• Computers and Concrete
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• v.24 no.3
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• pp.237-247
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• 2019

The key issue for the finite element analysis (FEA) of section steel reinforced concrete (SRC) structure is how to consider the bond-slip performance. However, the bond-slip performance is hardly considered in the FEA of SRC structures because it is difficult to achieve in the finite element (FE) model. To this end, the software developed by Python can automatically add spring elements for the FE model in ABAQUS to considering bond-slip performance. The FE models of the push-out test were conducted by the software and calculated by ABAQUS. Comparing the calculated results with the experimental ones showed that: (1) the FE model of SRC structure with the bond-slip performance can be efficiently and accurately conducted by the software. For the specimen with a length of 1140 mm, 3565 spring elements were added to the FE model in just 6.46s. In addition, different bond-slip performance can also be set on the outer side, the inner side of the flange and the web. (2) The results of the FE analysis were verified against the corresponding experimental results in terms of the law of the occurrence and development of concrete cracks, the stress distribution on steel, concrete and steel bar, and the P-S curve of the loading and free end.

• Korean Journal of Ichthyology
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• v.35 no.3
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• pp.194-200
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• 2023

The Yellowfin surgeonfish, Acanthurus xanthopterus was reported as the first confirmed record from Korea based on a single specimen (332.6 mm SL) collected from the coast from Geomundo Island. It is characterized by having a longitudinal yellowish band in front of eye, dorsal and anal fins with 4 bluish stripes, and broad yellowish bar distally on pectoral fin. The new Korean name, "No-rang-munui-yang-jwi-dom", is proposed for the species.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.570-576
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• 2002

Application of the aged Inconel 718 in hydrogen environment is seriously restraint by its high hydrogen embrittlement (HE) sensitivity. m previous researches, we have suggested the possibility and applicability of the laser surface annealing (LSA) process in improving the HE resistance of this alloy. Sequentially, a study on the effects of the precipitates in the Inconel 718 on its HE sensitivity was conducted in this research. Firstly, flat bar specimens were heat-treated to obtain various kinds of precipitation microstructures concerning the ${\gamma}$" phase and the 6 phase. Hydrogen was charged into the specimen by a cathodic charging process. The loss in reduction of area (RA) caused by hydrogen charging was used to assess the HE sensitivity. The HE sensitivity of the alloy was lowered with decreasing the volume fraction of ${\gamma}$". Moreover, it was possible to increase the HE resistance of the aged alloy by dissolving the $\delta$ phase, keeping the strength at the same level as that of the common aged alloy. Thus, we concluded that both the $\delta$ phase and the ${\gamma}$" phase affected the HE sensitivity of Inconel 718. Next, two kinds of notch tensile specimens were fabricated, one kind having $\delta$ phase and the other having no $\delta$ phase. All these specimens were aged via the same aging heat treatment process. The LSA process annealed a thin layer of the notch bottom of each specimen. One specimen of each kind was charged with hydrogen by the cathodic hydrogen charging process. Loss in the notch tensile strength (NTS) caused by hydrogen was used to evaluate the HE sensitivity. It was found that while the HE sensitivity of conventionally aged Inconel 718 was decreased by the LSA process, the HE sensitivity of the $\delta$-free aged Inconel 718 could further be decreased. Therefore, for applications in hydrogen environments, it is possible to fabricate alloys with both good HE resistance and high strength by controlling the precipitation conditions, and to improve HE resistance further via applying the LSA process.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.33-40
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• 2021

Measuring the compressive strength of concrete is a very important factor in the safety review of concrete structures. Concrete compressive strength measurement methods include destructive and non-destructive methods. The destructive method includes the uniaxial compression failure method, and the non-destructive method includes the rebound hardness method and the elastic wave measurement method. In this study, the type of measurement method and the effect of reinforcing bars inside the concrete were tested to examine the relationship between them. Regardless of the type of specimen, the average compressive strength by the elastic wave measurement method among the three experimental methods was greater than the average compressive strength by the other methods. When the specimen type is the same, the standard deviation of the measured values of the elastic wave measurement method is smaller than that of the other measurement methods, so it can be seen that the elastic wave measurement method does not show large variance in the measured values compared to the other two measurement methods. When the average compressive strength according to the test method for each specimen was compared with the average compressive strength of the compressive failure test method, the average compressive strength was measured to be high in the order of the elastic wave measurement method, the compression failure test, and the rebound hardness method. Since the measured values of the compressive strength of concrete are different depending on the method of measuring the compressive strength of concrete and the presence or absence of reinforcing bars inside the concrete, further research is required considering the effect of various concrete covers.

• The Journal of the Korean Society for Microbiology
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• v.11 no.1
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• pp.69-78
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• 1976

There have been increasing reports of mycobacterioses in man and animals caused by "atypical" or "opportunist" mycobacteria. At the presnt, "opportunist mycobacterioses" are not generally responsive to antituberculosis drugs, and therefore, create considerable problems with regard to chemotherapy and control measures. In recent years studies have been made to isolate opportunist mycobacteria from soil, house-dusts and tap-water. It seemed quite interesting to define the extent of circumstantial presence of "opportunist" mycobacteria and nocardia in the soils of school-ground of primary schools and middle-high schools. This communication is the results of pilot study to isolate and identify "opportunist" mycobacteria and nocardia from 504 soil specimens of 72 schools in Seoul City. 1. Of a total of 59 isolates from 504 soil specimens tested, 32 strains were identified as opportunist mycobacteria and 27 strains as nocardia. 2. Isolation rates of opportunist mycobacteria by the areas(of specimen collection) were as follows: 36.4% in the southern area of Han-River, 33.3% in the central area, 22.7% in the outskirt area and 16.6% in the intermediate area. There observed no apparent difference in the isolation rates both-between the areas and between primary schools and middle-high schools. However, a significant difference was noted in the isolation rates between the places of soil sampling in a given school(P<0.05), i.e., the highest was the soil of refuge heaps(15.2%), and tap-water pole area(11.1%), the school-lavatory entrance(9.7%), the school gate entrance(5.5%), and iron-bar play ground(2.7%). The soil specimens from the center of school ground and from school building entrance yielded none of mycobacterial isolates. 3. Isolation rates of nocardia by the areas were as follows: 33.3% in the central area, 31.8% in the outskirt area, 27.3% in the southern ares of Han-River and 11.1% in the intermediate area. As in the case of mycobacteral isolates, there observed no apparent differences in the isolation rates both between the areas and between primary schools and middle-high schools, but a significant difference was noted between the places of soil sampling(P<0.05), i.e., the highest was the soil of school building entrance(15.2%), and of school gate entrance(6.9%), refuge heaps(5.5,%), iron-bar play ground(4.1%), the school-lavatory entrance(2.7%) and tap-water pole area(2.7%), respectively. The soil specimens from the center of, school ground yielded none of nocardia isolates. 4. Of the 32 strains of isolated mycobacteria. 15 strains were slow-growing mycobacteria and the remaining 17 strains belonged to the rapid growers. Of the 15 slow-growers. 4 strains were M. scrofulaceum-szulgai complex, 3 M. gordonae, 4 M. terrae-triviale complex, 2 M. avium-intracellulare-xenopi complex, and 2 unclassified schotochromogens. Of the 17 strains of rapid growers, 12 were M. diernhoferi, 2 M. fortuitum-peregrinum complex, 2 M. vaccae and one M. flavescens. 5. Of the 27 strains of nocardia isolated, 11 strains were N. transvalensis, 5 N. convoluta, 5 N. erythropolis, one N. vaccinii, one N. polychromogens-paraffinae complex and 4 untypable strains of orange-pigmented nocardia spp.

• Magazine of the Korea Concrete Institute
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• v.3 no.2
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• pp.123-132
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• 1991

The purpose of this study was to Investigate the effects of bent - up bar Within beam - column 1lint core with High - Strength Concrete up to 800kg/$cm^2$. To achieve these objectives, 5 specimens were designed and tested under monotoric loading and reversed cyclic loadings. The primary variables were the number of bent-up bars, compressive strength of concrete and loading patterns. The results showed that the load capacity of specimen subjected to monotonic loading had more large than that of specirnn subjected to reversed cyclic loadings and the bent - up bar within joint core could prevented the crack at the joint face from propagating into the pint core but the failure was concentrated at the face of beam - column pint. Thus the study on flexural strength ratio should be accomplished before using bent - up bars within the joint core.

• Journal of Conservation Science
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• v.35 no.6
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• pp.631-640
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• 2019

The purpose of this study was to compare analytical results of sand iron bars reproduced by the traditional iron-making method through a destructive analysis and a non-destructive analysis. For these studies, we produced two types of samples. One was sample(SI-A), a part of the sand iron bar for destructive analysis. The other was SI-B(9 ㎠) for non-destructive analysis. A metallurgical microscope and scanning electron microscope were used for the destructive analysis, and neutron imaging analysis with the Hokkaido University Neutron Source (HUNS) at Hokkaido University, Japan, was used for the non-destructive analysis. The results obtained by destructive analysis showed that there was ferrite and pearlite of fine crystallite size, and some of these showed Widmanstätten ferrite microstructure grown within the pearlite and coarse ferrite at the edge of the specimen. The results from the neutron imaging analysis showed that there was also ferrite and pearlite with 3 ㎛ α-Fe of BCC structure. Based on these results, neutron imaging analysis is capable of identifying material characteristics without destroying the object and obtaining optimal research results when applying it to objects of cultural heritage.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.581-589
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• 2014

This paper presents the tension stiffening behavior from experimental results of each 6 amorphous steel fibers and normal steel fibers reinforced direct tensile specimens with the main variables such as cover thickness to bar diameter ratio. A tension stiffening effect for steel fiber reinforced RC tension members improve on the increase in cover thickness, and also amorphous steel fiber is usually superior to normal steel fiber. The reinforcement of steel fibers controlled the splitting cracks and led to significant increase in the tension stiffening effect. In particular, if cover thickness is more than twice the bar diameter, the amorphous steel fiber reinforced specimen is controlled the splitting crack and increased the tension stiffening effect. And, the tension stiffening effect of amorphous steel fiber reinforced concrete tension members is different to current structural design code provision.

• Journal of Korean Society of Steel Construction
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• v.26 no.1
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• pp.55-68
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• 2014

In this study, the beam-to column connections of concrete-encased-and-filled steel tube columns were tested under cyclic loading. Two specimens using steel beams and two specimens using precast concrete beams were tested. The dimension of the column cross section was $670mm{\pm}670mm$. The beam depths were 488mm and 588mm for the steel beams and 700mm for the precast concrete beams. The longitudinal bar ratios of the precast concrete beams were 1.1% and 1.5%. For the connections to the steel beams, continuity plates were used in the tube columns. For the connections to the PC beams, couplers were used for beam re-bar connections. The test results showed that except for a specimen, deformation capacities of the specimens were greater than 4% rotation angle, which is the requirement for the Special Moment Frame. Particularly, specimens using precast concrete beam showed excellent performances in the strength, deformation, and energy dissipation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.81-88
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• 2022

In the NRC (New paradigm Reinforced Concrete) beam, steel forms, main angles used as main reinforcements, and shear angles used as basic shear reinforcements are welded and assembled in the form of vierendeel truss structures in a steel factory. After the NRC truss frame is installed at the site, additional main reinforcement and shear reinforcement are distributed. In this study, the shear performance evaluation of the NRC beam was conducted through shear tests in accordance with the type of shear reinforcement of the NRC beam (shear angle, inclined shear reinforcing bar, and U-type cover bar). As a result of the test, the initial stiffness was similar before the initial cracking of each specimen, and all specimens were shear fractured.The shear reinforcements of the specimens exhibited a yielding behavior at the time of the maximum sheat force, and the shear strengths of the specimens increased as the amount of reinforcement of the shear reinforcement increased. These results show that NRC shear reinforcements exhibit shear performance corresponding to their shear strength contribution. As a result of calculating the nominal shear strengths according to KDS 14 20 22, the experimental shear strengths of the NRC beam specimens with shear reinforcement was 37~146% larger than the nominal shear strengths, so It was evaluated as a safety side.