• Tunnel and Underground Space
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• v.29 no.3
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• pp.172-183
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• 2019

The generalized Hoek-Brown (GHB) failure criterion developed by Hoek et al. (2002) is a nonlinear function which defines a stress condition at failure of rock mass. The relevant strength parameter values are systematically determined using the GSI value. Since GSI index is a value quantifying the condition of in-situ rock mass, the GHB criterion is a practical failure condition which can take into the consideration of in-situ rock mass quality. Considering that most rock mechanics engineers are familiar with the linear Mohr-Coulomb criterion and that many rock engineering softwares incorporate Mohr-Coulomb criterion, the equations for the equivalent friction angle and cohesion were also proposed along with the release of the GHB criterion. The proposed equations, however, fix the lower limit of the minor principal stress range, where the linear best-fitting is performed, with the tensile strength of the rock mass. Therefore, if the tensile stress is not expected in the domain of analysis, the calculated equivalent friction angle and cohesion based on the equations in Hoek et al. (2002) could be less accurate. In order to overcome this disadvantage of the existing equations for equivalent friction angle and cohesion, this study proposes the analytical formula which can calculate optimal equivalent friction angle and cohesion in any minor principal stress interval, and verified the accuracy of the derived formula.

• Journal of the Korea Convergence Society
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• v.10 no.6
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• pp.49-58
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• 2019

This study aims to analyze the relevance between oral health practices and oral discomforts of the elderly in an urban-rural area by surveying the elderly in welfare centers for the Elderly-continued oral health care program. The result shows that the elderly brush their teeth under regular oral care, and practice oral health life by scaling for the prevention of periodontal disease. Most of the elderly who drink alcohol have experienced implant care and tend to quit drinking after the treatment, and seemed to get their oral discomfort relieved. However, no relevance is found between implant experiences and social discomfort. Furthermore, the elderly who had bad breath expressed pronunciation, taste, pain and chewing discomfort, and social discomfort (P>.05). The educational level of the elderly did not have an impact on oral discomfort, but smoking, chewing and bad breath discomfort seemed to be related to social discomfort(P>.05). Therefore, since oral discomfort of the elderly causes social discomfort which decreases their quality of living, we recommend oral health departments of local governments to help the elderly maintain happy lives by continuing to study the practical use of reducing oral discomfort.

• Journal of the Korean Institute of Gas
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• v.23 no.4
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• pp.10-18
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• 2019

The Interior finishing materials tried to evaluate the combustion characteristics and the dangerous characteristic of Floor finish and Wall finish. We often use, conducting the experiment ISO 5660-1, Cone Calorimeter method, and ISO-TR-9122 FT-IR. According to the result of Cone calorimeter experiment, the tile carpet FF3 of Floor material had the highest THR $74.6mj/m^2$ because of the highest risk, and the PHRR of FF1 was $726kW/m^2$, which was easy to bum. As a result FT-IR test, The CO, $CO_2$ ratio was 8,146 PPM for roll carpet FF1 than tile carpet FF2, FF3 5,996, 5,171 PPM, which was a carpet with a high toxicity risk. In the case of wall finishes, The MDF plate(WF3) was THR $86.7mj/m^2$ with a high risk, PHRR $384kW/m^2$ was easy to ignite and toxicity index was 5.5. The CO, $CO_2$ ratio was 1,340~8,596 PPM, But the WF4 was the most toxic with 8,596 PPM.

• Korean Journal of Construction Engineering and Management
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• v.20 no.2
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• pp.105-112
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• 2019

As the Construction Technology Promotion Act was revised in 2015, the term of Supervision was removed and Construction Management was included instead. The consideration of Construction Management shall be based on the cost plus fee method specified in the Criteria for the Cost of Construction Technology Services of the Ministry of Land, Infrastructure and Transport. Nevertheless, it is based on the construction cost ratio in accordance with the Economy and Finance Ministry's Detailed Guidelines for Preparing the 2018 Budget Plan and Fund Management Plan (Manual for Business Type and Item). As a result, it has been expected that Construction Management consideration will be calculated according to a single government standard and that the Criteria will be applied reasonably. In addition, although the change in the Labor Standard Act has a significant effect on the working environment of the construction site, the nature of the construction site is not considered in this Act. Based on these problems, the study suggested that the government should apply a single standard after consultation with the relevant agencies when calculating the consideration for Construction management, that the scope of the Criteria for the Cost of Construction Technology Services should be clear, that the amount of input by the Construction Manager should be considered for the capability of engineers and the number of working days, and that construction characteristics should be considered when determining the number of working days and hours.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.339-346
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• 2018

An Industry Foundation Classes(IFC), which is a data schema developed focusing on architecture, is being expanded to civil engineering structures. However, it is difficult to create an information model based on extended IFC since the BIM software cannot provide support functions. To manage a railway track based on the extended IFC, this paper proposed a method to create an alignment-centered separated railway track model and convert it to an extended IFC-based information model. First, railway track elements have been classified into continuous and discontinuous structures. The continuous structures were created by an alignment-based software, and discontinuous structures were created as independent objects through linkage of the discretized alignment. Second, a classification system and extended IFC schema for railway track have been proposed. Finally, the semantic information was identified by using the property of classification code and user interface. The availability of the methods was verified by developing an extended IFC-based information model of the Osong railway site.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.205-212
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• 2018

In order to overcome shortcomings of commercial analysis program for solving certain geotechnical problems, finite element method adopting isoparametric quadrilateral element was selected as a tool for analyzing soil behavior and calculating process was programmed. Two examples were considered in order to verify reliability of the developed program. One of the two examples is the case of acting isotropic confining pressure on finite element and the other is the case of acting shear stress on the sides of the finite element. Isoparametric quadrilateral element was considered as the finite element and displacements in the element can be expressed by node displacements and shape functions in the considered element. Calculating process for determining strain which is defined by derivatives using global coordinates was coded using the Jacobian and the natural coordinates. Four point Gauss rule was adopted to convert double integral which defines stiffness of the element into numerical integration. As a result of executing analysis of the finite element under isotropic confining pressure, calculated stress corresponding to four Gauss points and center of the element were equal to the confining pressure. In addition, according to the analyzed results for the element under shear stress, horizontal stresses and vertical stresses were varied with positions in the element and the magnitudes and distribution pattern of the stresses were thought to be rational.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.7-17
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• 2018

Test bed additional wall combined with PHC-W pile retaining wall has been constructed. To determine the dimensions of test bed additional wall, bending and shear tests of full scale core members of additional wall were tested. Basement additional walls utilizing PHC-W pile retaining wall, which were developed by modifying the cross-section of PHC piles, were classified into the composite additional wall and the non-composite additional wall. Their tests were conducted to obtain bending strength and shear strength of basement additional walls ultilizing PHC-W pile retaining wall. Since bending strengths and shear strengths of the composite additional wall and the non-composite additional wall were similar, it could be confirmed that the non-composite additional wall could be applied instead of the composite additional wall. Full-scale model additional wall was 200 mm thick, thus the thickness of additional wall combined with PHC-W pile retaining wall could be reduced by 100~200 mm.

• Korean Journal of Construction Engineering and Management
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• v.20 no.1
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• pp.141-150
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• 2019

In the overseas plant construction market, the domain construction firms' construction capability has been greatly improved, but the capability of project management is evaluated to be insufficient compared to the technical aspect. Project management capabilities from the initial planning stage of project execution are regarded as the core competence of advanced construction companies. Among them, it is urgent to improve the capacity of conceptual estimate for domestic companies. In this study, the researchers surveyed and analyzed the methodology of estimating project cost in the planning phase of the plant project and developed an estimation method by conducting a case study analysis. Based on the logic of the cost index and parametric estimation method among the existing estimation methodology, the estimation tool was developed by deriving the input and output variables tailored to the plant project. The validity of the proposed methodology was evaluated by comparing the accuracy between the project estimate amount of the case project and the actual project amount. In order to increase the utilization of the developed conceptual estimate methodology,for plant construction project, it is necessary to systematize the data of the historical project data. Increasing the accuracy of future project cost estimates is directly related to increasing project award and profitability of the domestic construction company.

• Fire Science and Engineering
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• v.32 no.6
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• pp.46-54
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• 2018

A total of 19 elevators for evacuation were installed in the Lotte World Tower and it is planned to operate the shuttle using the manual key from five refuge floors to the 1st floor in an emergency. In the event of a fire or other disaster, it is necessary to conduct intensive analysis to determine how much RSET reduction could be achieved using the evacuation elevator compared to the existing evacuation plans. When the optimal transportation sharing ratio by the evacuation elevators was 40% at the Lotte World Tower, the RSET of the evacuation scenario in parallel with the elevators in the entire building was calculated to be 1 hour and 2 minutes. The RSET of a conventional evacuation scenario (Walking along the stairs without using the elevators) was calculated to be 1 hour 29 minutes, therefore, the former evacuation scenario were found to have a shortening effect of approximately 27 minutes compared to the latter. On the other hand, to maintain this effect, each part of the evacuation route using the elevator must have the capability to protect the evacuee from any hazards caused by fires, such as smoke, flame, and radiant heat during the evacuation. Moreover, the evacuation route should be continuous from the residence position of the elevator user to the final evacuation site, and be recognized easily.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.123-128
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• 2018

MDF was treated on the surface of MDF with fire retardant lacquer, water-soluble flame retardant coat and water-soluble wood cover on the MDF wood, and the pyrolysis characteristics and the atmospheric noxious gas generation characteristics were investigated by using the large capacity thermal analyzer. As a result of investigating pyrolysis and combustion gas generation characteristics after treatment of 0.11 / 11.55 g in terms of mass ratio, it was found that combustion starting time was slightly longer than that of pure MDF in the case of treatment with fire retardant lacquer. The combustion temperature was increased from $340^{\circ}C$ to $450^{\circ}C$. The pyrolysis and combustion gas generation characteristics of the MDF wood treated with the aqueous flame retardant coat showed the changes in combustion starting time and temperature from $260^{\circ}C$ to $542^{\circ}C$ for about 26 minutes at the mass ratio of 0.13 / 11g. Also, when the commercially available waterproof wood cover was treated with 0.13 / 11.55 g of MDF, the sudden weight change tended to increase from $300^{\circ}C$ to $370^{\circ}C$ and showed a second change at approximately $500^{\circ}C$.