• Structural Engineering and Mechanics
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• 제81권4호
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• pp.513-522
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• 2022

Steel-concrete composite segments replacing the conventional reinforced concrete segments can provide the rectangular shield tunnel superiorities on bearing capacity, ductility and economy. A simplified model with high-efficiency on computation is proposed for investigating the nonlinear response of the rectangular tunnel lining composed of composite segments. The simulation model is developed by an assembly of nonlinear fiber beam elements and spring elements to express the transfer mechanism of forces through components of composite segments, and radial joints. The simulation is conducted with the considerations of material nonlinearity and geometric nonlinearity associated with the whole loading process. The validity of the model is evaluated through comparison of the proposed nonlinear simulation with results obtained from the full-scale test of the segmental tunnel lining. Furthermore, a parameter study is conducted by means of the simplified model. The results show that the stiffness of the radial joint at haunch of the ling and the thickness of inner steel plate of segments have remarkable influence on the behaviour of the lining.

• Steel and Composite Structures
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• 제20권1호
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• pp.1-20
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• 2016

The strength and stiffness of the steel beams to concrete-filled tubular columns connections are significantly reduced if the thick-walled components are used. However, the thick-walled tubes used for columns can largely reduce the demand for space and increase the strength-to-weight ratio. This paper describes the cyclic performance of extended through-diaphragm connections between steel beams and thick-walled concrete-filled tubular columns improved with fillets around the diaphragm corners. Test on one full-scale connection was conducted to assess the seismic behavior of the connection in terms of strength, stiffness, ductility, deformation, energy dissipation, and strain distribution. It is shown that the fillets and extended through-diaphragm can alleviate the stress concentration in the connection and thus improve the seismic performance. The test results demonstrate that the through-diaphragm connections with thick-walled concrete-filled tubular columns can offer sufficient energy dissipation capacity and ductility appropriate for its potential application in seismic design.

• Steel and Composite Structures
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• 제6권2호
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• pp.159-182
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• 2006

Current fire design codes for determining the temperature within the structural elements that form part of a complete building are based on isolated member tests subjected to the standard fire. However, the standard time-temperature response bears little relation to real fires and doesn't include the effects of differing ventilation conditions or the influence of the thermal properties of compartment linings. The degree to which temperature uniformity is present in real compartments is not addressed and direct flame impingement may also have an influence, which is not considered. It is clear that the complex thermal environmental that occurs within a real building subject to a natural fire can only be addressed using realistic full-scale tests. To study global structural and thermal behaviour, a research project was conducted on the eight storey steel frame building at the Building Research Establishment's Cardington laboratory. The fire compartment was 11 m long by 7 m wide. A fire load of $40kg/m^2$ was applied together with 100% of the permanent actions and variable permanent actions and 56% of live actions. This paper summarises the experimental programme and presents the time-temperature development in the fire compartment and in the main supporting structural elements. Comparisons are also made between the test results and the temperatures predicted by the structural fire Eurocodes.

• Wind and Structures
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• 제26권2호
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• pp.75-87
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• 2018

A large number of low-rise buildings experienced serious roof covering failures under strong wind while few suffered structural damage. Clay and concrete tiles are two main kinds of roof covering. For the tile roof system, few researches were carried out based on Finite Element (FE) analysis due to the difficulty in the simulation of the interface between the tiles and the roof sheathing (the bonding materials, foam or mortar). In this paper, the FE analysis of a single clay or concrete tile with foam-set or mortar-set were built with the interface simulated by the equivalent nonlinear springs based on the mechanical uplift and displacement tests, and they were expanded into the whole roof. A detailed wind tunnel test was carried out at Tongji University to acquire the wind loads on these two kinds of roof tiles, and then the test data were fed into the FE analysis. For the purpose of validation and calibration, the results of FE analysis were compared with the full-scale performance ofthe tile roofs under simulated strong wind impact through one-of-a-kind Wall of Wind (WoW) apparatus at Florida International University. The results are consistent with the WoW test that the roof of concrete tiles with mortar-set provided the highest resistance, and the material defects or improper construction practices are the key factors to induce the roof tiles' failure. Meanwhile, the staggered setting of concrete tiles would help develop an interlocking mechanism between the tiles and increase their resistance.

• 한국지반환경공학회 논문집
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• 제15권9호
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• pp.69-75
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• 2014

기존에 사용되던 사각형 낙석방지망은 낙석에 의한 충격 완화를 위한 장치가 없어 적층 현상 등을 해결할 수 없으며 과도한 충격으로 철망이 파괴되는 문제 등이 지적되고 있었다. 여러 문제점이 복합적으로 발생하면서 매년 낙석 방지망 자체의 파괴에 의해 많은 피해가 발생하고 있다. 따라서 본 연구에서는 기존의 표준형 낙석방지망의 낙석방호 실패 원인을 고찰하고 설계 시 예상 낙석에너지를 파악하여 적정한 흡수에너지를 가진 육각 낙석방지망을 개발하였다. 또한 실내실험과 실대형실험을 통해 기존 낙석 방지망과의 성능차를 파악하여 육각 낙석방지망의 적용 가능성을 파악하고자 하였다. 실내실험과 실대형실험결과 낙석과 같은 하중 재하 시 육각 낙석방지망에 작용하는 응력은 스프링형 지지 장치에 의해 응력이 완화되어 충격에 의한 소성파괴에 대한 저항성이 우수한 반면 사각 낙석방지망의 경우 작용하는 응력이 직접적으로 낙석방지망에 작용함으로써 하중에 대한 저항력이 육각 낙석방지망보다 효율이 적은 것으로 판단된다.

• 한국터널지하공간학회 논문집
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• 제26권2호
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• pp.91-111
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• 2024

전력구 터널은 송전선로 지중화 사업의 일환으로 대부분의 경우 쉴드 TBM을 활용하여 건설된다. TBM 챔버는 터널 내부 중 유일하게 암반과 흙을 마주하는 공간이며, 붕락과 부딪힘 사고 등 사고노출 빈도가 가장 높은 곳이다. 현재 챔버 외부에서 디스크커터 마모정도를 측정할 수 있는 방법이 부재하기 때문에 근로자의 수시점검이 필수적이다. 이에 본 연구에서는 TBM 챔버 내부 안전사고를 예방하고, 챔버 오픈회수 절감을 통해 공사기간 단축의 효과를 기대하기 위하여 디스크커터 마모측정 기술 개념을 정립하고, 시작품을 제작하였다. 선행기술을 고찰하여 자기센서가 굴착환경에서 가장 적합하다고 판단하여, 자기센서, 무선통신 모듈, 전원공급, 외부 케이싱, 그리고 모니터링 시스템을 종합한 마모측정 센서 패키지를 개발하였다. 실제 굴착환경에서 시작품 성능검증을 수행하기 위해 3.6 m 토압식 쉴드 TBM을 활용한 실대형 굴진시험을 수행하였다. 실대형 굴진시험 결과 8개의 시작품 중 5개가 정상적으로 작동하였다. 최대 3,000 kN의 추력과 1.5 RPM의 회전속도 안에서 센서측정값이 무선통신을 통해 시스템에 원활하게 표출되는지 확인하였고, 센서 케이싱이 파손되지 않아 내구성을 확보하는 것으로 분석되었다.

• Smart Structures and Systems
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• 제7권5호
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• pp.379-392
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• 2011

This paper presents a multi-functional system, consisting of a magnetorheological (MR) damper and an electromagnetic induction (EMI) device, and its applications in stay cables. The proposed system is capable of offering multiple functions: (1) mitigating excessive vibrations of cables, (2) estimating cable tension, and (3) harvesting energy for wireless sensors used health monitoring of cable-stayed bridges. In the proposed system, the EMI device, consisting of permanent magnets and a solenoid coil, can converts vibration energy into electrical energy (i.e., induced emf); hence, it acts as an energy harvesting system. Moreover, the cable tension can be estimated by using the emf signals obtained from the EMI device. In addition, the MR damper, whose damping property is controlled by the harvested energy from the EMI device, can effectively reduce excessive cable vibrations. In this study, the multi-functionality of the proposed system is experimentally evaluated by conducting a shaking table test as well as a full-scale stay cable in a laboratory setting. In the shaking table experiment, the energy harvesting capability of the EMI device for wireless sensor nodes is investigated. The performance on the cable tension estimation and the vibration mitigation are evaluated using the full-scale cable test setup. The test results show that the proposed system can sufficiently generate and store the electricity for operating a wireless sensor node twice per day, significantly alleviate vibration of a stay cable (by providing about 20% larger damping compared to the passive optimal case), and estimate the cable tension accurately within a 2.5% error.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.469-472
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• 2004

There have been numerous accelerated aging laboratory tests for evaluating suitability of polymeric materials and devices. Aging test for materials and its full scale device has been conducted, but poor correlation of aging test such as service experience were observed. Service experience plays a key role in the utility section of composite insulators. A meaningful and reliable accelerated aging test is needed for evaluating composite insulator. During the service these insulators are subjected to aging stress such as humidity, pollution, and electrical field, and erosion and tracking of the weathershed occurs. This paper presents the criteria of reliability evaluation and evaluation facilities for 22.9 kV suspension composite insulator. We adopt the criteria of reliability evaluation consist of two test methods. One is CEA tracking wheel test for examining the tracking and erosion performance of composite insulator. The other is multi-stress aging test for examining effects of environmental factors such as UV, temperature, humidity, etc on composite insulator.

• Steel and Composite Structures
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• 제23권5호
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• pp.611-621
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• 2017

This paper presents an investigation on the fire resistance of high strength fiber reinforced concrete filled box columns (CFBCs) under combined temperature and loading. Two groups of full-size specimens were fabricated. The control group was a steel box filled with high-strength concrete (HSC), while the experimental group consisted of a steel box filled with high strength fiber concrete (HFC) and two steel boxes filled with fiber reinforced concrete. Prior to fire test, a constant compressive load (i.e., load level for fire design) was applied to the column specimens. Thermal load was then applied on the column specimens in form of ISO 834 standard fire curve in a large-scale laboratory furnace until the set experiment termination condition was reached. The test results show that filling fiber concrete can improve the fire resistance of CFBC. Moreover, the configuration of longitudinal reinforcements and transverse stirrups can significantly improve the fire resistance of CFBCs.

• 한국건설순환자원학회논문집
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• 제1권3호
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• pp.163-172
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• 2013

This paper presents a comprehensive review of recent advances in ultra-high performance concrete (UHPC). Fundamental characteristics of UHPC are elaborated with focus on its material constituents, mixing, and formulation procedures. Use of state-of-the-art materials such as carbon nanotubes or nano-silica is discussed as well, whose inclusion may enhance the performance of UHPC. The review evaluates supplementary treatment methods (e.g., pressuring curing) and identifies applicable standard test methods for determining the properties and behavior of UHPC. Site implementation is provided to link laboratory research with full-scale application. Research needs are suggested to further develop UHPC technologies from technical and socio-economical perspectives.