• Journal of the Society of Disaster Information
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• v.15 no.1
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• pp.28-38
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• 2019

Purpose: The purpose of this study is to contribute to improvement of measurement management level of construction structure and technology development of monitoring sensor by presenting the detailed causes and improvement plans of construction monitoring sensor's decline in durability. Method: The causes and improvement plans of the durability degradation of the construction monitoring sensor were divided into the construction field and the electric, electronic field. The detailed status was reviewed. Results: In the field of construction, approval and inspection, inspection and testing, verification and calibration, and minimization of loss and damage ratio were reviewed. In the field of electric and electronics, sensor package and sealing, disconnection of stress concentration area, damage caused by lightning and corrosion were reviewed. Conclusion: It is expected that the durability of monitoring sensors applied to the construction site will become longer than the present status based on the study that analyzed causes and improvement plans of construction monitoring sensor's decline in durability in the field of construction and electric, electronic devices.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.535-541
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• 1997

It is proper that the load distribution and the actual stress of members is analyzed by field measurement in estimating to the behavior of truss railway bridges, but those procedures are very difficult. So, the studies for the deduction of the stress, using the indirect data which are able to get from the research and investigation without field measurement, are needed. In this study, to investigate quantitically the variation of the stress of members, the stresses are obtained from the simulation which is considered the the reduction of the section area and the stiffness due to the corrosion and the degree of the stress ratio and the distribution is calculated. As the results, the stress of truss members is almost lineary increased to the decreasing of the area and the lower chord is greatly affected. And the increasing of the stress is predicted by the superposition to the results of the amount of that in each members.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.104-109
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• 2010

Lap joint friction stir welding(LFSW) is an relatively new solid state joining process. A6061-T6 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. Test methods used in this paper, lock-in thermography, a phase difference between the defect area and the healthy area indicates the qualitative location and size of the defect. In this paper, the defects detected from the thermal image of mechanical properties for weld were evaluated and compared by the lock-in infrared thermography technique.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.57-64
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• 2006

The crack presented in concrete structures causes a structural defect, the durability decrease, and external damages etc. Therefore, it is necessary to improve durability through the effort to control the crack. Fluosilicic acid($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicates prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. Mix proportions for experiment were modulated at 0.45 of water to cement ratio and $0.0{\sim}2.0%$ of adding ratio of fluosilicate salt based inorganic compound. To evaluate correlation of concrete strength and adding ratio of fluosilicate salt based inorganic compound, the tests were performed about design strength(21, 24, 27 MPa) with 0.5% of adding ratio of fluosilicate salt based inorganic compound. Applications of fluosilicate salt based inorganic compound to reduce cracks resulted from plastic and drying shrinkage, to improve durability are presented in this paper. Durability was evaluated as neutralization, chloride ion penetration depth, freezing thawing resistant tests and weight loss according reinforcement corrosion. It is ascertained that the concrete added fluosilicate salt based inorganic compound showed m ability to reduce the total area and maximum crack width significantly as compared non-added concrete. In addition, the durability of concrete improved because of resistance to crack and watertightness by packing role of fluosilicate salt based inorganic compound obtained and pozzolanic reaction of soluble $SiO_2$ than non-added concrete.

• International Journal of Highway Engineering
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• v.7 no.4 s.26
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• pp.113-123
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• 2005

In this study, calcium chloride$(CaCl_2)$, sodium chloride (NaCl), organic acids-containing deicer(NS 40, NS 100), mixed deicier$(NaCl\;70%+CaCl_2\;30%,\;NS\;40\;70%+CaCl_2\;30%,\;NaCl\;70%+NS\;40\;30%,\;NS\;40\;70%+NaCl\;30%)$ is investigated based on the laboratory test for deicing performance, freez-thaw resistance of concrete, and corrosion rate of metal. Test items for deicing performance were ice melting and ice penetration, freezing point depressions and eutectic point, pH, thermal properties for selected deicing chemicals as well as their compatibility with concrete and metal were experimentally investigated. As a test results, in case of the use chloride-containing deicier in area that concrete structures has subjected to freez-thaw reaction in winter season, it showed that mixed deicing chemicals with optimum ratio has desirable method than use one deicing chemicals when is consider to deicing performance and effects, corrosion of steel materials, and freez-thaw resistance of concrete. When use various deicing chemicals mixed, NS40(70%)+calcium chloride(30%) showed the best effective method.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.491-497
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• 2014

The corrosion of steel reinforcement in reinforced concrete bridge decks significantly affects the degradation of the capacity. Due to the advantageous characteristics such as high tensile strength and non-corrosive property, fiber reinforced polymer (FRP) has been gathering much interest from designers and engineers for possible usage as a alternative reinforcement for a steel reinforcing bar. However, its application has not been widespread, because there data for short- and long-term performance data of FRP reinforced concrete members are insufficient. In this paper, seven full-scale decks with dimensions of $4000{\times}3000{\times}240mm$ were prepared and tested to failure in the laboratory. The test parameter was the bottom reinforcement ratio in transverse direction. The decks were subjected to various levels of concentrated cyclic load with a contact area of $577{\times}231mm$ to simulate the vehicle loading of DB-24 truck wheel loads acting on the center span of the deck. It was observed that the glass FRP (GFRP) reinforced deck on a restraint girder is strongly effected to the level of the applied load rather than the bottom reinforcement ratio. The study results showed that the maximum load less than 58% of the maximum static load can be applied to the deck to resist a fatigue load of 2 million cycles. The fatigue life of the GFRP decks from this study showed the lower and higher fatigue performance than that of ordinary steel and CFRP rebar reinforced concrete deck. respectively.

• Journal of Korean Association for Spatial Structures
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• v.9 no.3
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• pp.93-100
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• 2009

As interest in latest cultural heritance is increased, an importance about conservation of dilapidated cultural building asset is risen. Most of cultural building asset used wood by main material and conservation repair about corrosion and damage by deterioration of these cultural building asset considers cultural value of member and the basis principle is the archetype maintenance. Accordingly, conservation processing method that use synthetic is embossed. This paper experimented with reinforcement sectional area ratio, direction of section, length, strength of synthetic resins as variable and manufactures total 14 specimens as experimental study about compression reinforcement performance of circular section wood that strengthen by synthetic resins. The result of this paper has shown that adequate strengthen is more efficient than new member and the most important authenticity in strengthen and repair of cultural heritance can be ensured.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.1-9
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• 2022

De -icing salts have been used commonly in areas where snow or ice is a seasonal safety hazard for roadway, however, the salts is one of main causes on serious deterioration of road infrastructures in crowded urban city like Seoul. In order to establish maintenance strategy of road infrastructures under de-icing salts laden environment, it is necessary to examine environmental characteristics and its response to the existing facilities. The purpose of this study is to evaluate the deterioration environment of road infrastructures. Additional purpose is to develop a design model and details for durability design of infrastructures under de-icing salts laden environment, considering mainly a build-up rate of surface chlorides. Concentration of external chloride solution and surface chloride content were calculated at the level of average de-icing salts for 5 years, ratio of auxiliary road of 17.5 to 30%, and effective exposure area to snow 50 to 80%. The chloride build-up rate was 0.073 ~ 0.077% / year and the maximum surface chloride content was calculated to be 2.2 ~ 2.31% by concrete wt. This study is expected to be used for establishing integrated strategy of road infrastructures, such as predicting chloride profiles or degree of chemical corrosion to exposure concrete.

• Resources Recycling
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• v.16 no.6
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• pp.3-9
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• 2007

Although the ferrous material was separated by the magnetic separation before the incineration process, the municipal solid waste incineration bottom ash generated during incinerator in metropolitan area consists of many iron products which account for about $3{\sim}11%$ as well as ceramics and glasses. The formation of $NiFe_2O_4$ and $FeCr_2O_4$ with a $Fe_3O_4-Fe_2O_3$ (similar to pure Fe) on the surface of iron product was found during air-annealing in the incinerator at $1000^{\circ}C$, because Ni and Cr has a chemical attraction about iron is using to coat with Ni and Cr metals for poish or to prevent corrosion. Therefore, Fe-Ni Cr oxide can be formed on durface of the iron product and it can be separated from bottom ash through the magnetic separation. So, in this study, the separation ratio of heavy metals as magnetic separation and mineralogical formation of Fe-ion(heavy metal) in ferrous metals corroded were investigated. As the result, the separation ratio of Ni and Cr based on particle sizes accounted for about $45{\sim}50%$, and Cu and Pb accounted for below 20%. Also, the leaching concentration of Ni and Cr in bottom ash separated by magnetic separation was lower than that in fresh bottom ash.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.9
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• pp.768-773
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• 2016

Engine valve seat and face, which are the important factors affecting engine performance, are required to have wear, heat and corrosion resistance. In order to produce surface layer with these characteristics, PTA(plasma transferred arc) surfacing procedure is generally employed, but problems, such as large HAZ and high dilution etc., frequently occurr. Laser cladding, which overcomes the drawbacks of conventional technologies, can be employed to create a superior clad layer with low dilution, small heat affected zone, and minimal distortion. However, in case cladding is to be applied to a large area, it is necessary to overlap 1 pass clad layer because of limited clad layer width. Two criteria for the overlapping ratio-beam size and clad layer width-have been considered thus far. Upon inspection of multi pass clads, produced by different overlapping criteria, it was observed that the greater the increase in overlapping ratio, the greater was the decrease in clad layer width and increase in clad layer height regardless of the criterion used. However, a multi pass clad overlapped by the beam size criterion demonstrated a higher hardness value than a clad overlapped by the clad layer width owing to decreasing dilution of the substrate. In conclusion, the beam size was defined as the criterion for the overlapping, because the clad layer width increased or decreased depending upon process parameters.