• Journal of Energy Engineering
• /
• v.21 no.4
• /
• pp.339-345
• /
• 2012

RMembrane LNG storage tanks have been recently investigated to replace full-containment LNG storage tanks because of safety and cost aspects. Quantitative Risk Analysis (QRA) and Finite Element Method (FEM) were used to evaluate safety of membrane LNG storage tanks. In this study, structural safety evaluation results via FEM analysis showed that both membrane type and full-containment type cryogenic LNG storage tanks with 140,000 $m^3$ capacity were equivalently safe in terms of strength safety and leakage safety of a storage tank system. Also, Fault Tree Analysis (FTA) was used to improve the safety of membrane LNG storage tanks and membrane LNG tanks were modified by adding three safety equipments: impact absorber structure for the low part of the membrane, the secondary barrier to diminish the thermal stress of the corner part of the outer tank, and a pump catcher in case of falling of a pump. Consequently, the safety of the modified membrane LNG storage tanks were proved to be equivalent to that of full-containment LNG storage tanks.

• Steel and Composite Structures
• /
• v.48 no.1
• /
• pp.43-57
• /
• 2023

The impacts of waste tire rubber (WTR) on the bending conduct of reinforced concrete beams (RCBs) are investigated in visualization of experimental tests and 3D finite element model (FEM) using both ANSYS and SAP2000. Several WTR rates are used in total 4 various full scale RCBs to observe the impact of WTR rate on the rupture and bending conduct of RCBs. For this purpose, the volumetric ratios (Vf) of WTR were chosen to change to 0%, 2.5%, 5% and 7.5% in the whole concrete. In relation to experimental test consequences, bending and rupture behaviors of the RCBs are observed. The best performance among the beams was observed in the beams with 2.5% WTR. Furthermore, as stated by test consequences, it is noticed that while WTR rate in the RCBs is improved, max. bending in the RCBs rises. For test consequences, it is clearly recognized as WTR rate in the RCB mixture is improved from 0% to 2.5%, deformation value in the RCB remarkably rises from 3.89 cm to 7.69 cm. This consequence is markedly recognized that WTR rates have a favorable result on deformation values in the RCBs. Furthermore, experimental tests are compared to 3D FEM consequences via using ANSYS software. In the ANSYS, special element types are formed and nonlinear multilinear misses plasticity material model and bilinear misses plasticity material model are chosen for concrete and compression and tension elements. As a consequence, it is noticed that each WTR rates in the RCBs mixture have dissimilar bending and rupture impacts on the RCBs. Then, to observe the impacts of WTR rate on the constructions under near-fault ground motions, a reinforced-concrete building was modelled via using SAP2000 software using 3-D model of the construction to complete nonlinear static analysis. Beam, column, steel haunch elements are modeled as nonlinear frame elements. Consequently, the seismic impacts of WTR rate on the lateral motions of each floor are obviously investigated particularly. Considering reduction in weight of structure and capacity of the members with using waste tire rubber, 2.5% of WTR resulted in the best performance while the construction is subjected to near fault earthquakes. Moreover, it is noticeably recognized that WTR rate has opposing influences on the seismic displacement behavior of the RC constructions.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.2
• /
• pp.169-177
• /
• 2017

In this paper, classification of spall and crack faults of gear teeth is studied by applying the ensemble empirical mode decomposition(EEMD) for the gear transmission error(TE). Finite element models of the gears with the two faults are built, and TE is obtained by simulation of the gears under loaded contact. EEMD is applied to the residuals of the TE which are the difference between the normal and faulty signal. From the result, the difference of spall and crack faults are clearly identified by the intrinsic mode functions(IMF). A simple test bed is installed to illustrate the approach, which consists of motor, brake and a pair of spur gears. Two gears are employed to obtain the TE for the normal, spalled, and cracked gears, and the type of the faults are separated by the same EEMD application process. In order to quantify the results, crest factors are applied to each IMF. Characteristics of spall and crack are well represented by the crest factors of the first and the third IMF, which are used as the feature signals. The classification is carried out using the Bayes decision theory using the feature signals acquired through the experiments.

• Tunnel and Underground Space
• /
• v.20 no.6
• /
• pp.475-490
• /
• 2010

The analysis of slope stability was performed from seven sites among total eleven sites of waste rock which are divided into two objects (mullock-pile and rock mass) according to the location of dumping-dropping point in L limestone Mine. The analysis of circular failure using Bishop's simplified method and the finite element method for mullock-pile slopes were adopted. For rock mass slopes, identification of failure modes on stereonet projection was determined, thereby limit equilibrium analysis was applied to obtain the safety factor of slopes and the finite element method was used to understand overall behavior of slope. Phi-c reduction method was used to calculate the safety factor of slopes through the finite element method. In mullock-pile slope of zone D and rock slopes of zone F and G, the assurance of slope stability was difficult, and the plans to assure the stability of slopes were proposed on the basis of the analysis of slopes at disposal sites of waste rock. Therefore, the method of piling with waste rock by dozer pushing after dumping for mullock-pile slope of zone D is required, and the method of piling after moving to the place which has no fault zone for rock slope of zone F and G is recommended.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2000.11b
• /
• pp.227-235
• /
• 2000

Agricultural products are easily deformable its shape because of some external forces. However, these force behavior is difficult to measure quantitatively. Until now, many researches on the mechanical property was performed with various methods such as material testing, chemical analysis and non-destructive methods. In order to investigate force behavior on the cellular unit of agricultural products, electro-microscope based 3D image processing method will contribute to analysis of plant cells behavior. Before image measurement of plant cells, plant sample was cut off cross-sectioned area in a size of almost 300-400 ${\mu}$ m units using the micron thickness device, and some of preprocessing procedure was performed with fixing and dyeing. However, the wall structure of plant cell is closely neighbor each other, it is necessary to separate its boundary pixel. Therefore, image merging and shrinking algorithm was adopted to avoid disconnection. After then, boundary pixel was traced through thinning algorithm. Each image from the electro-microscope has a information of x,y position and its height along the z axis cross sectioned image plane. 3D image was constructed using the continuous image combination. Major feature was acquired from a fault image and measured area, thickness of cell wall, shape and unit cell volume. The shape of plant cell was consist of multiple facet shape. Through this measured information, it is possible to construct for structure shape of unit plant cell. This micro unit image processing techniques will contribute to the filed of agricultural mechanical property and will use to construct unit cell model of each agricultural products and information of boundary will use for finite element analysis on unit cell image.

• Structural Engineering and Mechanics
• /
• v.69 no.2
• /
• pp.221-230
• /
• 2019

In this paper, shear behavior of non-persistent joint surrounded in concrete and gypsum layers has been investigated using experimental test and numerical simulation. Two types of mixture were prepared for this study. The first type consists of water and gypsum that were mixed with a ratio of water/gypsum of 0.6. The second type of mixture, water, sand and cement were mixed with a ratio of 27%, 33% and 40% by weight. Shear behavior of a non-persistent joint embedded in these specimens is studied. Physical models consisting of two edge concrete layers with dimensions of 160 mm by 130 mm by 60 mm and one internal gypsum layer with the dimension of 16 mm by 13 mm by 6 mm were made. Two horizontal edge joints were embedded in concrete beams and one angled joint was created in gypsum layer. Several analyses with joints with angles of $0^{\circ}$, $30^{\circ}$, and $60^{\circ}$ degree were conducted. The central fault places in 3 different positions. Along the edge joints, 1.5 cm vertically far from the edge joint face and 3 cm vertically far from the edge joint face. All samples were tested in compression using a universal loading machine and the shear load was induced because of the specimen geometry. Concurrent with the experiments, the extended finite element method (XFEM) was employed to analyze the fracture processes occurring in a non-persistent joint embedded in concrete and gypsum layers using Abaqus, a finite element software platform. The failure pattern of non-persistent cracks (faults) was found to be affected mostly by the central crack and its configuration and the shear strength was found to be related to the failure pattern. Comparison between experimental and corresponding numerical results showed a great agreement. XFEM was found as a capable tool for investigating the fracturing mechanism of rock specimens with non-persistent joint.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.20 no.5
• /
• pp.486-491
• /
• 2010

In this paper, it is identified that high-level vibration of the single phase main power transformers shut down due to the mechanical fault. vibration sources of the SPR in the transformer's are identified and the SPR vibrations are reduced by structural modification. For vibration characteristic identification, vibration signals were measured with an accelerometer when the transformer is driving. These signals are presented in a FFT analysis in order to find the dependency of frequency components on the transformer. From finite element analyses and some experiments, it is also found that resonances occur because the natural frequencies of the SPR exist in usual driving range. To shift the natural frequencies outside the driving range, the SPR is modified by increasing stiffness. It is verified that considerable amounts of vibration are reduced by the structural modification.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.11 no.4
• /
• pp.25-31
• /
• 2007

For areas such as the Korean Peninsula, which have moderate seismic activity but no available records of strong ground motion, synthetic seismograms can be used to evaluate ground motion without waiting for a strong earthquake. Such seismograms represent the estimated ground motions expected from a set of possible earthquake scenarios. Local site effects are especially important in assessing the seismic hazard and possible ground motion scenarios for a specific fault. The earthquake source and rupture dynamics can be described as a two-step process of rupture initiation and front propagation controlled by a frictional sliding mechanism. The seismic wavefield propagates through heterogeneous geological media and finally undergoes near-surface modulations such as amplification or deamplification. This is a complex system in which various scales of physical phenomena are integrated. A unified approach incorporates multi-scale problems of dynamic rupture, radiated wave propagation, and site effects into an all-in-one model using a three-dimensional, fourth-order, staggered-grid, finite-difference method. The method explains strong ground motions as products of complex systems that can be modified according to a variety of fine-scale rupture scenarios and friction models. A series of such deterministic earthquake scenarios can shed light on the kind of damage that would result and where it would be located.

• Journal of IKEEE
• /
• v.9 no.2 s.17
• /
• pp.143-151
• /
• 2005

Finite failure NHPP models proposed in the literature exhibit is either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. For the sake of proposing shape parameter of the Gamma family distribution, used the special pattern. Data set, where the underlying failure process could not be adequately described by the knowing models, which motivated the development of the Gamma or Weibull model and Gompertz model. Analysis of failure data set that led us to the Gamma or Weibull model and Gompertz model using arithmetic and Laplace trend tests, bias tests was presented in this Paper.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.394-394
• /
• 2009

Owing to the increasing number of intelligent homes(or called Smart home), the corresponding cost is much higher. Low voltage circuit breakers are widely used in the intelligent homes to interrupt fault current rapidly and to assure the reliability of the power supply. The distribution of magnetic field induced by arc current in the contact system of molded case circuit breaker(hereafter MCCB) depends on the shape, arrangement, and kinds of material of arc runner. This paper is focused on understanding the interrupting capability, more specifically of the arc runner, based on the shape of the contact system in the current MCCB. The magnetic driving force was calculated by using the flux densities induced by the arc current, which are obtained by three-dimensional finite element method. There is a need to assure that the optimum design required to analyze the electromagnetic forces of the contact system generated by current and the flux density be present. This is paper present our computational analysis on contact system in MCCB.