• Structural Engineering and Mechanics
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• 제82권4호
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• pp.417-434
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• 2022

In this work, a review of mechanical metamaterials and seismic protection systems that use them is carried out, focusing on passive protection systems. During the last years, a wide variety of classical systems of seismic protection have demonstrated to be an effective and practical way of reducing the seismic vulnerability of buildings, maintaining their health and structural integrity. However, with the emergence of metamaterials, which allow obtaining uncommon mechanical properties, new procedures and devices with high performance have been developed, reducing the seismic risk through novel approaches such as: seismic shields and the redirection of seismic waves; the use of stop band gaps and the construction of buried mass resonators; the design of pentamodal base isolators. These ideas are impacting traditional areas of structural engineering such as the design and building of highly efficient base isolation systems. In this work, recent advances in new seismic protection technologies and researches that integrate mechanical metamaterials are presented. A complete bibliometric analysis was carried out to identify and classify relevant authors and works related with passive seismic protection system based on mechanical metamaterial (pSPSmMMs). Finally, possible future scenarios for study and development of seismic isolators based on mechanical metamaterials are shown, identifying the relevant topics that have not yet been explored, as well as those with the greatest potential for future application.

• Geomechanics and Engineering
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• 제7권3호
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• pp.263-277
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• 2014

In the conventional design of retaining structures in a seismic zone, seismic inertia forces are commonly assumed to act upwards and towards the wall facing to cause a maximum active thrust or act upwards and towards the backfill to cause a minimum passive resistance. However, under certain circumstances this design approach might underestimate the dynamic active thrust or overestimate the dynamic passive resistance acting on a rigid retaining structure. In this study, a new analytical method for dynamic active and passive forces in c-${\phi}$ soils with an infinite slope was proposed based on the Rankine earth pressure theory and the Mohr-Coulomb yield criterion, to investigate the influence of seismic inertia force directions on the total active and passive forces. Four combinations of seismic acceleration with both vertical (upwards or downwards) and horizontal (towards the wall or backfill) directions, were considered. A series of dimensionless dynamic active and passive force charts were developed to evaluate the key influence factors, such as backfill inclination ${\beta}$, dimensionless cohesion $c/{\gamma}H$, friction angle ${\phi}$, horizontal and vertical seismic coefficients, $k _h$ and $k_v$. A comparative study shows that a combination of downward and towards-the-wall seismic inertia forces causes a maximum active thrust while a combination of upward and towards-the-wall seismic inertia forces causes a minimum passive resistance. This finding is recommended for use in the design of retaining structures in a seismic zone.

• Smart Structures and Systems
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• 제3권3호
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• pp.385-403
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• 2007

The effectiveness of the newly developed smart passive control system employing a magnetorheological (MR) damper and an electromagnetic induction (EMI) part for seismic protection of base isolated structures is numerically investigated. An EMI part in the system consists of a permanent magnet and a coil, which changes the kinetic energy of the deformation of an MR damper into the electric energy (i.e. the induced current) according to the Faraday's law of electromagnetic induction. In the smart passive control system, the damping characteristics of an MR damper are varied with the current input generated from an EMI part. Hence, it does not need any control system consisting of sensors, a controller and an external power source. This makes the system much simpler as well as more economic. To verify the efficacy of the smart passive control system, a series of numerical simulations are carried out by considering the benchmark base isolated structure control problems. The numerical simulation results show that the smart passive control system has the comparable control performance to the conventional MR damper-based semiactive control system. Therefore, the smart passive control system could be considered as one of the promising control devices for seismic protection of seismically excited base isolated structures.

• Earthquakes and Structures
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• 제9권3호
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• pp.563-576
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• 2015

Over the past few decades, seismic retrofitting of structural systems has been significantly improved by the adoption of various methods such as FRP composite wraps, base isolation systems, and passive/active damper control systems. In parallel with this trend, probabilistic risk assessment (PRA) for structural and nonstructural components has become necessary for risk mitigation and the achievement of reliable designs in performance-based earthquake engineering. The primary objective of the present study was to evaluate the effect on piping fragility at T-joints due to seismic retrofitting of structural systems with passive energy-dissipation devices (i.e., linear viscous dampers). Three mid-rise building types were considered: without any seismic retrofitting; with distributed damper systems; with optimal placement of dampers. The results showed that the probability of piping system failure was considerably reduced in a Multi Degree of Freedom (MDOF) building retrofitted with optimal passive damper systems at lower floor levels. This effect of damper systems on piping fragility became insignificant as the floor level increased.

• Smart Structures and Systems
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• 제8권3호
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• pp.239-252
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• 2011

In this study, the performances of a passive tuned mass damper (TMD) and a semi-active TMD (STMD) were evaluated in terms of seismic response control of elastic and inelastic structures under seismic loads. First, elastic displacement spectra were obtained for damped structures with a passive TMD and with a STMD proposed in this study. The displacement spectra confirmed that the STMD provided much better control performance than passive TMD and the STMD had less stroke requirement. Also, the robustness of the TMD was evaluated by off-tuning the frequency of the TMD to that of the structure. Finally, numerical analyses were conducted for an inelastic structure of hysteresis described by the Bouc-Wen model. The results indicated that the performance of the passive TMD whose design parameters were optimized for an elastic structure considerably deteriorated when the hysteretic portion of the structural responses increased, and that the STMD showed about 15-40% more response reduction than the TMD.

• Earthquakes and Structures
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• 제6권5호
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• pp.495-514
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• 2014

The performance of passive control system for the seismic protection of a multi-tower cable-stayed bridge with the application of partially longitudinal constraint system is investigated. The seismic responses of the Jiashao Bridge, a six-tower cable-stayed bridge using the partially longitudinal constraint system are studied under real earthquake ground motions. The effects of the passive control devices including the viscous fluid dampers and elastic cables on the seismic responses of the bridge are examined by taking different values of parameters of the devices. Further, the optimization design principle of passive control system using viscous fluid dampers is presented to determine the optimized parameters of the viscous fluid dampers. The results of the investigations show that the control objective of the multi-tower cable-stayed bridge with the partially longitudinal constraint system is to reduce the base shears and moments of bridge towers longitudinally restricted with the bridge deck. The viscous fluid dampers are found to be more effective than elastic cables in controlling the seismic responses. The optimized parameters for the viscous fluid dampers are determined following the principle that the peak displacement at the end of bridge deck reaches to the maximum value, which can yield maximum reductions in the base shears and moments of bridge towers longitudinally restricted with the bridge deck, with slight increases in the base shears and moments of bridge towers longitudinally unrestricted with the bridge deck.

• 토지주택연구
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• 제5권2호
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• pp.107-114
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• 2014

수동형 제진장치를 이용하는 제진구조는 수년간 개발이 지속되고 있으며, 1990년대 중반이후로 여러 나라들에서 실무적인 적용이 빠르게 증가되고 있다. 국내의 경우 이러한 제진장치 중 강재이력형 댐퍼가 비교적 저렴한 비용과 설치와 관리가 용이하다는 이유로 건물의 내진설계를 위하여 보편적으로 많이 적용되고 있다. 이 논문에서는 건물의 지진응답을 개선하기 위하여 적용된 소위 카고메댐퍼로 불리우는 등방성 강재이력형 댐퍼(Isotropic Hysteretic Metallic Damper, IHMD)의 유효성에 대한 해석적인 사례연구를 제시하고 있다. 연구대상 건물은 18층 규모의 철근콘크리트 라멘조 아파트건물로 해석결과를 통하여 IHMD의 실효성을 실증적으로 보여주고 있다. 해석결과는 IHMD가 건물의 지진응답을 줄일 수 있는 매우 효과적인 방법임을 검증하고 있다.

• Earthquakes and Structures
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• 제11권6호
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• pp.1001-1025
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• 2016

Building structures generally have inherent low damping capability and hence are vulnerable to seismic excitations. Control devices therefore play a useful role in providing safety to building structures subject to seismic events. In recent years semi-active dampers have gained considerable attention as structural control devices in the building construction industry. Magneto-rheological (MR) damper, a type of semi-active damper has proven to be effective in seismic mitigation of building structures. MR dampers contain a controllable MR fluid whose rheological properties vary rapidly with the applied magnetic field. Although some research has been carried out on the use of MR dampers in building structures, optimal design of MR damper and combined use of MR and passive dampers for real scale buildings has hardly been investigated. This paper investigates the use of MR dampers and incorporating MR-passive damper combinations in building structures in order to achieve acceptable levels of seismic performance. In order to do so, it first develops the MR damper model by integrating control algorithms commonly used in MR damper modelling. The developed MR damper is then integrated in to the seismically excited structure as a time domain function. Linear and nonlinear structure models are evaluated in real time scenarios. Analyses are conducted to investigate the influence of location and number of devices on the seismic performance of the building structure. The findings of this paper provide information towards the design and construction of earthquake safe buildings with optimally employed MR dampers and MR-passive damper combinations.

• 국제초고층학회논문집
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• 제1권3호
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• pp.195-201
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• 2012

Today, a great effort to develop PBSD procedure to be utilized in Korea is given by domestic structural engineers, academics, and governmental organizations. After Great East Japan Earthquake (2011) took place, lots of clients in Korea became to concern of their buildings so that requests of seismic performance evaluation and seismic rehabilitation for existing buildings have been gradually increased. Such interests in seismic events initiated a rapid development of a series of guidelines for seismic performance evaluation and seismic performance enhancement. For new buildings, however, design guidelines for PBSD are yet well prepared in Korea and prescriptive design methods are dominant design procedure still. Herein, seismicity demands used in seismic performance evaluation and some important design parameters in NLRH are introduced. Some project examples for seismic performance evaluation and rehabilitation applying passive energy dissipation devices are also described in the latter part of paper.

• 한국지진공학회논문집
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• 제10권6호
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• pp.37-46
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• 2006

본 연구에서는 면진 건물의 내진 성능을 개선하기 위하여 최근 개발된 스마트 수동 제어 시스템을 적용하고 이의 효용성을 수치 모의실험을 통해 검증하였다. 스마트 수동 제어 시스템은 효과적인 반능동 제어 장치로 알려진 MR 감쇠기에 전자기 유도부를 도입하여 응답 변화에 따라 MR 감쇠기로 입력되는 전류를 변화시킴으로써 MR 감쇠기의 감쇠 특성을 조절하는 새로운 개념의 스마트 제진 시스템이다. 스마트 수동 제어 시스템에서 전자기 유도부는 영구자석과 솔레노이드 코일로 구성되며, 기존 스마트 제진 시스템의 계측기, 제어기, 외부 전원장치를 한꺼번에 대체할 수 있다. 면진 건물에 대한 스마트 수동 제어 시스템의 내진 성능을 수치적으로 검증하기 위하여 미국토목학회에서 제시한 면진 건물에 대한 벤치마크 제어 문제를 활용하였다. 스마트 수동 제어 시스템의 제진 성능을 MR 감쇠기를 이용한 기존 스마트 제어 시스템의 성능과 비교하였다. 수치 모의실험 결과를 통해 스마트 수동 제어 시스템이 면진 건물의 내진 성능을 개선하는 데 매우 유용함을 확인하였다.