• Journal of the Korean Society for Railway
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• v.9 no.4 s.35
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• pp.467-472
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• 2006

This paper deals with the applicability of long-gauge deformation fiber optic sensors (FOS) to prestressed concrete structures. A main motivation is the desire to monitor the deflection of the railway bridges without intervenes of the signal intensity fluctuations. A 25 m long, 1.8 m deep PSC girder was fabricated compositely with 22 cm thick reinforced concrete deck. Two pairs of 3 m long-gauge sensors are attached to the prestressed concrete girder with parallel topology. Using the relationship between curvature and vortical deflection and the quadratic regression of curvatures at the discrete point, it is possible to extrapolate the deflection curve of the girder. The estimated deflection based on the developed method is compared with the results using conventional strain gauges and LVDTS. It has been demonstrated that the proposed instrumentation technique is capable of estimating the vertical deflection and neutral axis position of the prestressed concrete girder up to weak nonlinear region.

• Proceedings of the KSR Conference
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• 2011.10a
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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.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.501-506
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• 2002

The unbonded prestressed concrete(PSC) members exhibit very different structural behavior from that of bonded PSC members because of having different tendon stress increment. Recently, AASHTO changed the provision of ultimate tendon stress with unbonded tendons, because some researches tried to improve the provision of ultimate tendon stress with unbonded tendons. The purpose of the present study is to compare various Codes with the ultimate failure stresses of prestressing(PS) steels for the unbonded PSC members. To this end, Some national Codes have been collected and analyzed. A series of major influencing variables have been included in the analysis. It was found that the span-depth ratio, neutral axis depth-effective depth ratio, concrete compressive strength, effective prestress, and prestressing steel ratio have great influence on the ultimate failure stress of PS steel in unbonded PSC members. The Comparison indicates that existing formulas including ACI and domestic Code's equations shows some unwarranties. The present study allows more realistic analysis and design of prestressed concrete structures with internal unbonded tendons.

• Journal of the Korean Society of Safety
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• v.32 no.4
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• pp.53-58
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• 2017

The rebound hammer test and the measurement of ultrasonic pulse velocity(UPV) have been widely used for the physical properties & condition evaluation of reinforced & prestressed concrete structures for a long time, but the acoustoelastic effects by the prestressing in the prestressed concrete structures on the rebound number and ultrasonic pulse velocity have not been studied clearly. Therefore, this study investigated the data distribution of the rebound numbers and ultrasonic pulse velocities in reinforced and prestressed concrete slabs of $3000{\times}3000mm$ with a thickness of 250 mm. Also, the Kolmogorov-Smirnov goodness-of-fit test was done in order to identify statistical consistency and reliability. The statistical analysis results show that the rebound number and ultrasonic pulse velocities increased about 1.9% and 2.5%, respectively when prestressing was applied. As expected, the UPV shows better statistical reliability and potential for in situ evaluation than the RB because the RB are more sensitive to testing posture, surface condition, temperature and humidity so on. The experimental data in this study can be used for the condition assessment of reinforced and prestressed concrete structures by the rebound number and ultrasonic pulse velocity.

• Magazine of the Korea Concrete Institute
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• v.16 no.1 s.78
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• pp.12-21
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• 2004

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.78-88
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• 2012

Although structural concrete is well known for its good economic efficiency, it has limits of structural performance due to the low tensile strength, for which new structural members utilizing various concrete composite materials have been developed. Steel Fiber-Reinforced Concrete(SFRC) has great tensile strength, which is the one of the excellent composite material to complement the weakness of concrete, and it is also considered as a good alternative to prevent the explosive failure of high strength concrete under fire. Also, prestressed concrete members are of great advantages to long span structures and have greater shear strength compared to conventional reinforced concrete members. In this research, thus, a total of 22 direct shear test specimens were fabricated and tested to understand the shear behavior of Steel Fiber-Reinforced Prestressed Concrete(SFR-PSC) members, in which SFRC members combined with prestressing method. Based on the test results, the constitutive equations of shear behavior at crack interfaces were proposed, which provided good estimation on the shear behavior of the SFR-PSC direct shear test specimens.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.695-703
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• 2012

Recently, major infrastructure such as bridges, tunnels, PCCVs (Prestressed Concrete Containment Vessel), and gas tanks are Prestressed Concrete (PSC) structure types, which improve their safety by using confining effect from prestressing. Generally, concrete is known to be an outstanding fire resistant construction material. Because of this reason, researches related to extreme fire loaded PSC member behaviors are not often conducted even though PSC behavior under extreme fire loading is significantly different than that of ordinary reinforced concrete (RC) behavior. Therefore, in this study, RABT fire loading tests were performed on bi-directionally prestressed concrete panels with $1000{\times}1400{\times}300mm$ dimensions. The prestressed specimens were applied with 430 kN prestressing (PS) force using unbonded PS thread bars. Also, residual strength structural tests of fire tested PSC and ordinary RC structures were performed for comparison. The study results showed that PSC behavior under fire loading is significantly different than that of RC behavior.

• Computers and Concrete
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• v.3 no.1
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• pp.43-64
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• 2006

A tendon model that can effectively be used in finite element analyses of prestressed concrete (PSC) structures with bonded tendons is proposed on the basis of the bond characteristics between a tendon and its surrounding concrete. Since tensile forces between adjacent cracks are transmitted from a tendon to concrete by bond forces, the constitutive law of a bonded tendon stiffened by grouting is different from that of a bare tendon. Accordingly, the apparent yield stress of an embedded tendon is determined from the bond-slip relationship. The definition of the multi-linear average stress-strain relationship is then obtained through a linear interpolation of the stress difference at the post-yielding stage. Unlike in the case of a bonded tendon, on the other hand, a stress increase beyond the effective prestress in an unbonded tendon is not section-dependent but member-dependent. The tendon stress unequivocally represents a uniform distribution along the length when the friction loss is excluded. Thus, using a strain reduction factor, the modified stress-strain curve of an unbonded tendon is derived by successive iterations. The validity of the proposed two tendon models is verified through correlation studies between analytical and experimental results for PSC beams and slabs.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.711-730
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• 2010

This study presents the design of autonomous smart sensor nodes for damage monitoring of tendons and girders in prestressed concrete (PSC) bridges. To achieve the objective, the following approaches are implemented. Firstly, acceleration-based and impedance-based smart sensor nodes are designed for global and local structural health monitoring (SHM). Secondly, global and local SHM methods which are suitable for damage monitoring of tendons and girders in PSC bridges are selected to alarm damage occurrence, to locate damage and to estimate severity of damage. Thirdly, an autonomous SHM scheme is designed for PSC bridges by implementing the selected SHM methods. Operation logics of the SHM methods are programmed based on the concept of the decentralized sensor network. Finally, the performance of the proposed system is experimentally evaluated for a lab-scaled PSC girder model for which a set of damage scenarios are experimentally monitored by the developed smart sensor nodes.

• International Journal of Concrete Structures and Materials
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• v.4 no.2
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• pp.77-87
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• 2010

Prestressed concrete (PSC) I-type girders have been used for span length around up to 40 m in domestic region. PSC girders are very cost effective girder type and extending their lengths more than 50 m will bring large benefit in cost. A new design method was proposed by combining two notable design concept in order to extend the applicable span length in this study. First of all, several numbers of openings was introduced in the girder web, and half of the anchorage devices were moved into the openings. In this way, large compressive stress developed at end zone was reduced, and the portion of design load coming from self-weight was reduced as well. Secondly, prestressing force was introduced in the girder not once at the initial stage, but through multiple loading stages. A full scale girder with the length of 50 m with the girder depth of 2 m was fabricated, and a flexural test was conducted in order to verify the performance of newly developed girder. Test results showed that the new holed web design concept can provide a way to design girders longer than 50 meters with the girder height of 2 m.