• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.176-181
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• 2018

Concrete structures are degraded physically and chemically due to various reasons after construction. Because the deterioration of concrete structure reduces the service life, reasonable repair and maintenance techniques are needed. Recently, in order to efficiently repair concrete structures, many researches on hybrid repair materials having improved adhesion performance have been carried out actively. In this study, we developed a hybrid repair material containing rapid hardening cement, PVA powder, nylon fiber, and latex to improve adhesion and water-tightness of existing concrete. The compressive strength, drying shrinkage and the adhesion strength test were carried out to evaluate the performance of the repair material. In addition, the flexure bond performance was evaluated before and after repair. From the results, the bending strength was 110% ~ 150% in all specimens except for the specimen containing only the rapid hardening cement, and all the specimens behaved with the existing concrete in the crack pattern generated by the bending strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.1-8
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• 2018

The object of this paper is to find the characteristics of fire proof materials through an analytical method and to suggest a proper approach for fire-proof design of reinforced concrete beam strengthened with fiber reinforced polymer (FRP). Heating tests for fire-proof materials were conducted and the thermal conductivities and specific heats of them were simulated through finite element analyses. In addition, a finite element analysis on the beam specimen strengthened with FRP under high temperature, which was conducted by previous researchers, was performed and the analytical result was compared with test result. And then the compatibility of the analytical approach was evaluated. Finally, the heat resistance characteristic of RC beam strengthened with FRP was analyzed by the proposed analytical method and the strength decrease of the beam due to the high temperature was evaluated. From the comparison with analytical and test result, it was found that the heat transfer from outside to inside through the fire-proof materials can be suitably simulated by using the proposed analytical approach.

• Journal of the Society of Disaster Information
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• v.14 no.3
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• pp.343-351
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• 2018

Purpose: Recently, As the size of the structure increased, the necessity of reducing its weight was raised. To reduce weight In concrete structures, a hollow slab is proposed as an alternative for weight reduction effect. Method: It is difficult to construct the hollow body due to buoyancy, and the shear performance is insufficient due to the decreased cross section. Slabs were fabricated using unidirectional hollow bodies such as PVC pipes, and experiments were conducted about construction performance and structural performance. Results: The buoyancy preventive device has been improved the construction performance by preventing floating hollow body, it has been confirmed that it has adequate performance to be used as a hollow slab system because it has enough expected shear performance. Coclusion: Hollow ratio has a little connection with bending performance, but after the yielding load, it is necessary to consider the secondary stiffness of structure, and is is supposed that the decrease of shear performance with the increase of hollow core ratio can be complemented with shear reinforcement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.175-181
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• 2003

In this reseach, a seepage test is carried out for three kinds of soil using a upward seepage equipment. Reliability about the existing method of pipining investigation were verified making an estimate of the critical velocity, the critical hydraulic gradient, and hydraulic conductivity and so on. Also, sensitive analyses were carried out using Plaxis that is FEM Program about design factors of scour. The height of core had a big infulence on the hydraulic gradient of the embankment's lower part in the result of sensitive anaylsis. Also, second only to the height of core, and the slope of embankment, the width of crest had influence on scour. However, the change of hydraulic gradient in the effluent gateway had a little influence on the crest width of core. Using these results of sensitive analysis on designing, hydraulic gradient in the effluence gateway turned out to be reducing by altering design factors that change of sensitiveness is big, in case of the hydraulic gradient bigger than the standard hydraulic gradient.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.27-34
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• 2012

The objective of this study is to evaluate the stiffness of mortar-filled sleeve bar splice using estimation method of failure mode in the sleeve reinforcement splice. To attain this goal, we analyzed the test results of 261 actual-sized mortar-filled sleeve splice specimens. The study results showed that the estimation method of the failure mode in mortar-filled sleeve bar splice made an effective estimate of the stiffness in this bar splice with the exception of specimens with SD500 bars and smooth pipe sleeve. Especially, of the specimens with cast sleeve or uneven pipe sleeve in the range of reinforcement fracture using the estimation method of the failure mode in mortar-filled sleeve splice, specimens over 98% with SD400 bars and all specimens with SD500 bars had the stiffness capacity of higher than "A" class of AIJ code in monotonic loading. In addition, of the specimens in the range of reinforcement fracture using the estimation method of the failure mode in mortar-filled sleeve splice, all specimens with SD400 bars and SD500 bars had the stiffness capacity of higher than "A" class of AIJ code in cyclic loading.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.1-9
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• 2015

Recently Honam high-speed railroad line is constructed in southern part of Korea. This line is for next generation HST named HEMU-430X. But there is a limestone mine near this line and this mine will make a process to dig a passageway under the railway line. In this case, safety of railroad system and stability of mine are crucial problems on both sides. By measuring mine blasting vibration and calculating regression equation, effect of mine blasting to train running is investigated quantitatively. 0.5 kine (cm/sec) is applied as a management specification of vibration based on field measurement. In this study, changes of blasting patterns are suggested to control vibration of mine blasting. And the effect of train vibration to mine is also invesitigated by numerical analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.2
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• pp.40-48
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• 2016

To observe the rail-slab interaction in continuous welded railway(CWR) bridge when earthquake occurs, additional axial rail stresses and relative longitudinal displacements between rail and bridge deck were calculated with input of various load combinations and 3 different types of seismic loads to an analytical model. As results of analysis, it can be found that standard response spectrum proposed by Korea Rail(KR) network authority for earthquake design showed less additional axial rail stresses than allowable levels, but greater relative longitudinal displacement between rail and bridge deck, which means that adjustment of relative longitudinal displacement within a standard level is much more difficult than axial train stress. Additionally, if a large-scaled earthquake as occurred at Kobe, Japan comes up, then both of additional axial rail stress and relative displacement in rail-bridge deck may exceed allowable levels, which indicates to make proper design guides against sudden earthquake occurrence.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.102-109
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• 2010

This paper investigates the bond behavior of reinforced concrete beams having high-strength transverse reinforcement. A total of four reinforced concrete beams were tested in this study to estimate the bond capacity of the proposed U-shape reinforcement. The proposed U-shape reinforcement not only has a simple structure to install, but also can increase the bond capacity of reinforced concrete beams by controling bond cracks. This study follow the test method proposed by Ichinose to obtain the bond stress and the bond slip of the specimens. The main test parameters were the yield strength, ratio, and reinforcing types of transverse reinforcements. It was found that the proposed U-shape reinforcement was able to effectively improve the bond performance of reinforced concrete beams with high-strength transverse reinforcement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.4
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• pp.101-111
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• 2013

In this study, DEA (Data Envelopment Analysis) was carried out on the four bridges, which have the same extension (L=1,615m), in order to select the most superior, economical method of construction using the LCC concept of each bridge structure in the case of the Ulsan-Pohang double track railway which is scheduled to be constructed. DEA models were analyzed with the CCR model, which was designed for the evaluation of relative efficiency of each model. The initial construction costs, maintenance costs, indirect costs (user costs + indirect loss of social costs), and life cycle costs were used as input variables, and average duration was applied as the output variable. LCC was applied to calculate the input variables, and to get the costs of LCC, 100 years of period and 4.83% of real discount rate were applied, and the costs are classified into initial construction, maintenance, user, and indirect loss of social cost. The analysis results showed that the Method 2 and 3 were evaluated as the most efficient, and the other alternatives were evaluated as the following order; Method 1, the default, and Method 4.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.4
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• pp.38-47
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• 2013

For the joint connection of the precast steel grid composite decks, the prefabricated joint which is composed of concrete shear key and high-tension bolts was already proposed. In this study, for the purpose of increasing the bending stiffness and bending strength of the proposed prefabricated joint section details of the proposed joint are modified, and through experimental tests the bending performance, such as stiffness and strength of a modified joint, is compared with those of the proposed joint. Test and analysis results show that the shear cracks in the concrete shear key are clearly reduced by the strengthening of the shear key using shear studs and additional rebars. According to analysis results of the moment-curvature relationship, bending stiffness of the modified joint is about 47% greater than the stiffness of the proposed joint. Furthermore, the modified joint has about 32% greater bending strength than the proposed joint. Compared to specimens without the joint the modified joint has same or slightly higher bending strength, but about 37% lower bending stiffness.