• Journal of the Society of Disaster Information
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• v.18 no.2
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• pp.314-323
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• 2022

Purpose: To study the effect of the amended Occupational Safety and Health Act on the expansion of the employer's responsibility and obligations and the evaluation of the employer on the improvement of the safety management system. Method: An academic discussion was conducted by comparing the contents of previous studies with the analysis results. A questionnaire was prepared using the measurement tools collected from previous studies, and statistical multiple regression analysis was performed with the collected data. Result: Research hypothesis It was found that the expansion of responsibility and obligations of the business owner and the reinforcement of the employer's evaluation of the ordering party had a positive (+) effect on the improvement of the safety management system. Conclusion: The expansion of the responsibility and obligations of the employer and the strengthening of the evaluation of the owner of the orderer are having a positive effect on the improvement of the construction safety management system for the prevention of construction accidents.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.363-366
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• 2005

When widening or repairing concrete deck slab, there is a joint inevitably. However, joining-construction method have following problem, that is the additional stress in existing part of bridge resulting from the specific process of joining-construction and the difference of amount of shrinkage between new and existing bridge. On this study, compared shrinkage stress of the direct joining construction method with the indirect joining construction method, and concluded the proper substitution rate of expansion cement. The rate of replacement was proper at $10\%$. but more than $15\%$, concrete had excessive expansion and weeker compressive strength. The time of placing closure concrete, considering the shinkage stresses and creep, was suitable in $45\~60$ days after placing the new concrete deck slab.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.11-12
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• 2013

It is required to response to the demand for new space due to high density of population and buildings in urban area. In particular, in case of big cities such as Seoul where the lack of new construction site due to the depletion of available space, existing buildings must be demolished for new construction. Utilization of urban underground space can be an alternative to solve for urban space problems. There are applications of underpinning methods using micropiles for existing buildings. Sometimes, the difficulties come from the compact space available for new foundation underneath the existing ones. In this paper, a novel underpinning method is introduced which can solve the space restriction problems underneath existing columns.

• Journal of architectural history
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• v.28 no.2
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• pp.31-40
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• 2019

Considering the situation in the early 20th century when the existing urban system centered on urban areas began to change, the biggest factors causing urban structural changes in urban areas are construction of railroad and urban dismantling. The change process of Eupseong, in the microscopic viewpoint, can be understood as a process of change in the course of dismantlement of town's demarcation, improvement of accessibility and urban expansion due to the construction of railroads, process of urban expansion following the crumbling boundaries and structural changes. This study aimed to look at the transformation process of the Eupseong in the early 20th century, focusing on the demolition of the castle and the railway construction from a microscopic point of view of city.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.3
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• pp.194-199
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• 2010

Based on the idea of eigen-mode expansion, a method to analyze the reflection of Lamb wave from a finite vertical discontinuity of plate is theoretically derived and verified by experiment. The theoretical prediction is in good agreement with the experimental result, and this strongly suggests that eigen-mode expansion method could be used for solution of inverse scattering problem for ultrasonic testing using Lamb wave.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.121-128
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• 1996

In this study design and construction technique for joint-less integral abutment for short to mid span bridges was developed. Expansion of superstructure due to thermal effect was absorbed in the flexible pile-type abutment in stead of expansion joint in the conventional bridges. Design method for pile subject to vertical and horizontal force was proposed. Backfill, approach slab and details of its connection joint with pavement was also proposed.

• Water Engineering Research
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• v.1 no.1
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• pp.63-74
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• 2000

This paper presents a two- phase search scheme for optimal pipe expansion of expansion of existing water distribution systems. In pipe network problems, link flows affect the total cost of the system because the link flows are not uniquely determined for various pipe diameters. The two-phase search scheme based on stochastic optimization scheme is suggested to determine the optimal link flows which make the optimal design of existing pipe network. A sample pipe network is employed to test the proposed method. Once the best tree network is obtained, the link flows are perturbed to find a near global optimum over the whole feasible region. It should be noted that in the perturbation stage the loop flows obtained form the sample existing network are employed as the initial loop flows of the proposed method. It has been also found that the relationship of cost-hydraulic gradient for pipe expansion of existing network affects the total cost of the sample network. The results show that the proposed method can yield a lower cost design than the conventional design method and that the proposed method can be efficiently used to design the pipe expansion of existing water distribution systems.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2405-2408
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• 2011

In recent time, the cause analysis and the reduction of the track irregularity have become the most important issue in the ballasted track on the high-speed railway bridge. This is because that the frequency of the maintenance work at the bridge expansion joint zone is on the rise. The track irregularity on the railway bridge starts at the end of the bridge-deck and spreads along the bridge. Due to the dynamic vibration and the thermal expansion of the bridge, the compaction of the ballast gravel on the bridge expansion joint zone become loose and then the progress of the track irregularity result from the train-induced dynamic impact is accelerating further. Among the several options for reducing the track irregularity on the bridge expansion joint zone, the application and efficiency of the zero longitudinal restraint(ZLR) and tied sleeper are investigated in this paper. Field test construction has been conducted, then the progress of the track irregularity and the frequency of the maintenance work are analyzed before and after the filed test construction. Of the two methods, it is shown that the installation of the ZLR seems to be better than the tied sleeper.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.73-76
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• 2009

Autogenous shrinkage of high-strength mass concrete is affected high temperature history. So to evaluate autogenous shrinkage of high-strength mass concrete accurately, thermal expansion in it should be removed. In this study, compensated autogenous shrinkage was calculated after gathering thermal expansion coefficient at early age experimentally. As a result of the study. Autogenous shrinkage of mass specimen (300 ${\times}$ 300 ${\times}$ 300mm) was remarkably higher than it of standard specimen (100 ${\times}$ 100 ${\times}$ 400mm). So it was found that compensation on thermal expansion should in evaluating autogenous shrinkage of high-strength mass concrete. And this study shows results on opc and similar own contraction, if used retarder.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.37-49
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• 2021

Micropiles are widely used in construction field to enhance bearing capacity and reduce settlement of existing foundation. It has various benefits such as low construction expense, simple installation process, and small construction equipment. Recently, new microple equipped with the base expansion structure at the end has been developed to improve the foundation bearing capacity. The improvement of load capacity can be conceptually achieved by expanding the base expansion structure when a load is applied to the micropile. However, the expansion mechanism of the base expansion structure and the improvement of load capacity of the micropile were not yet experimentally validated. Therefore, in this study, a series of centrifuge model tests was performed to evaluate the effect of the base expansion structure on the improvement of load capacity. Two types of soil, sand and weathered rock, were prepared and the loading tests were performed using the real micropile with the base expansion structure. During the tests, the earth pressures surrounding the base expansion structure were monitored. As a result, when a load of 30 kN was applied to the micropile, the increase in the ratio of the horizontal to vertical pressure increment (∆σ_h/∆σ_𝜈) ranged from 0.4 to 0.58 in sand and ∆σ_h/∆σ_𝜈 = 0.19 in weathered rock, respectively. Therefore, it can be concluded that the increase in the horizontal earth pressure adjacent to the base expansion structure will improve the bearing capacity of the micropile.