Behavior of composite box bridge girders under localized fire exposure conditions

Gang Zhang,Venkatesh Kodur,Weifa Yao,Qiao Huang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.2

This paper presents results from experimental and numerical studies on the response of steel-concrete composite box bridge girders under certain localized fire exposure conditions. Two composite box bridge girders, a simply supported girder and a continuous girder respectively, were tested under simultaneous loading and fire exposure. The simply supported girder was exposed to fire over 40% of its span length in the middle zone, and the two-span continuous girder was exposed to fire over 38% of its length of the first span and full length of the second span. A measurement method based on comparative rate of deflection was provided to predict the failure time in the hogging moment zone of continuous composite box bridge girders under certain localized fire exposure condition. Parameters including transverse and longitudinal stiffeners and fire scenarios were introduced to investigate fire resistance of the composite box bridge girders. Test results show that failure of the simply supported girder is governed by the deflection limit state, whereas failure of the continuous girder occurs through bending buckling of the web and bottom slab in the hogging moment zone. Deflection based criterion may not be reliable in evaluating failure of continuous composite box bridge girder under certain fire exposure condition. The fire resistance (failure time) of the continuous girder is higher than that of the simply supported girder. Data from fire tests is successfully utilized to validate a finite element based numerical model for further investigating the response of composite box bridge girders exposed to localized fire. Results from numerical analysis show that fire resistance of composite box bridge girders can be highly influenced by the spacing of longitudinal stiffeners and fire severity. The continuous composite box bridge girder with closer longitudinal stiffeners has better fire resistance than the simply composite box bridge girder. It is concluded that the fire resistance of continuous composite box bridge girders can be significantly enhanced by preventing the hogging moment zone from exposure to fire. Longitudinal stiffeners with closer spacing can enhance fire resistance of composite box bridge girders. The increase of transverse stiffeners has no significant effect on fire resistance of composite box bridge girders.

콘크리트 박스거더교의 상판 아스팔트 두께에 따른 최저 설계 유효온도 산정

이성행 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.12

This study examined the minimum effective temperature adjustment value and effective temperature in winter according to the thickness of the upper asphalt pavement of a concrete box girder bridge. Three concrete box girder specimens with asphalt thicknesses of 0 mm, 50 mm, and 150 mm were manufactured. The temperature data were measured during the winter, and the effective temperature was analyzed. Seventeen and 23 temperature sensors were attached to each model, and a set of 3604 temperature data was measured for three months, 48 sets a day. The lowest effective temperature in winter was calculated based on this. The effective temperature of -15℃ was analyzed to be –9.9℃, -9.2℃, and -6.8℃ at 0mm, 50mm, and 150mm, respectively. At the lowest temperature (-15~13°C), each model was calculated to be 0.3°C to +1.7°C higher than the Eurocode, and the overall value was similar to the Eurocode. As a result of the analysis, the adjustment value of the minimum effective temperature according to the thickness of the asphalt was derived as +0.5℃ and +2.7℃ for 50mm and 150mm, respectively, based on 0mm. In the 50mm model designed the most, the effective temperature of the concrete bridge does not increase much compared to the steel bridge. Judging from the minimum effective temperature calculated in this study, it was judged that the minimum design temperature of the highway bridge design criteria in the normal climate area of the concrete bridge needs to be re-examined from –5℃ to -9.2℃. 본 연구에서는 콘크리트 박스거더교의 상부 아스팔트 포장 두께에 따른 겨울철 최저 유효온도 조정값과 유효온도를 연구한다. 이를 위하여 0mm, 50mm, 150mm의 아스팔트 두께를 갖는 3개의 콘크리트 박스거더 시험체를 제작하고, 겨울철 기간동안 온도 데이터를 측정하고 유효온도를 분석한다. 각 모형에 17개와 23개의 온도센서를 부착하여, 하루에 48세트씩 3개월간 3604 온도 데이터를 세트를 측정하고, 이를 바탕으로 겨울철 최저 유효온도를 산정한다. 대기온도 -15℃의 유효온도는 0mm, 50mm, 150mm에서 각각 -9.9℃, -9.2℃, -6.8℃로 분석된다. 최하위 온도(-15∼-13℃)에서 각 모형은 Euro code보다 0.3℃∼+1.7℃ 높게 산정되고, 전체적으로 Euro code와 매우 유사한 값을 보인다. 분석결과 아스팔트 두께에 따른 최저 유효온도의 조정값은 0mm를 기준으로 했을 때, 50mm 150mm 대하여 각각 +0.5℃, +2.7℃로 도출된다. 가장 많이 설계되는 50mm 모형에서 콘크리트교 유효온도는 강교에 비하여 증가가 별로 없음을 볼 수 있다. 본 연구에서 산정된 최저 유효온도로 판단할 때, 콘크리트교 보통기후 지역에서 현 도로교 설계기준의 최저 설계온도는 –5℃에서 –9.2℃이하로 재 검토되어야 할 필요성이 있는 것으로 판단된다.

매크로요소를 이용한 프리스트레스트 콘크리트 박스거더 교량의 비선형 해석

오병환,이명규,Oh, Byung-Hwan,Lee, Myung-Kue 한국콘크리트학회 1999 콘크리트학회지 Vol.11 No.1

일반적으로 프리스트레스트 콘크리트 박스거더교량의 설계에서는 단순화된 단면에 대하여 탄성이론에 근거하여 설계를 수행하고 있다. 이러한 단순화에 따른 제약조건을 개선하기 위해서 본 연구에서는 변단면의 프리스트레스트 콘크리트 박스거더교량을 해석하기 위한 매크로요소를 사용하였다. 해석프로그램에서 재료 비선형모델을 사용하여 극한하중 해석이 가능하도록 하였다. 또한, 교량의 장기거동을 예측하기 위해서 재료의 시간의존적 해석모델을 프로그램에 적용하여 교량의 장기 거동해석을 수행할 수 있게 하였다. 따라서, 재료비선형 모델과 시간의존 해석을 포함하는 비선형 매크로요소는 임의의 형상을 가진 프리스트레스트 박스거더 교량의 실제적인 거동해석에 유용하게 사용할 수 있을 것으로 사료된다. The conventional design of prestressed concrete box girder bridges has been based on the linear elastic analyses using simplified geometric models. To overcome the restriction involved in the simplifications, a macro element for the rational analysis of prestressed concrete box girder bridges with variable cross sections is incorporated in the present analysis. Through the adoption of nonlinear material models, the behaviour of prestressed box bridges up to ultimate loading stage can be examined. The time dependent material models included in the present macro element code enable to predict the long term behaviour of prestressed concrete box girder bridges. The proposed macro element code with the nonlinear material models and time dependent routines can be efficiently used for the realistic analysis of prestressed concrete box girder bridges with arbitrary shapes.

콘크리트 박스거더 교량의 발파해체를 위한 교량모형 해체실험

양형식(Hyung-Sik Yang),장형두(Hyong-Doo Jang),고영훈(Young-Hun Ko) 한국암반공학회 2011 터널과지하공간 Vol.21 No.2

콘크리트 블록에 대한 붙이기 발파실험과 더불어 콘크리트 박스거더 교량의 모형에 대하여 발파해체실험을 실시하였다. 장약으로는 폭발위력의 기준 약으로 사용되는 TNT를 사용하였다. 실험결과 콘크리트 박스거더 교량의 경우 폭약설치지점의 폭발력뿐 만 아니라 박스거더 내부 벽에 작용하는 폭풍압도 해체에 영향을 미치는 것으로 나타났다. Along with series of concrete block experiments, a demolition experiment was conducted for a scaled concrete box girder bridge to investigate collapse and blast behavior. Tri nitro toluene (TNT), the standard explosive for strength was adopted as concussion charge. The result show that demolition was caused by not only direct detonation pressures at charging spots but also blast pressures at inner wall of concrete box girder.

풀스팬 프리캐스트 세그먼트 교량의 해석 및 장기거동 해석

오병환(Oh Byung-Hwan),채성태(Chae Seong-Tae),정상화(Jung Sang-Hwa),박지언(Park Ji-Eon) 한국철도학회 1999 한국철도학회 학술발표대회논문집 Vol.- No.-

The newly proposed Precast Segmental Method (PSM), which makes use of precast elements for election, is relatively new, efficient and fast method for the construction of prestressed box girder bridges. A precast segment of 25 m long pretensioned in the fabrication yard is transported by a special trailer and a launching truss to its final position. The segments are then connected in the site by post-tensioning to make a continuous prestressed concrete box girder bridges. The purpose of this paper is to analyze and evaluate the design of precast prestressed concrete box girder bridges. The detailed analyses including time-dependent behavior of PSM bridges are conducted. The major results and findings, which have been obtained from finite element analysis of PSM bridge, are discussed in this paper and these results will be a good base for the design and analysis of a new precast bridges.

콘크리트 바닥판의 아스팔트 두께에 따른 강박스거더교의최고 설계 유효 온도 산정

이성행,신효경,김경남 한국강구조학회 2018 韓國鋼構造學會 論文集 Vol.30 No.5

The purpose of this study was to measure the temperature change according to the asphalt thickness of the steel box girder bridge deck and to prepare the design criteria accordingly. For this purpose, four steel box girder model specimens with asphalt thickness of 0mm, 50mm, 100m, and 150mm were produced. In each model, 17 to 23 temperature sensors were attached to upper concrete and steel box girders. The temperature was measured for two years and the effective temperature was calculated based on the measured data. The analysis showed that the effective temperature was between 4.3 and 7.1 percent higher than the Euro code at the highest temperature of 38°C. Temperature adjustment of the highest effective temperature according to asphalt thickness is given +2.6°C at 50mm and +0.8°C at 100mm. This value shows a slightly higher value from 0.8°C to 1°C compared to Euro code. The adjustment values for the effective temperature given in this study are considered to be a very useful basis for determining the design temperature load. 본 연구에서는 강박스거더교 바닥판의 아스팔트 두께에 따른 온도변화를 측정하고, 이에 따른 설계기준을 마련하고자 하였다. 이를위해 0mm, 50mm, 100m, 150mm의 아스팔트 두께를 갖는 4개의 강박스거더 모형시험체를 제작하였다. 각 모형에 17∼23개의 온도 센서를상부 콘크리트와 강박스거더에 부착하였다. 2년간 온도측정을 수행하고 측정데이터를 바탕으로 유효온도를 산정하였다. 분석결과 유효온도는 최고온도 38℃에서 Euro code와 비교하여 4.3∼ 7.1% 높게 산정되었다. 아스팔트 두께에 따른 최고 유효온도의 온도 조정값은 아스팔트 두께50mm에서 +2.6℃, 100mm에서는 +0.8℃가 제시된다. 이 값은 Euro code와 비교하여 0.8℃∼1℃의 약간 높은 값을 보인다. 이를 적용하면, 본 연구에서 제시된 유효온도의 조정값은 설계온도 하중 산정 시 매우 유용한 기초자료가 될 것으로 판단된다.

Vibration analysis of prestressed concrete bridge subjected to moving vehicles

Huang, M.,Liu, J.K.,Law, S.S.,Lu, Z.R. Techno-Press 2011 Interaction and multiscale mechanics Vol.4 No.4

The vibration response of the bridges under the moving vehicular load is of importance for engineers to estimate the serviceability of existing bridges and to design new bridges. This paper deals with the three dimensional vibration analysis of prestressed concrete bridges under moving vehicles. The prestressed bridges are modeled by four-node isoparametric flat shell elements with the transverse shearing deformation taken into account. The usual five degrees-of-freedom (DOFs) per node of the element are appended with a drilling DOF to accommodate the transformation of the local stiffness and mass matrices to the global coordinates. The vehicle is modeled as a single or two-DOF system. A single-span prestressed Tee beam and two-span prestressed box-girder bridge are studied as the two numerical examples. The effects of prestress forces on the natural frequencies and dynamic responses of the bridges are investigated.

FBG센서를 이용한 콘크리트 충진 FRP 스트럿 보강 PSC 교량의 스트럿 거동 분석

정원석,강동훈,안주옥,Chung. Won-Seok,Kang. Dong-Hoon,An. Zu-Og 한국방재학회 2009 한국방재학회논문집 Vol.9 No.6

최근 국내에서는 PSC(Prestressed Concrete) 박스 거더 교량의 교폭을 늘리고 자중을 줄이기 위한 목적으로 박스의 수를 줄이는 대신 콘크리트 충진 FRP(Concrete Filled FRP, CFFRP) 스트럿을 상판 캔틸레버 부분에 설치하는 공법이 시공되고 있다. 이러한 CFFRP 스트럿은 사례가 많지 않은 교량 구조물로서 설계 및 시공에서의 불확실성을 제거하기 위해 교량 시스템에서의 스트럿 거동을 실험적으로 분석할 필요가 있다. 따라서 본 연구에서는 대상교량에 대해 현장시험을 실시하여 CFFRP 스트럿의 국부 거동을 분석하고자 한다. 특히 전자기파 간섭에 대해 면역이 우수한 광센서인 FBG(fiber Bragg grating) 센서를 기반으로 시험을 실시하여 잡음이 없는 우수한 응답을 성공적으로 획득하였다. 현장시험에서는 재하트럭의 속도와 횡방향 위치를 매개변수로 시험을 실시하였다. 그 결과 CFFRP 스트럿은 하중재하 위치와 속도에 관계없이 압축상태에 존재하고 있으며, 통과 차량의 횡방향 위치가 CFFRP 스트럿의 거동에 민감한 요소임을 확인하였다. Recently, a new PSC (Prestressed Concrete) bridge system, which is supported by Concrete-filled fiber-reinforced polymer (CFFRP) strut, has been introduced. This bridge is able to reduce self-weight and increase the width of traditional PSC bridges. However, no relevant research has been reported on local behavior of CFFRP strut in the bridge system. The purpose of this study is to investigate local behavior of CFFRP struts using fiber Bragg grating (FBG) sensors. Field tests were performed to examine the hoop strains and longitudinal strains of the FRP strut under various lateral positions and velocities of a test truck. It has been observed that CFFRP strut is under compression regardless of vehicle speed and location. However, the CFFRP strut is sensitive to the lateral position of vehicles in terms of strain magnitude. Results also indicated that the FBG sensors can faithfully record the hoop and longitudinal strains of the FRP strut without electro-magnetic interference.

Cost optimization of segmental precast concrete bridges superstructure using genetic algorithm

R. Ghiamat,M. Madhkhan,T. Bakhshpoori 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.4

The construction of segmental precast concrete bridge is an increase due to its superior performance and economic advantages. This type of bridge is appropriate for spans within 30 to 150 m (100 to 500 ft), known as mega-projects and the design optimization would lead to considerable economic benefits. A box-girder cross section superstructure of balanced cantilever construction method is assessed here. The depth of cross section, (variable along the span linearly), bottom flange thickness, and the count of strands are considered as design variables. The optimum design is characterized by geometry, serviceability, ductility, and ultimate limit states specified by AASHTO. Genetic algorithm (GA) is applied in two fronts: as to the saving in construction cost 8% and as to concrete volume 6%. The sensitivity analysis is run by considering different parameters like span/depth ratio, relation between superstructure cost, span length and concrete compressive strength.

비내진 상세를 갖는 철근콘크리트 교량의 응답에 대한 수직방향 지진파의 영향

전종수 한국복합신소재구조학회 2016 복합신소재구조학회논문집 Vol.7 No.4

This research describes the impact of vertical earthquake components on the performance of typical non-ductile bridges. To achieve this goal, this research chooses a non-seismically designed reinforced concrete bridge typically found in the California area. Particularly, their columns with inadequate design have a higher possibility of shear failure. To consider this failure, the column model reflects shear-axial interaction effect and is verified by comparing simulated results and experimental data available in literature. Two computational bridge models having column shear model subjected to constant and varying axial load are then built to conduct inelastic dynamic analyses. The responses are employed to construct probabilistic seismic demand models for two bridge models. This results indicate that the consideration of shear-axial interaction effect increases the seismic demand of all bridge components in non-ductile bridges, resulting in their increased seismic vulnerability.