• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2023.11a
• /
• pp.277-278
• /
• 2023

In 2022, construction had a five fold higher accident and fatality rate compared to the overall industry. The Construction Technology Promotion Act requires parties in construction contracts to calculate safety costs following Ministry of Land, Infrastructure and Transport guidelines. Understanding safety expense components is vital for evaluating accident prevention costs and planning anti-accident strategies. A study surveyed safety professionals to analyze the importance and influence of safety management expense components, providing basic data for future research. Survey results highlighted the significance of safety management plans, structural safety assurance, and preventing collateral damage.

• Journal of the Korea Convergence Society
• /
• v.11 no.6
• /
• pp.191-196
• /
• 2020

In this study, the durability was analyzed as the models with three shapes depending on the length of the landing gear. Overall, the upper part of the landing gear produced a greater amount of deformation, but the equivalent stress was shown to be high in the upper part just above the lower part. Model 3 shows that the maximum equivalent stress is more than 4 times and the maximum total deformation is more than 24 times compared to model 2. Model 3 showed that the damage could occur beyond the yield stress at the lower end. Model 2 with the upper part longer than the lower part showed the lowest equivalent stress and total deformation among the three models. Therefore, from a structural standpoint, it was shown that model 2 was the most durable at landing and model 3 was the most degraded in terms of durability. The design and analysis results of this study can be effectively applied at grasping the structural durability of landing gear. By applying the structural durability analysis of landing gear, this paper is seen as the convergence study that conforms to aesthetic design.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.11
• /
• pp.501-509
• /
• 2019

The construction of foundation piles for buildings and bridges is changing from pile driving to an injected precast pile method. The goal is to minimize environmental damage, noise pollution, and complaints from neighboring residents. However, it is necessary to develop economic piles that are optimized for precasting by a centrifugal method in terms of both the material and structural system. A reinforced joint method is proposed for reinforced concrete piles (RC piles) manufactured by centrifugal casting. A previous study concluded that the structural performance of the current joint system for RC piles could be improved by using a reinforced joint composed of extended circular band plates and studs. In this study, the structural performance of such a joint was validated experimentally by bending and shear strength measurements. The proposed joint reinforcement method showed adequate structural performance in terms of bending and shear strength. The overall load-deflection behavior is close to that of a structure without joints, so it is expected that the behavior and performance of the design can be reliably reflected in site structures.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.3
• /
• pp.167-174
• /
• 2008

The objective of this study is to verify whether the composite action is sufficiently strong to withstand at the interface and the structural behavior of LB-DECK panel with field concrete slab strengthened with main reinforcing bars. Static and fatigue tests are performed for LB-DECK panels with varied shapes and amounts of rebars, and the results are compared with those of field concrete panel(FCP). The test results indicate that the LB-DECK panel with 1.5 times of more rebars inside significantly increase the overall stiffness. LB-DECK penel usually shows on average 52.1 percent of improved stiffness compared with the FCP. The fatigue test results also show that the LB-DECK panel can withstand two-million cycles of repeated loads without any damage.

• Earthquakes and Structures
• /
• v.5 no.6
• /
• pp.657-678
• /
• 2013

For economical earthquake resistant design of cable-stayed bridge tower, the use of energy dissipation systems for the earthquake protection of steel structures represents an alternative seismic design method where the tower structure could be constructed to dissipate a large amount of earthquake input energy through inelastic deformations in certain positions, which could be easily retrofitted after damage. The design of energy dissipation systems for bridges could be achieved as the result of two conflicting requirements: no damage under serviceability limit state load condition and maximum dissipation under ultimate limit state load condition. A new concept for cable-stayed bridge tower seismic design that incorporates sacrificial link scheme of low yield point steel horizontal beam is introduced to enable the tower frame structure to remain elastic under large seismic excitation. A nonlinear dynamic analysis for the tower model with the proposed energy dissipation systems is carried out and compared to the response obtained for the tower with its original configuration. The improvement in seismic performance of the tower with supplemental passive energy dissipation system has been measured in terms of the reduction achieved in different response quantities. Obtained results show that the proposed energy dissipation system of low yield point steel seismic link could strongly enhance the seismic performance of the tower structure where the tower and the overall bridge demands are significantly reduced. Low yield point steel seismic link effectively reduces the damage of main structural members under earthquake loading as seismic link yield level decreases due their exceptional behavior as well as its ability to undergo early plastic deformations achieving the concentration of inelastic deformation at tower horizontal beam.

• Structural Engineering and Mechanics
• /
• v.87 no.2
• /
• pp.137-149
• /
• 2023

In this study, to explore the working performance of the CFST split spherical node wind power tower, two groups of CFST split spherical joint plane towers with different web wall thicknesses and a set of space systems were analyzed. The tower was subjected to a low-cycle repeated load test, and the hysteresis and skeleton curves were analyzed. ABAQUS finite element simulation was used for verification and comparison, and on this basis parameter expansion analysis was carried out. The results show that the failure mode of the wind power tower was divided into weld tear damage between belly bar, high strength bolt thread damage and belly rod flexion damage. In addition, increasing the wall thickness of the web member could render the hysteresis curve fuller. Finally, the bearing capacity of the separated spherical node wind power tower was high, but its plastic deformation ability was poor. The ultimate bearing capacity and ductility coefficient of the simulated specimens are positively correlated with web diameter ratio and web column stiffness ratio. When the diameter ratio of the web member was greater than 0.13, or the stiffness ratio γ of the web member to the column was greater than 0.022, the increase of the ultimate bearing capacity and ductility coefficient decreased significantly. In order to maximize the overall mechanical performance of the tower and improve its economy, it was suggested that the diameter ratio of the ventral rod be 0.11-0.13, while the stiffness ratio γ should be 0.02-0.022.

• Journal of Conservation Science
• /
• v.25 no.2
• /
• pp.115-130
• /
• 2009

This study was focused on digital restoration and structural stability evaluation applying 3D scanning system of five-storied Magoksa temple stone pagoda in Gongju. For these, the digital restoration of the pagoda was completed using laser scan data which is measured 16 directions and data processing program of 7 stages. As a result of digital restoration, the overall height and width of stone properties showed a little difference in directions and the width of roof stones appeared very high difference of each floor. The width of pagoda body become smaller to the fifth floor, but gradual decrease rate showed irregular characteristics. Also, as result of 3D image analysis for structural stability evaluation, the displacement occurred toward northwest in second body stone to upper final stone except for central axis of the first body stone which inclines toward southwest. Such 3D image analysis is required quantification of survey method and should be applied to various field such as quantitative damage maps in order to utilize a conservation of stone cultural heritages, continuously.

• Smart Structures and Systems
• /
• v.29 no.1
• /
• pp.181-193
• /
• 2022

Data-driven structural health monitoring (SHM) of civil infrastructure can be used to continuously assess the state of a structure, allowing preemptive safety measures to be carried out. Long-term monitoring of large-scale civil infrastructure often involves data-collection using a network of numerous sensors of various types. Malfunctioning sensors in the network are common, which can disrupt the condition assessment and even lead to false-negative indications of damage. The overwhelming size of the data collected renders manual approaches to ensure data quality intractable. The task of detecting and classifying an anomaly in the raw data is non-trivial. We propose an approach to automate this task, improving upon the previously developed technique of image-based pre-processing on one-dimensional (1D) data by enriching the features of the neural network input data with multiple channels. In particular, feature engineering is employed to convert the measured time histories into a 3-channel image comprised of (i) the time history, (ii) the spectrogram, and (iii) the probability density function representation of the signal. To demonstrate this approach, a CNN model is designed and trained on a dataset consisting of acceleration records of sensors installed on a long-span bridge, with the goal of fault detection and classification. The effect of imbalance in anomaly patterns observed is studied to better account for unseen test cases. The proposed framework achieves high overall accuracy and recall even when tested on an unseen dataset that is much larger than the samples used for training, offering a viable solution for implementation on full-scale structures where limited labeled-training data is available.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.11
• /
• pp.725-730
• /
• 2017

The strength ratio of the main structures of buildings gradually increasing, due to the advances made in analysis and cost saving techniques. In this study, to examine the stability of industry buildings using sandwich panels as roof assemblies, we examine the changes in the moment strength ratio of the main structures caused by increasing the roof load. This study adopts the PEB structure and three H-steel structure as the structural analysis models. In the case where the additional load exceeds about 11% of the roof design load, the strength ratio exceeds 1 for the main structure. In the case where the additional load exceeds about 36%(of the roof design load), the working moment exceeds the plastic moments, which leads to major damage to the structure. This study compares 1) the maximum load according to the purlin spaces, 2) the maximum load by KS, and 3) the maximum load calculated from the test results of the manufacturer.The maximum bearing load of the panels determined by all three methods exceeds the structure failure threshold load of the main structure. This study provides evidence that an unexpected increase in the roof load might cause the whole structure to collapse, due to the failure of the main structural members, before the failure of the roof assemblies. Therefore, information on the structural performance of the sandwich panels is required for the structural design, and the sandwich panels should be considered to be an integral part of the overall structural design.

• Clinical and Experimental Pediatrics
• /
• v.63 no.4
• /
• pp.135-140
• /
• 2020

Background: Breastfeeding reportedly reduces the overall frequency of infections. Respiratory syncytial virus (RSV), the most common respiratory pathogen in infants, involves recurrent wheezing and has a pathogenic mechanism related to airway structural damage. Purpose: This study aimed to investigate whether breastfeeding has a beneficial effect against RSV-induced respiratory infection compared to formula feeding among infants in Korea. Methods: We retrospectively reviewed the medical records of infants under 1 year of age who were admitted with RSV infection between January 2016 and February 2018 at the department of pediatrics of 4 hospitals. We investigated the differences in clinical parameters such as cyanosis, chest retraction, combined infection, fever duration, oxygen use, oxygen therapy duration, intensive care unit (ICU) admission, and corticosteroid treatment of exclusive breast milk feeding (BMF), artificial milk formula fed (AMF), and mixed feeding (MF) groups. Results: Among the 411 infants included in our study, 94, 161, and 156 were included in the BMF, MF, and AMF groups, respectively. The rates of oxygen therapy were significantly different among the BMF (4.3%), MF (8.1%), and AMF (13.5 %) groups (P=0.042). The odds ratios (ORs) for oxygen therapy was significantly higher in the AMF group than in the BMF group (adjusted OR, 3.807; 95% confidence interval, 1.22-11.90; P=0.021). The ICU admission rate of the BMF group (1.1%) was lower than that of the MF (3.5%) and AMF (4.5%) groups; however, the dissimilarity was not statistically significant (P=0.338). Conclusion: The severity of RSV infection requiring oxygen therapy was lower in the BMF than the AMF group. This protective role of human milk on RSV infection might decrease the need for oxygen therapy suggesting less airway damage.