• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.77-87
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• 1999

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.

• Computers and Concrete
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• v.20 no.5
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• pp.617-625
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• 2017

Prestress force identification (PFI) is crucial to maintain the safety of prestressed concrete bridges. A synergic identification method has been proposed recently by the authors that can determine the prestress force (PF) and the excitation force simultaneously in prestressed concrete beams with good accuracy. In this paper, the ability of this method in the application with prestressed concrete box-girder bridges is demonstrated. A reasonable assumption is made to capture the similarity of the dynamic behavior of the prestressed concrete box-girder bridge and a beam under a certain loading scenario, and the feasibility of this method for application in a prestressed box-girder bridge is affirmed. A comprehensive laboratory test program is conducted, and the effects of PF, excitation, measuring time and uncertainties are studied. Results show that the proposed method can predict the PF and the excitation force in a prestressed concrete box-girder accurately and has a great robustness against uncertainties.

• Structural Engineering and Mechanics
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• v.31 no.5
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• pp.605-619
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• 2009

A comparative experimental study of prestressed continuous steel-concrete composite beams was carried out. Two continuous composite beams were tested, one of which was plain continuous steel-concrete composite beam, while the other was a composite beam prestressed with external tendons. Cracking behavior and the load carrying capacity of the beams were investigated experimentally. Full plasticity was developed in the mid-span section each beam, the maximum moments attained at the internal support sections however were governed by local buckling which was related to the slenderness of composite section. It was found that in hogging moment regions, the ultimate resistance of an externally prestressed composite beam would be governed by either distortional lateral buckling or local buckling, or interactive mode of these two buckling patterns. The results show that exerting prestressing on a continuous composite beam with external tendons will increase the extent of internal force and moment redistribution in the beam. The influences of local and distortional buckling on the behaviors of the composite continuous beams are discussed. The Moment redistribution and the load carrying capacity of the prestressed continuous composite beams are evaluated, and it is found that at the ultimate state, the moment redistribution in the prestrssed continuous composite beams is greater than that in non-prestressed composite beams.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.113-119
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• 2002

In the prestressed concrete structures, stresses are gradually redistributed with time due to the creep and shrinkage of concrete and the stress relaxation of prestressed steel. In this study a numerical procedure and computer program is developed to analyze the behavior of prestressed concrete structures considering the time-dependent properties of material. It accounts for the aging, creep and shrinkage of concrete and the stress relaxation of prestressed steel. The structural model uses two dimensional plane frame elements with three nodal degree of freedom and is analyzed based on the finite element method. Member cross section can consist of concrete, reinforcement and prestressing steel. Two different set of equations for the prediction of time-dependent material properties of concrete are presented, which are ACI, CEB-FIP. Analytical studies for different examples of prestressed concrete structures have been performed to demonstrated the capabilities and practical applicabilities of the developed program.

• Journal of Korean Association for Spatial Structures
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• v.17 no.1
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• pp.69-75
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• 2017

In fire design for floors, the three criteria of stability, integrity and insulation are required for the specified fire resistance duration. Among these, stability is not easy to confirm. For solid prestressed concrete slabs of uniform thickness, Eurocode 2 provides tabulated data and specifies an axis distance to the centroid of strands to achieve particular fire resistance ratings, but it is not clear if this data can be used for a wide range of different prestressed slab profiles. In order to verify the current code-fire ratings for precast prestressed slabs, both simple and advanced calculation methods are investigated. This paper examines the use of calculation methods, accounting for the real behaviour of unprotected simply supported prestressed concrete slabs exposed to the standard ISO 834 fire. The calculated fire resistance of each prestressed concrete slab is compared with tabulated data in Eurocode part 1.2, with detailed discussion.

• Earthquakes and Structures
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• v.19 no.6
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• pp.459-469
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• 2020

An external prestressed steel-bar truss unit was developed as a new strengthening technology to enhance the seismic performance of an in-plane masonry wall structure while taking advantage of the benefits of a prestressed system. The presented method consists of six steel bars: two prestressed vertical bars to introduce a prestressing force on the masonry wall, two diagonal bars to resist shear deformation, and two horizontal bars to maintain the configuration. To evaluate the effects of this new technique, four full-scale specimens, including a control specimen, were tested under combined loadings that included constant-gravity axial loads and cyclic lateral loads. The experimental results were analyzed in terms of the shear strength, initial stiffness, dissipated energy, and strain history. The efficiency of the external prestressed steel-bar truss unit was validated. In particular, a retrofitted specimen with an axial load level of 0.024 exhibited a more stable post behavior and higher energy dissipation than a control specimen with an observed complete sliding failure. The four vertical bars of the adjacent retrofitting units created a virtual column, and their strain values did not change until they reached the peak shear strength. The shear capacity of the masonry wall structure with external prestressed steel-bar truss units could be predicted using the model suggested by Yang et al.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.359-362
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• 1999

Partially prestressed concrete members are concrete members reinforced with a combination of prestressed and non-prestressed reinforcement, and also can offer advantages of reinforced concrete. The objective of this study is to develop a design program using Visual Basic language according to the limit state design method which controls crack and check fatigue effectively for partially concrete members.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.05a
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• pp.31-36
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• 1997

In this thesis, the safety assessment method of the continuous prestressed beam bridge using the service load were studied. From the field test results of the continuous prestressed beam bridge, CAE(composite action factor) and $P_{n}$(capacity load of bridge) were assessed, and these factors were applied to safety assessment of the continuous prestressed beam bridge.

• Structural Engineering and Mechanics
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• v.3 no.6
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• pp.555-567
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• 1995

Design curves have been prepared for prestressed rectangular beam section based on BS 8110, for determining area of steel for any given cross section, for stresses in concrete and steel and for the design moment. The design moment and the area of steel have been expressed in dimensionless form in terms of cross sectional dimensions and the characteristic strength of concrete. The choice and combination of design parameters result in considerably less number of curves as aid for design of rectangular prestressed beam sections, than those reported in CP 110 (Part 3).

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.520-525
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• 1996

Recently, the prestressed concrete long-span bridegs are increasingly built at various locations in the world. The mechanical and structural behavior of prestressed concrete bridges is very complex because of nonlinear and time-dependent material behavior and sequential change of structural system due to stepwise construction. These factors may cause construction errors with respect to design value and monitoring system is needed to minimize or to protect construction errors. This study presents the basis development of monitoring system for precise construction of large scale prestressed concrete bridges.