Absolutism 의 특성

조경래 ( Kyoung Rai Cho ) 고려대학교 역사연구소 1962 사총 Vol.7 No.-

Development of simple design-oriented procedure for predicting the collision damage of FPSO caisson protection structures

Cho, Sang-Rai,Le, Dinh Ngoc Can,Jeong, Jang-Hyun,Frieze, Paul A.,Shin, Hyun-Kyoung Pergamon Press 2017 Ocean engineering Vol.142 No.-

<P><B>Abstract</B></P> <P>Protection structures for FPSO (Floating Production Storage and Offloading) caissons should be sufficiently strong so as not to contact caisson pipes even when the protection structure is damaged by an impact by attendant vessels. In the present structural design process, non-linear commercial packages are employed for collision analyses. However, non-linear collision analyses using commercial packages are time-consuming and expensive to operate, especially in the initial design stage. In this study, substantiation of the adopted commercial package was first performed using collision test results on single pipes and H-shape pipes. Then, a rigorous parametric study was conducted by changing the design variables. A simple analytical expression was derived assuming that the kinetic energy of the striking vessel was dissipated by the plastic elongation of pipes and rotation of plastic hinges. Using the parametric study results, design equations to predict the maximum deflection and overall bending damage were obtained by which the effects of local denting and dynamic behaviour could be considered. Additionally, an equation to predict the extent of local denting damage was also derived. The developed procedure was numerically substantiated using the predicted extent of damage to an actual protection structure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Collision damage of FPSO caisson protection structures is developed in this study. </LI> <LI> Numerical analysis method was substantiated using the collision tests results. </LI> <LI> Simple design equations were derived using the parametric study results. </LI> <LI> Maximum deflection, maximum overall bending and local denting damage are predicted. </LI> <LI> A calculation example is also provided for the developed procedure. </LI> </UL> </P>

Experimental investigation of slamming impact acted on flat bottom bodies and cumulative damage

Hyun Kyoung Shin,Byoungcheon Seo,Sang-Rai Cho 대한조선학회 2018 International Journal of Naval Architecture and Oc Vol.10 No.3

Most offshore structures including offshore wind turbines, ships, etc. suffer from the impulsive pressure loads due to slamming phenomena in rough waves. The effects of elasticity & plasticity on such slamming loads are investigated through wet free drop test results of several steel unstiffened flat bottom bodies in the rectangular water tank. Also, their cumulative deformations by consecutively repetitive free drops from 1000 mm to 2000 mm in height are measured.

Probabilistic ultimate strength analysis of submarine pressure hulls

Cerik, Burak Can,Shin, Hyun-Kyoung,Cho, Sang-Rai The Society of Naval Architects of Korea 2013 International Journal of Naval Architecture and Oc Vol.5 No.1

This paper examines the application of structural reliability analysis to submarine pressure hulls to clarify the merits of probabilistic approach in respect thereof. Ultimate strength prediction methods which take the inelastic behavior of ring-stiffened cylindrical shells and hemi-spherical shells into account are reviewed. The modeling uncertainties in terms of bias and coefficient of variation for failure prediction methods in current design guidelines are defined by evaluating the compiled experimental data. A simple ultimate strength formulation for ring-stiffened cylinders taking into account the interaction between local and global failure modes and an ultimate strength formula for hemispherical shells which have better accuracy and reliability than current design codes are taken as basis for reliability analysis. The effects of randomness of geometrical and material properties on failure are assessed by a prelimnary study on reference models. By evaluation of sensitivity factors important variables are determined and comparesons are made with conclusions of previous reliability studies.

Repeated lateral impacts on steel grillage structures at room and sub-zero temperatures

Truong, Dac Dung,Shin, Hyun Kyoung,Cho, Sang-Rai Elsevier 2018 International journal of impact engineering Vol.113 No.-

<P><B>Abstract</B></P> <P>This paper presents experimental and numerical investigation results for the plastic response of steel grillages, represented by one longitudinal stiffener and two transverse stiffeners of stiffened plates, used on ships or offshore structures under repeated mass impacts. The repeated mass impact scenario adopted in this paper could represent the repetition of impacted loads on marine structures due to contact with ice floes and floating objects during service. Repeated impact tests on grillage models at room and sub-zero temperatures (−50 °C) were conducted by releasing a knife-edge striker using a drop testing machine. The ends of the grillage models were firmly fixed onto a strong bed with support fixtures. To evaluate the repeated impact performance of the tested models, permanent deflections were measured after each impact test. Additionally, numerical simulations were performed using the commercial software package ABAQUS/Explicit to predict the extent of damage to the tested models caused by repeated impacts. In the calculations, the material properties of tested models were used to determine the strain hardening and strain rate hardening model using the equations recently proposed by the authors. Also, a simple analytical approach has been proposed to predict the damage evolution of the grillage subjected to repeated mass impacts. Reasonable agreement was achieved between the predictions and test results. The results showed that when the structure was repeatedly impacted, permanent deflections of the grillage significantly increased with increasing impact force. The permanent deflections tended to have certain values when the number of impacts increased. Based on the numerical results (which were substantiated with the experimental results), further calculations were then carried out to examine impact responses in greater detail and assess the effects of variations in boundary conditions and strain rate definitions on the response of grillages to repeated mass impacts.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Repeated mass impact tests were performed on four steel grillage structures at room and sub-zero temperatures for different kinetic energies. </LI> <LI> Deflection increments were reduced and contact force increased, but impact duration decreased with an increasing number of impacts. </LI> <LI> An analytical method has been developed in this study to predict the permanent deflections of grillage beam under repeated mass impact. </LI> <LI> There is reasonable agreement between the experimental results and predictions of the numerical and analytical analyses developed in this study. </LI> <LI> The effects of strain rate and boundary conditions on the impact responses of grillages were also numerically investigated. </LI> </UL> </P>

Dynamic lateral mass impact on steel stringer-stiffened cylinders

Do, Quang Thang,Muttaqie, Teguh,Shin, Hyun Kyoung,Cho, Sang-Rai Elsevier 2018 International journal of impact engineering Vol.116 No.-

<P><B>Abstract</B></P> <P>This paper focuses on the impact responses of large-diameter, thin-walled steel stringer-stiffened cylinders subjected to low-velocity mass impact. The impact scenarios employed in this study represent load actions as a result of supply vessel collisions with the main legs of floating offshore platforms and wind turbine structures. Two steel stringer-stiffened cylinders were fabricated and drop tests were performed at mid-span, using a rigid knife-edged indenter. The details of the experimental setup, test procedure and test results are reported in this paper. The experimental data appear to be useful for future benchmark studies. Numerical predictions of the impact response of the test models were simulated by means of the explicit solver of the finite element software package ABAQUS. The numerical predictions show a good agreement with the test results. The effect of the strain-rate hardening definition on the results is highlighted. Furthermore, parametric studies were conducted on stringer-stiffened cylinder models in order to clarify the progressive impact responses.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dynamic mass impact tests have been performed to investigate the response of stringer-stiffened cylinders. </LI> <LI> Numerical simulations of the impact response of the stringer-stiffened cylinders are conducted. </LI> <LI> The effects of the strain-rate hardening definition on the numerical results are highlighted. </LI> <LI> Parametric studies were conducted on stringer-stiffened cylinder models to clarify the effect of boundary conditions, impact velocities, impact locations, stringer-stiffeners as well as striker header shapes. </LI> </UL> </P>

보강판의 국부변형 손상과 잔류 강도의 실험연구

박상현(Sang-Hyun Park),신현경(Hyun Kyoung Shin),강응순(Eungsoon Kang),조상래(Sang-Rai Cho),장용수(Yong-Su Jang),백남기(Nam-Ki Baek),박동기(Dong-Ki Park) 대한조선학회 2020 大韓造船學會 論文集 Vol.57 No.4

A study on accumulated damage of steel wedges with dead-rise 10 due to slamming loads

Byoungcheon Seo,Dac Dung Truong,Sang-Rai Cho,Dongju Kim,Sookeun Park,Hyun Kyoung Shin 대한조선학회 2018 International Journal of Naval Architecture and Oc Vol.10 No.4

This paper presents the results of experimental investigation on the elasticeplastic response of steel unstiffened wedges with dead-rise 10 subjected to repeated impulsive pressure loadings. Repeated drop tests were performed with both wedge thickness and drop height varied. The pressure and histories were recorded during the tests and the permanent deflections were measured after every drop. Using the recorded test result, the effects of flexibility of wedges and repetition have been investigated. From the pressure history obtained from the tests the characteristics of the impulses were identified. Numerical simulations of the tests were made using the measured pressure history and the permanent deflection predictions were compared with those of the experiments.

Permanent set evolution of aluminium-alloy plates due to repeated impulsive pressure loadings induced by slamming

Truong, Dac Dung,Shin, Hyun Kyoung,Cho, Sang-Rai Springer-Verlag 2018 Journal of marine science and technology Vol.23 No.3

Response of low-temperature steel beams subjected to single and repeated lateral impacts

Dac Dung Truong,Hae-Jung Jung,Hyun Kyoung Shin,Sang-Rai Cho 대한조선학회 2018 International Journal of Naval Architecture and Oc Vol.10 No.6

This paper presents the experimental and numerical investigation results of the response of lowtemperature steel (LT-FH32 grade steel) beams under repeated impacts at room temperature and a single impact at a sub-zero temperature. After conducting tensile tests at room and sub-zero, repeated impact tests were conducted on two clamped single-beam models at room temperature, and singleimpact tests of two other clamped single-beam models were conducted at 50 C. The single and repeated impact tests were conducted by releasing a knife-edge striker using a drop testing machine. The permanent deflection of the model measured after each impact gradually increased with increasing number of impacts. Under the reduced temperature, the permanent deflection of the models slightly decreased. The numerical analyses were also performed to predict the damage response of the tested single-beam models. A comparison of the numerical prediction with those of experiments showed quite reasonable agreement.