• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.535-540
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• 2001

In the early construction phase of the Korea Train Express (KTX), the Movable Scaffolding System (MSS) for the top structure of the bridge was the predominant construction method. But the method had to be changed due to arising problems and an alternative method had to be found. Company H that participated in Korea Train Express construction project achieved excellent results of performance through the introduction of the Precast Span Method (PSM), which has been previously successfully employed in foreign express train projects. This study intends to verify the superior performance of PSM over MSS in the KTX construction process by conducting a comparative analysis on PMS and MSS based on the field experience of company H. This study will not only help to understand PSM, which is expected to expand its future scope of application, but also contribute to solve the problems of PSM that occurred during the construction phase.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.317-327
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• 2001

In this paper, a relation to calculate design moments for reinforced concrete(RC) bridges constructed by movable scaffolding system(MSS) is introduced. Through the time-dependent analysis of RC bridges considering the construction sequence, the structural responses related to the member forces and deflections are reviewed, and a governing equation for determination of the design moment, which includes the creep deformation, is derived on the basis of the displacement-force condition at every constructuion stage. By using the relation, the design moment and its variation over time can easily be obtained only with the elastic analysis results without additional time-dependent analysis. In addition, correlation studies with the results by rigorous numerical analyses are conducts to verify the applicability of the introduced relation, and a more reasonable guideline for the determination of design moments is proposed on the basis of the obtained moment envelop.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.167-174
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• 2005

Through time-dependent analyses of RC bridges constructed by a movable scaffolding system (MSS) considering the construction sequence and creep deformation of concrete, structural responses related to the member forces are reviewed. On the basis of the compatibility condition and equilibrium equation at every construction stage, basic equations that can describe the moment variation with time in movable scaffolding construction are derived. By using the introduced relations, the design moment and its variation over time can easily be obtained with only the elastic analysis results and without additional time-dependent analyses considering the construction sequences. In addition, the design moments determined by the introduced equations are compared with the results from a rigorous numerical analysis with the objective of establishing the relative efficiencies of the introduced equations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.487-494
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• 2009

Friction coefficients of the prestressing tendon are the basic information required to control the prestressing force introduced to PSC structure during jacking. However, the friction coefficients show considerable differences depending on the specifications, causing much confusion to designers. In this study, the ranges of the friction coefficients presented in domestic and foreign specifications are compared together to clarify the differences. Then, a procedure is proposed that can be used to estimate the wobble and curvature friction coefficients from field data such as elongation and prestressing force and from theory related to the friction. The procedure is applied to various tendon profiles of several PSC bridges constructed by ILM, FCM and MSS. The resulting values are compared with those presented in some specifications and assumed in jacking and a reasonable range of the friction coefficient is discussed. Lift-off tests are also performed in some bridges to further verify the results. The resulting wobble friction coefficients are not as small as those presented in AASHTO specifications but range from the lower limit to mid point of domestic specifications, while the curvature friction coefficients approach or slightly exceed the upper limit.

• Journal of the Korea Concrete Institute
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• v.13 no.1
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• pp.1-8
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• 2001

Recently, prestressed concrete(PSC) bridge structures with many repetitive spans have been widely constructed using the segmental construction method in many countries. In these segmentally constructed PSC bridges, there exist many construction joints which is required coupling of tendons or overlapping of tendons to introduce continuous prestress through several spans of bridges. The purpose of this paper is to investigate in detail the complicated stress distributions around the tendon coupled joints in prestressed concrete girders. To this end, a comprehensive experimental program has been set up and a series of specimens have been tested to identify the effects of tendon coupling. The present study indicates that the longitudinal and transverse stress distributions of PSC girders with tendon couplers are quite different from those of PSC girders without tendon couplers. It is seen that the longitudinal compressive stresses introduced by prestressing are greatly reduced around coupled joints according to tendon coupling ratios. The large reduction of compressive stresses around the coupled joints may cause deleterious cracking problems in PSC girder bridges due to tensile stresses arising from live loads, shrinkage and temperature effects. The analysis results by finite element method correlate very well with test results observed complex strain distributions of tendon coupled members. It is expected that the results of this paper will provide a good basis for realistic design guideline around tendon coupled joints in PSC girder bridges.