• Journal of the Korean GEO-environmental Society
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• v.8 no.5
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• pp.57-65
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• 2007

Slope collapse occurs mostly at the rainy season or thawing season in Korea. From a engineer point of view, the design criterion in recent of soil slopes during the rainfall have a conservative tendency because a slope stability is evaluated in the condition that ground water level is located in the surface. However, for the rational design of soil slopes during rainfall, the raining conditions and the unsaturated soil characteristics of soil slopes have to be considered. For the unsaturated soil characteristics of soil slopes, the laboratory tests for unsaturated soils and the seepage analyses for the raining conditions have to be performed. Due to these difficulties, a conservative design of soil slopes in the current design criterion has been carried out. In this paper, therefore, a simple design method is proposed. The method is considered to the unsaturated soil characteristics and the results of seepage analysis without numerical analysis. To verify the suggested design method, it is compared with both analysis results by current design criterion and analysis results based on the seepage analysis. Through the comparative study, it was found that the current design criterion has been excessively conservative. Hence, simple design method in this study was evaluated as the rational design for the soil slopes during rainfall.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.3
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• pp.87-99
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• 1982

This study proposes a reliability based design criteria for the R.C. superstructures of highway bridges. Uncertainties associated with the resistance of T or rectangular sections are investigated, and a set of appropriate uncertainties associated with the bridge dead and traffic live loads are proposed by reflecting our level of practice. Major 2nd moment reliability analysis and design theories including both Cornell's MFOSM(Mean First Order 2nd Moment) Methods and Lind-Hasofer's AFOSM(Advanced First Order 2nd Moment) Methods are summarized and compared, and it has been found that Ellingwood's algorithm and an approximate log-normal type reliability formula are well suited for the proposed reliability study. A target reliability index (${\beta}_0=3.5$) is selected as an optimal value considering our practice based on the calibration with the current R.C. bridge design safety provisions. A set of load and resistance factors is derived by the proposed uncertainties and the methods corresponding to the target reliability. Furthermore, a set of nominal safety factors and allowable stresses are proposed for the current W.S.D. design provisions. It may be asserted that the proposed L.R.F.D. reliability based design criteria for the R.C. highway bridges may have to be incorporated into the current R.C. bridge design codes as a design provision corresponding to the U.S.D. provisions of the current R.C. design code.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.175-185
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• 2013

Currently in precast concrete construction, precast concrete and cast-in-place concrete with different concrete strengths are used. However, current design codes do not provide shear design methods for PC-CIP hybrid members using dual concrete strengths. In the present study, the shear strengths of beams using dual concrete compressive strengths (24 MPa, 60 MPa) were tested. The test variables were the area ratio of the two concretes, longitudinal bar ratio, and shear span-to-depth ratio. The shear strengths of test specimens were evaluated by current design methods, using an effective concrete strength (considering the area ratio of the two concrete strengths). The test result showed that when 60 MPa concrete was used in the compressive zone and the longitudinal bar ratio was low, the shear strengths of the test specimens were less than the predictions. On the basis of the results, design recommendations were provided for the shear design of the PC-CIP hybrid beams.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.454-457
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• 2011

본 논문에서는 국내에서 아직 기준이 마련되지 않은 제진설계에 대한 접근을 소개하였다. ASCE 7-05 기준에 근거하여 국내 5층 규모의 철근콘크리트 신축 건물에 제진 설계를 수행하였다. 우리나라의 현행 기준을 만족하면서 효과적인 제진 시스템 설계를 위한 방법을 소개한다. ASCE 7-05 기준에서는 제진 구조물 해석 시 부재력이 공칭강도의 1.5배를 초과하지 않은 경우 경계비선형 해석을 허용하고 있다. 이 때의 제진 설계 프로세스는 기존의 중력하중 및 등가정적하중의 75%에 의한 단면을 가정하여 부재설계를 실시하고, 선형 시간이력 해석을 통해 제진장치 및 가새를 설계한다. 이후 우리나라 실정에 맞도록 보정된 인공 지진파를 입력하여 경계비선형 해석을 실시하고, 밑면 전단력 및 층간변위 등의 만족여부를 검토한다. 이 때 목표성능을 완전탄성설계 또는 유사탄성설계로 정하여 목표성능을 만족하는지도 검토하여야 한다. 본 논문에 적용한 신축 건물은 유사탄성 설계를 위해 경계비선형 해석을 실시하였고, 가장 효과적인 제진 설계를 위해 댐퍼의 종류, 설치방법, 개수, 변위 증폭비 등을 변수로 한 case study를 진행하였다. 해석 결과 목표성능을 만족하는 범위 내에서 가장 효과적인 제진 설계는 점성댐퍼, 이층 토글형태, 증폭비 2.0, 총 8개의 댐퍼를 설치하는 것으로 나타났다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.145-150
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• 2019

This paper proposes a model for the calculation of the ultimate torsional strength in normal-strength and high-strength concrete beams which include the concrete contribution strength and use a reasonable thickness of shear flow. The adequacy of the proposed model is evaluated by comparing the calculated torsional strength with the experimentally observed results from 104 test specimens reported in the literature. The results are also compared with the calculations of the KCI and the ACI building code equations, and those of other model which include the concrete contribution strength. The comparisons show that the ultimate torsional strengths calculated by the proposed equation and Rahal's equation are closer to the experimentally observed results than those calculated by the code equations.

• Journal of Korean Society of Transportation
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• v.22 no.2 s.73
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• pp.55-63
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• 2004

기존의 설계시간순위 결정은 "순위곡선의 기울기가 완만해지는 지점"이라는 정성적인 기준을 사용하였다. 따라서, 분석자마다 서로 다른 결과를 도출하고 도로 설계시 고려해야하는 두요소(교통혼잡, 경제성)를 전혀 고려하지 못하는 문제점이 있다. 또한 현재의 도로 설계시 대상으로 삼는 시간교통량은 국내 도로의 교통특성이 설, 추석 등의 연휴에 집중적으로 몰리는 등 외국과 그 특성이 상이함에도 불구하고 미국과 동일한 상위 30순위 교통량을 사용한다. 상위 30순위 교통량을 설계시간순위로 하는 경우, 상위 30순위교통량 중 휴일교통량의 비율이 74.1%(설, 추석 연휴 39.7%)로 휴일 집중 교통량의 영향을 크게 받으며, 연중 최대교통량이 용량의 85.2% 에 불과해 도로가 과다 설계된다. 본 연구에서는 목표년도의 연중 최대시간교통량이 용량에 도달하는 순위를 설계시간순위로 하였으며, 분석결과 상위 150순위가 교통혼잡과 도로의 경제성을 모두 고려할 수 있는 설계시간순위로 산정되었다. 설계시간순위를 150순위로 할 경우 현행 설계순위인 30순위에 비해 휴일비율 13.8% 감소, 최대시간교통량의 용량비율($V_1/C_a$) 16.0% 증가의 효과가 있을 것으로 분석되었다. - 현행 설계시간순위(30순위) : 휴일비율 74.1%(설, 추석 비율 39.7%), $V_1/C_a$ 85.2% - 제안 설계시간순위(150순위) : 휴일비율 60.3%(설, 추석비율 23.0%), $V_1/C_a$ 101.2%

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.425-436
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• 2014

Although the strut-tie model approaches of current design codes are regarded as the valuable methods for designs of structural concretes with D-regions, the approaches have to be improved because of the uncertainties in terms of the concepts and provisions for designs of 3-dimensional structural concretes. To improve the uncertainties, a new strut-tie model approach is proposed in this study. In the proposed approach, the concepts of employing a 3-dimensional grid element allowing load transfers in all directions at a node to construct a strut-tie model, a numerical analysis approach to determine the effective strengths of concrete struts and nodal zones by reflecting the effects of reinforcing bars and 3-dimensional stress state, and maximum areas of struts and ties to examine their load carrying capacities are integrated into the strut-tie model approaches of current design codes.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.247-255
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• 2008

According to "A guide Book to Highway Design", most road elements are chosen based on a certain design speed in order to ensure obtaining safe and smooth traffic operating. However, road safety in practical way is corelative to not only all element of roads but also road shape, for example, between straight line and curves line and between curved lines. Also, it is relates to alignments such as horizontal alignment, vertical alignment, and cross section. That is, the practical road design should be examined in both sides of 3 dimension and consecutiveness as the practical road is a 3-dimensional successive object. The paper presents a concept for acceleration to evaluate consistency of road considering actual road shape on 3-dimension. Acceleration of vehicle is influential to road consistency based on running state of vehicle and state of drivers. Especially, the magnitude of acceleration is a quite influential element to drivers. Based on above, the acceleration on each point 3-D road can be calculated and then displacement can be done. Computation of acceleration means total calculation on each axis.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.57-65
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• 2011

Both shear and torsional moments apply shear stresses on cross-section of a member, which need to be considered in the design. But in the current Korean Building Code, the design equations for shear and torsional moments are expressed in terms of the sectional strength with different units, causing figures to be drawn separately in two axes. If the design equations are expressed in terms of stresses, then the stresses of shear and torsional moments can be added, allowing figures to be drawn in one axis for easy recognition of the design procedure and the final design results. Moreover, the current code's design equations for shear and torsional moments are considered separately with the intention of summing the area of stirrups with respect to unit length for shear moment ($A_{\upsilon}/s$) and torsional moment ($2A_t/s$). Since the size or type of vertical stirrups are predetermined in the design process, the design equations are expressed in terms of the spacing of stirrups rather than the $A_{\upsilon}/s$ and $2A_t/s$ terms, clarifying various design steps and a design process.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.301-304
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• 2010

이 논문에서는 콘크리트구조물의 성능설계를 위한 하중조합의 구성과 이의 신뢰도수준을 정하는 과정을 제시한다. 설계기준의 작성 및 적용에 관하여 논리적인 개념을 제시하고 있는 Eurocode 의 하중조합에 관한 기본 원칙을 살펴보고, 국내 및 미국의 콘크리트구조물의 설계에서 적용하고 있는 하중조합을 분석하여 본다. 구조물 설계에 관한 안전율의 결정에 있어서 널리 사용되고 있는 통계 및 신뢰도에 기반한 분석을 통하여, 현행 하중조합을 사용하고 재료별 저항계수를 적용하는 경우에 제공하게 되는 신뢰도 수준을 살펴본다. 철근콘크리트 보와 기둥의 예제를 이용하여 휨, 전단 및 축력에 관한 신뢰도 수준과 이에 영향을 미치는 설계변수들의 민감도분석을 수행한다.