• Progress in Superconductivity and Cryogenics
• /
• v.3 no.1
• /
• pp.6-10
• /
• 2001

Stress/stram dependencies of the critical current $I_c$ in AgMgNi sheathed multifilamentary Bi(2212) superconducting tapes were evaluated at 77K, 0T. The external reinforcement was accomplished by soldering Ag-Mg tapes to sin91e side or both sides of the sample. With the external reinforcement. the strength of tapes increased but $I_c$, decreased The $I_c$, degradation characteristic according to the external reinforcement was improved markedly in terms of the stress although it appeared less rectal.table on the basis of the strain. Effects of external reinforcement were discussed in a viewpoint of monitoring sensitivity of cracking in superconducting filaments by considering n-value representing the transport behavior of the current. It is closely associated with the location of them relative to the voltage-monitoring region in the tape.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2001.02a
• /
• pp.17-20
• /
• 2001

Stress/strain dependencies of the critical current I$_{c}$ in AgMgNi sheathed multifilamentary Bi(2212) superconducting tapes were evaluated at 77K. The external reinforcement was accomplished by soldering Ag-Mg tapes to single side or both sides of the sample. With the external reinforcement, the strength of tapes increased but I$_{c}$ decreased. The I$_{c}$ degradation characteristic according to the external reinforcement was improved markedly in terms of the stress although it appeared less remarkable on the basis of the strain. Effects of external reinforcement were discussed in a viewpoint of monitoring sensitivity of cracking in superconducting filaments by considering n-value representing the transport behavior of the current, which is closely associated with the location of them relative to the voltage-monitoring region in the tape. tape.

• Structural Engineering and Mechanics
• /
• v.83 no.6
• /
• pp.745-756
• /
• 2022

This study aims to determine the cause of the load resistance loss in storage racks that can be attributed to external forces such as earthquakes and to improve safety by developing reinforcement systems that can prevent load resistance loss. To this end, a static cyclic loading test was performed on pallet racks commonly used in logistics warehouses. The test results indicated that a pallet rack exposed to an external force loses more than 50% of its load resistance owing to the damage caused to column-beam joints. Three reinforcement systems were developed for preventing load resistance loss in storage racks exposed to an external force and for performing differentiated target functions: column reinforcement device, seismic damper, and viscoelastic damper. Shake table testing was performed to evaluate the earthquake response and verify the performance of these reinforcement systems. The results confirmed that, the maximum displacement, which causes the loss of load resistance and the permanent deformation of racks under external force, is reduced using the developed reinforcement devices. Thus, the appropriate selection of the developed reinforcement devices by users can help secure the safety of the storage racks.

• Progress in Superconductivity and Cryogenics
• /
• v.5 no.3
• /
• pp.15-19
• /
• 2003

For the purpose of standardization of the critical current measurement, it is meaningful to describe how $I_{c}$ will behave as the stress/strain level changes. In this study, strain dependencies of the critical current $I_{c}$ in Ag-alloy sheathed multifilamentary Bi(2212) and Bi(2223) superconducting tapes were evaluated at 77K, 0T. The external reinforcement was accomplished by soldering AgMgNi alloy tapes onto single or both sides of the sample. With the external reinforcement to the Bi(2212) tape, the strength of the tapes increased but the critical current at the strain free state, $I_{c0}$ decreased in some cases. The strain for onset of the $I_{c}$ degradation, $\varepsilon$$_{\irr}$, increased with an increase of the reinforcing volume and then saturated to a certain value. The effect of external reinforcement on the degradation of $I_{c}$ due to the bending strain in the Bi(2223) tape was also examined. Contrary to the expectation, it showed a significant $I_{c}$ degradation even at a small strain of 0.4 %. The observations of damage morphologies gave a good explanation to the $I_{c}$ behavior.c/ behavior.r.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.11
• /
• pp.2866-2874
• /
• 2000

This paper is concerned with the optimum design for external reinforcement of a nuclear reactor pressure vessel(RPV) in a severe accident. During the severe reactor accident of molten core, the temperature and the pressure in the nuclear reactor rise to a certain level depending on the initial and subsequent condition of a severs accident. The reis of the temperature and the internal pressure cause deterioration of the load carrying capacity and could cause failure of the RPV lower head. The deterioration of failure can be mitigated by the external cooling or the reinforcement of the lower head with additional structures. While the external cooling forces the temperature of an RPV to drop to the desired level, the reinforcement of the lower head can attain both the increase of the load carrying capacity and the temperature drop. The reinforcement of the lower head can be optimized to have the maximum effect on the collapse pressure and the temperature at the inner wall. Optimization results are compared to both the result without the reinforcement and the result with the designated reinforcement.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.1
• /
• pp.1-6
• /
• 2021

Concrete structures gradually age due to deterioration of materials or excess loads and environmental factors, and their performance decreases, affecting the usability and safety of structures. Although external tension construction methods are widely used among the reinforcement methods of old bridges, it is insufficient to identify the effects and effects of reinforcement depending on the level of aging. Therefore, in this study, a four-point loading experiment was conducted on the subject with the non-reinforced and external tensioning method to confirm the reinforcement effect of the external tensioning method, assuming the aging of the structure as a reduction in the compressive strength and tensile reinforcement of concrete, to analyze the behavior of the reinforcement and confirm the reinforcement effect. As a result of the experiment, it was difficult to identify the amount of reinforcement in the extreme condition due to early elimination of the anchorage. Therefore, compliance with the regulations on anchor bolts is required when applying the external tension reinforcement method. Crack load and yield load increased depending on whether external tension was reinforced, but before the crack, the stiffness before and after reinforcement was similar, making it difficult to confirm the reinforcement effect.

• Journal of the Korean Society for Railway
• /
• v.9 no.2 s.33
• /
• pp.151-159
• /
• 2006

It analyzed the mechanical behaviors of non-ballasted railway bridge (steel plate girder type) with ballast reinforced on the finite element analysis, field test and laboratory test far the static and dynamic responses. The major objective of this study is to investigate the effects and application of reinforcement for steel plate girder railway bridge by the external post-tensioning method. The reinforcement of non-ballast railway bridge had obviously stable dynamic behaviors due to the additional dead force which was ballast. But in case of static behaviors, static displacements and stresses had increased nearly the allowable values. Therefore we analyzed the mechanical behaviors of non-ballasted railway bridge with ballast reinforced and external post-tensioning reinforced on the finite element analysis and laboratory test for the static and dynamic behavior. As a result, the reinforcement of ballasted railway bridge the external post-tensioning method are obviously effective for the additional dead force which is ballast. The analytical and experimental study are carried out to investigate the post-tension force decrease bending behavior and deflection in composite bridge for serviceability. The servicing railway bridge with ballast reinforced has need of the reasonable reinforcement measures which could be reducing the effect of additional dead load that degradation phenomenon of structure by an unusual. stresses and a drop durability.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.1003-1006
• /
• 2003

In recent years, FRP plates have been studied for flexural reinforcement of RC structures due to easy installation and good Quality control. This study presents experimental field test results for the effectiveness of flexural reinforcement of the RC slab using external prestressing with thin CFRP strips made by the pultrusion process. It was demonstrated that flexural strength was considerably increased with relatively easy installation when compared to the other methods used for the composite reinforcement.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.1034-1039
• /
• 2004

The major objective of this study is to investigate the effects and application of reinforcement for steel plate girder railway bridge by the external prestressing method. It analyzed the mechanical behaviors of non-ballasted railway bridge with ballast reinforced and external post-tensioning reinforced on the finite clement analysis for the static and dynamic behavior. As a result, the reinforcement of ballasted railway bridge the external prestressing method are obviously effective for the additional dead force which is ballast. The analytical study are carried out to investigate the post-tension force decrease bending behavior and deflection in composite bridge for serviceability. To develop two type FEM model which reflect well the post-tension force transverse distribution behavior of servicing bridge. With the comparing the results of railway bridge with ballast which carried out before the post-tensioning with the results of railway bridge with ballast which carried out after post-tensioning, It is investigated that the additional dead load decrease effect and bending behavior of servicing bridge is effect by the post-tensioning. The reinforcement by using the external tendon can be reducing that structure of a degradation phenomenon by unusual stresses due to additional dead load and other problems.

• Journal of the Korean Society for Railway
• /
• v.10 no.2 s.39
• /
• pp.186-194
• /
• 2007

This study was performed to compare the load-carrying capacities of the reinforced concrete structure between the carbon fiber adhesion reinforcement method and the external post-tensioning method and further estimate the effective stress of the reinforced material by analyzing the experimental reinforcing effect of each method and the behavior resulting from each method. As a result, it was found out that the effective stress of the carbon fiber reinforcement according to the carbon fiber adhesion reinforcement method had an unexpected value, and also, bearing of the stress was found to be far from sharing thereof. That is to say, while the carbon fiber was bearing the whole stress to some limits, it got to be momentarily ruptured as soon as it went beyond such limits. On the other hand, the external post-tensioning method has the advantage of inducing an initial effective stress by introducing a strain, and thus, it was found that behavior or bearing of the stress was also found to be a solid behavior of the steel wire. This method was also found to be more efficient and excellent than the carbon fiber adhesion reinforcement method in the reinforcing effect or securing the effective stress. Accordingly, we were to discuss the effective stress as comparatively examined, focusing on deriving of the more enhanced reinforcing effect on the basis of the experiment to which the field characteristic is added.