Full-scale Damper Research Articles

Experimental and numerical investigation of a steel yielding arc and ring damper

The use of yield steel dampers in structures improves seismic resilience by efficiently absorbing energy, reducing the impact of seismic forces, and enhancing overall safety and stability. This paper introduces Arc and Ring Dampers (ARDs), a replaceable structural fuse system with the goal of improving seismic performance of structures against earthquakes. The ARD configuration consists of a central ring surrounded by four arcs. For the first time, an experimental study is carried out on full-scale damper specimens to determine seismic performance and failure mechanisms under cyclic loading. Nonlinear finite element method (FEM) analysis is employed for numerical validation and parametric exploration, taking into account variables such as arc and ring thickness, ring and arc radius, and stiffener width. According to the results, by carefully selecting and designing the geometric characteristics of this damper, it would offer a remarkably efficient energy absorption capacity and a significant load-bearing ability, resulting in a 36 % increase in its equivalent damping ratio. This study also describes these geometric features in detail, including the arcs' and ring's width-to-thickness ratios. Furthermore, this damper maintains structural stiffness without degradation under cyclic loading conditions, showing good ductility up to a value of 5.5. The theoretical predictions here are in good agreement with the experimental outcomes.

Development of novel high damping rubber damper under axial compression dynamic load for energy-dissipation application

High Damping Rubber (HDR) has been a reliable and durable material used in bearings as seismic isolation devices for several decades. However, there has been no development of HDR as dampers to mitigate structural response caused by earthquake excitations, specifically by dissipating the induced energy applied to structures under direct axial load. This paper aims to address this gap by developing a novel HDR damper utilizing Hyper Elastic Composite Material (HECM) and conducting experimental investigations to determine its damping ratio, compressibility, and elasticity behaviour under axial dynamic compression load for effective dissipation of dynamic loads. The research methodology involved performing response spectrum analysis (RSA) on a model of actual building structures, following the guidelines of National Annex to MS EN 1998–2017. Subsequently, the dampers were incorporated into the model to achieve a seismic base shear value without seismic actions, as determined by the RSA. Full-scale dampers were then developed using three different HECM variants (NR- A, B and C), selected based on their achievement of a damping ratio of more than 10% as bearing isolators using the shear method according to EN 15129:2009 cl. 8.2.4.1.5. The developed dampers underwent testing for damping and wind load in accordance with EN 15129 cl. 7.4.2.7 and cl. 7.4.2.8, respectively, incorporating the testing parameters derived from the model's RSA. Finite element models (FEM) were developed and accurately simulating the hysteresis curves and damping properties of the HDR damper. The properties of HECM in the FEM were derived from the simulation results and can be utilized for future damper design, ensuring compliance with industry requirements. Additionally, an empirical formula will be developed to enable structural designers to estimate the mechanical properties of the tested damper. The testing shows that NR-C HECM damper is able to achieve 10.46% under 1.8 Hz requirement and able to exceed more than10% damping ratio up to frequency 2.3 Hz, thus providing an alternative energy dissipation damper in the building industry.

Experimental evaluation and numerical simulation of low-yield-point steel shear panel dampers

Shear panel dampers are considered as a type of reliable passive energy dissipation device for seismic resistant structures with a damage-controlling concept. It has been revealed that the shear bulking of core plates and the premature failure of boundary plates are the main concerns for a shear panel damper that result in insufficient energy dissipation and undesirable ultra-low cycle fatigue performance. This study utilizes square steel tubes serving as out-of-plane stiffeners for the core plates made of a low-yield-point steel with a nominal yield stress of 225 MPa (named LYP225 steel). Meanwhile, a reduced flange plate section is adopted to mitigate the end fracture. An experimental study is carried out on three full-scale damper specimens with different flange plates and loading protocols. The test results show that the square tubes well prevent the bulking of the core plates and all the specimens exhibit plump hysteretic response and satisfactory energy dissipation capacity. The reduced plate sections reduce the likelihood of crack propagation occurring at the flange end, and thereby improve the ultra-low cycle fatigue performance. In order to develop the numerical model of shear panel dampers, a combined-hardening constitutive model with a memory surface is applied to represent the plasticity of LYP225 steel. Based on a plasticity analysis, a simplified calibration procedure is proposed associated with the three-dimensional constitutive model, where the plasticity parameters of LYP225 steel are determined using only the monotonic tensile test data. Eventually, the numerical results of uniaxial specimens and damper specimens are in good agreement with the test results, which validates the effectiveness of the constitutive model and the proposed calibration method.

Performance assessment of disc spring-based self-centering braces for seismic hazard mitigation

A novel type of self-centering bracing system employing a disc spring-based damper is presented in this study. The proposed damper employs a special detailing which enables fast assembly and reliable mechanical performance, and has high flexibilities in load resistance, deformability and energy dissipation capacity, catering to various design objectives. The working principle of the damper is first introduced, followed by a comprehensive experimental study on six full-scale damper specimens subjected to different loading protocols. The specimens exhibit very stable flag-shaped hysteretic behavior and are fully reusable with almost no damage after experiencing the considered test sequence. Reliable energy dissipation is provided by the dampers with little sensitivity to the repeated cyclic loading, where a typical equivalent viscous damping of 20% is achieved at large deformations. The work is then extended to a system level analysis, considering varying brace parameters, to evaluate the effectiveness of the self-centering bracing system in seismic control. A buckling-restrained braced frame is also included in the analysis for comparison. Among other findings, the study indicates that the fullness of the flag-shaped hysteresis is a critical factor affecting the key structural performances. In particular, decreasing the energy dissipation factor is effective in eliminating the residual deformation, but at the cost of amplified peak deformation and floor acceleration responses. A “partial self-centering” system, which allows certain static residual deformation of the brace, is found to simultaneously suppress the peak deformation, residual deformation, and peak floor acceleration.

Shear thickening fluid damper and its application to vibration mitigation of stay cable

Stay cables are vital structure elements of cable-stayed bridges, which feature large span, high flexibility and low damping properties. The vibration control of stay cables is of very importance to ensure the serviceability and integrity of cable-stayed bridges. This paper concerns the design of a novel self-adaptive full-scale damper with shear thickening fluid (STFD) and its application to the mitigation of undesirable cable vibration. Dynamic experiments are performed to study the properties of the STFD under a series of sine wave at different frequencies but a constant amplitude. The output damping force of the STFD significantly increases as the velocity increases and a phenomenological model is proposed to fit the observed performance of the STFD. A general differential equation of the cable attached with a STFD is developed to solve the eigenvalue problem of the cable-STFD system by the finite difference method. This method also provides a tool for accurate determination of decay process and damping force. The results show that, for a cable-STFD system, the STFD produces a combined performance of friction damper and viscous damper. The features of either friction damper or viscous damper predominates at different stages of the decay process. The comparison also shows that, in general, the STFD is more effective on the mitigation of the stay cable vibration by comparing to the cable attached a viscous damper.

Real-time aerodynamics hybrid simulation: Wind-induced effects on a reduced-scale building equipped with full-scale dampers

As buildings are designed to be taller and more slender, they become lighter and more flexible with less inherent damping. If left uncontrolled, excessive wind-induced building response can cause serious safety and serviceability issues. Additional damping provided by adding an auxiliary damping system to the tall building is considered as one of the most cost-effective means to suppress the wind-induced response. Typically, the performance of these damping systems is evaluated experimentally with scaled damper and building models. However, the simplified small-scale dampers may not truly reflect the complex behavior of the full-scale damping systems. To realize the effective reduction of the wind-induced response of tall buildings, a real-time aerodynamics hybrid simulation (RTAHS) methodology that can offer improved response evaluation of a tall building integrated with an auxiliary damping system is introduced in this study. In this novel dynamic testing approach, the accurate evaluation of wind-induced tall building response is achieved by interacting an aeroelastic model of the tall building with the numerical model of the full-scale damper via interfacing actuators during the wind-tunnel tests. The feasibility and simulation accuracy of the proposed dynamic testing technique in the wind tunnel is numerically demonstrated by two case studies involving the wind-induced response reduction of a tall building equipped with both small-scale and full-scale damper properties.

Experimental and analytical study on design performance of full-scale viscoelastic dampers

Viscoelastic (VE) dampers, with their stiffness and energy dissipation capabilities, have been widely used in civil engineering for mitigating wind-induced vibration and seismic responses of structures, thus enhancing the comfort of residents and serviceability of equipment inside. In past relevant research, most analytical models for characterizing the mechanical behavior of VE dampers were verified by comparing their predictions with performance test results from small-scale specimens, which might not adequately or conservatively represent the actual behavior of full-scale dampers, especially with regard to the ambient temperature, temperature rise, and heat convection effects. Thus, in this study, by using a high-performance testing facility with a temperature control system, full-scale VE dampers were dynamically tested with different displacement amplitudes, excitation frequencies, and ambient temperatures. By comparing the analytical predictions with the experimental results, it is demonstrated that adopting the fractional derivative method together with considering the effects of excitation frequencies, ambient temperatures, temperature rises, softening, and hardening, can reproduce the design performance of full-scale VE dampers very well.

Full Scale Measurements and Theoretical Predictions of 2nd Order Pitch and Roll Slow Motions of a Semisubmersible Platform

In Oct. 2007, the semisubmersible platform PETROBRAS 52 (P-52) was installed in Campos Basin (Roncador Field) offshore Brazil, in a depth around 1800 m through 16 lines in taut-leg con. The maximum production capacity is 180.000 bpd with a displacement of 80,986t at the operational draft of 27.5 m. Slow drift motions in the vertical plane (heave, roll, and pitch) were observed in a model test performed in a wave basin during the design phase. As resonant responses vary considerably with the damping loads, slow motion could be affected by scale effects. To observe the phenomena, by that time, it was a doubt if this phenomenon would happen during the platform operation. Since June 2008, PETROBRAS has been monitoring P-52 motions with the use of accelerometers and rate-gyros. Through spectral analysis of the measured signals, it was possible to verify the presence of slow motions with frequencies around the natural frequencies of roll and pitch during almost the whole monitoring period. Sometimes, the 2nd order amplitudes were even greater than the 1st order ones. Furthermore, the environmental conditions have also been monitored through wave radars, ADCPS (current) and meteorological stations (wind) in the vicinity of P-52 location, making the excitation loads identification possible. A comparative study confronting full-scale measurements and theoretical predictions was performed. First and second-order forces and responses were calculated using Wamit® second order module. This study permitted the estimation of the full scale damping values of this offshore system (hull plus mooring and riser lines) for one of the environmental conditions measured. The results indicate the importance of considering the resonant roll and pitch motions in the seakeeping analysis of large-volume semisubmersible platforms, contributing with an important feedback to future designs.

248 実大粘弾性ダンパの温度依存性と温度管理の効果

Among many viscoelastic dampers, linear ones seem better than nonlinear ones, because it is quite easy to simulate linear behaviors by making use of a simple generalized Maxwell model. However, their mechanical properties are usually quite sensitive to environmental temperature. To get rid of this bad influence, we developed a temperature control system for the VED. This paper reports the scale effect of this system. First, by the random wave excitation experiments, the temperature dependent mechanical properties of the full-scale VED were examined. And second, by applying the temperature control system to the damper used for seismic retrofitting of an existing reinforced concrete building, the scale effect of this system was studied. In addition, the influence of the VED on dynamic characteristics was examined by means of the dynamic loading test on the full-scale damper that includes this system.

MR 유체 댐퍼의 동적모델을 고려한 사장교의 반(半)능동제어

본 논문에서는 미국토목학회(ASCE)의 사장교에 대한 첫번째 벤치마크 문제를 이용하여 제어-구조물 상호작용을 고려한 새로운 반능동제어 기법을 제안하였다. 이 벤치마크 문제에서는 2003년 완공 예정으로 미국 Missouri주에 건설 중인 Cape Girardeau 교를 대상 구조물로 고려하였다. Cape Girardeau 교는 New Madrid 지진구역에 위치하고, Mississippi 강을 횡단하는 주요 교량이라는 점 때문에 설계단계에서부터 내진 문제를 중요하게 고려하였다. 본 연구에서는 MR 유체 감쇠기를 제어 장치로 제안하였고, clipped-optimal 알고리듬을 제어 알고리듬으로 사용하였다. 또한, 대용량 MR 유체 감쇠기 실험 결과를 이용하여, Bingham 모델, Bouc-Wen 모델, 수정된 Bouc-HWen 모델과 같이 수치해석에 이용할 수 있는 다양한 동적 모델을 개발하였다. MR 유체 감쇠기는 제어가능한 에너지 소산장치이며 구조물에 에너지를 가하지 않기 때문에 제안된 제어기법은 한정입출력 안정성이 보장된다. 수치해석을 통해, MR 유체 감쇠기를 이용한 반능동제어 기법이 사장교의 응답 감소에 효과적인 방법임을 증명하였다. This paper examines the ASCE first generation benchmark problem for a seismically excited cable-stayed bridge, and proposes a new semi-active control strategy focusing on inclusion of effects of control-structure interaction. This benchmark problem focuses on a cable-stayed bridge in Cope Girardeau, Missouri, USA, for which construction is expected to be completed in 2003. Seismic considerations were strongly considered in the design of this bridge due to the location of the bridge in the New Madrid seismic zone and its critical role as a principal crossing of the Mississippi River. In this paper, magnetorheological(MR) fluid dampers are proposed as the supplemental damping devices, and a clipped-optimal control algorithm is employed. Several types of dynamic models for MR fluid dampers, such as a Bingham model, a Bouc-Wen model, and a modified Bouc-Wen model, are considered, which are obtained from data based on experimental results for full-scale dampers. Because the MR fluid damper is a controllable energy-dissipation device that cannot add mechanical energy to the structural system, the proposed control strategy is fail-safe in that bounded-input, bounded-output stability of the controlled structure is guaranteed. Numerical simulation results show that the performance of the proposed semi-active control strategy using MR fluid dampers is quite effective.

Experimental Characterization of Metallic Dampers for Seismic Retrofit of Highway Bridges

The seismic effectiveness of metallic dampers as vibration isolators and energy dissipation devices as well as the dynamic performance of high rocker bearings are investigated experimentally. The scope of the study includes optimizing the metallic dampers for maximum dissipation of energy, characterizing full-scale metallic dampers, and understanding the seismic behavior of a small-scale bridge with dampers. Three fullscale dampers, two of straight and one of linearly tapered rods, were fabricated and tested under a progressive cyclic load. Test results consistently show that the tangential stiffness of the metallic dampers does not degrade significantly as the number of loading cycles increases even though slack in the test fixture exists. For practical applications, a 10 percent damping ratio is recommended for the design of metallic dampers composed of straight rods, although a significantly higher ratio can be used for tapered dampers. Finally, a small-scale damper was fabricated and installed in an approximately one-tenth-scale steel-girder bridge model. The model was mounted on a shake table and tested under harmonic and earthquake loads. The test results indicated that the metallic damper is an effective isolator that can prevent energy transmission from the substructure to the superstructure of a bridge. They also show that high rocker bearings are stable even at the table acceleration of 0.54 g ( g =9.8 m/s2).

Some Practical Applications of Rubber Dampers for the Suppression of Torsional Vibrations in Engine Systems

The method of rubber damper design outlined in this paper has been developed owing to the breakdown on a number of occasions of the two-mass system method hitherto widely used. This new method, which is based on the study of the behaviour of the engine as a whole in conjunction with the damper, splits up the functioning of a damper into two parts, one conveniently called the detuning effect, and the other, the absorption effect. The first relies on the powerful tuning curve method, already described in the Proceedings, and the other is based on numerous painstaking trials and physical tests on rubber samples and on full-scale dampers. The method outlined shows that there is no rigid relationship between the frequencies of the engine and damper, and that the free end of the engine crankshaft is not the only place where a successful damper can be fitted. In addition to giving some particulars about physical and other properties of rubber, it also shows how to calculate the heat dissipated by dampers. Practical support for the theory is provided by accounts of vibration trials on three widely different types of engines with dampers fitted to them. In all cases, comparison of calculated and experimental amplitudes is given. The good agreement between the two cannot escape attention and shows that the method outlined can be used with confidence.