• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.185-192
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• 2021

본 연구에서는 거푸집 패널이 부착된 실물 스케일의 중공슬래브 Mock-up을 제작하여 즉시 처짐 및 장기 처짐에 대한 플랫 플레이트 중공 슬래브의 안전성을 평가하고자 한다. 중공재가 적용된 Mock-up 실험체의 중공률은 24%로 설계하였다. 콘크리트 블록 하중 재하 시 슬래브의 가장 중앙부의 처짐인 No2의 경우 재하 시 처짐이 8.88mm 발생하였으며 이는 즉시 처짐에 대한 기준 값(l_n/240=17.93mm)에 비하여 안전한 값을 나타내고 있다. 3개월간 처짐 량 계측 결과, 중앙부 처짐 량은 초기 처짐에서 6.792mm 더 추가되어 처짐이 발생하였지만, 이는 국내 구조 기준에서 제시하고 있는 사용하중에 의한 기준 값을 만족하고 있는 것으로 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제42권1호
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• pp.20-26
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• 2014

본 연구에서는 유한요소해석을 이용하여 응력적층 바닥판의 구조성능을 평가하였다. 바닥판의 구조성능은 처짐과 응력, 압체력의 변화로 평가할 수 있다. 하중 재하 후 바닥판의 처짐 형상을 확인한 결과 하나의 판처럼 거동하는 것을 확인하였다. 이는 압체력에 의해 각 부재 사이에 마찰력이 작용했기 때문이다. 또한 초기 압체력과 산출된 압체력을 비교한 결과 바닥판의 처짐과 함께 압체력이 감소했다. 이는 하중에 의해 바닥판의 변형이 발생하면서 작용하는 힘이 줄어듦에 따라 압체력이 감소한 것으로 판단된다. 그러나 재료의 소성 특성이 제대로 반영되지 않았기 때문에 잔류응력과 잔류변형이 고려되지 않았으므로 추후 이에 대한 연구가 필요하다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.579-584
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• 2001

The reinforced concrete(RC) beam is developed cracks because the compression strength of concrete is strong but the tensile strength is weak. The structural strength and stiffness is decreased by reduction of tension resistance capacity of concrete due to the developed cracks. Using the fiber reinforced concrete that is increased the flexural strength and tensile strength at tensile part can enhance the strength and stiffness of concrete structure and decrease the tensile flexural cracks and deflection. Therefore, The reinforced concrete used the fiber reinforced concrete at tensile part ensure the safety and serviceability of the concrete structures. In this study, analytical model of a dual concrete beam that is composed of the normal strength concrete at compression part and the high tensile strength concrete at tensile part is developed by using the equilibrium condition of forces and compatibility condition of strains and is parted into elastic analytical model and ultimate analytical model. Three group of test beam that is formed of one reinforced concrete beam and two dual concrete beams for each steel reinforcement ratio is tested to examine the flexural behavior of dual concrete beams. The comparative study of total nine test beams is shown that the ultimate load of a dual concrete beams relative to the reinforced concrete beams have an increase in approximately 30%. In addition, the initial flexural rigidity, as used here, refer to the slope of load-deflection curves in elastic state is increased and the deflection is decreased.

• Smart Structures and Systems
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• 제14권3호
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• pp.419-444
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• 2014

Within this paper a new approach for early damage detection in rotor blades of wind energy converters is presented, which is shown to have a more sensitive reaction to damage than eigenfrequency-based methods. The new approach is based on the extension of Gasch's proportionality method, according to which maximum oscillation velocity and maximum stress are proportional by a factor, which describes the dynamic behavior of the structure. A change in the proportionality factor can be used as damage indicator. In addition, a novel deflection sensor was developed, which was specifically designed for use in wind turbine rotor blades. This deflection sensor was used during the experimental tests conducted for the measurement of the blade deflection. The method was applied on numerical models for different damage cases and damage extents. Additionally, the method and the sensing concept were applied on a real 50.8 m blade during a fatigue test in the edgewise direction. During the test, a damage of 1.5 m length was induced on the upper trailing edge bondline. Both the initial damage and the increase of its length were successfully detected by the decrease of the proportionality factor. This decrease coincided significantly with the decrease of the factor calculated from the numerical analyses.

• 제어로봇시스템학회논문지
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• 제13권1호
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• pp.72-78
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• 2007

Determination of the local vertical is not trivial for a moving vehicle and in general will require corrections for the Earth geophysical deflection. The vehicle's local vertical can be estimated by INS integration with initial alignment in SDINS(Strap Down INS) system. In general, the INS has drift error and it cause the performance degradation. In order to compensate the drift error, GPS/INS augmented system is widely used. And in the event that GPS is denied or unavailable, celestial navigation using star tracker can be a backup navigation system especially for the military purpose. In this celestial navigation system, the vehicle's position determination can be achieved using more than two star trackers, and the accuracy of position highly depends on accuracy of local vertical direction. Modern tilt sensors or accelerometers are sensitive to the direction of gravity to arc second(or better) precision. The local gravity provides the direction orthogonal to the geoid and, appropriately corrected, toward the center of the Earth. In this paper the relationship between direction of center of the Earth and actual gravity direction caused by geophysical deflection was analyzed by using precision orbit simulation program embedded the JGM-3 geoid model. And the result was verified and evaluated with mathematical gravity vector model derived from gravitational potential of the Earth. And also for application purpose, the performance variation of pure INS navigation system was analyzed by applying precise gravity model.

• Computers and Concrete
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• 제10권3호
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• pp.241-258
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• 2012

The need for long-span members increases gradually in recent years, which makes issues not only on ultimate strength but also on excessive deflection of horizontal members important. In building structures, the post-tension methods with unbonded tendons are often used for long-span members to solve deflection problems. Previous studies on prestressed flexural members with unbonded tendons, however, were mostly focused on the ultimate strength. For this reason, their approaches are either impossible or very difficult to be implemented for serviceability check such as deflection, tendons stress, etc. Therefore, this study proposed a flexural behavior model for post-tensioned members with unbonded tendons that can predict the initial behavior, before and after cracking, service load behavior and ultimate strength. The applicability and accuracy of the proposed model were also verified by comparing with various types of test results including internally and externally post-tensioned members, a wide range of reinforcement ratios and different loading patterns. The comparison showed that the proposed model very accurately estimated both the flexural behavior and strength for these members. Particularly, the proposed model well reflected the effect of various loading patterns, and also provided good estimation on the flexural behavior of excessively reinforced members that could often occur during reinforcing work.

• Structural Engineering and Mechanics
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• 제77권1호
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• pp.1-17
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• 2021

The influence of prestress force on the fundamental frequency and static deflection shape of uncracked Prestressed Concrete (PC) beams with a parabolic bonded tendon was examined in this paper. Due to the conflicts among existing theories, the analytical solutions for properly considering the dynamic and static behavior of these members is not straightforward. A series of experiments were conducted for a total period of approximately 2.5 months on a PC beam made with high strength concrete, subsequently and closely to the 28 days of age of concrete. Specifically, the simply supported PC member was short term subjected to free transverse vibration and three-point bending tests during its early-age. Subsequently, the experimental data were compared with a model that describes the dynamic behavior of PC girders as a combination of two substructures interconnected, i.e., a compressed Euler-Bernoulli beam and a tensioned parabolic cable. It was established that the fundamental frequency of uncracked PC beams with a parabolic bonded tendon is sensitive to the variation of the initial elastic modulus of concrete in the early-age curing. Furthermore, the small variation in experimental frequency with time makes doubtful its use in inverse problem identifications. Conversely, the relationship between prestress force and static deflection shape is well described by the magnification factor formula of the "compression-softening" theory by assuming the variation of the chord elastic modulus of concrete with time.

• 한국전산구조공학회논문집
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• 제24권1호
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• pp.87-95
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• 2011

본 논문에서는 비선형해석이라는 복잡한 과정을 거치지 않고도 사장교 시스템의 초기형상을 효율적이고 합리적으로 결정하는 방법을 제시하고자 한다. 사장교 시스템의 초기형상해석이라 함은 주형의 수직 처짐과 휨모멘트, 주탑의 수평변위와 휨모멘트를 최소화하면서, 고정하중과 평형을 이룰 수 있는 케이블의 장력과 무응력길이를 결정하는 방법으로 이때, 케이블이 정착되는 주형의 수평위치, 주탑의 수직위치가 변하지 않아야 한다. 본 연구에서는 주형과 주탑의 케이블 정착부에서 힘의 평형조건을 이용하여 주형의 수직 처짐과 주탑의 수평변위를 효과적으로 제어할 수 있는 장력 산정법을 사장교의 형태별로 정리하여 제시하였으며, 2차원 사장교 예제들에 대하여 기존 연구의 방법들과 장력, 주형의 모멘트와 처짐 등을 비교하였다. 또한 3차원 실교량에 대해 Improved TCUD법으로 초기형상해석을 수행하여 그 결과와 비교함으로서 본 방법의 정확성을 입증하고자 하였다.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.167-174
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• 2016

Recently laminated plates like composite materials has been used in a various field to grow the specific strength of the composition. However, delamination area caused by barely visible impact damage has potential risk that it can raise buckling of the delaminated plate. Because it can interrupt compressive behavior of laminated plates and reduce their strength, the whole structure can't be constituted by these materials. Many studies assume that behavior of the delaminated plate which is in lamanated plates equals theoretical buckling but their actual motion doesn't coincide because of initial imperfections of materials like deflection, residual stress, eccentricity and so on. In this paper, we change laminated plates with initial delamination into a beam of rectangular cross section with the initial crack and analyze compressive behavior according to initial imperfections through finite element method(FEM). Consequently analysis results show that behavior of laminated plates involving delamination differs from ideal buckling of the delaminated plate in actual conditions and we can predict its motion through imperfections relationship.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.356-359
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• 2005

Ionic-polymer-metal-composite(IPMC), one of new actuation materials of electroactive polymers plated with noble metallic electrodes is known for the fast bending upon electric field. The IPMC strip bends towards anode under electrical field. It has many merits of low driving voltage, quick responsiveness, high durability, possibility of miniaturizability. In this paper, we studied for developing the large deflection of IPMC according several fabricating parameters. We measured the large deflection by the different process of sandpaper and sandblasting in surface treatment, the initial compositing process and the surface electroding process, and the different counter ions in ion exchanging process. In fundamental, the displacement of IPMC strip depends on voltage magnitude and applied signal frequency and its maximum deformation is observed at a critical frequency, resonant frequency.