of a new friction damper conceived for the seismic upgrade of existing building frames. The damper dissipates seismic energy through the friction force triggered between a steel shaft and a lead core prestressed within a rigid steel chamber. The friction force is adjusted by controlling the prestress of the core, allowing the achievement of high forces with small dimensions, and reducing the architectural invasiveness of the device. The damper has no mechanical parts subjected to cyclic strain above their yield limit, thereby avoiding any risk of low-cycle fatigue. The constitutive behavior of the damper was assessed experimentally, demonstrating a rectangular hysteresis loop with an equivalent damping ratio of more than 55%, a stable behavior over repeated cycles, and a low dependency of the axial force on the rate of displacement. A numerical model of the damper was formulated in the OpenSees software by means of a rheological model comprising an in-parallel system of a non-linear spring element and a Maxwell element, and the model was calibrated on the experimental data. To assess the viability of the damper for the seismic rehabilitation of buildings, a numerical investigation was conducted by performing non-linear dynamic analyses on two case-study structures. The results highlight the benefits of the PS-LED in dissipating the largest part of seismic energy, limiting the lateral deformation of the frames, and controlling the increase in structural accelerations and internal forces at the same time.

Pre-tensioned SMA cable tests and its application in a novel self-centering viscoelastic damper

The elastic modulus of superelastic NiTi shape memory alloy (SMA) is between normal structural steel and viscoelastic materials. To enhance the initial stiffness and self-centering capability of viscoelastic (VE) dampers, an innovative self-centering high-damping rubber damper (SC-HRD), which is parallel composed of an SMA-cable-controlled self-centering system and a traditional high-damping rubber damper, was proposed and investigated in this study. The influence of initial strain, loading amplitude, and strain rate on the behavior of SMA cables after training and pre-tensioning was also tested for the SC-HRD application. Configuration and working principles of the SC-HRD were subsequently illustrated, followed by numerical studies on the behavior of the novel damper. Parametric analyses were then carried out on several design parameters of the SC-HRD to optimize its mechanical performance. Results show that the initial stiffness and residual self-centering strength of the SMA cables, which are essential for the SC-HRD application, can be enhanced with the increasing initial strain and loading strain rate. Compared with traditional VE dampers, the SC-HRD has better initial stiffness and self-centering capacities. Initial strain and relative area ratio of the pre-tensioned SMA cables in the proposed SC-HRD are suggested to be designed as about 2% and 0.123%, respectively, to achieve appropriate initial stiffness, energy dissipation, and residual deformation of the proposed SC-HRD.

Test of a novel self-centering brace using SMA slip friction damper

This paper reports an experimental work on a novel self-centering brace, which is a serial combination of shape memory alloy slip friction damper and steel tube. The study initiates with describing the axial behavior, in-plane rotational behavior and global buckling behavior of the brace, and deriving the corresponding analytical equations. Then, cyclic loading tests are conducted to obtain the hysteresis behavior of shape memory alloy bolt and the coefficient of kinetic friction of the sliding surfaces, both of which are critical to the behavior of the brace. In what followed, four tests are carried out on a 1/3-scaled specimen, corresponding to four loading protocols. The testing results indicate that the brace exhibits a flag-shaped hysteresis, which is characterized by excellent self-centering capability and satisfactory damping capacity. Using the experimental data, this work quantifies the peak strength, secant stiffness, energy dissipation and equivalent damping ratio, and analyzes the local strains and deformations. Furthermore, three-dimensional finite element models are established for numerical simulations. The finite element models capture the global and local behavior of the brace. Both the analytical equations and numerical simulations agree reasonably well with the experimental data.

Discrete and Continuum Modeling of Coulomb Friction Damping in Stone Blocks

Friction plays an important role in creating damping mechanism in structures.In this paper a study was conducted to analyze coulomb friction damping andfrictional energy dissipation mechanism with stone blocks in a single degreeof freedom system by discrete and continuum modeling in finite element-based software ABAQUS. Discrete and continuum modeling approach wasused in this study. It was found that both approaches gave similar results.

Performance evaluation of friction dampers considering different metal pairs and loading rates

Metal friction dampers are widely applied for structural energy dissipation and shock absorption, and their dynamic performance needs further study. Cyclic loading tests were conducted on 30 specimens to evaluate the effects of loading sequence and rate under high speed (20 mm/s ∼ 60 mm/s) and low speed (0.2 mm/s ∼ 3 mm/s). The friction pairs included five types: brass-hot rolled steel with untreated surfaces (B-HS), brass-hot rolled steel with polished surfaces (B-PHS), brass-stainless steel (B-SS), stainless steel-hot rolled steel with untreated surfaces (SS-HS), and stainless steel-hot rolled steel with polished surfaces (SS-PHS). The test results showed that all specimens exhibited plump rigid-plastic hysteresis behavior under different loading rates, and the mechanical indices of the specimens met the discreteness requirements of FEMA-356. The loading rates obviously influenced the normal force loss and friction coefficient of the friction interfaces. The static friction coefficients for the five metal friction pairs were recommended, and analytical models of the dynamic friction coefficient concerning loading rate were established. It was suggested that the B-HS, B-PHS, SS-HS, and SS-PHS friction pairs should be pre-friction within the travel range before use, and the friction coefficient of the B-SS and SS-HS friction pairs should be calibrated after the first loading.