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Ernest Nsabimana,Young-Hoon Jung(정영훈),Taehee Lee(이태희) 한국철도학회 2014 한국철도학회 학술발표대회논문집 Vol.2014 No.5
This paper investigated the effects of multiple wheelsets of bogies and their separated distances in the multiple passenger cars on dynamic response of subsoil at the critical speed. To simulate this condition, two-dimensional dynamic finite element analyses were used. For the present purposes, the simple train vehicle model, which has been developed previously by authors, was extended such that the train vehicle model has up to three passenger cars. The car-body mass and wheel are connected via a spring-dashpot. The wheel numerically represented by a reference point was interacted with the rail beam via the nonlinear Hertzian contact model. The slab track and subsoil were modeled using continuum elements bounded by special infinite elements. To observe the effect of the train speed of one, two, and three passenger cars, Rayleigh wave velocities in the subsoil were observed. Numerical results from time-domain simulations show that dynamic response at the critical speed becomes notable when the train vehicle has more than three passenger cars.
A Dynamic Modeling of Vertical Rail Deflection in Concrete Slab Track for High Speed Trains
Ernest Nsabimana,Chan-Yong Choi(최찬용),Young-Hoon Jung(정영훈) 한국철도학회 2013 한국철도학회 학술발표대회논문집 Vol.2013 No.5
Most of developed and many developing countries in the world are preparing to update their existing lines as well as to create new high speed railway routes. Such high speeds make the response of railway track become dynamic. In this paper, a finite element modeling is attempted to simulate time domain dynamic behavior of the two-dimensional slab track system. A vehicle wheel is simply modeled as a sprung mass with two reference points in which the wheel weight is applied at one end and the equivalent vehicle weight is assigned to the other end. The contact between a reference point and the rail is nonlinearly simulated. The numerically predicted vertical rail displacements show a remarkable influence of train velocity on the concrete track system.
Ernest Nsabimana,Young-Hoon Jung(정영훈),Taehee Lee(이태희) 한국철도학회 2013 한국철도학회 학술발표대회논문집 Vol.2013 No.11
The stresses change level is one of the most important factors affecting the development of nonlinear behavior of subsoil materials in railway tracks. In high speed lines, the ground vibrations induced by trains have a significant dynamic effect on the stresses produced in the subsoil and the rise of train speed will generate such strong vibrations that will increase and accelerate the development of the larger stresses in subsoil. In this present paper, for the computational analysis, a dynamic numerical simulation in finite element method and a static analytical method are both attempted to compute stresses and their distribution in two dimensional slab track model and a homogenous half-space respectively. The results of the numerical results are compared with analytical solutions to draw conclusions.
열차 증속에 따른 콘크리트 궤도 노반의 동적 응력 변화
이태희,최찬용,Ernest Nsabimana,정영훈 한국지반공학회 2013 한국지반공학회논문집 Vol.29 No.10
Societal interest on a faster transportation demands an increase of the train speed exceeding current operation speedof 350 km/h. To trace the pattern of variations in displacements and subsoil stresses in the concrete slab track system,finite element simulations were conducted. For a simple track-vehicle modeling, a mass-point system representing themoving train load was developed. Dynamic responses with various train speeds from 100 to 700 km/h were investigated. As train speeds increase the displacement at rail and subsoil increases nonlinearly, whereas significant dynamicamplification at the critical velocity has not been found. At low train speed, the velocity of elastic wave carrying elasticenergy is faster than the train speed. At high train speed exceeding 400 km/h, however, the train speed is approximatelyidentical to the elastic wave velocity. Nonlinearity in the stress history in subsoil is amplified with increasing train speeds,which may cause significant plastic strains in path-dependent subsoil materials.
Kim, Dongwook,Lee, Juhyung,Nsabimana, Ernest,Jung, Young-Hoon Techno-Press 2012 Ocean systems engineering Vol.2 No.3
Recently, interest of offshore structure construction in South Korea is growing as the land space becomes limited for further development and the renewable energy grows to be more attractive for the replacement of the fossil energy. In order for the optimal construction of optimum offshore floating structures, development of safe and economical offshore foundation technologies is a priority. In this study, the large-deformation behavior of a suction pile, which markets are rapidly growing nowadays, is analyzed for three different loading locations (top, middle, and bottom of the suction pile) with three different displacement inclinations (displacement controlled with displacement inclinations of 0, 10, and 20 degrees from the horizontal). The behavior analysis includes quantifications of maximum resistances, translations, and rotation angles of the suction pile. The suction pile with its diameter of 10 m and height of 25 m is assumed to be embedded in clay, sand, and multi layers of subsea foundation. The soil properties of the clay, sand, and multi layers were determined based on the results of the site investigations performed in the West sea of South Korea. As analyses results, the maximum resistance was observed at the middle of the suction pile with the displacement inclination of 20 degrees, while the translations and rotations resulting from the horizontal and inclined pullouts were not significant until the horizontal components of movements at the loading points reach 1.0 m.