• Steel and Composite Structures
• /
• v.33 no.1
• /
• pp.143-162
• /
• 2019

A number of desirable characteristics concerning excellent durability, aesthetics, recyclability, high ductility and fire resistance have made stainless steel a preferred option in engineering practice. However, the relatively high initial cost has greatly restricted the application of stainless steel as a major structural material in general construction. This drawback can be partially overcome by introducing composite stainless steel-concrete structures, which provides a cost-efficient and sustainable solution for future stainless steel construction. This paper presents a preliminary numerical study on stainless steel-concrete composite beam-to-column joints with bolted flush endplates. In order to ensure a consistent corrosion resistance within the whole structural system, all structural steel components were designed with austenitic stainless steel, including beams, columns, endplates, bolts, reinforcing bars and shear connectors. A finite element model was developed using ABAQUS software for composite beam-to-column joints under monotonic and symmetric hogging moments, while validation was performed based on independent test results. A parametric study was subsequently conducted to investigate the effects of several critical factors on the behaviour of composite stainless steel joints. Finally, comparisons were made between the numerical results and the predictions by current design codes regarding the plastic moment capacity and the rotational stiffness of the joints. It was concluded that the present codes of practice generally overestimate the rotational stiffness and underestimate the plastic moment resistance of stainless steel-concrete composite joints.

• Steel and Composite Structures
• /
• v.29 no.5
• /
• pp.635-645
• /
• 2018

Beam-column joints play a significant role in static and dynamic performances of reinforced concrete frame structures. This study contributes a numerical approach of topologically optimal design of carbon fiber reinforced plastics (CFRP) to retrofit existing beam-column connections with crack patterns. In recent, CFRP is used commonly in the rehabilitation and strengthening of concrete members due to the remarkable properties, such as lightweight, anti-corrosion and simplicity to execute construction. With the target to provide an optimal CFRP configuration to effectively retrofit the beam-column connection under semi-failure situation such as given cracks, extended finite element method (X-FEM) is used by combining with multi-material topology optimization (MTO) as a mechanical description approach for strong discontinuity state to mechanically model cracked structures. The well founded mathematical formulation of topology optimization problem for cracked structures by using multiple materials is described in detail in this study. In addition, moved and regularized Heaviside functions (MRHF), that have the role of a filter in multiple materials case, is also considered. The numerical example results illustrated in two cases of beam-column joints with stationary cracks verify the validity, benefit and supremacy of the proposed method.

• Journal of Korean Association for Spatial Structures
• /
• v.19 no.3
• /
• pp.41-50
• /
• 2019

The stone pagoda continued to be damaged by weathering and corrosion over time, and natural disasters such as earthquake are accelerating the destruction of cultural properties. Stone pagoda has discontinuous structure behavior and is very vulnerable to the seismic load acting in lateral direction. It is necessary to analyze various design variables as the contact surface characteristics play an important role in the dynamic behavior of stone pagodas. For this purpose, contact surface characteristics of stone pagoda can be classified according to surface roughness and filler type, and representative model is selected and structural modeling and analysis are performed using the discrete element method. Also, the seismic load according to the repetition period is calculated and the dynamic analysis is performed considering the discontinuous characteristics of the stone pagoda. Finally, the seismic behavior characteristics can be analyzed by the evaluation of stresses, displacements and structural safety.

• Nuclear Engineering and Technology
• /
• v.51 no.6
• /
• pp.1596-1609
• /
• 2019

The fuel rod performance has great importance for the safety and economy of an operating reactor. The fuel rod performance analysis code, which considers the thermal-mechanical response and irradiation effects of fuel rod, is usually developed in order to predict fuel rod performance accurately. The FRIPAC (${\underline{F}}uel$ ${\underline{R}}od$ ${\underline{I}}ntegral$ ${\underline{P}}erformance$ ${\underline{A}}nalysis$ ${\underline{C}}ode$) is such a fuel rod performance analysis code that has been developed recently by China Nuclear Power Technology Research Institute Co. Ltd. The code aims at the computational simulation of the Pressurized Water Reactor fuel rod behavior for both steady-state and power ramp condition. A brief overview of FRIPAC is presented including the computational framework and the main behavioral models. Validation of the code is also presented and it focuses on the fuel rod behavior including fuel center temperature, fission gas release, rod internal pressure/internal void volume, cladding outer diameter and cladding corrosion thickness. The validation is based on experimental data from several international projects. The validation results indicate that FRIPAC is an accurate and reliable fuel rod performance analysis code because of the satisfactory comparison results between the experimental measurements and the code predictions.

• Korean Journal of Materials Research
• /
• v.31 no.8
• /
• pp.471-479
• /
• 2021

The electrochemical reaction between lead borate glass frit doped with Sn metal filler and Ni-Cr wire of a J-type resistor during a term of Joule heating is investigated. The fusing behavior in which the Ni-Cr wire is melted is not observed for the control group but measured for the Sn-doped specimen under 30 V and 500 mA. The Sn-doped lead borate glass frit shows a fusing property compared with other metal-doped specimens. Meanwhile, the redox reaction significantly contributes to the fusing behavior due to the release of free electrons of the metal toward the glass. The electrons derived from the glass, which used Joule heat to reach the melting point of Ni-Cr wire, increase with increasing corrosion rate at interface of metal/glass. Finally, the confidence interval is 95 ± 1.95₉ %, and the adjusted regression coefficient, R in the optimal linear graph, is 0.93, reflecting 93% of the data and providing great potential for fusible resistor applications.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.19 no.1
• /
• pp.9-27
• /
• 2021

As an example of research activities in decontamination for decommissioning, new data are presented on the options for corrosion layer dissolution during the decommissioning decontamination, or persulfate regeneration for decontamination solutions re-use. For the management of spent decontamination solutions, new method based on solvent extraction of radionuclides into ionic liquid followed by electrodeposition of the radionuclides has been developed. Fields of applications of composite inorganic-organic absorbers or solid extractants with polyacrylonitrile (PAN) binding matrix for the treatment of liquid radioactive waste are reviewed; a method for americium separation from the boric acid containing NPP evaporator concentrates based on the TODGA-PAN material is discussed in more detail. Performance of a model of radionuclide transport, developed and implemented within the GoldSim programming environment, for the safety studies of the LLW/ILW repository is demonstrated on the specific case of the Richard repository (Czech Republic). Continuation and even broadening of these activities are expected in connection with the approaching end of the lifespan of the first blocks of the Czech NPPs.

• Geomechanics and Engineering
• /
• v.29 no.3
• /
• pp.229-236
• /
• 2022

In this study, a model experiment and field experiment was conducted to introduce the optimal tensile force when constructing a non-open cut tunnel according to the ground conditions of sandy soil. CMR (Concrete Modular Roof) method is economical because of the high precision and excellent durability, and corrosion resistance, and the inserted parts can be used as the main structure of a tunnel. In addition the CMR method has a stable advantage in interconnection because the concrete beam is press-fitted compared to the NTR (New Tubular Roof) method, and the need for quality control can be minimized. The ground conditions were corrected by adjusting the relative density of sandy soil during the construction of non-open cut tunnels, and after introducing various tensile forces, the surface settlement according to excavation was measured, and the optimal tensile force was derived. As a result of the experiment, the amount of settlement according to the relative density was found to be minor. Furthermore, analysis of each tensile force based on loose ground conditions resulted in an average decrease of approximately 22% in maximum settlement when the force was increased by 0.8 kN per segment. Considering these results, it is indicated that more than 2.0 kN tensile force per segment is recommended for settlement of the upper ground.

• Journal of Auto-vehicle Safety Association
• /
• v.14 no.1
• /
• pp.32-38
• /
• 2022

In the automobile industry, lamps are frequently used as a mean to emphasize each company's brand identity. Therefore, many detailed design models have emerged in order to realize a differentiated image in preparation for competitive vehicles. Among them, the design of a multi compartment lighting image concept that realizes light divided in multiple space also being introduced by various manufacturers. In this study, in order to solve the problem of cost and weight rise that the existing multi compartment image lamp has, using TRIZ method such as functional analysis modeling and trimming. Through this process, an idea to minimize cost and weight was derived. As the idea was designed in detail, the formation of light did not go as desired, and the diffusion of light also proceeded differently than intended. In order to overcome this problem, a new concept of corrosion and diffusion structure was applied. Eventually, it overcomes various problems and successfully applied it to a real vehicle. The idea was actually reflected in the "Santa Fe" model. Later, the media focused on the lamps to which the idea was applied, and contributed to the sale of a large number of vehicles by providing consumers with a new light sensibility. During the research process, it was possible to secure a number of patents and knowledge of new design concepts.

• Nuclear Engineering and Technology
• /
• v.55 no.5
• /
• pp.1892-1900
• /
• 2023

A protective oxide layer forms on the material surfaces of a Nuclear Power Plant during operation due to high temperature. These oxides can host radionuclides, the activated corrosion products of fission products, resulting in decommissioning workers' exposure. These deposited oxides are iron oxides such as Fe₃O₄, Fe₂O₃ and mixed ferrites such as nickel ferrites, chromium ferrites, and cobalt ferrites. Developing a new chemical decontamination technology for domestic CANDU-type reactors is challenging due to variations in oxide compositions from different structural materials in a Pressurized Water Reactor (PWR) system. The Korea Atomic Energy Research Institute (KAERI) has already developed a chemical decontamination process for PWRs called 'HyBRID' (Hydrazine-Based Reductive metal Ion Decontamination) that does not use organic acids or organic chelating agents at all. As the first step to developing a new chemical decontamination technology for the Pressurized Heavy Water Reactor (PHWR) system, we investigated magnetite dissolution behaviors in various HyBRID inorganic acidic solutions to assess their applicability to the PHWR reactor system, which forms a thicker oxide film.

• Journal of Korean Society of Environmental Engineers
• /
• v.38 no.2
• /
• pp.87-95
• /
• 2016

Turbidity is a key indicator to the user that the 'Discolored Water' phenomenon known to be caused by corrosion of the pipeline in the water supply system. 'Discolored Water' is defined as a state with a turbidity of the degree to which the user visually be able to recognize water. Therefore, this study used data mining techniques in order to estimate turbidity changes in water supply system. Decision tree analysis was applied in data mining techniques to develop estimation models for turbidity changes in the water supply system. The pH and residual chlorine dataset was used as variables of the turbidity estimation model. As a result, the case of applying both variables(pH and residual chlorine) were shown more reasonable estimation results than models only using each variable. However, the estimation model developed in this study were shown to have underestimated predictions for the peak observed values. To overcome this disadvantage, a high-pass filter method was introduced as a pretreatment of estimation model. Modified model using high-pass filter method showed more exactly predictions for the peak observed values as well as improved prediction performance than the conventional model.