• Journal of the Korean GEO-environmental Society
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• v.24 no.4
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• pp.13-22
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• 2023

In this paper, through experimental research, the period when rock bolts exert support effects is presented as grout strength and through numerical analysis, the rock bolt pull-out behavior according to ground conditions and strength reduction factors is analyzed. As a result, it is determined that rock bolts exhibit their reinforcing effect at a grout strength of 5 MPa (cured for 18 hours). The influence of the boundary interface strength reduction factor was found to be significant for rock bolt displacement in weak ground conditions, for shear stress between grout and ground in highly elastic ground conditions, and for grout stress in all ground conditions. These findings are expected to contribute to the establishment of specific standards for rock bolt testing and numerical analysis, and to facilitate improved design and implementation of rock bolt reinforcement.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.65-74
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• 2003

This paper presents the results of a comparative study between FEM and LEM on slope stability analysis. For validation, factors of safety were compared between FEM and LEM. The results from the two methods were in good agreement. This suggests that the FEM with the shear strength reduction method can be effectively used on slope stability analyses. A series of analyses were then performed using the FEM for various constitutive laws, slope angles, flow rules, and the finite element discretizations. Among the findings, the finite element method in conjunction with the shear strength reduction method can provide reasonable results in terms of safety. Also revealed is that the results of FEM can be significantly affected by the way in which the type of constitutive law and flow nile we selected.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.233-243
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• 2009

The objective of this study was to investigate the effect of openings on the structural behavior of SC walls. The FEM program ABAQUS was used in this analytical study. The main parameters were the locations and sizes of the openings: a total of 20 locations and a total of four opening sizes were adopted. The analysis results were compared with the results of the currently applied evaluation methods. The strength reduction factor method may be used to safely design SC walls with openings. The strength reduction factor of the effective strut method is more similar to that of the analysis results.

• Structural Engineering and Mechanics
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• v.12 no.3
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• pp.249-266
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• 2001

Current seismic design provisions allow structures to deform into inelastic range during design level earthquakes since the chance to meet such event is quite rare. For this purpose, design base shear is defined in current seismic design provisions as the value of elastic seismic shear force divided by strength reduction factor, R (${\geq}1$). Strength reduction factor generally consists of four different factors, which can account for ductility capacity, overstrength, damping, and redundancy inherent in structures respectively. In this study, R factor is assumed to account for only the ductility rather than overstrength, damping, and redundancy. The R factor considering ductility is called "ductility factor" ($R_{\mu}$). This study proposes ductility factor with correction factor, C, which can account for dynamic P-${\Delta}$ effect. Correction factor, C is established as the functional form since it requires computational efforts and time for calculating this factor. From the statistical study using the results of nonlinear dynamic analysis for 40 earthquake ground motions (EQGM) it is shown that the dependence of C factor on structural period is weak, whereas C factor is strongly dependant on the change of ductility ratio and stability coefficient. To propose the functional form of C factor statistical study is carried out using 79,920 nonlinear dynamic analysis results for different combination of parameters and 40 EQGM.

• Proceedings of KOSOMES biannual meeting
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• 2018.06a
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• pp.193-193
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• 2018

현재 우리나라는 레저선박 및 중소형 선박, 연안소형어선에 대부분 사용되는 재질은 강도가 높고 내양품성이 우수한 FRP를 사용하고 있다. 하지만 FRP선박의 폐선 시 환경문제와 자원재활용, 선체중량에 연비 및 대기오염등에 의해 소형선박 중심으로 알루미늄선 전환이 이루어지고 있다. 본 연구에서는 알루미늄 선체가 적용된 멀티하우스보트에 알루미늄선 구조기준에 따른 슬래밍하중을 적용하여 구조 강도평가를 실시하였으며, 그 결과를 통해 각 부재별 민감도 평가를 수행하여 알루미늄 구조강도기준을 만족함과 동시에 중량 저감을 하여 실제 선박설계에 적용시키고자 한다.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.176-183
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• 2008

This paper highlights the importance of carrying out global slope stability analysis as part of design calculations for geosynethetic walls in tiered configuration. Four design case histories were selected to examine the appropriateness of their design by performing additional slope stability analyses using the shear strength reduction method with in the frame work of finite element analysis. The results indicated that all of the walls examined, which were designed to meet the current design guide lines, did not satisfy the global slope stability requirement, and that longer reinforcements are required in the upper tiers to achieve the minimum factor of safety. Practical implications of the findings are discussed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.191-194
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• 2009

Very big springback in advanced high strength steel(AHSS) sheets invokes undesired shape defects, which can be eliminated by the tool surface correction method or the forming process control method. Since the springback reduction by controlling the forming process is limited, in this study, the die correction method which finds die correction from the relationship between die design variable and springback is introduced to achieve springback reduction and is applied to the automotive side rail to reduce the springback of 75.8% within the assembly limit of 1 mm.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.201-206
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• 2001

This paper presents truss model that can be used to determine the deformation as well as strength of RC members. This model is constituted to address plastic hinge rotation at tile deformation concentrated regions under severe lateral load. The behavior of each element of truss model is evaluated on the basis of stress field analysis. The deformation is obtained by combining element deformations with joint rotation. Initial strength is calculated at the first failure of any element, and strength deterioration after failure depends on the strength reduction of this element. The proposed model will provide useful tools in seismic design of ductility-required members.

• Smart Structures and Systems
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• v.2 no.4
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• pp.339-355
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• 2006

A procedure to retrofit existing essential facilities subjected to seismic excitation is proposed. The main features of this procedure are to reduce maximum acceleration and associated forces in buildings subjected to seismic excitation by reducing their strength (weakening). The weakening retrofit, which is an opposite strategy to strengthening, is particularly suitable for buildings having overstressed components and foundation supports or having weak brittle components. However, by weakening the structure large deformations are expected. Supplementaldamping devices however can control the deformations within desirable limits. The structure retrofitted with this strategy will have, therefore, a reduction in the acceleration response and a reduction in the deformations, depending on the amount of additional damping introduced in the structure. An illustration of the above strategy is presented here through an evaluation of the inelastic response of the structure through a nonlinear dynamic analysis. The results are compared with different retrofit techniques. A parametric analysis has also been carried out to evaluate the effectiveness of the retrofitting method using different combination of the performance thresholds in accelerations and displacements through fragility analysis.

• Journal of Korean Society of Steel Construction
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• v.27 no.3
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• pp.281-288
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• 2015

Seismic members like damper do not have any treatment of preventing story stiffness reduction after elastic yielding of stories causing story collapse. This paper suggests a method able to prevent story stiffness reduction using high-strength steel. This paper suggests these also : (1) High-strength steel stud column reinforcing story stiffness reduction until story drift 0.02rad can be designed in small area without adjusting layout. (2) Suggested seismic member installing at lowest level shows effects to preventing deformation concentration under huge seismic waves.