Earticle

Judging from the occasional occurrences of minor and major earthquakes in Korean peninsula, it is generally considered that Korean peninsula is not located in safe zone from earthquake any more. The worldwide damages from earthquake in public buildings such as bridges are also urging the necessity for an appropriate earthquake proof action. The elastomeric bearings have been used in seismic isolation design of bridges. and elastomeric bearings are quite ideal ones which allow movement and rotation in all directions without restraining superstruture. Within the limits of this study on dynamic behavior of the LBR for seismic isolation design, the reaearch results revealed that the Laminated Rubber Bearing(LRB) is useful in bridges for seismic isolation design. In addition, the relationship between the shape factor and compressive strength is linear. It was also found that the compressive strength gets higher as the shape factor increases.

The speed of vehicles on both straight and curved bridges is crucial, particularly during bridge usage or when raising the bridge for bearing replacement. This study examines the impact of vehicle speeds of 30, 60, and 100 km/hr on the bearings of straight and curved bridges. By conducting time-history analysis considering the centrifugal force of vehicle loads, the effects of vehicle speed on the bearing reactions and displacements were determined. Results show that the reaction and displacement of bearings on straight bridges are less affected by vehicle speed compared to curved bridges, where these effects increase significantly with speed.

본 연구에서는 기존선 도시철도 구간에서 노후 자갈궤도를 콘크리트궤도로 급속개량을 위해 개발된 사전제작형 급속개량 궤도(P-FIT)의 운행선 급속 시공 시, 사전제작형 콘크리트패널 하부에 이산지지 되는 탄성고무받침의 시공오차에 따른 구조 안전성 검토를 수행하였다. 사전제작형 콘크리트패널에 열차하중 재하시 탄성고무받침 종방향 및 횡방향 최대 시공오차를 고려하여 검토한 결과, 패널에 발생하는 응력은 탄성고무받침의 종방향, 횡방향, 종·횡방향 동시 시공오차 발생 순으로증가하였으나 허용응력 이내인 것으로 나타나 구조적 안전성을 확보하는 것으로 나타났다.

In this study, in the case of rapid construction of Precast Fast Improvement slab Track(P-FIT) developed for quick improvement of the old ballast track into concrete tracks in the urban railway section of the existing line, structural safety evaluation was conducted according to the construction error of the elastic rubber support discretely supported under the precast concrete panel. As a result of examining the maximum construction error in the longitudinal and lateral directions of the elastic rubber bearing under the train load on the precast concrete panel, the stress acting on the panel increased in the order of construction errors occurrence in the longitudinal, lateral, and longitudinal and lateral directions of the elastic rubber bearing. But it has been shown to secure structural safety since the generated stress was found to be within the allowable stress.

The fluid loading effect has been investigated for the shipboard equipment foundation mobility with finite element model. For thepurpose, two kinds of finite element models for 60m class ship have been developed: global and local model. The former is for lowfrequency range and the latter for middle frequency range. These finite element models contain added mass explaining fluid loadingeffect. Added mass has been implemented with virtual mass matrix derived from Laplace equation governing fluid surrounding ship hull. The mobility assessment result for diesel generator foundation of the objective model shows that the fluid loading effect should beconsidered, especially in low frequency range, to more accurately assess shipboard equipment foundation mobility.

경부 고속철 40 m 단경간 PSC 교량을 대상으로 38 자유도 KTX 동력차를 주행속도 500 km/h까지 12 단계 불규칙 궤도형상과 상호 작용력을 고려하여 해석하였다. 차량의 윤축하중과 중심회전각을 평가하기 위하여 170 m 일반도상을 교량과 조합하여 횡압과 탈선계수 그리고 윤중감소율을 허용기준과 비교하였다. 단순교와 연속교의 교량받침 최대 변위와 누적이동거리를 주행속도별로 해석하였다. PTFE 마찰판과 DP-mate의 EN-1337-2 기준의 장기마찰시험을 수행하였다. 수행된 장기마찰시험은 차세대 고속철의 증가되는 주행속도를 고려하여 개선 방안을 제안하였다.

Structural behaviour of PSC box bridge, on which KTX train runs, is analysed up to 500 km/h speed considering 12 stages track irregularity and interaction between bridge and vehicle. To evaluate wheel forces and rotations of vehicle, lateral wheel forces, derail factor and offload factor calculated on the track combining the bridge and 170 m normal track are compared with existing allowed limits. Maximum longitudinal displacement and accumulated sliding distance of the brige bearings for simply supported and 2 span continuous PSC bridges are presented by each running speeds. Long-term friction tests based on EN-1337-2 are conducted between PTFE and DP-mate plates. Finally, the long-term friction tests are proposed to consider the increasing speed of next generation high-speed train.

In order to increase seismic performance of nuclear power plant (NPP) in strong seismic zone, lead-rubber bearing (LRB) can be applied to seismic isolation system of NPP structures. Simple equivalent linear model as structural analysis model of LRB is more widely used in initial design process of LRB than a bilinear model. Seismic responses for seismically isolated NPP containment structures subjected to earthquakes categorized into 5 different soil-site classes are calculated by both of the equivalent linear- and bilinear- LRB models and compared each others. It can be observed that the maximum displacements of LRB and shear forces of containment in the case of the equivalent linear LRB model are larger than those in the case of bilinear LRB model. From the seismic fragility curves of NPP containment structures isolated by LRB, it can be observed that seismic fragility in the case of equivalent linear LRB model are about 5~30 % larger than those in the case of bilinear LRB model.

In order to perform a soil-isolation-structure interaction analysis of seismically isolated nuclear power plant (NPP) structures, the nonlinear behavior of a seismic isolation system may be converted to an equivalent linear model used in frequency domain analysis. Seismic responses for seismically isolated NPP containment structures subjected to a simple artificial acceleration history and different site class earthquakes are evaluated for the equivalent-linear and nonlinear models that have been applied to lead-rubber bearing (LRB) modeling. It can be observed that the maximum displacements of the equivalent linear model are larger than that of the nonlinear model. From the floor response spectrum analysis for the top of NPP containment structures, it can be observed that the spectral acceleration of an equivalent linear model at about 0.5 Hz frequency is about 2~3 times larger than that of a nonlinear model.

납코어가 삽입된 적층고무받침은 주요 재료가 온도에 대한 의존성을 보유하고 있으므로 온도 환경이 장치의 성능에 미치는 영향이 적지 않다. 따라서, 본 논문에서는 대표적인 면진장치인 납면진받침에 대하여 실규모 장치를 제작하고 온도변화에 따른 강성 및 감쇠 특성변화에 대하여 실험을 통하여 분석하고 평가하였다. 실물 크기의 납면진받침을 사용하여 $-10^{\circ}C$, $0^{\circ}C$, $10^{\circ}C$, $20^{\circ}C$, $30^{\circ}C$, $40^{\circ}C$의 온도 조건에 대하여 ISO22762:2010에서 제시하고 있는 특성시험법을 적용하여 수직강성 및 수평특성에 대하여 의존성 경향을 파악하였다. 또한, 면진받침 설계 시 주요한 평가지표로 사용되는 2차강성 및 특성강도에 대하여 해외 제조사에서 제시하고 있는 온도보정식과 시험결과를 비교하였으며 수직강성에 대한 온도의존 경향을 파악하였다.

Rubber laminated bearings with lead core are highly affected by changes in temperature because key materials which are rubber and lead have temperature dependencies. In this study, two full scale LRB(D800, S=5) are manufactured and temperature dependency tests on shear properties are accomplished. The shear properties at the 3rd cycle are used at $-10^{\circ}C$, $0^{\circ}C$, $10^{\circ}C$, $20^{\circ}C$, $30^{\circ}C$, $40^{\circ}C$ respectively. The double shear configuration, simultaneously testing two pieces, is applied for compression shear test in order to minimize the friction effects due to the test machine, described in ISO 22762-1:2010. Characteristic strength, post-yield stiffness, effective stiffness, equivalent damping ratio are estimated and presented coefficient due to the temperature changes.

교량받침은 상부구조물의 변위를 흡수하는 역할을 수행한다. 교량 받침으로 일반적인 탄성받침은 고무 자체의 전단변형 특성으로 상부구조물의 변위를 흡수한다. 공용 수명동안 받침 자체의 파괴 또는 받침의 기능 저하로 인하여 교량의 내구성을 저해하지 않기 위해서는 탄성받침의 피로내구성이 확보되어야 한다. 이에 이 논문에서는 온도변화에 의해 발생되는 상부구조물의 변위를 수용하는 탄성받침의 전단성능 내구성을 확인하기 위하여 전단피로실험을 실시하였다. 또한 탄성받침을 구성하는 한 층의 내부 고무층을 여러 겹의 고무로 겹쳐서 제작하는 제작 관행이 탄성받침의 전단성능에 어떠한 영향을 미치는지 조사하였다. 전단피로실험 결과 전단피로반복 회수에 따라 강성변화에 대한 특정한 경향을 찾아보기 어려웠다. 하지만 두꺼운 내무 고무층을 갖는 받침을 제작하는 경우 일부 업체에서는 관행적으로 여러 층의 고무를 겹쳐서 한 층의 내부고무층이 되도록 제작하는데 이 경우에는 받침의 전단성능이 현저하게 저하되거나 받침이 조기에 파괴되는 결과를 가져왔다.

Bridge bearings are devices absorbing the displacements of the superstructure. Elastomeric bearings used generally as bridge bearings absorb the displacements of the superstructure using their rubber characteristics. Elastomeric bearings should make sure their shear fatigue performance not to impede the durability of bridge system. In this paper shear fatigue tests were performed and stiffness were measured through the shear fatigue tests. Tests results show the measured stiffness of elastomeric bearings have no specific tendency. This paper found that elastomeric bearings show bad shear performance or fail early if elastomeric bearings are manufactured with a doublefold elastomeric layer.

In this paper, vibration reduction of resiliently mounted machinery and effect of the foundation impedance is studied. SBN (Structure-borne noise) reduction through the mount is analyzed by assuming that the system is modeled as a mass-spring system, while the impedance of the floor is included in the prediction. The comparison of the SBN difference through the mount between predictions and measurements show that the slopes are similar in the case of single-mount system, while the measurements differs significantly from the predictions in the case of the double-resilient system.

This study was conducted to investigate the specificities of four fulcrum types for geo-statistical analysis of elevation within rice paddy field. In Korea, the spaces between inter-rows and between hills for rice transplanting are 30cm and 11cm to 14cm, respectively. So, the size and shape of fulcrum for field elevation measurement should be considered according to the inter-row and the hill spaces. Four kinds of fulcrum were chosen such as round-shape with 2.5cm diameter, circular-shape with 10cm diameter, 10cm (one third of inter-row space) by 24cm (double of hill space) rectangular-shape, and 20cm (two-thirds of inter-row space) by 24cm rectangular-shape. The resulting descriptive statistics couldn't determine the best fulcrum type to measure the rice paddy field elevation. But the results of geo-statistical analysis could determine the best fulcrum type. In the case of 10cm by 24cm rectangular-shape fulcrum, Nugget and range, meaning measurement error and/or noise, and limit of spatial connection, respectively, were minimum; Q value meaning weight of spatial structure and $r^2$ value were minimum, and residual sum of squares was minimum. It means that 10cm by 24 cm rectangular-shape fulcrum could best describe the rice paddy field elevation.

We performed the heat aging test to predict the useful lifetime of Elastomeric Bearing Chloroprene Rubber (CR) used for supporting bridge. During the test, we measured elongation that are influenced by temperature and aging time. The failure of a test piece is defined as the point at which the elongation reaches to 75% of the initial value. This failure criterion is based on KS F 4420: 1998 (Elastomeric Bearing for bridge). Through the accelerated heat aging test, we found that the Arrhenius relationship and the Weibull lifetime distribution are appropriate as the life-temperature relationship and lifetime distribution of the CR, respectively. Using the Arrhenius -Weibull model, the parameters of the model are estimated and the lifetime of the CR at use condition is predicted.

Dynamic responses of multi-span simply supported bridges are investigated to examine the effect of damaged bearings under seismic excitations. The damaged bearings are modeled as sliding elements with friction between the super-structure and the pier top. Various values of the friction coefficients for damaged bearings are examined with increasing magnitudes of peak ground accelerations. It is found that the g1oba1 seismic behaviors are significantly influenced by the occurrence of bearing damage. It should be noticed that the most possible location of unseating failure of superstructures differs with that in the model without consideration of the bearing damage. It can be concluded that the bearing damage may play the major role in the unseating failure of a bridge system, so that the damage of bearings should be included to achieve more rational seismic safety evaluation.

한국어와 몽골어는 이른 시기에 고유문자가 없어 이웃한 나라의 한자를 빌려와 자신들의 말을 기록하였다. 그러나 한자는 음절말에서 l 자음을 표기하기가 어려우므로 별도의 방법을 사용하였다. 거란이 거란대자와 소자를 만들어 거란어를 표기한 이후로는 음절말의 l 자음은 별도의 방법을 사용하여 표기하지는 않았다. 그러나 거란대자는 음절문자의 성격이 강하므로 음절말의 l 문자가 여러 형태로 나타난다. 기존의 연구에서 추출한 음절말에 l 자음이 있는 문자들을 분석한 결과 (dal), (dal/tal), (sul), (γul/qʊl) 네 글자는 음절의 첫소리에 자음이 있는 것으로 분석하였다. 첫소리에 자음이 없는 음절말의 l 자음으로는 (al), (al), /(ol), (ul), (il)이 있다. , ,  문자 역시 첫소리에 자음이 없이 음절말에서 l 자음을 나타낸다. 음절말에 l 자음이 있으며 두 개의 모음이 나타나는 (u-ul)이 있는데 이 문자는 두 가지 뜻(겨울/시집가다)로 사용된다. 음절말의  문자는 부분적으로 l 자음을 나타내는 부호처럼 사용된 것으로 보이지만 추가 연구가 필요하다.

Korean and Mongolian did not have their own characters in the early days, so they borrowed Chinese characters from neighboring countries to record their own language. However, since Chinese characters are difficult to represent the l consonant in syllable-finals, a separate method was used. After creating Khitan large script and small script to represent Khitan language, the l consonant in syllable-finals was not represented using a separate method. However, since Khitan large script has a syllabic letter, the l character in syllable-finals appears in various forms. As a result of analyzing the characters with l consonants in syllable-finals extracted from previous studies, the four characters ?(dal), ?(dal/tal), ?(γul/q?l) and ?(sul) were analyzed as having consonants in the first sound of the syllable. The l consonants in syllable-finals without consonants in the first sound include ?(al), ?(al), ?/?(ol), ?(ul), and ?(il). The three letters ?, ?, ? also represent the l consonant in syllable-finals without a consonant in the initial sound. There is ?(u-ul) that has the l consonant in syllable-finals and appears as two vowel, and this letter is used with two meanings (winter/getting married). The letter ? in syllable-finals seems to have been used as a symbol to partially represent the l consonant, but further research is needed.