• Structural Engineering and Mechanics
• /
• v.76 no.6
• /
• pp.751-763
• /
• 2020

Available records of recent earthquakes show that near-field earthquakes have different characteristics than far-field earthquakes. In general, most of these unique characteristics of near-fault records can be attributed to their forward directivity. This phenomenon causes the records of ground motion normal to the fault to entail pulses with long periods in the velocity time history. The energy of the earthquake is almost accumulated in these pulses causing large displacements and, accordingly, severe damages in the building. Damage to structures caused by past earthquakes raises the need to assess the chance of future earthquake damage. There are a variety of methods to evaluate building seismic vulnerabilities with different computational cost and accuracy. In the meantime, fragility curves, which defines the possibility of structural damage as a function of ground motion characteristics and design parameters, are more common. These curves express the percentage of probability that the structural response will exceed the allowable performance limit at different seismic intensities. This study aims to obtain the fragility curve for low- and mid-rise structures of reinforced concrete moment frames by incremental dynamic analysis (IDA). These frames were exposed to an ensemble of 18 ground motions (nine records near-faults and nine records far-faults). Finally, after the analysis, their fragility curves are obtained using the limit states provided by HAZUS-MH 2.1. The result shows the near-fault earthquakes can drastically influence the fragility curves of the 6-story building while it has a minimal impact on those of the 3-story building.

• The Journal of Information Systems
• /
• v.30 no.2
• /
• pp.29-56
• /
• 2021

Purpose Cyber deviance of adolescents has become a serious social problem. With a widespread use of smartphones, incidents of cyber deviance have increased in Korea and both quantitative and qualitative damages such as suicide and depression are increasing. Research has been conducted to understand diverse factors that explain adolescents' delinquency in cyber space. However, most previous studies have focused on a single theory or perspective. Therefore, this study aims to comprehensively analyze motivations of juvenile cyber deviance and to develop a predictive model for delinquent adolescents by integrating four different theories on cyber deviance. Design/methodology/approach By using data from Korean Children & Youth Panel Survey 2010, this study extracts 27 potential factors for cyber deivance based on four background theories including general strain, social learning, social bonding, and routine activity theories. Then this study employs econometric analysis to empirically assess the impact of potential factors and utilizes a machine learning approach to predict the likelihood of cyber deviance by adolescents. Findings This study found that general strain factors as well as social learning factors have positive effects on cyber deviance. Routine activity-related factors such as real-life delinquent behaviors and online activities also positively influence the likelihood of cyber diviance. On the other hand, social bonding factors such as community commitment and attachment to community lessen the likelihood of cyber deviance while social factors related to school activities are found to have positive impacts on cyber deviance. This study also found a predictive model using a deep learning algorithm indicates the highest prediction performance. This study contributes to the prevention of cyber deviance of teenagers in practice by understanding motivations for adolescents' delinquency and predicting potential cyber deviants.

• Earthquakes and Structures
• /
• v.20 no.3
• /
• pp.295-307
• /
• 2021

The gap provided between adjacent structures in the metropolitan cities is mostly narrow due to architectural and financial issues. Consequently, structural pounding occurs between adjacent structures during earthquakes. It causes damages, ranging from minor local to more severe ones, especially in the case of seismically isolated buildings, due to their higher displacements. However, due to the increased flexibility of isolated buildings, the problem could become more detrimental to such structures. The effect of the seismic pounding of moat walls on the response of buildings isolated by Triple Friction Pendulum Bearing (TFPB) is investigated in this paper. To this propose, two symmetric three-dimensional models, including single-story and five-story buildings, are modeled in Opensees. Nonlinear Time History Analyses (NTHA) are performed for seismic evaluation. Also, five different sizes with four different sets of friction coefficients are considered for base isolators to cover a whole range of base isolation systems with various geometry configurations and fundamental period. The results are investigated in terms of base shear, buildings' drift, and roof acceleration. Results indicated a profound effect of poundings against moat walls. In situations of potential pounding, in some cases, the influence of impact on seismic responses of multistory buildings was more remarkable.

• Journal of Environmental Health Sciences
• /
• v.47 no.4
• /
• pp.310-319
• /
• 2021

Background: Humidifier disinfectant exposure is an ongoing issue, and there is still considerable related controversy. Various approaches are needed to secure scientific evidence on the extent of the victims' damages and for the determination of appropriate compensation. Objectives: The purpose of this study was to assess the association between humidifier disinfectant (HD) use and academic achievement in Korean children. Methods: This study used data from the 8th Panel Study on Korean Children in 2015. For the final study, 1,598 cases were used. T-tests and multiple linear regression analyses were conducted to determine whether the use of humidifier disinfectant is a factor that affects academic ability. Results: Children in groups using humidifier disinfectant showed statistically significantly lower scores in all areas of language, including reading, speaking and writing, and statistically lower scores in all areas of mathematics, including counting, addition and subtraction. In the multiple regression analysis results, which control for the effects of various demographic/social variables, the use of humidifier disinfectants showed statistically significant beta coefficients (β: -0.357, p<0.001), negatively affecting children's language ability. As for the 'math' variable, which was created by combining counting, addition, and subtraction scores, the use of humidifier disinfectants as independent variables also showed statistically significant beta coefficients (β: -0.200, p<0.001), negatively affecting children's math ability. Conclusions: The results of the study showed that depending on whether or not humidifier disinfectants were used, there are differences in children's language abilities, such as reading, speaking, and writing, as well as in their mathematical abilities, such as counting, adding, and subtracting numbers. These findings are thought to serve as a scientific basis for extending the perspective from health effects to more diverse areas of demographic and social impact related to humidifier disinfectant damage and compensation.

• Journal of the Korean GEO-environmental Society
• /
• v.24 no.1
• /
• pp.25-36
• /
• 2023

In Korea, the rockfall prevention fence is designed with 50kJ of rockfall kinetic energy in order to prevent damages such as falling rocks and landslides. In the case of rockfall kinetic energy, it is highly dependent on the shape of the slope on which it occurs. As a previous study, a fence performance evaluation was conducted for 100kJ rockfall impact energy using ETAG 27. However, previous studies have focused on newly installed rockfall prevention fences. In this study, a reinforcing materials was installed on the existing rockfall prevention fence through numerical analysis, and the structural performance of the high-strength rockfall prevention fence capable of defending against 120kJ of rockfall kinetic energy was evaluated.

• Geomechanics and Engineering
• /
• v.34 no.3
• /
• pp.251-265
• /
• 2023

In urban construction projects, it is crucial to evaluate the impacts of excavation-induced ground movements in order to protect surrounding structures. These ground movements resulting in damages to the neighboring structures and facilities (i.e., parking basement) are of main concern for the geotechnical engineers. Even more, the danger exists if the nearby structure is an ancient or masonry brick building. The formations of cracks are indicators of structural damage caused by excavation-induced ground disturbances, which pose issues for excavation-related projects. Although the effects of deep excavations on existing brick masonry walls have been thoroughly researched, the impact of twin excavations on a brick masonry wall is rarely described in the literature. This work presents a 3D parametric analysis using an advanced hypoplastic model to investigate the responses of an existing isolated brick masonry wall to twin perpendicular excavations in dry sand. One after the other, twin perpendicular excavations are simulated. This article also looks at how varying sand relative densities (D_r = 30%, 50%, 70%, and 90%) affect the masonry wall. The cracks at the top of the wall were caused by the hogging deformation profile caused by the twin excavations. By raising the relative density from 30% to 90%, excavation-induced footing settlement is greatly minimized. The crack width at the top of the wall reduces as a result of the second excavation in very loose to loose sand (D_r = 30% and 50%). While the crack width on the top of the wall increases owing to the second excavation in medium to very dense sand (D_r = 70% and 90%).

• Smart Structures and Systems
• /
• v.32 no.3
• /
• pp.153-166
• /
• 2023

Health monitoring of civil infrastructures, in particular, old bridges that are still in service, has become more than necessary, given the risk that a possible degradation or failure of these infrastructures can induce on the safety of users in addition to the resulting commercial and economic impact. Bridge integrity assessment has attracted significant research efforts over the past forty years with the aim of developing new damage identification methods applicable to real structures. The bridge of Ouled Mimoun (Tlemcen, Algeria) is one of the oldest railway structure in the country. It was built in 1889. This bridge, which is too low with respect to the level of the road, has suffered multiple shocks from various machines that caused considerable damage to its central part. The present work aims to analyze the stability of this bridge by identifying damages and evaluating the damage rate in different parts of the structure on the basis of a finite element model. The applied method is based on an inverse analysis of the normal stress responses that were calculated from the corresponding recorded strains, during the passage of a real train, by means of a set of strain gauges placed on certain elements of the bridge. The results obtained from the inverse analysis made it possible to successfully locate areas that were really damaged and to estimate the damage rate. These results were also used to detect an excessive rigidity in certain elements due to the presence of plates, which were neglected in the numerical reference model. In the case of the continuous bridge monitoring, this developed method will be a very powerful tool as a smart health monitoring system, allowing engineers to take in time decisions in the event of bridge damage.

• International conference on construction engineering and project management
• /
• 2024.07a
• /
• pp.1177-1186
• /
• 2024

The construction sector, in relation to human's residential issues, serves as the cornerstone of societal systems, economic security, the national economy, individuals and households, economic activity, national safety, management, business, and government. Also, the essential sectors, such as electric power generation, transmission, and distribution, and natural gas distribution, water, sewage, and stormwater systems, and so on, form the heart of our social system. These essential sectors of our society provide core goods and services for continuous public health services, construction services, government operations, multiple businesses, and national and economic safety. Therefore, those systems are the cornerstone of our society, and strengthening their security and resilience is of utmost significance. However, the existing framework for assessing and evaluating the problems with regard to those systems lacks efficient methods and mechanisms. The main objective of this research is to define correlations between different infrastructures within an economic system to strengthen the resilience and security of the construction sector. This study will be conducted to identify physical relationships between different industries within an economic system and to define deterministic relationships through the values of interconnectedness and interdependency. In addition, this research attempts to complete a probabilistic estimation of economic impacts using historical economic data and to develop an assessment model that can be used in the future to measure economic impact in terms of the construction sector. In case of loss in the construction sector due to exogenous factors, identifying which critical infrastructures or sectors will be the most affected will help minimize the risks and property damages. Furthermore, improving the resiliency of the construction sector will help speed recovery from or resistance to unpredictable external elements.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.9 no.4
• /
• pp.71-80
• /
• 2009

Although desire for living without hazardous damages grows these days, threats from natural disasters which we are currently exposed to are quiet different from what we have experienced. To cope with this changing situation, it is necessary to assess the characteristics of the natural disasters. Therefore, the main purpose of this research is to suggest a methodology to estimate the potential property loss and assess the flood risk using a regional regression analysis. Since the flood damage mainly consists of loss of lives and property damages, it is reasonable to express the results of a flood risk assessment with the loss of lives and the property damages that are vulnerable to flood. The regional regression analysis has been commonly used to find relationships between regional characteristics of a watershed and parameters of rainfall-runoff models or probability distribution models. In our research, however, this model is applied to estimate the potential flood damage as follows; 1) a nonlinear model between the flood damage and the hourly rainfall is found in gauged regions which have sufficient damage and rainfall data, and 2) a regression model is developed from the relationship between the coefficients of the nonlinear models and socio-economic indicators in the gauged regions. This method enables us to quantitatively analyze the impact of the regional indicators on the flood damage and to estimate the damage through the application of the regional regression model to ungauged regions which do not have sufficient data. Moreover the flood risk map is developed by Flood Vulnerability Index (FVI) which is equal to the ratio of the estimated flood damage to the total regional property. Comparing the results of this research with Potential Flood Damage (PFD) reported in the Long-term Korea National Water Resources Plan, the exports' mistaken opinions could affect the weighting procedure of PFD, but the proposed approach based on the regional regression would overcome the drawback of PFD. It was found that FVI is highly correlated with the past damage, while PFD does not reflect the regional vulnerabilities.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.5A
• /
• pp.565-575
• /
• 2009

In recent years, there have been numerous explosion-related accidents due to military and terrorist activities. Such incidents caused not only damages to structures but also human casualties, especially in urban areas. To protect structures and save human lives against explosion accidents, better understanding of the explosion effect on structures is needed. In an explosion, the blast load is applied to concrete structures as an impulsive load of extremely short duration with very high pressure and heat. Generally, concrete is known to have a relatively high blast resistance compared to other construction materials. However, normal strength concrete structures require higher strength to improve their resistance against impact and blast loads. Therefore, a new material with high-energy absorption capacity and high resistance to damage is needed for blast resistance design. Recently, Ultra High Strength Concrete(UHSC) and Reactive Powder Concrete(RPC) have been actively developed to significantly improve concrete strength. UHSC and RPC, can improve concrete strength, reduce member size and weight, and improve workability. High strength concrete are used to improve earthquake resistance and increase height and bridge span. Also, UHSC and RPC, can be implemented for blast resistance design of infrastructure susceptible to terror or impact such as 9.11 terror attack. Therefore, in this study, the blast tests are performed to investigate the behavior of UHSC and RPC slabs under blast loading. Blast wave characteristics including incident and reflected pressures as well as maximum and residual displacements and strains in steel and concrete surface are measured. Also, blast damages and failure modes were recorded for each specimen. From these tests, UHSC and RPC have shown to better blast explosions resistance compare to normal strength concrete.