• 콘크리트학회논문집
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• 제23권6호
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• pp.731-740
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• 2011

KCI 2007, ACI 318-08에 제시된 모멘트재분배 방법은 등분포 중력하중을 받는 연속 휨재에 대하여 검증된 방법이다. 횡하중에 의한 모멘트재분배 및 비탄성 거동은 중력하중과 전혀 다른 메커니즘을 발생된다. 이 연구에서는 기초역학에 근거하여 중력하중과 횡하중을 받는 철근콘크리트 모멘트골조의 보에 발생되는 모멘트재분배와 소성변형의 관계를 정량화하고, 이로부터 보의 소성변형능력에 근거한 모멘트재분배 설계법을 제안하였다. 제안된 모멘트재분배비는 KCI 2007, ACI 318-08 등 기존 설계기준과 마찬가지로 극한한계상태의 단면해석으로 결정되는 철근의 인장변형률로 정의된다. 또한 모멘트재분배비는 경간, 철근비, 단면강성, 변형경화 거동에 의하여 영향을 받는다. 제안된 방법을 사용하여 탄성해석으로 구한 설계모멘트를 재분배시키는 설계 가이드라인 및 예제를 제시하였다.

• 지질공학
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• 제30권4호
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• pp.635-648
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• 2020

본 연구는 회전관입말뚝의 이음부를 용접이나 볼트가 필요 없는 육각형 이음부로 개선하여 압축재하시험을 수행하였다. 또한 인발시험의 경우 기존 방법과 유사하게 볼트체결 방법으로 적용하여 인발시험을 수행하였다. 회전관입말뚝의 지지력을 평가하기 위해 현장시험 2지역을 선정하였다. 하중재하시험은 정재하시험과 인발시험을 수행하였으며 회전관입말뚝에 대한 지지력을 평가하였다. 현장시험결과, 정재하시험시 중력식 그라우트를 적용한 말뚝에서 AC 358 Code에 따른 지지력평가 결과 600 kN 이상으로 나타났으며, 그라우트가 없는 말뚝에서는 600 kN 이하의 지지력을 보여 중력 그라우팅이 필요함을 확인하였다. 또한 현장시험결과를 고려하여 지지력을 평가하였으며, 적은 표본에 의해서 도출된 결과로 추후 기초자료로 활용될 수 있을 것으로 판단된다.

• 한국전산구조공학회논문집
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• 제12권3호
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• pp.353-362
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• 1999

본 연구에서는 콘크리트 중력식 댐의 임계균열길이가 계산되었으며 또한 복합균열의 균열선단에서 유효응력 확대계수의 변화량이 조사되었다. 작용하중으로는 댐 상부면에 작용하는 정수압과 댐의 균열면에 작용하는 수압 및 자중으로 구성된 정하중, 그리고 댐 주위에서 발파작업이 수행되는 경우에 고려될 수 있는 발파진동 및 동수압으로 구성된 동하중이 사용되었다. 균열이 발생한 위치와 방향 및 발파진동의 크기에 따라 임계균열길이가 계산되었으며, 또한 복합균열의 형태 및 균열선단 간의 이격거리에 따른 유효응력확대계수의 변화량이 검토되었다.

• 한국지진공학회논문집
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• 제22권1호
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• pp.33-43
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• 2018

'Seismic Performance Evaluation Method for Existing Buildings (2013)' developed in accordance with the overseas guidelines ASCE 41 - 06 is the most widely used procedure among domestic seismic performance evaluation guidelines in Korea. However, unlike ASCE 41 - 06, it stipulates that the final performance should be derived as the gravity load distribution ratio of the lateral force resistance system in the guideline. Therefore, in the case of a dual steel structure system with slender braces, where the internal moment frame is mostly responsible for the gravity load, the evaluation of slender braces based on gravity load distribution ratio is difficult to be achieved. In this research, we propose an objective evaluation process for such system by evaluating seismic performance for large-scale factory facilities as an example.

• Earthquakes and Structures
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• 제16권2호
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• pp.235-251
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• 2019

Corrosion of reinforcement is the greatest threat to the safety of existing reinforced concrete (RC) structures. Most of the olden structures are gravity load designed (GLD) and are seismically deficient. In present study, investigations are carried out on corrosion damaged GLD beam-column sub-assemblages under reverse cyclic loading, in order to evaluate their seismic performance. Five GLD beam-column sub-assemblage specimens comprising of i) One uncorroded ii) Two corroded iii) One uncorroded strengthened with steel bracket and haunch iv) One corroded strengthened with steel bracket and haunch, are tested under reverse cyclic loading. The performances of these specimens are assessed in terms of hysteretic behaviour, energy dissipation and strength degradation. It is noted that the nature of corrosion i.e. uniform or pitting corrosion and its location have significant influence on the behaviour of corrosion damaged GLD beam-column sub-assemblages. The corroded specimens with localised corrosion pits showed in-cyclic strength degradation. The study also reveals that external strengthening which provides an alternate force path but depends on the strength of the existing reinforcement bars, is able to mitigate the seismic risk of corroded GLD beam-column sub-assemblages to the level of control uncorroded GLD specimen.

• Computers and Concrete
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• 제22권4호
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• pp.365-372
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• 2018

The current design codes present an equivalent frame method (EFM) for the analysis and design of two-way slab structures. However, since the EFM was developed to be suitable for two-way slab structures subjected to gravity loads only, it brings many problems in its application to the analysis of two-way slabs to which gravity and lateral loads are applied simultaneously. Therefore, authors proposed the unified equivalent frame method (UEFM) that can analyze the structural behavior of flat-plate slab systems subjected to gravity and lateral loads in their previous studies. In this study, the UEFM was modified to be applicable to the two-way slab system with beams. In addition, the accuracy of the proposed UEFM was then examined by comparing it to the lateral behaviors of the two-way slab specimens.

• 한국정밀공학회지
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• 제28권4호
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• pp.455-462
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• 2011

This paper is about the design of a new gravity compensator for the lower body exo-skeleton device. The exo-skeleton devices is for increasing the torque of the human body joint for the purpose of helping the disabled, workers in the industry, and military soldiers. So far, most of studied exo-skeleton devices are actuated by the motors, but motors are limited in energy such that a short durability is always a big problem. In this paper, a new gravity compensator is proposed to reduce the torque load applied to human body joints due to gravity. The gravity compensator is designed using a tortional bar spring, and its structure and characteristics are studied through the test and computer simulation. A design concept on the exo-skeleton device using the gravity compensator is presented. An analysis and computer simulation on the torque reduction of the proposed exo-skeleton device that applies and non-applies the gravity compensator are performed.

• 한국군사과학기술학회지
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• 제27권2호
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• pp.127-139
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• 2024

This paper discusses a gravity compensation technique designed to reduce wavefront error caused by gravity during the assembly and alignment of satellite multi-band optical sensor. For this study, the wavefront error caused by gravity was analyzed for the opto-mechanical structure of multi-band optical sensor. Wavefront error, an indicator of optical performance, was computed by using the displacements of optics calculated through structural analysis and optical sensitivity calculated through optical analysis. Since the calculated wavefront error caused by gravity exceeded the allocated budget, the gravity compensation technique was required. This compensation technique reduces wavefront error effectively by applying the compensation load to the appropriate position of the housing tube. This method successfully meets the wavefront error budget for all bands. In the future, a gravity compensation equipment applying this technique will be manufactured and used for assembly and alignment of multi-band optical sensor.

• 화약ㆍ발파
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• 제22권2호
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• pp.45-54
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• 2004

본 연구논문에서는 우리나라 주요 석재인 마천석 원석을 경남 함양군 마천면 기흥리에 위치한 마천석재, 덕우석재을 방문하여 원석과 판석을 색상, 조직, 구성광물, 입도의 차이에 따라 마천석 원석 17개를 채취하였다. 본 현장에서 채취한 시료에 대한 비중. 공극율. 흡수율. Point Load Test, 삼축압축시험, Brazilian Test, 암석학적 시험 및 분석, 화학적 시험 및 분석을 통해 마천석 원석의 물리적 특성을 규명하여 석재의 용도에 따른 타당성을 파악하는데 목적이 있다.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권5호
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• pp.257-263
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• 2000

One of the basic assumptions in the static gait design for a walking robot is that the weight of leg should be negligible compared to that of body, so that the total gravity center is not affected by swing of a leg. Based on the ideal assumption of zero leg-weight, conventional static gait has been simply designed for the gravity center of body to be inside the support polygon, consisting of each support leg's tip position. In case that the weight of leg is relatively heavy, however, while the gravity center of body is kept inside the support polygon, the total gravity center of walking robot can be out of the polygon due to weight of a swinging leg, which causes instability in walking. Thus, it is necessary in the static gait design of a real robot a compensation scheme for the fluctuation in the gravity center. In this paper, a body impedance control is proposed to obtain the total gravity center based on foot forces measured from load cells of a real walking robot and to adjust its position to track the pre-designed trajectory of the corresponding ideal robot's body center. Therefore, the walking stability is secured even in case that the weight of leg has serious influence on the total gravity center of robot.