• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.3A
• /
• pp.329-336
• /
• 2010

An experimental study to evaluate bursting behavior in anchorage zone of the standard PSC I girders (span length : 30 m) has been carried out. The arrangement of bursting reinforcement in anchorage zone of the standard PSC I girders is considered to be designed without accurately reflecting the stress flows in the end zone of the PSC I girders caused by presstressing forces of the tendons. Also, due to excessive arrangement of the bursting bars, the workability of the girder is decreased greatly. In this study, three specimens with the same dimensions as the end zone of the standard PSC I girder are prepared and the experiment is carried out by applying PS forces. The bursting reinforcement of each specimen consists of 100 mm, 200 mm, and 300mm spacings, respectively. The experimental results show that the range of the PS forces to cause crack in the anchorage zone of the specimen are more than 1.6 times of the design PS forces. The bursting cracks occur in the vertical direction on the inside of all specimens. After applying 2.7 times of the design PS force, some of the transverse bursting reinforcements only in the specimen reinforced by 300 mm spacing yielded. The experimental results show that the anchorage zone of the standard PSC I girders arranged by 300 mm spacing of the bursting reinforcements which is the maximum spacing allowed in the road bridge design specifications, can be considered safe enough.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.40-43
• /
• 2004

A new design method for prestressed concrete girder is proposed in this study, which steps for manufacturing are; (1) the bottom part of concrete girder is placed and pretensioned by the first post-tensioning performed on the tendons located in the bottom part of concrete girder, and (2) the next step which consists of concrete placing and post-tensioning operation is followed by the previous step if required. This indicates that sufficient compressive stress can be effectively introduced at the bottom face in stepwise manner, when compared to conventional PSC girder. Two specimens are prepared and tested to investigate the short-term behavior of the PSC girders manufactured by the proposed method. Section Analysis results exhibit good agreements with the test results in terms of strain distribution across the girder section. In addition, flexural strength obtained from the tests is found to be similar to the expected based on Code(Korea). These demonstrate that the method proposed in this study is applicable to the design of PSC girders.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5A
• /
• pp.823-832
• /
• 2006

To ensure the serviceability requirements of PSC composite girder bridges, it is essential to predict the stresses and deformations of the structure under service load conditions. Stresses and deformations vary continuously with time due to the effects of creep and shrinkage of concrete and relaxation of prestressing steel. The importance of these time-dependent effects is much more pronounced in precast prestressed concrete structures built in stages than in those constructed in one operation. In this paper, time-dependent analyses for PSC composite bridges using 30m standard girders have been conducted considering with the variation of the times of introducing initial prestressing forces and casting concrete. A computer program has been developed for the time-dependent analysis of simple or continuous PSC composite girders and parametric studies are conducted. Based on the numerical results, it is investigated the long-term behaviors of PSC composite girder bridges and discussed the limitations of the current codes for the prestress loss.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.524-527
• /
• 2004

Recently, precast concrete products have been increasingly used in the construction of bridges except for special bridges like long-span bridge due to their easy and high-quality construction. Specially the use of precast prestressed concrete hollow box slab bridges is also increased due to the merits in their construction. Thus, an experimental evaluation of flexural behavior of the precast PSC hollow box slab bridges and a development of effective analytical technique for the behavior are necessary. For the development, experimental study on the flexural behavior of the precast bridges up to ultimate states is needed. In this study, two full-scale precast PSC hollow box slab girders are manufactured and full-scale flexural failure tests of the girders subjected to cyclic loading are carried out. For the failure analysis of the girders, the so-called volume control method is applied to finite element analysis of the precast PSC hollow box slab girders discretized using multi-layered shell elements. The analytical results by the volume control method is verified by comparing with test results.

• Journal of the Korea Concrete Institute
• /
• v.11 no.5
• /
• pp.21-31
• /
• 1999

The companion paper presents an analytical model to predict behaviors of PSC-Beam bridges according to continuity of spans. This paper aims at providing several examples of its application to PSC-Beam bridge. In this regard, many uncertainties affecting to the continuity of spans (such as the ultimate shrinkage strain of slab and girders, the prestressing creep of girders, and the time adopting prestressing force) are analysis in detail. Moreover, to increase the serviceability and to remove th inherent structural defects including the cracking at interior supports, a necessity for the parametric studies of PSC-Beam bridges reflecting the construction sequence is emphasized.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.23 no.6
• /
• pp.579-592
• /
• 2010

This paper presents a multi-phase model update approach for system identification of prestressed concrete (PSC) girders under various prestress forces. First, a multi-phase model update approach designed on the basis of eigenvalue sensitivity concept is newly proposed. Next, the proposed multi-phase approach is evaluated from controlled experiments on a lab-scale PSC girder for which forced vibration tests are performed for a series of prestress forces. On the PSC girder, a few natural frequencies and mode shapes are experimentally measured for the various prestress forces. The corresponding modal parameters are numerically calculated from a three-dimensional finite element (FE) model which is established for the target PSC girder. Eigenvalue sensitivities are analyzed for potential model-updating parameters of the FE model. Then, structural subsystems are identified phase-by-phase using the proposed model update procedure. Based on model update results, the relationship between prestress forces and model-updating parameters is analyzed to evaluate the influence of prestress forces on structural subsystems.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.23 no.3
• /
• pp.303-314
• /
• 2010

A study for the nonlinear analysis method of prestressed concrete(PSC) girders with external tendons is presented. The PSC girders with external tendons show the complex nonlinear behavior due to the slip of external tendons at deviator and the change of eccentricity between the girders and external tendons. The external tendon between anchorage-deviator or deviator-deviator is modeled as an assemblage of the curved elements. The slip effect of the external tendon at deviator is taken into account using the force equilibrium relationship between the friction force and the driving force at each deviator. The finite element model and analysis method of the external tendon suggested herein are integrated in the nonlinear analysis program of segmentally erected PSC frames developed by the authors. The proposed analysis method is verified through the comparison of the analysis and experimental results obtained from other investigators. From the ultimate analysis results of PSC beams with external tendons having different number of deviators, the yielding and ultimate loads of PSC beams found to be increased as the number of deviators are increased. In addition, the ultimate capacity of the PSC beam increases according to the increase of friction coefficient between deviator and external tendon, whereas found to decease over the certain value of friction due to the effect of the moment transmitted to the member by the friction force exerted from the external tendon.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.4A
• /
• pp.707-717
• /
• 2006

As an alternative to conventional prestressed concrete (PSC) girders, various types of PSC girders are either under development or have already been applied in bridge structures. Incrementally prestressed concrete girder is one of these newly developed girders. According to the design concept, these new types of PSC girders have the advantages of requiring less self-weight while having the capability of longer spans. However, the dynamic interaction between bridge superstructures and passing trains is one of the critical issues concerning these railway bridges designed with more flexibility. Therefore, it is very important to evaluate modal parameters of newly designed bridges before doing dynamic analyses. In the present paper, a 25 meters long full scale PSC girder was fabricated as a test specimen and modal testing was carried out to evaluate modal parameters including natural frequencies and modal damping ratios at every prestressing stage. During the modal testing, a digitally controlled vibration exciter as well as an impact hammer is applied, in order to obtain precise frequency response functions and the modal parameters are evaluated varying with construction stages. Prestressed force effects on changes of modal parameters are analyzed at every incremental prestressing stage. With the application of reliable properties from modal experiments, estimation of dynamic performances of PSC girder railway bridges can be obtained from various parametric studies on dynamic behavior under the passage of moving train. Dynamic displacements, impact factor, acceleration of the slab, end rotation of the girder, and other important dynamic performance parameters are checked with various speeds of the train.

• Journal of the Korea Concrete Institute
• /
• v.20 no.2
• /
• pp.231-237
• /
• 2008

This study was performed to evaluate joint behavior of prestressed concrete(PSC)-steel mixed girders through the flexural test of 14 beams according to embedded length, amount of reinforcing steel, stud arrangement, and prestressing force. All test beams were failed by turns of desertion of reinforcing steel, stud, and steel plate. From test results, prestressing force was more effective on performance of connection than stud arrangement and reinforcing steel. And the spacing of stud is also more effective than embedding length. This paper also presented 3D nonlinear analysis considering the slip of composite section as well as the static load tests of PSC-steel mixed girders. According to the slip modulus, the nonlinear analysis showed that the behavior of hybrid girders could be divided into three parts as full-composite, partial-composite and non-composite. However, the experimental results showed that the PSC-steel hybrid girders with shear connectors took the part of partial composite action in ultimate load stage. In addition, it was founded that stud shear connectors and welded reinforcements were contributed to improve the ultimate strength of hybrid girders for about 20%.

• Journal of the Korea Concrete Institute
• /
• v.16 no.4 s.82
• /
• pp.573-579
• /
• 2004

For the fast construction and replacement of bridges in urban area, a prefabricated bridge system can be an excellent alternative. Details of prefabricated slabs for PSC girders were developed and static tests on shear connections were conducted to propose design equations of the shear connection. Stirrups and stud connectors were used as shear connectors and non-shrink mortar was used for the filling material in shear pockets for shear connectors. Stirrups and studs were fabricated to insert embedded nut-type devices in PSC girders. Shear strength of the shear connection considering chemical bond, friction and mechanical connectors was evaluated and empirical equations were suggested. Due to the mechanical connectors, ultimate slip capacity of the shear connection was sufficient for shear load redistribution, and suggested details of the shear connection showed good performance in terms of strength and ductility.