• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.227-238
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• 2003

Due to deterioration of bridge, usually be using the external prestressing method among repair reinforcement method. But, there is much to be desired about a detailed account, almost it has analysed by cambers of girders, deflections of middle span and upper, bottom stresses of girders. Also, it is not examined closely that effect of internal prestress by external prestressing. The purpose of this study is confirmed the effect of internal tendons by external prestressing, estimation of additional external prestressing force and look for exact external prestressing force.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.2
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• pp.111-120
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• 2001

This paper aims at estimating instantaneous prestress losses by measuring the actual prestress forces in prestressed concrete (PSC) box girder bridges. Measurement were taken to study initial prestress losses such as friction losses and slip losses. A new strain gauge system was developed to measure strains in internal tendons. The system was installed on a total of 20 tendons in a PSC box girder bridges. The variation of prestress forces were monitored during prestressing tendon and after prestress transfer. The prestress losses are also calculated including friction losses and slip losses. The measured data were compared with the theoretical values. The result shows that the measured prestress forces agree well with the theoretical values. It is shown that prestress force of each strand in the same tendon is a bit different. This study also shows that prestress losses of continuity tendons during prestress transfer are significantly different each other, which results from the variety of buttress location and tendon profile. The present study provides realistic information on the estimation of actual prestress forces and losses in PSC box girder bridges.

• Structural Engineering and Mechanics
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• v.37 no.3
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• pp.309-320
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• 2011

As a new type of large-span space structure, suspendome is composited of the upper single-layer reticulated shell and the lower cable-strut system. It has better mechanical properties compared to single-layer reticulated shell, and the overall stiffness of suspendome structure increases greatly due to the prestress of cable. Consequently, it can cross a larger span reasonably, economically and grandly with high rigidity, good stability and simple construction. For a better assessment of the advantages of mechanical characteristic of suspendome quantitatively, the static behavior of Kiewitt6 suspendome was studied by using finite element method, and ADINA was the software application to implement the analysis. By studying a certain suspendome, the internal forces, deformation and support constrained forces of the structure were obtained in this paper. Furthermore, the influences of parameters including prestress, stay bar length, cross-sectional area and rise-to-span ratio were also discussed. The results show that the increase of prestress and vertical stay bar length can improve the stiffness of suspendome; Cross-sectional area has nearly no impact on the static behavior, and the rise-to-span ratio is the most sensitive parameter.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.5
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• pp.259-266
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• 2018

This is the study for developing the hetero-core optical fiber sensors which are purpose to measure the prestress of PSC bridges during the life cycle period. The goal of this study is to improve the resolution of hetero-core sensors. As a result of the test, it is possible to measure the displacement in $2{\mu}m$ increments. In other words, if the length of the sensor module is 30cm, it is possible to measure the prestress variations in 0.2MPa increments at specified compressive strength of concrete(fck) of 40MPa by Hook's Law. So it can be useful for development of a sensor module measuring internal prestress measurement.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.4
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• pp.71-82
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• 1999

An axisymmetric shell element which includes the effects of the meridional and circumferential cable prestresses is developed. The fluid-structure interaction is expressed as added mass effect which is in proportion to the acceleration of the structure in interface surface. The added mass is obtained by using finite element method under the assumption that the fluid is invicid, incompressible and irrotational. It is coded for personal computer by the maximum use of axisymmetic properties and the dynamic analysis are performed under seismic exitations. A ring element makes the characteristics of the axisymmetric shell to be fully utilized. The elgenvalue solutons under the initial prestresses and the internal fluid are well agreed with the exact solutions and references by using under 20 elements. The eigenvalues are decreased along the increasing the height of internal fluid and these effects are dominant under the lower wave numbers. The results of the seismic analysis show that the radial deflection under the meridional prestress is a little larger than that under the circumferential prestress.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.591-596
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• 2001

In case of continuous steel box-girder bridges, the magnitude of the longitudinal tensile stress on concrete in internal support is larger than the tensile strength of concrete. In this paper, the parametric study was performed to present the effective magnitude of the longitudinal prestress for reducing the longitudinal tensile stress to decrease under the tensile strength of concrete. The parametric study is conducted with changing the steel box-girder section and the span length of bridge. Three dimensional finite element analyses are conducted with ABAQUS program. The behavior of the steel box-girder bridge with prestress is investigated through experimental works on a analogous steel box-girder bridge model, and their results are compared with those of analytical studies.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.688-693
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• 2007

Nowadays various studies related with superstructure of bridges are developed and they pursuit more effective section of bridges superstructure, material and economical application of composite materials. CFT structure(Concrete Filled Steel Tubular Structure) is developed type of composite structure that concrete is filled with steel box, and the deformation of the member, stiffness and internal force will be improved by confinement effect of steel box and concrete. This paper introduces new type of girder, CFTA girder( Concrete- Filled and Tied Steel Tubular Arch Girder) which is combined with traditional CFT structure,arch effect and prestress through carrying out the structural analysis by computer programs. The computer programs which is used are ABAQCS and MIDAS, and the 12.2m girder which is applied same load and prestresses is analyzed and compared the results respectively.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.43-63
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• 2023

With the concentration of the population in the city center and the saturation of the structures on the ground, the development of the underground structures becomes important and the construction of an adjoining tunnel that can reduce the overall problems is respected. In addition, it is necessary to apply the reinforcement construction method for the pillar part of the adjacent tunnel that can secure stability, economy and workability of the site. In this study, the tunnel pillar reinforcement method using prestress and grouting was reviewed. There are various reinforcement methods that can compensate for the problems of the side tunnel, but as the tunnel pillar construction method using prestress and grouting is judged to be excellent in field applicability, stability and economic feasibility, theoretical and numerical analysis of the actual behavior mechanism are conducted. Numerical analysis is divided into PC stranded wire + steel pipe reinforcement grouting + prestress (Case 1), pillar part tie bolt reinforcement (Case 2), pillar part non-reinforcement (Case 3) under the same ground conditions, and the maximum value of the celling displacement, internal displacement, and member force, the stability was confirmed. Through numerical analysis, it was confirmed that Case 1 which reinforced the PC stranded wire, was the best construction method and if it is verified and supplemented through field experiments later, it will be possible to derive superior results in terms of displacement control and member force than the currently applied reinforcement method was judged.

• Journal of Korean Society of Steel Construction
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• v.22 no.1
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• pp.21-31
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• 2010

In this study, a technique that uses wireless impedance sensor nodes is proposed to monitor tensile force of structural cable. To achieve this goal, the following approaches were implemented. First, a wireless impedance sensor node was designed for automated and cost-efficient prestress-loss monitoring. Second, an impedance-based algorithm was embedded in the wireless impedance sensor node for autonomous structural health monitoring of structural cables. Third, a tensile force monitoring technique that uses an interface plate for structural cables was proposed to overcome the limitations of the wireless impedance sensor node such as its narrow-band measurable frequency ranges. Finally, the applicability of the wireless impedance sensor node and the technique that uses the interface washer were evaluated in a lab-scaled prestressed concrete (PSC) girder model with internal and external tendons for which several prestress-loss scenarios were experimentally monitored with the wireless impedance sensor nodes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.101-110
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• 2014

Expansion agent is a very effective admixture for prevention of cracking due to autogenous/drying shrinkage and this can induce internal chemical prestress to embedded reinforcement. In this paper, tension-softening and hardening in cement mortar with steel and CSA expansion agent are experimentally evaluated. Cement mortar with steel reinforcement is prepared and tensile strength test is performed for evaluation of cracking and tensile behavior. In spite of slightly reduced strength and elasticity in CSA mortar, significantly increased tension-hardening behavior is evaluated in CSA mortar with induced chemical prestress. Furthermore previous tension softening models are compared with the test results and improvement are proposed.