• Earthquakes and Structures
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• v.11 no.6
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• pp.983-1000
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• 2016

To date the engineering community has seen facade systems as non-structural elements with high aesthetic value and a barrier between the outdoor and indoor environments. The role of facades in energy use in a building has also been recognized and the industry is also witnessing the emergence of many energy efficient facade systems. This paper will focus on using exterior skin of the double skin facade system as a dissipative movable element during earthquake excitation. The main aim of this study is to investigate the potential of the facade system to act as a damper system to reduce earthquake-induced vibration of the primary structure. Unlike traditional mass dampers, which are usually placed at the top level of structures, the movable/smart double skin facade systems are distributed throughout the entire height of building structures. The outer skin is moveable and can act as a multi tuned mass dampers (MTMDs) that move and dissipate energy during strong earthquake motions. In this paper, using a three dimensional 10-storey building structure as the example, it is shown that with optimal choice of materials for stiffness and damping of brackets connecting the two skins, a substantial portion of earthquake induced vibration energy can be dissipated which leads to avoiding expensive ductile seismic designs. It is shown that the engineering demand parameters (EDPs) for a low-rise building structures subjected to moderate to severe earthquakes can be substantially reduced by introduction of a smart designed double skin system.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.144-153
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• 1998

Base isolation is an innovative design strategy that provides a practical alternative for the seismic design of structures. Base isolators, mainly employed to isolate large structures subjected to earthquake ground excitations and to rehabilitate structures damaged by past earthquakes, deflect and absorb the seismic energy horizontally transmitted to the structures. This study demonstrates that the base isolation system may offer effective performance for bridges during severe seismic events through shaking table tests. Two base isolation system using laminated rubber bearings with and without hydraulic dampers are tested. The test results strongly show that the laminated rubber bearings cause the natural period of the bridge structure increased considerably, which results in the deck acceleration and the shear forces on the piers reduced significantly. The results also demonstrate that the hydraulic dampers enhance the system's capacity in dissipating energy to reduce the relative displacement between the bridge deck and the pier.

• Smart Structures and Systems
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• v.6 no.7
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• pp.793-810
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• 2010

This paper addresses the control issue of vibratory MEMS-based gyroscopes. This study considers a gyroscope that can be modeled by an inner mass attached to an outer mass by four springs and four dampers. The outer mass itself is attached to the rotating frame by an equal number of springs and dampers. In order to measure the angular rate of the rotating frame, a driving force is applied to the inner mass and the Coriolis force is sensed along the y-direction associated with the outer mass. Due to micro-fabrication imperfections, including anisoelasticity and damping effects, both gyroscopes do not allow accurate measurements, and therefore, it becomes necessary to devise feedback controllers to reduce the effects of such imperfections. Given an ideal gyroscope that meets certain performance specifications, a feedback control strategy is synthesized to reduce the error dynamics between the actual and ideal gyroscopes. For a dual-mass gyroscope, it is demonstrated that the error dynamics are remarkably decreased with the application of four actuators applied to both masses in the x and y directions. It is also shown that it is possible to reduce the error dynamics with only two actuators applied to the outer mass only. Simulation results are presented to prove the efficiency of the proposed control design.

• Journal of Power System Engineering
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• v.10 no.1
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• pp.96-101
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• 2006

In ship operation the consequence of roll and pitchingmotion can seriously degrade the performance of mechanical and personnel effectiveness. So many studies for the roll stabilization and trimming control system design have been performed and good results have been achieved where the stabilizing fins, tanks, rudders and flaps are used. However the ultimate objective of such approach should be focused on improving the boarding sensitivity. But there may exist many unsolved problems, for examples, ship control performance degradation and increasing of system complexity. So, the achieved control performance could not give us enough comfortable boarding sensitivity where the residual rolling and pitching motion are main drawbacks. To get rid of these disadvantages, the main hull control systems design approach has been considered using semiactive absorber. In this system, dampers, spring, dynamic dampers and control system with sensors are incorporated. In our system considered in this study, just two motors and control system with sensors are used for the bed. And the control system can be installed on each bed. So, we can control every bed on the specified control objective respectively. Above all, the good advantages of this system are the facts followed from simple idea and usefulness. Of course the structural modifications are needed. Considering disturbances, we design control system and verify the usefulness of developed system from the experimental study.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.432-439
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• 2006

Long span, high-rise bridges are rapidly increasing nowadays. Because of high flexibility, such bridges are easily excited by winds, vehicles, and pedestrians. The vibration of bridge induces a vibration of lamp post and pillar. Wind loads can also excite lamp posts and traffic signal structures directly. Because of low damping, such vibrations of lamp post are frequently amplified and come to collapse or lamp failure. In addition, such vibration makes the maintenance cycle shorter and increases social cost. We conducted vibration tests and identified the dynamic characteristics of two types lamp posts, and proposed tuned mass dampers to control the vibrations. Established models of the lamp posts present the dynamic characteristics of the structures very well and they are used to design TMDs. In this study, we suggested a new-type TMD model that is small, simple, economic and effective to suppress the vibration of lamp posts. The efficiency of TMD was examined by numerically and is to be examined experimentally.

• Smart Structures and Systems
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• v.24 no.5
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• pp.641-648
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• 2019

The authors investigate the feasibility of applying a vision-based displacement-measurement technique in the characterization of a SMA damper recently introduced in the literature. The experimental campaign tests a steel frame on a uni-axial shaking table driven by sinusoidal signals in the frequency range from 1Hz to 5Hz. Three different cameras are used to collect the images, namely an industrial camera and two commercial smartphones. The achieved results are compared. The camera showing the better performance is then used to test the same frame after its base isolation. U-shaped, shape-memory-alloy (SMA) elements are installed as dampers at the isolation level. The accelerations of the shaking table and those of the frame basement are measured by accelerometers. A system of markers is glued on these system components, as well as along the U-shaped elements serving as dampers. The different phases of the test are discussed, in the attempt to obtain as much possible information on the behavior of the SMA elements. Several tests were carried out until the thinner U-shaped element went to failure.

• Steel and Composite Structures
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• v.49 no.3
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• pp.257-270
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• 2023

In this study, the feasibility and applicability of a friction damper with a vertical installation scheme are investigated. This device is composed of a steel section and two friction hinges at both ends which dissipate seismic energy. Due to its small width and vertical installation scheme, the proposed damper can minimize the interference with architectural functions. To evaluate the performance of the proposed damper, its mechanical behavior is theoretically evaluated and the required formulas for the yield strength and elastic stiffness are derived. The theoretical formulas are verified by establishing the analytical model of the damper in the SAP2000 software and comparing their results. To further investigate the performance of the developed damper, the provided analytical model is applied to a 4-story reinforced concrete (RC) structure and its performance is evaluated before and after retrofit under the Maximum Considered Earthquake (MCE) hazard level. The seismic performance is thoroughly evaluated in terms of maximum interstory drift ratio, displacement time history, residual displacement, and energy dissipation. The results show that the proposed damper can be efficiently used to protect the structure against seismic loads.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.3 s.55
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• pp.53-62
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• 2007

This paper presents a new vibration control method for long-span bridges using complex damper system. The new system presents simple mechanical configuration with oil and elasto-plastic dampers which have velocity and displacement dependency in vibration energy absorbing. This system can produce various damping forces according to the applied external forces by the velocity and displacement-dependent characteristics of the dampers. The oil damper dissipates vibration energy for relatively frequent and small amplitude like in the case for small to moderate earthquakes, whereas the elasto-plastic damper system works for rare and large amplitude vibration such as high seismic excitation. Thus, the proposed system exhibits the advantage of low cost with high performance since the roles of the two different dampers are effectively separated. A numerical model is established for the complex damper system, and the response characteristics and effectiveness of the proposed system are presented through numerical simulations. Numerical results show that the proposed complex damper system can significantly improve the seismic performance of long-span bridge structures with much more effective damping mechanism than single conventional passive damper systems.

• Tribology and Lubricants
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• v.16 no.1
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• pp.27-32
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• 2000

This paper describes that the leaf spring damper (LSD) developed by authors can be controled by side clearance between side covers and leaf springs. The test rig and two prototype dampers with different side clearance were manufactured. Experiments were performed to investigate the effects of side clearance on the damping of the leaf spring damper. The stiffness and damping coefficients are obtained from the displacements and the reaction forces generated by rotating the eccentric shaft. All dynamic coefficients are plotted with the excitation frequency which is adjusted by rotating speed of the shaft.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.188-195
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• 1998

The main objective of this study is to observe the effect of visco-elastic damper on seismic behavior of structure. A small shaking table was designed and manufactured using the materials and machinery available in the market by the authors. Also, two small-scale models with and without visco-elastic dampers were made. Dynamic characteristics, such as natural periods and damping ratios, were measured with free vibration tests. Finally, the earthquake simulations tests by using this shaking table were performed to these models. Based on the test results, the effect of visco-elastic damper on the seismic response of models is evaluated.