• Journal of the Korean Geotechnical Society
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• v.30 no.3
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• pp.73-85
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• 2014

The strength parameters used in rock mass design are mainly estimated by equations using Hoek-Brown failure criterion because the tests to obtain the values are limited and expensive. To estimate the strength parameters, the Hoek-Brown failure criterion should be transformed to the Mohr-Coulomb failure criterion. But the processes are more or less cumbersome due to the several stages including the computation and the analyzing steps. In this study, several rock states of various conditions were modeled and then the strength parameters were estimated using the Hoek-Brown failure criterion. Thereafter by analyzing the results, some charts and equations estimating the strength parameters through only one step or easily in the field using the values of RMC, the uniaxial compressive strength and the rock constant ($m_i$), were suggested. And then the suggested method was compared and discussed with the existing method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.98-104
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• 2018

Nondestructive strength Equations are commonly used to determine the strength of concrete. However, the application of the existing equations may include many errors because this method is proposed on the basis of limited experimental parameters while actual bridges have various parameters such as conditions of concrete mixtures, properties of concrete strength, etc. Also, the error among the existing equations causes the confusion when engineers select the proper estimation equation for the concerned bridge. In this study, a series of the field inspection and the test have been performed on 297 existing bridges, in order to evaluate the bridges, based on the test results of the in-depth inspection, and the estimated strengths by means of the nondestructive strength equations are analyzed and compared with results of the core specimen strengths. According to results of analyses, the nondestructive strength equation proposed by CNDT Committee of Architectural Institute of Japan had high relationship with core strength. However, the strengths predicted by this equation, are underestimated when concrete's strengths are over 30 MPa, otherwise, they are overestimated. Also in this paper, based on the relationship between the estimated nondestructive concrete strengths and the core specimen strengths the modified strength equation through simple correlation analysis is proposed.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.2
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• pp.117-117
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• 1995

본 논문에서는 콤팩트 형광램프용 Dimming형 전자식 안정기의 설계에 있어서, 인버터 공진탱크의 커패시턴스값을 변화시킬 때 전압이득곡선을 분석하여 최적의 회로정수를 결정하는 방법을 제안하였다. 또한 하프브리지 인버터회로의 회로정수에 대한 PSpice 시뮬레이션을 행하여 램프전압과 전류값을 구하였고, 실제 전자식 안정기를 제가하고 시동특성과 조광특성을 비교분석하였다. 시동특성은 일반 전자식 안정기와 거의 동일하였으며, 조광특성은 전체 광출력의 5%까지 안정동작되어, 제안된 방법이 뛰어남을 확인하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.337-337
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• 2021

본 연구에서는 낙동강수계 도시의 주요 용수공급원인 댐유역의 연강수량과 연유입량자료를 수집 후 "NDIC-FAT" 가뭄빈도해석 프로그램(한국수자원공사 국가가뭄정보분석센터(NDIC), 2020)을 활용한 가뭄빈도분석을 시행하여 과거 동일기간과 비교하여 현재의 강수량 또는 유입량의 재현기간 및 크기를 산정하고, 수집된 연구대상 유역의 연강수량과 연유입량자료에 대한 상관식을 개발하여 가뭄빈도에 따른 연유입량 값을 가뭄빈도해석프로그램의 분석결과와 비교하여 본 연구에서 제안된 상관식의 활용성을 검토하였다. 가뭄빈도분석 결과 강수량에 따른 확률분포형은 6개의 유역중 2개소(남강댐, 합천댐)에서 AIC값에서 Normal 분포형이 가장 낮았고 나머지 4개소(안동댐, 영천댐, 운문댐, 임하댐) 유역은 AIC값에서 Gumbel 분포형이 가장 낮게 나타나 본 연구에 적용하였다. 연유입량에 따른 확률분포형 검정은 남강댐, 안동댐, 영천댐, 운문댐, 임하댐, 합천댐 유역 6개소 모두 AIC값에서 2변수 Log-Normal 분포형이 가장 적합한 것으로 평가되었다. 연구대상 유역의 연강수량과 연유입량자료를 이용하여 연유입량에 대한 상관식을 개발하여 비교한 결과 영천댐유역을 제외한 5개 유역의 일치율이 높게 나타났다.

• Journal of the Korean GEO-environmental Society
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• v.12 no.10
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• pp.13-22
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• 2011

In this study, features of correlation between S-velocity and N value are derived from 9 suspension PS layers in Chungcheong Buk-do. S-velocity to be measured on Chungcheong Buk-do is classified into 5 as conditions of stratum that are ; cohesive soil layer, sandy soil layer, gravel layer, weathering soil layer, weathered rock layer. Each correlation formulas between N value by SPT and S-velocity is proposed from these classifications. And correlation formula for whole soil body except weathered rock layer also is proposed for reference. Corelation formulas developed this study formed square expression considering existing formulas produced internationally. Strength parameter converted to linear if N value is more than 50. Features of proposed formula which came up with comparative analysis of international result of cohesive soil layer and sandy soil layer and gravel layer show similar to existing ones. But there is deference that result of correlation formula for weathered rock layer is a little smaller than domestic formula's one. Because correlations of weathered rock layer above the N value of 50 is converted into a linear formation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1A
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• pp.55-64
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• 2012

Experimental investigation on the structural behavior of steel fiber-reinforced ultra high performance concrete (UHPC) beams subjected to shear are presented. Six tests carried out on simply supported I-beams under concentrated loads are presented. The parameters varied were the volume fraction of the fibers (1.0, 1.5 and 2.0%) and shear span-effective depth ratio (2.5, 3.4). The test results indicated that ultimate shear strength increased with increasing fiber volume, and that ultimate shear strength decreased with increasing shear span-effective depth ratio. In addition, applicability of predictive equations for evaluating the ultimate shear strength of steel fiber-reinforced UHPC beams are estimated based on the test results. The comparison between computed values and the experimentally observed values are shown to validate the proposed theoretical equations. It is found that predictions by using AFGC and JSCE recommendations provide the most accurate estimates of shear strength of steel fiber-reinforced UHPC beams.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.4
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• pp.665-670
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• 2006

In this paper, the results of empirical methods and the numerical analysis were compared and investigated on the lateral displacement due to embankment in soft soil. The empirical methods gave different results so the possibility of lateral displacement could not be determined only by the empirical methods. The numerical analysis could be used so effectively that its result showed useful lateral and vertical displacements with depth and distance.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.1-2
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• 2009

Abutment Integral Approach Slabs are proposed to improve road traveling performance of bridge approaches and evaluated analysis application possibility of approach slabs in abutment integral approach slabs as comparing between Abutment Integral Approach Slabs and approach slabs in general bridges.

• Journal of the Korean GEO-environmental Society
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• v.4 no.2
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• pp.65-76
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• 2003

Stone column is a soil improvement method and can be applicable for loose sand or weak cohesive soil. Since the lack of sand, stone column seems one of the most adaptable approach for poor ground as a soil improvement technique. However, this method was not studied for practical application. In this paper, the bearing capacity of single stone column at the Gaduk, Ulsan and Gwangyang under the bulging and general shear failure mode were compared with those of the suggested formulas. Especially, a test result of single stone column at the Busan area by static load was compared with the bearing capacity of suggested formulas. The analysis results showed that there were not much bearing capacity differences among those suggested bearing capacity formulas. However, the bearing capacity by static load test was almost double of those with suggested formula. The result also showed that the undrained shear strength was the most important parameter for the bearing capacity estimation of stone column.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.171-179
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• 2002

This paper is a part of research series for the verification of the proposed Moon/Lim design equation. An analytical study was performed to examine the relation between the flexural behavior and the unbonded tendon stress of PSC members. The strain compatibility assumption was used in this study since previous studies showed that the stress variations of tendon had a close relation with the member displacements. The proposed equation has been developed with the same assumption of strain compatibility. Therefore the analytical procedure with the strain compatibility assumption was developed to compute the member displacements of previous tests. Then the analytical results were compared with tests results. The comparison showed that the strain compatibility assumption can be properly applicable to the design equation. Based on the analytical results, the relation between the tendon stress and the member flexural behavior at ultimate was examined. A parametric study also carried out with regard to the member displacements. As results, the parameters used for the proposed equation were proven to be proper for the computation of tendon stress.