• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.129-139
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• 2008

Due to uncertainty of numerous variables in durability model, a probalistic approach is increasing. Monte Carlo simulation (Level III method) is an easily accessible method, but requires a lot of repeated operations. This paper evaluated the effectiveness of First Order Second Moment method (Level II method), which is more convenient and time saving method than MCS, to predict the corrosion initiation in harbor concrete structure. Mean Value First Order Second Moment method (MV FOSM) and Advanced First Order Second Moment method (AFOSM) are applied to the error function solution of Fick's second law modeling chloride diffusion. Reliability index and failure probability based on MV FOSM and AFOSM are compared with the results by MCS. The comparison showed that AFOSM and MCS predict the similar reliability index and MV FOSM underestimates the probability of corrosion initiation by chloride attack. Also, the sensitivity of variables in durability model to corrosion initiation probability was evaluated on the basis of AFOSM. The results showed that AFOSM is a simple and efficient method to estimate the probability of corrosion initiation in harbor structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.214-224
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• 2008

Member force, strain and stress distribution of a section are obtained for optimized standard 25m~45m PSSC composite bridge subjected to dead and live load in order to interpret the effect of prestressing and deformation of tendon. The stress and strain distribution and moment capacity are obtained for both noncomposite and composite section and for allowable stress limit state, yield limit state and strength limit state. Reliability analysis is conducted after assuming limit states for stress and flexural strength. The reliability index for standard PSSC composite bridge which is designed to satisfy the allowable stress for flexural strength are higher than 3.5 which is required reliability indexes on American code for LRFD. Reliability of PSSC girder which is designed based on allowable stress of bridge design code is high for flexural strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.6 s.58
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• pp.166-175
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• 2009

An experimental study was carried out to estimate the flexural performance of steel fiberreinforced self-compacting concrete. Seven slabs with three different steel fiber-reinforced concretes were prepared to make beam specimens. After proper curing period, each slab was cut to five beams with a diamond saw. The beam specimen was tested with displacement control method to obtain load-deflection curve. As the results, the self-compacting concrete beam showed higher flexural strength, ductility and toughness index compared to the normal concrete beam. This means that steel fiber-reinforced self-compacting concrete can be used more widely in the field of architecture and civil engineering because of its self-compactability and good mechanical properties.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.98-106
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• 2008

The strengthening in terms of efficiency, easy, economics is very popular method when it is applied to a damaged structures. The purpose of this study develops anchorage system that supports enough strengthening effect without any damage. In addition it is checked whether the method can be conveniently applied to structures. To verify strengthening effect a flexural experiments were performed. Four concrete beams were constructed and tested. Deflections, strains and modes of failure were recorded to examine strengthen of beams. Comparing crack load of each experimental data, yielding load, ultimate load, ductility index, and tendon stress were analyzed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.93-100
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• 2008

The use of fiber reinforced polymer (FRP) composites is significantly growing in construction and infrastructure applications where durability under harsh environmental conditions is of great concern. In order to examine the applicability of FRP rebar as a reinforcement in flexural member, flexural tests were conducted. 12 beams with different FRP materials such as CFRP, GFRP and Hybrid FRP and reinforcement ratio were tested and analyzed in terms of failure mode, moment-deflection, flexural capacity, ductility index and sectional strain distribution. The test results were also compared with the theoretical model represented in ACI 440.1R06. Test results indicate that the flexural capacity of the beams reinforced by FRP bars can be accurately predicted using the ultimate design theory. They also show that the current ACI model for computing the deflection overestimates the actual deflection of GFRP series and underestimates the deflection of CFRP series.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.532-541
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• 2016

The objective of this paper is to support accurate pavement condition assessment and decision of proper maintenance method and time by conducting visual inspection and calculating the remaining life of pavement from falling weight deflectometer(FWD) data. Each was implemented in the same long-term performance pavement(LTPP) sections. Visual inspection was executed to measure pavement condition indices such as crack, rutting and international roughness index(IRI) and the Seoul Pavement Index(SPI) was calculated based on these results. The dynamic modulus was back-calculated from the FWD data. The remaining pavement lives were determined from equivalent single axle loading(ESAL) and FWD data. Correlation of maintenance priority by each result value was examined. Consequently, the correlation between remaining life to Crack and Rutting was higher than the other factors or indicesbecause IRI is not related to FWD value and SPI value consists with IRI value and other indices. The R-square value of correlation of FWD with Crack and Rutting was 0.65, which indicated an insufficient correlation. Consequently, when decision of maintenance of method, time, etc. is determined, FWD data have to be considered with Crack and Rutting because of those relations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.11-20
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• 2013

In this paper, the quantitative damage index for reinforced concrete (RC) columns with non-seismic details were presented. They are necessary to carry out the postearthquake safety evaluation of RC buildings under 5 stories without seismic details. The static cyclic test of the RC frame sub-assemblage that was an one span and actual-sized was first conducted. The specimen collapsed by the shear failure after flexural yielding of a column, lots of cracks on the surfaces of columns and beam-column joints and the cover concrete splitting at the bottom of columns occurred. The damage levels of these kinds of columns with non-seismic details were classified to five based on the load-displacement relationship by the test result. The residual story drift ratios and crack widths were then adapted as the quantitative index to evaluate the damage limit states because those values were comparatively easy to measure right after earthquakes. The highest one among the residual story drift ratios under the similar maximum story drift ratio decided on the residual story drift ratio of each damage limit state. On the other hand, the lowest and average ones among the respective residual shear and flexural widths under the similar maximum story drift ratio decided on the residual shear and flexural widths of each damage limit state, respectively. These values for each damage limit state resulted in being smaller than those by the international damage evaluation guidelines that are for seismically designed members under the same deformations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.40-47
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• 2021

In this study, the structural behavior by the details of the lap region with the headed bar was estimated through finite element analysis. To solve the finite element analysis of the anchorage region with complex contact conditions and nonlinear behavior, a quasi-static analysis technique by explicit dynamic analysis was performed. The accuracy of the finite element model was verified by comparing the experimental results with the finite element analysis results. It was confirmed that the quasi-static analysis technique well reflected the behavior of enlarged headed bar connection. As a result of performing numerical analysis using 21 finite element models with various development lengths and transverse reinforcement indexes, it was confirmed that the increase of development length and transverse reinforcement index improved the maximum strength and ductility. However, to satisfy the structural performance, it should be confirmed that both design variables(development length and transverse reinforcement index) must be enough at the design criteria. In the recently revised design standard(KDS 14 20 52 :2021), a design formula of headed bar that considers both the development length and the transverse reinforcing bar index is presented. Also the results of this study confirmed that not only the development length but also transverse reinforcing bars have a very important effect.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.30-39
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• 2022

Maintaining structural integrity of major apparatuses in a nuclear power plant, including piping system, is recognized as a critical safety issue. The integrity of piping system is also a critical matter related to the safety of a nuclear power plant. The actual failure mode of a piping system due to a seismic load is the leakage due to a fatigue crack, and the structural damage mechanism is the low-cycle fatigue due to large relative displacement that may cause plastic deformation. In this study, in-plane cyclic loading tests were conducted under various constant amplitudes using specimens composed of steel straight pipes and a steel pipe tee in the piping system of a nuclear power plant. The loading amplitude was increased to consider the relative displacement generated in the piping system under seismic loads, and the test was conducted until leakage, which is the limit state of the steel pipe tee, occurred due to fatigue cracks. The limit state of the steel pipe tee was expressed using a damage model based on the damage index that used the force-displacement relationship. As a result, it was confirmed that the limit state of the steel pipe tee can be quantitatively expressed using the damage index.

• Journal of Food Hygiene and Safety
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• v.32 no.6
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• pp.493-499
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• 2017

This study was conducted to monitor the current status of pesticide residues and sulfur dioxide in a total of 91 functional rice products from February to October 2016. Multi class pesticide multiresidue methods of 220 pesticides was performed by the GC/ECD, GC/NPD, GC/TOF/MS, LC/PDA, and LC/FLD. As a result of analysis, the pesticides were detected in 3 samples, representing a detection rate of 3.3%. The kind of pesticides was propiconazole and isoprothiolane used for germicide in agriculture or plant growth regulator purposes. The detected levels were 0.0340~0.0566 mg/kg, which were under the MRL (Maximum Residues Limits). The contents of sulfur dioxide in 91 samples by the Monier-Williams method were not detected. Risk assessment of pesticides evaluated using human health exposure with the ratio of EDI (Estimated daily intake) to ADI (Acceptable daily intake). %ADI (the ratios of EDI to ADI) were 0.24~1.25% with safety level.