• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.41 no.6
• /
• pp.617-625
• /
• 2021

The problems associated with the continuous method of a domestically improved prestressed concrete (PSC) girder and the bending moment of a continuous tendon were studied. Based on the results, a continuous tendon model was proposed that can resist the negative bending moment of an intergirder. This model lowers the anchorage of the continuous tendon as far as possible under the girder, and extends the tendon section arranged under the girder. This method reduces the PS's bending moment in the middle of the span, but maximizes it in the intergirder. This continuous tendon model can offer a suitable method for continuity before manufacturing a composite, which requires a higher design bending moment in the intergirder than in the middle of the span.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.6
• /
• pp.197-208
• /
• 1995

The prestressed concrete continuous members with unbonded tendons were investigated while comparing the experimental data with the analytical results. The comparison was carried out with the program TAPS which can take into account the unbonded tendon effects. The subjects that were interested included the load-deflection response, the design equations for the tendon stress at failure, the effects of bonded reinforcements, the effects of span-depth ratio, the effects of loading type. In this paper, contiriuous prestressed concrete members with unbonded ten dons were investigated. Of twelve tests with continuous members, six were two-span beams and six were three span one-way slats. Analytical results were compared favorably with experimental data and disclosed that the tendon stress at flexural failure is the function of the amount of bonded reinforcements, the loading types and patterns, and the tendon profile.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.10 no.4
• /
• pp.145-154
• /
• 2006

This paper presents a method to enhance the load carrying capacity for a two-span continuous steel-concrete composite beam strengthened with external tendons. The tendon is placed at the bottom of steel beam where the positive bending moment occurs. This results in the reduction of the negative bending moment as well as the positive bending moment. This paper describes the procedure to determine the number of tendon and the initial tendon force for the target rating factor in the rating factor equation. An example beam is given to demonstrate the proposed procedure, and it validity is confirmed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.291-296
• /
• 2002

In order to apply precast decks to the continuous composite bridges, several experiments and analytical studies were performed. For the continuous composite bridges, special attention should be paid to the transverse joints in negative moment region. Judging from the results, combination of longitudinal internal prestressing tendon and the external tendon can be effectively used for the prevention of cracking in the negative moment region of precast decks.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1994.04a
• /
• pp.7-12
• /
• 1994

In structural analysis of prestressed concrete continuous flexural mambers, secondary effects produced by tendon forces should be reasonably estimated. The secondary moment at service load stags is normally used for ultimate required moment caculation in strength design. This concept has to be reviewed when precise analysis is performed considering construction step, time dependent properties of concrete and tendon. An ultimate moment computation proposed, concept and structural behavior. The previously proposed procedure by other researcher and the proposed procedure are compared and reviewed for the currently constructed precast prestressed concrete bridge.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.985-990
• /
• 2001

The widened Seoul-Bridge is the first continuous 8-span prestressed concrete(PSC) girder bridge in domain. The construction sequence of the bridge consists of S steps in a large way. The measuring in construction stage includes the determination of the allowable fluctuation value of beam stress in each step and the measurement beam stress during prestessing. The measured tendon prestress force was compared with the design value. When it was compared with the analytic result, the difference between the measured stress and the analytic stress was below allowable error. The friction loss and the anchorage slip loss of the tendon prestress force was lower than the design loss value.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.2 no.3 s.6
• /
• pp.101-108
• /
• 2002

There exist many construction joints in segmentally constructed bridge girders. It is required coupling of tendons or overlapping of tendons to introduce continuous prestress through several spans of bridges. Even though tendon coupling method is easier to use in practice, some cracking problems around construction joints have been reported and complicated stress states around construction joints in PSC girders is not clearly investigated. The purpose of this paper is to investigate in detail the complicated longitudinal stress distributions around the construction joints in prestressed concrete girders with tendon couplers. 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 and segmental construction of bridge sections. The present study indicates that the longitudinal stress distributions of PSC girders with tendon couplers are quite different from those of PSC girders without tendon couplers. The longitudinal compressive stresses introduced by prestressing are greatly reduced around coupled joints according to tendon coupling ratios.

• Journal of the Korea Concrete Institute
• /
• v.21 no.1
• /
• pp.105-116
• /
• 2009

Reinforced concrete (RC) structures have been most widely used because of their good economic efficiency. However, it is very weak in tensile stresses and difficult to control deflection due to the heavy self-weight of concrete. On the other hand, it is generally known that prestressed concrete structures can be the most effective to overcome the demerits of RC structures by using various tendon lay-out and its amount. In the prestressed concrete members, the inflection points of tendons should be placed effectively for the deflection control and the moment reduction. Therefore, in this study, the equations of tendon profiles are derived in terms of polynomials that satisfy essential conditions of tendon geometries such as inflection points and natural curved shapes of tendons placed in continuous members, from which vertical components of prestressing forces can be also calculated. The derived high order polynomial expression for the distributed shape of the upward and downward forces was transformed to an simplified equivalent uniform vertical force in order to improve the applicability in the calculation of member deflection. The influences of vertical forces by tendons to deflection and moment in a continuous slab were also considered depending on the distance from column face to the location of tendons. The applicability of the proposed method was examined by an example of deflection calculation for the cases of slabs with and without tendons, and the efficiency of deflection control by tendons was also quantitatively estimated.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.4
• /
• pp.77-83
• /
• 2014

Prestressed concrete girder bridge has been one of the most widely used bridges in the world because of its excellent construction feasibility, economic efficiency, serviceability, and safety. In certain situations, the prestressing tendon is supposed to be bent by the construction error and the radius of curvature at the continuous joint of PSC girders, and this leads to the loss of prestressing force. However, this kind of prestress loss is not considered in the design and construction processes. This study proves that the prestress loss occurs at the continuous joint due to the local bending of tendon by the construction error or the radius of curvature. Also, a method that can reduce this type of prestress loss is proposed, and proved by the experiment. The result shows that maximum 10% of prestress loss occurs at the continuous joint and the proposed block-out method can reduce the prestress loss ratio by maximum 5%, approximately. This means that the block-out method can enhance the prestressing efficiency of continuous PSC girder bridges.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.681-684
• /
• 1999

The development of external prestressing methods has been one of the major trends in the concrete bridge constructions over the past decades. One of the promising methods to enhance the flexural strength of a externally prestressed girder is to place the tendons with large eccentricities. The test results in this study showed that the external prestressing of a composite girder increased the range of the elastic behavior, reduced deflections, increased ultimate strength, and added to the redundancy by providing the multiple stress paths. This study was conducted on the concrete bridges reinforced by the continuous girders and the external prestressing.