• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1001-1006
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• 2000

These should be constructed partially, because many prestressed concrete box girder bridges in situ have large cross section and long span. Therefore, accurate prediction of differences, both elapse time of each construction stage and exposure of atmosphere at each position of cross section, is very important. Though it is importance, engineers are apt to overlook it. This study predicted cracks due to shrinkage and stress concentration phenomenon by each construction stage and then, ascertained reduction of tensile stresses after applying retrofit scheme.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.538-541
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• 2006

PSC(Prestressed Concrete) box girder bridges have been widely applied in Korea. A number of these bridges have been built by the segmental construction method in the longitudinal direction and(or) vertically along the cross-sectional depth with MSS(Moving Scaffolding System). An actual 2-span continuous PSC box girder bridge of Kyeongbu high speed railway was selected and instrumented with 96 vibrating wire embedded type strain gauges and 2 thermocouples. The long-term behavior of the bridge was monitored through two major points located at mid-span of the first span and at the internal support. Data collection started just after the casting of the first segment (U section). Concrete strain and temperature data were gathered regularly by a data logger (CR10) during 600 days under and after construction. According to this measurement, the parabolic longitudinal strain distribution in the top slab at mid-span is shown. And also, the same distribution at the interior support is shown. The compressive strains at the cantilever region are larger than at the web position and the internal part in the top slab. Strain difference largely happened during the early construction period.

• Journal of the Korean Society of Safety
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• 제21권4호
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• pp.95-101
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• 2006

It is well known that the thermal load in PSC(prestressed concrete) box-girder bridge is the principal cause of detrimental crack. The longitudinal stress caused by the lateral stress from the temperature gradient in slab of PSC box-girder bridge has a considerable influence on the durability and economy of bridge structures. As the basic study for the rational consideration of thermal load and the derivation of design guide, the inverse thermal analysis program for PSC box-girder bridges using field measurement data is developed. In this paper, thermal analyses are performed using field monitoring data for the sample PSC box-girder bridge. It is proposed that the link between monitoring program and the inverse analysis program is available.

• Journal of the Korea Concrete Institute
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• 제18권4호
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• pp.507-515
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• 2006

The purpose of the paper is to propose a method to give a more accurate prediction of prestress changes in prestressed concrete(PSC) bridges. The statistical approach of the method is using the measurement data of the structural system to develop a nonlinear regression analysis. Long-term prediction of prestress is achieved using nonlinear regression analysis. The proposed method is applied to the prediction of prestress of an actual prestressed concrete box girder bridge. The present study represents that confidence interval of long-term prediction becomes progressively narrower with the increase of in-situ measurement data. Therefore, the numerical results prove that a more realistic long-term prediction of prestress changes in PSC structures can be achieved by employing the proposed method. The prediction results can be efficiently used to evaluate prestress during the service life of structure so that the remaining prestress exceeds the control criteria.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 한국전산구조공학회 1991년도 봄 학술발표회 논문집
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• pp.56-60
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• 1991

Free Cantilever Method(FCM) is one of the most effective construction methods when precast prestressed concrete box girders are erected in the construction site. The special feature of FCM is that precast segments are erected in cantilever on the pier and connected in the middle of span to form the complete superstructure. Therefore each structural subsystem will be shown in each construction step and it should be analyzed for design whenever the segment is erected. In this study, the computer program was developed to optimally design the P.C box girder bridge considering tile construction sequence and verified by comparing the calculated results with the data of existing P.C box girder bridges. the sensitivity analysis was performed to show the efficiency of the developed program.

• Computers and Concrete
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• 제28권5호
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• pp.487-495
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• 2021

The use of prestressed concrete box girder bridges built by segmentally balanced cantilevers has bloomed in the last decades due to its significant structural and construction advantages in complex topographies. In Colombia, this typology is the most common solution for structures with spans ranging of 80-200 m. Despite its popularity, excessive deflections in bridges worldwide evidenced that time-dependent effects were underestimated. This problem has led to the constant updating of the creep and shrinkage models in international code standards. Differences observed between design processes of box girder bridges of the Colombian code and Eurocode, led to the need for a validation of in-service status of these structures. This study analyzes the long-term behavior of the Tablazo bridge with data scarcity. The measured leveling of this structure is compared with a finite-element model that consider the most widely used creep and shrinkage models in the literature. Finally, an adjusted model evidence excessive deflection on the bridge after six years. Monitoring of this bridge typology in Colombia and updating of the current design code is recommended.

• Journal of the Korea Concrete Institute
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• 제19권4호
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• pp.433-439
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• 2007

The main objective of the paper is to investigate the static behavior of a prestressed concrete (PSC) girder that has been spliced with precast box segments. A 20 m long full-scale spliced PSC girder is fabricated and tested to compare its static performance against a monolithic girder. The monolithic girder has the same geometric and material properties with respect to the spliced girder. This includes infernal strain, deflections, neutral axis position, and crack patterns for both girders. The test also consists of monitoring relative displacements occurring across the joints. Both the horizontal displacement (gap) and vertical displacement (sliding) are measured throughout the loading procedure. All results have been compared to those obtained from the monolithic girder. It has been demonstrated that the spliced girder offers close behavior with respect to the monolithic girder up to the crack load. Both girders exhibits ductile flexural failure rather than abrupt shear failure at joints.

• Magazine of the Korea Concrete Institute
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• 제10권6호
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• pp.149-159
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• 1998

The reasonable prediction of time-dependent deformation of prestressed concrete(PSC) box girder bridges is very important for accurate construction as well as good serviceability. The long-term behavior is mostly influenced by the probabilistic characteristic of creep and shrinkage. This paper presents a method of statistical analysis and sensitivity analysis of creep and shrinkage effects in PSC box been taken into account - model uncertainty, parameter variation and environmental condition. The statistical and sensitivity analyses are performed by using the numerical simulation of Latin Hypercube sampling. For each sample, the time-dependent structural analysis is performed to produce response data, which are then statistically analyzed. The probabilistic prediction of the confidence limits on long-term effects of creep and shrinkage is then expressed. Three measure are examined to quantify the sensitivity of the outputs of each of the input variables. These are rank correlation coefficient(RCC), partical rank correlation coefficient(PRCC) and standardiozed rank regression coefficient(SRRC) computed on the ranks of the observations. Three creep and shrinkage models - i. e., ACI model. CEB-FIP model and the model in Korea Highway Bridge Specification - are studied. The creep model uncertainy factor and the relative humidity appear to be the most dominant factors with regard to the model output uncertainty.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.415-420
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• 1998

In this paper, 2D SUB-3D STM approach for analysis and design of 3D structural concrete is presented. In the approach several 2D sub strut-tie models which are representations of compressive and tensile stress flows of each projected plane of 3D structural concrete are utilized in the sketch of a 3D strut-tie model, in the evaluation of effective strengths of compressive concrete struts, and in the verification of geometric compatibility and bearing capacity of critical nodal zones of 3D strut-tie model. To prove the validity and rationality of the suggested approach, the behavior and strength of a prestressed box girder diaphragm tested to failure are evaluated.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.979-984
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• 2001

The Sang-Jin bridge constructed by the Free Cantilever Method in 1985 is 4-span concrete rahmen bridge with a hinge at midspan. Due to the effect of creep, shrinkage of concrete and relaxation of tendon, the Sang-Jin bridge exposed the excessive displacement at midspan with the passage of time. In order to improve the load-carrying-capacity and durability of the bridge, needs to repair and rehabilitate the structure emerged. New rehabilitation methods were applied such as external prestressing of concrete box, application of pier pre-camber and steel truss jacking. Structural analysis and several tests including static load test, dynamic load test and ambient vibration test were executed to verify the improvement. The test result showed that the displacement of the midspan was improved by 10mm and it was verified that the stiffness of the bridge was increased. Totally, the load-carrying-capacity of Sang-Jin bridge was increased at least 1.56times which was attributed to the new rehabilitation method.