• Smart Structures and Systems
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• 제9권6호
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• pp.489-504
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• 2012

For the safety of prestressed structures such as cable-stayed bridges and prestressed concrete bridges, it is very important to ensure the prestress force of cable or tendon. The loss of prestress force could significantly reduce load carrying capacity of the structure and even result in structural collapse. The objective of this study is to present a smart PZT-interface for wireless impedance-based prestress-loss monitoring in tendon-anchorage connection. Firstly, a smart PZT-interface is newly designed for sensitively monitoring of electro-mechanical impedance changes in tendon-anchorage subsystem. To analyze the effect of prestress force, an analytical model of tendon-anchorage is described regarding to the relationship between prestress force and structural parameters of the anchorage contact region. Based on the analytical model, an impedance-based method for monitoring of prestress-loss is conducted using the impedance-sensitive PZT-interface. Secondly, wireless impedance sensor node working on Imote2 platforms, which is interacted with the smart PZT-interface, is outlined. Finally, experiment on a lab-scale tendon-anchorage of a prestressed concrete girder is conducted to evaluate the performance of the smart PZT-interface along with the wireless impedance sensor node on prestress-loss detection. Frequency shift and cross correlation deviation of impedance signature are utilized to estimate impedance variation due to prestress-loss.

• Earthquakes and Structures
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• 제15권5호
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• pp.499-511
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• 2018

This paper aims to investigate the seismic performance of the prestressed steel strips retrofitted RC beam-column joints. Two series of joint specimens were conducted under compression load and reversed cyclic loading through quasi-static tests. Based on the test results, the seismic behavior of the strengthened joints specimens in terms of the failure modes, hysteresis response, bearing capacity, ductility, stiffness degradation, energy dissipation performance and damage level were focused. Moreover, the effects of the amount of the prestressed steel strips and the axial compression ratio on seismic performance of retrofitted specimens were analyzed. It was shown that the prestressed steel strips retrofitting method could significantly improve the seismic behavior of the RC joint because of the large confinement provided by prestressed steel strips in beam-column joints. The decrease of the spacing and the increase of the layer number of the prestressed steel strips could result in a better seismic performance of the retrofitted joint specimens. Moreover, increasing the axial compression ration could enhance the peak load, stiffness and the energy performance of the joint specimens. Furthermore, by comparison with the specimens reinforced with CFRP sheets, the specimens reinforced with prestressed steel strips was slightly better in seismic performance and cost-saving in material and labor. Therefore, this prestressed steel strips retrofitting method is quite helpful to enhance the seismic behavior of the RC beam-column joints with reducing the cost and engineering time.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 가을 학술발표회 논문집
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• pp.87-94
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• 1994

During the construction of externally prestressed 7-span continuous segmental bridge, cracks beyond permissible limit were found at anchor zone of expansion joint segment. To eliminate this problem, tension side of diaphragm was prestressed by post-tensioning bars in vertical and horizontal direction. To investigate this remedy is acceptable, stresses of reinforcing bars and concrete surface were measured for the real structure in the field. The measurement was performed through each step of prestressing sequence during construction. Also to investigage stresses induced by live load, static load test was performed and the results was analyzed. In this paper it will be presented the procedure and results for this experimental study along with comparison with analytical study.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.18-25
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• 2001

Analysis of prestressed box-girder bridges using the spline finite strip method is presented. In the present study, the spline finite strip method(FSM) is modified using the non-periodic B-spline interpolation. In the analysis of the prestressed box girder bridges, each tendon force is evaluated by summation of the adjacent segment forces. Once the equivalent forces acting on the structure at the tendon points are found, they are transformed into statically equivalent forces at the adjacent node or joints. Several examples were analyzed to verify the performance of present method using the non-periodic B-spline FSM. Good agreements were obtained when compared with the previous study.

• 한국구조물진단유지관리공학회 논문집
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• 제13권4호통권56호
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• pp.126-136
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• 2009

분사식 FRP 보강 공법은 섬유(Fiber)와 수지(Resin)를 외부에서 혼합하여 요철이 많은 콘크리트 표면에 고속의 압축 공기로 랜덤하게 분사하여 기존 콘크리트 구조물을 보강하는 공법이다. 새로운 분사식 FRP 공법을 이용하여 구조물의 보강 성능을 평가하였다. 콘크리트 보 실험체에 대한 휨강도 실험을 수행하여 분사식 FRP의 최적물성치를 찾고 이 결과를 이용하여 PSC I형 거더 표준단면을 1/5로 축소한 구조물에 적용하여 실험을 하였다. 손상된 프리스트레스트 콘크리트에 적용한 결과 무보강보에 비하여 휨강도가 49.8% 증가하였고 사용상태의 거동이 개선되었으며, 보강에 의해 처짐 및 균열 제어에 효과적이었다. 결론적으로 분사식 FRP 공법의 보강 적용은 구조물의 성능 향상에 효과적이라고 할 수 있다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.457-462
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• 2002

Generally speaking, durability, load carrying capacity and the life of structure becomes to be shortened in all structures as time passed. Also, we have to repair and reinforce because of tile decrease of the traffic volume and overloaded vehicles in the bridge. External prestressing method is most popular and effective strengthening method which can be used for the prestressed concrete-girders. When strengthening with external prestressing method, there are many ways to install anchorage system. But, These methods have many faults. For example, the achorage force is so small or an anchorage system installation damages an existing structure. So, this paper suggested a new anchorage system to strengthen without any damage to the structure and then confirm the increase of durability and the properties of behavior with experimentation.

• 콘크리트학회논문집
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• 제11권3호
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• pp.23-34
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• 1999

In designing PSC box girder bridge, the dead load, prestressing force, creep and shrinkage of concrete are the main factors which influence the camber and deflection of segmental concrete structure under construction. Among these factors the creep and shrinkage are the functions of the time-dependent property which, therefore, must considered with time. The prediction model for estimating creep and shrinkage of concrete has been suggested by ACI, CEB/FIP, JSCE and KSCE design code. In this study the creep and shrinkage test were carried out for four curing ages of concrete which was applied to the pretressed concrete box-girder bridge at a construction site, and the results of test were compared to the values of prediction by the design code. Shrinkage test shows that the test results are similar to KSCE-96 and JSCE-96 but very higher than other prediction model and creep test results are generally similar to ACI-209 and DSCE-96 but lower than other prediction models in contrast to shrinkage test.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.473-479
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• 1996

Until now, we assumed in the time-dependent analysis of concrete structure that tensile creep has same characteristics as compressive creep has. But, in according to results of researches, it appears that tensile creep is different from compressive creep in quantity and in mechanics because tensile creep is affected significantly by micro cracking. The test results indicate that the creep behavior of concrete in compression and tension is rather different. The test data shows that the amount of creep under tensile loading is larger than that under compressive loading. In this paper, a realistic tensile creep model is suggested and incorporated in the formulation. In order to get more accurate results of time-dependent analysis. The present study indicates that the long-term deflection of concrete structures under realistic tensile creep model is somewhat larger than that under ordinary compressive creep model.

• Structural Engineering and Mechanics
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• 제36권6호
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• pp.729-744
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• 2010

There is world wide concern for safety of nuclear power installations after the terrorist attack on World Trade Center in 2001 and several other civilian structures in the last decade. The nuclear containment structure in many countries is a double shell structure (outer shell a RCC and inner a prestressed concrete). The outer reinforced concrete shell protects the inner shell and is designed for external loading like impact and blast. A comparative study of non-linear response of reinforced concrete nuclear containment cylindrical shell subjected to impact of an aircraft (Phantom) and explosion of different amounts of blast charges have been presented here. A material model which takes into account the strain rate sensitivity in dynamic loading situations, plastic and visco-plastic behavior in three dimensional stress state and cracking in tension has been developed earlier and implemented into a finite element code which has been validated with published literature. The analysis has been made using the developed software. Significant conclusions have been drawn for dissimilarity in response (deflections, stresses, cracks etc.) of the shell for impact and blast loading.

• 콘크리트학회논문집
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• 제23권5호
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• pp.667-674
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• 2011

이 연구는 교량의 생애 동안의 온도 변화와 콘크리트의 시간 의존 영향을 고려하여 PSC 거더 일체식 교량의 해석 방법과 교대의 변위를 예측하는 모델 개발에 관한 것이다. 비선형 수치 해석 모델은 지반-구조물의 상호작용을 고려하며, 재료의 비선형 또한 고려되었다. 개발된 수치 해석 모델을 이용하여 총 243가지의 경우에 대하여 변수 연구를 하였다. 고려된 변수는 (1) 열팽창 계수, (2) 교량 길이, (3) 뒤채움재의 높이, (4) 뒤채움재의 강성, 그리고 (5) 말뚝-지반 강성이다. 변수 연구의 결과는 열팽창 계수, 교량 길이, 말뚝-지반의 강성이 지배적인 영향을 나타내는 것으로 드러났다. 또한, 교량의 길이는 교대의 윗부분의 변위에 지배적인 영향을 미치며 자유팽창 수축과 유사하였다. 하부의 변위에는 다른 변수들의 영향으로 추정이 쉽지 않았다. 개발된 교대의 변위 추정 모델은 기본 설계시에 사용될 수 있을 것이다.