• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.489-499
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• 2009

It is quite difficult to predict the flexural strength of post-tensioned members with unbonded tendons (unbonded posttensioned members, UPT members) because of debonding behavior between concrete and prestressing tendons, which is different from that with bonded tendons. Despite many previous researches, our understanding on the flexural strength of UPT members is still insufficient, and thus, national codes use different methods to calculate the strength, which quite often give very different results. Therefore, this paper reviews various existing methods, and aims at proposing an improved rational strength model for UPT flexural members having better accuracy. Additionally, a database containing a large number of test data on UPT flexural members has been established and used for verification of the proposed flexural strength model. The analysis results show that the proposed method provides much better accuracy than many existing methods including the rigid-body model that utilizes the assumption of concentrated deformation and plastic hinge length, and that it also gives proper consideration on the effects of primary parameters such as reinforcement ratio, loading pattern, concrete strength, etc. Especially, the proposed method also well predicts the ultimate stress of unbonded tendons of over-reinforced members, which are often possible in construction fields, and high strength concrete members.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.163-172
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• 2011

The CFTA girder developed is a concrete filled steel tubular system with arched shape and external post-tensioning (PT) tendons which control the initial camber and the bending stress of the girder. In the present study the effects of the PT tendons on the dynamic behavior of the girder subjected to a moving vehicle load are numerically investigated. Various levels for the tendon quantity and the tendon forces are considered, using the existing FE model of the girder. The vehicle considered is a DB-24 truck and is modeled with two tracks-three axles. Equivalent-load pulse time histories are applied to each node to simulate the moving vehicle, depending on the time of arrival and the discretization. The vehicle speeds are varied from 40 km/hr to 100 km/hr with increment of 20 km/hr. The analysis results show that the tendon forces do not produce any influences on the dynamic responses of the girder. However the dymamic deflection of the girder increases when a smaller amount of tendons is used. The Dynamic Amplification Factors (DAF) are evaluated based on the static and dynamic responses. Much lower values of the DAF are obtained, even no tendons applied, than those provided by the design criteria of the AASHTO LRFD and the Korea Highway Standard Specification.

• Clinics in Shoulder and Elbow
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• v.10 no.2
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• pp.160-166
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• 2007

Purpose: The current study assessed the factors affecting outcomes of primary repair procedures in tears of multiple rotator cuff tendons. Materials and Methods: Among the cases of rotator cuff tears involving two or more tendons receiving operations between 1997 and 2003, The clinical results of 19 cases with more than 2 years follow-up were evaluated by the UCLA score. We evaluated the correlation of trauma, active motion, acromiohumeral distance, tear size, and surface area with the UCLA score using Pearson's linear correlation coefficient (PLCC). Results: UCLA scores increased significantly in all cases, from 9 to 26.1 on average. However, the results were good in 53%, and poor in 47% according to Ellman's criteria. Trauma, active elevation, acromiohumeral distance, and tear size did not correlate with the UCLA score, but the tear surface area was inversely correlated with the score (PLCC=-0.696). Cases with degeneration of the infraspinatus muscle above Goutallier grade III on MRI showed worse results than cases with less degeneration. Conclusion: The clinical results of primary repair of rotator cuff tears involving multiple tendons were satisfactory in 53% of patients. Large tear surface area and severe degeneration of the infraspinatus were poor prognostic factors.

• Anatomy & Biological Anthropology
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• v.30 no.2
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• pp.61-65
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• 2017

This report describes a variation of the tendinous slip of the flexor digitorum longus (FDL) for the great toe. In addition, compositions of the long flexor tendons for all five toes were examined. The tendons of the FDL in the foot were investigated in 66 specimens of embalmed Korean adult cadavers. The tendons of the flexor hallucis longus (FHL) and the FDL with the lumbrical muscles were cut at the calcaneus and the metatarsophalangeal joints and were removed en bloc specifically to observe the FDL and the FHL tendons of the great toe. The tendinous slip of the FDL for the great toe was found bilaterally in the foot of a 52-year-old male. Its prevalence was two of 66 specimens (3.0%). The tendinous slip of the FDL for the great toe passed forward the great toe, and it constituted the superficial portion of the long flexor tendon for the great toe. The tendon of the FHL passed forward to constitute the deep portion of the long flexor tendon for the great toe. Thus, both the tendinous slip of the FDL and the tendon of the FHL composed the long flexor tendon for the great toe. The tendinous slip of the FDL and the tendon of the FHL for the great toe were similar in thickness; thus, each tendinous slip of the FDL and the tendon of the FHL were approximately one-half of the long flexor tendon for the great toe in thickness. The present study demonstrated an anatomical variation of the interconnection between the FHL and the FDL tendons, which will be useful for various surgeries and biomechanical research.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.619-624
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• 2002

A prestressed/precast concrete system was used to build the new Asian Olympic Stadium Project in Pusan, Korea. The stadium(mainly intended for cycle racing) is designed for the 2002 Asian Olympic Games and has a seating capacity of 20,000 spectators plus a few private suites. More than 1300 prestressed/precast components were used and they include single columns, primary beams, cantilever beams, double riser stands, and double tees. Especially, a total of 24 cantilever beams is used on the fourth story for the stands and double tees. These 8m long beams are post-tensioned to prevent cracking, to increase their durability and to serve serviceability by vibration. A cantilever section with cast-in-place topping is 800mm wide and 1500mm deep. Cantilever beams are connected to the column with the corbel by cast-in place concrete. Bonded post-tensioning tendons were assembled at the job site. Dead-end anchorages were installed in the end of cantilever beams and live-end anchorage is the opposite of them. This article presents the geometric layouts, design features and so on.

• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.113-119
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• 1999

Fatigue failure is a phenomenon such that structures under cyclic service load is failed by sudden brittle manner. Therefore, in order to obtain structures safety against the fatigue failure during their service lifes, fatigue characteristics should be considered for design and analysis of the structures. As stress range of prestressed (PS) tendons, which governs fatigus characteristic of prestressed concrete (PSC) structures, increases with increased use of partial prestressig, it is more necessary to consider fatigue characteristics of PS tendons. In this paper, direct-tension fatigue experiments with special specimen-setting devices are carried out to obtain fatigue characteristics of domestic low relaxation PS strands having different diameters and PS strands connected with coupler. Then, allowable stress range of fatigue for PSC beams using low relaxation strands are presented for the fatigue examination of prestressed concrete beams applied cyclic loading.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.519-524
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• 1998

The current study is a part of series of research about the evaluation method of the unbonded tendon stress in prestressed concrete member at flexural failure. As the experimental study, a test program with 14 beams and slabs was planed to identify the contribution of each important variable. The variables are (1) the effective prestress, (2) the concrete strength, (3) the amount of tendons (4) the amount of bonded reinforcements, (5) the loading type, (6) the span/depth ratio. It was found that the tendon stress increment decreases as the effective prestress increases. Also, the contributions of concrete strength, amount of tendons, bonded reinforcements, and loading type were observed to affect on tendon stresses. However, the tendon stress increments were minimal at high values of span/depth in contrast with the ACI Code.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.107-112
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• 2001

The IPC(Incremental Prestressed Concrete) which is gradually introducing the tensile force by tendons has been recently developed for reducing the effective depth of PSC bridges. As well known, concrete experiences long-term deformation such as creep and drying shrinkage, and the prediction of the long-term behavior of concrete bridges is essential for both safety and serviceability aspects. This paper was analysed the long-term behavior of a continuous 2-span IPC girder bridge taking into consideration of creep, drying shrinkage and the time of tensile force introduction. As results, the shrinkage of slab concrete increases the negative moment at interior support, and the The difference of concrete ages between slab and girder increases the camber. The effect of initial tensile force is larger than the effect of secondary tensile force in the tendons.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.100-103
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• 2004

Bridges are deteriorating over service life due to over weight vehicles, environmental conditions and so on. In addition to that, those could be classified into low level bridges which are not fit for highway because of upgrade of the design load. Consequently, such reasons impel the bridges to be repaired or strengthened. Among the rehabilitating methods, FRP sheets and externally prestressing methods are preferred recently. This paper presents experimental results about the behavior of PSC beams strengthened by external tendons and CFRP sheets.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.758-761
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• 2004

Prestressing tendons of the nuclear containment building dome are arranged in a non-axisymmetric manner. However, simple axisymmetric modeling of the containment building is often employed to estimate the structural behavior for, e.g. the ultimate pressure, which requires the axisymmetric approximation of the actual tendon arrangements of the dome. A procedure is proposed that can devise the actual 3-dimensional tendon stiffness and prestressing effect into the axisymmetric model. A numerical example of the CANDU type is presented to verify the procedure and to estimate the amount of approximation.