• Earthquakes and Structures
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• v.8 no.3
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• pp.761-778
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• 2015

The objective of this paper is to report the result of an experimental program conducted on the strengthening of nonductile RC frames by using external mesh reinforcement and plaster application. The main objective was to test an alternative strengthening technique for reinforced concrete buildings, which could be applied with minimum disturbance to the occupants. Generic specimen is two floors and one bay RC frame in 1/2 scales. The basic aim of tested strengthening techniques is to upgrade strength, ductility and stiffness of the member and/or the structural system. Six specimens, two of which were reference specimens and the remaining four of which had deficient steel detailing and poor concrete quality were strengthened and tested in an experimental program under cyclic loading. The parameters of the experimental study are mesh reinforcement ratio and plaster thickness of the infilled wall. The effects of the mesh reinforced plaster application for strengthening on behavior, strength, stiffness, failure mode and ductility of the specimens were investigated. Premature and unexpected failure mode has been observed at first and second specimens failed due to inadequate plaster thickness. Also third strengthened specimen failed due to inadequate lap splice of the external mesh reinforcement. The last modified specimen behaved satisfactorily with higher ultimate load carrying capacity. Externally reinforced infill wall composites improve seismic behavior by increasing lateral strength, lateral stiffness, and energy dissipation capacity of reinforced concrete buildings, and limit both structural and nonstructural damages caused by earthquakes.

• Structural Engineering and Mechanics
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• v.56 no.6
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• pp.899-916
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• 2015

Upgrading or strengthening of existing reinforced concrete (RC) infrastructure is an emerging demand nowadays. Near Surface Mounted (NSM) technique is very promising approach for flexural strengthening of RC members. However, premature failure such as concrete cover separation failure have been a main concern in utilizing this technique. In this study, U-wrap end anchorage with carbon fiber reinforced polymer (CFRP) fabrics is proposed to eliminate the concrete cover separation failure. Experimental programs were conducted to the consequence of U-wrap end anchorage on the flexurally strengthened RC beams with NSM-steel. A total of eight RC rectangular beam specimens were tested. One specimen was kept unstrengthened as a reference; three specimens were strengthened with NSM-steel bars and the remaining four specimens were strengthened with NSM-steel bars and U-wrap end anchorage using CFRP fabrics. A 3D non-linear finite element model (FEM) was developed to simulate the flexural response of the tested specimens. It is revealed that NSM-steel (with and without end-anchors) significantly improved the flexural strength; moreover decreased deflection and strains compared with reference specimen. Furthermore, NSM-steel with end anchorage strengthened specimens revealed the greater flexural strength and improve failure modes (premature to flexure) compared with the NSM-steel without end anchorage specimens. The results also ensured that the U-wrap end anchorage completely eliminate the concrete cover separation failure.

• The Korean Journal of Food And Nutrition
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• v.32 no.5
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• pp.536-552
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• 2019

The purpose of this study was to develop a standardized job description for dietitians using the DACUM technique. To examine the validity of job description through DACUM, dietitians were surveyed relative to importance, performance, and difficulty. The survey was conducted April 1-30, 2014. A total of 217 questionnaires were used in the analysis. The final developed job description for dietitians included six duties, 38 tasks, and 210 task elements. DACUM's findings include six duties: nutrition management, food service operation management, hygiene safety management, community food and nutrition program management, organization management, and professionalism strengthening. There were 5.1 points regarding importance, 4.1 points regarding performance, 4.9 points regarding difficulty, and statistically significant differences (p<0.001). Dietitians responded that 'nutrition management' and 'hygiene safety management' were the most important. 'Hygiene and safety management' showed the highest performance, and 'community food and nutrition program management' and 'professionalism strengthening'' showed the highest difficulty. Thus, it is considered that the job analysis results can be used to evaluate and improve the subjects' training program. Dietitians' jobs are subject to various environmental changes, such as demographic changes, health care system changes, and the development of the food industry, and thus, should be reviewed and analyzed periodically.

• Journal of the Korea Safety Management & Science
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• v.23 no.4
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• pp.23-29
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• 2021

The purpose of this study is to reduce the probability of occurrence of electric fires as a preemptive preventive measure, and to strengthen the capability of preventing electric fires by strengthening the cooperative function between electric fire-related departments and establishing a cooperative system. In this study, the general aspects of electric fires were identified by reviewing the literature such as ignition mechanisms of electric fires. And the major electrical fires that occurred in the last 10 years were classified into ignition factors (short circuit, overload/overcurrent, and earth leakage/ground fault) and ignition sources (wiring/wiring appliances, electrical equipment/household appliances). And the 4M technique was used to analyze the potential causes of ignition at the fire site and to suggest preventive measures. In the case In this study, out of 48 electrical fires in the past 10 years, 16 short-circuit fires, 3 overload/overcurrent fires, 3 short-circuit and earth fault fires, 16 fires in wiring/wiring appliances, and 10 fires in electrical equipment/home appliances classified as cases. And prevention measures were presented in terms of human, machine, media, and management by using the 4M technique. For the preemptive prevention of electric fires, strengthening the compulsory electrical safety inspection and making it mandatory to report when new or expanding electric facilities, charging a fee for electric safety inspection for detached houses and granting benefits subject to inspection completion, improvement of the electric safety voluntary inspection table and safety indications; It was suggested as a policy to organize and operate electrical safety inspection personnel in a two-person team (mixed), establish a close work cooperation system with related organizations, and strengthen electrical safety education and publicity.

• Journal of Korea Foundry Society
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• v.11 no.4
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• pp.293-302
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• 1991

Aluminum alloy matrix composites reinforced with various amounts of $Al_2O_3$ short fibers have been produced by a combined technique of rheo-compocasting and hot extrusion. Distribution of fibers in the composites fabricated by rheo-compocasting was relatively uniform. A good degree of uniaxial fiber alignment has been achieved by hot extrusion, but a lot of fibers fractured during extrusion. The tendency of fiber fracturing increases as the aspect ratio and the amount of fibers increase. Relatively good bonding between fiber and matrix was obtained by the formation of $MgAl_2O_4$ and Mg(Al, Fe)$_2O_4$ at the interface between fiber and matrix. In extruded composites, fiber-strengthening effect was relatively small since a lot of fibers fractured during hot extrusion. On the other hand, dispersion strengthening effect may increase. In order to improve the fiber strengthening effect, it is important to optimize the extrusion condition with consideration of metal flow in extrusion die.

• Earthquakes and Structures
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• v.5 no.2
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• pp.143-160
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• 2013

This paper presents the results of an experimental program concerning the efficiency of a specific strengthening technique which utilizes a small steel link element connected to the R/C frame through bracing elements. Brittle types of failure, especially at the connections between steel and concrete elements, can be avoided by appropriate design of the local details. Five single storey one bay R/C frames scaled 1:3 were constructed according to older codes with substandard details. The first one was a typical bare reference frame. The other four were identical to the first one, strengthened by steel bracing elements. The behavior of the strengthened frames is described with respect to the reference bare frame. The concrete frames were constructed according to older code provisions by the use of smooth steel bars, low strength concrete, sparsely spaced stirrups and substandard details. The strengthening scheme aimed to the increase of both strength and deformation capacity of the original R/C frame. The inelastic deformations are purposely concentrated to a short steel link element connecting the steel bracing to the R/C frame. The results show that the steel link element can increase considerably the strength and the energy dissipation capacity of the frame.

• International Journal of Concrete Structures and Materials
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• v.8 no.2
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• pp.141-155
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• 2014

The use of fiber reinforced polymer (FRP) composites in strengthening reinforced concrete beam-column subassemblies has been scrutinised both experimentally and numerically in recent years. While a multitude of numerical models are available, and many match the experimental results reasonably well, there are not many studies that have looked at the efficiency of different finite elements in a comparative way in order to clearly identify the best practice when it comes to modelling FRP for strengthening. The present study aims at investigating this within the context of FRP retrofitted reinforced concrete beam-column subassemblies. Two programs are used side by side; ANSYS and VecTor2. Results of the finite element modeling using these two programs are compared with a recent experimental study. Different failure and yield criteria along with different element types are implemented and a useful technique, which can reduce the number of elements considerably, is successfully employed for modeling planar structures subjected to in-plane loading in ANSYS. Comparison of the results shows that there is good agreement between ANSYS and VecTor2 results in monotonic loading. However, unlike VecTor2 program, implicit version of ANSYS program is not able to properly model the cyclic behavior of the modeled subassemblies. The paper will be useful to those who wish to study FRP strengthening applications numerically as it provides an insight into the choice of the elements and the methods of modeling to achieve desired accuracy and numerical stability, a matter not so clearly explored in the past in any of the published literature.

• Structural Engineering and Mechanics
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• v.56 no.1
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• pp.123-136
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• 2015

The proposed techniques to repair concrete members such as steel plates, fiber-reinforced polymers or concrete have important deficiencies in adherence and durability. The use of ultra high performance fiber concrete (UHPFC) can overtake effectively these problems. In this paper, the possibility of using UHPFC to strengthen reinforced concrete beams under torsion is investigated. Seven specimens of concrete beams reinforced with longitudinal and transverse reinforcements. One of these beams consider as control specimen while the others was strengthened by UHPFC on four, three, and two sides. This study includes experimental results of all beams with different types of configurations and thickness of UHPFC. As well as, finite element analysis was conducted in tandem with experimental test. Results reveal the effectiveness of the proposed technique at cracking and ultimate torque for different beam strengthening configurations, torque - twist graphs and crack patterns. The UHPFC can generally be used as an effective external torsional reinforcement for RC beams. It was noted that the behavior of the beams strengthen with UHPFC are better than the control beams. This increase was proportional to the retrofitted beam sides. The use of UHPFC had effect in delaying the growth of crack formation. The finite element analysis is reasonably agreement with the experimental data.

• 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.115-125
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• 2009

In these days, carbon fiber-reinforced polymers (CFRP) have been widely used for retrofitting and/or strengthening structural elements. However, there are not enough test data to predict the long-term performance of the retrofitted structures exposed to freeze-thawing cycles. This paper presents the results of experimental program undertaken to investigate the effects of freeze-thawing cycling (from-18 to $4^{\circ}C) on the behavior and failure characteristics of reinforced concrete (RC) beams strengthened in shear with CFRP sheet and plate using acoustic emission (AE) technique.

• Journal of the Ergonomics Society of Korea
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• v.23 no.3
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• pp.53-72
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• 2004

Today we are observing a lot of injuries, casualties, and property losses that are mainly caused by the defects of products. In order to derive safety designs, which minimize the possibility of such product liability-related accidents, we need to take into account the user-product interaction as an important part of the danger factor analysis. Existing risk analysis techniques, however, have some limitations in detecting comprehensive danger factors that are peculiarly involved in human errors and the functional defects of products. Researches on danger factor analysis regarding the user-product interaction have been carried out actively in ergonomics. In this paper, we suggest a novel product risk analysis technique, which is more objective and systematic compared to the previous ones, by combining a modified TAFEI (Task Analysis For Error Identification) technique with SASA (Systematic Approach to Accident Scenario Analysis) technique. By applying this technique to the product design practice in industry, corporations will be able to improve the product safety, consequently strengthening the competitiveness.