• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.3
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• pp.151-158
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• 2002

Recently, the externally prestressed unbonded steel I-beam bridges have been increasingly built. The mechanical behavior of prestressed steel I-beams which are with external unbonded tendon is different from that of normal bonded PSC beams in a point of that the slip of tendons at deviators and the change of tendon eccentricity occurs, when external loads are applied in external unbonded steel I-beams. The concept of prestressing steel structures has not been widely considered, in spite of long and successful history of prestressing concrete members. In this study, The field experiment on prestressed steel I-beams has been performed in the various aspects of prestressed I-beam including the tend on type and profile.

• Computers and Concrete
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• v.10 no.3
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• pp.241-258
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• 2012

The need for long-span members increases gradually in recent years, which makes issues not only on ultimate strength but also on excessive deflection of horizontal members important. In building structures, the post-tension methods with unbonded tendons are often used for long-span members to solve deflection problems. Previous studies on prestressed flexural members with unbonded tendons, however, were mostly focused on the ultimate strength. For this reason, their approaches are either impossible or very difficult to be implemented for serviceability check such as deflection, tendons stress, etc. Therefore, this study proposed a flexural behavior model for post-tensioned members with unbonded tendons that can predict the initial behavior, before and after cracking, service load behavior and ultimate strength. The applicability and accuracy of the proposed model were also verified by comparing with various types of test results including internally and externally post-tensioned members, a wide range of reinforcement ratios and different loading patterns. The comparison showed that the proposed model very accurately estimated both the flexural behavior and strength for these members. Particularly, the proposed model well reflected the effect of various loading patterns, and also provided good estimation on the flexural behavior of excessively reinforced members that could often occur during reinforcing work.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.335-345
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• 2005

This paper concentrates on the nonlinear analysis of prestressed concrete (PSC) containment structures. Unlike a commercialized program which adopts the perfect bond assumption between concrete and tendon in the analysis of PSC structures, a numerical algorithm to consider the slip effect, simultaneously with the use of commercialized programs such as DIANA and ABAQUS, is introduced in this paper For bonded tendons, the apparent yield stress of an embedded tendon is determined from the bond slip relationship. And for unbonded tendons, Correction for the strength and stiffness of unbonded internal tendons is achieved on the basis of an iteration scheme derived from the slip behavior of tendon along the entire length. Finally, the developed algorithm is applied to two PSC containment structures of PWR and CANDU to verify its efficiency and applicability in simulating the structural behavior of large complex structures, and the obtained result shows that both containment structures represent the ultimate pressure capacity larger than about 3 times of the design pressure.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.79-85
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• 2002

Recently, prestressed H-Beam bridges with external unbonded Tendons are increasingly built. The mechanical behavior of prestressed steel H-beams is different from that of normal bonded PSC beams in a point of the slip of tendons at deviators and the change of tendon eccentricity that occurs, when service load are applied in external unbonded steel H-beams. The concept of prestressing steel structures has been widely considered, in spite of long and successful history of prestressing concrete members. In the study, The flexural test on prestressed steel H-beams has been performed in the various aspects of prestressed H-beam including the tendon type and profile. The load was plotted against the deflection and the strain respectively in the steel beam and prestressing bars. The value expected with the equation of internal force equilibrium and compatibility between the deflection of the bars and the H-beam was found to correlate well with the measured data.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.261-271
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• 2006

Many uncertainties affecting to the structural behavior of prestressed concrete (PSC) bridges reinforced with the un bonded external tendons are analyzed on the basis of the analytical method introduced in the companion paper. Many design parameters, which must be considered in design procedure, such as friction slip at the deviators, number of deviators, time-dependent deformations of concrete, relaxation of tendon and influence of loading history in PSC bridges are reviewed, and a lot of valuable results are obtained through this parametric study. In advance, the structural responses according to the external tendon profiles are analyzed to grasp if an optimum tendon profile depends on the applied loading type, and the obtained results show that the most stable structural response is revealed when the locations of deviators are coincident with the loading points.

• Journal of Korean Association for Spatial Structures
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• v.17 no.4
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• pp.149-157
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• 2017

An innovative analysis method is proposed in this paper for the determination of ultimate resistance of prestressed concrete beams. The proposed method can be applied to simply supported or continuous beams in a unified manner whether structure and external loads are symmetric or not. Through the iterative nonlinear strain compatibility solutions, this method can also be applied to the non-prismatic section/un-symmetrical composite structures under moving load. The conventional studies have used the failure criteria when the strain of concrete reaches 0.003. However compared with bonded case, the value of strain in the reinforcement is much smaller than bonded case, thus, unbonded prestressed cases show compressive failure mode. It is shown that the proposed method gives acceptable results within 5% error compared with the prior experimental results. It can be shown that the proposed method can reach the solution much faster than typical three-dimensional finite element analysis for the same problem. This method is applicable to the existing unbonded prestressed members where deterioration has occurred leading to the reduced ultimate resistance or safety. In all, the proposed procedure can be applied to the design and analysis of newly constructed structures, as well as the risk assessment of rehabilitated structures.

• Magazine of the Korea Concrete Institute
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• v.27 no.3
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• pp.28-31
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• 2015

• Journal of Korean Association for Spatial Structures
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• v.19 no.1
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• pp.45-51
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• 2019

In this study, the static load test and the load transfer test were carried out to evaluate the structural performance of the circular anchorage proposed by the previous study. Specimens were fabricated according to KCI-PS101 and ETAG 013. As a result of the static load test, it was verified that the displacement of the wedge and the strand was kept constant when the tensile force of 80% of the nominal strength of the strand was applied. In the load transfer test, it was confirmed that all the specimens satisfied the stabilization formula of KCI-PS101 and ETAG 013. Post-tensioned one-way slab with circular anchorage were fabricated to evaluate the flexural behavior. All specimens exhibited the same flexural behavior and maximum load. However, the specimen with circular anchorage were advantageous than the rectangular anchorage one in terms of crack control of the anchorage zone.

• Computers and Concrete
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• v.15 no.1
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• pp.55-71
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• 2015

This paper presents a novel harmony search (HS)-based data-driven single input rule modules (SIRMs)-connected fuzzy inference system (FIS) for the prediction of stress in externally prestressed tendon. The proposed method attempts to extract causal relationship of a system from an input-output pairs of data even without knowing the complete physical knowledge of the system. The monotonicity property is then exploited as an additional qualitative information to obtain a meaningful SIRMs-connected FIS model. This method is then validated using results from test data of the literature. Several parameters, such as initial tendon depth to beam ratio; deviators spacing to the initial tendon depth ratio; and distance of a concentrated load from the nearest support to the effective beam span are considered. A computer simulation for estimating the stress increase in externally prestressed tendon, ${\Delta}f_{ps}$, is then reported. The contributions of this paper is two folds; (i) it contributes towards a new monotonicity-preserving data-driven FIS model in fuzzy modeling and (ii) it provides a novel solution for estimating the ${\Delta}f_{ps}$ even without a complete physical knowledge of unbonded tendons.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.1
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• pp.39-46
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• 2018

In this paper, an unbonded post-tensioning anchorage for a single-stranded wire that allows more efficient stress distribution in the post-tensioned anchorage zone was developed by using a finite element analysis using a commercial program. The stress analysis was carried out using a 3D model in the anchorage zone of the concrete member using the developed anchorage. The result of analysis ensured that the developed anchorage reduced the maximum bursting stress in anchorage zone compared to the case of existing anchorage and the location where maximum bursting stress also occurred closer to the anchorage. Bursting force was calculated using AASHTO, modified $M{\ddot{o}}rsch$ and Stone. As a result, it was concluded that an effective reinforcement design of the anchorage zone can be designed by modified $M{\ddot{o}}rsch$.