• Composites Research
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• v.22 no.5
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• pp.24-29
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• 2009

In this paper, a post-tensioned reinforced concrete slab was analyzed by the specially orthotropic laminates theory. Both the geometrical and material property of the cross section of the slab was considered symmetrically with respect to the neutral surface so that the bending extension coupling stiffness, $B_{ij}=0$, and $D_{16}=D_{26}=0$. Reinforced concrete slab behave as specially orthotropic plates. In general, the analytical solution for such complex systems is very difficult to obtain. Thus, finite difference method was used for analysis of the problem. In this paper, the finite difference method and the beam theory were used for analysis. The result of beam analysis was modified to obtain the solution of the plate analysis.

• 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.

• Structural Engineering and Mechanics
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• v.53 no.6
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• pp.1083-1104
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• 2015

This paper provides the results of an experimental investigation into the flexural behavior of continuous two-span unbonded post-tensioned high strength concrete (HSC) beams, strengthened by end-anchored CFRP laminates of different configurations in the hogging region. Implementing two different configurations of end-anchorage systems consisting of steel plates and bolts and carefully monitoring the development of strains throughout the load history using sufficiently large number of strain gauges, the response of beams including the observed crack propagations, beam deflection, modes of failure, capacity enhancement at service and ultimate and the amount of moment redistribution are measured, presented and discussed. The study is appropriate in the sense that it covers the more commonly occurring two span beams instead of the simply supported beams investigated by others. The experiments reconfirmed the finding of others that proper installation of composite strengthening system is most important in the quality of the bond which is essential for the internal transfer of forces. It was also found that for the tested two span continuous beams, the capacity enhancement is more pronounced at the serviceability level than the ultimate. This is an important finding as the design of these beams is mostly governed by the serviceability limit state signifying the appropriateness of the suggested strengthening method. The paper provides quantitative data on the amount of this capacity enhancement.

• Structural Engineering and Mechanics
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• v.86 no.1
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• pp.17-27
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• 2023

To investigate the mechanical behavior of the post-tensioned prestressed concrete lining (PPCL), the desilting tunnel of the Xiaolangdi Hydro Project in China is adopted as a case, and a detailed three-dimensional continuum model verified by the observation results is established for the PPCL. The radial stresses, longitudinal stresses, axial forces and bending moments of the PPCL under the completed cable tension condition (CCTC) and design water pressure condition (DWPC) are analyzed, respectively. The numerical results reveal that the PPCL concrete is significantly compressed in the circumferential direction by the prestress, while the prestress has a negligible influence on the radial stresses of the PPCL concrete. It should be noted that the concrete near the anchor slots has a complex and adverse stress state with stress concentration, longitudinal tensioning and large bending moment. In addition, a simplified shell model and a further simplified beam model which can take the influences of the prestress loss and the anchor slot into consideration are proposed for the PPCL. The results of the simplified models are in a good agreement with these of the three-dimensional continuum model, and they can be used as efficient approaches for the structural design and analysis of the PPCL.

• Earthquakes and Structures
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• v.12 no.1
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• pp.109-118
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• 2017

A novel post-tensioned self-centering (SC) concrete beam-column connection with web friction devices has been proposed for concrete moment-resisting frames. This paper presents a probabilistic performance evaluation procedure to evaluate the performance of the self-centering concrete frame with the proposed post-tensioned beam-column connections. Two performance limit states, i.e., immediate occupancy (IO) and repairable (RE) limit states, are defined based on peak and residual story drift ratios. Statistical analyses of seismic demands revealed that the dispersion of residual drifts is larger than that of peak drifts. Due to self-centering feature of post-tensioning connections, the SC frame was found to have high probabilities to be recentered under the design basis earthquake (DBE) and maximum considered earthquake (MCE) ground motions. Seismic risk analysis was performed to determine the annual (50-year) probability of exceedance for IO and RE performance limit states, and the results revealed that the design objectives of the SC frame would be met under the proposed performance-based design approach.

• Journal of Korean Association for Spatial Structures
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• v.20 no.1
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• pp.41-48
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• 2020

In this study, the design of anchorage zone for unbonded post-tensioned concrete beam with single tendons of ultimate strength 2400MPa was evaluated to verify that the KDS 14 20 60(2016) and KHBDC 2010 codes are applicable. The experimental results showed that the bursting force equation of current design codes underestimated bursting stress measured by test, because the KDS 14 20 60(2016) and KHBDC 2010 propose the location of the maximum bursting force 0.5h which is the half of the height of member regardless of stress contribution. Although the allowable bearing force calculated by current design codes was not satisfied the prestressing force, the cracks and failure in anchorage zone was not observed due to the strengthening effect of anchorage zone reinforcement.

• Computers and Concrete
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• v.5 no.6
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• pp.525-544
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• 2008

In this research, the self-centering effect in precast and prestressed reinforced concrete structures was investigated experimentally. The reinforced concrete beams and columns were precast and connected by post-tensioning tendons passing through the center of the beams as well as the panel zone of the connections. Three beam-to-interior-column connections were constructed to investigate parameters such as beam to column interfaces (steel on steel or plastic on plastic), energy dissipating devices (unbonded buckling restrained steel bars or steel angles) and the spacing of hoops in the panel zone. In addition to the self-centering effect, the shear strength in the panel zone of interior column connections was experimentally and theoretically evaluated, since the panel zone designed by current code provisions may not be conservative enough to resist the panel shear increased by the post-tensioning force.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.1
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• pp.3-10
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• 2018

This experimental investigation was conducted to observe the shear strengthening behavior of pre-damaged reinforced concrete (RC) beams strengthened with externally post-tensioning steel rods. A total of six simply supported beams - two control beams and four post-tensioned beams using external steel rods - were tested to failure in shear. The external steel rods of 18 mm or 28 mm diameter were respectively employed as post-tensioning material. The four post-tensioned beams have a V-shaped profile with a deviator (or saddle pin) located at mid-span, and the post-tensioning system increased the low load-carrying capacity and overcame a little bit of deflection caused by damage. Concretely, the load-carrying capacity and flexural stiffness were respectively increased by about 25~57% and 263~387% due to the post-tensioning when compared with the unstrengthened control beams.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.113-122
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• 2010

Corrosion of prestressing tendons and wire fractures in grouted post-tensioned prestressed concrete bridges have been considered as a serious safety problem. In bridge evaluation the condition of prestressing tendons should be inspected, and if corroded tendons are found, the loss of tendon area should be included when we calculate the ultimate strength. In the previous study, it was evaluated that continuous acoustic monitoring techniques could be considered as a reliable non-destructive method for detecting wire fractures of fully grouted post-tensioned prestressing tendons. In the present study, an experimental test was performed for detecting wire fractures of post-tensioned prestressing tendons which are prestressed lower than current design level. A 10 m prestressed concrete beam was fabricated, which included two tendons prestressed 66 percentage and 40 percentage of tensile strength, respectively. The corrosion of two tendons was induced by an accelerated corrosion equipment and the test beam was monitored by using seven acoustic sensors and a continuous acoustic monitoring system. From each prestressing tendon, two acoustic signals of wire fractures were successfully detected and source locations were estimated within 20 mm error. Based on the test results, it is considered that continuous acoustic monitoring techniques can be applied to detect low-prestressed wire fracture in fully grouted post-tensioned prestressed concrete beams.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.617-626
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• 2011

Seven post-tensioned lightweight concrete (LWC) beam specimens were tested under a symmetrical two-point top loading system. The parameters investigated were the amounts of mild longitudinal reinforcement and effective prestressing. The design compressive strength and dry density of the LWC tested were 30 MPa and 1,770 $kg/m^3$, respectively. Similar to post-tensioned normal weight concrete (NWC) beams, the crack propagation and stress increase of the unbonded tendons were significantly affected by the amounts of mild longitudinal reinforcement and effective prestressing. With the increase in the amounts of mild longitudinal reinforcement and effective prestressing, the serviceability and flexural capacity of the beams were enhanced whereas the stress increase in the unbonded tendons decreased. To control the crack width in post-tensioned LWC beams, a minimum amount of mild longitudinal reinforcement specified in ACI 318-08 provision is required. The flexural behavior of post-tensioned LWC beams and stress increase of the unbonded tendons could be rationally predicted by the proposed non-linear two-dimensional analysis. On the other hand, ACI 318-08 flexure provision was too conservative about the post-tensioned LWC beams.