• Structural Engineering and Mechanics
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• 제80권6호
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• pp.749-765
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• 2021

Suspension bridges bear large eccentric live loads in rush hours when most vehicles travel in one direction on the left or right side of the bridge. With the increasing number and weight of vehicles and the girder widening, the eccentric live load effect on the bridge behavior, including bending and distortion of the main girder, gets more pronounced, even jeopardizing bridge safety. This study proposes an analytical algorithm based on multi-catenary theory for predicting the suspension bridge responses to eccentric live load via the nonlinear generalized reduced gradient method. A set of governing equations is derived to solve the following unknown values: the girder rigid-body displacement in the longitudinal direction; the horizontal projection lengths of main cable's segments; the parameters of catenary equations and horizontal forces of the side span cable segments and the leftmost segments of middle span cables; the suspender tensions and the bearing reactions. Then girder's responses, including rigid-body displacement in the longitudinal direction, deflections, and torsion angles; suspenders' responses, including the suspender tensions and the hanging point displacements; main cables' responses, including the horizontal forces of each segment; and the longitudinal displacement of the pylons' tower top under eccentric load can be calculated. The response of an exemplar suspension bridge with three spans of 168, 548, and 168 m is calculated by the proposed analytical method and the finite element method in two eccentric live load cases, and their results prove the former's feasibility. The nonuniform distribution of the live load in the lateral direction is shown to impose a greater threat to suspension bridge safety than that in the longitudinal direction, while some other specific features revealed by the proposed method are discussed in detail.

• Structural Engineering and Mechanics
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• 제75권4호
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• pp.507-518
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• 2020

With the rapid development of rail transit, rail transit noise needs to be paid more and more attention. In order to accurately and effectively analyze the characteristics of low-frequency noise, a prediction model of vibration of box girder was established based on the hybrid FE-SEA method. When the train speed is 140 km/h, 200 km/h and 250 km/h, the vibration and noise of the box girder induced by the vertical wheel-rail interaction in the frequency range of 20-500 Hz are analyzed. Detailed analysis of the energy level, sound pressure contribution, modal analysis and vibration loss power of each slab at the operating speed of 140 km /h. The results show that: (1) When the train runs at a speed of 140km/h, the roof contributes more to the sound pressure at the far sound field point. Analyzing the frequency range from 20 to 500 Hz: The top plate plays a very important role in controlling sound pressure, contributing up to 70% of the sound pressure at peak frequencies. (2) When the train is traveling at various speeds, the maximum amplitude of structural vibration and noise generated by the viaduct occurs at 50 Hz. The vibration acceleration of the box beam at the far field point and near field point is mainly concentrated in the frequency range of 31.5-100 Hz, which is consistent with the dominant frequency band of wheel-rail force. Therefore, the main frequency of reducing the vibration and noise of the box beam is 31.5-100 Hz. (3) The vibration energy level and sound pressure level of the box bridge at different speeds are basically the same. The laws of vibration energy and sound pressure follow the rules below: web

• 한국산학기술학회논문지
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• 제20권3호
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• pp.602-608
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• 2019

본 연구에서는 강박스거더교 바닥판의 아스팔트 두께에 따른 단면 상하 온도차를 산정하고, 이에 따른 설계기준의 자료를 제공하고자 하였다. 아스팔트 두께 0mm, 50mm, 100m, 150mm의 4개 강박스거더 모형시험체를 제작하였다. 각 모형에 17~23개의 온도 센서를 상부 콘크리트와 강박스거더에 부착하였다. 이 센서 중 Euro code와 온도차를 비교 할 수 있는 6개의 온도 게이지를 선정하였다. 각 모형의 기준 대기온도에서 최대 온도와 최저 온도를 계산하고, 이를 바탕으로 온도차(경사)를 산정하여, 4개 각 모형에서 온도차 모델을 제시하였다. 0mm ~ 100mm 온도차 모델은 슬래브 최상단에서 Euro code의 온도차와 비교할 때 -0.9~-1.5도 더 낮은 온도차를 보였다. 전체적으로 측정된 온도차는 Euro code와 비교하여 5.45%~8.33%정도의 오차가 있음을 확인하였다. 산정된 온도와 평균온도의 차를 표준오차의 배수로 산정한 표준오차 계수는 최상단과 최하 단에서 평균 2.50 ~ 2.51배의 값으로 일정한 범위에서 산정되었다. 제시된 온도차 모델은 국내 교량 온도설계 온도차 기준 산정 시 기본 자료로 활용될 수 있을 것으로 판단된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.3142-3146
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• 2011

This paper introduces improved prestressed concrete (PSC) girders for the railway bridges. In order to improve performance of conventional PSC girders, various types of PSC girders are either under development or have already been applied in railway bridges. Incrementally prestressed concrete girder is one of these newly developed girders. According to the design concept, these types of PSC girders have the advantages of requiring less self-weight while having the capability of longer spans. However, the tensional failure of top flange is one of the critical issues at the first prestressing stage. To effectively provide initial section stiffness of PSC girders, concrete block on the top flange is used in this study. The efficiency of the proposed structures, compared with conventional girders and improved ones, is successfully demonstrated in the example.

• 한국농공학회지
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• 제29권3호
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• pp.145-152
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• 1987

This paper suggests a method for the analysis of box girders which are subject to the membrane and the plate bending actions, Moreover, the method is applied to the box girders under distributed loads which have various geometrical types of cross sections and are made out of different materials. The approach is based on the finite element technique in which the structure is considered to be a spatial assemblage of flat plate elements and the deformations of the plates are to be approximated with 9-noded parabolic isoparametric elements. The results are summarized as follows. 1.In all models, the larger the widths of top flange inside of web are, the larger the vertical deflections are. 2.The maximum transverse and longitudinal moments in the composite box girders are judged to be larger than those in the RC box girders. 3.The transverse and the longitudinal moments in top flange of composite box. girders are larger than those in that of the RC box girders. 4.The transverse and longitudinal moments in web and bottom flange of the composite box girders are estimated to be very small in compare to those in web and bottom flange of the RC box girders.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 춘계학술논문 발표대회
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• pp.29-31
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• 2007

Building construction in downtown is ever increasing with a strong demand. Top-Down Method is one of suitable construction method for its advantage in minimizing disturbance to neighborhood. Along with these reasons construction site has developed lots of new methods and materials for Time-Cost Trade-off and improving constructability. Opened Slab is one of these method which resist the horizontal force by slab and it has many merit about construction time and unity. We analyze the compression tests on opened slab for the application.

• 콘크리트학회논문집
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• 제26권6호
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• pp.761-769
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• 2014

인장강도 및 휨강도가 낮고 취성파괴의 특성을 가지는 일반적인 콘크리트의 단점을 극복하기 위하여 최근에는 압축강도가 180 MPa이상인 고성능 콘크리트에 강섬유를 혼입한 강섬유 보강 초고성능 콘크리트(UHPC)에 대한 연구가 활발히 진행되고 있다. UHPC 바닥판과 강재 거더를 이용하여 합성보를 구성할 때, UHPC 바닥판의 높은 강도와 강성으로 인하여 강재거더 상부 플랜지의 역할이 거의 불필요할 것으로 예상된다. 이러한 점을 착안하여 본 논문에서는 합성보 구성 시에 강재 거더의 상부플랜지를 없앤 역T형 거더를 적용하였다. 역T형 거더에 UHPC바닥판을 합성하여 합성보를 구성할 경우, 상부플랜지가 없는 이유로 전단연결재의 설치 위치가 상부플랜지 대신에 강재 거더 복부에 설치해야하는 문제점이 발생되며, 강재 복부에 설치되는 전단연결재에 대한 거동, 역T형 강거더 합성보의 휨거동 특성 등은 현재까지 실험 및 이론적으로 평가된 적이 거의 없는 실정인 이유로 이에 대한 연구가 절실하다. 이를 위하여 본 논문에서는 전단연결재 간격, 바닥판 두께 등을 변수로 하여 역T형 거더와 UHPC바닥판을 합성한 합성보를 8개 제작하여 전단연결재의 거동, 휨거동 특성 등을 파악하고자 하였다. 실험결과를 기준으로 볼 때, 향후 UHPC의 경우 스터의 간격은 100 mm에서 바닥판 두께의 2~3 배 사이로 규정함이 적절할 것으로 예상된다. 또한 실험 부재의 특성 상대변위는 Eurocode-4의 연성거동 기준에 의하면 충분한 연성 거동을 하는 것으로 판정되었으며, 바닥판이 지나치게 얇고 전단연결재의 간격이 지나치게 넓은 경우를 제외한 대부분의 부재들은 일반 콘크리트보다 UHPC의 성능이 우수하여 기존의 AASHTO LRFD 및 Eurocode-4의 식과 실험결과간의 차이가 있음을 알 수 있다.

• Structural Engineering and Mechanics
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• 제65권2호
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• pp.141-154
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• 2018

In this study, the bend-buckling strength of the web in longitudinally stiffened plate girder was numerically investigated. The buckling strength of the reinforced web was evaluated through an eigenvalue analysis of the hypothetical model, in which the top and bottom junctions of the web to the flanges were assumed as simple support conditions. Major parameters in the analysis include asymmetrical cross-sectional property, aspect ratio of the web, stiffener locations, and bending rigidity of the stiffeners. The numerical results showed that current AASHTO LRFD specifications (2014) provides the buckling strength from considerably safe side to slightly unsafe side depending on the location of the stiffeners. A modified equation for buckling coefficients was proposed to solve the shortcomings. The bending rigidity requirements of longitudinal stiffeners stipulated in AASHTO were also investigated. It is desirable to increase the rigidity of the stiffeners when the aspect ratio is less than 1.0.

• Structural Engineering and Mechanics
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• 제83권1호
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• pp.123-134
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• 2022

The stability of cable-stayed bridges is an important factor considered during design. In recent years, the novel spatial diamond-shaped bridge pylon has shown its advantages in various aspects, including the static response and the stability performance with the development of cable-stayed bridge towards long-span and heavy-load. Based on the energy approach, this paper presents a practical calculation method of the completed state stability of a cable-stayed bridge with two spatial diamond-shaped pylons. In the analysis, the possible transverse buckling of the girder, the top pylon column, and the mid pylon columns are considered simultaneously. The total potential energy of the spatial diamond-shaped pylon cable-stayed bridge is calculated. And based on the principle of stationary potential energy, the transverse buckling coefficients and corresponding buckling modes are obtained. Furthermore, an example is calculated using the design parameters of the Changtai Yangtze River Bridge, a 1176 m cable-stayed bridge under construction in China, to verify the effectiveness and accuracy of the proposed method in practical engineering. The critical loads and the buckling modes derived by the proposed method are in good agreement with the results of the finite element method. Finally, cable-stayed bridges varying pylon and girder stiffness ratios and pylon geometric dimensions are calculated to discuss the applicability and advantages of the proposed method. And a further discussion on the degrees of the polynomial functions when assuming buckling modes are presented.

• Steel and Composite Structures
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• 제43권2호
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• pp.165-183
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• 2022

Most transportation departments have recognized and developed procedures to address the ever-increasing weights of trucks traveling on bridges in a service today. Transportation agencies also recognize the issues with overheight vehicles' collisions with bridges, but few stakeholders have definitive countermeasures. Bridges are becoming more vulnerable to collisions from overheight vehicles. The exact response under lateral impact force is difficult to predict. In this paper, nonlinear impact analysis shows that the degree of deformation recorded through the modeling of the unprotected vehicle-girder model provides realistic results compared to the observation from the US-61 bridge overheight vehicle impact. The predicted displacements are 0.229 m, 0.161 m, and 0.271 m in the girder bottom flange (lateral), bottom flange (vertical), and web (lateral) deformations, respectively, due to a truck traveling at 112.65 km/h. With such large deformations, the integrity of an impacted bridge becomes jeopardized, which in most cases requires closing the bridge for safety reasons and a need for rehabilitation. We proposed different sacrificial cushion systems to dissipate the energy of an overheight vehicle impact. The goal was to design and tune a suitable energy absorbing system that can protect the bridge and possibly reduce stresses in the overheight vehicle, minimizing the consequences of an impact. A material representing a Sorbothane high impact rubber was chosen and modeled in ANSYS. Out of three sacrificial schemes, a sandwich system is the best in protecting both the bridge and the overheight vehicle. The mitigation system reduced the lateral deflection in the bottom flange by 89%. The system decreased the stresses in the bridge girder and the top portion of the vehicle by 82% and 25%, respectively. The results reveal the capability of the proposed sacrificial system as an effective mitigation system.