• Journal of Korean Society of Steel Construction
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• v.12 no.5 s.48
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• pp.549-558
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• 2000

In strengthening structure, the external post-tensioning method which secure clearness in the structure analysis process is adopted to bridges as well as architecture structure. In this study, to investigate the behavior of composite beam in the process of post-tensioning, the amount of prestress force loss, the amount of prestressed compression stress at the lower flange and the behavior of lower flange connected with anchorage are analyzed by comparing the results of finite element analysis with the measured results of installed strain gauges. After finishing the post-tensioning, the strengthening effect of external post-tensioning method is analyzed by static loading test. It is also investigated that the strengthening effect of shear section in the harped external post-tensioning specimens.

• Computational Structural Engineering
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• v.8 no.4
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• pp.75-85
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• 1995

The purpose of the present study is to develop a computer program which can be used to analyze prestressed concrete structures containing either bonded or unbonded tendons. To accomplish this, first, the concrete, nonprestressed, and prestressed steels are modeled with cyclic constitutive laws to take into account the various loading effects. Then, the hybrid-type element method is derived to improve the computations capability of stresses and strains, especially for the unbonded tendon. Since it allows one to determine the cross-sectional deformations in an element without any assumptions for its deformed shape, the element length can be much longer than that of the conventional finite element method. In order to achieve such a long element, various integral schemes are examined to implement them into the program. Then, the computational method for prestressing effects is developed consistently with the analytical method for the structure. Finally, analytical studies for actual tests were carried out to verify the program developed in this study.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.237-244
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• 2020

This study investigates the effect of the outrigger wall reinforced with post-tension on reducing differential column shortening. Since the outrigger wall is a concrete structure, the effect of its long-term behavior should be considered. The long-term behavior of the outrigger wall increases differential column shortening and decreases the shear force acting on the outrigger. When the stiffness of the outrigger becomes small, the effect of its long-term behavior increases. Furthermore, a method of reinforcing with post-tension to reduce differential column shortening is proposed. Following the analysis, it was confirmed that the post-tension method shows a significant reduction in the differential column shortening. This study shows that the effect of the outrigger wall reinforced with post-tension on reducing differential column shortening increases with the prestressing force of tendon.

• Geomechanics and Engineering
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• v.10 no.6
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• pp.737-755
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• 2016

The load transfer depth of a ground anchor is the minimum length required to transfer the initial prestressing to the grout column through the bonded part. A thorough understanding of the mechanism of load transfer as well as accurate prediction of the load transfer depth are essential for designing an anchorage that has an adequate factor of safety and satisfies implicit economic criteria. In the current research, experimental and numerical studies were conducted to investigate the load transfer mechanism of ground anchors based on a series of laboratory and field load tests. Optical FBG sensors embedded in the central king cable of a seven-wire strand were successfully employed to monitor the changes in tensile force and its distribution along the tendons. Moreover, results from laboratory and in-situ pullout tests were compared with those from equivalent case studies simulated using the finite difference method in the FLAC 3D program. All the results obtained from the two proposed methods were remarkably consistent with respect to the load increments. They were similar not only in trend but also in magnitude and showed more consistency at higher pullout loading stages, especially the final loading stage. Furthermore, the estimated load transfer depth demonstrated a pronounced dependency on the surrounding ground condition, being shorter in hard ground conditions and longer in weaker ones. Finally, considering the safety factor and cost-effective design, the required bonded length of a ground anchor was formulated in terms of the load transfer depth.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.1
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• pp.15-22
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• 2011

In this research, static load test is performed to verify the arch effect and structural performance of CFTA(Concrete-Filled and Tied steel tubular Arch) girder, and FE(Finite Element) analysis is performed to investigate validity of the test result. CFTA girder is designed to maximize the benefit of each material, such as steel plate, filled concrete and PS tendon. Static load test is performed based on the frame-analysis result of 12m sample miniature model. The result of static load test is that structural performance and safety of CFTA girder are confirmed and there is different deflection mode with other structural form result from arch effect. FE analysis with ABAQUS is also performed to show the validity of the truck collision safety and static load test.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.3
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• pp.165-172
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• 2019

In this study, the shear strength of prestressed concrete deep beams is predicted using finite element analysis, and the variation in the shear strength according to the degree of prestressing is investigated. Numerical analysis results are compared with results obtained by the strut-and-tie model and associated experiments. Numerical analyses are performed on prestressed concrete deep beams with different values of concrete strength, effective prestress, ratio of tensile reinforcement, and shear span to effective depth ratio. The shear strength predicted by the numerical analysis is similar to the experimental value obtained, with an error of less than 5%. However, the strut-and-tie model highly overestimated the shear strength of prestressed concrete deep beams with a concentrated loading area. The ultimate shear capacity of prestressed concrete deep beams increased linearly with increasing prestresss applied to the tendon.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.611-618
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• 2008

CFRP (carbon fiber reinforced polymer) tendons can be used as an alternative to solve the corrosion problem of steel tendons. Since CFRP tendons are vulnerable to transverse pressure and stress concentration, the conventional anchorage system used for steel tendons can create an unreliable load carrying capacity and may result in a premature failure. Therefore, it is necessary to develop the anchorage system that is well suited for CFRP tendons. There are many types of anchorage systems for CFRP tendons, which can be classified into three types: wedge-type anchorage, bond-type anchorage, and compression-type anchorage. This paper deals with the compression-type anchorage system manufactured through swaging technology. Based on the previous test results performed by the authors, the dimension of anchorage sleeve, the use and non-use of the insert, and the compression pressure on the sleeve have been selected as the major parameters affecting the performance of the compression-type anchorage. Some anchorage sleeves have been tapered to reduce the stress concentration. Test results revealed that the performance of the anchorage system depends mainly on the dimension and the compression pressure. It has been verified that the tapered sleeve can effectively reduce the stress concentration.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3D
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• pp.499-509
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• 2006

Precast concrete deck has many advantages comparing with the in-situ concrete deck, and has been successfully applied to replacement of the deteriorated decks and to the newly constructed highway bridges in domestic region. In order to apply the precast decks into the railway bridges, however, differences of the load characteristics between the highway and the railway should be properly taken into account including the train load, longitudinal force of the continuous welded rail, acceleration or braking force, temperature change and shrinkage. Proper level of the longitudinal prestress of the tendons that can ensure integrity of the transverse joints in the deck system is of a primary importance. To this aim, the longitudinal tensile stresses induced by the design loads are derived using three-dimensional finite element analyses for the frequently adopted PSC composite girder railway bridge. The effect of the temperature change is also investigated considering the design codes and theoretical equations in an in-depth manner. The estimated proper prestress level to counteract those tensile stresses is above 2.4 MPa, which is similar to the case of the highway bridges.