• 대한토목학회논문집
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• 제43권5호
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• pp.543-553
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• 2023

이 연구는 국내 공용 중인 교량 형식 중 건설 빈도가 가장 높은 RC 슬래브 교량의 공용내하력을 간단하게 평가할 수 있는 방안에 관한 것이다. 다수의 RC 슬래브 교량이 오랜 공용기간으로 인해 상당한 노후화가 진행된 상태지만, 교량의 규모 상 1, 2종 시설물에 포함되지 않아 그동안 안전 관리에 소홀한 측면이 있다. 기존의 이론적 선행연구에서는 실측 처짐 및 실측 고유진동수에 의해 도출된 처짐응답비와 강성저하율의 관계를 이용한 RC 슬래브 교량의 손상도 평가 프로세스(안)이 제시된 바 있다. 이 연구에서는 손상도 평가 프로세스(안)의 적정성을 검토하기 위해 실 교량에 대한 평가 결과를 시설물 안전법의 안전등급 및 Matsui의 노후도 지수와 비교·검토하였다. 또한 손상도 평가 프로세스(안)의 현장적용성을 향상시켜 실측 고유진동수만으로 개략적인 공용내하력을 평가하는 개선된 방안을 제시하였다. 연구결과, 10% 정도의 공용내하력 평가 결과의 오차를 허용하는 경우, 이 연구에서 제시된 방법은 노후화된 RC 슬래브 교량의 안전성 평가 및 유지보수 우선순위 산정 등에 효율적으로 활용될 수 있을 것으로 판단되었다.

• Structural Engineering and Mechanics
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• 제59권6호
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• pp.1095-1120
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• 2016

This paper investigates the change of structural characteristics of steel cable-stayed bridges after cable failure. Cables, considered as the intermediate supports of cable-stayed bridges, can break or fail for several reasons, such as fire, direct vehicle clash accident, extreme weather conditions, and fatigue of cable or anchorage. Also, the replacement of cables can cause temporary disconnection. Because of the structural characteristics with various geometric nonlinearities of cable-stayed bridges, cable failure may cause significant change to the structural state and ultimate behavior. Until now, the characteristics of structural behavior after cable failure have rarely been studied. In this study, rational cable failure analysis is suggested to trace the new equilibrium with structural configuration after the cable failure. Also, the sequence of ultimate analysis for the structure that suffers cable failure is suggested, to study the change of ultimate behavior and load carrying capacity under specific live load conditions. Using these analysis methods, the statical behavior after individual cable failure is studied based on the change of structural configuration, and distribution of internal forces. Also, the change of the ultimate behavior and load carrying capacity under specific live load conditions is investigated, using the proposed analysis method. According to the study, significant change of the statical behavior and ultimate capacity occurs although just one cable fails.

• 복합신소재구조학회 논문집
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• 제5권4호
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• pp.52-57
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• 2014

Due to the advantageous mechanical properties of the fiber reinforced polymeric plastics(FRP), their application in the construction industries is ever increasing trend, as a substitute of structural steel which is highly vulnerable under hazardous environmental conditions (i.e., corrosion, humidity, etc.). In this study, hybrid FRP-concrete composite pile (HCFFT) connection is suggested. The HCFFT is consisted of pultruded FRP unit module, filament wound FRP which is in the outside of mandrel composed of circular shaped assembly of pultruded FRP unit modules, and concrete which is casted inside of the circular tube shaped hybrid FRP pile. Therefore, pultruded FRP can increase the flexural load carrying capacity, filament wound FRP and concrete filled inside can increase axial load carrying capacity. In the study, connection capacity of HCFFT(small and mid size) is investigated throughout experiments and finite element method. From the results of experiments, we suggested the connection methods about HCFFT pile connection.

• Steel and Composite Structures
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• 제37권6호
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• pp.649-662
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• 2020

Although several types of rigid shear connectors have been developed particularly to increase load-carrying capacity, application is limited due to the complicated details of such connection. In this study, push-out tests were performed for specimens with hybrid shear connectors using headed studs and shear plates to identify the effects of each parameter on the structural performance of such shear connection. The test parameters included steel ratios of headed stud to shear plate, connection length, and embedded depth of shear plates. The peak strength and residual strength were estimated using various shear transfer mechanisms such as stud shear, concrete bearing, and shear friction. The hybrid shear connectors using shear plates and headed studs showed large load-carrying capacity and deformation capacity. The peak strength was predicted by the concrete bearing strength of the shear plates. The residual strength was sufficiently predicted by the stud shear strength of headed studs or by shear friction strength of dowel reinforcing bars. Further, the finite element analysis was performed to verify the shear transfer mechanism of the connection with hybrid shear connector.

• Smart Structures and Systems
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• 제3권3호
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• pp.373-384
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• 2007

For structural health monitoring (SHM) of civil infrastructures, displacement is a good descriptor of the structural behavior under all the potential disturbances. However, it is not easy to measure displacement of civil infrastructures, since the conventional sensors need a reference point, and inaccessibility to the reference point is sometimes caused by the geographic conditions, such as a highway or river under a bridge, which makes installation of measuring devices time-consuming and costly, if not impossible. To resolve this issue, a visionbased real-time displacement measurement system using digital image processing techniques is developed. The effectiveness of the proposed system was verified by comparing the load carrying capacities of a steel-plate girder bridge obtained from the conventional sensor and the present system. Further, to simultaneously measure multiple points, a synchronized vision-based system is developed using master/slave system with wireless data communication. For the purpose of verification, the measured displacement by a synchronized vision-based system was compared with the data measured by conventional contact-type sensors, linear variable differential transformers (LVDT) from a laboratory test.

• Steel and Composite Structures
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• 제12권3호
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• pp.183-205
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• 2012

This paper presents an investigation of the effect of inclined stiffeners on the load-carrying capacity of simply-supported hot-rolled steel I-beams under various load conditions. The study is carried out using finite element analysis. A series of beams modeled using 3-D solid finite elements with consideration of initial geometric imperfections, residual stresses, and material nonlinearity are analyzed with and without inclined stiffeners to show how the application of inclined stiffeners can offer a noticeable increase in their lateral-torsional buckling (LTB) capacity. The analysis results have shown that the amount of increase in LTB capacity is primarily dependent on the location of the inclined stiffeners and the lateral unsupported length of the beam. The width, thickness and inclination angle of the stiffeners do not have as much an effect on the beam's lateral-torsional buckling capacity when compared to the stiffeners' location and beam length. Once the optimal location for the stiffeners is determined, parametric studies are performed for different beam lengths and load cases and a design equation is developed for the design of such stiffeners. A design example is given to demonstrate how the proposed equation can be used for the design of inclined stiffeners not only to enhance the beam's bearing capacity but its lateral-torsional buckling strength.

• Steel and Composite Structures
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• 제10권6호
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• pp.475-487
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• 2010

Most of steel structures in various industries are subjected to corrosion due to environmental exposure. Corrosion damage is a serious problem for these structures which may reduce their carrying capacity. These aging structures require maintenance and in many cases, replacement. The goal of this research is to consider the effects of corrosion by developing a model that estimates corrosion loss as a function of exposure time. The model is formulated based on average measured thickness data collected from three severely corroded I-beams (nearly 30 years old). Since corrosion is a time-dependent parameter. Analyses were performed to calculate the lateral buckling capacity of steel beam in terms of exposure time. Minimum curves have been developed for assessment of the remaining lateral buckling capacity of ordinary I-beams based on the loss of thicknesses in terms of exposure time. These minimum curves can be used by practicing engineers for better estimates on the service life of corrosion damaged steel beams.

• 대한토목학회논문집
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• 제33권4호
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• pp.1327-1336
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• 2013

본 논문은 파형 복부판이 수평 곡선 I형 거더의 극한 거동에 미치는 영향을 다룬다. 파형 복부판은 기하학적 특성에 따라 플레이트 거더의 비틂 및 뒴 강성 증진을 위해 적용이 가능하다. 그동안 파형 복부판이 일반 직선 거더의 극한 거동에 미치는 영향을 다룬 많은 연구들이 있었으나, 면외 방향 거동이 주요하게 나타나는 곡선 거더의 극한 거동에 미치는 영향에 대한 연구는 거의 이루어지지 않았다. 이 연구에서는 비탄성-비선형 해석을 통해 파형 복부판 수평 곡선 I형 거더의 극한 거동을 다룬다. 본 해석 연구에서는 파형 복부판을 갖는 곡선 거더의 극한 거동에 영향을 미칠 수 있는 기하학적 인자로써, 곡선 거더의 횡방향 비지지 길이와 사잇각, 복부판의 파고 및 파장이 주요 매개변수로 고려되었다. 본 해석 연구를 통해, 각 매개변수 변화에 따른 극한 거동 및 내하력 변화를 분석하고, 일반 판형 복부판이 적용된 거더의 내하력과 비교하여 파형 복부판이 내하력 증진에 미치는 영향을 도출하였다. 본 해석 결과에 따르면, 높은 비틂 및 뒴 강성에 의해 파형 복부판은 곡선 거더의 내하력 증진에 효과적인 것으로 나타났다. 그러나 곡선 거더의 곡률 또는 사잇각이 작은 경우, 파형 판의 아코디언 효과에 의해 오히려 내하력이 감소될 수 있다는 것 또한 나타났다.

• 해양환경안전학회지
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• 제17권4호
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• pp.315-322
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• 2011

전 세계적으로 연안양식산업의 중요성은 날로 증대되고 있지만, 반폐쇄성 내만의 연안환경은 양식의 장기화 및 과밀식에 의하여 연안 오염이 가중되고 있다. 지속적인 연안양식을 위하여, 해양생태계에 부하를 주지 않는 생태학적 수용능력 산정을 통한 친환경적 어장관리의 필요성이 대두되고 있다. 생태학적 수용능력 산정 모델링의 경우, 전체 생태계와 모든 양식활동을 고려해야 하기 때문에, 그 개발 및 적용에 있어 아직 초기단계에 있다. 대안으로, 양식장의 생태학적 능률을 산정하는 생태지표에 대한 요구가 있다. 본 연구는 대상해역의 기초생산력과 굴 양식장의 섭취율을 고려한 여과압 지표를 사용하여 생태학적 수용능력 산정을 시도하였다. 2008년, 거제한산만에 시설되어있는 굴 양식장의 여과압 지표값은 0.203으로 나타났으며, 생산량은 4,935M/T로서 49개체/$m^3$로 시설되어 있다. 거제한산만의 현재 시설된 굴 양식장과 환경적 특성에 따라, 해양생태계에 부하를 주지 않는 생태학적 수용능력에 관해 새로이 산정된 여과압 지표는 0.102였다. 결과적으로, 거제한산만의 굴 양식장의 생태학적 수용능력은 현 생산량에서 49.8% 저감된 2,480M/T, 25개체/$m^3$였고, 이는 생태학적 과정, 종, 군집에 현저한 변화를 주지 않고서 거제한산만에 도입될 수 있는 양식장의 수용능력을 나타낸다. 본 연구는 굴 양식장의 지속적인 생산을 위하여 생태학적 수용능력을 산정할 수 있는 생태지표를 활용하였으며, 이는 친환경적 어장관리의 과학적 근거로 활용될 수 있다.

• Steel and Composite Structures
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• 제33권2호
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• pp.225-243
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• 2019

Cold-formed steel (CFS) sections when used as primary load carrying members often require additional strengthening for retrofitting purposes. In some cases, it is also necessary to reduce deflections in order to satisfy serviceability requirements. The introduction of angle sections, screwed to the webs so as to act as external stiffeners, has the potential to both increase flexural strength as well as reduce deflections. This paper presents the results of ten four-point bending tests, on built-up CFS sections, both open and closed, with different stiffening arrangements. In the laboratory tests, the stiffening arrangements increased the moment capacity and stiffness of the CFS beams by up to 85% and 100% respectively. The increase in moment capacity was more evident for the open sections, while that reduction in deflection was largest for the closed sections.