• Smart Structures and Systems
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• v.29 no.3
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• pp.445-455
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• 2022

Steel anchor bolts are installed in concrete using a variety of methods. One of the most common methods of anchor bolt installation is using epoxy resin as an infill material injected into the drilled hole to act as a bonding material between the steel bolt and the surrounding concrete. Typical design standards assume uniform stress distribution along the length of the anchor bolt accompanied with single crack leading to pull-out failure. Experimental evidence has shown that the steel anchor bolts fail owing to the multiple failure patterns, hence these design assumptions are not realistic. In this regard, the presented research work details the analytical model that takes into consideration multiple micro cracks in the infill material induced via impact loading. The impact loading from the Schmidt hammer is used to evaluate the bond condition bond condition of anchor bolt and the epoxy material. The added advantage of the presented analytical model is that it is able to take into account the various type of end conditions of the anchor bolts such as bent or U-shaped anchors. Through sensitivity analysis the optimum stiffness and shear strength properties of the epoxy infill material is achieved, which have shown to achieve lower displacement coupled with reduced damage to the surrounding concrete. The accuracy of the presented model is confirmed by comparing the simulated deformational responses with the experimental evidence. From the comparison it was found that the model was successful in simulating the experimental results. The proposed model can be adopted by professionals interested in predicting and controlling the deformational response of anchor bolts.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.2
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• pp.145-156
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• 2021

Ultrasonic Nanocrystal Surface Modification (UNSM) is a peening technology that generates elastic-plastic deformation on the material surface to which a static load of a air compressor and a dynamic load of ultrasonic vibration energy are applied by striking the material surface with a strike pin. In the UNSM-treated material, the structure of the surface layer is modified into a nano-crystal structure and compressive residual stress occurs. When UNSM is applied to welds in a reactor coolant system where PWSCC can occur, it has the effect of relieving tensile residual stress in the weld and thus suppressing crack initiation and propagation. In order to quantitatively evaluate the compressive residual stress generated by UNSM, many finite element studies have been conducted. In existing studies, single-path UNSM or UNSM in a limited area has been simulated due to excessive computing time and analysis convergence problems. However, it is difficult to accurately calculate the compressive residual stress generated by the actual UNSM under these limited conditions. Therefore, in this study, a minimum finite element peening analysis area that can reliably calculate the compressive residual stress is proposed. To confirm the validity of the proposed analysis area, the compressive residual stress obtained from the experiment are compared with finite element analysis results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.105-112
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• 2023

Steel fiber reinforced concrete (SFRC) exhibits enhanced strength and superior energy dissipation capacity compared to normal concrete, and it can also reduce crack propagation and fragmentation of concrete even when subjected to blast loads. In this study, the parameters defining failure surface and damage function of the K&C concrete nonlinear model were proposed to be applied for the properties of SFRC in LS-DYNA. Single element analysis has been conducted to validate the proposed parameters in the K&C model, which provided very close simulations on the compressive behavior of SFRC. In addition, blast analysis was performed on SFRC columns with different volume fractions of steel fibers, and the blast resistance of SFRC columns was quantitatively analyzed with Korea Occupational Safety & Health Agency (KOSHA) guidelines.

• Journal of Environmental Policy
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• v.10 no.1
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• pp.27-47
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• 2011

Used as foundation resources for environment improvement and preservation of single-housing residential area by practicing classification of biotope with the concept of ecological area rate applied and performing urban thermal environment prediction simulation. Biotope is classified as seven types according to classification of biotope which is carried out with the concept of ecological area rate applied. The classification is listed below in descending order: building biotope(48.16%), impervious pavement biotope(39.75%), greenspace biotope(6.23%), crack permeable pavement biotope(3.26%), whole surface permeable pavement biotope(2.51%), parts permeable pavement biotope(0.04%). As a result of analysing prediction of variation and characteristics of thermal environment of single-housing residential area, land surface temperature per types of biotope are evaluated as listed below in descending temperature order: impervious pavement biotope > building biotope > greenspace biotope > permeable pavement biotope. In case 2 where vegetated roof hypothetically covers 100% of the roof area, temperature is predicted to be $33.58^{\circ}C$ Max, $23.85^{\circ}C$ Min, and $27.74^{\circ}C$ Avg. which is Approximately $5.19^{\circ}C$ lower than a non-vegetated roof. Average outdoor temperature for case 2 is studied to be $0.18^{\circ}C$ lower than case 1.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.98-106
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• 2011

The deck of steel box girder bridges is composed of deck plate, longitudinal rib, and transverse ribs. The orthotropic steel decks have high possibility to fatigue damage due to numbers of welded connection part, the heavy contact loadings, and the increase of repeated loadings. Generally, the local stress by the repeated loadings of heavy vehicles causes the orthotropic steel deck bridge to fatigue cracks. The increase of traffic volume and heavy vehicle loadings are promoted the possibility of fatigue cracks. Thus, it is important to exactly evaluate the structural behavior of bridge considering the contact loading area of heavy vehicles and real load patterns of heavy trucks which have effects on the bridge. This study estimated the effect of contact area of design loads and real traffic vehicles through the finite element analysis considering the real loading conditions. The finite element analysis carried out 4 cases of loading patterns in the orthotropic steel deck bridge. Also, analysis estimated the influence of contact area of real truck loadings by the existence of diaphragm plate. The result of finite element analysis indicated that single tire loadings of real trucks occurred higher local stress than one of design loadings, and especially the deck plate got the most influence by the single tire loading. It was found that the diaphragm attachment at joint part of longitudinal ribs and transverse ribs had no effects on the improvement of structural performance against fatigue resistance in elastic analysis.

• (The)Study of the Eastern Classic
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• no.37
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• pp.377-410
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• 2009

In the East Asian Confucianism society, Hakmun was aimed to bring human beings and nature into harmony, and to explore a unity between knowledge and conducts. For example, Neo-Confucianism aspired they could explain the human existence and society through a single concept of Iki(理氣, the basic principles and the atmospheric force of nature). In this philosophy, humanics and natural sciences had not been differentiated at all. The East-West cultural interchanges at the beginning of modernity caused a crack in the traditional academic concepts. Through the Hundred Days of Reform(變法自疆運動, a movement of Strenuous Efforts through Reforming the Law), the Western Affairs Movement(洋務運動) in China, Meiji Restoration(明治維新) in Japan, or Innovation Movements(開化運動) and the Patriotic Enlightenment Movement(愛國啓蒙運動) in Korea, the traditional meanings of Hakmun was degraded while it became a target of the criticism of the enlightenment movements. Accordingly, East Asians' perception of Hakmun rapidly began to change. Although there had been the Silhak(實學, practical science) movement in Korea, which tried to differentiate its conceptualization of Hakmun from that of Neo-Confucianism during the 18th and 19th century, the fundamental shift in meaning occurred with the influx of the modern Western culture. This change converted the ultimate objective of Hakmun as well as its methods and substances. The separation of humanics and natural sciences, rise in dignity of the technological sciences, and subdivision of learning into disciplines and their specialization were accelerated during the Korean enlightenment period. The inflow of the modern western science, humanized thought, and empiricism functioned as mediators in these phase and they caused an irreversible crack in the traditional academic thoughts. Confronting the western mode of knowledge, however, the East Asian intellectuals had to explain their new learning by using traditional terms and concepts; modification was unavoidable when they tried to explain the newly imported knowledge and concepts. This presentation focuses on the traditional concepts of 'gyeogchi'(格致, extending knowledge by investigating things) and 'gungni'(窮理, investigation of principles), pervasively used in philosophy, physics and many other fields of study. These concepts will mark the key point with which to trace changes of knowledge and to understand the way how the concept of Hakmun was converted into a modern one.

• Journal of the Korea Concrete Institute
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• v.15 no.5
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• pp.689-696
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• 2003

Recently, Appendix A of ACI 318∼02 Code introduced the Strut-and-Tie Model(STM) procedure in shear design of deep flexural members. The STM procedure is widely used in the design of concrete regions where the distribution of longitudinal strains is significantly nonlinear, such as deep beams, beams with large openings, corbels, and dapped-end beams. Experimental study included five high-strength reinforced concrete deep beams with different detailing schemes for the horizontal and vertical reinforcement. The specimens were designed as simply supported beams subjected to concentrated loads on the top face and supported on the bottom face. At failure, all specimen exhibited primary diagonal crack running from the support region to the point load. Specimens which had mechanical anchorages(terminators) gives better representation of the load-carrying mechanism than the specimen had standard 90-degree anchorage at failure in deep flexural members. Based on the test results, shear design procedures contained in the ACI 318-99 Code, Appendix A of the ACI 318-02 Code, CSA A23.3-94 Code and CIRIA Guide-2 were evaluated. The Shear design of ACI 318-99 Code, Appendix A of the ACI 318-02 Code and CIRIA Guide-2 shown to be conservative predictions from 10% to 36% in the shear strength of the single-span deep beam which was tested. ACI 318-99 Code was the lowest standard deviation.

• Korean Journal of Agricultural Science
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• v.31 no.1
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• pp.1-8
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• 2004

This study was carried out to identify the effects of seaweed extracts(GA14) on growth of two rice cultivars, Junambyo and Donganbyo. Seedling qualities of two cultivars were better in all items including heading dates at early stage treated at seedling plus 2-3 leaf stages than at single treatment of seedling. Ripening ratio of Junambyo in paddy field was increased 0.3% by seaweed extracts(GA14) treatment, but that of Donganbyo decreased 0.5%. 1,000 grain weight of Junambyo and Donanbyo by seaweed extracts(GA14) treatment was two to four grams higher and the yield of two cultivars was also higher by three to four percent. Appearance characters of two rice cultivars was high in head, while damaged, chalky and crack rate were low at seaweed extracts(GA14) treatment. Protein, moisture and amylose characteristics related to table quality of Junambyo were not different by seaweed extracts treatment, but table values was high in only treatment. Donganbyo was also similar to Junambyo, but table quality was slightly high at non-treatment.

• Journal of the Korean Wood Science and Technology
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• v.39 no.1
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• pp.53-59
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• 2011

A connection was made between a single stretcher and 2 headers with 2 threaded nails (Type-A), and another one between 2 stretchers and 2 headers with 4 threaded nails (Type-B) to use as specimens. Type-C was the stretchers that are connected with 2 threaded nails by half lap joint at end-distance 5D to reinforce Type-B, Type-C1 the stretchers that are connected by half lap joint at end-distance 10D, and Type-C2 with 3 threaded nails at end-distance 10D. Compressive shear strength of Type-C, the supplementation of Type-B, was decreased by 30%, compared with that of Type-B. Those of Type-B and Type-C1 that used longer end-distance than Type-C were about the same, and that of Type-C2 connected with 3 threaded nails was 1.28-times stronger than that of Type-C1. Connection of the retaining wall using existing square timber has a problem between long and short stretchers and 2 headers. So it was investigated in the experiment to replace it. Therefore, if Type-B is replaced with Type-C2 in constructing the retaining wall, the crack and the rupture of timber caused by threaded nail as well as construction period can be reduced, and also it can be expected to increase their own strength.

• Geomechanics and Engineering
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• v.16 no.3
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• pp.273-284
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• 2018

A detailed understanding of the mechanical behaviors for crushed coal rocks after grouting is a key for construction in the broken zones of mining engineering. In this research, experiments of grouting into the crushed coal rock using independently developed test equipment for solving the problem of sampling of crushed coal rocks have been carried out. The application of uniaxial compression was used to approximately simulate the ground stress in real engineering. In combination with the analysis of crack evolution and failure modes for the grouted specimens, the influences of different crushed degrees of coal rock (CDCR) and solidified grout strength (SGS) on the mechanical behavior of grouted specimens under uniaxial compression were investigated. The research demonstrated that first, the UCS of grouted specimens decreased with the decrease in the CDCR at constant SGS (except for the SGS of 12.3 MPa). However, the UCS of grouted specimens for constant CDCR increased when the SGS increased; optimum solidification strengths for grouts between 19.3 and 23.0 MPa were obtained. The elastic moduli of the grouted specimens with different CDCR generally increased with increasing SGS, and the peak axial strain showed a slightly nonlinear decrease with increasing SGS. The supporting effect of the skeleton structure produced by the solidified grouts was increasingly obvious with increasing CDCR and SGS. The possible evolution of internal cracks for the grouted specimens was classified into three stages: (1) cracks initiating along the interfaces between the coal blocks and solidified grouts; (2) cracks initiating and propagating in coal blocks; and (3) cracks continually propagating successively in the interfaces, the coal blocks, and the solidified grouts near the coal blocks. Finally, after the propagation and coalescence of internal cracks through the entire specimens, there were two main failure modes for the failed grouted specimens. These modes included the inclined shear failure occurring in the more crushed coal rock and the splitting failure occurring in the less crushed coal rock. Both modes were different from the single failure mode along the fissure for the fractured coal rock after grouting solidification. However, compared to the brittle failure of intact coal rock, grouting into the different crushed degree coal rocks resulted in ductile deformation after the peak strength for the grouted specimens was attained.