• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.6C
• /
• pp.255-263
• /
• 2010

This paper investigates the effects of tunnelling-induced ground movements on nearby structures, considering soil-structure interactions of different construction (ground loss) and soil characteristics. The response of four-story block structures, which are subjected to tunnelling-induced ground movements, has been investigated in different construction (ground loss) and soil conditions using numerical analysis. The structures for numerical analysis has been modelled using Discrete Element Method (DEM) to have real cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The response of four-story block structures has been investigated with a ground movement magnitude and compared in terms of construction (ground loss) and soil conditions considering the magnitude of deformations and cracks in structures. In addition, the damage levels, which are possibly induced in structures, has been provided in terms of construction (ground loss) and soil conditions using the state of strain damage estimation criterion (Son and Cording, 2005). The results of this study will provide a background for better understandings for controlling and minimizing building damage on nearby structures due to tunnelling-induced ground movements.

• Textile Coloration and Finishing
• /
• v.1 no.1
• /
• pp.54-62
• /
• 1989

The woven fabric composed of nylon 6 filaments was treated with aqueous solutions (20, 30, 40, 50, 60%) of formic acid at 3$0^{\circ}C$ for 10 minutes under unrestrained condition, and the shrinkage behavior and some kinds of properties were examined. The shrinkages of the constituent yarns and fabric were increased with formic acid concentration, but they were lower than that of the original filaments because of fabric-structural factors. And the shrinkage of the warp was lower than that of the weft because of the residual stress from weaving process. By the restraint forces such as fabric-structural factors and residual stress, the constituent filaments were damaged partially at 60% of formic acid concentration and the degree of damage on the warp was greater than on the weft. And though the fabric count were increased overall, the spacing between the warps was decreased prior to the weft and eliminated nearly at 60% of formic acid concentration. The thickness, tensile strength, elongation, and handle value of fabric were increased overall with formic acid concentration excepting that the tensile strength for both the warp and weft directions and the elongation for the warp direction were decreased instead by the damage of yarns. But the crease recovery was decreased except the case of the weft direction at 60% of formic acid concentration.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.6
• /
• pp.753-760
• /
• 2013

The hydrogen embrittlement of metallic materials is an important issue from the viewpoint of structural integrity. In this regard, the estimation of mechanical properties and fracture toughness under hydrogen conditions provides very important data. This study provides an experimental validation of the approach for simulating the small punch of Inconel 617 using finite element damage analysis, as recently proposed by the authors, and applies an inverse method for the determination of the constitutive tensile behavior of materials. The mechanical properties obtained from the inverse method are compared with those obtained from the tensile test and validated. The mechanical properties and fracture toughness are predicted by using the inverse method and finite element damage analysis.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.4
• /
• pp.121-125
• /
• 2018

This paper presents the assessment of 7-wire strand monitoring using acoustic emission technique for bridges. 7-wire strand is widely used construction materials to provide additional tensile force to bridges. PSC (PreStressed Concrete) bridge and cable-stayed bridge are representatives for such cases. However, as the bridge aging progresses recently, corrosion problems of strand are emerging. For this reason, various NDT (Non-Destructive Test) methods for cable inspection are being studied and applied to the field. One of the NDT methods, acoustic emission technique, is known as an effective technique to detect cable damage and breakage. In this study, to evaluate the applicability of acoustic emission technique to bridges, acoustic emission signals according to damage of the strand were acquired and analyzed by tensile test. Moreover, The optimal AE sensor type was selected for field application. As a result, it is considered that the acoustic emission technique will be able to detect corrosion breakage and signs of rupture.

• Nuclear Engineering and Technology
• /
• v.47 no.3
• /
• pp.340-350
• /
• 2015

This paper proposes strain-based acceptance criteria for assessing plastic instability of the safety class 1 nuclear components made of ferritic steel during level D service loads. The strain-based criteria were proposed with two approaches: (1) a section average approach and (2) a critical location approach. Both approaches were based on the damage initiation point corresponding to the maximum load-carrying capability point instead of the fracture point via tensile tests and finite element analysis (FEA) for the notched specimen under uni-axial tensile loading. The two proposed criteria were reviewed from the viewpoint of design practice and philosophy to select a more appropriate criterion. As a result of the review, it was found that the section average approach is more appropriate than the critical location approach from the viewpoint of design practice and philosophy. Finally, the criterion based on the section average approach was applied to a simplified reactor pressure vessel (RPV) outlet nozzle subject to SSE loads. The application shows that the strain-based acceptance criteria can consider cumulative damages caused by the sequential loads unlike the stress-based acceptance criteria and can reduce the overconservatism of the stress-based acceptance criteria, which often occurs for level D service loads.

• Journal of the Korean Geotechnical Society
• /
• v.36 no.8
• /
• pp.35-47
• /
• 2020

For permanent anchors used for slope reinforcement, bearing capacity and durability should be secured during the period of use. However, according to recent domestic and foreign studies, phenomena such as tension fractures, damage to anchorages, deformation and damage to slope and reduction of residual load over time have been reported along the long-term behavior of the anchors. These problems are expected to increase in the future, which will inevitably lead to problems such as increasing maintenance costs and relevant facility collapse. It is necessary to improve maintenance procedures and methods of ground anchors more practically. In this study, the problems and limitations of domestic maintenance methods were analyzed by conducting a literature study, and the measurement data of load cells installed on the install ground anchors were analyzed to determine the change in the residual load with regard to the elapsed date of the anchors. Based on the results, the effect of the construction conditions of anchors and the soil compositions on the increase and decrease of load were identified.

• Journal of the Korean Applied Science and Technology
• /
• v.39 no.2
• /
• pp.294-302
• /
• 2022

This study attempted to investigate the effect of improving damaged hair by preparing a hair improving agent with basil oil and applying it to damaged hair. An experimental material was added to a perm base agent containing 0 g, 3 g, 6 g, 9 g of basil oil to prepare the preparation. It was applied to sample hair bleached at 8 levels with the prepared formulation. Each sample and damaged hair were measured and analyzed. The measurement method measured tensile strength, absorbance and gloss using methylene blue to determine the effect of improving maternal quality. Statistical analysis was conducted on the reliability of the study results. Studies have shown that all samples with basil oil have higher tensile strength than damaged hair. As a result of the absorbance analysis using methylene blue, it was found that the absorbance was lower than that of damaged hair in all samples. Gloss measurement showed that all samples showed increased luster compared to damaged hair. In conclusion, basil oil was found to improve damaged hair. In the future, research on various types of oil and research methods is needed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.4C
• /
• pp.153-162
• /
• 2009

This paper investigates the effects of excavation-induced ground movements on nearby structures, considering soil-structure interactions of different soil and structural characteristics. The response of four and two-story block structures, which are subjected to excavation-induced advancing ground movements, are investigated in different soil conditions using numerical analysis. The structures for numerical analysis are modelled to have cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The response of four and two-story block structures are investigated with advancing ground movement phases and compared with the response of structures which are subjected to excavation-induced total ground movement. The response of structures is compared among others in terms of the magnitude and shape of deformations and cracks in structures for different structure and ground conditions. The results of the comparison provide a background for better understandings for controlling and minimizing building damage on nearby structures due to excavation-induced ground movements.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.31 no.11
• /
• pp.1565-1573
• /
• 2007

This research was aimed to investigate the effect of $K_2CO_3$ instead of NaOH on retting of the kenaf bast. We examined the relationship between separation of fiber bundle and tensile strength besides observing the color, handle and cross sectional view for the kenaf fiber retted with various concentration(100, 150, 200, 250, 500, 1000mmol) of $K_2CO_3$ and double retted with 0.5% pectinase after $K_2CO_3$ retting. The one retted on low $K_2CO_3$ concentration, $150{\sim}200mmol$, showed the best result on color, handle and luster. The separation of fiber bundle started even at the low $K_2CO_3$ concentration, 100mmol, and as the $K_2CO_3$ concentration was higher, the size of the fiber bundle was smaller. In the case of 1000mmol, the fiber bundle became irregular, but they were breaking up into certain way. Regardless of $K_2CO_3$ concentration, the thinner the diameters of the kenaf fiber bundle, the stronger tensile strength have appeared. This result corresponds with the result of cross sectional view. Retting on $150{\sim}200mmol\;K_2CO_3$ concentration was most effective on fiber bundle#s separation and tensile strength. The one with double retted with 0.5% pectinase after $K_2CO_3$ retting showed very small size of fiber bundle and low tensile strength compare to the one just retted on $K_2CO_3$. This decrease of tensile strength seem to be related to damage of the fiber resulted by excessive fibrillation.

• Steel and Composite Structures
• /
• v.46 no.1
• /
• pp.53-73
• /
• 2023

Man-made structure materials like concrete usually contain inclusions. These inclusions affect the mechanical properties of concrete. In this investigation, the influence of inclusion length and inclination angle on three-dimensional failure mechanism of concrete under uniaxial compression were performed using experimental test and numerical simulation. Approach of acoustic emission were jointly used to analyze the damage and fracture process. Besides, by combining the stress-strain behavior, quantitative determination of the thresholds of crack stress were done. concrete specimens with dimensions of 120 mm × 150 mm × 100 mm were provided. One and two holes filled by gypsum are incorporated in concrete samples. To build the inclusion, firstly cylinder steel tube was pre-inserting into the concrete and removing them after the initial hardening of the specimen. Secondly, the gypsum was poured into the holes. Tensile strengths of concrete and gypsum were 2.45 MPa and 1.5 MPa, respectively. The angle bertween inclusions and axial loadind ary from 0 to 90 with increases of 30. The length of inclusion vary from 25 mm to 100 mm with increases of 25 mm. Diameter of the hole was 20 mm. Entirely 20 various models were examined under uniaxial test. Simultaneous with experimental tests, numerical simulation (Particle flow code in two dimension) were carried out on the numerical models containing the inclusions. The numerical model were calibrated firstly by experimental outputs and then failure behavior of models containing inclusions have been investigated. The angle bertween inclusions and axial loadind vary from 0 to 90 with increases of 15. The length of inclusion vary from 25 mm to 100 mm with increases of 25 mm. Entirely 32 various models were examined under uniaxial test. Loading rate was 0.05 mm/sec. The results indicated that when inclusion has occupied 100% of sample thickness, two tensile cracks originated from boundaries of sample and spread parallel to the loading direction until being integrated together. When inclusion has occupied 75% of sample thickness, four tensile cracks originated from boundaries of sample and spread parallel to the loading direction until being integrated together. When inclusions have occupied 50% and 25% of sample thickness, four tensile cracks originated from boundaries of sample and spread parallel to the loading direction until being integrated together. Also the inclusion was failed by one tensile crack. The compressive strength of samples decease with the decreases of the inclusions length, and inclusion angle had some effects on that. Failure of concrete is mostly due to the tensile crack. The behavior of crack, was affected by the inclusion length and inclusion number.