• Journal of the Korea institute for structural maintenance and inspection
• /
• v.16 no.4
• /
• pp.52-59
• /
• 2012

An analytical model is presented to predict the static behavior of the long-span prestressed concrete bridge deck(the long-span PSC deck). The finite element analysis is performed and the results are compared with that of the previous experimental test. The load-deflection relationship curves by FEM are in good agreement with the results reported in the previous study. The failure mode of all test specimens is predicted by the punching shear in this study. It is also observed in the previous experimental test. The main objective of this paper is presenting supportive method to predict static behavior of the long-span PSC deck slab. It is not simulating the punching shear behavior graphically.

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

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.341-344
• /
• 2008

In this paper, the effect of flame cutting order of tendons on the concrete stress was investigated experimentally. For this, the three slab specimens with 14 tendons were cast and tested. During the detensioning, the longitudinal and transversal strain were measured. Test results showed that the measured strains of transversal stirrups were varied by the cutting order.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.5A
• /
• pp.747-756
• /
• 2008

The purpose of this paper is to investigate the effect of the important parameters on the transfer length during the dynamic flame cutting of tendon experimentally. The considered parameters were strand diameter, concrete cover thickness, stirrup, debonding strand and release method. Ten pretensioned concete beam specimens were cast and tested. Time history curves for the axial strain of tendon were measured by electrical resistance strain gauges mounted on the strands. Experimental results indicated that large dynamic shock effects occurred near cut-end during the sudden release. The prestressing forces are dependent on the parameters above considered. The ratio of residual prestressing forces of 12.7 mm strands is greater than 15.2 mm strands. Using debonding strand and gradual release are more efficient for applying prestressing forces.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.41-42
• /
• 2009

The purpose of this paper is to inspect a structural performance for the composite wall pile through static bending test. In result, all specimen came to failure in 1.8 times cracking load and the drift of the neutral axis on a load increasing occurred.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.11 no.3 s.55
• /
• pp.23-31
• /
• 2007

Fast bridge construction has been increasingly needed according to the changed construction environment. This paper deals with quasi-static tests on precast piers for bridge substructures. One of the most crucial aspect of the design of precast prestressed concrete bridge piers is the seismic performance. Seven precast pier elements were fabricated. The amount of prestressing bars, the prestressing force, and the location and number of the joint between segments were the main test parameters. Test results showed that the introduced axial prestress made the restoration of the deformation under small lateral displacement and minor damage. However, there was no effect of the prestress when the plastic hinge region was damaged severely due to large lateral displacement. Judging from the observed damage, the design of the joints in precast piers should be done for the first joint between the foundation and the pier segment. The amount of the necessary prestressing steel may be designed to satisfy the P-M diagram according to the service loads, not by having the same steel ratio as normal RC bridge piers. In order to satisfy the current required displacement ductility, it is necessary to have the same amount of the transverse reinforcements as RC piers. As the steel ratio increases, the energy absorption capacity increases. The number of joints showed a little influence on the energy absorption capacity.

• Journal of the Korea Concrete Institute
• /
• v.27 no.4
• /
• pp.399-409
• /
• 2015

Recently, the use of composite construction method using precast (PC) and cast-in-place (CIP) concrete is increased in modular construction. For PC members, pre-tensioning is used to improve efficiency of the structural performance. However, current design codes do not clearly define shear strength of prestressed PC-CIP composite members. In this study, 22 specimens were tested to evaluate shear strength of prestressed composite members with vertical shear reinforcement. The test variables were the area ratio of high-strength (60 MPa) to low-strength concrete (24 MPa), prestressing force of strands, shear span-to-depth ratio(a/d), and vertical shear reinforcement ratio. The test results showed the prestressing force did not completely restrain diagonal cracking of non-prestressed concrete in the web. Thus, the effect of prestress force was not insignificant in the effect for monolithic beams. The vertical shear strength and horizontal shear strength of the composite beams were compared with the strength predictions of KCI design method.

• Journal of the Korea Concrete Institute
• /
• v.21 no.2
• /
• pp.159-168
• /
• 2009

In this study, strength, stiffness and confinement effect with stress-strain and stress-volumetric strain curves for improved uniaxial compressive behavior of RC circular columns laterally confined with prestressing aramid fiber strap were experimentally investigated. The test variables were the specimens with or without axial reinforcing bar and the number and spacing of strap, prestressing level, the types of reinforcing fiber (CFS, GFS). As a result, the failure type of the columns was very stable and strength increase rate was about 73% comparison with the general RC columns. Moreover, the strain increase rate is very small and the axial displacement confinement effect was very effective compared with existry methods (CFS, GFS), the initial and final lateral confinement effect was excellent.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.3C
• /
• pp.91-96
• /
• 2009

The purpose of this study was to investigate a method for the strength enhancement of wale in temporary retaining structures. Tests on the wale structures strengthened with carbon fibre reinforced plastic (CFRP) strips and prestressed with seven wire strands were conducted. From this test, it is found that the flexural stiffness and strength of the wales strengthened with CFRP strips and seven wire strands were significantly improved compared to the unstrengthened one. The ultimate tensile strains of attached CFRP strips on the steel beam were in the range of 8,000 and $11,000{\mu}{\epsilon}$, and it is noticed that the bonding ability with steel and CFRP strips is good. In this paper, a new method for enhancing the strength of wale in retaining structures is suggested.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.67-76
• /
• 2020

This paper reports an experimental study to evaluate the flexural behavior of concrete beams reinforced using Fe based shape memory alloy (Fe-SMA) bars. For the experiment, a concrete beam of 200mm×300mm×2,200mm was produced, and a 4% pre-strained Fe-SMA bar was used as a tensile reinforcement. As experimental variables, type of tensile reinforcement (SD400, Fe-SMA), reinforcement ratio (0.2, 0.39, 0.59, 0.78), activation of Fe-SMA (activation, non-activation), and joint method of Fe-SMA bar (Continuous, welding, coupler) were considered. The electric resistance heating method was used to activate the Fe-SMA bar, and a current of 5A/㎟ was supplied until the specimen reached 160℃. After the upward displacement of the specimen due to the camber effect was stabilized, a three-point flexural loading experiment was performed using an actuator of 2,000 kN capacity. As a result of the experiment, it was found that the upward displacement occurred due to the camber effect as the Fe-SMA bar was activated. The specimen that activated the Fe-SMA bar had an initial crack at a higher load than the specimen that did not activate it. However, as with general prestressed concrete, the effect of the prestress by Fe-SMA activation on the ultimate state of the beam was insignificant.