• Computers and Concrete
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• 제20권5호
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• pp.605-616
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• 2017

Concrete filled steel tubular (CFST) composite girder is a new type of structures for bridge constructions. The existing design codes cannot be used to predict the thermal stress in the CFST truss girder structures under solar radiation. This study is to develop the temperature gradient curves for predicting thermal stress of the structure based on field and laboratory monitoring data. An in-field testing had been carried out on Ganhaizi Bridge for over two months. Thermal couples were installed at the cross section of the CFST truss girder and the continuous data was collected every 30 minutes. A typical temperature gradient mode was then extracted by comparing temperature distributions at different times. To further verify the temperature gradient mode and investigate the evolution of temperature fields, an outdoor experiment was conducted on a 1:8 scale bridge model, which was installed with both thermal couples and strain gauges. The main factors including solar radiation and ambient temperature on the different positions were studied. Laboratory results were consistent with that from the in-field data and temperature gradient curves were obtained from the in-field and laboratory data. The relationship between the strain difference at top and bottom surfaces of the concrete deck and its corresponding temperature change was also obtained and a method based on curve fitting was proposed to predict the thermal strain under elevated temperature. The thermal stress model for CFST composite girder was derived. By the proposed model, the thermal stress was obtained from the temperature gradient curves. The results using the proposed model were agreed well with that by finite element modelling.

• 에너지공학
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• 제24권4호
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• pp.71-80
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• 2015

PVC 프레임의 취약한 강도를 보완하기 위해 사용되는 철재 보강재는 상대적으로 높은 열전도 특성으로 인해 PVC 프레임의 전체적인 열 성능을 떨어뜨리는 역할을 한다. 본 연구는 철재 보강재의 타공을 통해 표면적을 줄임으로서 전열 면적의 감소를 통한 열저항 특성을 개선하고, 감소된 만큼 두께를 높임으로서 타공으로 인한 강도 저하를 보완하였다. 이에 대한 성능을 평가하기 위해 PVC frame, PVC frame + original steel stiffener, PVC frame + 30% perforated steel stiffener, PVC frame + 50% perforated steel stiffener, PVC frame + 65% perforated steel stiffener 등 5개의 시험체를 구성하였으며, 시험 방법은 수식과 시뮬레이션에 의한 방법을 적용하였다. 시험 결과 PVC frame + 65% perforated steel stiffener이 열저항 특성과 강도특성에서 가장 높은 것으로 평가되었다.

• Earthquakes and Structures
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• 제16권1호
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• pp.11-28
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• 2019

This article investigates the response of Integral Abutment Bridges (IAB) when subjected to a sequence of seasonal thermal loading of the deck followed by ground seismic shaking in the longitudinal direction. Particular emphasis is placed on the effect of pre-seismic thermal Soil-Structure Interaction (SSI) on the seismic performance of the IAB, as well as on the ability of various backfills configurations, to minimize the unfavorable SSI effects. A series of two-dimensional numerical analyses were performed for this purpose, on a complete backfill-integral bridge-foundation soil system, subjected to seasonal cyclic thermal loading of the deck, followed by ground seismic shaking, employing ABAQUS. Various backfill configurations were investigated, including conventional dense cohesionless backfills, mechanically stabilized backfills and backfills isolated by means of compressive inclusions. The responses of the investigated configurations, in terms of backfill deformations and earth pressures, and bridge resultants and displacements, were compared with each other, as well as with relevant predictions from analyses, where the pre-seismic thermal SSI effects were neglected. The effects of pre-seismic thermal SSI on the seismic response of the coupled IAB-soil system were more evident in cases of conventional backfills, while they were almost negligible in case of IAB with mechanically stabilized backfills and isolated abutments. Along these lines, reasonable assumptions should be made in the seismic analysis of IAB with conventional sand backfills, to account for pre-seismic thermal SSI effects. On the contrary, the analysis of the SSI effects, caused by thermal and seismic loading, can be disaggregated in cases of IAB with isolated backfills.

• Structural Engineering and Mechanics
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• 제50권3호
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• pp.305-322
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• 2014

Reliability-based design limit states and associated partial load factors provide a consistent level of design safety across bridge types and members. However, limit states in the current AASHTO LRFD have not been developed explicitly for the situation encountered by integral abutment bridges (IABs) that have unique boundary conditions and loads with inherent uncertainties. Therefore, new reliability-based limit states for IABs considering the variability of the abutment support conditions and thermal loading must be developed to achieve IAB designs that achieve the same safety level as other bridge designs. Prestressed concrete girder bridges are considered in this study and are subjected to concrete time-dependent effects (creep and shrinkage), backfill pressure, temperature fluctuation and temperature gradient. Based on the previously established database for bridge loads and resistances, reliability analyses are performed. The IAB limit states proposed herein are intended to supplement current AASHTO LRFD limit states as specified in AASHTO LRFD Table 3.4.1-1.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.195-202
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• 2004

After the 1990's, Guss asphalt has chosen in Korea for using in pavement of a steel deck bridge because of it's distinguish ability about water proof and so on. But on the other hand it may cause server stress and displacement on the bridge as it is treated using very high temperature ranging from 220℃ to 260℃. Therefore it is critical to estimate the thermal effect of Guss asphalt on the steel deck bridge before the width and pattern of the unit portion are decided to minimize impact. In this study, a serious of numerical tests of the some steel box bridges were idealized were conducted to verify the feasibility of numerical value analysis. The parametric study was performed to present design proposal about the Box section dimensions and the diaphragm spacing.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.693-696
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• 2006

In massive hardening concrete structures, early age thermal cracking due to the heat of hydration may occur. There are many massive structures in Incheon bridge project and they have to be carefully treated to prevent thermal cracking. In this paper, an example of analyzed and measured results of hydration heat of pile caps in the Incheon bridge project was represented. Finite element simulations were carried out before casting and curing method was determined using the analyzed result. Sensors were installed before casting and temperature and strain of concrete was measured during curing. Gathered data were compared with the analyzed data and selected control method to prevent cracking was verified. Analyzed result gave good agreement and very few cracking could be found.

• 한국산학기술학회논문지
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• 제17권8호
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• pp.133-139
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• 2016

합리적인 설계 온도하중을 산정하기 위하여, 강상자형교의 시험체가 실물 규모로 제작되었다. 박스단면의 크기는 폭 2.0m, 높이 2.0m, 길이 3.0m이며, 슬래브의 두께는 17 cm이다. 온도 게이지를 사용하여 1년간 온도를 측정하였다. 또한 인근에 시험체와 유사한 방향으로 설치된 같은 형식의 실교량에서도 같은 기간에 온도를 측정하였다. 교량시험체는 21지점, 실교량에서는 19지점에서 온도를 측정하고 각 측점에서 측정온도를 통계 처리하여 추세선과 표준 오차를 산정하고, Euro code에서 제시한 대기온도 $24^{\circ}C{\sim}38^{\circ}C$에서 각 지점의 유효온도를 산정하였다. 교량시험체 모형에서는 $35^{\circ}C$이상에서 Euro code와 실교량과 비교하여 유효온도가 $2^{\circ}C{\sim}3^{\circ}C$ 정도 높게 산정되었다. 제시된 시험체와 실교량에서 Euro code에 대한 유효온도의 상관계수는 87.4%, 93.2%로 계산되었다. 국내 도로교설계기준에 따르면 합성교에서 최고기온은 $40^{\circ}C$로 규정하고 있는데 이는 본 연구에서 산정된 실교량과 Euro code의 유효온도와 거의 근접하는 것으로 평가된다. 각 지역별 최고 온도에 대한 Contour map에서 산정한 대기온도별 최고온도와 본 연구에서 제시한 유효온도를 접목하면 국내 교량 설계 시 각 지역의 특성을 고려한 설계기준이 확립될 수 있을 것이다.

• Earthquakes and Structures
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• 제13권5호
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• pp.429-442
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• 2017

Dry bridges have been widely applied in the Qinghai-Tibet Railway (QTR) to minimize the thermal disturbance of engineering to the permafrost. However, because the Qinghai-Tibet Plateau is an area with a high potential occurrence of earthquakes, seismic action can easily destroy the dry bridges. Therefore, a three-dimensional numerical model, with consideration of the soil-pile interactions, is established to investigate the thermal characteristics and their impact on the seismic response of the dry bridge in permafrost region along the QTR. The numerical results indicate that there exist significant differences in the lateral displacement, shear force, and bending moment of the piles in different thermal conditions under seismic action. When the active layer become from unfrozen to frozen state, the maximum displacement of the bridge pile reduces, and the locations of the zero and peak values of the shear force and bending moment also change. It is found that although the higher stiffness of frozen soil confines the lateral displacement of the pile, compared with unfrozen soil, it has an adverse effect on the earthquake energy dissipation capacity.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.236-240
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• 2009

Dry wall using steel stud has the advantage of possibility to install various building, so it used to many buildings inside and outside of the country very rapidly. Though Light gauge steel framed housing offers many advantages to the consumer and the builder, the use of steel studs in wall system cause thermal problems such as thermal performance and pattern staing on walls. The present study has been conducted to observe effect of stud by the shape, and two kind of stud is made for this test to compare thermal performance. The test was conducted by setting those stud on the chamber and heating them. As the results of test and photograping by using TVS, there was temperature gap of each stud, and surface temperature of each section was appeared differently due to shape of stud delaying thermal bridge.

• 한국구조물진단유지관리공학회 논문집
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• 제17권4호
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• pp.91-100
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• 2013

이 연구에서는 기존아파트 외벽체의 단열 성능저하 및 보수보강에 필요한 기초 자료를 만들기 위해서 아파트의 구조체 단열성능 측정분석과 함께 단열하자에 대한 기준수립 및 평가를 하고자 한다. 또한 아파트 건축물 구조체의 열교 및 결로발생 부분을 예측하고자 하였다. 한편 시공연도별 분석에 의하여 단열기준 및 시간 경과에 따른 단열성능 정도를 분석하기 위함이다.