연결 동조질량감쇠기를 이용한 인접한 쌍둥이 구조물의 새로운 진동제어

옥승용 ( Seung-yong Ok ),김승민 ( Seung-min Kim ) 한국안전학회 2017 한국안전학회지 Vol.32 No.2

This study deals with new application method of the connecting tuned mass damper (CTMD) system for efficient vibration control of adjacent twin structures which have the same dynamic properties such as natural frequency and damping characteristics to each other. In the existing research, the vibration control of the twin structures has a limit to the application of the conventional damper-connection method of the twin structures. Due to the same frequency characteristics leading to the equally vibrating behaviors, it is impossible to apply the conventional connection method of the adjacent structures. In order to overcome these limitations induced by the symmetry of the dynamic characteristics, we propose a new CTMD-based control system that adopts the conventional connection configuration but unbalances the symmetric system by arranging the control device asymmetrically and then can finally achieve the efficient control performance. In order to demonstrate the applicability of the proposed system, numerical simulations of the optimally designed proposed system have been performed in comparison with the optimal design results of the existing independent single tuned mass damper (STMD) control system and the another optimal control system previously proposed by the same author, hereafter called CTMD-OsTMD. The comparative results of the control performances among STMD, CTMD-OsTMD and the proposed CTMD systems verified that the newly proposed control system can be a control-efficient and cost-effective system for vibration suppression of the two adjacent twin structures.

퍼지관리제어기법의 강인성능평가

옥승용,박관순,고현무,Ok, Seung-Yong,Park, Kwan-Soon,Koh, Hyun-Moo 한국지진공학회 2005 한국지진공학회논문집 Vol.9 No.5

Using the variable control gain scheme on the basis of fuzzy-based decision-making process, Fuzzy supervisory control (FSC) technique exhibits better control performance than linear control technique with one static control gain. This paper demonstrates the effectiveness of the FSC technique by evaluating the robust performance of the FSC technique under the presence of uncertainties in the models and the excitations. Robust performance of the FSC system is compared with that of optimally designed LQG control system for the benchmark cable-stayed bridge presented by Dyke et al. Parameter studies on the robust performance evaluation are carried out by varying the stiffness of the bridge model as well as the magnitudes of several earthquakes with different frequency contents. From the comparative study of two control systems, FSC system shows the enhanced control performance against various magnitudes of several earthquakes while maintaining lower level of power required for controlling the bridge response. Especially, FSC system clearly guarantees the improved robust performance of the control system with stable reduction effects on the seismic responses and slight increases in total power and stroke for the control system, while LQG control system exhibits poor robust performance. 지진응답제어를 위한 효율적 방법으로 제시된 퍼지관리제어기법은 퍼지에 기반한 의사결정과정을 통하여 가변 제어이득행렬을 구현함으로써 하나의 제어이득만으로 표현되는 선형제어기법보다 개선된 제어성능을 발휘할 수 있다. 이 논문에서는 퍼지관리제어기법의 효율성을 하중 및 교량모델의 불확실성에 대한 제어성능의 강인성 측면에서 평가하였다. 강인성 평가에 있어서는 Dyke등이 제시한 벤치마크 교량에 대하여, 최적설계된 LQG기법과 제어성능을 비교하는 방법을 사용하였다. 불확실성을 주는 요인으로는 주파수 특성이 다른 여러 지진가속도의 규모 및 교량의 강성변화를 가정하였다. 최적설계된 LQG 제어기와 제어효과를 비교한 결과, FSC시스템이 지진의 종류와 규모에 따라 보다 작은 전력을 사용하면서도 개선된 제어성능을 발휘하였다. 특히, LQG 제어시스템이 강성변화에 대하여 불안정한 제어성능을 보인 반면, FSC 시스템은 매우 안정적인 응답제어효과를 보이면서도 제어시스템에 소요되는 전력량과 제어장치의 스트로크에 있어서도 큰 변화를 보이지 않음으로써 매우 탁월한 강인성을 보장할 수 있는 것으로 나타났다.

지게차 충돌 위치 및 보관물류 분포에 따른 선반구조물의 거동특성분석

옥승용 ( Seung Yong Ok ),권오용 ( Oh Yong Kwon ),백신원 ( Shin Won Paik ) 한국안전학회(구 한국산업안전학회) 2013 한국안전학회지 Vol.28 No.6

The statistics of recent accidents in warehouses show that a heavy toll of lives were produced by various accidents, e.g. collision,overturn, fall, slip, exposure to harmful substances or environments, etc. Of significant concern amongst them is the collision, especially the collision between forklift and storage rack structure. Accordingly, this study focuses on behavioral characteristics of rack structure subjected to dynamic impact loading of a forklift. For this purpose, time-domain response analysis has been performed on a standard 2-bay six-story rack structure consisting of columns, beams and bracing members with perforated open section. In order to investigate the most critical scenario, the impact loads are applied in both down-aisle and cross-aisle directions, and the impact locations are also varied along the shelves of the palettes. In order to deal with storage distributions, three types of rack structures are further taken into account: original empty rack structure with no storage, half-loaded rack structure and fully-loaded rack structure. The numerical simulation results demonstrate that the dynamic characteristics of the rack structure are significantly dependent on the distribution of the storage goods and its natural period varies from 0.24sec to 1.06sec, approximately 4.4 times. Further, the parametric studies show that the forklift impact is most critical to the safety of the rack structure when it collides either at the base or at the top of the rack structure.

다목적 최적화 기법을 이용한 비선형 지진격리시스템의 최적 설계

옥승용(Ok Seung-Yong),곽신영(Kwag Shin-Young),고현무(Koh Hyun-Moo) 대한토목학회 2009 대한토목학회 학술대회 Vol.2009 No.10

동적능동제어시스템의 FORM기반 구조신뢰성해석

옥승용 ( Seung Yong Ok ) 한국안전학회 2013 한국안전학회지 Vol.28 No.1

확률모델 불확실성을 고려한 구조물의 신뢰도 기반 최적설계 -제1편: 설계 방법

옥승용 ( Seung Yong Ok ),박원석 ( Won Suk Park ) 한국안전학회(구 한국산업안전학회) 2012 한국안전학회지 Vol.27 No.5

Reliability-based design optimization (RBDO) problem is usually formulated as an optimization problem to minimize an objective function subjected to probabilistic constraint functions which may include deterministic design variables as well as random variables. The challenging task is that, because the probability models of the random variables are often assumed based on limited data, there exists a possibility of selecting inappropriate distribution models and/or model parameters for the random variables, which can often lead to disastrous consequences. In order to select the most appropriate distribution model from the limited observation data as well as model parameters, this study takes into account a set of possible candidate models for the random variables. The suitability of each model is then investigated by employing performance and risk functions. In this regard, this study enables structural design optimization and fitness assessment of the distribution models of the random variables at the same time. As the first paper of a two-part series, this paper describes a new design method considering probability model uncertainties. The robust performance of the proposed method is presented in Part 2. To demonstrate the effectiveness of the proposed method, an example of ten-bar truss structure is considered. The numerical results show that the proposed method can provide the optimal design variables while guaranteeing the most desirable distribution models for the random variables even in case the limited data are only available.

하중 및 모델 불확실성에 따른 래선반구조물의 파괴모드멸 신뢰성 평가 및 경향성 분석

옥승용 ( Seung Yong Ok ) 한국안전학회(구 한국산업안전학회) 2013 한국안전학회지 Vol.28 No.7

According to recent statistics of fatalities and injuries in warehouses, the collision of forklift to storage rack structures is one of the major accidents. Due to the randomness of forklift-colliding event and inherent uncertainties in the impact loading and the structural model, the quantitative assessment of the structural safety of the forklift-colliding rack structure can be treated by the probabilistic approaches such as FORM, SORM and MCS, etc. In order to investigate the reliability of the rack structure, several component-level failure modes are taken into account and the assessment results of the corresponding failure probabilities are verified in comparison with the FORM, SORM and MCS results. The numerical results demonstrate that FORM is the most numerically efficient method with less accurate assessment results and MCS is the accurate but numerically inefficient method, whereas SORM is both the accurate and numerically efficient method. Further, Parametric studies on the level of the uncertainties in the load and model parameters demonstrate that the failure probability of the rack is increased as the uncertainty level is increased, and vice versa.

물류보관 랙선반시설물의 시스템신뢰성 해석

옥승용 ( Seung Yong Ok ),김동석 ( Dong Seok Kim ) 한국안전학회(구 한국산업안전학회) 2014 한국안전학회지 Vol.29 No.4

This study proposes a system reliability analysis of rack storage facilities subjected to forklift colliding events. The proposedsystem reliability analysis consists of two steps: the first step is to identify dominant failure modes that most contribute to the failure ofthe whole rack facilities, and the second step is to evaluate the system failure probability. In the first step, dominant failure modes areidentified by using a simulation-based selective searching technique where the contribution of a failure mode to the system failure isroughly estimated based on the distance from the origin in the space of the random variables. In the second step, the multi-scale systemreliability method is used to compute the system reliability where the first-order reliability method (FORM) is initially used to evaluatethe component failure probability (failure probability of one member), and then the probabilities of the identified failure modes and theirstatistical dependence are evaluated, which is called as the lower-scale reliability analysis. Since the system failure probability iscomprised of the probabilities of the failure modes, a higher-scale reliability analysis is performed again based on the results of thelower-scale analyses, and the system failure probability is finally evaluated. The illustrative example demonstrates the results of thesystem reliability analysis of the rack storage facilities subjected to forklift impact loadings. The numerical efficiency and accuracy of theapproach are compared with the Monte Carlo simulations. The results show that the proposed two-step approach is able to provideaccurate reliability assessment as well as significant saving of computational time. The results of the identified failure modes additionallylet us know the most-critical members and their failure sequence under the complicated configuration of the member connections.

확률모델 불확실성을 고려한 구조물의 신뢰도 기반 최적설계 -제2편: 강인 성능 평가

옥승용 ( Seung Yong Ok ),박원석 ( Won Suk Park ) 한국안전학회(구 한국산업안전학회) 2012 한국안전학회지 Vol.27 No.6

This paper, being the second in a two-part series, presents the robust performance of the proposed design method which can enhance a reliability-based design optimization(RBDO) under the uncertainties of probabilistic models. The robust performances of the solutions obtained by the proposed method, described in the Part 1, are in-vestigated through the parametric studies. A 10-bar truss example is considered, and the uncertain parameters include the number of data observed, and the variations of applied loadings and allowable stresses. The numerical results show that the proposed method can produce a consistent result despite of the large variations in the parameters. Especially, even with the relatively small data set, the analysis results show that the exact probabilistic model can be success-fully predicted with optimized design sections. This consistency of estimating appropriate probability model is also observed in the case of the variations of other parameters, which verifies the robustness of the proposed method.

동일한 인접구조물의 효율적 진동제어방안

옥승용 ( Seung Yong Ok ) 한국안전학회(구 한국산업안전학회) 2014 한국안전학회지 Vol.29 No.3

This study proposes a new control approach for efficient vibration suppression of two identical adjacent structures. The conventional control approach of two adjacent structures is to interconnect the two structures with passive, semi-active or active control devices. However, when the two adjacent structures are identical to each other, their dynamical behaviors such as frequency and damping properties are also the same. In this case, the interconnected control devices cannot exhibit the dissipative control forces on the both structures as expected since the relative displacements and velocities of the devices become close to zero. In other words, the interconnection method does not work for the twin structures as enough as expected. In order to solve this problem, we propose several new control approaches to effectively and efficiently reduce the identically-fluctuating responses of the adjacent structures with minimum control efforts. In order to demonstrate the proposed control systems, the proposed several control systems are optimally designed and their control performances are compared with that of the conventional optimal control system where each TMD(tunedmass damper) is installed in each structure for independent control purpose. The simulated results show that one of the proposed control systems(System 04) is able to guarantee enhanced control performance compared with the conventional system