• Corrosion Science and Technology
• /
• v.13 no.6
• /
• pp.214-223
• /
• 2014

Interest in the durability assessment and structural performance has increased according to an increase of concrete structures in salt damage environment recent years. Reliable way ensuring the most accelerated corrosion test is a method of performing the rebar corrosion monitoring as exposed directly to the marine test site exposure. However, long-term exposure test has a disadvantage because of a long period of time. Therefore, many studies on reinforced concrete in salt damage environments have been developed as alternatives to replace this. However, accelerated corrosion test is appropriate to evaluate the critical chlorine concentration in the short term, but only accelerated test method, is not easy to get correct answer. Accuracy of correlation acceleration test depends on the period of the degree of exposure environments. Therefore, in this study, depending on the concrete mix material, by the test was performed on the basis of the composite degradation of the salt damage, and investigate the difference of corrosion initiation time of the rebar, and indoor corrosion time of the structure, of the marine environment of the actual environments were inuestigated. The correlation coefficient was derived in the experiment. Long-term exposure test was actually conducted in consideration of the exposure conditions submerged zone, splash zone and tidal zone. The accelerated corrosion tests were carried out by immersion conditions, and by the combined deterioration due to the carbonation and accelerated corrosion due to wet and dry condition.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.2
• /
• pp.940-951
• /
• 2014

This study was to investigate of nursing activities performed by nursing staffs in long-term care hospitals. A survey of was conducted with 131 nurses who were working in 15 geriatric hospitals using a structural questionnaire. Data were collected from March 7 to June 30, 2013 and analyzed with SPSS 17.0, using descriptive statistics and t-test, ANOVA. This survey confirmed that the 88 activities except to 'making nursing diagnosis', 'setting nursing goals', and 'writting patient evaluation checklist' had been practiced in a wide range of nurses with nurse assistants. The degree of performance by nurse assistant was significantly different among nurses group according to the total number of patient and number of nurse(p<.001). Therefore, it is necessary to establish the legal and institutional regulation and development of algorithm for delegation, classify the impossible nursing task and work that can be delegated long-term care hospital.

• Journal of Chest Surgery
• /
• v.34 no.9
• /
• pp.686-691
• /
• 2001

Background: The Duromedics valve has been used in Korea since 1982, however, but there were no long term clinical results that have been reported. This paper presents the long term clinical results of Duromedics valve implanted in Seoul National University Hospital. Material and method: Between 1987, 23 patients underwnet cardiac valve replacement with Duromedics mechanical valve. There were 8 mitral valve replacements, 5 aortic valve replacements, one tricuspid valve replacement, 6 aortic and mitral valve replacements, and one mitral and tricuspid valve replacement. There were 12 men and 11 women. The mean age was 35$\pm$10(15~52) years. We evaluated the clinical performance of Duromedics cardiac prosthesis. Result: The early operative mortality was 4.3%(1/23) and the late morlatity was 4.3%(1/23). Causes of death were low cardiac output syndrome and structural valvular failure. The mean follow-up duration was 133$\pm$43(8~157) months. There were 3 reoperations. The causes of reoperations were thrombosis and structural failure and nonstructural valvular failure. The actuarial survival rate at 10 years was 90.9%. Conclusion: Although the number of patients was not sufficient for effective clinical study, the long term clinical results of Duromedics valve was relatively good and there was no structural defect in this mechanical valve. However, more research is needed in the future.

• Smart Structures and Systems
• /
• v.11 no.5
• /
• pp.453-476
• /
• 2013

DuraMote is a remote sensing system developed for the "NIST TIP project: next generation SCADA for prevention and mitigation of water system infrastructure disaster". It is designed for supervisory control and data acquisition (SCADA) of ruptures in water pipes. Micro-electro mechanical (MEMS) accelerometers, which record the vibration of the pipe wall, are used detect the ruptures. However, the performance of Duramote cannot be verified directly on a water distribution system because it lacks an acceptable recordable level of ambient vibration. Instead, a long-span cable-stayed bridge is an ideal test-bed to validate the accuracy, the reliability, and the robustness of DuraMote because the bridge has an acceptable level of ambient vibration. The acceleration data recorded on the bridge were used to identify the modal properties of the structure and to verify the performance of DuraMote. During the test period, the bridge was subjected to heavy rain, wind, and a typhoon but the system demonstrates its robustness and durability.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.181-184
• /
• 2006

Traditional durability analysis is not possible to provide a controlled durability and long-term performance of concrete structures. Recently, research works have shown that probabilistic approach based on the theory of structural reliability, would be very valuable for durability analysis. In this study, the probabilistic durability analysis based on a Monte Carlo Simulation was carried out using sample data selected from detailed field investigation. The probabilistic properties of some design variables, such as diffusion coefficients of concrete and surface chloride concentration, were newly determined using some experimental data. By applying a probabilistic durability analysis to an integral structural design, the durability performance of concrete structures would be remarkably improved.

• Wind and Structures
• /
• v.25 no.2
• /
• pp.195-214
• /
• 2017

Full-scale wind characteristics based on the field measurements is an essential element in structural wind engineering. Statistical analysis of the wind characteristics at Sutong Cable-stayed Bridge (SCB) site is conducted in this study with the recorded long-term wind data from structural health monitoring system (SHMS) between 2008 and 2015. Both the mean and turbulent wind characteristics and power spectra are comprehensively investigated and compared with those in the current codes of practice, such as the measured wind rose diagram, monthly maximum mean wind speed, turbulence intensity, integral length scale. Measurement results based on the monitoring data show that winds surrounding the SCB site are substantially influenced by the southeast monsoon in summer and strong northern wind in winter. The measured turbulence intensity is slightly higher than the recommended values in specifications, while the measured ratio of lateral to longitudinal turbulence intensity is slightly lower. An approximately linear relationship between the measured turbulence intensities and gust factors is obtained. The mean value of the turbulence integral length scale is smaller than that of typical typhoon events. In addition, it is found that the Kaimal spectrum is suitable to be adopted as the power spectrum for longitudinal wind component at the SCB site. This contribution would provide important wind characteristic references for the wind performance evaluation of SCB and other civil infrastructures in adjacent regions.

• Smart Structures and Systems
• /
• v.24 no.4
• /
• pp.507-524
• /
• 2019

A Bayesian dynamic linear model (BDLM) is presented for a data-driven analysis for response prediction and load effect separation of a revolving auditorium structure, where the main loads are self-weight and dead loads, temperature load, and audience load. Analyses are carried out based on the long-term monitoring data for static strains on several key members of the structure. Three improvements are introduced to the ordinary regression BDLM, which are a classificatory regression term to address the temporary audience load effect, improved inference for the variance of observation noise to be updated continuously, and component discount factors for effective load effect separation. The effects of those improvements are evaluated regarding the root mean square errors, standard deviations, and 95% confidence intervals of the predictions. Bayes factors are used for evaluating the probability distributions of the predictions, which are essential to structural condition assessments, such as outlier identification and reliability analysis. The performance of the present BDLM has been successfully verified based on the simulated data and the real data obtained from the structural health monitoring system installed on the revolving structure.

• Smart Structures and Systems
• /
• v.11 no.5
• /
• pp.511-531
• /
• 2013

Recent advances in low-cost remote monitoring systems have made it possible and practical to perform structural health monitoring (SHM) on a large scale. However, it is difficult for a single remote monitoring system to cover a wide range of SHM applications due to the amount of specialization required. For the remote monitoring system to be flexible, sustainable, and robust, this article introduces a new cost-effective, advanced remote monitoring and inspection system named DuraMote that can serve as a next generation supervisory control and data acquisition (SCADA) system for civil infrastructure systems. To evaluate the performance of DuraMote, we conduct experiments at two representative counterpart sites: a bridge and water pipelines. The objectives of this article are to improve upon the existing SCADA by integrating the remote monitoring system (i.e., DuraMote), to describe a prototype SCADA for civil engineering structures, and to validate its effectiveness with long-term field deployment results.

• Wind and Structures
• /
• v.12 no.5
• /
• pp.425-439
• /
• 2009

The expediency of revising universal rules for the combination of gravity and lateral actions of wind force-resisting steel structures recommended by the Standards EN 1990 and ASCE/SEI 7-05 is discussed. Extreme wind forces, gravity actions and their combinations for the limit state design of structures are considered. The effect of statistical uncertainties of extreme wind pressure and steel yield strength on the structural safety of beam-column joints of wind force-resisting multistory steel frames designed by the partial factor design (PFD) and the load and resistance factor design (LRFD) methods is demonstrated. The limit state criterion and the performance process of steel frame joints are presented and considered. Their long-term survival probability analysis is based on the unsophisticated method of transformed conditional probabilities. A numerical example illustrates some discrepancies in international design standards and the necessity to revise the rule of universal combinations of loads in wind and structural engineering.

• Earthquakes and Structures
• /
• v.22 no.6
• /
• pp.561-570
• /
• 2022

It is of great importance to be able to evaluate different structural systems not only based on their seismic performance but also considering their lifetime service costs. Many structural systems exist that can meet the engineering requirements for different performance levels; therefore, these systems shall be selected based on their economic costs over time. In this paper, two structural systems, including special steel moment-resisting and the ordinary concentric braced frames, are considered, which are designed to meet the three performance levels: Immediate Occupancy (IO), Life Safety (LS), Collapse Prevention (CP). The seismic behavior of these two systems is studied under three strong ground motions (i.e., Tabas, Bam, Kajour earthquake records) using the Perform3D package, and the incurred damages to the studied systems are examined at two hazard levels. Economic analyses were performed to determine the most economical structural system to meet the specified performance level requirements, considering the initial cost and costs associated with damages of an earthquake that occurred during their lifetime. In essence, the economic lifetime study results show that the special moment-resisting frames at IO and LS performance levels are at least 20% more economical than braced frames. The result of the study for these building systems with different heights designed for different performance levels also shows it is more economical from the perspective of long-term ownership of the property to design for higher performance levels even though the initial construction cost is higher.