Oil Damper Research Articles

NUMERICAL INVESTIGATION OF DYNAMIC RESPONSE CHARACTERISTIC OF DAMPED BRACED TUBE SYSTEM WITH DIFFERENT DAMPED SLIT COMFIGURATION

This paper investigated the dynamic response characteristic with focus on damped slit configuration of damped braced tube systems with oil dampers. According to the results, 1) damped braced tube system has over 10% 1st to 3rd damping ratio, 2) while the displacement and acceleration responses are simultaneously reduced up to maximized 1st mode damping ratio, the acceleration reduction effect may be getting worse after the peak, 3) while uniform damper distribution contributes to better damping performance, centralized damper distribution contributes to better period reduction.

Study on the correlation between combustion status and block vibration induced by piston slap

The correlation between the combustion status and block vibration was studied at different engine speed, torque and oil temperature conditions. The frequency components lower than 8 kHz had a similar change trend with the peak value of combustion pressure at different speed conditions. The frequency components from 8 kHz to 25 kHz increased with engine speed and these frequency components were mainly affected by the inertia force. The spectrum energy of frequency components increased with engine torque due to the increase of combustion pressure. The maximum spectrum energy of frequency components below 20 kHz didn’t show a particular trend due to the opposite effects caused by combustion pressure and oil damping at different oil temperatures. The frequency components higher than 20 kHz increased with the increase of oil temperature, which meant the frequency components were more sensitive to the oil damping.

Reliability Analysis of Response-Controlled Buildings Using Fragility Curves

The number of buildings with passive control systems is steadily growing worldwide. For this reason, this study focuses on the reliability analysis of these systems employing fragility curves. The structural performance evaluation is obtained for a 10-story steel building with two different sections (trimmed and conventional). The trimmed section of the building was evaluated with hysteresis and oil dampers, while the conventional section of the building was evaluated without damper. The fragility curves were obtained from the incremental dynamic analysis using 20 ground motion records. Spectral acceleration response at the fundamental period of the building was considered and used as the intensity measure for the ground motion records. The maximum inter-story drift ratio of the building was employed as the damage measure. In addition, the seismic energy absorption rate was compared between hysteresis and oil dampers. As a result, hysteresis dampers were found to be more effective for high ground motion intensities. On the other hand, the oil damper dissipates energy immediately, even for low ground motion intensities. Furthermore, the combination of different types of dampers improved the seismic performance of the trimmed section of the building to almost the same level as the conventional section of the building. Eventually, a combination of hysteresis and oil dampers in a building is suggested to improve structural performance.

Therapeutic effect of gait training with two types of ankle-foot orthoses on the gait of the stroke patients in the recovery phase.

Objectives This study aimed to demonstrate the therapeutic effect of gait training using ankle-foot orthoses (AFOs) on the gait of stroke patients when not wearing AFOs with two different types of AFO, an AFO with an oil damper (AFO-OD) that resists plantarflexion and an AFO with a plantarflexion stop (AFO-PS), and to display the possible differences between the AFO types. Patients and methods Forty-two patients (38 males, 4 males, mean age: 59.7±10.9; range, 38 to 81 years) with subacute stroke were randomized to either an AFO-PS or an AFO-OD group. Participants were given gait training in a two-week period by physiotherapists wearing their allocated AFO. Nineteen patients were assigned to the AFO-PS group and 20 to the AFO-OD group. Patients' gait without an AFO before gait training and then after two weeks of training wearing allocated AFOs was recorded through a three-dimensional movement capture system. Results A therapeutic effect through two weeks of continuous use of AFOs and gait training was found in both AFO groups (main effect of time) in the spatiotemporal factors, ankle joint moments, ankle power generation, shank-to-vertical angle, and center of gravity velocity throughout the stance phase, pre-swing knee angular velocity, and hip flexion moment in pre-swing. The results did not show a large interaction between two AFOs group. Conclusion These findings reveal that both AFOs had significant therapeutic effects on stroke gait. There was no significant difference between the two AFO groups. Further studies with a control group representing the effects of gait training without wearing an AFO are needed.

Ankle–foot orthosis with an oil damper versus nonarticulated ankle–foot orthosis in the gait of patients with subacute stroke: a randomized controlled trial

BackgroundGait improvement in patients with stroke has been examined in terms of use or non-use of an ankle–foot orthosis (AFO), but the effects of different kinds of AFOs remain unclear. In this study, the effect on gait of using an AFO with an oil damper (AFO-OD), which has plantarflexion stiffness without dorsiflexion resistance, was compared with a nonarticulated AFO, which has both dorsiflexion and plantarflexion stiffness, in a randomized controlled trial.MethodsForty-one patients (31 men, 10 women; mean age 58.4 ± 11.3 years) in the subacute phase of stroke were randomly allocated to two groups to undergo gait training for 1 h daily over 2 weeks by physiotherapists while wearing an AFO-OD or a nonarticulated AFO. A motion capture system was utilized to measure shod gait without orthosis at baseline and after training with the allocated AFO. Data analysis focused on the joint kinematics and kinetics, spatial and temporal parameters, ground reaction force, and shank-to-vertical angle. Unpaired t-test or Mann–Whitney U test was performed to clarify the difference in gait with an AFO between the two AFO groups after training, with a significance level of p = 0.05.ResultsThirty-six patients completed the study (17 in the AFO-OD group and 19 in the nonarticulated AFO group). The ankle joint was more dorsiflexed in single stance (p = 0.008, effect size r = 0.46) and peak ankle power absorption was larger in stance (p = 0.007, r = 0.55) in the AFO-OD group compared with the nonarticulated AFO group. Peak power absorption varied among patients in the AFO-OD group. Increased dorsiflexion angles were also found at initial contact (p = 0.008, r = 1.51), pre-swing (p = 0.045, r = 0.91), and the swing phase (p = 0.045, r = 0.91) in the AFO-OD group. There was no difference in peak plantarflexion moment, ankle power generation, spatial or temporal parameters, ground reaction force, or shank-to-vertical angle between the two groups.ConclusionsThe results of this study showed that an AFO with plantarflexion stiffness but without dorsiflexion resistance produced greater improvement in ankle joint kinematics and kinetics compared with the nonarticulated AFO, but the results of peak power absorption varied greatly among patients.Trial registration UMIN000028126, Registered 1 August 2017, https://upload.umin.ac.jp/cgi-bin/icdr/ctr_menu_form_reg.cgi?recptno=R000032197

A comparative study of seismic analysis, design, and collapse safety margins of tall buildings in the United States and Japan: Part II: comparison of seismic capacity and collapse safety margin

This is an extension of the companion paper (Part 1) that presents the details of the two buildings located in Tokyo and designed using the US Performance Based Seismic Design (PBSD) methodology for one building (US Prototype Building) and the Japanese PBSD methodology for the other (Japan Prototype Building). The paper presents the IDA results and associated discussion on the collapse safety margin and the damage progress of the major structural elements. The Japan Prototype Building made of steel moment-resisting frames equipped with oil dampers is 1.5 times stronger in terms of the collapse safety margin than the US Prototype Building made of an reinforced concrete (RC) core shear wall system. The difference between the two buildings is believed to occur because of the larger redundancy and resultant larger over-strength achieved by the Japan Prototype Building. It is noteworthy that the construction cost of the Japan Prototype Building is about 30% higher than the US Prototype Building as indicated in Part 1. To explain the behavioral difference, sequences, and progresses of damage to major structural members are characterized in reference to the fragility curves of respective members. The benefits of oil dampers are found that the addition of the oil dampers would increase the collapse safety margin by 29% with an extra construction cost of 3%.

A comparative study of seismic analysis, design, and collapse safety margins of tall buildings in the United States and Japan, Part I: Performance-based analysis and design

Performance-based seismic analysis and design of tall buildings have become increasingly common in the United States and have been the standard practice in Japan for a long time. The methodologies for seismic hazard analyses, selection of earthquake records for design, and acceptance criteria, however, are widely different in the two countries. Japan experiences large earthquakes and strong shakings of buildings significantly more frequently than the United States, and the data on actual seismic performance are richer in Japan than in the United States. Comparison of performance and calibration between the two design procedures can help to improve the quantitative assessment of seismic performance of buildings in the United States. This article presents the application of US and Japanese procedures to a tall building archetype once proportioned, analyzed, and designed according to US practices and once per Japanese practices. The structural systems selected are very different; for the United States, the archetype is designed using a core reinforced concrete shear wall building with composite floor systems and steel columns as the gravity system, whereas for Japan, the archetype is designed using a steel moment frame made of square concrete-filled steel tube (CFT) columns and composite beams and installed with oil dampers. Although the design procedures followed are vastly different, the seismic performances of the systems are rather similar during serviceability, design basis, and maximum considered events. As will be presented in the second part of this article, the collapse safety margins of the two designs are significantly different.

A novel damped braced tube system for tall buildings in high seismic zones

SummaryThe damped outrigger system is known to efficiently provide additional damping in buildings with heights of over 250 m. However, particularly for supertall buildings in the center of Tokyo, Japan, the outrigger truss from the center core to the exterior columns need to span distances of more than 20 m. This increases the flexural stiffness demand on the outrigger that leads to larger truss depths making the damped outrigger system inefficient. For such tall buildings with large plans, a new damping modification system, the “damped braced tube system” is proposed, where the exterior surface of the elastic mega braces are partially removed vertically to create a split and are replaced with dissipaters (energy‐dissipation devices). The damped braced tube system enhances the seismic performance as the exterior surfaces of the elastic mega braces work together with the damped slits like in a coupled wall system and increases the overall damping ratio. In this paper, numerical models were constructed based on a real project in Japan consisting of a 397‐m supertall building employing the damped tubular braced system using oil dampers (referred to as viscous dissipaters). A series of generalized response spectrum based numerical analyses and optimizations were performed to minimize the seismic response. The proposed system exhibited improved damping performance with the first to third mode damping ratios reaching to more than 7% while providing a wide range of options for dissipater distribution for design. Finally, the elevation of the slit's base is recommended to be equal to 0.22 of the total building height considering the trade‐off relationship between the first modal damping ratio and the fundamental period.

Semi-Active Cable Damping to Compensate for Damping Losses Due to Reduced Cable Motion Close to Cable Anchor

The relative motion of transverse cable dampers is smaller than predicted by the taut string model because of the effects of bending stiffness and fixed support conditions. As a result of the reduced damper motion, the dissipated energy per cycle is reduced as well, which may explain why damping measurements on real stay cables with transverse dampers often show lower cable damping ratios than expected from the taut string theory. To compensate for the reduced damper motion and damper efficiency, respectively, a semi-active cable damper is proposed. The controllable damper is realized by a hydraulic oil damper with real-time controlled bypass valve whereby the resulting damper force is purely dissipative. The proposed control law is clipped viscous damping with negative stiffness. The viscous coefficient is adjusted in real time to the actual frequency of vibration to generate optimum modal damping while the negative stiffness component partially compensates for the reduced damper motion due to the flexural rigidity and fixed support conditions of the cable. The measurements of the prototype semi-active hydraulic damper are used to derive a precise model of the semi-active damper force including the control force constraints due to the fully open and fully closed bypass valve. This model is used to compute the cable damping ratios of the first four cable modes, for typical damper positions, for a taut string model and for a cable model with flexural rigidity and fixed supported ends. The obtained cable damping ratios are compared to those resulting from the passive linear viscous damper being optimized to the first four cable modes. The results demonstrate that the proposed semi-active cable damper with the consideration of the minimum and maximum control force constraints significantly enhances the cable damping of the first four modes compared to the linear viscous damper.

Research and Development of Three-Dimensional Isolation System for SFR

The development of a SFR(:Sodium-cooled Fast Reactor) is carried out by Japan Atomic Energy Agency and others. Not only the decrease of horizontal seismic loads, but also the decrease of vertical seismic loads is important in SFR which has thin wall structures. Accordingly, the three-dimensional isolation system is developed for the seismic design of the components. This isolation device consists of a thick rubber bearing, four coned disc spring units, four vertical oil dampers, eight sliding functions and a supporting function. Furthermore, horizontal oil dampers are installed for damping force. This isolation device has few critical development elements and no additional function such as the rocking suppression device. In this isolation system, the natural frequency in the horizontal direction is 0.29Hz, the natural frequency in the vertical direction is 3.0 Hz. This isolation device is premeditatedly developed from 2017. This project has carried out load tests with full and half scale coned disc springs. The design method of coned disc spring units has been confirmed. Furthermore, this project has developed the horizontal oil damper of high allowable velocity and the vertical oil damper. This project is carrying out load tests of the half scale three-dimensional seismic isolation device, which consist of the thick rubber bearing, the coned disc spring units, the supporting function and so on. The development of this isolation device will be continued sequentially. The fundamental design method of this isolation device is confirmed in this project.

Optimization of tuned rolling-cylinder dampers using particle swarm optimization

Tuned mass dampers (TMDs), which consist of an added mass and a spring/oil damper, are often installed to damp equipment and structures because they are compact and lightweight. However, there are some problems such as performance degradation due to age-related deterioration of springs and oil dampers. A tuned rolling-cylinder damper (TRCD), which does not use a spring or oil damper, has been proposed, which consists of an arc-shaped main vibration body and multiple rolling elements. The TRCD is simple in structure and is easy to install and durable. However, the combination of parameters such as the radius of the arc vessel, the number of rolling elements, and the radius to obtain the optimum damping performance has not been fully investigated. In this paper, an optimization of the TRCD was performed using an optimization technique called the Particle Swarm Optimization (PSO), and the validity was verified experimentally. In addition, the Distinct Element Method (DEM) was used to analyze the contact forces between rolling elements and between rolling elements and arc containers．

Development of dynamic behavior model for damping characteristics of suspension for automobiles

The suspension for automobiles reduces the vibrations transmitted from the road surface to the vehicle body, which improves vehicle dynamic performance and ride comfort, springs to the shock absorber as the main structure, and oil damper is widely employed in the vibration damping portion. In recent years, in response to the problem of reducing the noise in the car which is called rattle noise, evaluation is required including transient attenuation characteristics of the damper. We construct a damping force characteristic analysis model which considers the transient response of a damper in the car noise prediction system using the 1D model, and the evaluation of transient damping force response near the open operation using this model was obtained.

Simulation and Analysis of Bistatic Radar Scattering From Oil-Covered Sea Surface

In this study, the bistatic radar scattering coefficients related to an oil-covered sea surface are predicted by modeling both the oil damping effect on surface roughness–through the advanced integral equation method–and the oil modification on the dielectric properties of the scattering surface. The bistatic scattering is analyzed in the whole upper scattering space under different radar frequencies, incidence angles, wind speeds, and oil thicknesses. Numerical predictions show that the scattering energy of an oil-covered sea surface is generally higher in the forward scattering zone than that in the backward one. In addition, the oil damping effect is the main mechanism ruling the scattering behavior in the backward region. The information related to the bistatic scattering geometry is also explored to retrieve oil thickness, representing one of the key parameters for radar-based marine oil pollution observation. A new index is proposed to quantify the sensitivity of bistatic scattering coefficients to oil thickness in different cases: single-polarization features, dual co-polarization features, namely, the polarization ratio (PR) and the normalized polarization difference index (NPDI), and dual-angular scattering features. Numerical results show that the bistatic scattering coefficients result in an enhanced sensitivity to oil thickness with respect to the monostatic case. The single HH-polarized scattering coefficients show better oil thickness sensitivity in the backward region, while the VV-polarized ones are more sensitive to oil thickness in the forward region. The combination of dual-polarized scattering coefficients significantly improves the oil thickness sensitivity compared to single-polarization radar observations, especially in the forward region. PR outperforms NPDI, even though the latter can suppress the effect of wind speed. The combination of dual-angular observations can significantly increase its sensitivity of oil thickness in the backward region but at the expense of reduced sensitivity in the forward region.

Global Simultaneous Optimization of Oil, Hysteretic and Inertial Dampers Using Real-Valued Genetic Algorithm and Local Search

A method for global simultaneous optimization of oil, hysteretic and inertial dampers is proposed for building structures using a real-valued genetic algorithm and local search. Oil dampers has the property that they can reduce both displacement and acceleration without significant change of natural frequencies and hysteretic dampers possess the characteristic that they can absorb energy efficiently and reduce displacement effectively in compensation for the increase of acceleration. On the other hand, inertial dampers can change (prolong) the natural periods with negative stiffness and reduce the effective input and the maximum acceleration in compensation for the increase of deformation. By using the proposed simultaneous optimization method, structural designers can select the best choice of these three dampers from the viewpoints of cost and performance indices (displacement, acceleration). For attaining the global optimal solution which cannot be attained by the conventional sensitivity-based approach, a method including a real-valued genetic algorithm and local search is devised. In the first stage, a real-valued genetic algorithm is used for searching an approximate global optimal solution. Then a local search procedure is activated for enhancing the optimal character of the solutions by reducing the total quantity of three types of dampers. It is demonstrated that a better design from the viewpoint of global optimality can be obtained by the proposed method and the preference of damper selection strongly depends on the design target (displacement, acceleration). Finally, a multi-objective optimization for the minimum deformation and acceleration is investigated.

Theoretical Investigation on the Impact of Two HDR Dampers on First Modal Damping Ratio of Stay Cable

Stay cables are one of the vital components of a cable-stayed bridge. Due to their flexible nature, stay cables are vulnerable to external excitation and often vibrate with large amplitude under wind action which leads to the fatigue failure of the cables. To suppress such kind of large amplitude vibration by improving the damping ratio of the cable various dampers such as magnetorheological damper, friction damper; oil damper; or high damping rubber (HDR) damper are utilized and gained popularity over time. This paper focuses on improving the damping ratio of stay cables using a combination of two HDR dampers. First, the theoretical model is formulated considering cable bending stiffness to evaluate the damping effect of cable-HDR dampers system. Then, the impact of various design parameters of HDR dampers on cable damping considering the cable stiffness is performed. The comparative analysis of results shows that the considered parameters such as loss factor, spring factor, and installation location of dampers have much effect on the stay cables damping ratio. Finally, the optimal parameters of the two HDR dampers are proposed for damper design.

Research on the Contact Bounce During the Closing Process of a Repulsion Mechanism Applied in a Superconductivity Direct-Current Vacuum Circuit Breaker

This paper studies the contact bounce during the closing process of a repulsion mechanism applied in a superconductivity direct-current vacuum circuit breaker. A multi-physics field coupling simulation model is established to describe the whole closing process for the repulsion mechanism. The relationship between the V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> is obtained for the repulsion mechanism, where the V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> is an instantaneous closing velocity for the movable contact just mating with the stationary contact at the first time, and the D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> is the maximum contact bounce distance. According to this relationship, the critical instantaneous closing velocity V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cri</sub> for the case of no contact bounce is determined. According to V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cri</sub> , a novel oil buffer is designed to adjust the closing displacement of the repulsion mechanism to realize a nonclosing bounce. A prototype repulsion mechanism with an oil damper is developed. Its closing characteristics are tested and compared with the simulation results to verify the absence of a contact bounce.

Impact of Alternate Gait Training Using Knee-Ankle-Foot Orthoses with Oil Damper Ankle Hinge in Patients with Subacute Severe Hemiplegia.

Patients with severe hemiplegia along with knee instability require knee–ankle–foot orthoses (KAFOs) for gait training. However, in these patients, it is unclear which type of walking training is more effective to improve gait function. Providing alternate gait training (AGT) improves walking function in patients with spinal cord injury, but it is still unclear whether this is effective in hemiplegic stroke patients. In this study, we defined “unified AGT” as AGT performed with the same therapeutic concept by physiotherapists. We then investigated whether AGT improved gait function quicker than our traditional gait training in hemiplegic stroke patients. We enrolled 15 subjects with severe hemiplegia and knee instability who had undergone unified AGT using KAFOs with hinged oil dampers at the ankles, and 30 historical control (HC) subjects who had undergone traditional gait training. We used multiple comparison and survival analyses to analyze the differences in the functional independence measure (FIM) gait score changes between the two groups. The multiple comparison revealed a significant increase (p < 0.05) in the FIM gait score compared with its initial score in the subjects with unified AGT. However, this improvement was not seen in the HC subjects. Additionally, the survival analysis of time taken to recover revealed a significant difference between the subjects with unified AGT and HC subjects (p < 0.05). These findings suggest that unified AGT using a KAFO facilitates gait improvement in patients with severe hemiplegia and knee instability.

Influencing kinetic energy using ankle-foot orthoses to help improve walking after stroke: a pilot study.

An ankle-foot orthosis with an oil damper (AFO-OD) may improve kinetics and kinematics for efficient walking after stroke. Yet it is unknown whether hemiplegic walking behaves like "inverted-pendulum" gait and how it is modulated by using AFO-ODs for efficiency. This study examined whether the use of AFO-ODs improves the kinetics of total vertical ground reaction force (vGRF) and kinematics of vertical pelvic displacement (vPD) in different walking phases, and gait speed following stroke. Also, the relationship between those gait parameters was examined to assess efficient walking. Observational study within subject. Eight participants with hemiplegia walked at self-selected speed without and with AFO-ODs over the walkway and gait speed was measured. Force plates were used to measure total vGRF during the double-limb support phase with the paretic leading limb and with the paretic trailing limb (DSPT). The vPD in the paretic and nonparetic stance phases was measured by a three-dimensional motion analysis system. Without AFO-ODs, reduced total vGRF during DSPT was related to greater vPD in the subsequent nonparetic stance. Using AFO-ODs significantly increased gait speed and total vGRF during double-limb support phase with the paretic leading limb and during DSPT, which were significantly correlated. Vertical pelvic displacement in the nonparetic stance was higher than the paretic stance in both conditions. Decreased total vGRF during DSPT was compensated by excessive vPD in the nonparetic stance phase without AFO-ODs, indicating inefficient walking. However, the use of AFO-ODs improved the kinetic energy of total vGRF during the double-limb support phase, contributing to efficient walking. The AFO-ODs can be used to improve kinetic energy and to modulate functions in the weight transition during the double-limb support phase, with faster walking speed. Thus, AFO-ODs can be considered to be therapeutic AFOs to acquire efficient walking performance in poststroke rehabilitation.

Моделирование динамического воздействия авиационного двигателя на крыло самолета при отрыве лопатки вентилятора

One of the requirements for a projected aircraft is the ability to continue flying and land in the event of a breakdown of one of the engines. One of the calculated cases of engine breakdown is a fan blade breakaway. This phenomenon causes large vibrations of both the engine itself and the aircraft structure.Design model and method for studying engine vibrations with damage in the form of blade breakaway have been developed; numerical studies of unsteady vibrations of an engine suspended on a pylon have been carried out. Herewith, the following load options are considered: engine operation with fan imbalance before shutdown, which is performed by the pilot; sharp braking and jamming of the fan rotor as a result of breakage of the front elastic support of the rotor, which can occur when the blade breaks off; braking the rotor after turning off the engine.The front bearing of the rotor is ball the bearing installed in elastic elements "squirrel wheel". The ball bearing is modeled as a rigid joint. Outside the elastic element, there are two thin-walled shells, which are intermediate load-bearing elements. With an increase in the imbalance of the fan rotor, the gap in the oil damper closes, the damper housing sits on the shells, switching on their rigidity to work. Thus, the stiffness characteristic of the support is bilinear. The stiffness coefficients of the elastic element "squirrel wheel" and the front support shells are determined by the method of numerical simulation. The fan rotor is modeled as a solid body on bearing supports. The stator of the engine is modeled by a rigid body on an elastic suspension. The pylon and the elastic engine mount elements are modeled by beams of variable cross-section operating simultaneously in tension, torsion and bending.A numerical analysis of the transient vibration processes of the D-436-148FM engine on the pylon of the An-178 airplane is carried out. The most dangerous case of damage as the breakdown of the bearing support after the fan blade breakaway is investigated. The results of the calculations are the graphs of the forces in the bearing arrangements and in the hinges of the engine mounting depended on time.

Robust Optimal Damper Placement of Nonlinear Oil Dampers With Uncertainty Using Critical Double Impulse

A new robust method for optimal damper placement is presented for building structures under the critical double impulse. Oil dampers are treated here as representative supplemental dampers to control the seismic response of high-rise buildings. Such oil dampers usually obey a bi-linear force-velocity relation in controlling the maximum damping force through a relief mechanism to avoid the occurrence of excessive design forces in surrounding frames. The influence of uncertainty in characteristics of those bi-linear oil dampers on building structural safety is investigated. For the efficient evaluation of dynamic performance, the resonant critical double impulse is used as the base input instead of actual earthquake ground motions. Since the critical double impulse is determined to maximize the input energy to the objective building by changing the second impulse timing, uncertainties in input ground motions can be taken into account in a robust manner. To consider these various uncertainties, the robustness function based on the Info-Gap model is used in the robust optimization to assess structural performance variations caused by various uncertainties in the structural design phase. In this paper, a new innovative objective function in the robust optimal damper placement problem is proposed to enhance the robustness of structural performance under the variation of structural parameters by comparing the robustness function of the robust design with that of an ordinary optimal damper placement without considering uncertainties. Numerical examples of the robust optimal design of linear and bi-linear oil damper placements are shown for 10-story and 20-story planar building frame models. Structural performances of the robust optimal design to the conventional design earthquake ground motions are examined to investigate the validity of using the critical double impulse in the structural design under uncertainties.