• Proceedings of the KSR Conference
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• 2009.05b
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• pp.233-237
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• 2009

In this study, we suggest that several approaches to evaluate the collision acceleration value of a car in the article 35 and the guideline 16 of Korean rolling stock safety regulation. There are various methods to evaluate collision acceleration such as; a displacement comparison method by the double integration of filtered acceleration data, a velocity comparison method by the integration of filtered acceleration data, an analysis method of time-velocity curve, or a differential method of time-velocity curve. We compared these methods one another using 1D dynamic simulation model composed of nonlinear dampers, springs and bars, and masses. Also, we applied these methods to a hybrid model, which is made of 3D shell element model and 2D collision dynamics model, in order to evaluate whether 1D force-displacement curve modeling for energy absorbing structures have an effect on the collision acceleration levels or not.

• Journal of the Korean Society for Railway
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• v.14 no.1
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• pp.11-18
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• 2011

This paper proposed a new 2-D multi-body dynamic modeling technique to analyze overriding behaviors taking place during train collision. This dynamic model is composed of nonlinear springs, dampers and masses by considering the deformable characteristics of carbodies as well as energy absorbing structures and components. By solving this dynamic model for rollingstock, energy absorbing capacities of collision elements, accelerations of passenger sections, impact forces applied to interconnecting devices, and overriding displacements can be well estimated. For a case study, we chose KHST (Korean High Speed Train), obtained crush characteristic data of each carbody section from 3-D finite element analysis, and established a 2-D multi-body dynamic model. This 2-D dynamic model was simulated under the train-to-train collision scenarios, and evaluated with 3-D virtual testing model. It was founded from the simulation results that this 2-D dynamic model could well predict overriding behaviors, and the modeling technique of carbody deformation was very important in overriding estimation.

• 연구논문집
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• s.32
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• pp.103-111
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• 2002

In this study, the crashworthiness of KHST has been evaluated by analysing a nonlinear spring/bar-damper-mass model of 1-dimensional collision dynamics. The numerical results show that KHST can easily absorb kinetic energy at lower impact force and acceleration in heavy collisions, when compared with KTX. Also, in a Light collision like a traint-to-train accident at lower speed under 8 kph, the carbody and components of KHST can be protected without any damage except the energy absorbing tube to be replaced easily. However, KTX may be much damaged in the light collision because there is no energy absorbing tube. In conclusion, the crashworthy performance of KHST has been much improved than that of KTX, although there are something to be improved for a better crashworthy performance

• Computers and Concrete
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• v.19 no.1
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• pp.87-98
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• 2017

In recent year, the coat layer drops and the rebar rust of bridge parapets, which caused the structural performance degradation. In order to achieve the comprehensive rehabilitation, ultra high performance cementitious composites is proposed to existing RC parapet rehabilitation. The influence factors of UHPCC rehabilitation includes two parts, i.e., internal factors related with material, such as UHPCC layer thickness, corrosion ratio of rebars, fiber volume fraction, and external factors related with the load, such as impact speeds, impact angles, vehicle mass. The influence of the factors was analyzed in this paper based on the nonlinear finite element. The analysis results of the maximum dynamic deformation and the peak impact load of parapets revealed the influence of the internal factors and the external factors on anti-collision performance and degree degradation. This research may provide a reference for the comprehensive multifunctional rehabilitation of existing bridge parapets.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.2
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• pp.93-100
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• 2022

The collision behaviors of the tripod and jacket structures, which are considered as support structures for offshore wind towers at the Southwest sea of Korea, were compared by nonlinear dynamic analysis. These structures, designed for the 3 MW capacity of the wind towers, were modeled using shell elements with nonlinear behaviors, and the tower structure including the nacelle, was modeled by beam and mass elements with elastic materials. The mass of the tripod structure was approximately 1.66 times that of the jacket structure. A barge and commercial ship were modeled as the collision vessel. To consider the tidal conditions in the region, the collision levels were varied from -3.5 m to 3.5 m of the mean sea level. In addition, the collision behaviors were evaluated as increasing the minimum collision energy at the collision speed (=2.6 m/s) of each vessel by four times, respectively. Accordingly, the plastic energy dissipation ratios of the vessel were increased as the stiffness of collision region. The deformations in the wind tower occurred from vibration to collapse of conditions. The tripod structure demonstrated more collision resistance than the jacket structure. This is considered to be due to the concentrated centralized rigidity and amount of steel utilized.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.376-386
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• 2020

The aim of this study was to develop a new efficient strategy that uses the Vector form Intrinsic Finite-element (VFIFE) method to conduct the static and dynamic analyses of marine pipes. Nonlinear problems, such as large displacement, small strain, and contact and collision, can be analyzed using a unified calculation process in the VFIFE method according to the fundamental theories of point value description, path element, and reverse motion. This method enables analysis without the need to integrate the stiffness matrix of the structure, because only motion equations of particles established according to Newton's second law are required. These characteristics of the VFIFE facilitate the modeling and computation efficiencies in analyzing the nonlinear dynamic problem of flexible pipe with large deflections. In this study, a three-dimensional (3-D) dynamical model based on 3-D beam element was established according to the VFIFE method. The deep-sea flexible pipe was described by a set of spatial mass particles linked by 3-D beam element. The motion and configuration of the pipe are determined by these spatial particles. Based on this model, a simulation procedure to predict the 3-D dynamical behavior of flexible pipe was developed and verified. It was found that the spatial configuration and static internal force of the mining pipe can be obtained by calculating the stationary state of pipe motion. Using this simulation procedure, an analysis was conducted on the static and dynamic behaviors of the flexible mining pipe based on a 1000-m sea trial system. The results of the analysis proved that the VFIFE method can be efficiently applied to the static and dynamic analyses of marine pipes.

• Earthquakes and Structures
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• v.18 no.2
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• pp.171-184
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• 2020

The potential of using the roof water tanks as a mitigation measure to minimize the required separation gap and induced pounding forces due to collisions is investigated. The investigation is carried out using nonlinear dynamic analysis for two adjacent 3-story buildings with different dynamic characteristics under two real earthquake motions. For such analysis, nonlinear viscoelastic model is used to simulate forces due to impact. The sloshing force due to water movement is modelled in terms of width of the water tank and the instantaneous wave heights at the end wall. The effect of roof water tanks on the story's responses, separation gap, and magnitude and number of induced pounding forces are investigated. The influence of structural stiffness and storey mass are investigated as well. It is found that pounding causes instantaneous acceleration pulses in the colliding buildings, but the existence of roof water tanks eliminates such acceleration pulses. At the same time the water tanks effectively reduce the number of collisions as well as the magnitude of the induced impact forces. Moreover, buildings without constructed water tanks require wider separation gap to prevent pounding as compared to those with water tanks attached to top floor under seismic excitations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.211-222
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• 2011

In this paper a structural analysis of the PWR(pressurized water reactor) canister with 102cm diameter is carried out to evaluate the structural safety of the canister for the impact force occurring at the moment of collision with the ground in the falling plumb down accident from the carriage vehicle which may happen during the canister handling at the spent nuclear fuel disposal repository. For this, a rigid body dynamic analysis of the canister is executed to compute the impact force using the commercial CAE system, RecurDyn, and a nonlinear structural analysis is performed to compute stresses and deformations occurring inside the canister for this computed impact force using the commercial FEM code, NISA. From these analysis results, the structural safety of the canister is evaluated for the falling plumb down accident from the carriage vehicle due to the inattention during the canister handling at the repository. The rigid body dynamic analysis performed assuming the canister as a rigid body shows that the canister falls plumb down to the ground in two types. And also it shows that early collision impact force is the biggest one and following impact forces decrease gradually. The height of the carriage vehicle in the repository is assumed as 5m in order to obtain the stable structural safety evaluation result. The nonlinear structural analysis of the canister is executed for the biggest early impact force. The structural analysis result of the canister shows that the structural safety of the PWR canister is not secured for the falling plumb down accident from the moving carriage vehicle because the maximum stresses occurring in the cast iron insert of canister are bigger than the yield stress of the cast iron.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.601-609
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• 2022

Jack-up drilling rigs are mobile offshore platforms widely used in the offshore oil and gas exploration industry. These are independent, three-legged, self-elevating units with a cantilevered drilling facility for drilling and production. A typical jack-up rig includes a triangular hull, a tower derrick, a cantilever, a jackcase, living quarters and legs which comprise three-chord, open-truss, X-braced structure with a spudcan. Generally, jack-up rigs can only operate in water depths ranging from 130m to 170m. Recently, there has been an increasing demand for jack-up rigs for operating at deeper water levels and harsher environmental conditions such as waves, currents and wind loads. All static and dynamic loads are supported through legs in the jack-up mode. The most important issue by society is to secure the safety of the leg structure against collision that causes large instantaneous impact energy. In this study, nonlinear FE -analysis and verification of the requirement against collision for 35MJ recommended by DNV was performed using LS-Dyna software. The colliding ship used a 7,500ton of shore supply vessel, and five scenarios of collisions were selected. From the results, all conditions do not satisfy the class requirement of 35MJ. The loading conditions associated with chord collision are reasonable collision energy of 15M and brace collisions are 6MJ. Therefore, it can be confirmed that the identical collision criteria by DNV need to be modified based on collision scenarios and colliding members.

• 전자공학회논문지 IE
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• v.46 no.3
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• pp.33-41
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• 2009

Because the stability of obstacle avoidance ability is important for the safe operation of mobile robots, this paper deals with the analysis of dynamic stability of Limit-cycle navigation method that was proposed by authors. Limit-cycle navigation method is fast and easy to implement for fast moving mobile robots using limit-cycle characteristics of the 2nd-order nonlinear function. It can be applied to robots in dynamically changing environment such as the robot soccer. By adjusting the radius of the motion circle and the direction of the obstacle avoidance, the mobile robot can avoid the collision with obstacles and move to the destination point. The stability of Limit-cycle navigation method is analyzed with a linear model. To demonstrate the effectiveness and applicability, it is applied to the robot soccer Simulations and real experiments ascertain the merits of the proposed method.