• Journal of the Society of Disaster Information
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• v.19 no.1
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• pp.138-145
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• 2023

Purpose: In accordance with the increase in the number of buildings repaired and reinforced following deterioration from when a fire occurs in a previously reinforced building, the impact on the structure after the fire is analyzed to establish standards for repair and reinforcement measures. Method: After curing for 28 days, the process was to measure the compressive strength and induce destruction through a compressor, repair and reinforce it with epoxy, and conduct a re-compressive strength test on some specimens after curing for 3 days to understand the degree of strength restoration. The rest of the repaired and reinforced specimens as well as the unrepaired and unreinforced specimens were then put into an oven and heated according to the temporal and temperate conditions listed below, and then the compressive strength was tested to estimate the impact of fire. Result: After reinforcing the yielded specimen with epoxy, the process was to then put it in an oven and heat it at different temperatures over time. It was found that there was a decrease in the strength of the reinforcement more than that of the actual specimen. Conclusion: Based on this, it was found that a building repaired and reinforced with epoxy resin is actually more dangerous than a general unrepaired building when it is damaged by fire, and thus, that it must be prepared for fire vulnerabilities.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.220-227
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• 2021

PCT (Power Cable Tunnel) and UT (Utility Tunnel), which are non-transport underground infrastructures, are mostly RC (Reinforced Concrete) structures, and their durability decreases due to the deterioration caused by carbonation over time. In particular, since the rate of carbonation varies by use and region, a predictive model based on actual carbonation data is required for individual maintenance. In this study, a carbonation prediction model was developed for non-transport underground infrastructures, such as PCT and UT. A carbonation prediction model was developed using multiple regression analysis and deep neural network techniques based on the actual data obtained from a safety inspection. The structures, region, measurement location, construction method, measurement member, and concrete strength were selected as independent variables to determine the dependent variable carbonation rate coefficient in multiple regression analysis. The adjusted coefficient of determination (Ra2) of the multiple regression model was found to be 0.67. The coefficient of determination (R2) of the model for predicting the carbonation of non-transport underground infrastructures using a deep neural network was 0.82, which was superior to the comparative prediction model. These results are expected to help determine the optimal timing for repair on carbonation and preventive maintenance methodology for PCT and UT.

• Journal of Korean Society of Steel Construction
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• v.30 no.2
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• pp.105-114
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• 2018

The use of post installed anchors with bond type has lately been increasing when it is necessary to repair, reinforce, or remodel structures. This method provides flexibility and simplicity for construction of structural members that require adhering or fixing. Meanwhile, strength evaluation of anchors with expansion type among post-installed anchors systems has nearly reached setting up stage like design code through continual experimental studies for the last ten years, but analyses or experimental studies on anchor system with bond type are not yet sufficient. Accordingly, the designers and builders of korea depend on foreign design codes since there are no exact domestic design code they could credit. In this study, the objectives are investigating the effects on pull-out strength of resin anchors embedded into plain concrete by pull-out experiment of resin anchors with variables such as anchor diameter, anchor interval, embedment depth and edge distance.

• International journal of steel structures
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• v.18 no.4
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• pp.1336-1349
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• 2018

Generally, a precast prestressed concrete (PSC) beam is used as girders for short-to-medium span (less than 30 m) bridges due to the advantages of simple design and construction, reduction of construction budget, maintenance convenience. In order to increase the span length beyond 50 m of precast PSC girder, PSC hollow box girder with unbonded prestressed H-type steel beam placed at the compressive region is proposed. The unbonded compressive prestressing in the H-type steel beams in the girder is made to recover plastic deflection of PSC girder when the pre-stressing is released. Also, the H-steel beams allow minimization of depth-to-length ratio of the girder by reducing the compressive region of the cross-section, thereby reducing the weight of the girder. A quasi-static 3-point bending test with 4 different loading steps is performed to verify safety and plastic deflection recovery of the girder. The experimental results showed that the maximum applied load exceeded the maximum design load and most of the plastic deflection was recovered when the compressive prestressing of H-type steel beams is released. Also using prestressed H-type steel as compression reinforcements in the upper part of cross section, repair and restoration difficulty and cost of PSC girders should be significantly reduced. The study result and analysis are discussed in detail in the paper.

• Journal of Korean Society of Forest Science
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• v.102 no.1
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• pp.90-96
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• 2013

This study was conducted to investigate a stability trend within 6 above average and 4 blow average erosion control dams, which were selected by The Korean Association of Soil and Water Conservation and were built in 1990s in Gyeonggi and Gangwon Province. The study was aimed to measure rebound hardness of upstream face, flood way and downstream face from those dams selected by using 'Concrete Test Hammer'. The main purposes of the study are selection of compression strength prediction equation and scope of wavelength, which successfully demonstrate non-destructive test results for erosion control dams. There is an opportunity to increase disaster prevention ability when stability vulnerability of concrete erosion control dam is detected in a timely manner. Results of the compression strength investigation express that there is a consistency with visual inspection of stability that has been processed by The Korean Association of Soil and Water Conservation. We concluded that a prediction equation, which was developed by Architectural Institute of Japan (AIJ), shows highest suitability in Korean erosion control dams when stability investigation is performed. The detailed criteria for the test result are 'stable', 'detail inspection required' and 'poor' for over 300 $kgf/cm^2$, 250~300 $kgf/cm^2$ and below 250 $kgf/cm^2$ respectively. Standards for stability of Korean erosion control dam and a compression strength prediction equation (that corresponds to the standards of the stability) should be established on the basis of chronological data of erosion control dam compression strength. Systematical approach for stability inspection that carries out remodeling or repair when problem on erosion control structures are detected through visual inspection and simple stability test, is necessary for the future disaster prevention.