• Journal of the Korea Institute of Building Construction
• /
• v.14 no.5
• /
• pp.433-442
• /
• 2014

The most design criteria and specifications in Korea utilized to ensure appropriate quality are based on process and prescriptive criteria determining materials, measure and methods. It has many problems including a loss of competitiveness resulting from inhibited creativity of the contractors. The performance-based specifications focused on final product are being proposed, but have difficulty in adapting to the architectural field. In this study the hybrid specification prototype for curtain wall construction was suggested. The specification framework was presented through analysis of linkage between the performance and prescriptive specification cases. Based on the survey with practitioners, the performance inspection process and the sample specification were developed by identifying the essential performance test timings. The applicability of the specification prototype was evaluated by interviews with experts. It was found that the prototype was active and a progressive supporting tool which could support to secure phased performance during construction as well as final performance.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.10
• /
• pp.6282-6288
• /
• 2014

$CO_2$ welding is used widely in the field. On the other hand, welding defects occur when welders cannot adjust the current and voltage needed for welding and have to stop working to adjust the current and voltage, causing sudden cooling down of the welding structure inside a vehicle or tank where the control panel is invisible or when work site is far. This study used three types of existing $CO_2$ welders. This also applied SS400 rolled steel for welding structural purposes for remote control torch welding, perform a welding test through v-groove butt welding with a remote control torch and existing $CO_2$ welding torch, conducted visual inspection on the appearance of a welded top bead. In addition, the appearance quality of the welding part was monitored mainly through penetrant testing and a bending test to evaluate the welding defect reduction and the effect on the performance and compatibility by replacing the existing welder.

• Structural Engineering and Mechanics
• /
• v.85 no.4
• /
• pp.531-543
• /
• 2023

The existing concrete bridges are time-varying working systems, where the maintenance strategy should be planned according to the time-varying performance of the bridge. This work proposes a time-dependent residual capacity assessment procedure, which considers the non-stationary bridge load effects under growing traffic and non-stationary structural deterioration owing to material degradations. Lifetime bridge load effects under traffic growth are predicated by the non-stationary peaks-over-threshold (POT) method using time-dependent generalized Pareto distribution (GPD) models. The non-stationary structural resistance owing to material degradation is modeled by incorporating the Gamma deterioration process and field inspection data. A three-span continuous box-girder bridge is illustrated as an example to demonstrate the application of the proposed procedure, and the time-varying reliability indexes of the bridge girder are calculated. The accuracy of the proposed non-stationary POT method is verified through numerical examples, where the shape parameter of the time-varying GPD model is constant but the threshold and scale parameters are polynomial functions increasing with time. The case study illustrates that the residual flexural capacities show a degradation trend from a slow decrease to an accelerated decrease under traffic growth and material degradation. The reliability index for the mid-span cross-section reduces from 4.91 to 4.55 after being in service for 100 years, and the value is from 4.96 to 4.75 for the mid-support cross-section. The studied bridge shows no safety risk under traffic growth and structural deterioration owing to its high design safety reserve. However, applying the proposed numerical approach to analyze the degradation of residual bearing capacity for bridge structures with low safety reserves is of great significance for management and maintenance.

• Korean Journal of Clinical Laboratory Science
• /
• v.49 no.2
• /
• pp.108-113
• /
• 2017

A sudden cardiac death (SCD) is defined as an unnatural sudden death caused by heart disease. To determine the cause of death, observation of the microscopic change in cardiac muscle tissue is suggested, rather than visual postmortem examination. However, this suggestion is time consuming to be applied in the field, is cost-ineffective, and is inconvenient. Therefore, the purpose of this study is to understand whether temporary inspection used to examine the cardiac marker (Myoglobin, CK-MB, cTn I) in postmortem blood via rapid cardiac triple test kit (which is used by clinics to diagnose patients with acute myocardial infarction) can effectively be utilized for the paragnosis of sudden, unnatural cardiac death. The results of postmortem examination and temporary investigation found that 23 groups (76.7%), among the 30 experimental groups, were assumed to be non-traumatic sudden cardiac deaths, which indicated a positive response (according to comparison with forensic autopsy); 4 groups, among the 10 control groups, were assumed to be cerebrovascular disease, which indicated a negative response; 1 group was assumed to be alcoholic and drug poisoning, indicating a positive response; and 1 group was assumed to be oxygen deficiency due to suffocation, indicating a positive response. Hence, it was found that the level of sensitivity and specificity of cardiac marker's temporary inspection showed significant result, 76.7% and 80% respectively. Given this, temporary inspection can be effectively used for the paragnosis of sudden cardiac death when the medical history, situation of the site, and postmortem interval are considered together. With the result of precedent research on time of first revelation and extinction in blood, and difference in concentration over time progress according to the characteristic of cardiac marker's (myoglobin, CK-MB, cTn I) individual material, further research on concentration of cardiac marker per each post time needs to be conducted in order to estimate time science death (which is required to identify the cause of death and investigation).

• Korean Chemical Engineering Research
• /
• v.55 no.3
• /
• pp.322-331
• /
• 2017

District heating was first introduced in Korea in 1985. As the service life of the underground thermal piping network has increased for more than 30 years, the maintenance of the underground thermal pipe has become an important issue. A variety of complex technologies are required for periodic inspection and operation management for the maintenance of the aged thermal piping network. Especially, it is required to develop a model that can be used for decision making in order to derive optimal maintenance and replacement point from the economic viewpoint in the field. In this study, the analysis was carried out based on the repair history and accident data at the operation of the thermal pipe network of five districts in the Korea District Heating Corporation. A failure probability model was developed by introducing statistical techniques of qualitative analysis and binomial logistic regression analysis. As a result of qualitative analysis of maintenance history and accident data, the most important cause of pipeline damage was construction erosion, corrosion of pipe and bad material accounted for about 82%. In the statistical model analysis, by setting the separation point of the classification to 0.25, the accuracy of the thermal pipe breakage and non-breakage classification improved to 73.5%. In order to establish the failure probability model, the fitness of the model was verified through the Hosmer and Lemeshow test, the independent test of the independent variables, and the Chi-Square test of the model. According to the results of analysis of the risk of thermal pipe network damage, the highest probability of failure was analyzed as the thermal pipeline constructed by the F construction company in the reducer pipe of less than 250mm, which is more than 10 years on the Seoul area motorway in winter. The results of this study can be used to prioritize maintenance, preventive inspection, and replacement of thermal piping systems. In addition, it will be possible to reduce the frequency of thermal pipeline damage and to use it more aggressively to manage thermal piping network by establishing and coping with accident prevention plan in advance such as inspection and maintenance.

• Journal of fish pathology
• /
• v.26 no.2
• /
• pp.111-116
• /
• 2013

In this study, the disinfectant efficacy of Aqua farmsafe$^{(R)}$, composed of didecyldimethylammonium chloride (DDAC) and yucca extract was evaluated against Salmonella typhimurium and fish pathogens. Determination of the anti-microbial or anti-viral efficacy of the disinfectant was based on Animal, Plant and Fisheries Quarantine and Inspection Agency Regulation No. 2011-26, Korea. Anti-bacterial efficacy test by broth dilution method was used to determine the lowest effective dilution of the disinfectant following exposure to test bacteria for 30 min at $4^{\circ}C$. Aqua farmsafe and test bacteria or virus were diluted with distilled water (DW), standard hard water (SW) or organic matter dilution (OM) according to treatment condition. Under the our results, disinfectant efficacy of Aqua farmsafe$^{(R)}$ possesses 30~40 fold against fish pathogens including bacteria and virus compared to that on animal pathogenic bacteria, S. typhimurim. As the efficacy of Aqua farmsafe$^{(R)}$ against fish pathogen was investigated in vitro, a controlled field trial is required to determine whether the use of Aqua farmsafe$^{(R)}$ will be able to reduce fish diseases.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.6
• /
• pp.92-98
• /
• 2019

In this study, we developed a repair material incorporating PVA powder resin and nylon fiber into cemented carbide used in the existing field to improve adhesion performance and water tightness with existing concrete. Flexural behavior evaluation was performed. The main experimental variables were PVA powder resin, nylon fiber mixing rate and damage type, and performance tests were conducted to evaluate compressive strength and flexural behavior after repairing materials. It was found that all formulations fully satisfied the required performance of the repair material. The flexural strength test results of the repaired tube specimens showed that the performance of the repaired materials was maximized when the nylon fiber was added and the PVA powder was added in an appropriate amount. The flexural behavior of all the specimens showed the flexural behavior of the structural members with a low rebar ratio, suggesting that the amount of iron wire in the domestic fume pipe was somewhat insufficient. That is, it was confirmed that the amount of reinforcement of the steel wire was somewhat small, so that the concrete was cracked before the behavior of the concrete and the steel wire reached the extreme state, and the concrete was immediately destroyed beyond the tensile strength of the concrete.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.1
• /
• pp.81-89
• /
• 2018

Austenitic stainless steels have excellent corrosion resistance, durability and fire resistance. Especially, since STS304L among austenitic types is a low-carbon variation of STS304 and has excellent intergranular corrosion resistance, it can often be used under the welded condition without heat treatment after field welding. This paper investigated ultimate behaviors such as ultimate strength and weld metal fracture mechanism of STS304L fillet-welded connections with TIG(tungsten inert gas) welding through test results. Main variables of specimens are weld length and welding direction against loading. Fracture of specimens are classified into three modes(tensile fracture, shear fracture and block shear fracture). Ultimate strengths were compared according to the welding direction and weld length and TFW series with transverse fillet weld had the highest strength compared with other types(LFW series with longitudinal fillet weld and FW series with all round weld). It is known that current design specifications such as KBC 2016 and AISC2010 underestimated the strength of TFW and LFW specimens and provided unconservative estimates for FW specimens. Finally, strength equations were proposed considering material properties of STS 304L material.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.5
• /
• pp.92-100
• /
• 2011

This paper describes a numerical modeling for deflection calculation using the natural frequency response that is measured acceleration response for concrete bridges. In the formulation of the dynamic deflection, the change amounts and the transformed responses about six kinds of free vibration responses are defined totally. The predicted response can be obtained from the measured acceleration data without requiring the knowledge of the initial velocity and displacement information. The relationship between the predicted response and the actual deflection is derived using the mathematical modeling that is induced by the process of a acceleration test data. In this study, in order to apply the proposed response predicted model to the integration scheme of the natural frequency domain, the Fourier Fast Transform of the deflection response is separated into the frequency component of the measured data. The feasibility for field application of the proposed calculation method is tested by the mode superposition method using the PSC-I bridges superstructures under several cases of moving load and results are compared with the actually measured deflections using transducers. It has been observed that the proposed method can asses the deflection responses successfully when the measured acceleration signals include the vehicle loading state and the free vibration behavior.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.16 no.1
• /
• pp.120-130
• /
• 2012

As long span and complex bridges are constructed often recently, safety estimation became a big issue. Various types of measuring instruments are installed in case of long span bridge. New wireless technologies for long span bridges such as sending information through a gateway at the field or sending it through cables by signal processing the sensing data are applied these days. However, The case of occurred accidents related to bridge in the world have been reported that serious accidents occur due to lack of real-time proactive, intelligent action based on recognition accidents. To solve this problem in this study, the idea of "communication among things", which is the basic method of RFID/USN technology, is applied to the bridge monitoring system. A sensor node module for USN based intelligent bridge system in which sensor are utilized on the bridge and communicates interactively to prevent accidents when it captures the alert signals and urgent events, sends RF wireless signal to the nearest traffic signal to block the traffic and prevent massive accidents, is designed and tested by performing TinyOS based middleware design and sensor test free Space trans-receiving distance.