• Nuclear Engineering and Technology
• /
• v.56 no.9
• /
• pp.3884-3897
• /
• 2024

This study investigates the creep behavior of bentonite-sand mixtures as potential buffer materials for low-level radioactive waste (LLW) repositories, with a specific case study in Taiwan. To assess the long-term hydro-mechanical properties, constant-volume swelling pressure, hydraulic conductivity, strain-controlled shear, and stress-controlled shear tests were conducted on MX80 and KV1 bentonite-sand mixtures. The experimental results indicate that MX80-sand 70/30 mixtures are prioritized as the buffer materials with 2.10 MPa swelling pressure and 1 × 10^-13 m/s hydraulic conductivity. However, the shear strength of mixtures was reduced by almost 50 % when fully saturated. Furthermore, this study proposed a novel stress-controlled direct shear apparatus to retrieve the creep model parameters. The numerical method based on the creep model efficiently supports and simulates the saturation process and creep displacement. The finite element method (FEM) result predicts that the buffer of both bentonite-sand mixtures will achieve an average degree of saturation of 95 % at the end of three decades and full saturation in 100 years. The simulated creep displacement results at key nodes suggest that both top and bottom parts in the buffer, assembled from MX80-sand 70/30 mixtures or KV1-sand 70/30 mixtures, will have almost equivalent values of 4 mm in the horizontal and 2 mm in the vertical directions eventually.

• Geotechnical Engineering
• /
• v.13 no.3
• /
• pp.101-122
• /
• 1997

A spiting reinforcement system is composed of a series of radially installed reinforcing spites along the perimeter of the tunnel opening ahead of excavation. The reinforcing spill network is extended into the in-situ soil mass both radially and longitudinally The sailing reinforcement system has been successfully used for the construction of underground openings to reinforce weak rock formations on several occasions. The application of this spiting reinforcement system is currently extended to soft ground tunneling in limited occasions because of lack of reliable analysis and design methods. A method of threetimensional limit equilibrium stability analysis of the smile-reinforced shallow tunnel in soft ground is presented. The shape of the potential failure wedge for the case of smile-reinforced shallow tunnel is assumed on the basis of the results of three dimensional finite element analyses. A criterion to differentiate the spill-reinforced shallow tunnel from the smile-reinforced deep tunnel is also formulated, where the tunnel depth, soil type, geometry of the tunnel and reinforcing spites, together with soil arching effects, are considered. To examine the suitability of the proposed method of threedimensional stability analysis in practice, overall stability of the spill-reinforced shallow tunnel at facing is evaluated, and the predicted safety factors are compared with results from twotimensional analyses. Using the proposed method of threetimensional limit equilibrium stability analysis of the smile-reinforced shallow tunnel in soft ground, a parametric study is also made to investigate the effects of various design parameters such as tunnel depth, smile length and wadial spill spacing. With slight modifications the analytical method of threeiimensional stability analysis proposed may also be extended for the analysis and design of steel pipe reinforced multi -step grouting technique frequently used as a supplementary reinforcing method in soft ground tunnel construction.

• Journal of Bio-Environment Control
• /
• v.18 no.3
• /
• pp.192-199
• /
• 2009

This study was conducted to find proper structural reinforcement methods for the 4.5m-high (eaves height) 1-2W type plastic greenhouse. 3D finite element analysis was used to analyze the steel-tube structure. The 4.5m-high 1-2W type plastic greenhouse was modified by welding 1.5m-long steel-pipes into a 3.0m-tall columns of the standard 1-2W type plastic greenhouse. This remodeling method is widely used in Korea with farmer's discretion to increase the production when they grow paprika. But it is not based on the quantitative structural analysis. The proposed reinforcement methods were proved to stand against the design wind velocity of $40m{\cdot}s^{-1}$ and snow depth of 40cm. It strongly implies that the cross beam between side columns and wind resistance walls, and the lattice type cross beam should be good reinforcements to improve the structural safety of the elevated eaves height plastic greenhouse.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.27 no.4
• /
• pp.58-66
• /
• 1990

A series of test was performed measuring the failure strength and failure mode of Gr/Pi, $[0^{\circ}/45^{\circ}/90^{\circ}/-45^{\circ}]_s$ laminate containing a single pin loaded hole. The finite element method is applied to calculate the stress distribution in the laminates, then the failure load and the failure mode were predicted by means of the characteristic length. 12 different geometric variations were developed to analyze the effects of the ratio of specimen width to hole diameter (W/d) and ratio of edge distance to hole diameter (L/d). X-Ray of NDE methods were utilized in finding out the initial defects, damage and the fracture mechanism, and SEM(Scanning Electron Microscopes) was used the evaluation of the fracture mechanism and crack propagation around hole under tension pin loading. $[0^{\circ}/45^{\circ}/90^{\circ}/-45^{\circ}]_s$ laminate are found to be most sensitive to W/d but not so influenced by L/d. The failure mode and tensile strength predicted by the model show agreement with experiment data for pin loading bolted jointed test except range of $L/d{\leqq}3$.

• Journal of the Korea Concrete Institute
• /
• v.28 no.6
• /
• pp.695-702
• /
• 2016

This paper presents compression capacity of transfer system in pilotis subjected to axial load. Recently, transfer system is usually used in low floors of wall-typed apartments when members' sections are suddenly changed between upper walls and bottom columns. It can help transfer loads from the walls to the columns. Especially, a transfer girder system is usually used as one of transfer systems applied to a pilotis. However, the transfer girder system has low constructability and economics. Therefore, the other transfer system with transfer slab was suggested and has been studied. In this paper, to evaluate the compression capacity of transfer slab, tests were conducted on pilotis transfer slab systems subjected to axial load. First of all, two specimens were determined by FEM. The main parameter is length of the bottom columns. The lengh of the bottom columns were 40% and 50% of length of upper walls in the tranfer slab specimens. Results showed that the compression capacity of piloti transfer systems subjected to axial load was affected by length of bottom columns. The compression capacity is 52% higher than design strength for specimen with the bottom column's length of 40% of length of the upper wall and 46% for specimen with the bottom column's length of 50% of length of the upper wall.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.11
• /
• pp.1139-1145
• /
• 2011

An automated anastomotic ring-pin system consisting of both the anastomotic ring-pin system and the coupler device has eliminated the drawbacks of the suture method. High density polyethylene (HDPE), a material with outstanding biocompatibility and injection molding capability, was used in the ring. SUS316 stainless steel, Ti-6Al-4Nb, Ti-6Al-4V, and unalloyed titanium were used in FEM simulations of the micropin. The authors categorized the microvascular anastomotic ring micropins into short neck (SN) and long neck (LN) groups in order to evaluate the effect of the micropin's fillet radius and neck length on the von Mises stress. The micropins were further divided into those with and without fillet. On the basis of the fillet radius rate (FRR), which represents the rate of change in the von Mises stress with respect to the availability and shape of the fillet, and the neck length rate (NLR), which represents the rate of change in the von Mises stress with respect to changes in the length of the neck within the fillet shape, it can be concluded that the SN-3 neck design is the most stable.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.2 s.31
• /
• pp.171-179
• /
• 1997

The high-tension bolted joints are clamped by the axial force which approaches the yielding strength. The introduced axial force is transmitted to the connection members pass through washer. The transferred load in connections is balanced to the compressive stress of plates, axial force in bolts and the external loads. In this mechanism, the compressive stress and slip load we dominated by the effective stiffness of bolted joints and plates. In general the effective stiffness is specified to product to the effective area and elasticity modulus in connections. In this reason, the conic projection formular which is assumed that the axial force in bolts is distributed to the cone shape and that region is related to the elastic deformation mechanism in connections, was proposed. But it conclude what kind of formula is justified. Therefore in this paper, the fatigue tests are performed to the high tension bolted joints and inspected to the phase on the friction face. And using the FEM and numerical method, it is analyzed and approximated to the compressive stress distribution and its region. Moreover, it is estimated to the effective area and to the relation the friction area to the effective compressive distribution region.

• Journal of Animal Environmental Science
• /
• v.14 no.1
• /
• pp.61-68
• /
• 2008

The roof structural model of liquid manure storage tank was designed to improve a structural safety and an ability of resistance to corrosion by the bad environmental condition with high humidity and high gas concentration. Due to corrosion of a general steel, the 5 years used materials were reduced to one-third of a new material in the result of a bending strength test. Some structural materials were tested to evaluate a strength and an anti-corrosion, and stainless steel pipe (STS439), steel angle with zinc hot dipping, rectangular steel pipe covered with FRP (Fiberglass Reinforced Plastics) resin were selected finally. A stainless steel is more expansive about $3{\sim}5$ times than general structural steel. But its durability under heavy corrosive environment is expected twice as long as general steel. The roof models were designed as closed cone type for each of the three structural materials. In the result of a FEM (Finite Element Method) structural analysis for the developed models, the safe snow depth was higher 2.3 times than a general roof structure, when elements of equal section modulus were used.

• Proceedings of the KOSOMBE Conference
• /
• v.1997 no.11
• /
• pp.245-248
• /
• 1997

Operative interventions for the management of osteonecrosis of the femoral head (ONFH) include core drilling, with or without vascularized fibular bone grafting. Nevertheless, their clinical results have not been consistently satisfactory. Recently, a new surgical procedure that incorporates cementation with polymethylmethacrylate (PMMA) after core drilling has been tried clinically. In this study, a biomechanical analysis using a finite element method(FEM) was undertaken to evaluate surgical methods and their underlying surgical parameter. Our finite element models included five types. They were (1) normal model (Type I), (2) necrotic model (Type II), (3) core decompressed model (Type III). (4) fibular bone grafted model (Type IV), and (5) cemented with PMMA model (Type V). The geometric dimensions of the femur were based on digitized CT-scan data of a normal person. Various physiological loading conditions and surgical penetration depths by the core were used as mechanical variables to study their biomechanical contributions in stress transfer within the femoral head region. In addition. the peak von Mises stress(PVMS) within the necrotic cancellous bone of the femoral head was obtained. The fibular bone grafted method and cementation method provided optimal stress transfer behaviors. Here. substantial increase in the low stress level was observed when the penetration depth was extended to 0mm and 5mm from the subchondral region. Moreover, significant decrease in PVMS due to surgery was observed in the fibular bone grafted method and the cementation method when the penetration depths were extended up to 0 and 5mm from the subchondral region. The drop in PVMS was greater during toe-off than during heel-strike (57% vs. 28% in Type IV and 49% vs. 22% in Type V). Both the vascularized fibular bone grafting method (Type IV) and the new PMMA technique (Type V) appear to be very effective in providing good stress transfer and reducing the peak Von-Mises stress within the necrotic region. Overall results show that fibular bone grafting and cementation methods are quite similar. In light of above results, the new cementation method appears to be a promising surgical alternative or the treatment of ONFH. The use of PMMA for the core can be less prone to surgical complication as opposed to preparation of fibular bone graft and can achieve more immediate fixation between the core and the surrounding region.

• Journal of Sensor Science and Technology
• /
• v.9 no.1
• /
• pp.1-8
• /
• 2000

One of today's very critical and sensitive accurate accelerometer which can be used higher temperature than $200^{\circ}C$ and corrosive environment, is particularly demanded for automotive engine. Because silicon is a material of large temperature dependent coefficient, and the piezoresistors are isolated with p-n junctions, and its leakage current increase with temperature, the performance of the silicon accelerometer degrades especially after $150^{\circ}C$. In this paper, The temperature characteristic of a accelerometer using silicon on insulator (SOI) structure is studied theoretically, and compared with experimental results. The temperature coefficients of sensitivity and offset voltage (TCS and TCO) are related to some factors such as thermal residual stress, and are expressed numerically. Thermal stress analysis of the accelerometer has also been carried out with the finite-element method(FEM) simulation program ANSYS. TCS of this accelerometer can be reduced to control the impurity concentration of piezoresistors, and TCO is related to factors such as process variation and thermal residual stress on the piezoresistors. In real packaging, The avarage thermal residual stress in the center support structure was estimated at around $3.7{\times}10^4Nm^{-2}^{\circ}C^{-1}$ at sensing resistor. The simulated ${\gamma}_{pT}$ of the center support structure was smaller than one-tenth as compared with that of the surrounding support structure.