• 대한두개안면성형외과학회지
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• 제9권2호
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• pp.51-54
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• 2008

Purpose: The choice of open versus closed reduction for mandibular subcondylar fracture is a debatable issue. To evaluate the advantage of open approach to closed method with IMF(intermaxillary fixation), we conducted a retrospective study to compare the outcomes of each method. Methods: From 2002 to 2006, 29 patients with mandibular subcondylar fractures were treated by open or closed reduction. 17 patients were treated by open reduction and 12 patients by closed reduction and IMF. Each group was assessed for duration of mandibular immobilization, incidences of buccal palsy, malocclusion, TMJ(temporomandibular joint) pain, and deviation of the mandible on mouth opening. Results: All cases showed accurate reduction in anatomical position, no significant displacement and no deviation on mouth opening during the follow-up period. IMF period is statistically shorter in open reduction (p<0.05). Differences in incidence of other complications were not significant statistically. Conclusion: As there are significant independent morbidities associated with IMF which requires postoperative rehabilitation, prolonged temporomandibular immobilization should not be overlooked. Some patients with poor compliances will not tolerate IMF in nonsurgical treatment. In the aspect of patient's convenience and early recovery by short IMF period, open reduction would be recommended as a better treatment method.

• Smart Structures and Systems
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• 제26권5호
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• pp.667-680
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• 2020

This study aims at reporting a systematic procedure for evaluating the static and dynamic structural performance of steel bridges based on a short-period structural health monitoring measurement. Sungsu bridge located in Korea is considered as a case study presenting the most recent tests carried out to examine the bridge condition. Short-period measurements of Structural Health Monitoring (SHM) system were used during the bridge testing phase. A novel symmetry index is introduced using statistical analyses of deflection and strain measurements. Frequency Domain Decomposition (FDD) is implemented to the strain measurements to estimate the bridge mode shapes and damping ratios. Furthermore, Markov Chain Monte Carlo (MCMC) is also implemented to examine the reliability of bridge performance while ambient design trucks are in static or moving at different speeds. Strain, displacement and acceleration were measured at selected locations on the bridge. The results show that the symmetry index can be an efficient and useful measure in assessing the steel bridge performance. The results from the used method reveal that the performance of the Sungsu bridge is safe under operational conditions.

• Bulletin of the Korean Chemical Society
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• 제19권4호
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• pp.422-428
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• 1998

In the present paper, we report a molecular dynamics (MD) simulation of non-rigid zeolite-A framework only as the base case for a consistent study of the role of intraframework interaction on several zeolite-A systems using the same technique in our previous studies of rigid zeolite-A frameworks. Usual bond stretching, bond angle bending, torsional rotational, and non-bonded Lennard-Jones and electrostatic interactions are considered as intraframework interaction potentials. The comparison of experimental and calculated structural parameters confirms the validity of our MD simulation for zeolite-A framework. The radial distribution functions of non-rigid zeolite-A framework atoms characterize the vibrational motion of the framework atoms. Mean square displacements are all periodic with a short period of 0.08 ps and a slow change in the amplitude of the vibration with a long period of 0.53 ps. The displacement auto-correlation (DAC) and neighbor-correlation (DNC) functions describe the up-and-down motion of the framework atoms from the center of α-cage and the back-and-forth motion on each ring window from the center of each window. The DAC and DNC functions of the framework atoms from the center of α-cage at the 8-ring windows have the same period of the up-and-down motion, but those functions from the center of 8-ring window at the 8-ring windows are of different periods of the back-and-forth motion.

• 한국지진공학회논문집
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• 제25권1호
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• pp.11-20
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• 2021

The seismic deformation method is conventionally used as a seismic design for a multi-utility tunnel in Korea. In the seismic deformation method, the soil ground's natural period is one of the most critical factors for calculating the ground displacement using cosine functions. Correction factors for the natural period and shear wave velocity have been used to consider the non-linearity of dynamic soil properties. However, the correction factors have been issued because the correction factors have not been sufficiently studied to consider Korea's regional conditions. This paper aims to evaluate the natural periods for the seismic deformation method considering Korea's ground conditions. Ground response analysis was performed using seven real earthquake records on twelve sites with different soil conditions where actual multi-utility tunnels are installed. As a result, natural periods of the sites were analyzed and new correction factors were proposed according to seismic performance and Korea's regional conditions.

• Earthquakes and Structures
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• 제12권3호
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• pp.285-296
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• 2017

Base isolation is a quite practical control strategy for enhancing the response of structural systems induced by strong ground motions. Due to the dynamic effects of base isolation systems, reduction in the interstory drifts of the superstructure is often achieved at the expense of high base displacement level, which may lead to instability of the structure or non-practical designs for the base isolators. To reduce the base displacement, several hybrid structural control strategies have been studied over the past decades. This study investigates a particular strategy that employs Tuned Mass Dampers (TMDs) for improving the performance of base-isolated structures and unlike previous studies, specifically focuses on the effectiveness of this hybrid control strategy in structures that are equipped with nonlinear base isolation systems. To consider the nonlinearities of base isolation systems, a Bouc-Wen model is selected and nonlinear dynamic OpenSees models are used to perform several time-history simulations in time and frequency domains. Through these numerical simulations, the effects of several parameters such as the fundamental period of the structure, dynamic properties of the TMD and isolation systems and properties of the input ground motion on the behaviour of TMD-structure-base isolation systems are examined. The results of this study provide a better insight into the performance of linear shear-story structures with nonlinear base isolators and show that there are many scenarios in which TMDs can still improve the performance of these systems.

• 콘크리트학회논문집
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• 제20권5호
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• pp.643-651
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• 2008

본 연구의 목적은 면진장치 설계 절차 체계화에 따른 면진건물의 응답특성을 사용지진 기록에 따라 평가하는데 있다. 이를 위한 대상 건물은 면진에 적합한 기초 면진 적용한 20층 주거 건물로, 지진기록 사용에 따른 응답특성을 평가하였다. 그 결과 면진건물의 시간이력해석을 위한 지진파의 선정은 응답 결과에 많은 차이가 발생할 수 있으므로 관련기준의 제정이 필요한 것으로 판단된다. 본 연구에서 제안한 지진기록을 이용한 면진구조물의 시간이력해석 결과, 면진층 변위, 층간변위비, 면진장치의 거동이 적절한 것으로 평가되었다. 결론적으로 본 연구에서 제안한 지진기록 및 면진장치 선정 결과, 설계된 면진건물의 지진저항 성능이 우수함을 확인할 수 있었다.

• Earthquakes and Structures
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• 제12권1호
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• pp.91-108
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• 2017

Superstructures and isolation systems of seismically isolated buildings located close to active faults may observe increased seismic demands resulting from long-period and high-amplitude velocity and displacement pulses existent in near-fault ground motions as their fundamental periods may be close to or coincident with these near-fault pulse periods. In order to take these effects into account, the 1997 Uniform Building Code (UBC97) has specified near-source factors that scale up the design spectrum depending on the closest distance to the fault, the soil type at the site, and the properties of the seismic source. Although UBC97 has been superseded by the 2015 International Building Code in the U.S.A., UBC97 near-source factors are still frequently referred in the design of seismically isolated buildings around the world. Therefore it is deemed necessary and thus set as the aim of this study to assess the necessity and the adequacy of near-source factors for seismically isolated buildings. Benchmark buildings of different heights with isolation systems of different properties are used in comparing seismic responses obtained via time history analyses using a large number of historical earthquakes with those obtained from spectral analyses using the amplified spectrums established through UBC97 near-source factors. Results show that near-source factors are necessary but inadequate for superstructure responses and somewhat unconservative for base displacement response.

• Earthquakes and Structures
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• 제15권3호
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• pp.319-334
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• 2018

In this paper, an analytical study was carried out to propose an optimum base-isolated system for the design of steel structures equipped with lead rubber bearings (LRB). For this, 5 and 10-storey steel moment resisting frames (MRFs) were designed as Special Moment Frame (SMF). These two-dimensional and three-bay frames equipped with a set of isolation systems within a predefined range that minimizes the response of the base-isolated frames subjected to a series of earthquakes. In the design of LRB, two main parameters, namely, isolation period (T) and the ratio of strength to weight (Q/W) supported by isolators were considered as 2.25, 2.5, 2.75 and 3 s, 0.05, 0.10 and 0.15, respectively. The Force-deformation behavior of the isolators was modelled by the bi-linear behavior which could reflect the nonlinear characteristics of the lead-plug bearings. The base-isolated frames were modelled using a finite element program and those performances were evaluated in the light of the nonlinear time history analyses by six natural accelerograms compatible with seismic hazard levels of 2% probability of exceedance in 50 years. The performance of the isolated frames was assessed in terms of roof displacement, relative displacement, interstorey drift, absolute acceleration, base shear and hysteretic curve.

• 공학논문집
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• 제6권1호
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• pp.53-63
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• 2004

본 연구에서는 지진하중을 받는 철근콘크리트 교각의 지진성능 및 파괴모드에 전단이 미치는 영향을 조사하였다. 본 연구에서 개발된 전단-축력간의 상호거동 이력응답 모델의 검증을 위하여 철근콘크리트 기둥 실험에 대한 비교해석을 수행하였다. 비교결과, 예측된 해석치는 전단에 관한 하중-변위 이력응답에 있어서 실험결과와 좋은 상관관계를 보여주었다. 아울러, 본 연구에서 개발된 모델을 이용하여 고베 지진에 의해서 손상된 철근콘크리트 교량의 비선형 시간이력 해석을 수행하였다. 교각의 변위응답에 관한 분석결과, 축력의 변화를 고려한 전단의 영향으로 인하여 최대변위가 상당히 증가하였고, 전반적인 교각 강성의 감소와 함께 진동주기의 증가를 유발한다는 것을 알 수 있었다. 따라서 전단과 축력의 영향을 동시에 고려한 응답에 철근콘크리트 교각의 지진손상 평가에 관해서 보다 나은 설명을 제공할 수 있을 것으로 사료된다.

• Earthquakes and Structures
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• 제7권6호
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• pp.1259-1281
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• 2014

This research has been conducted in order to investigate the effects of peak ground velocity (PGV) of near-field earthquakes on base-isolated structures mounted on Single Friction Pendulum (SFP), Double Concave Friction Pendulum (DCFP) and Triple Concave Friction Pendulum (TCFP) bearings. Seismic responses of base-isolated structures subjected to simplified near field pulses including the forward directivity and the fling step pulses are considered in this study. Behaviour of a two dimensional single story structure mounting on SFP, DCFP and TCFP isolators investigated employing a variety range of isolators and the velocity (PGV) of the forward directivity and the fling step pulses as the main variables of the near field earthquakes. The maximum isolator displacement and base shear are selected as main seismic responses. Peak seismic responses of different isolator types are compared to emphasize the efficiency of each one under near field earthquakes. It is demonstrated that rising the PGVs increases the isolator displacement and base shear of structure. The effects of the forward directivity are greater than the fling step pulses. Furthermore, TCFP isolator is more effective to control the near field effects than the other friction pendulum isolators are. This efficiency is more significant in pulses with longer period and greater PGVs.