• Structural Engineering and Mechanics
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• v.49 no.2
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• pp.203-223
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• 2014

The extensive use of prestressed reinforced concrete (PSC) highway bridges in marine environment drastically increases the sensitivity to both fatigue-and corrosion-induced damage of their critical structural components during their service lives. Within this scenario, an integrated method that is capable of evaluating the fatigue reliability, identifying a condition-based maintenance, and predicting the remaining service life of its critical components is therefore needed. To accomplish this goal, a procedure for fatigue reliability prediction of PSC highway bridges is proposed in the present study. Vehicle-bridge coupling vibration analysis is performed for obtaining the equivalent moment ranges of critical section of bridges under typical fatigue truck models. Three-dimensional nonlinear mathematical models of fatigue trucks are simplified as an eleven-degree-of-freedom system. Road surface roughness is simulated as zero-mean stationary Gaussian random processes using the trigonometric series method. The time-dependent stress-concentration factors of reinforcing bars and prestressing tendons are accounted for more accurate stress ranges determination. The limit state functions are constructed according to the Miner's linear damage rule, the time-dependent S-N curves of prestressing tendons and the site-specific stress cycle prediction. The effectiveness of the methodology framework is demonstrated to a T-type simple supported multi-girder bridge for fatigue reliability evaluation.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.269-272
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• 2008

The seismic fragility curves of a structure represents the probability of exceeding the prescribed structural damage given various levels of ground motion intensityand the seismic fragility curve is essential to evaluation of structural performance and assessment of risk and loss of structures. The purpose of this paper is to develop seismic fragility functions for bridge structures in Koreaby reviewing those of advanced countries. Therefore, at first, we investigated development conditions of the seismic fragility functions. And the next highway bridges in Korea are classified into a number of categories and several typical bridges are selected to estimate seismic fragilities for using this analysis method in Korea. Finally, fragility curves for PSC Box girder bridge are estimated. The results show that the bridge classification and damage state play an important role in estimation of seismic damage and seismic fragility analysis for bridge structures.

• BMB Reports
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• v.46 no.2
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• pp.113-118
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• 2013

TTRAP is a multi-functional protein that is involved in multiple aspects of cellular functions including cell proliferation, apoptosis and the repair of DNA damage. Here, we demonstrated that the lentivirus-mediated overexpression of TTRAP significantly inhibited cell growth and induced apoptosis in osteosarcoma cells. The ectopic TTRAP suppressed the growth and colony formation capacity of two osteosarcoma cell lines, U2OS and Saos-2. Cell apoptosis was induced in U2OS cells and the cell cycle was arrested at G2/M phase in Saos-2 cells. Exogenous expression of TTRAP in serum-starved U2OS and Saos-2 cells induced an increase in caspase-3/-7 activity and a decrease in cyclin B1 expression. In comparison with wild-type TTRAP, mutations in the 5'-tyrosyl-DNA phosphodiesterase activity of TTRAP, in particular $TTRAP^{E152A}$, showed decreased inhibitory activity on cell growth. These results may aid in clarifying the physiological functions of TTRAP, especially its roles in the regulation of cell growth and tumorigenesis.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.815-829
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• 2008

Debris flows are a natural hazard which looks like a combination of flood, land and rock slide. Large rainfall in July 2006 produced several large scale debris flows and many small debris flows that resulted in loss of life and considerable property and railway damage, as was widely reported in the national media. The hazard "debris flow" is still insufficiently researched. Furthermore debris flows are very hard to predict. Flexible Ring net barriers are multi-functional mitigation devices commonly applied to rock fall or floating wood protection in floods, snow avalanches and also mud flows or granular debris flows, if properly dimensioned for the process or processes for which they are intended. Overtopping of the barriers by debris flows and sediment transport is possible, supporting the design concept that a series of barriers may be used to stop volumes of debris larger than are possible using only one barrier. The future for these barrier concepts looks promising because these barriers represent the state of art for such applications and are superior to many other available options.

• Wind and Structures
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• v.31 no.3
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• pp.217-227
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• 2020

Based on translation models, both Gaussian and non-Gaussian wind fields are generated using spectral representation method for investigating the influence of non-Gaussian characteristics and directivity effect of wind load on fatigue damage of wind turbine. Using the blade aerodynamic model and multi-body dynamics, dynamic responses are calculated. Using linear damage accumulation theory and linear crack propagation theory, crack initiation life and crack propagation life are discussed with consideration of the joint probability density distribution of the wind direction and mean wind speed in detail. The result shows that non-Gaussian characteristics of wind load have less influence on fatigue life of wind turbine in the area with smaller annual mean wind speeds. Whereas, the influence becomes significant with the increase of the annual mean wind speed. When the annual mean wind speeds are 7 m/s and 9 m/s at hub height of 90 m, the crack initiation lives under softening non-Gaussian wind decrease by 10% compared with Gaussian wind fields or at higher hub height. The study indicates that the consideration of the influence of softening non-Gaussian characteristics of wind inflows can significantly decrease the fatigue life, and, if neglected, it can result in non-conservative fatigue life estimates for the areas with higher annual mean wind speeds.

• Smart Structures and Systems
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• v.14 no.4
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• pp.679-697
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• 2014

The strain data acquired from structural health monitoring (SHM) systems play an important role in the state monitoring and damage identification of bridges. Due to the environmental complexity of civil structures, a better understanding of the actual strain data will help filling the gap between theoretical/laboratorial results and practical application. In the study, the multi-scale features of strain response are first revealed after abundant investigations on the actual data from two typical long-span bridges. Results show that, strain types at the three typical temporal scales of $10^5$, $10^2$ and $10^0$ sec are caused by temperature change, trains and heavy trucks, and have their respective cut-off frequency in the order of $10^{-2}$, $10^{-1}$ and $10^0$ Hz. Multi-resolution analysis and wavelet shrinkage are applied for separating and extracting these strain types. During the above process, two methods for determining thresholds are introduced. The excellent ability of wavelet transform on simultaneously time-frequency analysis leads to an effective information extraction. After extraction, the strain data will be compressed at an attractive ratio. This research may contribute to a further understanding of actual strain data of long-span bridges; also, the proposed extracting methodology is applicable on actual SHM systems.

• Advances in nano research
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• v.12 no.6
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• pp.583-592
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• 2022

In this paper, a pulsed picosecond laser dressing method for bronze-bonded diamond wheel is studied systematically and comprehensively. The picosecond laser pulse ablation experiment is carried out, and the ablation thresholds of bronze-bonded and diamond abrasive particle are measured respectively. The results indicate that the single-pulse ablation thresholds of bronze-bonded are 0.89J/cm², 0.24J/cm² during strong/weak ablation stages. And the multi-pulse ablation thresholds of diamond abrasive particle are 1.69J/cm², 0.49J/cm² during strong/weak ablation stages. Obviously, diamond grains have less thermal damage during the process of gentle ablation. The diamond grains of the grinding wheel surface are graphitized during laser dressing. The bronze-bonded is relatively smooth and organizational stability, and the diamond grits have suitable prominent height, which are beneficial to maintain the good grinding performance of dressed bronze-bonded diamond grinding wheels.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.33 no.12
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• pp.105-112
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• 2017

Through various media, damage of both smoking and second-hand smoking has been recognized, and brought global scale of interest in antismoking. In Korea, government has tightened regulations of smoking in non-smoking zone since December, 1980, and after National Health Promotion Act in 1995, non-smoking zone has been gradually expanded. On the other hand, there were law suits to find those regulation towards smokers are either unconstitutional or not for 4 times. In this current state, people need smoking area to prevent second-hand smoking and to consider smokers in multi-unit dwelling. Main purpose of this research is to plan smoking spaces based on various typology of multi-dwelling plan for protection of both smokers and non-smokers' right. The research group collected and analyzed the smoking behaviors in various multi-unit dwelling types such as flat type, tower type, hybrid type and others. Based on those data, the group found three phenomena. First, there are internal regulations in multi-unit dwelling to make non-smoking zone based on National Health Promotion Act and resident representative meeting decision. Second, main smoking activities are occurring at major traffic line and entrances. Third, smoking inside of multi-unit dwelling complex causes second-hand smoking to residents live in $1^{st}$ floor and when they enter. Therefore, one can achieve both smokers' and non-smokers' protection of right by creating a designated smoking space near main entrances of multi-unit dwelling complex to consider smokers' and prevents second-hand smoking by using shaft space, which is in core space, to ventilate tobacco smoke through roof.

• Journal of Conservation Science
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• v.34 no.6
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• pp.503-515
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• 2018

Stupa of State Preceptor Jigwang at Beopcheonsa temple site, Wonju, was conserved and restored in 1957. It was necessary to assess the degree of damage to the used mortar and to provide objective data on the necessity of its removal. Therefore, the HCP(half-cell potential) measurement used in concrete fields was applied. Multi-regression analysis of HCP data, following the rapid corrosion test of the roofstone mortar used by the rebar, resulted in a high correlation of HCP values(0.86), depending on the amount of corrosion and cover depth used for the steel bar. As a result, high correlation values(0.86) for the coefficients of determination were derived. The showed that the measurement of the wet conditions -431 to -663 mV on the roofstone indicated a corrosion damage rate of 90% or more after removal and restoration.

• Steel and Composite Structures
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• v.26 no.6
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• pp.745-757
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• 2018

The inclusion of a ductile steel bracing as means of repairing an earthquake-damaged bridge bent is evaluated and experimentally assessed for the purposes of restoring the damaged bent's strength and stiffness and further improving the energy dissipation capacity. The study is focused on substandard reinforced concrete multi-column bridge bents constructed in the 1950 to mid-1970 in the United States. These types of bents have numerous deficiencies making them susceptible to seismic damage. Large-scale experiments were used on a two-column reinforced concrete bent to impose considerable damage of the bent through increasing amplitude cyclic deformations. The damaged bent was then repaired by installing a ductile fuse steel brace in the form of a buckling-restrained brace in a diagonal configuration between the columns and using post-tensioned rods to strengthen the cap beam. The brace was secured to the bent using steel gusset plate brackets and post-installed adhesive anchors. The repaired bent was then subjected to increasing amplitude cyclic deformations to reassess the bent performance. A subassemblage test of a nominally identical steel brace was also conducted in an effort to quantify and isolate the ductile fuse behavior. The experimental data from these large-scale experiments were analyzed in terms of the hysteretic response, observed damage, internal member loads, as well as the overall stiffness and energy dissipation characteristics. The results of this study demonstrated the effectiveness of utilizing ductile steel bracing for restoring the bent and preventing further damage to the columns and cap beams while also improving the stiffness and energy dissipation characteristics.